WO2021110405A1 - Gate driver for controlling a power switch - Google Patents

Abstract

The invention relates to a gate driver for controlling a power switch, in particular a bipolar transistor with insulated gate electrode, IGBT, or a power MOSFET, with a high-side system and a low-side system. A high-side switch and a high-side diode are provided in the high-side system, and a low-side switch and a low-side diode are provided in the low-side system. The high-side switch is connected to the high-side diode, and the low-side switch is connected to the low-side diode. The interconnected high-side switch and high-side diode and the interconnected low-side switch and low-side diode are connected to a phase connector of the power switch. For measurement of a voltage the low-side system has a measuring device which is connected to the anode of at least one intermediate diode, the cathode of which is connected to the voltage to be measured in the high-side system of the power switch.

Description

description

title

Gate driver for controlling a circuit breaker

The invention relates to a gate driver for driving a power switch.

State of the art

For the operation of electric drives in hybrid and / or electric vehicles, pulse inverters are used to control electrical machines, which convert an input DC voltage into a three-phase output voltage system with variable amplitude and / or frequency.

To control the corresponding switching elements (e.g. IGBT or power FETs), supply systems for gate control are required. The positive gate supply voltage must be tolerated relatively closely. If the positive gate voltage is too high, e.g. in the event of a short circuit in a switching element, this will result in a short circuit current that is no longer controllable or in damage to the gate. If the positive gate voltage is too low, the on-state losses are too high and the switching losses increase.

There are also restrictions for the negative gate voltage that are comparable to those for the positive gate voltage.

So far, these requirements have been met by appropriate voltage regulators, for example by downstream linear regulators.

The document DE 10 2017 104983 A1 discloses a vehicle comprising an electric machine, an IGBT and a gate driver. The IGBT has a gate, an emitter and a collector and is configured to pass an electrical charge through a phase of the electrical machine. The gate driver is for conducting current to the gate at a first level and, in response to a time integral of a voltage across the phase exceeding a predetermined level, for transitioning from the first level to a second level which is less configured as the first level.

From the publication DE 10 2018 100 460 A1 a power supply system for vehicles is known that can include a gate driver that is configured to control a traction gate and a generator gate, which correspond to switches of a controllable voltage converter, so that the gates have alternating ON periods of pulse width modulation. The gates can be activated in response to the fact that a throughput value falls below a threshold value. The gate driver may further be configured to drive the gates such that a duty cycle of one of the gates in response to the throughput exceeding the threshold is zero.

Disclosure of the invention

The present invention provides a gate driver for driving a circuit breaker according to claim 1.

Preferred further developments are the subject of the subclaims.

Advantages of the invention

The invention relates to a gate driver for controlling a power switch, in particular a bipolar transistor with an insulated gate electrode, IGBT, or a power MOSFET, with a high-side system and a low-side system. A high-side switch and a high-side diode are provided in the high-side system, and a low-side switch and a low-side diode are provided in the low-side system. The high-side switch is connected to the high-side diode, and the low-side switch is connected to the low-side diode. The interconnected high-side switch and high-side diode and the interconnected low-side switch and low-side diode are connected to one Phase connection of the circuit breaker connected. To measure a voltage, the low-side system has a measuring device which is connected to the anode of at least one intermediate diode, the cathode of which is connected to the Ga te supply voltage of the high-side circuit breaker.

According to the invention, it is possible to measure a gate supply voltage related to the high-side system or other voltages related to the high-side system by a measuring device related to the low-side system. As a result, a complex voltage regulation carried out on site by a linear regulator or switching regulator for tightly tolerated supply voltages can be saved, or a diagnosis or controllability of the voltage can be achieved using these sensors.

A measuring device related to the common ground potential of the 3 lowside systems can often be seen in a conventional gate driver, because it can perform a large number of measuring and / or control tasks in all three phases relatively inexpensively.

According to the invention, this is used to implement a simple and inexpensive solution for measuring or monitoring the gate supply voltage of a circuit breaker in the high-side system.

With a low forward voltage of the lowside switch, a sufficiently low gate supply voltage to be measured in the highside system and a sufficiently high supply voltage in the lowside system, the intermediate diode becomes conductive. A measuring device related to the lowside system can then, according to the invention, measure the gate supply voltage in the highside system at the anode of the intermediate diode during the time in which the lowside switch or the lowside diode is conductive.

