Using the IR2110 Low and High Level Key Driver - Explanation and Circuit Examples. Power MOSFET Driver for Low Voltage Circuits
Power MOSFETs and insulated gate bipolar transistors (IGBTs) are the basic elements of modern power electronics and are used as switching elements for high currents and voltages. However, to match low-voltage logical control signals with the gate control levels of MOSFET and IGBT transistors, intermediate matching devices are required - high-voltage drivers (hereinafter, for brevity, by “high-voltage drivers” we will mean “high-voltage drivers of MOSFET and IGBT transistors”).
In most cases, the following classification of high-voltage drivers is used:
- Independent drivers of the upper and lower arms of the half-bridge, integrated in one chip ( High and Low Side Driver);
- Upper and lower leg drivers connected in a half-bridge circuit ( Half-Bridge Driver);
- Upper arm drivers ( High Side Driver);
- Low arm drivers ( Low Side Driver).
In Fig. Figure 1 shows the control circuits corresponding to these types of drivers.
Rice. 1.
In the first case (Fig. 1a), two independent loads are controlled from single control signals. The loads, accordingly, are connected between the source of the lower transistor and the high-voltage power bus (low-side driver), as well as between the drain of the upper transistor and ground (high-side driver). The so-called midpoints (drain of the upper transistor and source of the lower transistor) are not connected to each other.
In the second case (Fig. 1b), the midpoints are connected. Moreover, the load can be turned on both on the upper and lower shoulders, but connected to the middle point in the same way as a half-bridge circuit (the so-called full bridge circuit). Strictly speaking, in scheme 1a, nothing prevents you from connecting the middle points. But in this case, with a certain combination of input signals, it is possible for two transistors to open simultaneously and, accordingly, an excessively large current to flow from the high-voltage bus to the ground, which will lead to failure of one or both transistors at once. Eliminating such a situation in this scheme is the concern of the developer. In half-bridge drivers (circuit 1b), this situation is eliminated at the level of the internal control logic of the microcircuit.
In the third case (1c), the load is connected between the drain of the upper transistor and the ground, and in the fourth (1d) - between the source of the lower transistor and the high-voltage power bus, i.e. Two “halves” of circuit 1a are implemented separately.
In recent years, STMicroelectronics has focused (in the niche of high-voltage drivers) only on drivers of the first two types (families L638x And L639x, which will be discussed below). However, earlier designs contain driver chips that control turning on or off a single MOSFET or IGBT transistor (the “Single” category in STMicroelectronics terms). With a certain switching circuit, these drivers can control the load of both the upper and lower arms. Let's also note the microcircuit TD310— three independent single drivers in one housing. This solution will be effective when controlling a three-phase load. STMicroelectronics classifies this chip as a “Multiple” category driver.
L368x
Table 1 shows the composition and parameters of the L368x family of microcircuits. ICs in this family include both independent high- and low-side (H&L) drivers and half-bridge (HB) drivers.
Table 1. L638x family driver parameters
| Name | Voffcet, V | Io+, mA | Io-, mA | Ton, ns | Toff, ns | Tdt, ns | Type | Control |
|---|---|---|---|---|---|---|---|---|
| L6384E | 600 | 400 | 650 | 200 | 250 | Prog. | HB | IN/-SD |
| L6385E | 600 | 400 | 650 | 110 | 105 | H&L | HIN/LIN | |
| L6386E | 600 | 400 | 650 | 110 | 150 | H&L | HIN/LIN/-SD | |
| L6387E | 600 | 400 | 650 | 110 | 105 | H&L | HIN/LIN | |
| L6388E | 600 | 200 | 350 | 750 | 250 | 320 | HB | HIN/LIN |
Let's explain some parameters:
V OFFSET - the maximum possible voltage between the source of the upper transistor and ground;
I O+ (I O-) - maximum output current when the upper (lower) transistor of the output stage of the microcircuit is open;
T ON (T OFF) — signal propagation delay from inputs HIN and LIN to outputs HO and LO when turned on (off);
T DT - pause time - a parameter related to half-bridge drivers. When changing active states, the logic circuit forcibly introduces pauses to avoid turning on the upper and lower arms simultaneously. For example, if the lower arm is turned off, then both arms are turned off for some time and only then the upper one turns on. And, conversely, if the upper arm is turned off, then both arms are turned off for some time and then the lower one turns on. This time can either be fixed (as in L6388E), or set by selecting the value of the corresponding external resistor (as in L6384E).
Control. ICs of independent drivers of the upper and lower shoulders are controlled via the HIN and LIN inputs. Moreover, the high level of the logical signal turns on, respectively, the upper or lower arm of the driver. In addition, the L6386E chip uses an additional SD input, which turns off both arms regardless of the state at the HIN and LIN inputs.
The L6384E chip uses SD and IN signals. The SD signal turns off both legs regardless of the state at the IN input. The signal IN = 1 is equivalent to the signal combination (HIN = 1, LIN = 0) and, conversely, IN = 0 is equivalent to the signal combination (HIN = 0, LIN = 1). Thus, simultaneous switching on of the upper and lower side transistors is impossible in principle.
In the L6388E chip, control is carried out via the HIN and LIN inputs, so it is in principle possible to apply a combination (HIN = 1, LIN = 1) to the inputs, but the internal logic circuit converts it into a combination (HIN = 0, LIN = 0), thus eliminating , simultaneous switching on of both transistors.
As for the parameters, let's start with H&L type chips.
The value V OFFSET equal to 600 Volts is, in a sense, a standard for microcircuits of this class.
The output current I O+ (I O-), equal to 400/650 mA, is an average indicator, focused on typical general-purpose transistors. Compared to the IRS family of microcircuits (G5 HVIC generation), International Rectifier offers mainly microcircuits with a 290/600 mA parameter. However, the International Rectifier line also includes models with parameters of 2500/2500 mA (IRS2113) and slightly lower speed, or microcircuits with output currents up to 4000/4000 mA (IRS2186). True, in this case the switching time compared to L6385E increases to a value of 170/170 ns.
Switching time. T ON (T OFF) values equal to 110/105 ns (for L6385E) exceed similar values for IRS family microcircuits (albeit not very significantly). International Rectifier achieved the best performance (60/60 ns) in the IRS2011 model, but by reducing the VOFFSET voltage to 200 V.
However, we note that STMicroelectronics offers drivers in which the common wire of the input (low-voltage) and output (high-voltage) stages is the same. International Rectifier, in addition to chips with a similar architecture, offers drivers with separate common buses for the input and output stages.
Comparing the parameters of the L6384E half-bridge driver with International Rectifier products, we can conclude that it is inferior (both in output currents and speed) only to the IRS21834 model, which implements HIN/-LIN input logic. If IN/-SD input logic is critical, the L6384E driver outperforms International Rectifier products.
