ZVS driver not oscillating

Thread Starter

icantalktosneks

Joined Apr 23, 2021
22
1621690450740.png

As far as i can tell i am following this circuit, although different components. However, when connected to a DC supply, both LEDs light up dimly and there is no oscillation. It appears that the drains of the MOSFETs are connected together via the inductor and the Vgs of both MOSFETs are constant.
Without the LC tank, only one LED lights up, so I assume that means the MOSFETs are indeed working.
The components I am using are as follows:
MOSFETs: IRFP260N
Schottky diodes: UF4001
The resistors are normal 0603 SMD resistor, all values are as shown above
The capacitor is a MLCC, all values, are as shown above
The inductor is a toroid inductor, all values are as shown above
 

ericgibbs

Joined Jan 29, 2010
12,932
hi,
The LED's in that position are a bad idea.
What type, colour , forward voltage drop.?

You only have a 5V supply.
E

Clip from d/s
ESP_ 322.png
 

Thread Starter

icantalktosneks

Joined Apr 23, 2021
22
hi,
The LED's in that position are a bad idea.
What type, colour , forward voltage drop.?

You only have a 5V supply.
E

Clip from d/s
View attachment 239276
The LEDs are green with a forward voltage drop of 3.3V.
The voltage divider ensures around 4.54 volts are delivered to the gate of the MOSFET though, I can try with a proper DC power supply, but what voltage should i raise it to
 

ericgibbs

Joined Jan 29, 2010
12,932
hi,
Why have you removed the other inductors in the circuit.
We had the previous ZVS working OK, why have you changed.?

Do you understand how a centre tapped push/pull ZVS oscillator works.??

E
 

Attachments

ericgibbs

Joined Jan 29, 2010
12,932
hi,
What is the current path from the 5V supply to the Drains of the MOS and the L1 inductor.?
It has to flow via the Green LED's and the 100R , how can it draw sufficient current via a 20mA LED and 100R path.??

Compared to the current path of the previous circuit.?
E
Added the previous circuit for comparison.

ESP_ 324.png


ESP_ 325.png
 
Last edited:

Thread Starter

icantalktosneks

Joined Apr 23, 2021
22
hi,
What is the current path from the 5V supply to the Drains of the MOS and the L1 inductor.?
It has to flow via the Green LED's and the 100R , how can it draw sufficient current via a 20mA LED and 100R path.??

Compared to the current path of the previous circuit.?
E
Added the previous circuit for comparison.

View attachment 239278


View attachment 239280
im not quite sure i understand. According to the simulation, even with the LEDs, it should still oscillate though
 

ericgibbs

Joined Jan 29, 2010
12,932
hi ican,
I cannot see how that circuit would oscillate when using actual components, sometimes a simulation can be misleading as it does not map all the possible parameters of the components.

Do you have two transformers of the same type/specification on your work bench.??

E
 

Thread Starter

icantalktosneks

Joined Apr 23, 2021
22
hi ican,
I cannot see how that circuit would oscillate when using actual components, sometimes a simulation can be misleading as it does not map all the possible parameters of the components.

Do you have two transformers of the same type/specification on your work bench.??

E
I have a similar transformer but it should still oscillate with just the LC tank circuit right?
 
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