SWITCHING POWER SUPPLY DEVICE

• US 20090174978A1
• Filed: 12/29/2008
• Published: 07/09/2009
• Est. Priority Date: 01/08/2008
• Status: Active Grant

• Current Assignee: Sanken Electric Company Limited
• Original Assignee: Sanken Electric Company Limited
• Inventors: NAKAMURA, Masaru
• Granted Patent: US 8,054,600 B2
• Time in Patent Office: Days
• US Class Current: 361/90
• CPC Class Codes: H02H 3/07 and with permanent disconnection after a predetermined number of reconnection cycles
• CPC Class Codes: H02H 7/1213 for DC-DC converters

Abstract

A switching power supply device includes: a switching element connected through a primary winding of a transformer to an output end of an input rectifying/smoothing circuit that rectifies and smoothes an alternating current input voltage and outputs a direct current input voltage; an output rectifying/smoothing circuit that rectifies and smoothes a voltage induced in a secondary winding of the transformer and outputs a direct current output voltage; and a control circuit that controls ON and OFF of the switching element. The control circuit includes an overvoltage protection circuit that detects a voltage corresponding to the direct current output voltage and a voltage corresponding to the alternating current input voltage, outputs an overvoltage operation prohibition signal for prohibiting ON and OFF operations of the switching element when the voltage corresponding to the direct current output voltage rises to a first threshold value or more, and releases the overvoltage operation prohibition signal when the alternating current input voltage drops and the voltage corresponding to the alternating current input voltage falls down below a second threshold value.

Claims

1. A switching power supply device, comprising:

an input rectifying/smoothing circuit that rectifies and smoothes an alternating current input voltage and outputs a direct current input voltage;

a switching element connected to an output end of the input rectifying/smoothing circuit through a primary winding of a transformer;

an output rectifying/smoothing circuit that rectifies and smoothes a voltage induced in a secondary winding of the transformer and outputs a direct current output voltage; and

a control circuit that controls ON and OFF of the switching element, wherein the control circuit includes an overvoltage protection circuit that detects a voltage corresponding to the alternating current input voltage and a voltage corresponding to the direct current output voltage, outputs an overvoltage operation prohibition signal for prohibiting ON and OFF operations of the switching element when the voltage corresponding to the direct current output voltage rises to a first threshold value or more, and releases the overvoltage operation prohibition signal when the alternating current input voltage drops and the voltage corresponding to the alternating current input voltage falls down below a second threshold value.

2. The switching power supply device according to claim 1, wherein the overvoltage protection circuit detects a voltage obtained by rectifying and smoothing the alternating current input voltage.

3. The switching power supply device according to claim 1, wherein the overvoltage protection circuit detects a pulsating voltage proportional to a peak value of the alternating current input voltage.

4. The switching power supply device according to claim 1, wherein the overvoltage protection circuit performs current conversion for a pulsating voltage proportional to a peak value of the alternating current input voltage, and detects the voltage subjected to the current conversion.

5. The switching power supply device according to claim 1, wherein,

the control circuit includes a low-input protection circuit that detects the voltage corresponding to the alternating current input voltage, and

an input terminal of the low-input protection circuit is connected, on an integrated circuit, commonly with an input terminal for detecting the voltage corresponding to the alternating current input voltage in the overvoltage protection circuit.

6. A switching power supply device, comprising:

an input rectifying/smoothing circuit that rectifies and smoothes an alternating current input voltage and outputs a direct current input voltage;

a switching element connected to an output end of the input rectifying/smoothing circuit through a primary winding of a transformer;

an output rectifying/smoothing circuit that rectifies and smoothes a voltage induced in a secondary winding of the transformer and outputs a direct current output voltage; and

a control circuit that controls ON/OFF of the switching element, the control circuit including;

an overvoltage protection circuit that detects a voltage corresponding to the direct current output voltage; and

a low-input protection circuit that is connected to the overvoltage protection circuit and detects a voltage corresponding to the alternating current input voltage, wherein,

the overvoltage protection circuit outputs an overvoltage operation prohibition signal for prohibiting ON and OFF operations of the switching element when the voltage corresponding to the direct current output voltage rises to a first threshold value or more, and

the low-input protection circuit outputs a signal for releasing the overvoltage operation prohibition signal to the overvoltage protection circuit when the alternating current input voltage drops and the voltage corresponding to the alternating current input voltage falls down below a second threshold value.

7. The switching power supply device according to claim 6, wherein the low-input protection circuit rectifies and smoothes the alternating current input voltage, and detects the rectified and smoothed voltage.

8. The switching power supply device according to claim 6, wherein the low-input protection circuit detects a pulsating voltage proportional to a peak value of the alternating current input voltage.

9. The switching power supply device according to claim 6, wherein the low-input protection circuit performs current conversion for a pulsating voltage proportional to a peak value of the alternating current input voltage, and detects the voltage subjected to the current conversion.