Let's take a closer look at the L6385E driver chip, the structure and connection diagram of which is shown in Fig. 2.
Rice. 2.
The chip contains two independent drivers of the upper (HVG output) and lower side (LVG output). The implementation of the low-side driver is quite trivial since the potential at the GND pin is constant and hence the task is to convert the low-voltage input logic signal LIN to the voltage level at the LVG output required to turn on the low-side transistor. In the upper side, the potential at the OUT pin changes depending on the state of the lower transistor. There are various circuit solutions used to build a cascade of the upper arm. In this case, a relatively simple and inexpensive bootstrap control circuit is used (circuit with a “floating” power supply). In such a scheme, the duration of the control pulse is limited by the value of the bootstrap capacitance. In addition, it is necessary to provide conditions for its constant charging using a high-voltage, fast-acting level shift cascade. This cascade provides conversion of logic signals to the levels necessary for stable operation of the high-side transistor control circuit.
If the control voltage drops below a certain limit, the output transistors may go into linear mode, which, in turn, will lead to overheating of the crystal. To prevent this, voltage monitoring circuits (UVLO) must be used. Under Voltage LockOut) for both the upper (potential control V BOOT) and the lower (potential control V CC) shoulder.
Modern high-voltage drivers tend to integrate a bootstrap diode into the integrated circuit package. Thanks to this, there is no need to use an external diode, which is quite bulky compared to the driver chip itself. The built-in bootstrap diode (more precisely, a bootstrap circuit) is used not only in the L6385E driver, but also in all other microcircuits of this family.
The L6386E is a variant of the L6385E with additional features. Its structure and connection diagram are shown in Fig. 3.
Rice. 3.
The main differences between the L6386E and the L6385E. Firstly, an additional SD input has been added, a low signal level at which turns off both transistors, regardless of the state of the HIN and LIN inputs. Often used as an emergency shutdown signal, not associated with the input control signal generation circuit. Secondly, a stage has been added to control the current flowing through the lower stage transistor. Comparing with the previous diagram, we see that the drain of the lower-side transistor is connected to ground not directly, but through a current resistor (current sensor). If the voltage drop across it exceeds the threshold value V REF, then a low level is formed at the DIAG output. Note that this state does not affect the operation of the circuit, but is only an indicator.
A few words about the use of L638x family chips. The limited space of the article does not allow us to consider application examples, however, the document “L638xE Application Guide” from STMicroelectronics provides examples of a three-phase motor control circuit, a dimmable fluorescent lamp ballast circuit, DC/DC converters with various architectures, and a number of others. Also shown are diagrams of demonstration boards for all microcircuits of this family (including the topology of printed circuit boards).
To summarize the analysis of the L638x family, we note: without having unique characteristics in any individual parameters, the drivers of this family are among the best in the industry both in terms of the totality of parameters and the technical solutions used.
High Voltage Driver Family
half bridge L639x
At first glance, microcircuits of this family can be considered a development of the L6384E microcircuit. However, when analyzing the functionality of the L639x family drivers, it is very difficult to recognize the L6384E as a prototype (except perhaps due to the absence of other half-bridge drivers in the STMicroelectronics line). Table 2 shows the composition and parameters of the L639x family of microcircuits.
Table 2. L639x family driver parameters
| Name | Voffcet, V | Io+, mA | Io-, mA | Ton, ns | Toff, ns | Tdt, μs | Type | Smart SD | OU | Comp. | Control |
|---|---|---|---|---|---|---|---|---|---|---|---|
| L6390 | 600 | 270 | 430 | 125 | 125 | 0,15…2,7 | HB | There is | There is | There is | HIN/-LIN/-SD |
| L6392 | 600 | 270 | 430 | 125 | 125 | 0,15…2,7 | HB | There is | HIN/-LIN/-SD | ||
| L3693 | 600 | 270 | 430 | 125 | 125 | 0,15…2,7 | HB | There is | PH/-BR/-SD |
The main feature of this family of microcircuits is the presence of additional built-in elements: an operational amplifier or comparator (for L6390 - both). In Fig. Figure 4 shows the structure and circuit diagram of the L6390 chip.
Rice. 4.
What advantages do additional elements provide in practical applications? Operational amplifiers (in L6390 and L6392) are designed to measure the current flowing through the load. Moreover, since both outputs (OP+ and OP-) are available, it becomes possible to generate both an absolute value and a deviation from a certain reference voltage (corresponding, for example, to the maximum permissible value) at the corresponding output of the microcircuit. In the L6390 driver, the comparator performs a very specific function of “smart shutdown” ( Smart Shutdown) - i.e. When the maximum permissible current in the load is exceeded, the comparator begins to influence the logic of the driver and ensures smooth disconnection of the load. The shutdown speed is set by the RC circuit connected to the SD/OD pin. Moreover, since this output is bidirectional, it can be either an error indication output for the control microcontroller or an input for forced shutdown.
All microcircuits contain protection logic against the simultaneous opening of the upper and lower side transistors and, accordingly, the formation of a pause when the output state changes. The pause time T DT for all microcircuits of the family is programmable and is determined by the value of the resistor connected to the DT pin.
Control logic in L6390 and L6392 same type - HIN, LIN and SD signals.
Chip difference L6393 from L6390 and L6392 is not only the absence of an operational amplifier. The comparator in L6393 is independent of the rest of the circuit elements and, in principle, can be used for arbitrary purposes. However, the most reasonable application is to control the current and generate an excess sign (by analogy with the DIAG pin in the L6386E chip discussed above). The main difference is in the control logic - the combination of PHASE, BRAKE and SD control signals is quite rare (if not unique) for microcircuits of this class. The control cyclogram is shown in Fig. 5.
Rice. 5.
The cyclogram is focused on control directly from engine signals, for example, direct current and implements the so-called. delayed stop mechanism. Let's assume that BRAKE is a signal to the actuator, i.e. its low level turns on the motor regardless of the state of the PHASE signal. Again, assume that PHASE is a signal from a feedback sensor, such as a frequency sensor mounted on the motor shaft, or a limit sensor indicating a breakpoint. Then a high level of the BRAKE signal will not stop the engine immediately, but only by a positive edge of the PHASE signal. For example, if we are talking about a carriage drive, then a stop signal (high BRAKE level) can be given in advance, but the stop will occur only at a specific point (when the PHASE sensor is triggered).
In Fig. Figure 6 shows the structure and circuit diagram of the L6393 chip.
Rice. 6.
About the parameters. The I O+ (I O-) output currents of 270/430 mA are inferior to International Rectifier ICs (which, as noted above, typically have 290/600 mA). However, the dynamic parameters T ON /T OFF (125/125 ns) are superior (and often significantly) to all chips in the IRS family.
Conclusions on the L639x family. With sufficiently high quantitative characteristics, which in itself allows us to classify the L639x family as one of the industry leaders, additional functions provide a qualitative leap, since they allow us to implement in one chip those functions that were previously implemented using a number of additional components.
