Multiple voltage ballast
A ballast and method for operating a ballast includes a switch or other circuit for connecting and disconnecting a voltage multiplier to a rectifier circuit. A control circuit for controlling the switch senses an input voltage and connects the voltage multiplier to the rectifier circuit when an input voltage falls below a selected voltage level.
1. A ballast comprising:
a rectifier circuit;
a multiplier component;
a switch for coupling and decoupling the multiplier component from the rectifier circuit;
an input circuit wherein the switch is configured to operate in conjunction with a voltage change at the input circuit;
a load driver coupled for receiving current from the rectifier circuit; and
a control circuit coupled between the input circuit and the switch, the control circuit including a delay circuit and a diode connected at its anode to the delay circuit, the delay circuit driving the control circuit off during initial startup of the ballast for a predetermined period, after which the diode becomes reverse biased and the control circuit operates as a function of whether an actual measured input voltage is high or low as though the delay circuit was no longer present in the control circuit.
2. The ballast of claim 1 wherein the rectifier circuit is a full wave rectifier and wherein the switch is coupled to the rectifier circuit in such a way that when the multiplier component is coupled to the rectifier circuit, the rectifier circuit is converted to a voltage doubler circuit.
3. The ballast of claim 1 wherein the multiplier component is a voltage doubler circuit.
4. The ballast of claim 1 wherein the load driver is an inverter circuit configured to drive a fluorescent lamp.
5. The ballast of claim 1 wherein the control circuit is configured to open and close the switch.
6. The ballast of claim 5 wherein the control circuit is configured to open the switch when the input voltage increases past a predetermined level.
7. The ballast of claim 5 wherein the control circuit is configured to open the switch when the input voltage is higher than 180 volts.
8. The ballast of claim 1 wherein the control circuit includes a coupling circuit.
9. The ballast of claim 8 wherein the coupling circuit includes an optical isolator.
10. The ballast of claim 8 wherein the coupling circuit includes a TRIAC.
11. The ballast of claim 1 wherein the control circuit includes an inverter stage to which the diode of the control circuit is connected.
12. The ballast of claim 8 wherein the control circuit includes a rectifier.
13. The ballast of claim 8 wherein the control circuit includes a coupling capacitor as a coupler.
14. The ballast of claim 8 wherein the control circuit includes a magnetic coupler.
15. The ballast of claim 1 wherein the switch is a TRIAC.
16. The ballast of claim 15 wherein the TRIAC is a first TRIAC and the switch includes a second TRIAC coupled to the first TRIAC.
17. The ballast of claim 16 wherein the second TRIAC is configured to be turned on by an optical signal.