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Registered Member #61510
Joined: Fri Mar 10 2017, 09:30AM
Location:
Posts: 2
I have to design a flyback transformer for controlled charging of defibrillator capacitor.This is done by using a mosfet as a switch.Whenever the mosfet is turned on charging of capacitor occurs.the mosfet is controlled using PWM The following specification is used Max duty cycle:100% max energy stored:360j Charging time:7 sec primary voltage:12 V Secondary voltage:2000V How can I calculate the maximum ON time of the transistor. I have used the equation for inductance L= (2000V*ON TIME)/PEAK CURRENT PFA Thank you ]
transformer_design_for_charging_defibrillator_capa
citors1.pdf[/file]
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140
Starting with 'ballpark' figures;
360 Joules in 7 seconds = 52 W = 5.2 Adc average at battery = 10V (minimum) at 50% pwm that is about 21 A peak (x4) for the transistor and transformer primary, I guess a Litz wire or copper tape primary will help a little here.
Registered Member #61510
Joined: Fri Mar 10 2017, 09:30AM
Location:
Posts: 2
Thank you for the reply. Actually I have to charge the capacitor in a controlled manner. For eg: For 360J, the duty cycle is fixed as 100%, for 300j duty cycle is 90% for 200J it is 80% and so on. The transistor switching is controlled by the PWM output of the controller. So for 100% duty cycle how long should the transistor be turned on for charging the capacitor to 360j. I have to determine the ON period inorder to design the coil. L=(V*on time)/peak current
Registered Member #2989
Joined: Sun Jul 11 2010, 12:01AM
Location: UK
Posts: 94
Here are some links that I found helpfull.
for getting an idea of the transformer needed try the transformer may get hot
this is the controller chip (LT3751) I've used for a 24 to 800v cap charger also used SIC diode on the output ie woolfspeed
On the snubber design, maybe you could use a diode to put the leakage inductance energy from the primary to the output. Called boost-flyback or something.
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Design of flyback transformer for charging defibrillator capacitors