Conclusion
Of course, the range of high-voltage drivers from STMicroelectronics cannot be considered very wide (at least in comparison with similar products from International Rectifier). However, the quantitative and qualitative characteristics of the reviewed families are not inferior to the best IR products.
Speaking about drivers of MOSFET and IGBT transistors, one cannot fail to mention the transistors themselves; STMicroelectronics produces a fairly wide range of field-effect (for example MDMESH V and SuperMesh3) and bipolar transistors with an insulated gate. Since these electronic components were recently covered in this magazine, they are left outside the scope of this article.
And finally, as mentioned above, STMicroelectronics' line of MOSFET and IGBT transistor drivers does not end with half-bridge drivers. The range of drivers of the “Single” and “Multiple” categories and their parameters can be found on the official website of the STMicroelectronics company - http://www.st.com/ .
Literature
1. L638xE Application Guide // ST Microelectronics document an5641.pdf.
2. Yachmennikov V. Increasing efficiency with MDmesh V transistors // Electronics News, No. 14, 2009.
3. Ilyin P., Alimov N. Review of MOSFET and IGBT by STMicroelectronics // Electronics News, No. 2, 2009.
4. Medjahed D. Highly efficient solutions based on SuperMESH3 transistors // Electronics News, No. 16, 2009.
MDMEDH V in PowerFlat housing
STMicroelectronics, a global leader in power MOSFETs, has developed a new PowerFlat package with improved performance, specifically designed for surface mount applications, for the MDMESH V family of transistors. Case dimensions 8x8 mm with a height of 1 mm (PowerFlat 8x8 HV). Its low height allows you to create thinner power supplies, as well as reduce the size of the printed circuit board or increase the density of the installation. The drain contact in the PowerFlat housing is a large exposed metal surface, which improves heat dissipation and therefore improves reliability. This housing is capable of operating in the temperature range -55…150°C.
Transistors of the MDMESH V family are the best transistors in the world in terms of open channel resistance in the operating voltage range of 500...650 V. For example, transistors of the series STW77N65M5 from the MDMESH V family have a maximum Rdson value of 0.033 Ohm and a maximum static current of 69 A for an operating voltage of 650 V. Moreover, the gate charge of such a transistor is only 200 nK. STL21N65M5 — This is the first transistor from the MDMESH V family in a PowerFlat package. At an operating voltage of 650 V, the STL21N65M5 transistor has an open-channel resistance of 0.190 Ohms and a maximum static current of 17 A, while its gate charge is 50 nK.
About ST Microelectronics
Currently, MOSFET and IGBT transistors are mainly used as high- and medium-power power switches. If we consider these transistors as a load for their control circuit, then they are capacitors with a capacity of thousands of picofarads. To open the transistor, this capacity must be charged, and when closing, it must be discharged, and as quickly as possible. This needs to be done not only so that your transistor has time to operate at high frequencies. The higher the gate voltage of the transistor, the lower the channel resistance for MOSFETs or the lower the collector-emitter saturation voltage for IGBT transistors. The threshold voltage for opening transistors is usually 2–4 volts, and the maximum at which the transistor is fully open is 10–15 volts. Therefore, a voltage of 10-15 volts should be applied. But even in this case, the gate capacitance is not charged immediately and for some time the transistor operates in the nonlinear part of its characteristic with a high channel resistance, which leads to a large voltage drop across the transistor and its excessive heating. This is the so-called manifestation of the Miller effect.
In order for the gate capacitance to quickly charge and the transistor to open, it is necessary that your control circuit can provide as much charging current as possible to the transistor. The gate capacitance of the transistor can be found from the passport data for the product and when calculating, you should take Cv = Ciss.
For example, let's take the MOSFET transistor IRF740. It has the following characteristics that interest us:
Opening Time (Rise Time - Tr) = 27 (ns)
Closing time (Fall Time - Tf) = 24 (ns)
Input Capacitance - Ciss = 1400 (pF)
We calculate the maximum opening current of the transistor as:
We determine the maximum closing current of the transistor using the same principle:
Since we usually use 12 volts to power the control circuit, we will determine the current-limiting resistor using Ohm’s law.
That is, resistor Rg=20 Ohm, according to the standard E24 series.
Please note that it is not possible to control such a transistor directly from the controller; I will introduce that the maximum voltage that the controller can provide will be within 5 volts, and the maximum current within 50 mA. The controller output will be overloaded, and the transistor will exhibit the Miller effect, and your circuit will fail very quickly, since someone, either the controller or the transistor, will overheat first.
Therefore, it is necessary to choose the right driver.
The driver is a pulse power amplifier and is designed to control power switches. Drivers can be upper and lower keys separately, or combined into one housing into an upper and lower key driver, for example, such as IR2110 or IR2113.
Based on the information presented above, we need to select a driver capable of maintaining the transistor gate current Ig = 622 mA.
Thus, we will use the IR2011 driver capable of supporting a gate current Ig = 1000 mA.
It is also necessary to take into account the maximum load voltage that the switches will switch. In this case it is equal to 200 volts.
The next very important parameter is the locking speed. This eliminates the flow of through currents in the push-pull circuits shown in the figure below, causing losses and overheating.
If you carefully read the beginning of the article, then according to the passport data of the transistor you can see that the closing time should be less than the opening time and, accordingly, the turning-off current should be higher than the opening current If>Ir. It is possible to provide a larger closing current by reducing the resistance Rg, but then the opening current will also increase, this will affect the magnitude of the switching voltage surge when switching off, depending on the rate of current decay di/dt. From this point of view, an increase in switching speed is a largely negative factor that reduces the reliability of the device.
In this case, we will take advantage of the remarkable property of semiconductors to pass current in one direction, and install a diode in the gate circuit that will pass the turn-off current of the transistor If.
Thus, the gate current Ir will flow through resistor R1, and the gate current If will flow through diode VD1, and since the resistance of the p–n junction of the diode is much less than the resistance of resistor R1, then If>Ir. To ensure that the turn-off current does not exceed its value, we connect a resistor in series with the diode, the resistance of which will be determined by neglecting the resistance of the diode in the open state.
Let's take the nearest smaller one from the standard series E24 R2=16 Ohm.
Now let's look at what the name of the upper key driver and lower key driver mean.
It is known that MOSFET and IGBT transistors are controlled by voltage, namely the gate-source voltage (Gate-Source) Ugs.
What are the upper and lower keys? The figure below shows a diagram of a half-bridge. This circuit contains upper and lower keys, VT1 and VT2, respectively. The upper switch VT1 is connected by the drain to the positive supply Vcc, and by the source to the load and must be opened by a voltage applied relative to the source. The lower key, the drain is connected to the load, and the source is connected to the power supply negative (ground), and must be opened by voltage applied relative to the ground.
