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Part Number: UC3843A
Hi. I am making a boost DC/DC converter from 12VDC to 27.8VDC@100mA with adjustable output voltage from 24v@30mA to 30@160mA.
Power source - battery. Depending on the level of charge, it produces a different voltage. When fully charged - 13v, and with a full discharge of 10v. Also, sometimes the device is connected to the power supply unit for 19 volts. When the input voltage changes or when the output voltage is adjusted, the controller skips the operating cycles. It looks like this:
How to fix it? what is it "slope compensation" why is it needed and what does it do and how calculate R7? I have made it but I don't understand. Is feedback compensation necessary if there is an slope compensation? how to calculate the values of feedback compensation elements?
Hi User, Thanks for your interest in UC3843A. I would recommend taking a look at section 3 of this application note: www.ti.com/.../slup317.pdf. There is a section explaining slope compensation on page 17. Slope compensation is typically necessary for current mode control devices to avoid sub harmonic oscillation. This can become an issue when you operate above 50% duty cycle. You will still need feedback compensation even with slope compensation. Page 10 of this document provides some guidance for setting compensation components for current mode control boost: www.ti.com/.../slup340.pdf. What are the red and teal waveforms in the images you shared? Also could you explain how you are adjusting the input voltage and output voltage in your simulation? Best Regards,Ben Lough
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In reply to Benjamin Lough:
no. I read this very useful document www.ti.com/.../slup340.pdf and try to figure it out. I also found one interesting fact. If you change the control circuit of the gate of the FET to this one. That device begins to work stably in those modes in which stability before it could not be achieved. I think that this is all due to current emissions when the transistor is opened. This circuit tightens the opening of the transistor and the current ejection decreases. So maybe it's not about correcting the feedback but in the current needles on the current sensor?
In reply to user5213571:
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