Regulation for power supply mode transition to low-load operation

Patent metadata

Field	Value
Publication number	US-9419527-B2
Application number	US-201313772202-A
Country	US
Kind code	B2
Filing date	Feb 20, 2013
Priority date	Mar 7, 2012
Publication date	Aug 16, 2016
Grant date	Aug 16, 2016

Abstract

A switching power converter includes a controller configured to transition from a first operating mode to a second operating mode by determining the operating conditions at the transition point between the operation modes. The controller uses a point where a switch included in the power converter would have been turned on if operating under the first operating mode as a reference point to determine when to turn on the switch under the second operating mode. Using the reference point, the switching power converter determines a control period for regulating the switching period of the switch in a second operating mode.

First claim

What is claimed is:

1. A switching power converter comprising:
a transformer including a primary winding coupled to an input voltage and a secondary winding coupled to an output of the switching power converter;
a switch coupled to the primary winding of the transformer, current through the primary winding being generated while the switch is turned on and not being generated while the switch is turned off; and
a controller configured to generate a control signal to turn on or turn off the switch, the switch being turned on responsive to the control signal being in a first state and the switch being turned off responsive to the control signal being in a second state, wherein:
responsive to a load level at the output of the switching power converter being less than a first load level but greater than a second load level, the second load level being less than the first load level, the controller is further configured to generate the control signal based on a first operation mode, during the first operation mode the switching power converter regulating a duty cycle of the control signal applied to the switch by performing one of:
varying a conduction pulse width of the control signal and keeping a switching period of the control signal constant, or
varying the conduction pulse width of the control signal and varying the switching period of the control signal;

responsive to the load at the output of the switching power converter being less than the second load level but greater than a third load level, the third load level being less than the second load level, the controller is further configured to generate the control signal based on a second operation mode, during the second operation mode the switching power converter regulating the duty cycle of the control signal applied to the switch by keeping the conduction pulse width constant and varying the switching period; and
wherein at a transition point between the first operation mode and the second operation mode, the controller is further configured to use a point during the first operation mode when the switch would have been turned on prior to transitioning to the second operation mode as a reference point to determine when to turn on the switch during the second operation mode.

2. The switching power converter of claim 1 , wherein in the second operation mode, the controller is further configured to turn on the switch at an end of a control period, the control period representing an amount of time that the controller extends the switching period beyond the reference point when operating in the second operation mode.

3. The switching converter of clam 1 , wherein the first operation mode is a valley mode switching operation mode.

4. The switching converter of clam 1 , wherein the first operation mode is a pulse width modulation operation mode.

5. The switching converter of clam 1 , wherein the reference point is determined in accordance with valley mode switching operation mode.

6. The switching converter of clam 1 , wherein the reference point is determined in accordance with pulse width modulation operation mode.

7. The switching converter of claim 1 , wherein the reference point coincides with the end of the off duration of the switch in the first operation mode.

8. A method of controlling a switching power converter, the switching power converter including a transformer with a primary winding coupled to an input voltage and a secondary winding coupled to an output of the switching power converter, and a switch coupled to the primary winding of the transformer, current in the primary winding being generated while the switch is turned on and not being generated while the switch is turned off, the method comprising:
generating a control signal to turn on or turn off the switch, the switch being turned on responsive to the control signal being in a first state and the switch being turned off responsive to the control signal being in a second state, wherein:
responsive to a load level at the output of the switching power converter being less than a first load level but greater than a second load level, the second load level being less than the first load level, generating the control signal based on a first operation mode, during the first operation mode the switching power converter regulating a duty cycle of the control signal applied to the switch by performing one of:
varying a conduction pulse width of the control signal and keeping a switching period of the control signal constant, or
varying the conduction pulse width of the control signal and varying the switching period of the control signal;

responsive to the load at the output of the switching power converter being less than the second load level but greater than a third load level, the third load level being less than the second load level, generating the control signal based on a second operation mode, during the second operation mode the switching power converter regulating the duty cycle of the control signal applied to the switch by keeping the conduction pulse width constant and varying the switching period; and
wherein at a transition point between the first operation mode and the second operation mode, using an operating point during the first operation mode when the switch would have been turned on prior to transitioning to the second operation mode as a reference point to determine when to turn on the switch during the second operation mode.

9. The method of claim 8 , wherein during the second operation mode, turning on the switch at an end of a control period, the control period representing an amount of time that the controller extends the switching period beyond the reference point when operating in the second operation mode.

10. The method of clam 8 , wherein the first operation mode is a valley mode switching operation mode.

11. The method of clam 8 , wherein the first operation mode is a pulse width modulation operation mode.

12. The method of clam 8 , wherein the reference point is determined in accordance with valley mode switching operation mode.

13. The method of clam 8 , wherein the reference point is determined in accordance with pulse width modulation operation mode.

14. The method of claim 8 , wherein the reference point coincides with the end of the off duration of the switch in the first operation mode.

Assignees

• Iwatt Inc
• Dialog Semiconductor Inc

Inventors

• Yan Liang
• Kesterson John William
• Wang Xiaoyan

Classifications

• H02M3/33507 Primary

  with automatic control of the output voltage or current, e.g. flyback converters (H02M3/33561, H02M3/33569 take precedence) · CPC title

• H02M2001/0032

  Electricity · mapped topic

• Y02B70/16

  Cross-Sectional Technologies · mapped topic

• H02M1/12

  Arrangements for reducing harmonics from AC input or output · CPC title

• H02M3/28 Primary

  using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate AC · CPC title