Title:
SWITCHING TYPE DC POWER SUPPLY
Document Type and Number:
Japanese Patent JP3145442
Kind Code:
B2
Abstract:
PURPOSE: To provide a switching type DC power supply, which can prevent the abnormal heat generation and fuming of components and the like, by limiting a total power to a pedetermined value and below and by limiting the total power more than the predetermined value when a load is partially excessive.
CONSTITUTION: When overcurrent flows to any of loads (not shown in the figure) connected with output terminals 4, 5, 6 and 7, an overload detection circuit 9 outputs a signal. A voltage proportional to the current of a switching transistor Q1 detected by a resistance R1 is offset by the output signal of the overload detection circuit 9 at an offset circuit 10, and when the voltage exceeds the threshold value, the pulse width of a switching transistor Q1 is limited by a PWM circuit 3 so that the overcurrent can be limited and the abnormal heat generation and fuming of components, etc., related to the loads can be prevented.
Inventors:
Masayoshi Saito
Application Number:
JP27959291A
Publication Date:
March 12, 2001
Filing Date:
October 25, 1991
Export Citation:
Assignee:
Canon Inc
International Classes:
H02M3/28; H02M7/12; (IPC1-7): H02M3/28; H02M7/12
Domestic Patent References:
| JP5835615A | ||||
| JP1160361A | ||||
| JP63310370A |
Attorney, Agent or Firm:
Hiroyuki Niwa (1 outside)