And if everything is very clear with the lower key, apply 12 volts to it - it opens, apply 0 volts to it - it closes, then for the upper key you need a special circuit that will open it relative to the voltage at the source of the transistor. This scheme is already implemented inside the driver. All we need is to add boost capacitance C2 to the driver, which will be charged by the driver supply voltage, but relative to the source of the transistor, as shown in the figure below. It is with this voltage that the top key will be unlocked.
This circuit is quite workable, but the use of a booster capacitance allows it to operate in narrow ranges. This capacitance is charged when the lower transistor is open and cannot be too large if the circuit must operate at high frequencies, and also cannot be too small when operating at low frequencies. That is, with this design, we cannot keep the upper switch open indefinitely; it will close immediately after capacitor C2 is discharged, but if we use a larger capacitance, it may not have time to recharge by the next period of operation of the transistor.
We have encountered this problem more than once and very often had to experiment with selecting a booster capacitance when changing the switching frequency or the operating algorithm of the circuit. The problem was solved over time and very simply, in the most reliable and “almost” cheap way. While studying the Technical Reference for the DMC1500, we became interested in the purpose of the P8 connector.
Having carefully read the manual and thoroughly understood the circuit of the entire drive, it turned out that this is a connector for connecting a separate, galvanically isolated power supply. We connect the minus of the power supply to the source of the upper switch, and the plus to the input of the Vb driver and the positive leg of the booster capacitance. Thus, the capacitor is constantly charged, making it possible to keep the upper key open for as long as necessary, regardless of the state of the lower key. This addition to the scheme allows you to implement any key switching algorithm.
As a power source for charging the booster capacitance, you can use either a conventional transformer with a rectifier and a filter, or a DC-DC converter.
FET Drivers
MOSFET and IGBT transistor drivers are devices for controlling powerful semiconductor devices in the output stages of electrical energy converters. They are used as an intermediate link between the control circuit (controller or digital signal processor) and powerful actuators.
The stages of development of energy (power) electronics are determined by advances in the technologies of power switches and their control circuits. The dominant direction in power electronics is to increase the operating frequencies of converters that are part of switching power supplies. Converting electricity at higher frequencies makes it possible to improve the specific weight and size characteristics of pulse transformers, capacitors and filter chokes. The dynamic and static parameters of power devices are constantly being improved, but powerful switches must also be effectively controlled. Powerful high-speed drivers of MOSFET and IGBT transistors are designed for balanced interaction between the control circuit and the output stages. The drivers have high output currents (up to 9 A), short rise times, fall times, delays and other interesting distinctive features. The driver classification is shown in Figure 2.15.
Figure 2.15 - Classification of drivers
The driver must have at least one external pin (two in push-pull circuits), which is mandatory. It can serve either as a pre-switching amplifier or directly as a key element in a switching power supply.
Bipolar transistors, MOS transistors and trigger-type devices (thyristors, triacs) can be used as a controlled device in power circuits for various purposes. The requirements for a driver that provides optimal control in each of these cases are different. The bipolar transistor driver must control the base current when turned on and ensure the resorption of minority carriers in the base during the turn-off stage. The maximum values of the control current differ little from the average values over the corresponding interval. The MOS transistor is controlled by voltage, however, at the beginning of the on and off intervals, the driver must pass large pulse currents of charging and discharging the device’s capacitors. Trigger-type devices require the formation of a short current pulse only at the beginning of the switching interval, since switching off (switching) for the most common devices occurs along the main, and not the control, electrodes. All these requirements must be met to one degree or another by the corresponding drivers.
Figures 2.16...2.18 show typical circuits for connecting bipolar and field-effect MOSFET transistors using one transistor in the driver. These are so-called circuits with passive switching off of the power transistor. As can be seen from the figure, the structure of the driver circuits is completely identical, which makes it possible to use the same circuits to control transistors of both types. In this case, the resorption of carriers accumulated in the structure of the transistor occurs through a passive element - an external resistor. Its resistance, which shunts the control transition not only when turned off, but also during the turn-on interval, cannot be chosen too small, which limits the rate of charge resorption.
To increase the speed of the transistor and create high-frequency switches, it is necessary to reduce the resistance of the charge reset circuit. This is done using a reset transistor, which is turned on only during the pause interval. The corresponding control circuits for bipolar and MOS transistors are presented in Figure 2.17.
The article is devoted to the developments of Electrum AV LLC for industrial applications, whose characteristics are similar to modular devices produced by Semikron and CT Concept.
Modern concepts for the development of power electronics and the level of technological basis of modern microelectronics determine the active development of systems built on IGBT devices of various configurations and power. In the state program “National Technological Base”, two works are devoted to this area on the development of a series of medium-power IGBT modules at the Kontur enterprise (Cheboksary) and a series of high-power IGBT modules at the Kremniy enterprise (Bryansk). At the same time, the use and development of systems based on IGBT modules is limited by the lack of domestic driver devices for controlling IGBT gates. This problem is also relevant for high-power field-effect transistors used in converter systems with voltages up to 200 V.
Currently, control devices for high-power field-effect and IGBT transistors are represented on the Russian “electronic” market by Agilent Technologies, IR, Powerex, Semikron, and CT Concept. IR and Agilent products contain only a device for generating transistor control signals and protective circuits and, in the case of working with high-power transistors or at high frequencies, require additional elements for their use: a DC/DC converter of the required power to generate the supply voltages of the output stages, powerful external output stages for generating gate control signals with the required steepness of edges, protective elements (zener diodes, diodes, etc.), control system interface elements (input logic, generation of control diagrams for half-bridge devices, optically isolated status signals of the state of the controlled transistor, supply voltages etc.). Powerex products also require a DC/DC converter, and additional external components are required for matching with TTL, CMOS and fiber optics. There are also no necessary status signals with galvanic isolation.
The most functionally complete drivers are from Semikron (SKHI series) and CT Concept (Standard or SCALE types). CT Concept drivers of the Standart series and SKHI drivers are made in the form of printed circuit boards with connectors for connecting to the control system and controlled transistors with the necessary elements installed on them and with the ability to install tuning elements by the consumer. The products are similar in their functional and parametric features.
The range of SKHI drivers is shown in Table 1.
