Pwm switching regulator control circuit

A switching voltage regulator and control circuit technology, applied in circuit devices, control/regulation systems, emergency protection circuit devices, etc., can solve the problems of increasing ripple voltage and reducing output voltage, so as to prevent output voltage drop, ripple The effect of small wave voltage

Inactive Publication Date: 2005-02-09
SEIKO INSTR INC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The voltage is not boosted during this off time and the output voltage is lowered by the load, the ripple voltage becomes larger

Method used

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  • Pwm switching regulator control circuit
  • Pwm switching regulator control circuit
  • Pwm switching regulator control circuit

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Embodiment Construction

[0019] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0020] figure 1 is a schematic diagram showing a PWM switching regulator control circuit according to the present invention.

[0021] Basic operation is the same as conventional circuit except soft start. The error amplifier 108 outputs the difference between the feedback voltage Va obtained by dividing the output voltage VOUT by the voltage dividing resistors 101 and 102 and the voltage VREF output from the reference voltage circuit 104 as an output VERR. Then, the PWM comparator 110 outputs a comparison result between the output VERR of the error amplifier 108 and the output VOUT of the chopper oscillation circuit 109 .

[0022] The switch circuit 112 outputs a pulse signal to start the oscillation circuit 111 to the EXT terminal until the output voltage VOSC becomes a stable voltage. The pulse signal causes the external switch to ...

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PUM

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Abstract

Provided is a PWM switching regulator control circuit, which is small in the ripple voltage without a drop of the output voltage which, is attributable to a load at the time of a soft start. A PWM switching regulator control circuit is provided, in which an offset voltage that is lower than a reference voltage is inputted to an error amplifier at the time of a soft start, to thereby prevent an off-time from occurring in the PWM comparator output, prevent the output voltage that is attributable to the load from dropping, and make the ripple voltage small.

Description

technical field [0001] The invention relates to a PWM switching regulator control circuit with soft start function. Background technique [0002] In order to suppress the inrush current or the overshoot of the output voltage when the power is turned on, some PWM switching regulator control circuits provide a soft-start function. Refer to Figure 2 and image 3 , the operation of the conventional soft-start function will be described sequentially from when no supply voltage is present at all. [0003] First, when the power supply is connected to the PWM switching regulator control circuit, the output voltage VOUT rises from 0V, the current flows from the constant current source 206 into the capacitor 207, and the gate voltage of the n-channel MOS transistor 204 gradually rises. As a result, since the voltage VREF of the reference voltage 203 slowly rises the voltage at the non-inverting input terminal of the error amplifier 208, the rush current and the overshoot of the outpu...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H02M3/00H02H9/00H02M3/155H03K7/08
CPCH02M1/36H03K7/08H02H9/001H02M3/155
Inventor 田家良久
Owner SEIKO INSTR INC
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