POWER SUPPLY CONTROLLER, ELECTRONIC DEVICE, AND METHOD FOR CONTROLLING POWER SUPPLY

• US 20120081085A1
• Filed: 07/13/2011
• Published: 04/05/2012
• Est. Priority Date: 10/05/2010
• Status: Active Grant

• Current Assignee: Socionext Inc.
• Original Assignee: Fujitsu Semiconductor Limited (Fujitsu Limited)
• Inventors: MIYAMAE, Toru
• Granted Patent: US 8,441,239 B2
• Time in Patent Office: Days
• US Class Current: 323/271
• CPC Class Codes: H02M 3/156 with automatic control of output voltage or current, e.g. switching regulators

Abstract

A comparator type power supply controller that controls an output voltage. The power supply controller includes a comparator that compares a feedback voltage, which corresponds to the output voltage, with a reference voltage, wherein the comparator instructs power supply when the feedback voltage decreases when the feedback voltage decreases from the reference voltage. An offset application circuit is coupled to the comparator. The offset application circuit controls an input offset voltage of the comparator and decreases the input offset voltage as time elapses when the feedback voltage becomes lower than the reference voltage after the power supply ends. An amplifier amplifies a voltage difference of the feedback voltage and the reference voltage. The offset application circuit increases a change speed of the input offset voltage as the voltage difference increases in accordance with an output voltage of the amplifier.

Claims

1. A comparator type power supply controller that controls an output voltage, the power supply controller comprising:

a comparator that compares a feedback voltage, which corresponds to the output voltage, with a reference voltage and instructs power supply when the feedback voltage decreases from the reference voltage;

an offset application circuit coupled to the comparator to control an input offset voltage of the comparator, wherein the offset application circuit decreases the input offset voltage as time elapses when the feedback voltage becomes lower than the reference voltage after the power supply ends; and

an amplifier that amplifies a voltage difference of the feedback voltage and the reference voltage;

wherein the offset application circuit increases a change speed of the input offset voltage as the voltage difference increases in accordance with an output voltage of the amplifier.

2. The power supply controller according to claim 1, wherein the offset application circuit includes a delay circuit that delays a change start timing of the input offset voltage in accordance with an output voltage of the amplifier.

3. The power supply controller according to claim 2, wherein the offset application circuit includes:

a charge circuit that starts charging in response to a change start command of the input offset voltage supplied from the delay circuit; and

a differential pair that receives an output voltage of the charge circuit and a certain voltage and generates divided currents, wherein the divided currents flow from the differential pair to a load of the comparator.

4. The power supply controller according to claim 1, wherein

the offset application circuit includes a charge circuit having a charge current controlled in accordance with the output voltage of the amplifier, and

a change in the input offset voltage is adjusted in accordance with an output voltage of the charge circuit.

5. The power supply controller according to claim 4, wherein the offset application circuit includes a differential pair that receives the output voltage of the charge circuit and a certain voltage and generates divided currents, wherein the divided currents flow from the differential pair to a load of the comparator.

6. The power supply controller according to claim 1, wherein the offset application circuit includes:

a charge circuit that starts charging when the power supply ends; and

a differential pair that receives an output voltage of the charge circuit and the output voltage of the amplifier and generates divided currents;

wherein the divided currents flow from the differential pair to a load of the comparator.

7. An electronic device comprising:

a comparator type power supply; and

a load circuit supplied with power from the power supply, wherein the power supply includes;

a comparator that compares a feedback voltage, which corresponds to an output voltage of the power supply, with a reference voltage, wherein the comparator instructs power supply when the feedback voltage decreases from the reference voltage;

an offset application circuit coupled to the comparator, wherein the offset application circuit controls an input offset voltage of the comparator, and the offset application circuit decreases the input offset voltage as time elapses when the feedback voltage becomes lower than the reference voltage after the power supply ends; and

an amplifier that amplifies a voltage difference of the feedback voltage and the reference voltage;

wherein the offset application circuit increases a change speed of the input offset voltage as the voltage difference increases in accordance with an output voltage of the amplifier.

8. A method for controlling a comparator type power supply that controls an output voltage, the method comprising:

comparing a feedback voltage, which corresponds to the output voltage, with a reference voltage;

instructing power supply when the feedback voltage decreases from the reference voltage;

decreasing an input offset voltage of the comparator of the power supply as time elapses when the feedback voltage becomes lower than the reference voltage after the power supply ends; and

increasing a change speed of the input offset voltage as a voltage difference of the feedback voltage and the reference voltage increases.

9. A comparator type power supply controller that controls an output voltage, the power supply controller comprising:

a comparator that compares a feedback voltage, which corresponds to the output voltage, with a reference voltage;

an offset control circuit coupled to the comparator, wherein the offset control circuit controls an input offset voltage of the comparator; and

an amplifier that amplifies a voltage difference of the feedback voltage and the reference voltage and supplies the amplified voltage difference to the offset control circuit;

wherein the offset control circuit includes;

a slope generation unit including a capacitor charged by a charge current; and

a differential pair that receives a charge voltage of the capacitor and a certain voltage and generates divided currents, wherein

the divided currents flow from the differential pair to a load of the comparator, and

the slope generation unit changes a charge profile of the charge voltage by delaying a charge start timing of the capacitor or changing an increase speed of a charge voltage of the capacitor in accordance with the amplified voltage difference.