Table 1. Nomenclature of SKHI drivers
| Semikron driver type | Number of channels | Max voltage to control. transistor,V | Gate voltage change, V | Max imp. exit current, A | Max gate charge, µC | Frequency, kHz | Insulation voltage, kV | DU/dt, kV/µs |
| SKHI 10/12 | 1 | 1200 | +15/–8 | 8 | 9,6 | 100 | 2,5 | 75 |
| SKHI 10/17 | 1 | 1700 | +15/–8 | 8 | 9,6 | 100 | 4 | 75 |
| SKHI 21A | 1 | 1200 | +15/–0 | 8 | 4 | 50 | 2,5 | 50 |
| SKHI 22A/22B | 2 | 1200 | +15/–7 | 8 | 4 | 50 | 2,5 | 50 |
| SKHI 22A/H4 | 2 | 1700 | +15/–7 | 8 | 4 | 50 | 4 | 50 |
| SKHI 22V/H4 | 2 | 1700 | +15/–7 | 8 | 4 | 50 | 4 | 50 |
| SKHI 23/12 | 2 | 1200 | +15/–8 | 8 | 4,8 | 100 | 2,5 | 75 |
| SKHI 23/17 | 2 | 1700 | +15/–8 | 8 | 4,8 | 100 | 4 | 75 |
| SKHI 24 | 2 | 1700 | +15/–8 | 8 | 5 | 50 | 4 | 50 |
| SKHI 26W | 2 | 1600 | +15/–8 | 8 | 10 | 100 | 4 | 75 |
| SKHI 26F | 2 | 1600 | +15/–8 | 8 | 10 | 100 | 4 | 75 |
| SKHI 27W | 2 | 1700 | +15/–8 | 30 | 30 | 10 | 4 | 75 |
| SKHI 27F | 2 | 1700 | +15/–8 | 30 | 30 | 10 | 4 | 75 |
| SKHI 61 | 6 | 900 | +15/–6,5 | 2 | 1 | 50 | 2,5 | 15 |
| SKHI 71 | 7 | 900 | +15/–6,5 | 2 | 1 | 50 | 2,5 | 15 |
| SKHIВS 01 | 7 | 1200 | +15/–8 | 1,5 | 0,75 | 20 | 2,5 | 15 |
CT Concept SCALE drivers are made on the basis of a basic hybrid assembly and include the main elements for controlling powerful field-effect or IGBT transistors, which are mounted on a printed circuit board, with the ability to install the necessary tuning elements. The board is also equipped with the necessary connectors and sockets.
The range of basic hybrid SCALE driver assemblies from CT Concept is shown in Table 2.
Driver devices produced by Electrum AV are completely finished, functionally complete devices containing all the necessary elements for controlling the gates of powerful transistors, providing the necessary levels of matching of current and potential signals, durations of edges and delays, as well as the necessary levels of protection of controlled transistors at dangerous saturation voltage levels (current overload or short circuit) and insufficient voltage at the gate. The DC/DC converters and transistor output stages used have the necessary power to ensure switching of controlled transistors of any power at a sufficient speed to ensure minimal switching losses. DC/DC converters and optocouplers have sufficient levels of galvanic isolation for use in high voltage systems.
Table 2. Nomenclature of basic hybrid SCALE driver assemblies from CT Concept
| Driver type from CT Concept | Number of channels | Driver supply voltage, V | Max imp. output current, A | Max voltage on control. transistor,V | Output power, W | Latency, ns | Insulation voltage, V | du/dt, kV/μs | Entrance |
| IGD 508E | 1 | ±15 | ±8 | 3300 | 5 | 225 | 5000 | Vols | |
| IGD 515E | 1 | ±15 | ±15 | 3300 | 5 | 225 | 5000 | Vols | |
| IGD 608E | 1 | ±15 | ±8 | 1200 | 6 | 60 | 4000 | >50 | Trance |
| IGD608A1 17 | 1 | ±15 | ±8 | 1700 | 6 | 60 | 4000 | >50 | Trance |
| IGD 615A | 1 | ±15 | ±15 | 1200 | 6 | 60 | 4000 | >50 | Trance |
| IGD615A1 17 | 1 | ±15 | ±15 | 1700 | 6 | 60 | 4000 | >50 | Trance |
| IHD 215A | 2 | ±15 | ±1.5 | 1200 | 1 | 60 | 4000 | >50 | Trance |
| IHD 280A | 2 | ±15 | ±8 | 1200 | 1 | 60 | 4000 | >50 | Trance |
| IHD280A1 17 | 2 | ±15 | ±8 | 1700 | 1 | 60 | 4000 | >50 | Trance |
| IHD 680A | 2 | ±15 | ±8 | 1200 | 3 | 60 | 4000 | >50 | Trance |
| IHD680A1 17 | 2 | ±15 | ±8 | 1700 | 3 | 60 | 4000 | >50 | Trance |
| IHD 580 F | 2 | ±15 | ±8 | 2500 | 2,5 | 200 | 5000 | Vols |
This article will present devices MD115, MD150, MD180 (MD115P, MD150P, MD180P) for controlling single transistors, as well as MD215, MD250, MD280 (MD215P, MD250P, MD280P) for controlling half-bridge devices.
Driver module for single-channel IGBT and high-power field-effect transistors: MD115, MD150, MD180, MD115P, MD150P, ID180P
The driver module MD115, MD150, MD180, MD115P, MD150P, MD180P is a hybrid integrated circuit for controlling IGBTs and powerful field-effect transistors, including when they are connected in parallel. The module provides matching of current and voltage levels with most IGBTs and high-power field-effect transistors with a maximum permissible voltage of up to 1700 V, protection against overload or short circuit, and against insufficient voltage at the transistor gate. The driver generates an “alarm” signal when the operating mode of the transistor is violated. Using external elements, the driver operating mode is adjusted for optimal control of different types of transistors. The driver can be used to drive transistors with "Kelvin" outputs or to control current using a current sensing resistor. The MD115P, MD150P, MD180P devices contain a built-in DC/DC converter to power the driver output stages. Devices MD115, MD150, MD180 require an external isolated power source.
Pin assignment
1 - “emergency +” 2 - “emergency –” 3 - “input +” 4 - “input –” 5 - “U power +” (only for models with the index “P”) 6 - “U power –” (only for models with the index “P”) 7 - “General” 8 - “+E power” 9 - “output” - transistor gate control 10 - “–E power” 11 - “forward” - saturation voltage control input of the controlled transistor 12 - “current” - input for monitoring the current flowing through the controlled transistor
Driver modules for dual-channel IGBT and power field-effect transistors IA215, IA250, IA280, IA215I, IA250I, IA280I
Driver modules MD215, MD250, MD280, MD215P, MD250P, MD280P are a hybrid integrated circuit for controlling IGBTs and powerful field-effect transistors via two channels, both independently and in half-bridge connection, including when transistors are connected in parallel. The driver provides matching of current and voltage levels with most IGBTs and high-power field-effect transistors with maximum permissible voltages up to 1700 V, protection against overloads or short circuits, and insufficient voltage level at the transistor gate. The driver inputs are galvanically isolated from the power unit with an insulation voltage of 4 kV. The driver contains internal DC/DC converters that form the necessary levels to control the gates of transistors. The device generates the necessary status signals that characterize the operating mode of the transistors, as well as the availability of power. Using external elements, the driver operating mode is adjusted for optimal control of different types of transistors.
