Multi-transformer LLC resonant converter circuits and methods

• US 8,629,627 B2
• Filed: 06/29/2010
• Issued: 01/14/2014
• Est. Priority Date: 06/29/2010
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Cohen, Isaac, Lu, Bing
• Primary Examiner(s): VU, JIMMY T
• Application Number:
  US12/826,141
• Publication Number:
  US 20110316430A1
• Time in Patent Office: 1,295 Days
• Field of Search: 315/200.R, 315/209.R, 315/224, 315/258, 315276-283, 315/291, 315/307, 363 16- 2104, 363/39, 363/40, 363/131, 363/132
• US Class Current: 315/291
• CPC Class Codes: H02M 1/0058 by employing soft switching techniques, i.e. commutation of transistors when applied voltage is zero or when current flow is zero using an auxiliary actively switched resonant commutation circuit connected to an intermediate DC voltage or between two push-pull branches of an inverter bridge H02M7/4811; in resonant inverters H02M7/4815; in inverters operating from a resonant DC source H02M7/4826
• CPC Class Codes: H02M 3/33561 having more than one ouput with independent control
• CPC Class Codes: H05B 45/382 with galvanic isolation between input and output
• CPC Class Codes: H05B 45/39 Circuits containing inverter bridges
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

In a first aspect, an LLC resonant converter is provided for driving a plurality of output circuits from a DC input signal. The LLC resonant converter includes: (a) an inverter circuit for converting the DC input signal to a square-wave signal; (b) an inductor network coupled to the inverter circuit; and (c) a plurality of transformers, each transformer including a primary winding and a secondary winding. The primary windings of the transformers are coupled in series, and the series-coupled primary windings are coupled in parallel with the inductor network. The secondary winding of each transformer is coupled to and provides a current to a corresponding one of the output circuits. The secondary winding currents are substantially equal, and power is processed by a single transformer between the DC input signal and each output circuit. Numerous other aspects are also provided.

Claims

1. An LLC resonant converter for driving a plurality of output circuits from a DC input signal, the converter comprising:

an inverter circuit for converting the DC input signal to a square-wave signal;

a single inductor network coupled to the inverter circuit; and

a plurality of transformers, each transformer including a primary winding and a secondary winding, the primary windings of the transformers coupled in series, the series-coupled primary windings directly connected in parallel with the inductor network, the secondary winding of each transformer coupled to and providing a current to a corresponding one of the output circuits;

wherein the secondary winding currents are substantially equal; and

wherein power is processed by a single transformer between the DC input signal and each output circuit and the inductor network is separately formed and independent of each single transformer.

2. The LLC resonant converter of claim 1, wherein the inductor network comprises a first inductor coupled in parallel with the series-coupled primary windings.

3. The LLC resonant converter of claim 2, wherein the inductor network further comprises a second inductor coupled in series with the series-coupled primary windings.

4. The LLC resonant converter of claim 1, wherein the inductor network comprises a discrete inductor.

5. The LLC resonant converter of claim 1, wherein the inductor network comprises integrated inductors.

6. The LLC resonant converter of claim 5, wherein the integrated inductors comprise a magnetic core comprising a center leg and a pair of outer legs.

7. The LLC resonant converter of claim 1, wherein the output circuits each comprise a string of series-coupled LEDs.

8. An LLC resonant converter circuit for driving a plurality of output circuits from a DC input signal, the converter comprising:

an inverter circuit for converting the DC input signal to a square-wave signal;

a single inductor network coupled to the inverter circuit; and

a plurality of transformers connected to the inductor network, each transformer including a primary winding and a secondary winding, the primary windings of the transformers coupled in series, the secondary winding of each transformer coupled to and providing a current to a corresponding one of the output circuits;

wherein the secondary winding currents are substantially equal; and

wherein the inductor network is separate from and independent of the plurality of transformers.

9. The LLC resonant converter of claim 8, wherein the inductor network comprises a first inductor coupled in parallel with the series-coupled primary windings.

10. The LLC resonant converter of claim 9, wherein the inductor network further comprises a second inductor coupled in series with the series-coupled primary windings.

11. The LLC resonant converter of claim 8, wherein the inductor network comprises a discrete inductor.

12. The LLC resonant converter of claim 8, wherein the inductor network comprises integrated inductors.

13. The LLC resonant converter of claim 12, wherein the integrated inductors comprise a magnetic core comprising a center leg and a pair of outer legs.

14. The LLC resonant converter of claim 8, wherein the output circuits each comprise a string of series-coupled LEDs.

15. The LLC resonant converter of claim 8, wherein the secondary winding of each transformer is coupled to and provides a current to a corresponding plurality of the output circuits.

16. A method for driving a plurality of output circuits from a DC input signal, the method comprising:

converting the DC input signal to a square-wave signal;

coupling the square wave signal via a single inductor network to a plurality of transformers, each transformer including a primary winding and a secondary winding, wherein the inductor network is separate from and independent of the plurality of transformers;

coupling the primary windings of the transformers in series;

connecting the series-coupled primary windings in parallel with the inductor network;

coupling the secondary winding of each transformer to a corresponding one of the output circuits;

providing a current from the secondary winding of each transformer to the corresponding output circuit, wherein the secondary winding currents are substantially equal; and

driving the plurality of output circuits with the LLC resonant converter.

17. The method of claim 16, wherein the inductor network comprises a first inductor, and the method further comprises coupling the first inductor in parallel with the series-coupled primary windings.

18. The method of claim 17, wherein the inductor network further comprises a second inductor, and wherein the method further comprises coupling the second inductor in series with the series-coupled primary windings.

19. The method of claim 16, wherein the inductor network comprises a discrete inductor.

20. The method of claim 16, wherein the inductor network comprises integrated inductors.