Vermes
Advanced Member level 4
This device uses a mains power of a typical construction – in the 'flyback' system with UC3842 controller, with main output counted for 23V/12A. In addition, a voltage of +8V, -8V is produced to power the driver, ventilator and measurement amplifier and +38V to power TL494 in the regulator. The regulator system is a step-down converter with the TL494 and n-MOSFET transistor. The value of voltage and current limit is set by an analogue signal (range from 0V to about 4,5V), the same signal is taken from the module in order to measure.
Scheme of the regulator:
The module of the driver uses Atmega8 microcontroller (because of the number of its legs and the flash memory), with connected display such as in Nokia 3310 and the capacitance keypad (it is not a simple touch keypad – copper is lacquered). Instead of a special C/A converter, PWM modulator was used with RC filter with a big time constant. There are two functions available: function of basic power supply of 0-20V, 0-10A and Li-ion and acid accumulators charger. Function of calibration allows to calibrate the A/C and C/A converters, using additional voltmeter and ammeter, it can be useful because of using resistors 5% and not very accurate source of reference (78L05).
Link to original thread – Zasilacz regulowany II (0..10A, 0..20V), funkcja ładowarki