In a preferred embodiment of the gate driver according to the invention, it is provided that the at least one intermediate diode is two intermediate diodes, the cathodes of which are connected to the two potentials of the gate supply voltage in the high-side system of the circuit breaker and their anodes to the input outputs of a differential amplifier are connected, and that the output of the differential amplifier is connected to the measuring device.

The present measurement of a voltage in the high-side system includes the following falsifications: The forward voltage of the lowside switch and / or the lowside diode falsifies the measurement signal and the forward voltage of the intermediate diode falsifies the measurement signal. The falsifications resulting from this procedure can be compensated as follows:

A doubling of the intermediate diode and the insertion of a differential amplifier make it possible to significantly reduce these falsifications. It only needs to be ensured that the input voltages of the differential amplifier remain in the permissible common mode range.

If the two intermediate diodes are operated at approximately the same operating point, a large part of the error is compensated for by the characteristic tolerance of the forward voltage of the intermediate diodes.

In a further preferred embodiment of the gate driver according to the invention, it is provided that a level shifter is arranged between the cathode of the at least one intermediate diode and the gate connection of the power switch.

When measuring the gate supply voltage, there is also the problem that when the gate supply voltage is high in the high-side system, measurements can no longer be made. To avoid this, the high gate supply voltage can be brought back into the measuring range by a level shifter, for example by adding a constant negative voltage, for example by a Zener diode. A level shifter is a circuit that is used to translate signal information from one voltage range to another, thereby enabling compatibility between integrated circuits with different voltage requirements. In a further preferred embodiment of the gate driver according to the invention it is provided that the differential amplifier has a peak value rectifier which is arranged between the output of the differential amplifier and the measuring device.

In the present measurement of the gate supply voltage, there is also the problem that the measurement signal is correct only during the time in which the lowside switch or the lowside diode is conductive.

In the time phase in which the high-side switch or the high-side diode is conductive, the two intermediate diodes block. If the remaining wiring in the lowside system ensures that the output of the differential amplifier goes to its minimum value, this period of time can be bridged with a peak value rectifier without an appropriate measuring signal.

In a further preferred embodiment of the gate driver according to the invention, it is provided that the high-side switch and the low-side switch are each an IGBT or MOSFET.

In a further preferred embodiment of the gate driver according to the invention it is provided that the anode of the high-side diode is connected to the source connection of the MOSFET as the high-side switch or the emitter connection of the IGBT as the high-side switch, and that the cathode of the high-side diode is connected to the drain connection of the MOSFET as the high-side switch or the collector connection of the IGBT as the high-side switch.

In a further preferred embodiment of the gate driver according to the invention it is provided that the anode of the lowside diode is connected to the source connection of the MOSFET as the lowside switch or the emitter connection of the IGBT as the lowside switch, and that the Ka method of the lowside diode is connected to the drain connection of the MOSFET as the lowside switch or the collector connection of the IGBT as the lowside switch. In a further preferred embodiment of the gate driver according to the invention, it is provided that the high-side diode is a body diode of the high-side switch, and the low-side diode is a body diode of the low-side switch.

In a further preferred embodiment of the gate driver according to the invention, it is provided that the measuring device is an analog-digital converter.

In a further preferred embodiment of the gate driver according to the invention it is provided that a microcontroller is arranged between the output of the differential amplifier and the measuring device, which is set up to sample output signals of the differential amplifier at a time.

Brief description of the drawings

The present invention is explained in more detail below with reference to the exemplary embodiments specified in the schematic figures. Show it:

1 shows a schematically illustrated embodiment of the gate driver according to the invention;

2 shows a further schematically illustrated embodiment of the gate driver according to the invention;

3 shows a further schematically illustrated embodiment of the gate driver according to the invention;

4 shows a further schematically illustrated embodiment of the gate driver according to the invention;

FIG. 5 shows an exemplary implementation of the embodiment of the gate driver according to the invention according to FIG. 4; FIG. and 6 shows the behavior of the measuring device in the event of a rise and a subsequent fall in the gate supply voltage.

Embodiments of the invention

In the figures, identical reference symbols denote identical or functionally identical elements.

