Title:
CONSTANT CURRENT OUTPUT CIRCUIT
Document Type and Number:
Japanese Patent JPH04137115
Kind Code:
A
Abstract:
PURPOSE:To reduce the power consumption by measuring the voltage drop in a current limiting element by a voltage drop detecting part and sending a control signal to a switching power supply part by a switching control part so that this voltage drop is fixed. CONSTITUTION:An output voltage Vs of a switching power supply part 10 satisfies relations Vs=VCE+(R+RL)I=VCE+(1+RL/R)Vc where the second term (1+RL/R)Vc is a fixed value. The first term VCE is controlled to a reference voltage VCEO by the close loop passing a transistor, a differential amplifier A3, an adder 61, an integrator 62, a pulse width control circuit 63, a switching element SW, a rectifying and smoothing circuit (D+CL), and the output voltage Vs. A loss PC of the transistor satisfies relations PC=VCEI=2VX22mA=44mW when VCEO is defined as 2V. That is, the loss is reduced to 1/10 of conventional that. As the result, the heat radiation area is reduced to miniaturize the device.
Inventors:
AKIYAMA CHUJI
OKUZUMI TOSHIKI
OKUZUMI TOSHIKI
Application Number:
JP25960390A
Publication Date:
May 12, 1992
Filing Date:
September 28, 1990
Export Citation:
Assignee:
YOKOGAWA ELECTRIC CORP
International Classes:
G05F1/563; G05F1/56; (IPC1-7): G05F1/56; G05F1/563