JPH04114232U - Gate drive circuit for insulated gate voltage-driven semiconductor devices - Google Patents

Abstract

(57) [Summary] [Purpose] When driving the gate of an insulated gate voltage-driven semiconductor device via a pulse transformer with a pulse voltage whose duty ratio varies, a gate voltage that can supply sufficient gate voltage for driving is provided. Provides a drive circuit. [Structure] A capacitor 5 is connected in series between one end of the secondary winding of a pulse transformer 2 whose primary winding is supplied with a pulse voltage, and the gate of a MOS-FET 4 and one end of a resistor 3. A diode 6 with its cathode facing the gate side of the MOS-FET 4 is connected in parallel to the resistor 3.

Description

[Detailed explanation of the idea]

0001

[Industrial application field]

The present invention is an insulated gate voltage-driven semiconductor device in which the gate is insulated from other electrodes. This invention relates to a gate drive circuit.

0002

[Conventional technology]

Conventionally, for example, in MOS-FET, the gate was insulated from other electrodes and the When driving a voltage-driven semiconductor element with a pulse voltage, the circuit structure is relatively simple. A game using a pulse transformer as shown in Fig. 3 is recommended because it is easy and inexpensive to construct. A drive circuit is used. In this circuit, the pulse voltage source 1 is used as shown in FIG. 4(a). When a pulse voltage V1 with a waveform like this is input to the primary side of pulse transformer 2, A voltage signal V2 with a pulse waveform as shown in Fig. 4(b) is output to the secondary side. . This voltage waveform on the secondary side becomes the gate voltage Vgs of the MOS-FET 4 as it is. A resistor 3 connected in parallel between the gate and source turns on the gate of the MOS-FET 4. This is to discharge the gate charge that has been charged at the time of the gate when the gate is turned off.

0003

[Problem that the idea aims to solve]

In the gate drive circuit as described above, the pulse input to the primary side of the pulse transformer 2 is Since the DC component of the pulse voltage waveform is not transmitted to the secondary side, the pulse output to the secondary side is The average potential of the voltage waveform is always 0V. For this reason, the duty ratio changes When pulse voltage waveform V1 is input to the primary side of pulse transformer 2, it is output to the secondary side. The positive and negative peak voltages of the voltage waveform V2 shown in Fig. 4(b) change greatly. It will move. Therefore, for the gate of MOS-FET4, the input voltage wave Overvoltage margin at minimum duty ratio and maximum duty ratio of It is necessary to consider the margin for the threshold voltage, and also the duty ratio. Regardless of what happens, you must make sure to provide a gate voltage that allows sufficient drive. There was a problem that there was no.

0004 The purpose of this invention is to generate pulses with waveforms whose amplitude is approximately constant and whose duty ratio varies. Voltage drives the gate of an insulated gate voltage-driven semiconductor device via a pulse transformer A gate driver that is easy to configure and can supply a sufficient gate voltage when The objective is to provide a dynamic circuit.

[0005]

[Means to solve the problem]

In order to solve the above problems, the gate drive circuit of the present invention is shown in FIG. 1 of the embodiment. A resistor is connected in parallel between the gate and source of the insulated gate voltage driven semiconductor element 4 so that Connect resistor 3 and the secondary winding of pulse transformer 2, respectively, and In the gate drive circuit that supplies pulse voltage from pulse voltage source 1 to the next winding, One end of the secondary winding of the transformer 2 and the gate of the semiconductor element 4 and one end of the resistor 3 The cathode is directed toward the capacitor 5 connected in series between them and the gate of the semiconductor element 4. In this way, a DC regeneration circuit consisting of a diode 6 connected in parallel to a resistor 3 is provided. Prepare.

[0006]

[Effect]

In the above gate drive circuit of the present invention, the amplitude is on the primary side of the pulse transformer 2. When a pulse voltage that is almost constant and whose duty ratio changes variously is input, the secondary side outputs an AC voltage with a large peak voltage fluctuation, whereas the capacitor 5 The DC component of the primary side input voltage waveform is regenerated by the action of the diode 6 and the secondary side A drive circuit output with a waveform superimposed on the side output is obtained. This allows the pulse tran Fluctuations in the peak voltage at the secondary side output of the device 2 are suppressed, and A gate voltage that enables sufficient driving is supplied.

