As a first step to build a Half Bridge , I assembled one with IR2153 and an ATX transformer.
with the frequency set to 40khz (RT - 18k , CT - 1nf) , it was outputting around 26 Volts
2 mosfets - 4n60 (FQPxx... 2.6 amp 600v). initially I had two Bulk caps 100uf/250 volts. I connected the output to load, over 1 amp and all seemed okay. (mosfet , Transformer all very cool). Then I changed the Input capacitor. I made a new input part. connected 1x150uf/450v capacitor followed by two 3.3uf/350v in series. for few days / few testing this was working okay . Then one day during working I heard a sound. No output.
I checked - both mosfets gone. IR2153 gone .. IR2153 VCC- GND is short. so i bought new IR2153 and Two 4n60 . connected a 60w lamp before the bridge . I turned it on and gone again... I checked both Mosfet gone , upper mosfet gate resistance is gone ( resistance value infinity). IR2153 still seemed to work . I connected a 56k (RT) and 4.7uf(CT) and connected two LEDS and they are alternately blinking.
In flybacks when Mosfets die (my cases) , I usually found the Drain-source short (continuity in multi meter). But here The Gate-Drain is found short. So with the 150uf in the input I heard connecting a lamp before it wont save the mosfets.. And today I replaced the burned gate resistor. and mosfets (2X2N60). to the one end of the transformer I have the 1uf/250v capacitor and to the other end I connected a 60w incandescent lamp. Turned it on - again gone... both mosfets... G-D short (no reading for even body diode) What could be the reasons.. so to at least save my mosfets where should i connect the 60w lamp..?
Add 18V zeners to gate-source of fets.
Add approx 6r8 resistor in return path of high side gate drive....
Add diode with cathode to switching node connection of chip and anode to ground.
There are two diodes connected across both mosfets FR107 (not shown in the schematic).
What about the 150uf bulk capacitor ? too much ? chance for any inrush current issue ?
Like we do in flyback. how/where to connect a 60w lamp for mosfet protection.
Both times, my high sides gate resistors died.
I will connect 18v zener to both mosfet (G-S). If somehow one mosfet dies then the other one will also die?
will connect 6.8ohm to mosfet (high) return path (I have 4.7 and 8.2 ohm in stock - will try 8.2 ohm). will connect this resistor to IR2153 pin 6 - after the capacitor and before the mosfets junction
there are so many things that can be the fault:-
1) bad layout causing undershoot on the mosfet midpoint, killing the driver IC
2) leakage causing overvolt spikes on the mosfets
3) insufficient heat-sinking
4) RFI at higher currents getting into the control
5) blocking cap not needed by the way - as you already have a cap divider - but it would serve to limit max current in the fets
6) over current at startup
7) Too many volts on pin 1 - NEEDS A ZENER 15V 3W ...!
8) output diodes could fail dus to over volt spikes due to leakage - they need snubbers for safety - as do the pri side mosfets ...!
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p.s. a 60W bulb looks like a short ckt when cold - it is a bad load to use for test on this ckt.