Table 4. Pin designation of the dual-channel IGBT driver module and power field-effect transistors
| Pin No. | Designation | Function | Pin No. | Designation | Function |
| 14 | ВХ1 “+” | Channel 1 direct control input | 15 | IR | Measuring collector for monitoring the saturation voltage on the controlled transistor of the first channel |
| 13 | ВХ1 “–” | Inverse control input of the first channel | 16 | IR1 | Saturation voltage control input with adjustable threshold and blocking time of the first channel |
| 12 | ST "+E pit" | Status of the supply voltage of the output stage of the first channel | 17 | Out2 | Transistor gate control output with adjustable turn-on time of the controlled transistor of the first channel |
| 11 | NW | Input for connecting an additional capacitor (setting the turn-on delay time) of the first channel | 18 | Out1 | Transistor gate control output with adjustable turn-off time of the controlled transistor of the first channel |
| 10 | ST | Status alarm output on the controlled transistor of the first channel | 19 | –E pit | |
| 9 | BLOCK | Lock input | 20 | General | Supply voltage outputs of the power section of the driver of the first channel |
| 8 | Not involved | 21 | +E pit | Supply voltage outputs of the power section of the driver of the first channel | |
| 7 | +5V | 22 | +E pit " | ||
| 6 | Input for connecting power to the input circuit | 23 | General" | Supply voltage outputs of the power section of the second channel driver | |
| 5 | ВХ2 “+” | Channel 2 direct control input | 24 | –E pit " | Supply voltage outputs of the power section of the second channel driver |
| 4 | ВХ2 “–” | Inverse control input of the second channel | 25 | Out1" | Transistor gate control output with adjustable turn-on time of the controlled transistor of the second channel |
| 3 | ST “+E pit”9 | Status of the supply voltage of the output stage of the second channel | 26 | Out2" | Transistor gate control output with adjustable turn-off time of the controlled transistor of the second channel |
| 2 | Sz9 | Input for connecting an additional capacitor (setting the switching delay time) of the second channel | 27 | IK1" | Saturation voltage control input with adjustable threshold and blocking time of the second channel |
| 1 | ST9 | Status alarm output on the controlled transistor of the second channel | 28 | IR" | Measuring collector for monitoring the saturation voltage on the controlled transistor of the second channel |
Devices of both types MD1ХХХ and MD2ХХХ provide the generation of transistor gate control signals with separately adjustable values of charging and discharge currents, with the required dynamic parameters, provide voltage control and protection of transistor gates in the event of insufficient or excessive voltage on them. Both types of devices monitor the saturation voltage of the controlled transistor and perform a smooth emergency load shutdown in critical situations, generating an optocoupler signal indicating this. In addition to these functions, the MD1XXX series devices have the ability to control the current through a controlled transistor using an external current-measuring resistor - a “shunt”. Such resistors, with resistances from 0.1 to several mOhms and powers of tens and hundreds of W, made on ceramic bases in the form of nichrome or manganin strips of precise geometry with adjustable nominal values, were also developed by Electrum AV LLC. More detailed information about them can be found on the website www.orel.ru/voloshin.
Table 5. Basic electrical parameters
| Input circuit | ||||
| min. | type. | Max. | ||
| Supply voltage, V | 4,5 | 5 | 18 | |
| Current consumption, mA | no more than 80 without load no more than 300 mA with load | |||
| Input logic | CMOS 3–15 V, TTL | |||
| Current at control inputs, mA | no more than 0.5 | |||
| Output voltage st, V | no more than 15 | |||
| Output current st, mA | at least 10 | |||
| Output circuit | ||||
| Peak output current, A | ||||
| MD215 | no more than 1.5 | |||
| MD250 | no more than 5.0 | |||
| MD280 | no more than 8.0 | |||
| Output average current, mA | no more than 40 | |||
| Maximum switching frequency, kHz | not less than 100 | |||
| Rate of voltage change, kV/µs | at least 50 | |||
| Maximum voltage on the controlled transistor, V | not less than 1200 | |||
| DC/DC converter | ||||
| Output voltage, V | at least 15 | |||
| Power, W | no less than 1 no less than 6 (for models with index M) | |||
| Efficiency | at least 80% | |||
| Dynamic characteristics | ||||
| Delay input output t on, µs | no more than 1 | |||
| Protective shutdown delay t off, µs | no more than 0.5 | |||
| Status turn-on delay, μs | no more than 1 | |||
| Recovery time after protection is triggered, μs | no more than 10 | |||
| at least 1 (set by capacitances Сt,Сt") | ||||
| Response time of the saturation voltage protection circuit when the transistor is turned on tblock, µs | at least 1 | |||
| Threshold voltages | ||||
| min. | type. | Max. | ||
| Protection threshold for insufficient power supply E, V | 10,4 | 11 | 11,7 | |
| The saturation voltage protection circuit of the controlled transistor ensures that the output is turned off and the CT signal is generated at a voltage at the input “IR”, V | 6 | 6,5 | 7 | |
| Insulation | ||||
| Isolation voltage of control signals relative to power signals, V | not less than 4000 AC voltage | |||
| DC/DC converter insulation voltage, V | not less than 3000 DC voltage | |||
The proposed drivers allow you to control transistors at high frequencies (up to 100 kHz), which allows you to achieve very high efficiency of conversion processes.
Devices of the MD2ХХХ series have a built-in input logic block that allows you to control signals with different values from 3 to 15 V (CMOS) and standard TTL levels, while providing an identical level of transistor gate control signals and forming a switching delay duration of the upper and higher voltages, adjustable using external capacitors. the lower arm of the half-bridge, which ensures the absence of through currents.
Features of using drivers using the example of the MD2ХХХ device
Short review
Driver modules MD215, MD250, MD280, MD215P, MD250P, MD280P are universal control modules designed for switching IGBTs and high-power field-effect transistors.
All types MD2ХХХ have mutually compatible contacts and differ only in the level of maximum pulse current.
MD types with higher powers - MD250, MD280, MD250P, MD280P are well suited for most modules or several parallel-connected transistors used at high frequencies.
The MD2XXX series driver modules provide a complete solution to control and protection problems for IGBTs and power field-effect transistors. In fact, no additional components are required on either the input or output side.
Action
Driver modules MD215, MD250, MD280, MD215P, MD250P, MD280P for each of the two channels contain:
- input circuit providing signal level matching and protective switching delay;
- electrical isolation between the input circuit and the power (output) part;
- transistor gate control circuit; on an open transistor;
- circuit for monitoring the supply voltage level of the power part of the driver;
- amplifier;
- protection against voltage surges in the output part of the driver;
- electrically isolated voltage source - DC//DC converter (only for modules with index P)
Both driver channels operate independently of each other.
Thanks to the electrical isolation provided by transformers and optocouplers (subjected to a test voltage of 2650 V AC at 50 Hz for 1 minute) between the input circuit and the power section, as well as an extremely high voltage slew rate of 30 kV/µs, driver modules are used in circuits with large potential voltages and large potential jumps occurring between the power part and the control circuit.
