AP8012 データシートの表示（PDF） - Unspecified

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AP8012

OFF LINE SMPS PRIMARY SWITCHER GREEN POWER

Unspecified 

AiT Semiconductor Inc.

www.ait‐ic.com

AP8012

OFF LINE SMPS PRIMARY SWITCHER

GREEN POWER

DETAILED INFORMATION

Startup

This device includes a high voltage start up current source connected on the SW of the device. As soon as a

voltage is applied on the input of the converter, this start up current source is activated and to charge the VCC

capacitor as long as VCC is lower than VSTART. When reaching VSTART, the start up current source is cut

off by UVLO&TSD and the device begins to operate by turning on and off its main power MOSFET. As the

COMP pin does not receive any current from the opto-coupler, the device operates at full current capacity and

the output voltage rises until reaching the regulation point where the secondary loop begins to send a current

in the opto-coupler. At this point, the converter enters a regulated operation where the COMP pin receives the

amount of current needed to deliver the right power on secondary side.

Fig 1. Startup circuit

Feedback

A feedback pin controls the operation of the device. Unlike conventional PWM control circuits which use a

voltage input, the COMP pin is sensitive to current. The Fig 2. presents the internal current mode structure.

Fig 2. Feedback Circuit

REV1.0 ‐NOV2008 Released ‐

‐6‐

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