Generating a control signal based on leading edge dimming detection for maintaining input current of a power converter

• US 9,543,845 B2
• Filed: 09/16/2014
• Issued: 01/10/2017
• Est. Priority Date: 10/15/2013
• Status: Active Grant

• Current Assignee: Power Integrations Incorporated
• Original Assignee: Power Integrations Incorporated
• Inventors: Del Carmen, Jose Requinton Jr.
• Primary Examiner(s): Zhang, Jue
• Assistant Examiner(s): Jackson, Lakaisha
• Application Number:
  US14/487,862
• Publication Number:
  US 20150103568A1
• Time in Patent Office: 847 Days
• US Class Current: 1/1
• CPC Class Codes: H02H 9/001 limiting speed of change of electric quantities, e.g. soft switching on or off progressive control of electronic switches for eliminating interferences H03K17/16
• 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 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 3/33523 with galvanic isolation between input and output of both the power stage and the feedback loop
• CPC Class Codes: H02M 7/217 using semiconductor devices only
• CPC Class Codes: H05B 45/14 using electrical feedback from LEDs or from LED modules
• CPC Class Codes: H05B 45/37 Converter circuits
• CPC Class Codes: H05B 45/3725 Switched mode power supply [SMPS]
• CPC Class Codes: H05B 45/385 using flyback topology

Abstract

A power converter includes an energy transfer element, a power switch, a controller and a leading edge dimming detection circuit. The controller is coupled to control switching of the power switch to regulate the output of the power converter by controlling a transfer of energy through the energy transfer element. The leading edge dimming detection circuit is coupled to generate a control signal in response to detecting leading edge dimming at the input of the power converter. In one aspect, the leading edge dimming detection circuit detects the leading edge dimming and then generates a control signal to engage a compensator which maintains the input current of the power converter to be equal to or greater than a minimum current. In another aspect, the leading edge dimming detection circuit detects and reutilizes the turn-on current spike energy of a leading edge dimmer.

Claims

1. A power converter, comprising:

an energy transfer element coupled between an input and an output of the power converter;

a power switch coupled to the energy transfer element to control a transfer of energy between the input and the output of the power converter;

a controller coupled to control switching of the power switch to regulate an output of the power converter;

a leading edge dimming detection circuit coupled to generate a control signal in response to detecting leading edge dimming at the input of the power converter; and

a damper circuit coupled to suppress a spike in an input current of the power converter, wherein the spike in the input current corresponds with a turn-on event of an input voltage of the power converter by a leading edge dimming circuit that is to be coupled to the input of the power converter, wherein the leading edge dimming detection circuit further includes a spike energy reclamation circuit coupled to the damper circuit to store energy generated by the spike in the input current and to generate the control signal in response thereto.

2. The power converter of claim 1, further comprising:

a compensator coupled to the input of the power converter; and

a control switch coupled to selectively engage the compensator in response to the control signal indicating the detection of leading edge dimming, wherein, when engaged, the compensator is coupled to maintain an input current of the power converter to be equal to or greater than a minimum current.

3. A power converter, comprising:

an energy transfer element coupled between an input and an output of the power converter;

a power switch coupled to the energy transfer element to control a transfer of energy between the input and the output of the power converter;

a controller coupled to control switching of the power switch to regulate an output of the power converter;

a leading edge dimming detection circuit coupled to generate a control signal in response to detecting leading edge dimming at the input of the power converter;

a compensator coupled to the input of the power converter; and

a control switch coupled to selectively engage the compensator in response to the control signal indicating the detection of leading edge dimming, wherein, when engaged, the compensator is coupled to maintain an input current of the power converter to be equal to or greater than a minimum current,

wherein the leading edge dimming detection circuit is coupled to detect a current spike in a rectified input current of the power converter, and to generate the control signal to engage the compensator in response thereto, wherein the current spike corresponds with the turning on of an input voltage of the power converter by a dimming circuit during leading edge dimming, and wherein the leading edge dimming detection circuit comprises a current sense resistance coupled such that the rectified input current flows through the current sense resistance to develop a first voltage across the current sense resistance.

4. The power converter of claim 3, wherein the minimum current is equal to a holding current threshold of a dimmer circuit that is coupled to the input of the power converter.

5. The power converter of claim 3, wherein the control signal keeps the compensator disengaged in response to trailing edge dimming and in response to the absence of dimming at the input of the power converter.

6. The power converter of claim 3, wherein the compensator is coupled to draw a compensation current from the input of the power converter, wherein the compensator comprises a bulk capacitance module.

7. The power converter of claim 6, wherein the bulk capacitance module consists of a capacitance coupled such that the compensation current flows through the capacitance.

8. The power converter of claim 3, wherein the compensator is coupled to draw a compensation current from the input of the power converter, wherein the compensator comprises a current sink.

9. The power converter of claim 8, wherein the current sink comprises:

a resistance; and

a capacitance coupled to the resistance such that the compensation current flows through the resistance and through the capacitance.

