TL494 didn't respond, then burned
tarakan2, Wed Sept 10 2014, 08:52PMI 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?
I should have grounded pin 4 as well?
Re: TL494 didn't respond, then burned
Alex M, Wed Sept 10 2014, 11:18PM
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.
Alex M, Wed Sept 10 2014, 11:18PM
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.
Re: TL494 didn't respond, then burned
tarakan2, Thu Sept 11 2014, 02:34AM
MOSFET is still good. IRF540 is powerful enough.
tarakan2, Thu Sept 11 2014, 02:34AM
MOSFET is still good. IRF540 is powerful enough.
Re: TL494 didn't respond, then burned
tarakan2, Thu Sept 11 2014, 02:53AM
MOSFET is still good. IRF540 is powerful enough.
Why dead time control is used in this circuit in TL494, not the Error Amplifier 2 ?
Why not connect a thermal and a magnetic (optical) feedback system directly to 1,2 and 16,15 ?
There are amps inside the TL494?
I want to build a circuit that uses an optical feedback for a magnetic levitator.
Do I need a different set of resistors instead of a 56K and a 50K variable resistor that connect to pin1 to balance the amplifier inputs?
What should they be equal to to make things work if I use an optical part off this circuit:
- the optical magnetic levitator without PWM.
tarakan2, Thu Sept 11 2014, 02:53AM
MOSFET is still good. IRF540 is powerful enough.
Why dead time control is used in this circuit in TL494, not the Error Amplifier 2 ?
Why not connect a thermal and a magnetic (optical) feedback system directly to 1,2 and 16,15 ?
There are amps inside the TL494?
I want to build a circuit that uses an optical feedback for a magnetic levitator.
Do I need a different set of resistors instead of a 56K and a 50K variable resistor that connect to pin1 to balance the amplifier inputs?
What should they be equal to to make things work if I use an optical part off this circuit:
- the optical magnetic levitator without PWM.Print this page