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Title:
SHORT-CIRCUITING PROTECTIVE CIRCUIT
Document Type and Number:
Japanese Patent JPH07227083
Kind Code:
A
Abstract:

PURPOSE: To prevent fuming and burning of parts by stopping oscillation of a power conversion switch when an output voltage decreases below a certain level due to the short-circuiting of output or parts or that of the secondary coil winding of a transformer.

CONSTITUTION: When a secondary coil winding 5 of a transformer 6 is short- circuited during operation, a light emitting element 33 of a photocoupler stops emitting light and transfers a failure output voltage detection to an oscillation circuit 38 of a power conversion switch. In an oscillation stop circuit 38, a phototransistor 19 which is the light receiving element of the photocoupler stops conducting current due to the emission stop of the light emitting element 33. Therefore, the terminal voltage of a resistor 24 obtained from the division ratio of resistors 18 and 24 of the voltage at both terminals of a zener diode 23 serially connected to a resistor 22 connected to a DC input power supply 1 increases, thus enabling a transistor 14 to conduct. Then, the drive terminal of the power conversion switch is short-circuited via a diode 15, thus stopping oscillation and hence cutting off the power supply to a secondary side for protection.


Inventors:
KISHI KOJI
Application Number:
JP1994000014221
Publication Date:
August 22, 1995
Filing Date:
February 08, 1994
Export Citation:
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Assignee:
HITACHI LTD
HITACHI COMPUTER ELECTRONIC
International Classes:
H02H3/24; H02M3/28; (IPC1-7): H02M3/28; H02H3/24
Attorney, Agent or Firm:
小川 勝男