Sinewave dimmer control method

• US 7,019,469 B1
• Filed: 10/21/2004
• Issued: 03/28/2006
• Est. Priority Date: 10/21/2004
• Status: Expired due to Fees

• Current Assignee: Electronic Theatre Controls Incorporated
• Original Assignee: Electronic Theatre Controls Incorporated
• Inventors: Suomi, Eric W., Rasmussen, Eric G., Thurk, John P.
• Primary Examiner(s): VU, DAVID HUNG
• Application Number:
  US10/971,682
• Time in Patent Office: 523 Days
• Field of Search: None
• US Class Current: 315/307
• CPC Class Codes: H02M 1/38 Means for preventing simultaneous conduction of switches
• CPC Class Codes: H02M 5/293 using semiconductor devices only
• CPC Class Codes: H05B 39/048 with reverse phase control
• CPC Class Codes: H05B 41/3924 by phase control, e.g. using a triac H05B41/3922 takes precedence
• CPC Class Codes: Y10S 315/04 Dimming circuit for fluorescent lamps

Abstract

An input line filter separates an ac sinusoidal power source from a power switching stage having a series switching section and a clamp switching section. Both the series switching section and a clamp switching section include complementary pairs of high power and high speed MOSFETs. The series switching section is connected in series between the input line filter and the inductor of an output load filter between the power switching stage and a load. The clamp switching section is connected to shunt the inductor and load. Synchronous operation is achieved by alternately operating the series and clamp switching sections to conductive conditions at a high pulse width modulation frequency. The duty cycle is selected to provide a sinusoidal output waveform with a desired amplitude. A microprocessor based programmable controller provides control signals for alternate conduction of the series and clamp switching sections. A dead time interval stored in memory in the controller separates the control signals for reliable and efficient operation. The dead time interval may be constant, or may be varied in accordance with load power variations.

Claims

1. A method for operating a sinewave dimmer to provide a power output signal from a power source having a varying waveform, said method comprising:

supplying a pulse width modulation signal having a duty cycle corresponding to a desired magnitude proportion of the output power signal;

alternately switching into conductive states a series circuit switch device between the power source and an integrating filter and a clamp circuit switch device shunting the integrating filter;

said switching including rendering the series circuit switch device conductive in accordance with the pulse width modulation signal and rendering the clamp circuit switch device conductive in accordance with the inverse of the pulse width modulation signal; and

separating each alternating conductive state of the series circuit switch device and the clamp circuit switch device with a dead time interval in which both the first and second circuit paths are nonconductive.

2. A method as claimed in claim 1 wherein the power output signal and the power source have sinusoidal waveforms.

3. A method as claimed in claim 2 wherein said switching and separating steps are performed by a microprocessor based programmable controller having a memory, and wherein said dead time interval is stored in the memory.

4. A method as claimed in claim 3 wherein the dead time intervals following conduction of the series circuit switch are of the same length as the dead time intervals following conduction of the clamp circuit switch.

5. A method as claimed in claim 4 wherein the pulse width modulation frequency is over about twenty kilohertz.

6. A method as claimed in claim 5 wherein the pulse width modulation frequency is about fifty kilohertz.

7. A method as claimed in claim 5 wherein the dead time interval is in the range of from about 100 to about 180 nanoseconds.

8. A method as claimed in claim 5 wherein the dead time interval is about 150 nanoseconds.

9. A method as claimed in claim 5 wherein the dead time interval is fixed.

10. A method as claimed in claim 5 further comprising feeding back output power information to the controller, and varying the dead time interval in the controller in accordance with changes in the feedback output power information.

11. A method as claimed in claim 10 wherein the dead time interval is increased when the feedback output power decreases.

12. A method for operating a sinewave dimmer to provide a power output signal from a power source having a varying waveform, said method comprising:

supplying a pulse width modulation signal having a duty cycle corresponding to a desired magnitude proportion of the output power signal;

alternately switching into conductive states a series circuit switch device between the power source and an integrating filter and a clamp circuit switch device shunting the integrating filter;

said switching including rendering the series circuit switch device conductive in accordance with the pulse width modulation signal and rendering the clamp circuit switch device conductive in accordance with the inverse of the pulse width modulation signal; and

following each conductive state of the series circuit switch device with a dead time interval in which both the first and second circuit paths are nonconductive;

said switching and following steps being performed in a microprocessor based programmable controller having memory, and said dead time interval being stored in the controller memory.

13. A synchronous sinewave dimmer for use with a load and with a power supply having an ac power supply signal, said synchronous sinewave dimmer comprising:

an input line filter for connection to the power supply;

an output load filter having an output load inductor in series with the load;

a power switching stage between said input line filter and said output load filter, said power switching stage having a series switching stage connected in series with said output load filter and with the load and a clamp switching stage connected to shunt said output load filter and the load;

a microprocessor based programmable controller having an input and memory, said controller providing series and clamp control signals for operating said series and clamp switching stages alternately in a conductive condition with a pulse width modulation duty cycle based on load power information received at said input; and

a dead time interval stored in said memory and used by said controller for separating said series and clamp control signals.

14. A synchronous sinewave dimmer as claimed in claim 13, said dead time interval being fixed.

15. A synchronous sinewave dimmer as claimed in claim 14, said dead time interval being about 150 nanoseconds.

16. A synchronous sinewave dimmer as claimed in claim 13 further comprising an output power feedback connection between the load and said controller, and said controller varying said dead time interval in accordance with changes in output power.

17. A synchronous sinewave dimmer as claimed in claim 13, said power switching stage and said clamp switching stage both including complementary pairs of MOSFETs.