Method and apparatus for extending the power output range of a power converter used for a lighting system

• US 9,246,378 B2
• Filed: 07/19/2013
• Issued: 01/26/2016
• Est. Priority Date: 07/19/2013
• Status: Expired due to Fees

• Current Assignee: Microchip Technology Incorporated
• Original Assignee: Supertex Incorporated (Microchip Technology Incorporated)
• Inventors: Walker, James T.
• Primary Examiner(s): Vu, Jimmy
• Assistant Examiner(s): Chan, Wei
• Application Number:
  US13/946,933
• Publication Number:
  US 20150022105A1
• Time in Patent Office: 921 Days
• Field of Search: 363/21.15, 363/21.03, 363/21.12, 363/74, 315/297, 315/307, 315/294, 315/224, 315/185.R
• US Class Current: 1/1
• 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 1/36 Means for starting or stopping converters
• CPC Class Codes: H05B 45/10 Controlling the intensity of the light
• CPC Class Codes: H05B 45/37 Converter circuits

Abstract

A method and system for extending the power output range of a power converter used for a lighting system is disclosed.

Claims

1. A power conversion system with a delayed start time, comprising:

a voltage detector for receiving a rectified voltage; and

comparing a reference voltage and the rectified voltage to generate an output signal when the rectified voltage exceeds the reference voltage;

a delay timer configured to;

receive the output signal and generate a sink signal and an enable signal;

a power converter enabled by the enable output signal; and

a current sink circuit comprising a transistor for drawing a sink current from a source of the rectified voltage and an analog switch comprising a switch output coupled to the gate of the transistor and inputs configured to receive the sink signal, the enable signal and a voltage signal;

wherein the analog switch connects the switch output to a constant current when the power converter is not enabled and connects the switch output to a variable voltage circuit when the power converter is enabled.

2. The system of claim 1, further comprising:

a rectifier circuit for receiving an alternating current (AC) input and producing a direct current (DC) output and providing the DC output as the rectified voltage to the voltage detector.

3. The system of claim 1 wherein the power converter is enabled by the delay timer when a first time interval has elapsed after the delay timer is triggered.

4. The system of claim 3, wherein the delay timer comprises a capacitor and the first time interval is generated by a charging and discharging of the capacitor.

5. The system of claim 4, wherein the delay timer further comprises a switch that couples the capacitor to a current source in a first position and couples the capacitor to a current sink in a second position.

6. The system of claim 5, wherein the capacitor is charged during the time that the voltage detector output is off due to AC input not being present, and said capacitor is discharged during the time that said voltage detector output is on due to AC input being present.

7. The system of claim 6, wherein the capacitor charge and discharge currents have different values.

8. The system of claim 6, wherein the power converter is not operated until said capacitor discharges to a predetermined voltage.

9. The system of claim 3 wherein the current sink circuit contains at least one MOSFET.

10. The system of claim 3

wherein the amount of current drawn by the current sink circuit is proportional to a control voltage.

11. A dimmer for use with a lighting system, comprising:

a rectifier circuit for receiving an alternating current (AC) input and producing a direct current (DC) output;

a voltage detector for generating an output signal when the DC output exceeds a threshold voltage;

a delay timer configured to;

receive the output signal and generate a sink signal and an enable signal;

a power converter enabled by the enable signal; and

a current sink circuit comprising a transistor for drawing a sink current from a source of the rectified voltage and an analog switch comprising a switch output coupled to the gate of the transistor and inputs configured to receive the sink signal, the enable signal and a voltage signal;

wherein the analog switch connects the switch output to a constant current when the power converter is not enabled and connects the switch output to a variable voltage circuit when the power converter is enabled.

12. The system of claim 11, wherein the power converter is enabled by the delay timer when a first time interval has elapsed after the delay timer is triggered.

13. The system of claim 12, wherein the delay timer comprises a capacitor and the first time interval is generated by a charging and discharging of the capacitor.

14. The system of claim 13, wherein the delay timer further comprises a switch that couples the capacitor to a current source in a first position and couples the capacitor to a current sink in a second position.

15. The system of claim 14, wherein the capacitor is charged during the time that the voltage detector output is off due to AC input not being present, and said capacitor is discharged during the time that said voltage detector output is on due to AC input being present.

16. The system of claim 15, wherein the capacitor charge and discharge currents have different values.

17. The system of claim 15, wherein the power converter is not operated until said capacitor discharges to a predetermined voltage.

18. The system of claim 14 wherein the current sink circuit contains at least one MOSFET.

19. The system of claim 14 wherein the amount of current drawn by the current sink circuit is proportional to a control voltage.

20. A method of dimming a lighting system, comprising:

receiving, by a rectifier circuit, an alternating current (AC) input and producing a direct current (DC) output;

generating, by a voltage detector, a signal indicating that the DC output exceeds a threshold voltage;

measuring, by a delay timer, a first time interval that is initiated by the signal;

generating, by the delay timer, a sink signal and an enable signal;

enabling a power converter based on the enable signal;

providing, by the power converter, a voltage to a load; and

drawing current, by a current sink circuit, from the DC output of the rectifier circuit in response to a voltage signal, the sink signal, and the enable signal when the power converter is not enabled.

21. The method of claim 20, wherein the load comprises a light emitting diode (LED) system.

22. The method of claim 20 further comprising a timer system for reducing the power converter operation time in proportion to the dimmer phase angle information.

23. The method of claim 20, wherein the load comprises at least one of the following:

an incandescent lamp, a compact fluorescent lamp (CFL), or an electrolumanescent panel.