- #1
Guineafowl
- 791
- 382
Hi all,
1500W 12Vdc to 110Vac modified sine inverter.
Two output MOSFETs shorted and took some of the driver components with them. I removed all the MOSFETs, and fed in some power carefully - once the voltage rose to 12V, I could see the large output caps were being charged to over 200V, and the input oscillator circuit was working. I concluded the input side was OK.
However, now I've put in some new MOSFETs, replaced their gate driver transistors and two ICs - TC4093BP. These are quad NANDs with Schmitt triggers, I guess for wave shaping. Sadly, the unit only powers on for a brief time then beeps and lights the "overload" LED. The output caps are charged for the brief time before overload kicks in.
There is no short on the output, so what is happening? I have a blurry schematic, and my plan is to follow the overload sense circuit, but it's hard going as the schematic refers to an older model and not everything is the same.
How would you approach this?
Many thanks
1500W 12Vdc to 110Vac modified sine inverter.
Two output MOSFETs shorted and took some of the driver components with them. I removed all the MOSFETs, and fed in some power carefully - once the voltage rose to 12V, I could see the large output caps were being charged to over 200V, and the input oscillator circuit was working. I concluded the input side was OK.
However, now I've put in some new MOSFETs, replaced their gate driver transistors and two ICs - TC4093BP. These are quad NANDs with Schmitt triggers, I guess for wave shaping. Sadly, the unit only powers on for a brief time then beeps and lights the "overload" LED. The output caps are charged for the brief time before overload kicks in.
There is no short on the output, so what is happening? I have a blurry schematic, and my plan is to follow the overload sense circuit, but it's hard going as the schematic refers to an older model and not everything is the same.
How would you approach this?
Many thanks