PWM TL594

  • Thread starter billy fok
  • Start date
  • #1
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i have set up the circuit, but i do have some problem that i can't figure it out..

  • my frequency requirement is 20khz, i do follow the formula that the data sheet given, base on my oscilloscope, it shown 10khz.. capacitor voltage is 0.01 micro. resistor value is 5.5k ohms.
  • when i connect the the potentiometer, i can't adjust the duty cycle at all..
I have attach
  • my circuit output oscilloscope result.
  • circuit that i set up
  • and datasheet, it content the formula that i use..
data sheet for TL594
please give me some advice on this..
 

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Answers and Replies

  • #3
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explain pls
 
  • #4
Svein
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explain pls
I just got you a schematic that works. Start with that and experiment with component values.
 
  • #5
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so the output will be pwm signal and i able to adjust the duty cycle???
 
  • #7
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hi

may I know how to determine the ferrite core transformer??? pls help
 
  • #9
702
34
First, build everything to the left - No MOSFETS / transformer....
Spend time with the resulting circuit until you are satisfied it's working. Then, add the MOSFETS with transformer, but no output rectifiers. Be careful as you explore this configuration as the mosfets are likely to be damaged by small errors.

For the transformer, I would look up coiltronic's VersaPak. These are designed to help beginners get working power supplies and have support documents.

With the transformer, but no rectifiers, study the voltage waveforms on the drain of each MOSFET. You will see voltage spikes when each MOSFET is turned off. Adding a resistive load to the output of the transformer, you'll see these spikes become worse. What you're seeing is the energy stored in the leakage inductance of the transformer. Search under the word snubber to find circuits that can absorb the energy so that it doesn't harm your mosfets.

Next, add your rectifiers. There are issues with rectifiers in that they don't turn off immediately and this will cause ringing and voltage spikes. Again, snubbers across your rectifiers will help. Also, experiment with the rectifiers. Different ones behave radically different.

Spend time, pace yourself, and this circuit can bring a great deal of wisdom :-)
 
  • #10
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it can fit for closed loop right??
 
  • #13
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Yes.
base on the circuit, what is voltage error???? is a diode or???
 
  • #15
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The symbol indicates a LED.
may i know what is the purpose of the transformer??
 
  • #16
Svein
Science Advisor
Insights Author
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may i know what is the purpose of the transformer??
  1. Galvanic isolation (no wires between the output voltage and the inputs)
  2. The circuit will not work without a transformer.
 
  • #17
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  1. Galvanic isolation (no wires between the output voltage and the inputs)
  2. The circuit will not work without a transformer.
hi... i just build up the circuit without the mosfet. am i alright to say that, there will be not output at all????
would you mind recommend 1 transformer to me??? I been looking the transformer that you recommend to me. i should be looking at the DC-DC transformer. and 30 Watt POE+ Power Transformers For Akros Silicon AS1135 will be my choice...

can i choose circuit B???

Hope hear from you soon!!
 

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