KR102410531B1 - Gate driving circuit - Google Patents

Abstract

The gate driving circuit includes a driving signal input unit, a cut-off voltage supply unit, a conduction voltage supply unit, a saturation voltage supply unit, and a driving voltage selection unit. The driving signal input unit selectively receives different first driving signals and second driving signals for driving the semiconductor switching device, the blocking voltage supply unit supplies a blocking voltage to cut off the semiconductor switching device, and the conduction voltage supply unit is the semiconductor A conduction voltage is supplied to cause the switching element to conduct, and the saturation voltage supply unit causes a saturation current to flow through the semiconductor switching element and supplies a saturation voltage having a magnitude between the cut-off voltage and the conduction voltage, and the driving voltage selector provides a cut-off voltage according to the driving signal. , the conduction voltage and the saturation voltage are selectively provided to the gate terminal of the semiconductor switching device.

Description

gate driving circuit {GATE DRIVING CIRCUIT}

The present invention relates to a circuit related to a power semiconductor device, and more particularly, to a gate driving circuit of a switching device such as an IGBT and a MOSFET.

In general, the greater the slope of the gate signal of the power semiconductor device, the faster the power semiconductor device enters the saturation region, so that the switching loss is small. However, a large slope of the gate signal causes noise and gate voltage surge, which increases EMI, cross talk, and may damage power semiconductor devices with low gate withstand voltage, such as SiC MOSFETs.

For this reason, in a conventional gate driver, the slope of the gate signal is gently adjusted and used. However, there is a problem in that the switching loss of the power device increases because a resistor is added to the gate terminal for this purpose.

KR 1020190007814 A KR 102160135224 A

The present invention has been devised to solve the problems of the related art, and an object of the present invention is to provide a gate driver for supplying a stable gate driving voltage while reducing switching loss of a power semiconductor device.

In order to achieve the above object, a gate driving circuit according to the present invention includes a driving signal input unit, a cut-off voltage supply unit, a conduction voltage supply unit, a saturation voltage supply unit, and a driving voltage selection unit.

The driving signal input unit selectively receives different first driving signals and second driving signals for driving the semiconductor switching device, the blocking voltage supply unit supplies a blocking voltage to cut off the semiconductor switching device, and the conduction voltage supply unit is the semiconductor A conduction voltage is supplied to cause the switching element to conduct, and the saturation voltage supply unit causes a saturation current to flow through the semiconductor switching element and supplies a saturation voltage having a magnitude between the cut-off voltage and the conduction voltage, and the driving voltage selector provides a cut-off voltage according to the driving signal. , the conduction voltage and the saturation voltage are selectively provided to the gate terminal of the semiconductor switching device.

According to this configuration, it is possible to reduce the switching loss by using a smaller gate resistance compared to the conventional two-level gate driving circuit. In addition, by moving the semiconductor switching element from the cut-off state to the conduction state through a separate intermediate state using a two-level input signal as in the prior art, a more stable gate driving voltage can be supplied even with a simple structure.

In this case, the driving voltage selector includes a first selector and a second selector each complementary to the first driving signal and the second driving signal, and a third selector operated with a preset time delay for the second driving signal. may include wealth.

In addition, a first resistor, a second resistor, and a third resistor having one end commonly connected to the gate of the semiconductor switching device and the other end connected to the first selector, the second selector, and the third selector, respectively, are further added. may include

In addition, the first selector and the second selector each include a first transistor and a second transistor that are bipolar junction transistors complementary to the same driving signal, and the base terminal of the first transistor and the second transistor is a driving signal. It may be commonly connected to the input unit, the collector terminal may be connected to the first resistor and the second resistor, respectively, and the emitter terminal may be connected to the cutoff voltage supply unit and the saturation voltage supply unit, respectively.

In addition, the third selection unit may further include a third transistor having a drain terminal connected to a conduction voltage supply unit and a source terminal connected to a third resistor, and a signal delay element delaying the gate driving signal and supplying it to the gate terminal of the third transistor. can

Also, the first transistor may be an NPN BJT, the second transistor may be a PNP BJT, and the third transistor may be an N-channel MOSFET, and a signal inverting element may be commonly connected to the base terminals of the first transistor and the second transistor.

According to the present invention, it is possible to reduce the switching loss by using a smaller gate resistance compared to the conventional two-level gate driving circuit.

