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Flyback charger circuit

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pavandanyasi

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Hai This is pavan .i am designing 65v/3amps flyback charger circuit with the reference circuit from PI.
when I connected the input supply through resistor (33ohms 10watt) in phase for protecting the circuit .when i switch on the supply the input current is going 3.5 amps .and resistor got very hot (burn). i thing some where short in primary side .but i am not clear what is the problem and how to find the exact problem . please tell me what is the problem . i have attached the circuit schematic .pls help me
Note: I did'not connect the zener diode (Vr1 160v) . because Vr1 is not available.
input voltage =110vac
output voltage=38vdc
input current =3.5amps This voltages i am getting
 

Please provide a reference to the schematic from 'PI'. Without it, the component references mean nothing.

Brian.
 

input supply through resistor (33ohms 10watt) in phase for protecting the circuit .when i switch on the supply the input current is going 3.5 amps .and resistor got very hot (burn).

From your description this is causing more than 300 W in the resistor, and so it burns.
 

input supply through resistor (33ohms 10watt) in phase for protecting the circuit .when i switch on the supply the input current is going 3.5 amps .and resistor got very hot (burn).

From your description this is causing more than 300 W in the resistor, and so it burns.
 

Hi,

This schematic diesn't help much, because it is not "your" schematic.
At least I don't find the 33 Ohms resistor you are talking about.

What does "for protecting the circuit" mean? Please describe with values like voltage and current.

Klaus
 

Hi,

This schematic diesn't help much, because it is not "your" schematic.
At least I don't find the 33 Ohms resistor you are talking about.

What does "for protecting the circuit" mean? Please describe with values like voltage and current.

Klaus
I Externally connected the resistor 33ohms in series of AC phase for protection .in case any fault occur in the circuit components will not damage . my problem is when i switch on the supply input current going to 3amps and my Topswitch ic going to blown
 

Hi,

I can´t see how a resistor in series with the input can help to protect something - in combination with a flyback SMPS.
Can you explain - and how did you calcualte the value.

I assume you don´t understand flyback input current vs input voltage behaviour:
--> The lower the input voltage, the higher the input current.

The higher the input current the higher the voltage drop across the resistor and thus the power dissipation of the resistor.
I assume instead of "protecting" anything with your resistor ... you increased the risk of fire.

Either
* use no doubtful "protection" at all, because the datasheet of the TOPSwitch-HX already shows protection features:
The TOPSwitch-HX Family also enables the design of power supplies with robust functionality and provides enhanced safety features such as output overvoltage protection, overload power limiting and hysteretic thermal protection.
.
* Or use a true protection device like a fuse.

In either case you have to follow the datasheet recommendations very strictly. Especially the part (value) selection and PCB layout.

Klaus
 

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