[0007]

【Example】

Embodiments of the present invention will be described below with reference to the drawings. In Figure 1, 5 is a pulse One end of the secondary winding of transformer 2, the gate and resistor of MOS-FET 4 to be driven A capacitor is connected in series with one end of 3, and 6 is the gate side of MOS-FET4. The cathode is connected to the resistor 3, and the anode is connected to the source side, and the resistor 3 is connected in parallel. It is a diode. DC component is regenerated by these capacitor 5 and diode 6 It constitutes a circuit.

[0008] In the drive circuit configured as above, the pulse voltage source 1 is connected to the pulse transformer 2. When a pulse voltage V1 with the waveform shown in Fig. 2 (a) is input to the primary side of the A pulse voltage V2 having a waveform having positive and negative polarities shown in 2(b) is output. When this pulse voltage V2 is a negative voltage, the diode 6 becomes conductive and the capacitor 5 It will be charged. At this time, the gate charge of MOS-FET4 is discharged through resistor 3. The gate is turned off. Then, the pulse voltage V2 in FIG. 2(b) is a positive voltage. When , the charging voltage of capacitor 5 is superimposed on this positive voltage, and the level becomes positive. As a result, the pulse voltage Vgs has a waveform shown in FIG. 2(c). That is, the voltage V2 Even if the DC component of voltage V1 is lost, voltage Vgs is clamped at the lowest voltage of almost 0 voltage. The DC component where the voltage is removed becomes the regenerated voltage. Such a pulse voltage Vgs is MO Since it is input to the gate of S-FET 4, sufficient gate drive is performed. Figure 2 T1 is the gate on time and T2 is the gate off time.

[0009] Generally, the maximum rating of the gate-source voltage of MOS-FET4 is Vgs<±20 It is about V. Now, assuming that the gate voltage Vgs threshold is 7V, the overvoltage margin is When designed with 5V, the maximum value of the gate-source voltage is 15V. above Under the conditions, when the duty ratio of the pulse voltage waveform is 50%, the conventional drive In the active circuit, the gate voltage Vgs is 7.5V, with a 0.5V master to the threshold. - I can only take gin. On the other hand, in the drive circuit of this embodiment, the duty ratio is Even in the case of 50%, the gate voltage Vgs can be maintained at approximately 14V, so the threshold voltage There is a margin of 7V.

0010

[Effect of the idea]

As described above, the drive circuit of the present invention uses a pulse voltage source via a pulse transformer. In a circuit that drives the gate of an insulated gate voltage-driven semiconductor device, a pulse Connected between one end of the secondary winding of the transformer and the gate of the semiconductor element and one end of the resistor. A capacitor connected in parallel with a resistor with the cathode facing the gate side of the semiconductor element. A DC regeneration circuit consisting of a diode is installed, so the primary side of the pulse transformer is A pulse voltage whose amplitude is approximately constant and whose duty ratio varies is input, and the secondary side Even when an AC voltage with a peak voltage that fluctuates widely is output, capacitors and The DC component of the primary side input voltage waveform is regenerated by the action of the diode and becomes the secondary side output voltage. A drive circuit output with a superimposed waveform can be obtained. Therefore, with a simple configuration, It is possible to suppress fluctuations in the peak voltage of the secondary output of the transformer, and It is possible to supply a gate voltage that can drive the child gate sufficiently and well.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of an embodiment of the present invention.

2A to 2C are waveform diagrams illustrating the operation of the embodiment of FIG. 1;

FIG. 3 is a circuit diagram showing an example of a conventional drive circuit.

FIGS. 4(a) and 4(b) are waveform diagrams illustrating the operation of a conventional drive circuit.

[Explanation of symbols]

1 Pulse voltage source 2 Pulse transformer 3 Resistor 4 Insulated gate voltage driven semiconductor element (MOS-FE
T) 5 Capacitor 6 Diode

Claims (1)

[Scope of utility model registration request] 1. A resistor and a secondary winding of a pulse transformer are connected in parallel between the gate and source of an insulated gate voltage driven semiconductor element, and a pulse voltage is applied to the primary winding of the pulse transformer from a pulse voltage source. a capacitor connected in series between one end of the secondary winding of the pulse transformer, the gate of the semiconductor element, and one end of the resistor, and a cathode directed toward the gate of the semiconductor element. A gate drive circuit for an insulated gate voltage-driven semiconductor device, comprising a DC regeneration circuit comprising a diode connected in parallel to the resistor.