Self oscillating power supply

Details Self oscillating power supply Self oscillating power supply

1998-01-26

1999-06-29

Riley, Shawn

Electric power conversion systems

Current conversion

Including d.c.-a.c.-d.c. converter

363 56, H02M 3335

Patent

active

059177128

DESCRIPTION:

BRIEF SUMMARY
This Application is a U.S. National Phase Application of PCT International Application PCT/JP96/01233.


TECHNICAL FIELD

The present invention relates to a power supply device used in various electronic appliances, and more particularly to a power supply device useful as a non-contact power supply device used in small portable appliances, for example, cordless telephone, cellular telephone, PHS, video with camera, and personal computer.


BACKGROUND ART

In a power supply device generally known, an output is obtained at a secondary side by resonating the voltage of a primary side coil of a switching transformer and a capacitor connected at its both ends.
As means for obtaining a stabilized output at the secondary side, a circuit composition for controlling the primary side, or a circuit composition for controlling the secondary side are used, among others.
First, as the means for controlling the primary side, FIG. 15 shows a circuit diagram of a conventional power supply device for controlling and stabilizing the on/off period of switching by installing a control circuit at the primary side, and feeding back the gate signal of the switching element as means for stabilizing and oscillating, to the output of the switching element by an impedance circuit composed of a series circuit of resistance and diode. According to the diagram, an input power source 1 is a DC voltage rectified and smoothed from a commercial power source, and a series circuit of starting circuit composed of a resistance 2 and a capacitor 3 is connected to both ends of the input power source 1, and a series circuit of a primary side coil 4 of switching transformer and switching element 5 is connected, and a capacitor 6 is connected to both ends of the primary side coil 4 of the switching transformer.
Moreover, the junction of the resistance 2 and capacitor 3 is connected to the drain of the switching element 5 through a series circuit of a resistance 7 and diode 8, and is further connected to the gate of the switching element 5 through a control winding 9 of the switching transformer. A capacitor 11 is connected to both ends of a secondary side coil 10 of the switching transformer, and a capacitor 13 is connected through a diode 12, thereby obtaining an output at both ends of the capacitor 13. Incidentally, the load side after the secondary side coil 10 of the switching transformer is separable, and an output can be obtained as required.
The operation of the conventional power supply device is described below. First, when the input power source 1 is applied, a voltage starts to be charged into the capacitor 3 through the resistance 2. The voltage of the capacitor 3 is fed into the gate of the switching element 5 through the control winding 9 of the switching transformer, and when reaching the threshold voltage of the gate, the switching element 5 begins to conduct. As a result, a voltage is induced in the control winding 9 of the switching transformer and the secondary side coil 10 of the switching transformer, and the voltage of the control winding 9 of the switching transformer elevates, and the gate voltage of the switching element 5 is further increased, so that the switching element 5 is completely turned on instantly by the positive feedback action.
Therefore, the current of the primary side coil 4 of the switching transformer, that is, the drain current of the switching element 5 increases linearly, and the energy is accumulated in the primary side coil 4 of the switching transformer. As the switching element 5 is completely turned on, an impedance circuit 14 of resistance 7 and diode 8 (or, an impedance circuit 15 shown in FIG. 15, instead of this impedance circuit 14) begins to discharge the voltage of the capacitor 3, that is, the gate voltage of the switching element 5. By such feedback action, when the gate voltage of the switching element 5 becomes lower than the threshold voltage, the switching element 5 is suddenly turned off.
As the switching element 5 is turned off, the voltage induced in the primary side coil 4 of the sw

REFERENCES:
patent: 4652984 (1987-03-01), Van Der Akker et al.
patent: 4937727 (1990-06-01), Leonardi

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