LLC series resonant DC-to-DC converter

• US 6,344,979 B1
• Filed: 02/09/2001
• Issued: 02/05/2002
• Est. Priority Date: 02/09/2001
• Status: Expired due to Term

• Current Assignee: Delta Electronics Incorporated
• Original Assignee: Delta Electronics Incorporated
• Inventors: Zhang, Alpha J., Gu, Yilei, Huang, Guisong
• Primary Examiner(s): STERRETT, JEFFREY L
• Application Number:
  US09/780,128
• Time in Patent Office: 361 Days
• Field of Search: 363/15, 363/16, 363/17, 363/39, 363/40, 363/131, 363/132
• US Class Current: 363/16
• CPC Class Codes: H02M 3/01 Resonant DC/DC converters
• CPC Class Codes: H02M 3/33571 Half-bridge at primary side of an isolation transformer
• CPC Class Codes: H02M 3/33573 Full-bridge at primary side of an isolation transformer
• CPC Class Codes: H02M 3/3382 in a push-pull circuit arrangement
• 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

The present invention discloses a DC-to-DC converter. The DC-to-DC converter includes a square wave generator for generating a sequence of output voltages having a waveform of square wave. The DC-to-DC converter further includes a resonant tank connected to the square wave generator comprising a series capacitor connected to a series inductor and a parallel inductor. The DC-to-DC converter further includes a transformer having a primary side connected in series with the series inductor and connected in parallel to the parallel inductor. The transformer further includes a secondary side for connecting to a rectifying circuit for providing a rectified DC voltage to an output load circuit. The series capacitor functioning with the series inductor to provide a first characteristic resonant frequency represented by ƒ_s, and the series capacitor functioning with the series inductor and the parallel inductor to provide a second characteristic resonant frequency represented by ƒ_m wherein ƒ_s>ƒ_m. The converter runs at variable frequency switching to perform output regulation. The converter features high conversion efficiency at high input operation by switching at frequency between the first and second characteristic resonant frequency. In a preferred embodiment, the parallel inductor is integrated to transformer as primary magnetizing inductor and in further the series inductor may also be integrated into transformer.

Claims

1. A DC-to-DC converter comprising:

a square wave generator for generating a sequence of output voltages having a waveform of square wave;

a resonant tank connected to said square wave generator comprising a series capacitor connected to a series inductor and a parallel inductor;

a transformer having a primary side connected in series with said series inductor and connected in parallel to said parallel inductor;

said transformer further including a secondary side for connecting to a rectifying circuit for providing a rectified DC voltage to an output load circuit;

said rectifier circuit further comprising a filtering capacitor for filtering said rectified DC voltage outputted to said output load circuit;

said series capacitor functioning with said series inductor to provide a first characteristic resonant frequency represented by ƒ

_s, and said series capacitor functioning with said series inductor and said parallel inductor to provide a second characteristic resonant frequency represented by ƒ

_m wherein ƒ

_s>

ƒ

_m;

said converter operating in the frequency range that is higher than said second frequency ƒ

_m.

2. The DC-to-DC converter of claim 1 wherein:

when the operation frequency of said DC-to-DC converter is between said first and said second frequency, ƒ

_m<

ƒ

<

ƒ

_s, the switches in said square wave generator operate under zero-voltage-switching condition and the rectifiers in said rectifier circuit operate under zero-current-switching condition.

3. The DC-to-DC converter of claim 1 wherein:

said rectifying circuit comprises a center-tapped rectifying circuit.

4. The DC-to-DC converter of claim 1 wherein:

said rectifying circuit comprises a full-bridge rectifying circuit.

5. The DC-to-DC converter of claim 1 wherein:

said parallel inductor is implemented as an external inductor.

6. The DC-to-DC converter of claim 1 wherein:

said parallel inductor is implemented as a magnetizing inductance of said transformer.

7. The DC-to-DC converter of claim 1 wherein:

said series inductor is implemented as an external inductor.

8. The DC-to-DC converter of claim 1 wherein:

said series inductor is implemented as a leakage inductance of said transformer.

9. The DC-to-DC converter of claim 1 wherein:

said square wave generator comprises a first switch and a second switch complimentary to said first switch for alternately turning on and off for generating said square wave voltage.

10. The DC-to-DC converter of claim 1 wherein:

said square wave generator comprises four switches connected as a full-bridge structure for generating square wave voltage.

11. The DC-to-DC converter of claim 1 wherein:

said square wave generator comprises two half-bridges connected in series for generating square wave voltage.

12. A resonant tank connected to the primary winding of the transformer in a DC-to-DC converter comprising:

a series capacitor connected to a series inductor and a parallel inductor in series;

said parallel inductor connected to the primary winding of the transformer in parallel;

said series capacitor functioning with said series inductor to provide a first characteristic resonant frequency represented by ƒ

_s, and said series capacitor functioning with said series inductor and said parallel inductor to provide a second characteristic resonant frequency represented by ƒ

_m wherein ƒ

_s>

ƒ

_m; and

said DC-to-DC converter operating in a frequency range higher than said secondary frequency ƒ

_m.

13. The resonant tank of claim 12 wherein:

said parallel inductor is integrated into the magnetizing inductance of the transformer.

14. The resonant tank of claim 12 wherein:

said series inductor is integrated into the leakage inductance of the transformer.