LLC series resonant converter and the driving method for the synchronous rectification power switches thereof

• US 20060187686A1
• Filed: 06/21/2005
• Published: 08/24/2006
• Est. Priority Date: 02/21/2005
• Status: Active Grant

• Current Assignee: Delta Electronics Incorporated
• Original Assignee: Delta Electronics Incorporated
• Inventors: Ying, Jianping, Gan, Hongjian, Sun, Chaoqun
• Granted Patent: US 7,184,280 B2
• Time in Patent Office: Days
• US Class Current: 363/17
• CPC Class Codes: H02M 3/33592 having a synchronous rectifier circuit or a synchronous freewheeling circuit at the secondary side of an isolation transformer
• CPC Class Codes: H02M 3/3376 with automatic control of output voltage or current
• 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
• CPC Class Codes: Y02P 80/10 Efficient use of energy, e.g. using compressed air or pressurized fluid as energy carrier

Abstract

An LLC series resonant converter and a driving method for the synchronous rectification power switches thereof are provided. The LLC series resonant converter includes a bridge circuit, a resonant network, a transformer, a rectification circuit, and a frequency adjustment controller. The bridge circuit includes at least one pair of power switches. The power switches drive the resonant network. The rectification circuit includes at least one pair of synchronous rectification power switches. The synchronous rectification power switches and the power switches have a mapping relation between them. The frequency adjustment controller provides driving signals to the synchronous rectification power switches in response to the operating frequency of the LLC series resonant converter and the series resonant frequency of the resonant network, to implement synchronous rectification in the LLC series resonant converter.

Claims

1. An LLC series resonant converter, comprising:

a bridge circuit, coupled to an input voltage, comprising at least one pair of power switches;

a resonant network, coupled to the bridge circuit and being driven by the power switches;

a transformer, coupled to the resonant network;

a rectification circuit, coupled to the transformer, the transformer providing an output current of the LLC series resonant converter, wherein the rectification circuit comprises at least one pair of synchronous rectification power switches, the at least one pair of synchronous rectification power switches and the power switches of the bridge circuit have a mapping relation, corresponding one of the synchronous rectification power switches and corresponding one of the power switches are synchronously on or off; and

a frequency adjustment controller, coupled between the power switches and the synchronous rectification power switches, providing driving signals to the synchronous rectification power switches in response to the operating frequency of the LLC series resonant converter and the series resonant frequency of the resonant network, to perform synchronous rectification in the LLC series resonant converter.

2. The LLC series resonant converter according to claim 1, wherein the frequency adjustment controller provides the driving signals for the synchronous rectification power switches, according to a quantity relation of the operating frequency of the LLC series resonant converter and the series resonant frequency of the resonant network.

3. The LLC series resonant converter according to claim 2, wherein the frequency adjustment controller provides the driving signals for the synchronous rectification power switches, according to the driving signals for the power switches.

4. The LLC series resonant converter according to claim 3, wherein when the operating frequency of the present invented LLC series resonant converter is lower than the series resonant frequency of the resonant network, the driving signal of each of the synchronous rectification power switches is a constant width pulse signal which is synchronous with the driving signal of the corresponding power switch, the width of the constant width pulse signal is determined by a series resonant parameter of the resonant network;

and when the operating frequency of the LLC series resonant converter is higher than or equal to the series resonant frequency of the resonant network, the driving signal of each of the synchronous rectification power switches is the driving signal of the corresponding power switch.

5. The LLC series resonant converter according to claim 4, wherein the width of the constant width pulse signal is equal to or slightly less than a half of a series resonant period of the resonant network.

6. The LLC series resonant converter according to claim 4, wherein the frequency adjustment controller further comprises:

a pair of driving signal generators, respectively coupled between the power switches and the synchronous rectification power switches, receiving the driving signals of the corresponding power switches, and outputting the driving signals of the corresponding synchronous rectification power switches.

