CN111669031A - Switching power supply main power tube drive circuit - Google Patents

Abstract

The present invention provides a driving circuit for a main power tube of a switching power supply. The main power tube is a PMOS tube. The driving circuit includes a pull-down circuit and a clamping circuit. The first end of the pull-down circuit is connected to the control end of the power tube. The second end is grounded, and the power tube is fully turned on by controlling the pull-down circuit to be turned on; the first end of the clamping circuit receives the supply voltage, and the second end is connected to the control end of the power tube, and the When the clamping circuit is turned on, the voltage of the control terminal of the power tube is clamped to a desired voltage. The invention can drive the power tube quickly and has high working efficiency.

Description

Switching power supply main power tube drive circuit

technical field

The invention relates to the field of power electronics, in particular to a main power tube driving circuit of a switching power supply.

Background technique

In the prior art, a PMOS transistor is often used as the main power transistor of the switching power supply. 1 illustrates the drive circuit of the PMOS main power transistor in the prior art. In the prior art, the main power transistor is turned on by controlling the switch M1 to be turned on, and the main power transistor is turned off by controlling the switch M2 to be turned on. However, only by pulling down the main power tube of the switch tube M1, the conduction speed of the main power tube is not fast enough; secondly, the main power tube cannot be controlled to be fully turned on.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a switching power supply main power tube driving circuit capable of driving power tubes with high efficiency and speed, so as to solve the problems existing in the prior art that the conduction speed of the power tubes is not fast enough and cannot be fully turned on.

In order to achieve the above purpose, the present invention provides a switching power supply main power tube driving circuit, the main power tube is a PMOS tube, and it is characterized in that: the driving circuit includes a pull-down circuit and a clamping circuit, and the pull-down circuit is the first. The terminal is connected to the control terminal of the power tube, the second terminal of which is grounded, and the pull-down circuit is controlled to be turned on to drive the power tube to be fully turned on; the first terminal of the clamping circuit receives the supply voltage, and the second terminal of the clamping circuit receives the power supply voltage. The control terminal of the power tube is connected; when the main power tube is fully turned on, the clamping circuit is turned on, and the clamping circuit clamps the voltage of the control terminal of the power tube to a desired voltage.

Optionally, the pull-down circuit includes a first switch tube and a second switch tube, the first end of the first switch tube is connected to the control end of the power tube, and the second end of the first switch tube is grounded; the second switch tube first The terminal is connected to the control terminal of the main power tube, and the second terminal is grounded; the power tube is fully turned on by controlling the conduction of the first switch tube and the second switch tube.

Optionally, after the clamping circuit is turned on, the second switch tube is controlled to be turned off.

Optionally, the drive circuit further includes a third switch tube, the first end of the third switch tube receives the supply voltage, and the second end of the third switch tube is connected to the control end of the power tube; by controlling the The third switch tube is turned on to control the power tube to be turned off.

Optionally, the drive circuit further includes a first resistor, a first current source and a fourth switch tube, the first end of the first resistor receives the supply voltage, and the second end of the first resistor is connected to the control end of the main power tube; A current source and the fourth switch tube are connected in series and then connected to the control terminal of the power tube; when the main power tube is turned on, the first current source and the fourth switch tube are turned on.

Compared with the prior art, the present invention has the following advantages: the driving circuit includes a pull-down circuit and a clamping circuit, the first end of the pull-down circuit is connected to the control end of the power tube, and the second end of the pull-down circuit is grounded. turn on to drive the power tube to be fully turned on; the first end of the clamp circuit receives the supply voltage, and the second end of the clamp circuit is connected to the control end of the power tube, when the clamp circuit is turned on, the power The tube control terminal voltage is clamped at the desired voltage. The invention can drive the power tube quickly and has high working efficiency.

Description of drawings

1 is a schematic diagram of a main power tube drive circuit of a switching power supply in the prior art;

FIG. 2 is a schematic diagram of the main power tube driving circuit of the switching power supply of the present invention;

Detailed ways

The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, but the present invention is not limited to these embodiments. The present invention covers any alternatives, modifications, equivalent methods and arrangements made within the spirit and scope of the present invention.

In order to give the public a thorough understanding of the present invention, specific details are described in detail in the following preferred embodiments of the present invention, and those skilled in the art can fully understand the present invention without the description of these details.

