Power converter with winding communication

• US 9,584,027 B2
• Filed: 04/10/2015
• Issued: 02/28/2017
• Est. Priority Date: 04/10/2015
• Status: Active Grant

• Current Assignee: Power Integrations Incorporated
• Original Assignee: Power Integrations Incorporated
• Inventors: Polivka, William M.
• Primary Examiner(s): ROSARIO BENITEZ, GUSTAVO A
• Application Number:
  US14/684,002
• Publication Number:
  US 20160301314A1
• Time in Patent Office: 690 Days
• US Class Current: 1/1
• 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: H02M 3/33592 having a synchronous rectifier circuit or a synchronous freewheeling circuit at the secondary 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 power converter includes an energy transfer element, a switched element, a secondary control circuit, a primary switching, and a primary control circuit. The secondary control circuit generates a voltage pulse across a secondary winding of the energy transfer element while the secondary winding provides current to an output. The secondary control circuit is coupled to vary a voltage across the switched element to generate the voltage pulse across the secondary winding in response to an output of the power converter. The primary control circuit is coupled to the primary switch and a third winding of the energy transfer element. The primary control circuit is coupled to switch the primary switch to regulate the output in response to the voltage pulse. The secondary winding is coupled to reflect the voltage pulse onto the third winding which is on the same side of the energy transfer element as a primary winding.

Claims

1. A power converter comprising:

an energy transfer element including a first winding, a second winding, and a third winding, wherein the first winding is coupled to an input voltage and the second winding is coupled to an output of the power converter;

a switched element coupled to the second winding;

a secondary control circuit coupled to generate a voltage pulse across the second winding while the second winding provides current to the output, wherein the secondary control circuit is coupled to vary a voltage across the switched element to generate the voltage pulse across the second winding in response to the output of the power converter being at or above a reference value, wherein the secondary control circuit includes;

a synchronous rectifier controller configured to generate an enable signal and a delayed enable pulse when a primary switch is off; and

a pulse generator coupled to generate a disable pulse at a pulse generator output in response to receiving an output signal and the delayed enable pulse, wherein the disable pulse has a shorter duration than a duration of the enable signal;

the primary switch coupled to the first winding; and

a primary control circuit coupled to the primary switch and the third winding, the primary control circuit coupled to switch the primary switch to regulate the output of the power converter in response to the voltage pulse, wherein the second winding is coupled to reflect the voltage pulse onto the third winding.

2. The power converter of claim 1, wherein the switched element includes a transistor and the secondary control circuit is coupled to output a secondary drive signal to selectively disable the transistor to increase the voltage across the switched element while the secondary current through the second winding provides current to the output in response to the output of the power converter falling below the reference value.

3. The power converter of claim 2, wherein the switched element also includes a diode coupled in parallel with the transistor, wherein the diode has a forward voltage that is larger than a transistor voltage across the transistor when the transistor is enabled.

4. The power converter of claim 2, wherein the secondary control circuit further includes:

a first comparator coupled to generate the output signal on a comparator output when the output of the power converter is above the reference value;

the synchronous rectifier controller coupled to sense at least one of a secondary voltage across the second winding and a secondary current through the second winding to determine when the primary switch is off; and

secondary logic coupled to generate the secondary drive signal in response to the enable signal and the disable pulse, wherein the secondary drive signal disables the transistor when the secondary logic receives the enable signal and the disable pulse, and wherein the secondary drive signal enables the transistor when the secondary logic receives the enable signal and not the disable pulse.

5. The power converter of claim 4, wherein the pulse generator includes:

an AND gate coupled to receive the delayed enable pulse and the output signal; and

a monostable multivibrator coupled to generate the disable pulse in response to an output of the AND gate.

6. The power converter of claim 4, wherein the delayed enable pulse is generated after a delay time, and wherein the delay time indicates at least one of an output current or a temperature of the power converter.

7. The power converter of claim 4, wherein the delayed enable pulse is generated after a delay time, and wherein the delay time increases when an output current of the power converter changes in a first direction, and wherein the delay time decreases when the output current changes in a second direction that is opposite the first direction.

8. The power converter of claim 4, wherein a duration of the delayed enable pulse indicates at least one of an output current or a temperature of the power converter.

9. The power converter of claim 4, wherein a duration of the delayed enable pulse increases when an output current of the power converter changes in a first direction, and wherein the duration of the delayed enable pulse decreases when the output current changes in a second direction that is opposite the first direction.

