20A smps battery charger

Thread Starter

freeman3020

Joined Jun 18, 2017
34
Hi all

I designed 20A charger using tl494 ,the problem mosfet damaged many time one I connect mains rectified DC volt, also IC damaged,
I tried circuit without feedback many time so duty cycle 45% without any problem, I think when duty cycle close to 0 , mosfet bomb ,I think I need some component for protection
 

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tcmtech

Joined Nov 4, 2013
2,867
The biggest issue I can come up with is that given you are using a push-pull type driver circuit on a a rectified mains voltage source each switching device is being subjected to 2X the Dc rail voltage before any transient spike voltages beyond that peak are added on which in a typical push-pull type power circuit they can be substantial. Push-pull switching circuits are best suited to lower voltage applications and you are operating them with a much higher voltage.

Ideally at a line voltages you should be using a H-bridge switching circuit so that transient spikes can be bypassed back into the DC rails and absorbed by the main filter capacitor where they can't build up high enough to do damage to any of the switching devices.
 

Thread Starter

freeman3020

Joined Jun 18, 2017
34
The biggest issue I can come up with is that given you are using a push-pull type driver circuit on a a rectified mains voltage source each switching device is being subjected to 2X the Dc rail voltage before any transient spike voltages beyond that peak are added on which in a typical push-pull type power circuit they can be substantial. Push-pull switching circuits are best suited to lower voltage applications and you are operating them with a much higher voltage.

Ideally at a line voltages you should be using a H-bridge switching circuit so that transient spikes can be bypassed back into the DC rails and absorbed by the main filter capacitor where they can't build up high enough to do damage to any of the switching devices.

so you think we can't solve this problem easily , is using high voltage mosfet solve problem , or add capacitor between transformer terminal
 

tcmtech

Joined Nov 4, 2013
2,867
If it was me I would just change the circuit over to a H-bridge design simply for the added robustness factors you gain from it.

Theres a reason that circuit design is typically not used in higher input voltage power supplies.
 

Dodgydave

Joined Jun 22, 2012
10,139
Hi all

I designed 20A charger using tl494 ,the problem mosfet damaged many time one I connect mains rectified DC volt, also IC damaged,
I tried circuit without feedback many time so duty cycle 45% without any problem, I think when duty cycle close to 0 , mosfet bomb ,I think I need some component for protection
Set the pwm duty to 60/75 and use the Tl431 to regulate the output voltage with the opto-coupler.
 
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