Hybrid adaptive power factor correction schemes for switching power converters
View Patent ↗A method of a controller of a switching power converter that provides a configurable power factor control method for the switching power converter. The controller combines power regulation control methods of constant on-time control and constant power control to adjust the power factor of the switching power converter. The controller switches between constant on-time control and constant power control based on an input voltage of the power converter.
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 at each of a plurality of switching cycles of the switch;
wherein the controller is further configured to generate the control signal to turn on the switch in a constant on-time mode of the switching power converter during each of the plurality of switching cycles for a first duration that is constant during each of the plurality of switching cycles corresponding to a first part of at least a single one of AC cycles of the input voltage responsive to the input voltage being less than a threshold voltage; and
wherein the controller is further configured to generate the control signal to turn on the switch in a constant power mode of the switching power converter during each of the plurality of switching cycles for a second duration that varies during at least some of the plurality of switching cycles corresponding to a second part of said at least the single one of the AC cycles of the input voltage responsive to the input voltage being greater than the threshold voltage;
wherein the controller does not receive a level of the input voltage and is further configured to determine whether the input voltage is less than or greater than the threshold voltage based on a slope of the current through the primary winding that is used by the controller as a proxy for the level of the input voltage.
2. The switching power converter of claim 1 , wherein the controller is further configured to determine whether the input voltage is less than the threshold voltage or greater than the threshold voltage during at least some of the plurality of switching cycles of the switch of said at least the single one of the AC cycles.
3. The switching power converter of claim 1 , wherein the second duration is less than the first duration.
4. The switching power converter of claim 1 , wherein the controller is further configured to determine the first duration based on a percentage of time that the switch is turned on for the first duration within said at least the single one of the AC cycles of the input voltage to the switching power converter.
5. The switching power converter of claim 4 , wherein the percentage of time that that the switch is turned on for the first duration within said at least the single one of the AC cycles of the input voltage to the switching power converter is indicative of a power factor of the switching power converter.
6. The switching power converter of claim 4 , wherein the controller is configured to determine the first duration by:
determining a configured percentage of time that the switch is turned on for the first duration corresponding to the first part of said at least the single of the AC cycles of the input voltage to the switching power converter;
setting an initial duration of time that the switch is to be turned on during the constant on-time mode;
calculating the percentage of time that the switch is turned on for the initial duration of time within said at least the single of the AC cycles of the input voltage to the switching power converter; and
adjusting the initial duration of time until the configured percentage of time that the switch is turned on within said at least the single of the AC cycles of the input voltage to the switching power converter is reached.
7. The switching power converter of claim 1 , wherein the controller is further configured to determine a third duration of time in which the switch is turned on during the constant on-time mode based on the output voltage during the constant on-time mode, wherein the third duration is greater than the first duration.
8. The switching power converter of claim 1 , wherein the controller is configured to generate the control signal to turn on the switch in the constant power mode at a next switching cycle of said at least the single one of the AC cycles of the input voltage responsive to the input voltage being greater than the threshold voltage.
9. In a controller, a method of controlling a switching power converter, the switching power converter including a transformer coupled between an input voltage and an output of the switching power converter, the transformer including a primary winding coupled to the input voltage and a secondary winding coupled to the output of the switching power converter, and 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, the method comprising:
generating a control signal to turn on or turn off the switch at each of a plurality of switching cycles of the switch;
wherein the control signal is generated to turn on the switch in a constant on-time mode of the switching power converter during each of the plurality of switching cycles for a first duration that is constant during each of the plurality of switching cycles corresponding to a first part of at least a single one of AC cycles of the input voltage responsive to the input voltage being less than a threshold voltage; and
wherein the control signal is generated to turn on the switch in a constant power mode of the switching power converter during each of the plurality of switching cycles for a second duration that varies during at least some of the plurality of switching cycles corresponding to a second part of said at least the single one of the AC cycles of the input voltage responsive to the input voltage being greater than the threshold voltage;
wherein the control signal is generated to turn on the switch in either the constant on-time mode or the constant power mode using a slope of the current through the primary winding and without the controller receiving a level of the input voltage, the slope of the current being a proxy for the level of the input voltage.
10. The method of claim 9 , further comprising:
determining whether the input voltage is less than the threshold voltage or greater than the threshold voltage during at least some of the plurality of switching cycles of the switch of said at least the single one of the AC cycles.
11. The method of claim 9 , wherein the second duration is less than the first duration.
12. The method of claim 9 , further comprising:
determining the first duration based on a percentage of time that the switch is turned on for the first duration within said at least the single one of the AC cycles of the input voltage to the switching power converter.
13. The method of claim 12 , wherein the percentage of time that that the switch is turned on for the first duration within said at least the single one of the AC cycles of the input voltage to the switching power converter is indicative of a power factor of the switching power converter.
14. The method of claim 12 , wherein determining the first duration comprises:
determining a configured percentage of time that the switch is turned on for the first duration corresponding to the first part of said at least the single of the AC cycles of the input voltage to the switching power converter;
setting an initial duration of time that the switch is turned on during the constant on-time mode;
calculating the percentage of time that the switch is to be turned on for the initial duration of time within said at least the single of the AC cycles of the input voltage to the switching power converter; and
adjusting the initial duration of time until the configured percentage of time that the switch is turned on within said at least the single of the AC cycles of the input voltage to the switching power converter is reached.
15. The method of claim 9 , further comprising:
determining a third duration of time in which the switch is turned on during the constant on-time mode based on the output voltage during the constant on-time mode, wherein the third duration is greater than the first duration.
16. The method of claim 9 , further comprising:
generating the control signal to turn on the switch in the constant power mode at a next switching cycle of said at least the single one of the AC cycles of the input voltage responsive to the input voltage being greater than the threshold voltage.