10. The power converter of claim 8, wherein the current sink comprises:

a resistance having a first terminal and a second terminal;

a first capacitance having a third terminal and a fourth terminal, wherein the second terminal of the resistance is coupled to the third terminal of the first capacitance; and

a second capacitance having a fifth terminal and a sixth terminal, wherein the first terminal of the resistance is coupled to the fifth terminal of the second capacitance and the fourth terminal of the first capacitance is coupled to the sixth terminal of the second capacitance.

11. The power converter of claim 10, wherein the second capacitance has a capacitance value greater than a capacitance value of the first capacitance.

12. The power converter of claim 3, wherein the compensator is coupled to the control switch such that a compensation current flows through the compensator and through the control switch between a first node and a second node of the power converter when the compensator is engaged, wherein the current sense resistance is coupled between the second node and an input circuit of the power converter.

13. The power converter of claim 12, wherein the current sense resistance functions to detect the current spike for the leading edge dimming detection circuit and functions as a damper resistor to limit the current spike in the rectified input current.

14. The power converter of claim 12, wherein the leading edge dimming detection circuit further comprises a capacitance coupled to be charged in response to the first voltage developed across the current sense resistance, wherein the control signal is generated in response to a second voltage across the capacitance.

15. The power converter of claim 14, wherein the control signal controls the control switch to engage the compensator when the second voltage is above a threshold voltage of the control switch.

16. A power converter, comprising:

an energy transfer element coupled between an input and an output of the power converter;

a power switch coupled to the energy transfer element to control a transfer of energy between the input and the output of the power converter;

a controller coupled to control switching of the power switch to regulate an output of the power converter;

a damper circuit coupled to suppress a spike in an input current of the power converter, wherein the spike in the input current corresponds with a turn-on event of an input voltage of the power converter by a leading edge dimming circuit that is to be coupled to the input of the power converter; and

a leading edge dimming detection circuit coupled to generate a control signal in response to detecting leading edge dimming at the input of the power converter, wherein the leading edge dimming detection circuit further includes a spike energy reclamation circuit coupled to the damper circuit to store energy generated by the spike in the input current and to generate the control signal in response thereto.

17. The power converter of claim 16, wherein the damper circuit is an active damper circuit coupled to be selectively engaged to suppress the spike in the input current for only a portion of the turn-on event.

18. The power converter of claim 17, wherein the energy stored by the spike energy reclamation circuit is generated during the portion of the turn-on event that the active damper circuit is engaged.

19. The power converter of claim 16, further comprising an active bleeder circuit coupled to be engaged to maintain the input current of the power converter to be equal to or greater than a minimum current in response to the control signal indicating the presence of leading edge dimming.

20. The power converter of claim 19, wherein the minimum current is equal to a holding current threshold of the dimming circuit.

21. The power converter of claim 16, wherein a magnitude of the stored energy and of the control signal is responsive to an amount of dimming by the dimming circuit at the input of the power converter.

22. The power converter of claim 21, wherein the controller includes a feedback terminal coupled to receive a feedback current that is representative of the output of the power converter, wherein the control signal generated by the spike energy reclamation circuit is a compensation current that is added to the feedback current to emulate an increase in the output of the power converter, such that the controller increases the input current of the power converter.

23. The power converter of claim 21, wherein the magnitude of the stored energy and of the control signal increases with increases in a phase angle of voltage removed from the input voltage by the dimming circuit when the phase angle is between zero (0) and ninety (90) degrees.

24. The power converter of claim 23, wherein the magnitude of the stored energy and of the control signal decreases with decreases in the phase angle of voltage removed from the input voltage by the dimming circuit when the phase angle is between ninety (90) and one hundred eighty (180) degrees.

25. The power converter of claim 21, wherein the damper circuit includes a first terminal and a second terminal, the spike energy reclamation circuit including:

a first diode having an anode coupled to the first terminal of the damper circuit; and

a storage capacitor having a third terminal coupled to a cathode of the first diode and a fourth terminal coupled to the second terminal of the damper circuit, wherein the signal is responsive to a first voltage across the storage capacitor.

26. The power converter of claim 25, wherein the damper circuit includes a damper resistance, wherein the first and second terminals of the damper circuit are terminals of the damper resistance.

27. The power converter of claim 25, wherein the spike energy reclamation circuit further comprises an averaging capacitor coupled to generate a second voltage across the averaging capacitor with respect to an input return of the power converter, wherein the second voltage is an average of the first voltage over several line cycles of the input voltage, wherein the magnitude of the control signal is representative of the second voltage across the averaging capacitor.

28. The power converter of claim 27, wherein the spike energy reclamation circuit further comprises:

a second diode having a cathode coupled to the averaging capacitor; and

a resistance having one terminal coupled to the storage capacitor and another terminal coupled to an anode of the second diode.

29. The power converter of claim 27, wherein the averaging capacitor has a capacitance value greater than a capacitance value of the storage capacitor.