SPS for Terris MDVD 214

Switching Power Supply 130 Watts (POW3103A) for Terris MDVD 214. The schematic has been reverse engineered from PCB. The device was distributed in Germany via the ALDI (Hofer in Austria) and Amazon.de - 2011 and 2012. In result of overheating R31 (0.22ohm), R32 (0.22ohm) and U5 (STP4435) can burn. It happen to mine MDVD when I left the iPod on the docking socket for more than 3 months during the extremely hot summer of 2018 in Germany. Therefor I have to reverse the schematics and repair the device. The schema might have some inconstancies and deviations from the original. Values of coils, SMD capacitors and some other elements are not indicated. This is because I drew the schema for the purposes of the repair and I was lazy enough not to remove and measure all the goofy small components. Otherwise all the prefixes and text labels (except those I can’t read) are kept as original PCB to facilitate “search and replace” procedure. The circuit is typical SPS consisted by: • EMI filter – bunch of coils and capacitors to avoid electromagnetic interference with other devices. • Input rectifier – Diode (Graetz) bridge with RL257. Converts mains 220V(AC) to 310V(DC). • Inverter – small oscillator/generator (LD7575PS) drives the main switch (MOSFET transistor) and creates 310V AC pulses with frequency bigger than 50 KHz, which are used to feed the primary winding of the transformer. • Transformer – Based on PQ3225 Ferrite Core. It hat 4 windings: primary (input) winding, first output winding(supply power to inverter’s oscillator), second and third output windings(they supply power to corresponding output rectifier and respective step-down voltage converter) • Two simple rectifiers (single diode based). • Two step-down converters (MC34063A) boosted with MOSFET transistor (STP4435) • Inverter feedback voltage loop implemented with opto-copler(EL817) and Zener shunt regulator(LM431). This way the inverter can use PWM to regulate the output.