Datasheet

Clip-Detect

VRail

25V

50V

time

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Overall System Description

4.4 Standby

The UCC28600 supplies the bias power to the PFC and DC/DC converter. When the power consumption

on the ±15V rails falls below approx. 1.5W, the UCC28600 turns off the bias power to the main power

converters and enters low power/standby mode.

During this mode the ±15V is "alive" but the main power rail (50V/25V) is off. When power consumption on

the auxiliary voltages goes up again the main power rail is turned on.

4.5 Switchable Rail Voltage

The power supply rail voltage has 2 different settings which are controlled by the clip-detect pin.

During low power situations where 25V rail voltage is sufficient, the system turns off the PFC converter

and only uses the DC/DC converter.

At high line (230VAC) and in this mode, the main DC/DC converter enters a burst mode operation to be

able to regulate the voltage down to 25V. Depending on power level this burst operation produces some

acoustical noise. At low line (110VAC) the DC/DC does not enter the burst mode, and therefore, no

acoustical noise.

When the clip-detect is pulled high (12V), the PFC converter starts and the rail voltage is regulated up to

50V. If the clip-detect pin goes low again the rail voltage stays at 50V for a few seconds and then slowly

ramps down to 25V.

Figure 2. Correlation Between Rail Voltage and Clip-Detect Signal

SLOU293C–June 2010–Revised September 2012 A 600-W, Isolated PFC Power Supply for AVR Amplifiers Based on the

TAS5630 and TAS5631

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