Soft switching DC-DC converter including a buck converter and a boost converter sharing a common transformer

• US 7,551,462 B2
• Filed: 02/07/2006
• Issued: 06/23/2009
• Est. Priority Date: 02/08/2005
• Status: Expired due to Fees

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Uruno, Junpei, Kanouda, Akihiko, Shoji, Hiroyuki, Kaminaga, Yasuo
• Primary Examiner(s): Ullah; Akm E
• Assistant Examiner(s): WILLIAMS, ARUN C
• Application Number:
  US11/348,348
• Publication Number:
  US 20060176719A1
• Time in Patent Office: 1,232 Days
• Field of Search: 363/21.02, 363/89, 363/95, 363/97
• US Class Current: 363/89
• CPC Class Codes: H02M 1/342 Active non-dissipative snubbers
• CPC Class Codes: H02M 3/158 including plural semiconductor devices as final control devices for a single load
• 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

A soft switching DC-DC converter is provided which includes circuitry for both a buck converter and a boost converter. The buck converter circuitry and the boost converter circuitry share a common transformer including a primary coil and first and second secondary coils. A first switching element is coupled to a first capacitor to provide the buck converter operation while another switching element is provided to provide the boost converting operation. The primary coil of the transformer is commonly used as a choke coil by both the buck converter and the boost converter. In this way, size and cost reduction can be obtained.

Claims

1. A soft switching DC-DC converter for converting an input voltage into another voltage, the converter including a resonant circuit,

wherein the DC-DC converter comprises a buck converter wherein:

a first terminal of a rectification circuit of a power source is connected with a first terminal of a first switching element having a control terminal for controlling a main electric current,

a second terminal of the first switching element and a first terminal of a primary coil of a transformer, comprising the primary coil and a first secondary coil and a second secondary coil, are connected together,

a second terminal of the primary coil of the transformer is connected to a first terminal of a first capacitor,

a second terminal of the first switching element and a first terminal of a first diode are connected together,

a second terminal of the first diode and a second terminal of the rectification circuit are connected together,

a second terminal of the first capacitor and the second terminal of the rectification circuit are connected together,

a second diode and a second capacitor are connected in parallel to the first switching element,

the first terminal of the first switching element and a first terminal of a third diode are connected together,

a second terminal of the third diode is connected with a first terminal of a second switching element having a control terminal for controlling the main electric current,

a second terminal of the second switching element and a first terminal of the first secondary coil of the transformer are connected together,

a second terminal of the first secondary coil of the transformer and the second terminal of the first switching element are connected together, and

wherein the DC-DC converter includes a boost converter wherein;

a second terminal of the primary coil of the transformer is connected with a first terminal of a third switching element having a control terminal for controlling the main electric current,

a second terminal of the third switching element and a second terminal of the rectification circuit are connected together,

the first terminal of the third switching element and a first terminal of a fourth diode are connected together,

a second terminal of the fourth diode and a first terminal of the first capacitor are connected together,

a fifth diode and a third capacitor are connected in parallel to the third switching element,

the first terminal of the third switching element and a first terminal of the second secondary coil of the transformer are connected together,

a second terminal of the second secondary coil of the transformer and a first terminal of a sixth diode are connected together,

a second terminal of the sixth diode is connected with a first terminal of a fourth switching element having a control terminal for controlling the main electric current, and

a second terminal of the fourth switching element and the second terminal of the rectification circuit are connected together, and

wherein the primary coil and the first and second secondary coils are formed from one transformer and wherein the primary coil of the one transformer is commonly used as a choke coil of the boost converter and the buck converter to thereby provide soft switching for the first, second, third and fourth switches, and

further comprising at least one drive circuit for controlling on/off operations of the first switching element to provide a buck converting operation for the input voltage while fixing said third switching element to be off and for controlling on/off operations of the third switching element to provide a boost converting operation for the input voltage, while fixing said first switching element to be off.