The embodiment of the gate driver 100 according to the invention shown in FIG. 1 has a high-side system 20 and a low-side system 10. A high-side switch 12 and a high-side diode 14 are provided in the high-side system 20, and a low-side switch 22 and a low-side diode 24 are provided in the low-side system 10. The high-side switch 12 is connected to the high-side diode 14, and the low-side switch 22 is connected to the low-side diode 24. The interconnected high-side switch 12 and high-side diode 14 and the interconnected low-side switch 22 and low-side diode 24 are connected to a phase connection 8 of the circuit breaker. To measure a voltage, the low-side system 10 has an analog-digital converter 4 as a measuring device, which is connected to the anode of an intermediate diode 2, the cathode of the intermediate diode 2 being connected to the gate supply voltage of the circuit breaker 12 is.

If the forward voltage of the low-side switch 22 is low, the gate supply voltage 6 to be measured is low, and the supply voltage 30 is sufficiently high, the intermediate diode 2 becomes conductive. An analog-to-digital converter 4 based on the lowside can then, according to the invention, measure the gate supply voltage 6 at the anode of the intermediate diode 2.

The embodiment of the gate driver 100 according to the invention shown in FIG. 2 is an addition to the embodiment of the gate driver according to the invention according to FIG. 1. According to FIG. 2, two intermediate diodes 2 are provided, the cathodes of which are connected to the two potentials of the gate supply voltage The high-side system of the circuit breaker and its anodes are connected to the inputs of a differential amplifier, and that the output of the differential amplifier 16 is connected to the analog-digital converter 4. A doubling of the intermediate diode and the insertion of a differential amplifier makes it possible to significantly reduce the falsification of the measurement signal caused by the transmission characteristic of the lowside switch or the lowside diode. It only needs to be ensured that the input voltages of the differential amplifier remain in the permissible common mode range. If the two intermediate diodes 2 are operated at approximately the same operating point, a large part of the error is compensated for by their forward voltage.

The embodiment of the gate driver 100 according to the invention shown in FIG. 3 is an addition to the embodiment of the gate driver according to the invention according to FIG. 2. According to FIG. 3, between the cathode of the upper inter mediate diode 2 and the gate terminal 8 of the Circuit breaker a level shifter 18 is arranged.

When measuring the gate supply voltage 6, there is also the problem that when the gate supply voltage is high in the high-side system, no further measurements can be made

To avoid this, the high gate supply voltage 6 can be brought back into the measurement range by a level shifter 18, for example by adding a constant negative voltage.

The embodiment of the gate driver 100 according to the invention shown in FIG. 4 is a supplement to the embodiment of the gate driver according to the invention according to FIG. 3. According to FIG the analog-to-digital converter 4 is arranged.

In the present measurement of the gate supply voltage, there is also the problem that the measurement signal is correct only during the time in which the lowside switch or the lowside diode is conductive.

In the time phase in which the high-side switch 12 or the high-side diode 14 is conductive, the two intermediate diodes block 2. If the remaining circuitry in the low-side system 10 ensures that the output of the Differential amplifier 16 passes to its minimum value, this period of time without a valid measured value can be bridged with a peak value rectifier 26.

FIG. 5 shows an exemplary implementation of the embodiment of the gate driver according to the invention according to FIG. 4. According to FIG. 5, a Zener diode 32 and a resistor 34 of 1k ohms are provided in order to allow a negative voltage to be added to the input voltages can remain in the common mode area of the differential amplifier. The diode 2a is a decoupling diode for comparison signals of the differential amplifier 16, and the diode 2b is a decoupling diode for measurement signals. The resistance was 36 of 10k ohms and the resistor 38 of 10k ohms, a base current for the diodes 2a, 2b is possible. The arrangement with the resistor 42 of 100 ohms and the resistor 44 of 10k ohms causes a more negative voltage at the non-inverting input for the period in which the low-side is blocked, so that the output of the differential amplifier 16 jumps to the minimum value.

With resistor 46 of 2k ohms, resistor 48 of 2k ohms, resistor 52 of 20k ohms, resistor 54 of 20k ohms, resistor 56 of 22k ohms and resistor 66 of 10k ohms, as well as LM2902 as a differential amplifier, the diode 62 and the capacitor 64 of 1 nF, the differential amplifier 16 is designed with a peak value rectifier, including a first suggestion for filtering dynamic voltage overshoots between the phase connection and the reference ground of the measuring system (differential amplifier and ADC), which typically occur when the circuit breaker is switched.

