Hi, I'm having trouble with a simple half bridge induction heater.
The oscilattor is a TL494, working in a range of(30-280KHZ),the drives are two mosfet drivers:TC4421 and TC4422,inverter and no inverter.
In the half bridge, i use two power mosfets IRFP460.
The oscilattor and drivers are ok,delivering 15V signal to the power mosfets gates through 27ohms resistors.
The power mosfets are for maximum ratings: 500V(VDS) 20A(ID) and is is mounted over a good aluminium dissipators.
The problem is: The IRFP460 mosfets are going to get burst, when the power is turned on.
The low voltage power supply feeds 15Vdc and the high voltage power supply feeds 170Vdc to the D(drain) from mains 120Vac.
The first test was with 170Vdc in the D(drain) .it got burned
Then I did a second test, using a variac, feeding 50Vac to both low and high power supplys, resulting in a 72Vdc in the D(drain).
In this second test, I resolved to measure the drain current(ID) and the Vds(drain to source voltage) in one of the two power mosfets.
Thus, in this time, I got only one of the two power mosfets burned after a few seconds, I believe that the ammeter lead wire connections, did a unbalance on the two parts, resulting in it burns.
I am using a work 1.5uH work coil in parallel with a 376nf capacitor bank(resonance frequency in 212KHZ).
A 470nf DC blocking capacitor in series with a 45uH matching coupling inductor.
All this tests were made in a 30KHZ frequency , I did have no time to reach the resonance because the power mosfets got burned before that.
So, Somebody can give me a hand on it?
Regards
The oscilattor is a TL494, working in a range of(30-280KHZ),the drives are two mosfet drivers:TC4421 and TC4422,inverter and no inverter.
In the half bridge, i use two power mosfets IRFP460.
The oscilattor and drivers are ok,delivering 15V signal to the power mosfets gates through 27ohms resistors.
The power mosfets are for maximum ratings: 500V(VDS) 20A(ID) and is is mounted over a good aluminium dissipators.
The problem is: The IRFP460 mosfets are going to get burst, when the power is turned on.
The low voltage power supply feeds 15Vdc and the high voltage power supply feeds 170Vdc to the D(drain) from mains 120Vac.
The first test was with 170Vdc in the D(drain) .it got burned
Then I did a second test, using a variac, feeding 50Vac to both low and high power supplys, resulting in a 72Vdc in the D(drain).
In this second test, I resolved to measure the drain current(ID) and the Vds(drain to source voltage) in one of the two power mosfets.
Thus, in this time, I got only one of the two power mosfets burned after a few seconds, I believe that the ammeter lead wire connections, did a unbalance on the two parts, resulting in it burns.
I am using a work 1.5uH work coil in parallel with a 376nf capacitor bank(resonance frequency in 212KHZ).
A 470nf DC blocking capacitor in series with a 45uH matching coupling inductor.
All this tests were made in a 30KHZ frequency , I did have no time to reach the resonance because the power mosfets got burned before that.
So, Somebody can give me a hand on it?
Regards