Title:
SWITCHING POWER SUPPLY DEVICE
Document Type and Number:
Japanese Patent JP3042171
Kind Code:
B2
Abstract:
PURPOSE: To improve reliability and reduce cost by performing constant voltage control of the output voltage at the secondary side only by the primary side of a transformer without using a photocoupler.
CONSTITUTION: As an output voltage V2 at the secondary side increases, a voltage V3 which is generated at a bias coil winding 2c of a transformer 2 also increases and then a negative voltage V4 at the cathode side of a rectification diode 28 increases toward minus side. When the negative voltage V4 becomes larger than a specified value, a current I1 which is lead into a shunt regulator 32 increases. Then, the current I1 is amplified by a transistor 42 for amplification, is fed to a base circuit of a transistor 12 for bypassing, and passes through the transistor 12 for bypassing. Then, current flowing to the base of a switching transistor 4 is bypassed to the ground line and then ON period of the switching transistor 4 is reduced, thus reducing the output voltage V2 at the secondary side and hence performing constant voltage control of the output voltage V2 at the secondary side only at the primary side of the transformer 2.
Inventors:
Atsushi Hirono
Koji Nakahira
Koji Nakahira
Application Number:
JP13588392A
Publication Date:
May 15, 2000
Filing Date:
April 27, 1992
Export Citation:
Assignee:
MURATA MANUFACTURING CO.,LTD.
International Classes:
H02M3/28; H02M3/338; (IPC1-7): H02M3/338; H02M3/28
Domestic Patent References:
| JP382368A | ||||
| JP63179783U | ||||
| JP480285U |
Attorney, Agent or Firm:
Keiji Yamamoto