Drive circuit and switching regulator comprising the same

Abstract

A drive circuit drives a switch element having a first terminal, a second terminal, and a control terminal. A direct-current voltage is applied to the first terminal. The drive circuit includes a capacitor which is charged when the switch element is in the OFF state, and applies a charged voltage between the control terminal and the first terminal of the switch element or between the control terminal and the second terminal of the switch element when the switch element is in the ON state.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a diagram illustrating a circuit configuration of a drive circuit according to a first embodiment of the present invention and a switching regulator including the drive circuit.

FIG. 1B is a timing diagram illustrating operating waveforms of the switching regulator of the first embodiment of the present invention.

FIG. 2 is a diagram illustrating a circuit configuration of a drive circuit according to a second embodiment of the present invention and a switching regulator including the drive circuit.

FIG. 3A is a diagram illustrating a circuit configuration of a drive circuit according to a third embodiment of the present invention and a switching regulator including the drive circuit.

FIG. 3B is a timing diagram illustrating operating waveforms of the switching regulator of the third embodiment of the present invention.

FIG. 4 is a circuit diagram illustrating a variation of the switching regulator of the second embodiment of the present invention.

FIG. 5A is a diagram illustrating a circuit configuration of a drive circuit according to a first conventional example and a switching regulator including the drive circuit.

FIG. 5B is a timing diagram illustrating operating waveforms of the switching regulator of the first conventional example.

FIG. 6 is a diagram illustrating a circuit configuration of a drive circuit according to a second conventional example and a switching regulator including the drive circuit.

Claims

1. A drive circuit for driving a switch element having a first terminal, a second terminal, and a control terminal, wherein a direct-current voltage is applied to the first terminal, the drive circuit comprising: a capacitor which is charged when the switch element is in the OFF state, and applies a charged voltage between the control terminal and the first terminal of the switch element or between the control terminal and the second terminal of the switch element when the switch element is in the ON state.

2. The drive circuit of claim 1, further comprising: a direct-current power supply;a first switch which is connected between a positive terminal of the capacitor and a positive terminal of the direct-current power supply, and goes to the ON state when the switch element is turned OFF;a second switch which is connected between a negative terminal of the capacitor and a negative terminal of the direct-current power supply, and goes to the ON state when the switch element is turned OFF;a third switch which is connected between the positive terminal of the capacitor and the control terminal of the switch element, and goes to the ON state when the switch element is turned ON; anda fourth switch which is connected to the negative terminal of the capacitor and the second terminal of the switch element, and goes to the ON state when the switch element is turned ON.

3. The drive circuit of claim 2, wherein the first switch is a diode having a cathode connected to the positive terminal of the capacitor.

4. The drive circuit of claim 2, wherein, when the first switch is in the ON state, the third switch is in the OFF state, and when the third switch is in the ON state, the first switch is in the OFF state.

5. The drive circuit of claim 2, wherein, when the second switch is in the ON state, the fourth switch is in the OFF state, and when the fourth switch is in the ON state, the second switch is in the OFF state.

6. The drive circuit of claim 1, further comprising: a direct-current power supply;a first switch which is connected between a positive terminal of the capacitor and a positive terminal of the direct-current power supply, and goes to the ON state when the switch element is turned OFF;a second switch which is connected between a negative terminal of the capacitor and a negative terminal of the direct-current power supply, and goes to the ON state when the switch element is turned OFF;a third switch which is connected between the positive terminal of the capacitor and the control terminal of the switch element, and goes to the ON state when the switch element is turned ON; anda fourth switch which is connected to the negative terminal of the capacitor and the first terminal of the switch element, and goes to the ON state when the switch element is turned ON.

7. The drive circuit of claim 6, wherein the first switch is a diode having a cathode connected to the positive terminal of the capacitor.

8. The drive circuit of claim 6, wherein, when the first switch is in the ON state, the third switch is in the OFF state, and when the third switch is in the ON state, the first switch is in the OFF state.

9. The drive circuit of claim 6, wherein, when the second switch is in the ON state, the fourth switch is in the OFF state, and when the fourth switch is in the ON state, the second switch is in the OFF state.

10. The drive circuit of claim 1, wherein the switch element is an N-channel FET.

11. A switching regulator comprising: a drive circuit;a switch element driven by the drive circuit;an input direct-current power supply for applying a direct-current voltage to a first terminal of the switch element; andan inductor connected to a second terminal of the switch element, for repeatedly performing accumulation and discharge of energy by an ON/OFF operation of the switch element,wherein the drive circuit drives the switch element having the first terminal, the second terminal, and a control terminal, wherein a direct-current voltage is applied to the first terminal,the drive circuit has a capacitor which is charged when the switch element is in the OFF state, and applies a charged voltage between the control terminal and the first terminal of the switch element or between the control terminal and the second terminal of the switch element when the switch element is in the ON state, andthe drive circuit rectifies and smoothes a voltage occurring in the inductor to generate a direct-current output voltage.