Single-stage AC-DC power converter with flyback PFC and selectable dual output current
View Patent ↗A single-stage AC-DC power converter for powering a load at a substantially constant current, and related methods and systems. The AC-DC power converter includes a high power factor correction (PFC) circuit configured in a flyback topology and operating in transition mode. The flyback PFC circuit outputs a direct current (DC) voltage and a DC current. The PFC circuit further includes a flyback transformer and a switch circuit that selectably toggles the substantially constant output current provided to the load between a first and a second, preset constant current. The secondary windings of the flyback transformer are split into two sections, and the switch circuit toggles the two sections of the secondary windings between a series and a parallel configuration to provide the first and second, preset constant currents. The switch circuit includes a switch and three, fast Schottky diodes.
1. A single stage AC-DC power converter for powering a load at a substantially constant current, comprising:
a high power factor correction (PFC) circuit configured in a flyback topology operating in transition mode;
wherein the flyback PFC circuit is connected to an alternating current (AC) power supply and configured to output a direct current (DC) voltage and a DC current; and
wherein the flyback PFC circuit further comprises a flyback transformer and a switch circuit that selectably toggles the substantially constant output current provided to the load wherein when the switch circuit is closed, the constant output current is equal to a first, preset constant current, and when the switch circuit is open the constant output current is equal to a second, preset constant current which is equal to twice the first preset constant current, and wherein the DC voltage output is greater when the switch circuit is closed than when the switch circuit is open.
2. The single stage AC-DC power converter of claim 1 , wherein the flyback transformer comprises a primary winding and a secondary winding, the secondary winding being split into two equal, halved sections of bifilar windings.
3. The single stage AC-DC power converter of claim 2 , wherein the switch circuit toggles between a first configuration in which the two sections of the secondary winding are in series and a second configuration in which the two sections of the secondary winding are in parallel, wherein, when the two sections of the secondary winding are in series, the first, preset constant current is provided to the load, and wherein, when the two sections of the secondary winding are in parallel, the second, preset constant current is provided to the load.
4. The single stage AC-DC power converter of claim 1 , wherein the switch circuit includes a switch and three, fast Schottky diodes, wherein, when the switch is in a closed position, the two sections of the secondary winding are in series with each other and wherein, when the switch is in an open position, the two sections of the secondary winding are in parallel with each other.
5. The single stage AC-DC power converter of claim 1 , wherein the flyback PFC circuit further comprises a controller and wherein the controller sets the second, preset constant current.
6. The single stage AC-DC power converter of claim 1 , wherein the AC-DC power converter is a light emitting diode (LED) driver and the load is an LED load.
7. The single stage AC-DC power converter of claim 1 , wherein the switch circuit is placed across output of the flyback transformer.
8. A method for powering a load at a substantially constant current using a single stage AC-DC power converter, comprising:
receiving an alternating current (AC) voltage from an AC power supply;
converting the AC voltage into a direct current (DC) voltage and a DC current; providing the DC voltage and the DC current to a high power factor correction (PFC) circuit configured in a flyback topology, the flyback PFC circuit operating in transition mode and having a flyback transformer and a switch circuit; and
wherein when the switch circuit is closed, setting the output current provided to the load at a first, preset constant current, and wherein when the switch circuit is open setting the output current to a second, preset constant current, which is equal to twice the first preset constant current, and wherein the DC voltage output is greater when the switch circuit is closed than when the DC voltage output when the switch circuit is open.
9. The method of claim 8 , wherein the flyback transformer comprises a primary winding and a secondary winding, further comprising splitting the secondary winding into two sections of equal halves, wherein the step of setting the output current provided to the load at either the first, preset constant current or the second, preset constant current further comprises toggling the switch circuit between a first configuration in which the two sections of the secondary winding are in series and a second configuration in which the two sections of the secondary winding are in parallel.
10. The method of claim 9 , wherein the step of configuring the two sections of the secondary winding in series further comprises providing the first, preset constant current to the load and wherein the step of configuring the two sections of the secondary winding in parallel further comprises providing the second, preset constant current to the load.
11. The method of claim 10 , wherein the switch circuit includes a switch and three, fast Schottky diodes, wherein closing the switch causes the flyback PFC circuit to be in the first configuration in which the two sections of the secondary winding are in series and wherein opening the switch causes the flyback PFC circuit to be in the second configuration in which the two sections of the secondary winding are in parallel.
12. A system for powering a load at a substantially constant current, comprising:
an alternating current (AC) power supply that provides an AC input voltage and an AC input current; and a single stage AC-DC power converter having a high power factor correction (PFC) circuit configured in a flyback topology and operating in transition mode;
wherein the flyback PFC circuit is connected to the AC power supply and configured to output a direct current (DC) voltage and a DC current; and
wherein the flyback PFC circuit further comprises a flyback transformer and a switch circuit that selectably toggles the substantially constant output current provided to the load wherein when the switch circuit is closed, the constant output current is equal to a first, preset constant current, and when the switch circuit is open the constant output current is equal to a second, preset constant current which is equal to twice the first preset constant current, and wherein the DC voltage output is greater when the switch circuit is closed than when the switch circuit is open.
13. The system of claim 12 , wherein the flyback transformer comprises a primary winding and a secondary winding, the secondary winding being split into two sections of two equal halves.
14. The system of claim 12 , wherein the switch circuit includes a switch and three, fast Schottky diodes.
15. The system of claim 14 , wherein, when the switch is in a closed position, the two sections of the secondary winding are in series with each other and, when the switch is in an open position, the two sections of the secondary winding are in parallel with each other.
16. The system of claim 12 , wherein the single AC-DC power converter further comprises a controller and wherein the controller sets the second, preset constant current.
17. The system of claim 12 , wherein the AC-DC power converter is a light emitting diode (LED) driver and the load is an LED load.
18. A system for powering a load at a substantially constant current, comprising:
an alternating current (AC) power supply that provides an AC input voltage and an AC input current; and
a single stage AC-DC power converter having high power factor correction (PFC) circuit configured in a flyback topology and operating in transition mode;
wherein the flyback PFC circuit is connected to the AC power supply and configured to output a direct current (DC) voltage and a DC current; and
wherein the flyback PFC circuit further comprises a flyback transformer and a switch circuit that selectably toggles the substantially constant output current provided to the load wherein when the switch circuit is closed, the constant output current is equal to a first, preset constant current, and when the switch circuit is open the constant output current is equal to a second, preset constant current which is equal to twice the first preset constant current, and wherein the DC voltage output is greater when the switch circuit is closed than when the switch circuit is open;
wherein the switch circuit toggles between a first configuration in which two sections of a secondary winding are in series when the switch circuit is closed and a second configuration in which the two sections of the secondary winding are in parallel when the switch circuit open.
19. The system of claim 18 , wherein,
when the two sections of the secondary winding are in series, the flyback PFC circuit provides the first, preset constant current to the load and,
when the two sections of the secondary winding are in parallel, the flyback PFC circuit provides the second, preset constant current to the load.