10. The power converter of claim 2, wherein a magnitude of rate of change of the secondary current through the second winding increases when the voltage pulse is across the second winding.

11. The power converter of claim 1, wherein the primary control circuit is coupled to delay switching the primary switch for one or more periods in response to observing the voltage pulse.

12. The power converter of claim 1, wherein the primary control circuit includes voltage sense circuitry coupled to the third winding to observe the voltage pulse.

13. The power converter of claim 1, wherein the second winding of the energy transfer element is galvanically isolated from the first and third windings.

14. The power converter of claim 1, wherein the power converter is a flyback converter topology.

15. The power converter of claim 1, wherein the energy transfer element includes a transformer.

16. The power converter of claim 1, wherein the energy transfer element includes a coupled inductor.

17. A controller for a power converter comprising:

a synchronous rectifier controller coupled to sense a secondary current through a secondary winding of the power converter, wherein the synchronous rectifier controller is configured to generate an enable signal and a delayed enable pulse when the secondary winding conducts the secondary current;

a comparator coupled to generate an output signal on a comparator output when an output of the power converter is above a reference value;

a pulse generator coupled to generate a disable pulse at a pulse generator output in response to receiving the output signal and the delayed enable pulse, wherein the disable pulse has a shorter duration than a duration of the enable signal, wherein the pulse generator includes;

an AND gate coupled to receive the delayed enable pulse and the output signal; and

a monostable multivibrator coupled to generate the disable pulse in response to an output of the AND gate; and

secondary logic to be coupled to a switched element coupled to the secondary winding, wherein the secondary logic is configured to generate a secondary drive signal to vary a voltage across the switched element to create a voltage pulse across the secondary winding.

18. The controller of claim 17, wherein the switched element includes a transistor and the secondary logic is coupled to output the secondary drive signal to selectively disable the transistor to increase the voltage across the switched element while the secondary winding provides current to the output in response to the output of the power converter falling below the reference value.

19. The controller of claim 18, wherein the secondary drive signal disables the transistor when the secondary logic receives the enable signal and the disable pulse, and wherein the secondary drive signal enables the transistor when the secondary logic receives the enable signal and not the disable pulse.

20. The controller of claim 17, wherein the voltage pulse across the secondary winding influences switching of a primary switch coupled to a primary winding inductively coupled to the secondary winding, the secondary drive signal generated in response to receiving the enable signal and the disable pulse.

21. A method of regulating a power converter, comprising:

enabling a switched element for an enabling window in response to sensing that a primary switch of the power converter is off, wherein the switched element is coupled to a second winding of an energy transfer element that also includes a third winding and a first winding coupled to an input of the power converter, and wherein the primary switch is coupled to the first winding to regulate an output of the power converter;

generating an enable signal and a delayed enable pulse in response to said sensing that the primary switch is off;

generating a disable pulse in response to the delayed enable pulse and the output of the power converter being at or above a reference value, wherein the disable pulse has a shorter duration that a duration of the enable signal, wherein a secondary drive signal coupled to control the switched element is generated in response to the enable signal and the disable pulse;

generating a voltage pulse on the second winding by adjusting a voltage across the switched element for a disabling duration in response to the output of the power converter being at or above the reference value, wherein the disabling duration is within the enabling window, and wherein secondary current is provided to the output through the second winding during the enabling window; and

switching the primary switch in response to the voltage pulse being reflected onto the third winding, wherein the second winding is coupled to reflect the voltage pulse onto the third winding.

22. The method of claim 21, wherein the switched element includes a transistor and a diode, and wherein enabling the switched element includes enabling the transistor.

23. The method of claim 22, wherein adjusting the voltage across the switched element for the disabling duration includes disabling the transistor for the disabling duration.

24. The method of claim 22, wherein the second winding of the energy transfer element is galvanically isolated from the first and third windings.

25. The method of claim 22, wherein said sensing that the primary switch of the power converter is off includes sensing secondary current through the second winding.

26. The method of claim 25, further comprising:

waiting until a next switching period of the primary switch in response to no secondary current being sensed in the second winding; and

switching the primary switch on and off at the next switching period.

27. The method of claim 22, wherein said sensing that the primary switch of the power converter is off includes sensing a secondary voltage across the second winding.