Power supply circuit

• US 20080218136A1
• Filed: 02/28/2008
• Published: 09/11/2008
• Est. Priority Date: 12/07/2004
• Status: Active Grant

• Current Assignee: Ricoh Company Limited
• Original Assignee: Ricoh Company Limited
• Inventors: Agari, Hideki
• Granted Patent: US 7,550,955 B2
• Time in Patent Office: Days
• US Class Current: 323/268
• CPC Class Codes: G05F 1/575 characterised by the feedback circuit

Abstract

A disclosed power supply circuit (1) for receiving an input voltage at an input terminal (VDD), converting the input voltage to an output voltage and outputting the output voltage to a load (10) connected to an output terminal (OUT), comprises: a power supply circuit unit (2) for converting the input voltage to a predetermined constant voltage and outputting the converted voltage to the output terminal, the power supply circuit unit operating in accordance with a first control signal (CE); an output current detecting circuit unit (3) for detecting a current output (iout) from the power supply circuit unit, and outputting a second control signal when the detected current is smaller than a predetermined value i1; and an output voltage detecting circuit unit (4) for detecting a voltage output (Vout) from the power supply circuit unit, and operating while the output current detecting circuit unit outputs the second control signal, the output voltage detecting circuit unit stopping operation of the power supply circuit unit with the first control signal when the detected voltage exceeds a predetermined value Vdet1; whereby the output supply voltage detecting circuit unit makes the power supply circuit unit operate when the detected voltage becomes equal to or lower than a predetermined value Vdet2 that is lower than the predetermined value Vdet1, and thereby the power supply circuit unit performs intermittent operations.

Claims

1. A power supply circuit for converting an input voltage to an output voltage, comprising:

a first unit for converting the input voltage to a predetermined voltage level, operating in accordance with a first control signal;

a second unit for detecting at least one of a current output and a voltage output from the first unit, and outputting a second control signal; and

a third unit for detecting the other one of the current output and voltage output from the first unit, operating in accordance with the second control signal, and outputting the first control signal,

wherein the second unit is configured to output the second control signal and the third unit is configured to output the first control signal such that the first unit performs intermittent operations.

15. The power supply circuit of claim 1, wherein

the second unit detects a current output from the first unit, and outputs the second control signal to the third unit when the detected current output is smaller than a predetermined current value;

and

the third unit stops output of the first control signal when the second control unit outputs the second control signal and voltage output from the first unit exceeds a certain value.

2-14. -14. (canceled)

16. A method of converting a voltage, the method comprising:

applying a first voltage at an input of a first unit for converting a voltage by a set ratio, wherein the first unit operates in accordance with a first control signal;

converting the first voltage and outputting the converted voltage with the first unit in accordance with the first control signal;

monitoring at least one of a voltage output and a current output from the first unit; and

intermittently stopping conversion of the first voltage based upon preset levels of the monitored at least one of a voltage output and a current output.

17. The method of claim 16, wherein the step of monitoring at least one of an voltage output and a current output includes:

monitoring the current output from the first unit; and

monitoring the voltage output when the monitored output current is less than a preset current level.

18. The method of claim 17, wherein the step of intermittently stopping conversion of the voltage according to preset levels of the monitored voltage output and current output includes stopping conversion of the first voltage when the monitored voltage output exceeds a preset voltage level.