Method and apparatus to limit maximum switch current in a switch of a switching power supply

• US 20070008753A1
• Filed: 07/08/2005
• Published: 01/11/2007
• Est. Priority Date: 07/08/2005
• Status: Active Grant

• Current Assignee: Power Integrations Incorporated
• Original Assignee: Power Integrations Incorporated
• Inventors: Kroes, Derek
• Granted Patent: US 7,613,019 B2
• Time in Patent Office: Days
• US Class Current: 363/56.10
• CPC Class Codes: H02M 1/0009 Devices or circuits for detecting current in a converter
• CPC Class Codes: H02M 1/0038 Circuits or arrangements for suppressing, e.g. by masking incorrect turn-on or turn-off signals, e.g. due to current spikes in current mode control
• CPC Class Codes: H02M 1/32 Means for protecting converters other than automatic disconnection
• 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: Y10S 323/908 Inrush current limiters

Abstract

Techniques are disclosed to limit the current in a switch of a switching power supply. An example switching regulator circuit includes a switch to be coupled to an energy transfer element. A controller is coupled to the switch to control switching of the switch. A current sensor is included in the controller. The current sensor includes first and second comparators coupled to compare a current in the switch with first and second current limits, respectively. The controller is to open the switch for a remainder of a current switching cycle of the switch until a next switching cycle of the switch in response to the first or second comparators. A frequency adjuster is also included in the controller and coupled to the second comparator. The frequency adjuster is to adjust an oscillating frequency of an oscillator included in the controller in response to the second comparator.

Claims

1. A switching regulator circuit, comprising:

a switch to be coupled to an energy transfer element;

a controller coupled to the switch to control switching of the switch;

a current sensor included in the controller and including first and second comparators coupled to compare a current in the switch with first and second current limits, respectively, the controller to open the switch for a remainder of a current switching cycle of the switch until a next switching cycle of the switch in response to the first or second comparators; and

a frequency adjuster included in the controller and coupled to the second comparator, the frequency adjuster to adjust an oscillating frequency of an oscillator included in the controller in response to the second comparator.

2. The switching regulator of claim 1 wherein the frequency adjuster is to reduce the oscillating frequency of the oscillator to delay the next switching cycle of the switch in response to the second comparator.

3. The switching regulator of claim 1 wherein the frequency adjuster is to reduce the oscillating frequency of the oscillator to skip the next switching cycle of the switch in response to the second comparator.

4. The switching regulator of claim 1 wherein the controller is included in an integrated circuit.

5. The switching regulator of claim 4 wherein the switch is included in the integrated circuit.

6. The switching regulator of claim 1 wherein the second current limit is greater than the first current limit.

7. The switching regulator of claim 1 further comprising a leading edge blanking circuit included in the controller and coupled to the current sensor.

8. The switching regulator of claim 1 wherein the frequency adjuster is to adjust the oscillating frequency of the oscillator to provide uninterrupted regulation at an output coupled to the energy transfer element.

9. A method for regulating a transfer of energy, comprising:

switching a switch coupled to an energy transfer element to regulate a transfer of energy through the energy transfer element;

opening the switch for a remainder of a current switching cycle of the switch until a next switching cycle of the switch if a current in the switch is greater than a first or second current limit; and

delaying the next switching cycle of the switch if the current in the switch is greater than the second current limit.

10. The method for regulating the transfer of energy of claim 9 wherein delaying the next switching cycle of the switch comprises adjusting a frequency of an oscillator if the current in the switch is greater than the second current limit.

11. The method for regulating the transfer of energy of claim 9 wherein delaying the next switching cycle of the switch comprises skipping the next switching cycle of the switch if the current in the switch is greater than the second current limit.

12. The method for regulating the transfer of energy of claim 9 wherein the second current limit is greater than the first current limit.

13. The method for regulating the transfer of energy of claim 9 further comprising ignoring the current through the switch during a leading edge blanking time of each switching cycle of the switch.

14. The method for regulating the transfer of energy of claim 9 wherein the delaying of the next switching cycle comprises maintaining uninterrupted regulation of an output coupled to the energy transfer element.

15. A power supply, comprising:

an energy transfer element coupled between an input and an output of the power supply;

a switch coupled to the input of the energy transfer element to regulate a transfer of energy from the input of the power supply to the output of the power supply;

a controller coupled to the switch to control switching of the switch;

a current sensor included in the controller and including first and second comparators coupled to compare a current in the switch with first and second current limits, respectively, the controller to open the switch for a remainder of a current switching cycle of the switch until a next switching cycle of the switch in response to the first or second comparators; and

a frequency adjuster included in the controller and coupled to the second comparator, the frequency adjuster to adjust an oscillating frequency of an oscillator included in the controller in response to the second comparator.

16. The power supply of claim 15 further comprising a feedback circuit coupled between the output of the power supply and the controller to provide a feedback signal from the output of the power supply to the controller.

17. The power supply of claim 15 further comprising an integrated circuit including the controller.

18. The power supply of claim 17 wherein the integrated circuit further comprises the switch.

19. The power supply of claim 15 wherein the second current limit is greater than the first current limit.

20. The power supply of claim 15 wherein the frequency adjuster is to adjust the oscillating frequency of the oscillator to provide uninterrupted regulation at the output of the power supply.