Low-cost self-oscillating driver circuit
A driver circuit for powering a load is disclosed. The driver circuit includes a self-oscillating half-bridge circuit, a resonant driver in electrical communication with the self-oscillating half-bridge circuit, and a DC voltage supply in electrical communication with the resonant driver. The self-oscillating half-bridge circuit is configured to generate a high-frequency AC signal. The resonant driver is configured to limit a current of the high-frequency AC signal and produce a limited output voltage based on the high-frequency AC signal. The DC voltage supply is configured to rectify the limited output voltage into a DC output voltage including a substantially constant current for powering the load.
1. A driver circuit for powering a load, comprising:
a self-oscillating half-bridge circuit generating a high-frequency AC signal, wherein the self-oscillating half-bridge circuit comprises a transformer including a first winding, a second winding, and a third winding, and wherein the first winding and the second winding include opposite polarities;
a resonant driver in electrical communication with the self-oscillating half-bridge circuit, the resonant driver circuit limiting a current of the high-frequency AC signal and produce a limited output voltage based on the high-frequency AC signal, the resonant driver including a capacitor connected directly to the third winding of the transformer in series, wherein the capacitor and the third winding of the transformer are connected in parallel with the load; and
a DC voltage supply in electrical communication with the resonant driver rectifying the limited output voltage into a DC output voltage including a substantially constant current for powering the load.
2. The driver circuit recited in claim 1 , wherein the DC voltage supply is a voltage doubler that includes two diodes and two capacitors, and wherein the voltage doubler doubles the limited output voltage from the resonant driver.
3. The driver circuit recited in claim 2 , wherein the two diodes are low voltage diodes having a breakdown voltage ranging from about 200 Volts to about 400 Volts.
4. The driver circuit recited in claim 1 , wherein the DC voltage supply includes a full wave rectifier and a filter capacitor.
5. The driver circuit recited in claim 4 , wherein the filter capacitor is about one microfarad.
6. The driver circuit recited in claim 5 , wherein the full wave rectifier doubles a frequency of the limited output voltage from the resonant driver.
7. The driver circuit recited in claim 1 , wherein the self-oscillating half-bridge circuit includes an upper switching element and a lower switching element that are connected in a cascade arrangement.
8. The driver circuit recited in claim 7 , wherein the upper switching element and the lower switching element are both bipolar junction transistors (BJTs).
9. The driver circuit recited in claim 1 , wherein the self-oscillating half-bridge circuit has a start-up circuit that is comprised of a resistor, a diode, a diac, and a capacitor.
10. The driver circuit recited in claim 9 , wherein the capacitor of the start-up circuit is charged during an initial start-up of the driver circuit until the diac reaches a breakover voltage.
11. The driver circuit recited in claim 1 , the resonant driver including an inductor, and wherein an inductance of the inductor and a capacitance of the capacitor are selected such that as an overall gain of the resonant driver decreases a frequency of operation also decreases.
12. The driver circuit recited in claim 11 , wherein the resonant driver further includes a buck winding that steps down a second current flowing through the third winding of the transformer.
13. A driver circuit for powering at least one light emitting diode (LED) in a non-dimming application, comprising:
a self-oscillating half-bridge circuit generating a high-frequency AC signal, the self-oscillating half-bridge circuit including an upper switching element and a lower switching element that are connected in a cascade arrangement and a transformer including a first winding, a second winding, and a third winding, and wherein the first winding and the second winding include opposite polarities;
a resonant driver in electrical communication with the self-oscillating half-bridge circuit, the resonant driver circuit limiting a current of the high-frequency AC signal and produce a limited output voltage based on the high-frequency AC signal, the resonant driver including a capacitor connected directly to the third winding of the transformer in series, wherein the capacitor and the third winding of the transformer are connected in parallel with the at least one LED; and
a DC voltage supply in electrical communication with the resonant driver and rectifying the limited output voltage into a DC output voltage including a substantially constant current for powering the at least one LED.
14. The driver circuit recited in claim 13 , wherein the DC voltage supply is a voltage doubler that includes two diodes and two capacitors.
15. The driver circuit recited in claim 14 , wherein the two diodes are low voltage diodes having a breakdown voltage ranging from about 200 Volts to about 400 Volts.
16. The driver circuit recited in claim 14 , wherein the voltage doubler doubles the limited output voltage from the resonant driver.
17. The driver circuit recited in claim 13 , wherein the DC voltage supply includes a full wave rectifier and a filter capacitor.
18. The driver circuit recited in claim 17 , wherein the filter capacitor is about one microfarad.
19. The driver circuit recited in claim 17 , wherein the full wave rectifier doubles a frequency of the limited output voltage from the resonant driver.
20. The driver circuit recited in claim 13 , wherein the upper switching element and the lower switching element are both bipolar junction transistors (BJTs).
21. The driver circuit recited in claim 13 , the resonant driver including an inductor, and wherein an inductance of the inductor and a capacitance of the capacitor are selected such that as an overall gain of the resonant driver decreases a frequency of operation also decreases.
22. The driver circuit recited in claim 21 , wherein the resonant driver further includes a buck winding that steps down a second current flowing through the third winding of the transformer.
23. A driver circuit for powering a load, comprising:
a self-oscillating half-bridge circuit to generate a high-frequency AC signal, wherein the self-oscillating half-bridge circuit has a start-up circuit that is comprised of a resistor, a diode, a diac, and a capacitor;
a resonant driver in electrical communication with the self-oscillating half-bridge circuit, the resonant driver circuit limiting a current of the high-frequency AC signal and produce a limited output voltage based on the high-frequency AC signal; and
a DC voltage supply in electrical communication with the resonant driver to rectify the limited output voltage into a DC output voltage including a substantially constant current for powering the load.
24. The driver circuit recited in claim 23 , wherein the capacitor of the start-up circuit is charged during an initial start-up of the driver circuit until the diac reaches a breakover voltage.