Circuit of a power supply unit having a switching device

1. A circuit of a power supply unit, comprising:

a first rectifying device having an anode which is to be connected to a negative terminal of a direct current power source,

a second rectifying device having an anode which is connected to a cathode of the first rectifying device,

a first condenser having one end which is connected to the anode of the second rectifying device,

a second condenser connected to a cathode of the second rectifying device and connected to a positive terminal of the direct current power source,

a third rectifying device having an anode which is connected to the cathode of the second rectifying device,

a resonance reactor connected to a cathode of the third rectifying device and connected to an other end of the first condenser,

a switching device having a first main terminal which is to be connected to the positive terminal of the direct current power source, having a second main terminal which is connected to the cathode of the third rectifying device,

an output reactor having one end which is connected to the cathode of the third rectifying device,

an output condenser including one end and an other end, the one end to be connected to the negative terminal of the direct current power source and the other end connected to the other end of the output reactor,

an output rectifying device having a cathode which is connected to the other end of the first condenser and having an anode which is to be connected to the negative terminal of the direct current power source,

a control circuit, executing sensing of at least one of a voltage of the direct current power source, a voltage of a load, and a current of the output reactor, carrying out calculations based on the sensed input(s), and sending a gate signal to a control terminal of the switching device at a selected on duty, and

a fourth rectifying device having an anode which is to be connected to the negative terminal of the direct current power source and having a cathode which is connected to the cathode of the third rectifying device and the output reactor, the fourth rectifying device connected in parallel with a series of the output rectifying device and the resonance reactor.

2. The circuit of a power supply unit as set forth in claim 1 , wherein

the resonance reactor is made of a wiring with a parasitic inductance.

3. A circuit of a power supply unit, comprising:

a first rectifying device having an anode which is to be connected to a negative terminal of a direct current power source,

a second rectifying device having an anode which is connected to a cathode of the first rectifying device,

a first condenser having one end which is connected to the anode of the second rectifying device,

a second condenser connected to a cathode of the second rectifying device and to be connected to a positive terminal of the direct current power source,

a third rectifying device having an anode which is connected to the cathode of the second rectifying device,

a resonance reactor connected to a cathode of the third rectifying device and connected to an other end of the first condenser,

a first switching device having a first main terminal which is to be connected to the positive terminal of the direct current power source, having a second main terminal which is connected to a cathode of the third rectifying device, and having a control terminal connected to a control circuit,

an output reactor having one end which is connected to the cathode of the third rectifying device,

an output condenser including one end and an other end, the one end to be connected to the negative terminal of the direct current power source and the other end connected to the other end of the output reactor,

a second switching device having a first main terminal which is connected to the other end of the first condenser, and having a second main terminal which is to be connected to the negative terminal of the direct current power source, and

a control circuit, executing sensing of at least one of a voltage of the direct current power source, a voltage of a load, and a current of the output reactor, carrying out calculations based on the sensed input(s), and sending a first gate signal to a control terminal of the first switching device and sending a second gate signal to a control terminal of the second switching device, the second gate signal being in an opposite phase to a phase of the first gate signal at a selected on duty, wherein

a first dead time is set between a decay time of the first gate signal and a rise time of the second gate signal, and a second dead time is set between a decay time of the second gate signal and the rise time of the first gate signal,

the length of the first dead time and the length of the second dead time become shorter as the current which flows through the output reactor becomes larger, the voltage at both ends of the output condenser becomes smaller and the voltage of the direct current power source becomes smaller, and

the first dead time is set to satisfy the conditions that the second resonance condenser is charged to have the voltage of the direct current power source, the first resonance condenser is discharged to have a 0V and, furthermore, switching devices are turned on at the timing in which electric current starts to flow into the switching devices.

4. The circuit of a power supply unit as set forth in claim 3 , wherein

the second gate signal is turned on at the timing when the detected voltage of the first condenser is decayed.

5. The circuit of a power supply unit as set forth in claim 3 , wherein

the resonance reactor is made of a wiring with a parasitic inductance.