The very short delay times of the drivers of the MD2XXX series allow them to be used in high-frequency power supplies, high-frequency converters and resonance converters. Thanks to their extremely short delay times, they guarantee trouble-free operation during bridge control.
One of the main functions of MD2ХХХ series drivers is to guarantee reliable protection of controlled power transistors from short circuits and overloads. The emergency state of the transistor is determined using the voltage on the collector of the power transistor in the open state. If a user-defined threshold is exceeded, the power transistor turns off and remains disabled until the active signal level at the control input ends. After this, the transistor can be turned on again by applying an active level to the control input. This protection concept is widely used to reliably protect IGBTs.
Functional assignment of pins
Pins 14 (VX1 “+”), 13 (VX1 “–”)
Pins 13 and 14 are the driver control inputs. Control is carried out by applying TTL logical levels to them. The input In1 “+” is direct, that is, when a logical 1 is applied to it, the power transistor opens, and when a 0 is applied, it closes. The input In1 “–” is inverse, that is, when logical 1 is applied to it, the power transistor closes, and when 1 is applied, it opens. Typically, In1 “–” is connected to the common conductor of the input part of the driver, and it is controlled using the In1 “+” input. Inverting and non-inverting driver connection is shown in Fig. 10.
Table 6 shows the state diagram of one driver channel.
Electrical isolation between the input and output parts of the driver at these pins is carried out using optocouplers. Thanks to their use, the possibility of the influence of transient processes occurring on the power transistor on the control circuit is eliminated.
Table 6. State diagram of one driver channel
| In1+ | In1– | Transistor gate voltage | Transistor saturation voltage >normal | St | St "+E pit" | Out |
| X | X | + | X | X | L | L |
| x | x | x | + | l | N | l |
| l | x | x | x | x | N | l |
| x | H | x | x | x | H | l |
| H | l | - | - | H | H | H |
The input circuit has built-in protection that prevents both power transistors of the half-bridge from opening simultaneously. If an active control signal is applied to the control inputs of both channels, the circuit will be blocked and both power transistors will be closed.
Driver modules should be located as close as possible to the power transistors and connected to them with the shortest possible conductors. Inputs In1 “+” and In1 “–” can be connected to the control and monitoring circuit with conductors up to 25 cm long.
Moreover, the conductors must run in parallel. In addition, the inputs In1 “+” and In1 “–” can be connected to the control and monitoring circuit using a twisted pair. The common conductor to the input circuit must always be connected separately for both channels to ensure reliable transmission of control pulses.
Taking into account that reliable transmission of control pulses occurs in the case of a very long pulse, the complete configuration must be checked in the case of a minimally short control pulse.
Pin 12 (ST “+E pit”)
Pin 12 is a status output that confirms the presence of power (+18 V) at the output (power) part of the driver. It is assembled according to an open collector circuit. When the driver is operating normally (power supply is available and its level is sufficient), the status pin is connected to the common pin of the control circuit using an open transistor. If this status pin is connected according to the diagram shown in Fig. 11, then an emergency situation will correspond to a high voltage level on it (+5 V). Normal driver operation will correspond to a low voltage level at this status pin. The typical value of the current flowing through the status pin corresponds to 10 mA, therefore, the value of the resistor R is calculated using the formula R = U / 0.01,
where U is the supply voltage. When the supply voltage drops below 12 V, the power transistor is turned off and the driver is blocked.
Pin 11 (Сз)
An additional capacitor is connected to pin 11, which increases the delay time between the input and output pulse ton on the driver. By default (without an additional capacitor) this time is exactly 1 μs, due to which the driver does not respond to pulses shorter than 1 μs (protection against impulse noise). The main purpose of this delay is to eliminate the occurrence of through currents arising in half-bridges. Through currents cause heating of power transistors, activation of emergency protection, increase current consumption, and deteriorate the efficiency of the circuit. By introducing this delay, both channels of a half-bridge loaded driver can be driven by a single square wave signal.
For example, the 2MBI 150 module has a turn-off delay of 3 μs; therefore, in order to prevent the occurrence of through currents in the module when the channels are jointly controlled, it is necessary to install an additional capacitance of at least 1200 pF on both channels.
To reduce the influence of ambient temperature on the delay time, it is necessary to select capacitors with low TKE.
Pin 10 (ST)
Pin 10 is the status output of an alarm on the power transistor of the first channel. A high logic level at the output corresponds to normal driver operation, and a low level corresponds to an emergency. An accident occurs when the saturation voltage on the power transistor exceeds the threshold level. The maximum current flowing through the output is 8 mA.
Pin 9 (BLOCK)
Pin 6 is the driver control input. When a logical unit is applied to it, the driver’s operation is blocked and a blocking voltage is supplied to the power transistors. The blocking input is common to both channels. For normal operation of the driver, a logical zero must be applied to this input.
Pin 8 is not used.
Pins 7 (+5 V) and 6 (common)
Pins 6 and 7 are inputs for connecting power to the driver. Power is supplied from a source with a power of 8 W and an output voltage of 5 ± 0.5 V. The power must be connected to the driver with short conductors (to reduce losses and increase noise immunity). If the connecting conductors have a length of more than 25 cm, it is necessary to place noise-suppressing capacitors (ceramic capacitor with a capacity of 0.1 μF) between them as close as possible to the driver.
Pin 15 (IR)
Pin 15 (measuring collector) is connected to the collector of the power transistor. Through it, the voltage on the open transistor is controlled. In the event of a short circuit or overload, the voltage across the open transistor increases sharply. When the threshold voltage value at the transistor collector is exceeded, the power transistor is turned off and the ST alarm status is triggered. Time diagrams of the processes occurring in the driver when the protection is triggered are shown in Fig. 7. The protection response threshold can be reduced by connecting diodes connected in series, and the threshold value of the saturation voltage is U us. por.=7 –n U pr.VD, where n is the number of diodes, U pr.VD is the voltage drop across the open diode. If the power transistor is powered from a 1700 V source, it is necessary to install an additional diode with a breakdown voltage of at least 1000 V. The cathode of the diode is connected to the collector of the power transistor. The protection response time can be adjusted using pin 16-IK1.
Pin 16 (IC1)
Pin 16 (measuring collector), unlike pin 15, does not have a built-in diode and a limiting resistor. It is necessary to connect a capacitor, which determines the response time of the protection based on the saturation voltage on an open transistor. This delay is necessary to prevent interference from affecting the circuit. By connecting a capacitor, the protection response time increases in proportion to the blocking capacitance t = 4 C U us. por., where C is the capacitance of the capacitor, pF. This time is summed with the driver’s internal delay time t off (10%) = 3 µs. By default, the driver contains capacitance C = 100 pF, therefore, the protection response delay is t = 4 100 6.3 + t off (10%) = 5.5 μs. If necessary, this time can be increased by connecting a capacitance between pin 16 and the common power supply wire of the power unit.
