Discharging circuit for power source device with rectifier circu

Details Discharging circuit for power source device with rectifier circu Discharging circuit for power source device with rectifier circu

1982-02-22

1984-05-15

Wong, Peter S.

Electric power conversion systems

Current conversion

Using semiconductor-type converter

363 46, H02M 706

Patent

active

044491778

DESCRIPTION:

BRIEF SUMMARY
DESCRIPTION

1. Technical Field
The present invention relates to a discharging circuit for a power source device with a rectifier circuit.
2. Background of the Invention
The circuit shown in FIG. 1 has been used as a conventional high power rectified direct-current power source device, for example a direct-current power supply used to drive electric motors. Namely, an output of a rectifier circuit 11 is connected to the load through terminals 14 and 15, and the circuit 11 is connected in parallel to the load with a smoothing capacitor 12 for decreasing the ripple, and a dummy resistor 13. This circuit, however, suffers from the problem that the dummy resistor 13 is continually heated when the power source voltage is applied and the problem that a large capacitor value would result in a longer time constant of the circuit because of the high resistance value of the dummy resistor 13 and, thereby, causes concern over unsafe conditions due to delayed decrease of the voltage across the capacitor due to slow discharging.
The present invenion is proposed in order to solve the above-mentioned problems in the conventional circuit.


SUMMARY OF THE INVENTION

In consideration of the above-mentioned problems in conventional discharging circuits for power source devices with rectifier circuits, an object of the present invention is to decrease the generation of the heat at the resistor and eliminate the concern over safety due to delayed discharge of the capacitor, based on the idea of activating a switching circuit to connect the capacitor circuit with the resistor having low resistance value when the output voltage of the rectifier circuit falls below a predetermined value lower than the charged voltage of the smoothing capacitor.
According to the present invention, there is provided a discharging circuit for a power source device with a rectifier circuit, in which one terminal of said rectifier circuit is connected to one terminal of a smoothing capacitor and the other terminal of said rectifier circuit is connected to the other terminal of said smoothing capacitor through a diode, said smoothing capacitor being connected in parallel to a circuit consisting of a resistor and a circuit conducting transistor connected in series, said rectifier circuit having connected across its terminals a time constant selection circuit consisting of a resistor and a capacitor connected in parallel, the connecting point of said diode and said rectifier circuit and the base of said transistor having connected between them a Schmitt circuit, said time constant selection circuit and said Schmitt circuit being activated when said power source is turned off, whereby said circuit conducting transistor is made conductive, whereby, said smoothing capacitor is discharged.


BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a circuit diagram of a conventional discharging circuit for a power source device with a rectifier circuit,
FIG. 2 is a circuit diagram of a discharging circuit for a power source device with a rectifier circuit according to an embodiment of the present invention,
FIG. 3 is a circuit diagram of a Schmitt circuit used for the circuit in FIG. 2.


BEST MODE FOR CARRYING OUT THE INVENTION

Below, a discharging circuit for a power source device with a rectifier circuit according to an embodiment of the present invention is explained in reference to FIG. 2. A rectifier circuit 21 is supplied with alternating current voltage and outputs rectified voltage. One output line is connected to a terminal 31, the other output line is connected to the cathode of a diode 25, and the anode of the diode 25 is connected to a terminal 32. A load (not shown) is connected between the terminals 31 and 32. The cathode of the diode 25 is also connected with one of the terminals of a resistor 22, one of the terminals of a capacitor 23, and the input terminal of a Schmitt circuit 24. The output of the Schmitt circuit 24 is connected to the base of a circuit conducting transistor 27, the emitter of the transistor 27 is connected to the anode of the diode 25

REFERENCES:
patent: 3246229 (1966-04-01), Lloyd
patent: 3670230 (1972-06-01), Rooney et al.
patent: 4275436 (1981-06-01), Peterson

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