This is an amplifier, based on the TDA7293 with a switching power supply to power any feedback I would appreciate it. Power Output: min. 50W into 4 ohms at 0.5% THD at about 10V battery voltage - Input voltage: 9-15V (15A) - Standby current is approximately 200mA - Battery voltage monitoring - clipping LED.
Amplifier section - TDA7293. The amplifier section is classically reference diagram from the datasheet of the TDA7293 and contains no special set up. A clipping LED is available as a small optical gimmick.
The power supply - The power supply is designed as a push-pull converter.
The transformer is a ETD29/10/16 N27 with 2 x 6 primary windings (2 x 1.2mm) and 2 x 21 secondary windings (1 x 0.8mm). As the two switching transistors are used IRFZ44N, fed by a combination of 10uH choke + two 1000uF Low ESR capacitors. The transistors are controlled by a TL494, wherein the gate drive is buffered in a totem pole circuit of BC327/BC337. The switching frequency is 60kHz (120kHz or "internal"). The output voltage is adjustable over a balanced and precision trimmer. The control loop is implemented using the positive component of the output voltage. The output filter consists of one inductor and a 3300uF 35V 100uH ultra low ESR capacitor. Backed by the power supply is a 15A fuse. Currently voltage is set to 2 x 24V.
Battery monitor with the help of a TL071 and the reference voltage of the TL494's when I realized a very simple monitoring of input voltage. The alarm point can be adjusted with the help of a trimmer.