Switching power supply device

• US 5,644,479 A
• Filed: 10/18/1994
• Issued: 07/01/1997
• Est. Priority Date: 10/27/1993
• Status: Expired due to Term

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Ishii, Takuya, Yoshida, Koji
• Primary Examiner(s): Wong, Peter S.
• Assistant Examiner(s): Riley, Shawn
• Application Number:
  US08/325,928
• Time in Patent Office: 987 Days
• Field of Search: 363/15, 363/16, 363/40, 363/97, 363/131
• 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

Abstract

A switching power supply device which includes a series circuit constituted by a first switching element which is connected to an input voltage and which is at least repeatedly turned on and off and a second switching element which is repeatedly turned on and off alternating with the first switching element. A first capacitor is connected to one end of the second switching element. A transformer having a primary winding is connected to the second switching element and the first capacitor. A series circuit constituted by a second capacitor and a rectifier diode is connected across the secondary winding of the transformer, and a series circuit constituted by an inductance element and a smoothing capacitor is connected across the rectifier diode. A control circuit controls the turning on and off of the first and second switching elements based on the voltage across the smoothing capacitor. The voltage across the smoothing capacitor is supplied as the output.

Claims

1. A switching power supply device comprising:

a series circuit constituted by a first switch means which is connected to an input voltage and which is repeatedly turned on and off, and a second switch means which is repeatedly turned on and off to alternate with said first switch means;

a first capacitor connected to one end of said second switch means;

a transformer having a primary winding connected to said second switch means and said first capacitor and having at least one secondary winding;

a series circuit constituted by a second capacitor, and a rectifier diode connected across said at least one secondary winding of said transformer;

a series circuit constituted by an inductance element and a smoothing capacitor connected across said rectifier diode; and

a control circuit for controlling turning on and turning off of said first and second switch means in order to control an output voltage, said output voltage being a voltage across said smoothing capacitor.

2. The switching power supply device according to claim 1, further comprising a capacitor connected across at least one of said first switch means and said second switch means, said control circuit controlling said turning on and off of said first and second switch means so that there is a period during which both of said switch means are off.

3. The switching power supply device according to claim 1, wherein each of said first and second switch means is constituted by a switching element and a diode which are connected in parallel.

4. The switching power supply device according to claim 1, wherein said first and second switch means each include a FET.

5. A switching power supply device comprising:

a series circuit constituted by a first switch means which is connected to an input voltage and which is repeatedly turned on and off, and a second switch means which is repeatedly turned on and off to alternate with said first switch means;

a first capacitor connected to one end of said second switch means;

a transformer having a primary winding connected to said second switch means and said first capacitor and having at least one secondary winding;

a series circuit constituted by a second capacitor, and a rectifier diode connected across said at least one secondary winding of said transformer;

a series circuit constituted by an inductance element and a smoothing capacitor connected across said rectifier diode; and

a control circuit for controlling turning on and off of said first and second switch means in order to control an output voltage, and

wherein, in a loop including said first and second capacitors, said rectifier diode, and said second switching means coupled through said primary and secondary windings of said transformer;

at least one of said first capacitor and said second capacitor resonates with a leakage inductance of the said primary and secondary windings of said transformer, and an external inductance;

said secondary winding of said transformer serves as a resonance current; and

said output voltage is a voltage across said smoothing capacitor.

6. The switching power supply device according to claim 5, wherein each of said first and second switch means is constituted by a switching element and a diode which are connected in parallel.

7. The switching power supply device according to claim 5, wherein said first and second switch means each include a FET.

8. A switching power supply device comprising:

a series circuit constituted by a first switch means which is connected to an input voltage and which is repeatedly turned on and off, and a second switch means which is repeatedly turned on and off to alternate with said first switch means;

a third capacitor connected across at least one of said first switch means and said second switch means;

a first capacitor connected to one end of said second switch means;

a transformer having a primary winding connected to said second switch means and said first capacitor and having at least one secondary winding;

a series circuit constituted by a second capacitor, and a rectifier diode connected across said at least one secondary winding of said transformer;

a series circuit constituted by an inductance element and a smoothing capacitor connected across said rectifier diode; and

a control circuit for controlling turning on and off of said first and second switch means so that there is a period during which both of said switch means are off;

wherein, in a loop including said first and second capacitors, said rectifier diode, and said second switching means coupled through said primary and secondary windings of said transformer;

at least one of said first capacitor and second capacitor resonates with a leakage inductance of said primary and secondary windings of said transformer or an external inductance;

said secondary winding of said transformer serves as a resonance current; and

said output voltage is a voltage across said smoothing capacitor.

9. The switching power supply device according to claim 8, wherein each of said first and second switch means is constituted by a switching element and a diode which are connected in parallel.

10. The switching power supply device according to claim 8, wherein said first and second switch means each include a FET.