7. The LLC series resonant converter according to claim 6, wherein each of the driving signal generators comprises:

a synchronous signal circuit, coupled to the corresponding power switches, receiving the common driving signals for the power switches, outputting a synchronous signal synchronizing to the driving signals for the power switches;

a constant width pulse generator, coupled to the synchronous signal circuit, receiving the synchronous signal, outputting the constant width signal synchronizing to the driving signals for the power switches; and

an AND logic gate, coupled to the corresponding power switches, the constant width pulse generator and the corresponding synchronous rectification power switches, receiving the driving signals for the power switches and the constant width signals, after applying an AND logic operation on the driving signals for the power switches with the constant width pulse signal, thereby generating and outputting the driving signals for the synchronous rectification power switches.

8. The LLC series resonant converter according to claim 7, wherein a rising edge of the synchronous signals is used to trigger the constant width pulse generator and the rising edge of said the constant width pulse signal is synchronizing with the rising edge of the driving signals of said the corresponding power switches.

9. The LLC series resonant converter according to claim 7, wherein the frequency adjustment controller further comprises:

a locking circuit, coupled to the constant width pulse generators of the driving signal generators, outputting a locking signal with low voltage level to the constant width pulse generators when the operating frequency of the LLC series resonant converter is over high, causing a difficulty for driving the synchronous rectification switches, to lock the driving signals for the synchronous rectification power switches, therefore setting the synchronous rectification power switches to be off state.

10. The LLC series resonant converter according to claim 9, wherein the locking circuit uses an operating frequency checking signal to read the operating frequency of the LLC series resonant converter.

11. The LLC series resonant converter according to claim 10, wherein the operating frequency checking signal is generated by a voltage control oscillator.

12. The LLC series resonant converter according to claim 1, wherein the bridge circuit is a full-bridge circuit or a half-bridge circuit.

13. The LLC series resonant converter according to claim 1, wherein the resonant network includes a series resonant capacitor and a series resonant inductor in series connection.

14. A driving method for synchronous rectification power switches, applying for an LLC series resonant converter, the LLC series resonant converter comprising a bridge circuit, a resonant network and a rectification circuit, wherein the bridge circuit comprises at least one pair of power switches, the rectification circuit comprises at least one pair of synchronous rectification power switches, the at least one pair of synchronous rectification power switches and the power switches of the power switches have a mapping relation, corresponding one of the synchronous rectification power switches and corresponding one of the power switches are synchronously on or off, the driving method for synchronous rectification power switches comprising the steps of:

(a) obtaining the operating frequency of the LLC resonant converter;

(b) obtaining the series resonant frequency of the resonant network; and

,

(c) providing driving signals to the synchronous rectification power switches, according to the operating frequency of the LLC series resonant converter and the series resonant frequency of the resonant network, to implementing synchronous rectification in the LLC series resonant converter.

15. The driving method for synchronous rectification power switches according to claim 14, wherein the step (c) further comprises a step of:

providing the driving signal of the synchronous rectification power switches, according to a quantity relation between the operating frequency of the LLC series resonant converter and the series resonant frequency of the resonant network.

16. The driving method for synchronous rectification power switches according to claim 15, wherein the step (c) further comprises:

providing said the driving signals of the synchronous rectification power switches, according to the driving signals for the power switches.

17. The driving method for synchronous rectification power switches according to claim 16, wherein the step (c) further comprises:

when the operating frequency of the LLC series resonant converter is lower than the series resonant frequency of the resonant network, the driving signals of each synchronous rectification switch is a constant width pulse signal, synchronizing with the driving signals of the corresponding power switches, and the width of the constant width pulse signal is determined by a series resonant parameter of the resonant network; and

when the operating frequency of the LLC series resonant converter is higher than or equal to the series resonant frequency of the resonant network, the driving signal of each of the synchronous rectification power switches is the driving signals for the power switches.

18. The driving method for synchronous rectification power switches according to claim 17, wherein the width of the constant width pulse signal is equal to or slightly less than a half of a series resonant period of the resonant network.

19. The driving method for synchronous rectification power switches according to claim 17, wherein a rising edge of the constant width pulse signal is synchronizing with a rising edge of the driving signals of the corresponding power switches.

20. The driving method for synchronous rectification power switches according to claim 14, further comprising:

when the operating frequency of the LLC series resonant converter is over high, causing difficulty for driving the synchronous rectification switches, locking the driving signals for the synchronous rectification power switches, so that the synchronous rectification power switches are off state.