In addition, by moving the semiconductor switching element from the cut-off state to the conduction state through a separate intermediate state using a two-level input signal as in the prior art, a more stable gate driving voltage can be supplied even with a simple structure.

1 is a schematic block diagram of a gate driving circuit according to an embodiment of the present invention;
Fig. 2 is a circuit diagram showing an actual implementation example of Fig. 1;
3 and 4 are diagrams illustrating a voltage and power loss between a gate source and a gate source of a semiconductor switching device according to the related art when the gate resistance is low, respectively.
5 and 6 are diagrams illustrating a voltage and power loss between a gate source and a gate source of a semiconductor switching device according to the related art when the gate resistance is high, respectively.
7 and 8 are diagrams showing voltage and power loss between gate sources of the semiconductor switching device according to the present invention when the gate resistance is low, respectively.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

1 is a schematic block diagram of a gate driving circuit according to an embodiment of the present invention, and FIG. 2 is a circuit diagram illustrating an actual implementation example of FIG. 1 . In FIG. 1 , the gate driving circuit 100 includes a driving signal input unit 110 , a cut-off voltage supply unit 120 , a saturation voltage supply unit 130 , a conduction voltage supply unit 140 , and a driving voltage select unit 150 , and a gate. It includes a resistor 160 .

The driving voltage selector 150 again includes a first selector 152 , a second selector 154 , and a third selector 156 , and the gate resistor 160 includes a first resistor 162 . ), a second resistor 164 , and a third resistor 166 .

The driving signal input unit 110 selectively receives different first and second driving signals for driving the semiconductor switching device. The first driving signal is an off signal, the second driving signal is an on signal, and the driving signal input unit 110 receives two-level signals as in the prior art.

The cut-off voltage supply unit 120 supplies a cut-off voltage for shutting off the semiconductor switching element, and the conduction voltage supply unit 140 supplies a conduction voltage for the semiconductor switching element to conduct. In FIG. 2, the cut-off voltage is -5V, conduction. It can be seen that the voltage is set to 20V.

The saturation voltage supply unit 130 allows a saturation current to flow through the semiconductor switching device and supplies a saturation voltage having a magnitude between the cut-off voltage and the conduction voltage. The magnitude of the saturation voltage must be large enough to allow a saturation current to flow through the MOSFET, but the MOSFET must not transition to a conducting state. Therefore, the saturation voltage may be preset by these restrictions, and it can be seen that it is set to 15V in FIG. 2 .

The driving voltage selector 150 selectively provides a cut-off voltage, a conduction voltage, and a saturation voltage to the gate terminal of the semiconductor switching device according to the driving signal. More specifically, a typical voltage source gate driver is a two-level gate driver.

One level charges the gate of the power transistor to a positive voltage value, bringing the transistor into conduction (con). The other levels are zero or negative, which puts the transistor in the shut-off state (bl). The gate driver proposed in the present invention has a third level for changing the transistor into a saturated state (sat), and this is implemented using a two-level driving signal.

The driving voltage selector 150 includes a first selector 152 and a second selector 154 that complementarily operate with respect to the first and second driving signals, respectively, and preset values for the second driving signal. and a third selection unit 156 that operates with a time delay.

In addition, a first resistor ( ) having one end commonly connected to the gate of the semiconductor switching device and the other end connected to the first selector 152 , the second selector 154 , and the third selector 156 , respectively. 162 ), a second resistor 164 , and a third resistor 166 . As such, the gate driver is connected to the power MOSFET through one gate resistor for each level. Therefore, the switching speed for each transition can be adjusted individually.

The first selector 152 and the second selector 154 include a first transistor and a second transistor that are bipolar junction transistors complementary to the same driving signal, and the first and second transistors 152 and 154 are provided. The transistor 154 has a base terminal commonly connected to the driving signal input unit 110 , a collector terminal connected to a first resistor 162 and a second resistor 164 , respectively, and an emitter terminal connected to a cut-off voltage supply unit 120 , respectively. and the saturation voltage supply unit 130 , respectively.

The third selector 156 delays the third transistor element 156-2 having a drain terminal connected to the conduction voltage supply unit 140 and a source terminal connected to the third resistor 166, and a gate driving signal to a third A signal delay element 156-4 supplied to the gate terminal of the transistor element 156-2 is further included.

