• State
  • Locked Locked
  • Replies 3 replies
  • Subscribers 65 subscribers
  • Views 6413 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

SG3524: Power on and SHUTDOWN test

AJEET KUMAR IIST
Prodigy 90 points
Part Number: SG3524

Hi,

SG3524 is designed for 50kHz signal in Flyback convertor mode to generate PWM. The PINS 3(oscillator output)  and 7 (CT ramp wave) are always present whethre SHDN is 0V or 1.1V.

1. Please let us know how to we confirm the controller is on or off.

Also, the Emitter output (Pin 11 $ 14) is driving the GATE of a MOSFET to run a flyback transformer. But Emitter output is not present. We are assuming as Current limitter (Pin 4) is not getting any feedback because transformer is not connected.

2. Please let us nkow how can we check for the output without connecting the transformer in the circuit to make sure GATE pulse is proper and parameters (Duty cycle) can be in our control.

For switching frequecy design, formula is given fosc = 1.3/(RT* CT)

But it is not coming practically as we have designed for fosc = 48kHz with RT = 2.7k and CT = 0.01uF

3. Please let us know the formula to design for fosc.

  • 0
    TI__Mastermind 26870 points
    Hello Ajeet,

    I have notified the appropriate team about your questions for your application. Please look for a response soon.

    Regards,
    Ulrich
  • 0
    TI__Intellectual 2230 points

    Hi Ajeet,

    Please see my answers below you questions:

    1. Please let us know how to we confirm the controller is on or off.

    The CT ramp wave will not disappear when SHDN is enabled, but the COMP will be pulled down to around 0V and PWM outputs will be shutdown when shutdown enable. You can check these signals to confirm the controller is on or off. 

    2. Please let us nkow how can we check for the output without connecting the transformer in the circuit to make sure GATE pulse is proper and parameters (Duty cycle) can be in our control.

    Apply a DC voltage to COMP and you should see the duty cycle change with the DC voltage if there are no faults.

    3. Please let us know the formula to design for fosc.

    The oscillator frequency can be calculated by fosc = 1.3/(RT* CT), and you can also refer to Figure 2 in the datasheet to select the frequency you need. Please notice that there is 5%(typ) standard deviation of frequency.

    Thanks

    Oliver

  • 0 in reply to Oliver Pan91
    Prodigy 90 points

    Thanks for the reply...

    For output frequency, we have used 2.2k, and 0.01uF to get 50kHz signal, which according to formula it is 59kHz.

    Thanks

    Ajeet