ClariTy 2x300W Class-T Amplifier Part 3: power supply assembly and alignment （1）

Published:2011/8/3 22:20:00 Author:Amy From:SeekIC

Ton Giesberts

As already mentioned in the previous parts of this article, this final amp needs more than just a heavy-duty symmetrical power supply. In this final part, we examine the main power supply, the other power supplies, final assembly and alignment.

The analogue input portion of the TA3020 operates from a stabilised 5-V supply voltage. A stabilised 10-V auxil-iary voltage is also needed for driving also has a switch-on delay for the mains voltage (current limiting). An additional feature is a buffer circuit with a phase inverter, which allows in a bridge configuration without requiring any modifications to the amplifier board. Naturally, the required mains power indicator and mute signal the MOSFETs. The power supply board the two channels to be easily operated are also present.

Analogue power sup­ply and mute circuit

The analogue 5-V power supply has its own transformer (TR1,2 x 9 V). A small, discrete-component circuit for generat­ing a well-defined mute signal is added here (see Figure 1). The supply voltage for this circuit is taken directly from the output of the bridge rectifier (Bl), fil­tered by a small capacitor (C14), so the amplifier can be switched to mute mode as quickly as possible when the mains voltage drops out.



The mute circuit is the height of sim­plicity: after C13 has been charged, T2 has enough voltage to fully drive the optocoupler on the amplifier board. C13 is slowly charged via Rll until it reaches the level defined by voltage divider R9/R10. D2 limits the voltage at the mute output, but the ultimate value is not especially critical. When the mains voltage drops out, C13 is quickly discharged by D3. The mute signal can be connected to the ampli­fier board via pin header K2.

The negative supply voltage is only needed for powering the phase inverter. Standard positive and negative voltage regulators are used for the +/- 5-V sup­plies. The -i-5-V supply can be con­nected to the amplifier board via Kl. The negative voltage is also available on a solder pin, so it is also available for user-defined applications.

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