In FIG. 2 , it can be seen that the first transistor 152 is an NPN BJT, and the second transistor 154 is implemented as a PNP BJT. This is because reverse current can flow when implemented as an FET. It can be seen that the third transistor 156 - 2 is an N-channel MOSFET, and the signal inverting element 153 is commonly connected to the base terminals of the first transistor 152 and the second transistor 154 .

3 and 4 are diagrams illustrating voltage and power loss between gate sources of a semiconductor switching device according to the related art when the gate resistance is low, respectively. In FIG. 3 , it can be seen that the surge of the gate signal occurs in the case of a low gate resistance (8Ω).

5 and 6 are diagrams illustrating voltage and power loss between gate sources of a semiconductor switching device according to the related art when the gate resistance is high, respectively. 6 , it can be seen that a large power loss occurs in the case of a high gate resistance (100Ω).

7 and 8 are diagrams illustrating voltage and power loss between gate sources of the semiconductor switching device according to the present invention when the gate resistance is low, respectively. In FIG. 7 , it can be seen that the gate signal is stable even though a low gate resistance (8Ω) is employed, and the power loss is small due to the low gate resistance.

As described above, according to the present invention, it is possible to reduce the switching loss by using a smaller gate resistance compared to the conventional two-level gate driving circuit. In addition, by moving the semiconductor switching element from the cut-off state to the conduction state through a separate intermediate state using a two-level input signal as in the prior art, a more stable gate driving voltage can be supplied even with a simple structure.

In summary, the present invention proposes a three-level gate driver capable of reducing the surge of the gate signal while using a small gate resistance to reduce the switching loss. It consists of two BJTs, one MOSFET, and three resistors for controlling the transient state of each device to make the voltage level of the gate driving signal in three stages (conduction, saturation, cutoff).

The present invention is to supply a stable gate driving voltage while reducing switching loss of a power semiconductor device, and is particularly suitable for power semiconductor devices with low gate withstand voltage such as SiC MOSFETs, and has a smaller gate resistance compared to a conventional two-level gate driving circuit. can be used to reduce switching losses.

Although the present invention has been described with reference to some preferred embodiments, the scope of the present invention should not be limited thereto, but should also extend to modifications or improvements of the above embodiments supported by the claims.

100: gate driving circuit
110: drive signal input unit
120: cut-off voltage supply
130: saturation voltage supply
140: conduction voltage supply unit
150: drive voltage selection unit
152: first selection unit, first transistor
153: signal inverting element
154: second selection unit, second transistor
156: third selection unit
156-2: third transistor
156-4: signal delay element
160: gate resistor unit
162: first resistor
164: second resistor
166: third resistance

Claims (6)

a driving signal input unit for selectively receiving different first and second driving signals for driving the semiconductor switching device;
a cut-off voltage supply unit supplying a cut-off voltage for shutting off the semiconductor switching device;
a conduction voltage supply unit supplying a conduction voltage for causing the semiconductor switching element to conduct;
a saturation voltage supply unit for allowing a saturation current to flow through the semiconductor switching element and supplying a saturation voltage having a magnitude between the cut-off voltage and the conduction voltage; and
A gate driving circuit comprising a driving voltage selector that selectively provides the cut-off voltage, the conduction voltage, and the saturation voltage to a gate terminal of the semiconductor switching device according to the driving signal,
The driving voltage selector may include: a first selector and a second selector each complementary to the first and second driving signals; and a third selector operating with a preset time delay with respect to the second driving signal,
A first resistor, a second resistor, and a third resistor have one end commonly connected to the gate of the semiconductor switching device and the other end connected to the first selector, the second selector, and the third selector, respectively further comprising,
The first selector and the second selector each include a first transistor and a second transistor that are bipolar junction transistors complementary to the same driving signal, wherein the first transistor and the second transistor have a base terminal. is commonly connected to the driving signal input unit, a collector terminal is connected to the first resistor and the second resistor, respectively, and an emitter terminal is connected to the cut-off voltage supply unit and the saturation voltage supply unit, respectively;
The third selection unit may include: a third transistor having a drain terminal connected to the conduction voltage supply unit and a source terminal connected to the third resistor; and a signal delay element delaying the driving signal and supplying it to the gate terminal of the third transistor,
wherein the first transistor is an NPN BJT, the second transistor is a PNP BJT, the third transistor is an N-channel MOSFET, and a signal inverting element is commonly connected to the base terminals of the first transistor and the second transistor. gate driving circuit.
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