Soft switching DC-DC converter

• US 20060176719A1
• Filed: 02/07/2006
• Published: 08/10/2006
• Est. Priority Date: 02/08/2005
• Status: Active Grant

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Kanouda, Akihiko, Shoji, Hiroyuki, Kaminaga, Yasuo, Uruno, Junpei
• Granted Patent: US 7,551,462 B2
• Time in Patent Office: Days
• 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

The present invention relates to a soft switching DC-DC converter. A soft switching DC-DC converter comprises a first switching element having a first terminal connected to an input side and having a control terminal for controlling a main electric current; a first diode having a first terminal connected to a second terminal of this first switching element; a primary coil of a transformer having primary and secondary coils, connected to the second terminal of the first switching element; a second diode having a first terminal connected to the first terminal of the first switching element; a second switching element having a first terminal connected to the second terminal of this second diode; and the secondary coil of the transformer, having a first terminal connected to a second terminal of this second switching element, and having a second terminal connected to the second terminal of the first switching element. The soft switching DC-DC converter allows a substantial reduction of the loss in the capacitor operation, by including a resonant circuit composed of a transformer.

Claims

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

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 is connected to a first terminal of a primary coil of a transformer having primary and secondary coils,

a second terminal of the primary coil of the transformer is connected to a second terminal of the rectification circuit,

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 is connected with a first terminal of a first capacitor,

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

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

7. The soft switching DC-DC converter according to claim 1 using a transformer having primary and secondary coils,

wherein the coefficient of coupling between the primary coil and the secondary coil of the transformer is in the range of 0.2 to 0.9.

8. The soft switching DC-DC converter according to claim 1 provided with a period of time in which both of the first and second switching elements are turned off,

wherein the first switching element is turned on at least after the second switching element has been turned on.

9. The soft switching DC-DC converter according to claim 1 including:

a first drive circuit for driving and controlling the first switching element;

a second drive circuit for driving and controlling the second switching element;

an input voltage detection section for detecting an input voltage;

an input current detection section for detecting an input current;

an output voltage detection section for detecting an output voltage;

an output voltage setting section for setting an output voltage; and

a control circuit for controlling these components,

wherein the control circuit controls the first and second drive circuits so as to match the shapes of the voltage waveform of the input voltage detection section and the current waveform of the input current detection section, as well as to match the voltage values of the output voltage detection section and the output voltage setting section.

10. The soft switching DC-DC converter according to claim 8, wherein the first switching element is turned on when the second switching element has been turned on and when the potential difference between one terminal of the first switching element and the other terminal of the first switching element is 0 V.

11. The soft switching DC-DC converter according to claim 8, wherein the first switching element is turned on when the second switching element has been turned on and is distributing power to the second diode.

12. The soft switching DC-DC converter according to claim 7, wherein the transformer having the primary and secondary coils is molded by high thermal conductive resin with a metal or inorganic ceramic filler mixed into a high-thermal conductive resin in which an anisotropic structure exists within the resin component.

13. The soft switching DC-DC converter according to claim 7 using the transformer having the primary and secondary coils, wherein the secondary coil is divided into two or more.

14. The soft switching DC-DC converter according to claim 1, wherein the second switching element uses a switching element with a reverse voltage.

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

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 having primary and secondary coils 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 secondary coil of the transformer are connected together, and

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

4. A soft switching DC-DC converter for converting an input voltage into another voltage, the converter having a capacitor of the boost converter according to claim 3 as a power source, and being connected with the buck converter according to claim 2, wherein the boost converter is connected with the resonant circuit according to claim 3, and the buck converter is connected with the resonant circuit according to claim 2.

5. A soft switching DC-DC converter for converting an input voltage into another voltage, the converter having a capacitor of the buck converter according to claim 2 as a power source, and being connected with the boost converter according to claim 3, wherein the buck converter is connected with the resonant circuit according to claim 2, the boost converter is connected with the resonant circuit according to claim 3, and the primary coil of the transformer of the resonant circuit of the buck converter is commonly used as a choke coil of boost converter and the buck converter.

6. A soft switching DC-DC converter for converting an input voltage into another voltage,

wherein a first terminal of a rectification circuit of a power source and a first terminal of a first inductor are connected together;

a second terminal of the first inductor and a first terminal of a first switching element having a control terminal for controlling a main electric current are connected together;

a second terminal of the first switching element and a second terminal of the rectification circuit are connected together;

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

the buck converter according to claim 2 is connected between a second terminal of the first diode and the second terminal of the rectification circuit,

wherein the buck converter is connected with the auxiliary circuit according to claim 2, and is mounted with a control circuit in which the first switching element is turned on when the input voltage is equal to or less than a desired value, and the first switching element is turned off when the input voltage exceeds the desired value.

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

wherein a first terminal of a rectification circuit of a power source is connected with a first terminal of a primary coil of a transformer having primary and secondary coils,

a second terminal of the primary coil of the transformer 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 second terminal of the rectification circuit are connected together,

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

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

a second terminal of the secondary coil of the transformer 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, and

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

15. A soft switching DC-DC converter for converting an input voltage into another voltage, the converter including:

a first switching element having a first terminal connected to an input side and having a control terminal for controlling a main electric current of the soft switching DC-DC converter;

a primary coil of a transformer having primary and secondary coils, connected to a second terminal of the first switching element;

a diode having a first terminal connected to the first terminal of the first switching element.;

a second switching element having a first terminal connected to a second terminal of the diode; and

the secondary coil of the transformer, having a first terminal connected to a second terminal of the second switching element, and having a second terminal connected to the second terminal of the first switching element.

18. The soft switching DC-DC converter according to claim 15 provided with a period of time in which both of the first and second switching elements are turned off,

wherein the first switching element is turned on at least when the second switching element has been turned on.

19. The soft switching DC-DC converter according to claim 18, wherein the first switching element is turned on when the second switching element has been turned on and when the potential difference between one terminal of the first switching element and the other terminal of the first switching element is 0 V.

20. The soft switching DC-DC converter according to claim 18, wherein the first switching element is turned on when the second switching element has been turned on and is distributing power to the second diode.

16. A soft switching DC-DC converter for converting an input voltage into another voltage, the converter including:

a first switching element having a first terminal connected to an input side, and having a control terminal for controlling a main electric current of the soft switching DC-DC converter;

a first diode having a first terminal connected to a second terminal of the first switching element;

a primary coil of a transformer having primary and secondary coils, connected to a second terminal of the first switching element;

a second diode having a first terminal connected to the first terminal of the first switching element;

a second switching element having a first terminal connected to a second terminal of the second diode; and

the secondary coil of the transformer, having a first terminal connected to a second terminal of the second switching element, and having a second terminal connected to the second terminal of the first switching element.

17. A soft switching DC-DC converter for converting an input voltage into another voltage, the converter including:

a first switching element having a control terminal for controlling a main electric current of the soft switching DC-DC converter;

a primary coil of a transformer having primary and secondary coils, connected to a first terminal of the first switching element;

the secondary coil of the transformer, connected to the first terminal of the first switching element;

a diode having a first terminal connected to the other terminal of the secondary coil of the transformer; and

a second switching element having a first terminal connected to a second terminal of the diode,

wherein a second terminal of the second switching element is connected to a second terminal of the first switching element.