Method and apparatus for a switch mode power supply that generates a high pulse width modulation gain while maintaining low noise sensitivity

• US 7,369,418 B2
• Filed: 03/05/2007
• Issued: 05/06/2008
• Est. Priority Date: 11/13/2001
• Status: Expired due to Fees

• Current Assignee: Power Integrations Incorporated
• Original Assignee: Power Integrations Incorporated
• Inventors: Balakrishnan, Balu
• Primary Examiner(s): Laxton; Gary L.
• Application Number:
  US11/714,458
• Publication Number:
  US 20070159152A1
• Time in Patent Office: 428 Days
• Field of Search: 363/20, 363/21.01, 363/21.12, 363/21.17, 323/282, 323/284, 323/285
• US Class Current: 363/21.17
• CPC Class Codes: H02M 1/0006 Arrangements for supplying an adequate voltage to the control circuit of converters
• CPC Class Codes: H02M 3/1563 without using an external clock H02M3/158 takes precedence
• CPC Class Codes: H02M 3/33507 with automatic control of the output voltage or current, e.g. flyback converters H02M3/33561, H02M3/33569 take precedence
• CPC Class Codes: H02M 3/338 in a self-oscillating arrangement H02M3/337 takes precedence

Abstract

A power supply with high pulse width modulation gain and low noise sensitivity has been disclosed. In one embodiment, a power supply includes a regulator circuit controlling a power switch. The regulator circuit includes a control input that receives a current, which is the sum of a consumption current of the regulator and a feedback current. The consumption current of the regulator is varied as a function of the duty cycle of the power switch. The feedback current is the current in a shunt regulator, which is control current in excess of the internal consumption of the regulator.

Claims

1. A method, comprising:

receiving a control current at a regulator circuit, the control current including a subtraction current of the regulator circuit and a feedback current;

deriving an amount of the control current in excess of the subtraction current to derive the feedback current;

adjusting a duty cycle at which a power switch is switched in response to the feedback current; and

increasing the subtraction current of the regulator circuit during an on-time of the power switch in response to the duty cycle at which the power switch is switched.

2. The method of claim 1 wherein increasing the subtraction current comprises directing a portion of the subtraction current from the power switch to a ground terminal when the power switch is switched on.

3. The method of claim 1 wherein increasing the subtraction current comprises increasing the subtraction current in response to an increase in the duty cycle of the power switch.

4. The method of claim 1 wherein the feedback current is proportional to an output level of a power supply output, the method further comprising regulating the power supply output in response to the duty cycle of the power switch.

5. The method of claim 4 wherein regulating the power supply output further includes regulating the power supply output to have an approximately constant output voltage and output current characteristic.

7. The method of claim 1 wherein decreasing the subtraction current comprises directing a portion of the subtraction current from the power switch to a ground terminal when the power switch is switched on.

8. The method of claim 1 wherein decreasing the subtraction current comprises decreasing the subtraction current in response to a decrease in the duty cycle of the power switch.

9. The method of claim 1 wherein the feedback current is proportional to an output level of a power supply output, the method further comprising regulating the power supply output in response to the duty cycle of the power switch.

10. The method of claim 9 wherein regulating the power supply output further includes regulating the power supply output to have an approximately constant output voltage and output current characteristic.

6. A method, comprising:

receiving a control current at a regulator circuit, the control current including a subtraction current of the regulator circuit and a feedback current;

deriving an amount of the control current in excess of the subtraction current to derive the feedback current;

adjusting a duty cycle at which a power switch is switched in response to the feedback current; and

decreasing the subtraction current of the regulator circuit during an on-time of the power switch in response to the duty cycle at which the power switch is switched.