The invention is described in more detail by way of example in the following paragraphs with reference to the accompanying drawings. It should be noted that, the accompanying drawings are all in a relatively simplified form and in an inaccurate scale, so as to facilitate and clearly assist in explaining the purpose of the embodiments of the present invention.

As shown in FIG. 2, a schematic diagram of an embodiment of the main power tube driving circuit of the switching power supply of the present invention is shown. The main power tube of the present invention is a PMOS tube, and the driving circuit includes a pull-down circuit, a clamping circuit, and a switch tube M4 and a switch tube M3. , a first current source I1 and a first resistor R1. The pull-down circuit includes a PMOS transistor M1 and an NMOS transistor M2. The source of the PMOS transistor M1 is connected to the main power transistor control terminal, and its drain is grounded; the drain of the NMOS transistor M2 is connected to the main power transistor control terminal, and its source is grounded. By driving the M1 tube and the M2 tube to be turned on, the main power tube is fully turned on. The switch tube M3 and the current source I1 are connected in series to the control terminal of the main power tube. The current source I1 and the M3 tube are always on when the main power tube is turned on, and the voltage I1*R1 on the first resistor R1 maintains the gate source of the main power tube. voltage VGS. In order to ensure that the lowest level of the main power tube after being pulled down is controlled, the clamp circuit is connected to the control end of the main power tube, the first end of the clamp circuit receives the supply voltage, and the second end of the clamp circuit is connected to the control end of the power tube , when the clamping circuit is turned on, the voltage of the control terminal of the power tube is clamped to a desired voltage, and an enable signal EN is output to control the second switch tube to be turned off. After the main power transistor is turned on, the enable signal EN controls the NMOS transistor M2 to be turned off. The first end of the switch tube M4 receives the input voltage, and the second end of the switch tube M4 is connected to the control end of the main power tube, and the main power tube is driven to turn off by pulling down the switch tube M4.

Although the embodiments are described and described separately above, some common technologies are involved, and in the opinion of those of ordinary skill in the art, they can be replaced and integrated between the embodiments. Reference is made to another example described.

The above-mentioned embodiments do not constitute a limitation on the protection scope of the technical solution. Any modifications, equivalent replacements and improvements made within the spirit and principles of the above-mentioned embodiments shall be included within the protection scope of this technical solution.

Claims (5)

1. The utility model provides a switching power supply main power tube drive circuit, the main power tube is the PMOS pipe, its characterized in that: the driving circuit comprises a pull-down circuit and a clamping circuit, wherein the first end of the pull-down circuit is connected with the control end of the power tube, the second end of the pull-down circuit is grounded, and the pull-down circuit is controlled to be conducted so as to drive the power tube to be conducted fully; the first end of the clamping circuit receives a power supply voltage, and the second end of the clamping circuit is connected with the control end of the power tube; when the main power tube is sufficiently conducted, the clamping circuit is conducted, and the clamping circuit clamps the voltage at the control end of the power tube at a desired voltage.

2. The main power transistor driving circuit of claim 1, wherein: the pull-down circuit comprises a first switch tube and a second switch tube, wherein the first end of the first switch tube is connected with the control end of the power tube, and the second end of the first switch tube is grounded; the first end of the second switch tube is connected with the control end of the main power tube, and the second end of the second switch tube is grounded; the first switch tube and the second switch tube are controlled to be conducted to drive the power tube to be sufficiently conducted.

3. The main power transistor driving circuit of claim 2, wherein: and after the clamping circuit is switched on, the second switching tube is controlled to be switched off.

4. The switching power supply main power tube driving circuit according to claim 3, wherein: the driving circuit further comprises a third switching tube, wherein a first end of the third switching tube receives power supply voltage, and a second end of the third switching tube is connected with a control end of the power tube; and the power tube is controlled to be switched off by controlling the third switching tube to be switched on.

5. The switching power supply main power tube driving circuit according to claim 4, wherein: the driving circuit further comprises a first resistor, a first current source and a fourth switching tube, wherein the first end of the first resistor receives a power supply voltage, and the second end of the first resistor is connected with the control end of the main power tube; the first current source and the fourth switch tube are connected in series and then connected with the control end of the power tube; and in the conduction stage of the main power tube, the first current source is conducted with the fourth switch tube.

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