Soft-start reference ramp and filter circuit

Details Soft-start reference ramp and filter circuit Soft-start reference ramp and filter circuit

2004-06-07

2009-08-11

Ullah, Akm E (Department: 2838)

Electricity: power supply or regulation systems

Self-regulating

Using a three or more terminal semiconductive device as the...

C323S901000, C363S049000

Reexamination Certificate

active

07573252

ABSTRACT:
A method and circuit for providing a controlled ramping and filtering to a reference voltage in a regulator circuit such that an inrush current is limited and noise coupling to an output voltage is reduced. In a typical regulator circuit a soft-start and filter circuit is inserted between a feedback amplifier and a charge transfer circuit. The soft-start and filter circuit comprises a pair of transistors that are arranged to operate as a current mirror, a biasing current source determining the current drawn from the current mirror, and a soft-start capacitor shunted by a third transistor providing a conditioned reference voltage. When reference voltage rises rapidly during power-up, charging of the soft-start capacitor with constant current provides a soft-sloped conditioned reference voltage. In steady state, soft-start capacitor and a resistance of the transistor provide a first order low pass filter reducing noise that couples to the reference voltage.

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