Secondary side hybrid converter apparatus and method

Patent metadata

Field	Value
Publication number	US-9595877-B2
Application number	US-201414500486-A
Country	US
Kind code	B2
Filing date	Sep 29, 2014
Priority date	Sep 29, 2014
Publication date	Mar 14, 2017
Grant date	Mar 14, 2017

Abstract

An apparatus comprises an isolated power converter coupled to an input dc power source, wherein the isolated power converter comprises a primary switching network operating at a fixed switching frequency, a secondary resonant tank including a dc blocking capacitor and a rectifier having two input terminals coupled to the secondary resonant tank, an output capacitor coupled between a first output terminal of the rectifier and a load and a dc/dc converter coupled between a second output terminal of the rectifier and the load.

First claim

What is claimed is:

1. An apparatus comprising:
an isolated power converter coupled to an input dc power source, wherein the isolated power converter comprises:
a primary switching network operating at a fixed switching frequency;
a secondary resonant tank including a dc blocking capacitor; and
a rectifier having two input terminals coupled to the secondary resonant tank, wherein the rectifier comprises two legs, and wherein a first leg comprises two switching elements connected in series and a second leg comprises two elements connected in series, and wherein a common node of the two switching elements is connected to a first input terminal of the rectifier and a common node of the two elements of the second leg is connected to a second input terminal of the rectifier;

an output capacitor coupled between a first output terminal of the rectifier and a load; and
a dc/dc converter coupled between a second output terminal of the rectifier and the load, wherein the dc/dc converter has an input directly connected to the first leg and an output directly connected to the second leg.

2. The apparatus of claim 1 , wherein:
the dc/dc converter is a four-switch buck-boost converter; and
the isolated power converter is an inductor-inductor-capacitor (LLC) resonant converter.

3. The apparatus of claim 1 , wherein:
the dc/dc converter is configured to operate at a PWM mode.

4. The apparatus of claim 3 , wherein:
the dc/dc converter is configured to operate at a buck converter mode in response to a first input voltage and operate at a boost converter mode in response to a second input voltage, wherein the first input voltage is higher than the second input voltage.

5. The apparatus of claim 1 , wherein:
an average voltage across the dc blocking capacitor is approximately equal to one half of a difference between a voltage across the load and a voltage of the second output terminal of the rectifier.

6. The apparatus of claim 1 , wherein:
a gain of the isolated power converter is approximately equal to 1.

7. The apparatus of claim 1 , wherein:
the dc/dc converter comprises an input capacitor, a first switch, a second switch, a third switch, a fourth switch and an inductor.

8. The apparatus of claim 7 , wherein:
the input capacitor is coupled between the second output terminal of the rectifier and ground;
the first switch and the second switch are connected in series and further coupled between two terminals of the input capacitor of the dc/dc converter;
the third switch and the fourth switch are connected in series and further coupled between two terminals of the output capacitor; and
the inductor is between a common node of the first switch and the second switch, and a common node of the third switch and the fourth switch.

9. The apparatus of claim 7 , wherein:
the rectifier comprises a first secondary switch, a second secondary switch, a third secondary switch and a fourth secondary switch; and
the secondary resonant tank comprises a resonant inductor connected in series with the dc blocking capacitor.

10. The apparatus of claim 9 , wherein:
the secondary resonant tank comprises:
two inputs coupled to a secondary side transformer winding of the isolated power converter;
a first output coupled to a common node of the first secondary switch and the second secondary switch; and

a second output coupled to a common node of the third secondary switch and the fourth secondary switch;
the first secondary switch and the second secondary switch are connected in series and further coupled between two terminals of the input capacitor of the dc/dc converter; and
the third secondary switch and the fourth secondary switch are connected in series and further coupled between two terminals of the output capacitor.

11. A system comprising:
an isolated power converter coupled to an input dc power source, wherein the isolated power converter is an unregulated inductor-inductor-capacitor (LLC) resonant converter and the unregulated LLC resonant converter comprises:
a secondary resonant tank including a dc blocking capacitor; and
a rectifier having two input terminals coupled to the secondary resonant tank, wherein the rectifier comprises a first leg having two switching elements connected in series and a second leg having two elements connected in series, and wherein a bottom terminal of the first leg is directly connected to a bottom terminal of the second leg;

an output capacitor coupled between a first output terminal of the rectifier and a load, wherein the first output terminal of the rectifier is an upper terminal of the second leg; and
a dc/dc converter coupled between a second output terminal of the rectifier and the load, wherein the second output terminal of the rectifier is an upper terminal of the first leg, and wherein:
the dc/dc converter is configured to operate at a buck converter mode when an input voltage from the input dc power source is higher than a voltage threshold; and
the dc/dc converter is configured to operate at a boost converter mode when the input voltage from the input dc power source is lower than the voltage threshold.

12. The system of claim 11 , wherein:
a power delivered by the dc/dc converter is a fraction of a power delivered by the isolated power converter.

13. The system of claim 11 , wherein the LLC resonant converter is configured to:
operate in a duty cycle approximately equal to 50%; and
operate at a fixed frequency.

14. The system of claim 11 , wherein:
the dc/dc converter is a regulated four-switch buck-boost converter.

15. The system of claim 11 , wherein:
the secondary resonant tank comprises a resonant inductor connected in series with the dc blocking capacitor; and
the rectifier comprises a first secondary switch, a second secondary switch, a third secondary switch and a fourth secondary switch, and wherein:
the first secondary switch and the second secondary switch are connected in series and further coupled between two input terminals of the dc/dc converter; and
the third secondary switch and the fourth secondary switch are connected in series and further coupled between two output terminals of the dc/dc converter.

16. A method comprising:
providing a serial hybrid converter comprising:
an isolated power converter coupled to an input dc power source, wherein the isolated power converter comprises:
a primary switching network operating at a fixed switching frequency;
a secondary resonant tank including a dc blocking capacitor; and
a rectifier having two input terminals coupled to the secondary resonant tank, and wherein the rectifier comprises a first leg having two switching elements connected in series and a second leg having two elements connected in series;

an output capacitor coupled between a first output terminal of the rectifier and a load; and
a dc/dc converter coupled between a second output terminal of the rectifier and the load, wherein an upper terminal of the first leg is connected to the load through the dc/dc converter and an upper terminal of the second leg is directly connected to the load;

configuring the dc/dc converter to operate at a buck converter mode in response to a first input voltage; and
configuring the dc/dc converter to operate at a boost converter mode in response to a second input voltage, wherein the first input voltage is higher than the second input voltage.

17. The method of claim 16 , further comprising:
configuring the isolated power converter to operate at a fixed switching frequency, wherein the isolated power converter is an unregul

Assignees

• Futurewei Technologies Inc

Inventors

• Dai Heping
• Fu Dianbo
• Ye Liming
• Chen Daoshen

Classifications

• H02M2001/0058

  Electricity · mapped topic

• H02M3/33576 Primary

  having at least one active switching element at the secondary side of an isolation transformer · CPC title

• H02M1/0058

  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 title

• Y02B70/10

  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 title