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Registered Member #1412
Joined: Thu Mar 27 2008, 04:07PM
Location: Taipei Taiwan
Posts: 278
Hi,I am building a royer type induction heater based on this design. schematic: but I found a few problems.The gate drive waveform is not a sine wave.Is this correct?
The secondary of my matching transformer get hot fast.With load it consume 2.17A,without load it consume 0.9A(@64V input)
I made a few substitution:I use RHR15120 for D1 and D2,G40N60B3 for Q1 and Q2,HER308 for D5.
Other detail:resonant capacitor is two 0.68uF capacitor connected in serial.matching transformer is 11+11 turns primary vs 4turns secondary on ETD54 core.Current limiting inductor is 35 turns litz wire on CH467060 core.
Can I solve the secondary heating problem without making a new transformer?
Registered Member #3900
Joined: Thu May 19 2011, 08:28PM
Location:
Posts: 600
In the scope picture, the top trace is the tank voltage, but what are the bottom two? If they're the gates then you have way too much resistance. The gates act as capacitors and you want a nice square wave. Not some rc time constant junk. The voltage across each drain should be a nice half sine wave, alternating.
Get rid of that matching transformer. Or at least make it on a CRT fbt core. To cut it out entirely you can center tap the work coil itself.
Registered Member #1412
Joined: Thu Mar 27 2008, 04:07PM
Location: Taipei Taiwan
Posts: 278
ben123324 wrote ...
In the scope picture, the top trace is the tank voltage, but what are the bottom two? If they're the gates then you have way too much resistance. The gates act as capacitors and you want a nice square wave. Not some rc time constant junk. The voltage across each drain should be a nice half sine wave, alternating.
Get rid of that matching transformer. Or at least make it on a CRT fbt core. To cut it out entirely you can center tap the work coil itself.
Hth
Yes the pink and blue trace are the gates. So which resistor should I decrease?R1.R2.R3.R4?
Why FBT core?I don't have any unwanted FBT but I have some much bigger EE or EI core(from an arc welder).Why some people use matching transformer and some didn't?
And how can I improve power coupling between work piece and my circuit?
Registered Member #3900
Joined: Thu May 19 2011, 08:28PM
Location:
Posts: 600
well this is your average mazzilli driver:
and the resistance depends on frequency, but you don't want the time constant to alter the nice clean square wave you should be getting. the gate resistors are the ones in series with the gate capacitance, the other two are simply pull down.
the reason i told you to get a fbt is because of your heating issues. it would solve them as long as you use the correct wire rating(which would now fit on the core with decent airflow)
here is the induction heating design marko came up with:
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Royer induction heater waveform problem
