Granted Patent B2

US 7,015,679 · App. 10/741,055 · Granted Mar 21, 2006

Abstract

Claims (29)

1. A circuit for supplying an electrical a.c. load with a voltage that may be varied, the circuit comprising:

a control signal input for receiving a switching control signal to control load output voltage;

first and second circuit output terminals for connection across the load;

first switch means having an input coupled to the control signal input and having an output coupled between one of the first and second circuit output terminals and a first a.c. line terminal; and

second switch means having an input coupled to the first switch means and having an output coupled between the first and second circuit output terminals and coupled to a second a.c.line terminal,

the first and second switch means being arranged to be switched by the complementarily.

2. The circuit of claim 1 wherein at least one of the first and second switch means comprises:

transistor means coupled to the switch means and having a control electrode coupled to the switch means input and having other electrodes; and

rectifier bridge means having first terminals coupled to the other electrodes of the transistor means, and having second terminals coupled to the output.

3. The circuit of claim 1 further comprising flip-flop means coupled between the first switch means and the second switch means.

4. The circuit of claim 3 wherein the flip-flop means comprises transistor means, resistor means and capacitor means arranged to provide closed loop operation.

5. The circuit of claim 4 wherein a time constant of the resistor means and the capacitor means is arranged to produce bistable flip-flop operation at a desired operation frequency.

6. The circuit of claim 1 further comprising filter means coupled between the first switch means and the second switch means.

7. The circuit of claim 1 wherein the control signal input is arranged to receive a pulse width modulated switching control signal.

8. An integrated circuit comprising substantially the circuit of claim 1 .

9. A method for supplying a variable voltage to an electrical a.c. load, the method comprising:

providing a control signal input for receiving a switching control signal to control load output voltage;

providing first and second circuit output terminals for connection across the load;

providing first switch means having an input coupled to the control signal input and having an output coupled between one of the first and second circuit output terminals and a first a.c. line terminal;

providing second switch means having an input coupled to the first switch means and having an output coupled between the first and second circuit output terminals and coupled to a second a.c. line terminal; and

providing a switching control signal to the control signal input to switch the first and second switch means complementarily.

10. The method of claim 9 wherein at least one of the first and second switch means comprises:

transistor means coupled to the switch means and having a control electrode coupled to the switch means input and having other electrodes; and

rectifier bridge means having first terminals coupled to the other electrodes of the transistor means, and having second terminals coupled to the output.

11. The method of claim 9 further comprising providing flip-flop means coupled between the first switch means and the second switch means.

12. The method of claim 11 wherein the flip-flop means comprises transistor means, resistor means and capacitor means arranged to provide closed loop operation.

13. The method of claim 12 wherein a time constant of the resistor means and the capacitor means is arranged to produce bistable flip-flop operation at a desired operation frequency.

14. The method of claim 9 further comprising providing filter means coupled between the first switch means and the second switch means.

15. The method of claim 9 wherein the control signal is a pulse width modulated signal.

Assignments (10)