The upper curve 70 shown in Fig. 6 represents the gate supply voltage to be measured of a circuit breaker and is varied positively and subsequently negatively over a sufficiently large voltage range to demonstrate the functional principle, and the lower curve 80 shown in Fig. 6 represents accordingly represents the voltage measured by the analog-to-digital converter 4.

The axis of abscissa is time while the axis of ordinate is voltages. It can be seen from curve 70 that the gate supply voltage to be measured increases from 14 V to 20 V within the first 10 ms and decreases back to 14 V within the following 10 ms.

It is clear from curve 80 that the increase in the gate supply voltage to be measured by 6 V is correctly evaluated by the analog-to-digital converter 4 on the low-side system, and that there is a slight delay in the decrease due to the peak value rectification. However, this delay is not relevant in the case of the temporal variation of the gate supply voltage to be expected here.

In an embodiment that is not shown, provision is made for the evaluation to be placed on a high-side system and for an auxiliary voltage to be monitored on the low-side system.

In a further embodiment, not shown, an evaluation of a digital signal is also possible.

In a further embodiment not shown, instead of the peak value detection, a microcontroller can also sample the signal at the appropriate point in time.

Although the present invention has been fully described above on the basis of preferred exemplary embodiments, it is not restricted thereto, but can be modified in many different ways.

Claims

Patent claims: 1. Gate driver (100) for controlling a power switch, in particular a special bipolar transistor with an insulated gate electrode, IGBT, or a power MOSFET, with a high-side system (20) and a low-side system (10), wherein in the high-side system (20) a high-side switch (12), a high-side diode (14) and a low-side switch (22), a low-side diode (24) are provided in the low-side system (10), wherein the high-side switch (12) is connected to the high-side diode (14) and the low-side switch (22) is connected to the low-side diode (24), the high-side switch (12) and high-side diode (14 ) and the interconnected lowside switch (22) and lowside diode (24) are connected to a phase connection (8) of the circuit breaker, and wherein the lowside system (10) has a measuring device (4) for measuring a voltage has, which is connected to the anode at least one intermediate diode (2), the cathode of which is also connected to the gate supply voltage ung (6) of the high-side circuit breaker is connected. 2. Gate driver according to claim 1, wherein the at least one intermediate diode (2) are two intermediate diodes (2, 2a, 2b), the cathodes of which are connected to the two potentials of the gate supply voltage in the high-side system of the power switch and their anodes are connected to the inputs of a differential amplifier, and that the output of the differential amplifier is connected to the measuring device. 3. Gate driver according to claim 1 or 2, wherein a level shifter (18) is arranged between the cathode of the at least one intermediate diode (2) and the voltage to be measured in the high-side system (6). 4. Gate driver according to one of the preceding claims, wherein the differential amplifier (16) has a peak value rectifier (26) which is arranged between the output of the differential amplifier (16) and the measuring device (4). 5. Gate driver according to one of the preceding claims, wherein the high-side switch (12) and the low-side switch (22) are each an IGBT or MOSFET. 6. Gate driver according to claim 5, wherein the anode of the high-side diode (14) with the source connection of the MOSFET as the high-side switch (12) or the emitter connection of the IGBT as the high-side switch (12) verbun is the, and the cathode of the high-side diode (14) is connected to the drain connection of the MOSFET as the high-side switch (12) or the collector connection of the IGBT as the high-side switch (12). 7. Gate driver according to claim 5 or 6, wherein the anode of the lowside diode (24) with the source connection of the MOSFET as the low side switch (22) or the emitter connection of the IGBT as the low side switch ( 22) is connected, and the cathode of the lowside diode (24) is connected to the drain terminal of the MOSFET as the lowside switch (22) or the collector terminal of the IGBT as the lowside switch (22) . 8. Gate driver according to one of the preceding claims, wherein the high-side diode (14) is a body diode of the high-side switch (12), and wherein the low-side diode (24) is a body-diode of the low-side switch ( 22) is. 9. Gate driver according to one of the preceding claims, wherein the measuring device (4) is an analog-digital converter. 10. Gate driver according to one of claims 1 to 3 and 5 to 9, wherein between tween the output of the differential amplifier (16) and the measuring device (4), a microcontroller is arranged, which is set up to output signals of the differential amplifier (16) to be sampled at a point in time.