Pins 17 (out. 2) and 18 (out. 1)
Pins 17 and 18 are driver outputs. They are designed to connect power transistors and adjust their turn-on time. Pin 17 (out. 2) supplies a positive potential (+18 V) to the gate of the controlled module, and pin 18 (out. 1) supplies a negative potential (–5 V). If it is necessary to ensure steep control edges (about 1 μs) and not very high load power (two 2MBI 150 modules connected in parallel), direct connection of these outputs to the control pins of the modules is permissible. If you need to tighten the edges or limit the control current (in case of heavy load), then the modules must be connected to pins 17 and 18 through limiting resistors.
If the saturation voltage exceeds the threshold level, a protective smooth decrease in voltage occurs at the gate of the control transistor. Time to reduce the voltage at the transistor gate to the level of 90%t off (90%) = 0.5 μs, to the level of 10%t off (10%) = 3 μs. A smooth decrease in the output voltage is necessary in order to eliminate the possibility of a voltage surge.
Pins 19 (–E supply), 20 (Common) and 21 (+E supply)
Pins 19, 20 and 21 are the power outputs of the driver power section. These pins receive voltage from the driver DC/DC converter. In the case of using drivers such as MD215, MD250, MD280 without built-in DC/DC converters, external power supplies are connected here: 19 pin –5 V, 20 pin - common, 21 pin +18 V for a current of up to 0.2 A.
Driver calculation and selection
The initial data for the calculation is the input capacitance of the module C in or the equivalent charge Q in, the input resistance of the module R in, the voltage swing at the module input. U = 30 V (given in the reference information for the module), the maximum operating frequency at which the module operates f max.
It is necessary to find the pulse current flowing through the control input of the module Imax, the maximum power of the DC/DC converter P.
Figure 16 shows the equivalent circuit of the module input, which consists of a gate capacitance and a limiting resistor.
If the charge Qin is specified in the source data, then it is necessary to recalculate it into the equivalent input capacitance Cin =Qin /D U.
The reactive power allocated to the input capacitance of the module is calculated by the formula Рс =f Q input D U. The total power of the DC/DC converter of the driver Р is the sum of the power consumed by the output stage of the driver Рout, and the reactive power allocated to the input capacitance of the module Рс: P = P out + Pc.
The operating frequency and voltage swing at the module input were taken to be maximum in the calculations; therefore, the maximum possible power of the DC/DC converter during normal driver operation was obtained.
Knowing the resistance of the limiting resistor R, you can find the pulse current flowing through the driver: I max =D U/R.
Based on the calculation results, you can select the most optimal driver needed to control the power module.
MOP (in bourgeois MOSFET) stands for Metal-Oxide-Semiconductor, from this abbreviation the structure of this transistor becomes clear.
If on the fingers, then it has a semiconductor channel that serves as one plate of the capacitor and the second plate is a metal electrode located through a thin layer of silicon oxide, which is a dielectric. When voltage is applied to the gate, this capacitor is charged, and the electric field of the gate pulls charges to the channel, as a result of which mobile charges appear in the channel that can form an electric current and the drain-source resistance drops sharply. The higher the voltage, the more charges and lower the resistance, as a result, the resistance can drop to tiny values - hundredths of an ohm, and if you raise the voltage further, a breakdown of the oxide layer and the Khan transistor will occur.
The advantage of such a transistor, compared to a bipolar one, is obvious - voltage must be applied to the gate, but since it is a dielectric, the current will be zero, which means the required the power to control this transistor will be scanty, in fact, it only consumes at the moment of switching, when the capacitor is charging and discharging.
The disadvantage arises from its capacitive property - the presence of capacitance on the gate requires a large charging current when opening. In theory, equal to infinity on infinitely small periods of time. And if the current is limited by a resistor, then the capacitor will charge slowly - there is no escape from the time constant of the RC circuit.
MOS transistors are P and N duct. They have the same principle, the only difference is the polarity of the current carriers in the channel. Accordingly, in different directions of the control voltage and inclusion in the circuit. Very often transistors are made in the form of complementary pairs. That is, there are two models with exactly the same characteristics, but one of them is N channel, and the other is P channel. Their markings, as a rule, differ by one digit.
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My most popular MOP transistors are IRF630(n channel) and IRF9630(p channel) at one time I made about a dozen of them of each type. Possessing a not very large body TO-92 this transistor can famously pull through itself up to 9A. Its open resistance is only 0.35 Ohm.
However, this is a fairly old transistor; now there are cooler things, for example IRF7314, capable of carrying the same 9A, but at the same time it fits into an SO8 case - the size of a notebook square.
One of the docking problems MOSFET transistor and microcontroller (or digital circuit) is that in order to fully open until completely saturated, this transistor needs to drive quite a bit more voltage onto the gate. Usually this is about 10 volts, and the MK can output a maximum of 5.
There are three options:
But in general, it is more correct to install a driver, because in addition to the main functions of generating control signals, it also provides current protection, protection against breakdown, overvoltage, as an additional bauble, optimizes the opening speed to the maximum, in general, it does not consume its current in vain. Choosing a transistor is also not very difficult, especially if you don’t bother with limiting modes. First of all, you should be concerned about the value of the drain current - I Drain or I D you choose a transistor based on the maximum current for your load, preferably with a margin of 10 percent. The next important parameter for you is VGS- Source-Gate saturation voltage or, more simply, control voltage. Sometimes it is written, but more often you have to look at the charts. Looking for a graph of the output characteristic Dependency I D from VDS at different values VGS. And you figure out what kind of regime you will have.
For example, you need to power the engine at 12 volts, with a current of 8A. You screwed up the driver and only have a 5 volt control signal. The first thing that came to mind after this article was IRF630. The current is suitable with a margin of 9A versus the required 8. But let’s look at the output characteristic:
If you are going to use PWM on this switch, then you need to inquire about the opening and closing times of the transistor, choose the largest one and, relative to the time, calculate the maximum frequency of which it is capable. This quantity is called Switch Delay or t on,t off, in general, something like this. Well, the frequency is 1/t. It’s also a good idea to look at the gate capacity C iss Based on it, as well as the limiting resistor in the gate circuit, you can calculate the charging time constant of the RC gate circuit and estimate the performance. If the time constant is greater than the PWM period, then the transistor will not open/close, but will hang in some intermediate state, since the voltage at its gate will be integrated by this RC circuit into a constant voltage.
When handling these transistors, keep in mind the fact that They are not just afraid of static electricity, but VERY STRONG. It is more than possible to penetrate the shutter with a static charge. So how did I buy it? immediately into foil and don’t take it out until you seal it. First ground yourself to the battery and put on a foil hat :).