6. A circuit of a power supply unit, comprising:

a first rectifying device having an anode which is to be connected to a negative terminal of a direct current power source,

a second rectifying device having an anode which is connected to a cathode of the first rectifying device,

a first condenser having one end which is connected to the anode of the second rectifying device,

a second condenser connected to a cathode of the second rectifying device and to be connected to a positive terminal of the direct current power source,

a third rectifying device having an anode which is connected to the cathode of the second rectifying device,

a resonance reactor connected to a cathode of the third rectifying device and connected to an other end of the first condenser,

a first switching device having a first main terminal which is to be connected to the positive terminal of the direct current power source, and having a second main terminal which is connected to a cathode of the third rectifying device,

an output reactor having one end which is connected to the cathode of the third rectifying device,

an output condenser including one end and an other end, the one end to be connected to the negative terminal of the direct current power source and the other end connected to the other end of the output reactor,

a second switching device having a first main terminal which is connected to the other end of the first condenser, and having a second main terminal which is to be connected to the negative terminal of the direct current power source,

a control circuit, executing sensing of at least one of a voltage of the direct current power source, a voltage of a load, and a current of the output reactor, carrying out calculations based on the sensed input(s), and sending a first gate signal to a control terminal of the first switching device and sending a second gate signal to a control terminal of the second switching device, the second gate signal being in an opposite phase to a phase of the first gate signal at a selected on duty, and

a fourth rectifying device having an anode which is to be connected to the negative terminal of the direct current power source and having a cathode which is connected to the cathode of the third rectifying device and the output reactor, the fourth rectifying device connected in parallel with a series of the output rectifying device and the resonance reactor.

7. The circuit of a power supply unit as set forth in claim 6 , wherein

a first dead time is set between a decay time of the first gate signal and a rise time of the second gate signal, and

a second dead time is set between a decay time of the second gate signal and the rise time of the first gate signal.

8. The circuit of a power supply unit as set forth in claim 7 , wherein

the length of the first dead time and the length of the second dead time become shorter as the current which flows through the output reactor becomes larger, the voltage at both ends of the output condenser becomes smaller and the voltage of the direct current power source becomes smaller, and

the first dead time is set to satisfy the conditions that the second resonance condenser is charged to have the voltage of the direct current power source, the first resonance condenser is discharged to have a 0V and, furthermore, switching devices are turned on at the timing in which electric current starts to flow into the switching devices.

9. The circuit of a power supply unit as set forth in claim 6 , wherein

the second gate signal is turned on at the timing when the detected voltage of the first condenser is decayed.

10. A circuit of a power supply unit, comprising:

a first rectifying device having an anode which is to be connected to a negative terminal of a direct current power source,

a second rectifying device having an anode which is connected to a cathode of the first rectifying device,

a first condenser having one end which is connected to the anode of the second rectifying device,

a second condenser connected to a cathode of the second rectifying device and to be connected to a positive terminal of the direct current power source,

a third rectifying device having an anode which is connected to the cathode of the second rectifying device,

a resonance reactor having one end connected to an other end of the first condenser,

a first switching device having a first main terminal which is to be connected to the positive terminal of the direct current power source, and having a second main terminal which is connected to an other end of the resonance reactor,

a second switching device having a first main terminal which is connected to a cathode of the third rectifying device, and having a second main terminal which is directly connected to a second main terminal of the first switching device, and the other end of the resonance reactor,

an output rectifying device having a cathode which is connected to an other end of the first condenser and having an anode which is to be connected to the negative terminal of the direct current power source,

an output reactor having one end which is directly connected to the second main terminal of the second switching device,

an output condenser including one end and an other end, the one end to be connected to the negative terminal of the direct current power source and the other end connected to an other end of the output reactor, and

a control circuit sending a first gate signal to a control terminal of the first switching device and sending a second gate signal to a control terminal of the second switching device, the second gate signal being in an opposite phase to a phase of the first gate signal.

11. The circuit of a power supply unit as set forth in claim 10 , wherein

the resonance reactor is made of a wiring with a parasitic inductance.