Datasheet

Overall System Description

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4.2 Overcurrent Protection (OCP)

4.2.1 Main DC/DC Converter (OCP)

There are 2 different current protection modes in the main DC/DC converter.

The first mode is primary-side detection and the main purpose of this insures that a fault condition on the

50V rail is not destructive.

The current sensing is done by rectifying and filtering the ac-voltage across the resonant capacitor. The

UCC25600 controller IC has a comparator input that senses this voltage and if the voltage exceeds 1V,

the UCC25600 turns off both MOSFETs, resets the soft-start capacitor and initiates a start sequence. The

converter repeats this step until the fault condition is no longer present.

Since the converter is able to supply peak powers above 1 kW but is not thermally designed for this

function, an average power measurement was implemented. By measuring the average output current on

the secondary side rail, an indication of the power level can be established.

The converter should be allowed to supply an average power of approximately 700W. This should ensure

that the amplifier module can deliver 600W.

4.2.2 Auxiliary Converter (OVP)

The auxiliary converter is controlled by the UCC28600 which uses peak current control. The primary side

current is measured and if this current reaches the OC-level, the supply shuts down and initiates a start-up

sequence. This prevents any faulty conditions on the ±15V rail to be destructive.

4.3 Overtemperature Protection

The system has 1 thermal sensor on the PC board located near the Anode of the diode D8.

The sensor is the TMP300 and the trip-temperature can be adjusted by a resistor (R48). In the described

design this temperature is approximately 90°C. The TMP300 has an open drain output that is pinned out

on the board. The TMP300 also supplies an analog voltage that can be translated into a temperature –

available at J4 pin 2.

For a thermal indication, the user should react – either by lowering the amplifier output power or by

shutting down. It is possible to connect the thermal indicator pin directly to the clip-detect pin. This lowers

the rail voltage to 25V and reduces output power.

The thermal protection should be tested in the final product and the user should consider if a primary side

thermal sensor should be applied to the semiconductors.

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

TAS5630 and TAS5631

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