Flyback driver for use in a flyback power converter and related method

• US 9,326,333 B2
• Filed: 10/14/2011
• Issued: 04/26/2016
• Est. Priority Date: 10/14/2011
• Status: Active Grant

• Current Assignee: Infineon Technologies Americas Corp. (Infineon Technologies AG)
• Original Assignee: Infineon Technologies Americas Corp. (Infineon Technologies AG)
• Inventors: Green, Peter B., Wilhelm, Dana
• Primary Examiner(s): Vo, Tuyet
• Application Number:
  US13/273,531
• Publication Number:
  US 20130093356A1
• Time in Patent Office: 1,656 Days
• Field of Search: 315/291, 315/224, 315/225, 315/247, 315/185.S, 315307-311
• US Class Current: 1/1
• CPC Class Codes: H02M 1/4258 using a single converter stage both for correction of AC input power factor and generation of a regulated and galvanically isolated DC output voltage H02M1/4241 takes precedence
• CPC Class Codes: H02M 3/33523 with galvanic isolation between input and output of both the power stage and the feedback loop
• CPC Class Codes: H05B 45/385 using flyback topology
• 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

According to one embodiment, a flyback power converter comprises a primary circuit including a flyback driver, and an isolated output circuit responsive to the primary circuit. The isolated output circuit is used to power a load. The flyback driver is configured to identify a load current in the isolated output circuit from an input power to the primary circuit, and to regulate the load current according to the input power. In one embodiment, the flyback driver is configured to sense an input voltage to the flyback power converter, to identify an average current value corresponding to a current through a converter switch in the primary circuit, and to multiply the average current value and the input voltage to determine the input power to the primary circuit.

Claims

1. A flyback power converter comprising:

a primary circuit including a flyback inductor and a flyback driver configured to receive power from an auxiliary winding of said flyback inductor;

an isolated output circuit including an isolated output inductor responsive to said primary circuit, said isolated output circuit powering a load;

said flyback driver coupled to a high voltage rail of said primary circuit and configured to identify a load current in said isolated output circuit from an input power to said primary circuit, and to regulate said load current according to said input power.

2. The flyback power converter of claim 1, wherein said flyback driver is configured to identify and regulate said load current without receiving a control signal from said isolated output circuit.

3. The flyback power converter of claim 1, wherein said load comprises at least one light-emitting diode (LED), and wherein said load current flows through said at least one LED.

4. The flyback power converter of claim 1, wherein said flyback driver is implemented as an integrated circuit (IC).

5. The flyback power converter of claim 1, wherein said flyback driver is configured to multiply an average current value and an input voltage to said flyback power converter, thereby determining said input power to said primary circuit.

6. The flyback power converter of claim 5, wherein said flyback driver comprises an analog multiplier configured to multiply said average current value and said input voltage.

7. The flyback power converter of claim 5, wherein'"'"'said average current value corresponds to an average of a ramp current produced by said primary circuit.

8. A flyback driver in a primary circuit including a flyback inductor and configured for use in a flyback power converter, said flyback driver coupled to a high voltage rail of said primary circuit, said flyback driver configured to receive power from an auxiliary winding of said flyback inductor, to identify a load current in an isolated output circuit, including an isolated output inductor responsive to said primary circuit, according to an input power to said primary circuit of said flyback power converter, and to regulate said load current according to said input power.

9. The flyback driver of claim 8, wherein said flyback driver is configured to identify and regulate said load current without receiving a control signal from said isolated output circuit.

10. The flyback driver of claim 8, wherein at least one light-emitting diode (LED) is utilized as a load, and wherein said load current flows through said at least one LED.

11. The flyback driver of claim 8, wherein said flyback driver is implemented as an integrated circuit (IC).

12. The flyback driver of claim 8, wherein said flyback driver comprises an analog multiplier configured to multiply an average current value and an input voltage to said flyback power converter, thereby determining said input power to said primary circuit.

13. The flyback driver of claim 12, wherein said average current value corresponds to an average of a ramp current produced by said primary circuit.

14. A method for use in a flyback power converter, said method comprising:

powering a flyback driver in a primary circuit of said flyback power converter using an auxiliary winding of a flyback inductor in said primary circuit, said flyback driver being coupled to a high voltage rail of said primary circuit;

determining, by said flyback driver, an input power to said primary circuit;

utilizing said input power, by said flyback driver, to identify a load current in an isolated output circuit in said flyback power converter, said isolated output circuit including an isolated output inductor responsive to said primary circuit;

regulating, by said flyback driver, said load current according to said input power.

15. The method of claim 14, wherein identifying and regulating said load current is performed without receiving a control signal from said isolated output circuit.

16. The method of claim 14, wherein said load current is used to power a load comprising at least one light-emitting diode (LED), and wherein said load current flows through said at least one LED.

17. The method of claim 14, further comprising:

sensing a flyback inductor voltage in said primary circuit;

turning a converter switch of said primary circuit OFF when said flyback inductor voltage exceeds a threshold voltage.

18. The method of claim 14, wherein determining said input power to said primary circuit comprises:

sensing an input voltage to said flyback power converter;

identifying an average current value corresponding to a current through a converter switch in said primary circuit;

multiplying said average current value and said input voltage to determine said input power to said primary circuit.

19. The method of claim 18, wherein multiplying said average current value and said input voltage is performed using an analog multiplier.

20. The method of claim 18, wherein said average current value corresponds to an average of a ramp current produced by said primary circuit.