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Registered Member #3859
Joined: Sun May 01 2011, 03:47PM
Location:
Posts: 179
I built this circuit:
I didn't have all the parts so I built only the part with TL494 and after, without the feedback and the amplifier part. So I had the variable resistor, the TL494 , and all the resistors and a capacitor that surround it. I checked the circuit 5 times after soldering it together.
I wired a 12 volt halogen light bulb to test the circuit's ability to PWM drive loads. I use IRF540 instead of BUZ31L but I have done it before.
So I try to make my circuit work by connecting pin 1 to a variable +12 to -12 power supply. The halogen lightbulb was not lit, than it lit up, but then the TL494 burned.
Why didn't my circuit work like an improvised dimmer switch for the lamp? As I understand this is how it is supposed to interpret the 0 to 12 volt input from the amplifiers. I probably went below 0 volts when I tried to influence pin 1 with a variable voltage input but why didn't it work when there was 0 volts?
Registered Member #3943
Joined: Sun Jun 12 2011, 05:24PM
Location: The Shire, UK
Posts: 552
Does your MOSFET still test good? As halogen light bulbs can briefly draw several times their normal running current when first energised (cold filament resistance is very low).
If the MOSFET has been damaged then a low resistance from gate to source could have caused a high continuous current to have been sunk through the TL494's internal driver transistors making it heat rapidly.
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TL494 didn't respond, then burned
