30W 220V Inverter Module, the reality about it! Schematic, Details, Infos 

Keep up with the informative videos. Cheers Dave.

You made a 30 minute video on a cheap Chinese inverter?? That's exactly the kind of content i'm here for! Thank you so much!

cool video! 1. Careful about touching the transformer as the output windings possibly not safety insulated (I could see copper between the tape). I suppose if all supplies, loads, and measuring devices are fully isolated, you may be single fault tolerant for a single finger... two fingers not so much. I thought it odd that the transformer seemed to have a lot of empty volume. Perhaps they reduced the wire gauge from the original design to save money? 2. Because a tungsten filament impedance changes with temperature, the relation of true power (watts) is not as linear as you indicated for both the 1-bulb and 2-bulb tests when the voltage is not at rated levels... however, it works fine for a first order approximation. It would be cool if you had a current probe for the 2nd channel of the oscilloscope! 3. The bridge rectifier presents as a non-linear load on the source drawing most of the current at the voltage peaks (resulting in very poor crest factor as you showed on the scope). The peak currents in the windings could I guess with 20-30kHz you had chose appropriate diodes and bulk capacitance b/c standard 50/60Hz parts would not work well?

Hi Konstantin, nice testing of this cheap inverter, but i think that you have at 11:35 made a calculation error. With 230V and 213 Ohm of current limiting, the maximum current is 0,2A and not 1A. With 230V and 0,2A of current, it becomes 46Watt. Way above the advertised 30Watt limit. Also, if you use a 10 times higher C2 capacitor like 220nF, the current limit drops to 21,3 Ohm with 34Khz. With a capacitor as resistor, the higher the capacitor value, the higher AC current that can flow. But it all depends on the frequency. With 230V mains voltage at 50Hz, and 213 Ohm of current limiting value, you need arround 15uF capacitance. I can be wrong, but i think these cheap mini inverters are old stock and that they where used to drive Fluorescent lamps in emergency exit lamps powered from a 12V AGM battery in case of mains faillure. Grtz

What's the cheap Chinese module on the left of the last circuit? I couldn't hear what you said.

I can't believe that schematics is right - the PNP transistors are closed from the beginning by R1/R2. Chematics should work if swap Collectors with Emitters and swap power polarity or transistors PNP to NPN. Are you sure?