Controller for a Power Converter and Method of Operating the Same

• US 20140009978A1
• Filed: 07/06/2012
• Published: 01/09/2014
• Est. Priority Date: 07/06/2012
• Status: Active Grant

• Current Assignee: Power Systems Technologies Company Limited (Flex, Ltd.)
• Original Assignee: Power Systems Technologies Company Limited (Flex, Ltd.)
• Inventors: Brinlee, Antony, Chandrasekaran, Sriram, Malechek, Steven
• Granted Patent: US 9,190,898 B2
• Time in Patent Office: Days
• US Class Current: 363/25
• CPC Class Codes: H02M 1/0025 Arrangements for modifying reference values, feedback values or error values in the control loop of a converter
• CPC Class Codes: H02M 1/0035 using burst mode control
• CPC Class Codes: H02M 1/0058 by employing soft switching techniques, i.e. commutation of transistors when applied voltage is zero or when current flow is zero using an auxiliary actively switched resonant commutation circuit connected to an intermediate DC voltage or between two push-pull branches of an inverter bridge H02M7/4811; in resonant inverters H02M7/4815; in inverters operating from a resonant DC source H02M7/4826
• CPC Class Codes: H02M 1/007 Plural converter units in cascade push-pull DC/DC converters with pre-regulator H02M3/3374; DC-AC converters following a DC-DC stage including a high frequency transformer H02M7/4807; DC-AC converters following a DC-DC conversion stage generating periodically varying voltages H02M7/4826
• CPC Class Codes: H02M 1/4225 using a non-isolated boost converter
• CPC Class Codes: H02M 3/01 Resonant DC/DC converters
• CPC Class Codes: H02M 3/33571 Half-bridge at primary side of an isolation transformer
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

A controller for a power converter and method of operating the same. In one embodiment, the controller includes an inductor-inductor-capacitor (“LLC”) controller configured to receive an error signal from an error amplifier to control a switching frequency of an LLC stage of the power converter to regulate an output voltage thereof. The controller also includes a power factor correction (“PFC”) controller configured to control a bus voltage produced by a PFC stage of the power converter and provided to the LLC stage so that an average switching frequency thereof is substantially maintained at a desired switching frequency.

Claims

1. A controller for use with a power converter, comprising:

an inductor-inductor-capacitor (LLC) controller configured to receive an error signal from an error amplifier to control a switching frequency of an LLC stage of said power converter to regulate an output voltage thereof; and

a power factor correction (PFC) controller configured to control a bus voltage produced by a PFC stage of said power converter and provided to said LLC stage so that an average switching frequency thereof is substantially maintained at a desired switching frequency.

2. The controller as recited in claim 1 wherein said PFC stage is a PFC boost stage and said LLC stage is a LLC resonant buck stage.

3. The controller as recited in claim 1 wherein a control loop associated with said LLC stage has a faster response than a control loop associated with said PFC stage.

4. The controller as recited in claim 1 wherein said LLC controller comprises a nonlinear function subsystem configured to apply a correction factor to said error signal to produce a corrected error signal.

5. The controller as recited in claim 4 wherein said correction factor is approximated by a broken line correction factor.

6. The controller as recited in claim 4 wherein said LLC controller comprises a voltage controlled oscillator configured to receive said corrected error signal to control said switching frequency of said LLC stage.

7. The controller as recited in claim 1 wherein said PFC controller is configured to elevate said bus voltage to generate an error in said error signal to detect light-load operation of said power converter.

8. The controller as recited in claim 1 wherein said error amplifier is coupled to a resistor divider configured to sense said output voltage and provide a sensed output voltage to an operational amplifier of said error amplifier to produce said error signal.

9. The controller as recited in claim 1 wherein said PFC stage comprises at least one error amplifier configured to control said bus voltage as a function of said switching frequency of said LLC stage and said desired switching frequency.

10. The controller as recited in claim 1 further comprising a burst mode controller configured to cause said power converter to enter a burst mode of operation under a light load.

11. The controller as recited in claim 1 further comprising a burst mode controller configured to cause said power converter to enter a burst mode of operation when said error signal crosses a burst threshold level.

12. The controller as recited in claim 1 wherein a resistor divider is configured to sense said output voltage, and first and second sense switches, coupled to said resistor divider, are configured to reduce a power dissipation when said power converter enters a burst mode of operation.

13. The controller as recited in claim 1 wherein said desired switching frequency is substantially equal to a resonant frequency of said LLC stage.

14. A method of operating a power converter, comprising:

receiving an error signal from an error amplifier to control a switching frequency of an inductor-inductor-capacitor (LLC) stage of said power converter to regulate an output voltage thereof; and

controlling a bus voltage produced by a power factor correction (PFC) stage of said power converter and provided to said LLC stage so that an average switching frequency thereof is substantially maintained at a desired switching frequency.

15. The method as recited in claim 14 wherein a control loop associated with said LLC stage has a faster response than a control loop associated with said PFC stage.

16. The method as recited in claim 14 further comprising applying a correction factor to said error signal to produce a corrected error signal and controlling said switching frequency of said LLC stage as a function thereof.

17. The method as recited in claim 14 further comprising elevating said bus voltage to generate an error in said error signal to detect light-load operation of said power converter.

18. The method as recited in claim 14 further comprising causing said power converter to enter a burst mode of operation under a light load.

19. The method as recited in claim 14 further comprising causing said power converter to enter a burst mode of operation when said error signal crosses a burst threshold level.

20. The method as recited in claim 14 further comprising sensing said output voltage, and reducing a power dissipation when said power converter enters a burst mode of operation.