JPH065221U - Power MOSFET drive circuit - Google Patents

Abstract

(57) [Summary] [Object] To provide a highly reliable power MOSFET drive circuit in which the power MOSFET is not destroyed even if the power supply voltage fluctuates. [Structure] MOS of drive stage of power MOSFET Q40
The constant voltage circuit 3 is provided between the FET Q10 and the power supply Vcc.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a drive circuit for a power MOSFET.

[0002]

[Prior art]

 Generally, as a drive circuit of a power MOSFET, there is a totem pole type or push-pull type circuit, and a power supply voltage is directly applied to the gate of the power MOSFET through a gate resistor by a transistor or a MOSFET, respectively.

FIGS. 5 and 6 are examples of totem pole type and push-pull type circuits, respectively. In FIG. 5, 10 is a semiconductor element which is a drive circuit of a power MOSFET, and 20 is a control element in the semiconductor element 10. Circuit parts, Q10, Q20, and Q30 are MOSFETs of the power MOSFET driving stage in the semiconductor element 10, R10 and R20 are resistors, Q40 is a power MOSFET, Vcc is a power supply, and ZD10 is a Zener diode for protection described later. .

Further, in FIG. 6, 10 ′ is a semiconductor element which is a drive circuit of a power MOSFET, 20 ′ is a control circuit section in the semiconductor element 10 ′, Q 50 and Q 60 are transistors of the power MOSFET drive stage, and R 20 ′ is A resistor, Q70 is a power MOSFET, and ZD10 is a Zener diode for protection described later.

[0005]

[Problems to be solved by the device]

 By the way, the drive circuit of the power MOSFET having the above-mentioned configuration has the following problems.

That is, since the power supply voltage Vcc is directly applied to the gate of the power MOSFET via the gate resistance, when the power supply voltage Vcc changes, the gate voltage V _{GS of the} power MOSFET also changes accordingly. On the other hand, the on-resistance R _DS of the power MOSFET may change, or a voltage exceeding the gate withstand voltage may be applied to destroy the power MOSFET.

A change in the on-resistance R _DS of the power MOSFET and a change in the gate voltage V _GS with respect to the change in the power supply voltage Vcc have characteristics as shown in FIGS. 7 and 8, respectively. In order to prevent the destruction of the power MOSFET due to such a change in the power supply voltage, it has conventionally been necessary to connect the Zener diode ZD10 as described above to the gate of the power MOSFET.

Therefore, an object of the present invention is to provide a highly reliable power MOS FET drive circuit in which the gate voltage and the on-resistance of the power MOSFET do not change with the fluctuation of the power supply voltage. To provide.

[0009]

[Means for Solving the Problems]

 In order to achieve the above-mentioned object, the present invention provides a power MOSFET drive circuit which is inserted between a power MOSFET and a power supply to drive the power MOSFET, wherein a constant voltage circuit is provided between the semiconductor element in the drive stage of the power MOSFET and the power supply. Is provided.

[0010]

[Action]

 In the drive circuit of the power MOSFET of the present invention, the constant voltage circuit is provided as described above, and the gate voltage is stabilized. Therefore, even if the power supply voltage fluctuates, the change of the on-resistance of the power MOS FET disappears and the gate is destroyed. Disappears.

Further, the Zener diode of the gate portion of the power MOSFET, which has been indispensable in the past, is unnecessary, and since the constant voltage circuit is intended only for the gate voltage, the area is small and the shape of the drive circuit is small. It is possible to stabilize the gate voltage without the problem of large size.

[0012]

【Example】

 An embodiment of the present invention will be described with reference to FIGS.

FIG. 1 and FIG. 2 are drive circuits for totem pole type and push-pull type power MOSFETs according to the present embodiment, respectively.

The same functional parts as those of the conventional example shown in FIGS. 5 and 6 are designated by the same symbols.

In a semiconductor element (hereinafter simply referred to as a drive circuit) 1 which is a totem pole type drive circuit in FIG. 1, a constant voltage circuit 3 is incorporated between a power supply voltage Vcc and a drive MOSFET Q10. Therefore, even if the power supply voltage Vcc changes, the voltage input to the control circuit 2 changes, but the gate voltage of the power MOSFET Q40 does not change, and the on-resistance does not change or the gate is not destroyed.

FIG. 3 and FIG. 4 show this, and the on-resistance R of the power MOSFET Q40 with respect to the power supply voltage Vcc, respectively._DSCharacteristics and gate voltage V_GSIt shows the characteristics of. As apparent from FIGS. 3 and 4, the on-resistance R of the power MOSFET Q40 is _DS And gate voltage V_DSIs constant regardless of fluctuations in the power supply voltage Vcc.

Further, since the gate voltage can be stabilized, the Zener diode ZD10 for protecting the gate portion of the power MOS FET 40, which has been indispensable in the past, is unnecessary, and the constant voltage conversion is intended only for the gate voltage. The area of the constant voltage circuit 3 in the drive circuit can be small, and the gate voltage can be stabilized without the problem that the shape of the drive circuit becomes large.

Further, in the push-pull type drive circuit 1'of FIG. 2, the constant voltage circuit 3'is incorporated between the power supply voltage Vcc and the driving transistor Q50. 2'is a control circuit. Also in this embodiment, the same effect as that of the totem pole type drive circuit of FIG. 1 can be obtained. As described above, according to the present embodiment, there is no change such that the shape is enlarged, and fluctuations in the power supply voltage are prevented. On the other hand, it is possible to realize a highly reliable power MOS FET drive circuit capable of supplying a stable gate voltage.

[0019]

[Effect of device]

 As described above, according to the present invention, it is possible to realize a highly reliable power MOSFET drive circuit capable of supplying a stable gate voltage without making a change in size.

[Brief description of drawings]

FIG. 1 is a totem pole type power MOSFET drive circuit according to an embodiment of the present invention.

FIG. 2 is a circuit diagram of a push-pull type power MOSFET driving circuit according to another embodiment of the present invention.

FIG. 3 is a characteristic diagram of a power supply voltage and an on-resistance in a power MOSFET drive circuit according to an embodiment of the present invention.

FIG. 4 is a characteristic diagram of a power supply voltage and a gate voltage in a power MOSFET drive circuit according to an embodiment of the present invention.

FIG. 5 is a totem pole type power MOS according to a conventional example.
It is a FET drive circuit diagram.

FIG. 6 is a push-pull type power MOSF according to a conventional example.
It is an ET drive circuit diagram.

FIG. 7 is a characteristic diagram of power supply voltage and on-resistance in a power MOSFET drive circuit according to a conventional example.

FIG. 8 is a characteristic diagram of a power supply voltage and a gate voltage in a power MOSFET drive circuit according to a conventional example.

[Explanation of symbols]

3,3 ′ constant voltage circuit Q40, Q70 power MOSFET Vcc power supply Q10, Q20, Q30 MOSFET (driving stage semiconductor element) Q50, Q60 transistor (driving stage semiconductor element)

Claims (1)

[Scope of utility model registration request] 1. A power MOSFET inserted between a power MOSFET and a power source to drive the power MOSFET.
In the T drive circuit, a constant voltage circuit is provided between the semiconductor element in the drive stage of the power MOSFET and the power supply, and the power MOSFET drive circuit.