ZVS driver drawing too much current

Thread Starter

icantalktosneks

Joined Apr 23, 2021
35
Lately, I've been trying to build a ZVS circuit that follows the schematic shown below
1640002065043.png

However, when I actually attach a DC power supply that can supply up to 5A @ 30VDC, and crank is past a certain limit, power supply indicator switches from constant voltage to constant current and the voltage drops.
At first, after only around 8V, the power supply changes to constant current and the input voltage drops to 3V and the current draw becomes 153mA
After removing the transformer, the limit changes to around 15V
After removing the capacitor, the power supply no longer switches to constant current at all.

The thing is, I've done this exact circuit before and it worked perfectly. My question is, what is causing such a problem?

Attached below is the list of components, and the LTSpice file
NPN MOSFETs: IRFP260N
Schottky diodes: UF4007
Capacitor: WIMA MKP 0.1uF rated at 250VDC
Resistors: 100Ω 5W cement resistors and 10kΩ through-hole resistors
 

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Last edited:

Alec_t

Joined Sep 17, 2013
12,734
Welcome to AAC!
The asc schematic simulates fine. I see no obvious error there, so that points to there being a wiring error or short circuit (C1, M1, M2 ??).
 

ronsimpson

Joined Oct 7, 2019
2,005
You have almost the maximum voltage on the Gates.
What do you have for L3 100uH? Spice does not know about core saturation.
I see the start up current is large.
 

Thread Starter

icantalktosneks

Joined Apr 23, 2021
35
Welcome to AAC!
The asc schematic simulates fine. I see no obvious error there, so that points to there being a wiring error or short circuit (C1, M1, M2 ??).
Without the transformer, the everything works fine (e.g. only one of the MOSFETs turn on, hence I suspect something to do with the startup)
 

ronsimpson

Joined Oct 7, 2019
2,005
Would the maximum voltage at the gates be an issue? Should I add a 5V zener diode?
R1,2 10k, could be smaller to bring down the voltage to 15V or 18V. Make a voltage divider with R3,4. But that is not why you are having a startup problem.
I use a toroid coil for L3
So all I learned is that you made it. Can you send a picture? From here I cannot tell if the coil or transformer or the inductor is in saturation.
In the SPICE file the capacitors are 10pF?
 

Thread Starter

icantalktosneks

Joined Apr 23, 2021
35
R1,2 10k, could be smaller to bring down the voltage to 15V or 18V. Make a voltage divider with R3,4. But that is not why you are having a startup problem.

So all I learned is that you made it. Can you send a picture? From here I cannot tell if the coil or transformer or the inductor is in saturation.
In the SPICE file the capacitors are 10pF?
I bought the inductor of taobao, and the capacitor should be 0.1uF in the SPICE file
 

ronsimpson

Joined Oct 7, 2019
2,005
After removing the transformer, the limit changes to around 15V
There is a chance that your diodes on the output are not right.
On the other hand it pulls too much in the "removed transformer mode". This indicates there is a problem without the diodes.
What is getting hot in this mode?
 

Thread Starter

icantalktosneks

Joined Apr 23, 2021
35
There is a chance that your diodes on the output are not right.
On the other hand it pulls too much in the "removed transformer mode". This indicates there is a problem without the diodes.
What is getting hot in this mode?
The current limiting resistors to the gates of the MOSFETs get warm after a while
The diodes seem to be connected correctly?
 

Thread Starter

icantalktosneks

Joined Apr 23, 2021
35
There is a chance that your diodes on the output are not right.
On the other hand it pulls too much in the "removed transformer mode". This indicates there is a problem without the diodes.
What is getting hot in this mode?
when i set the power supply to 12V @2A, the circuits emit a soft whining sound and the power supply goes into constant current mode again
 

Thread Starter

icantalktosneks

Joined Apr 23, 2021
35
Hi I'm back, this time with the solution.
I'm still not entirely sure whether the inductor or transformer were saturated, but I resoldered the primary side of the transformer and it seems to work now.
I set the input up to 20V@2A, and it has a static current draw of around 1.1A
 
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