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Part Number: TPS23751
we have a TPS23751 low-cost design based on the PMP11254 (12V 2.1A), but are using the LinkCom transformer LDT8202-51R.
I am wondering how to calculate the allowable adapter voltage range? Is it strictly dependent on the transformer?
The datasheet for the transformer says 33-57V? We would want to go lower to support 24V inputs.
No the transformer is not the only component that sets the input voltage range.
Since you want a 12V/2.1A with a 24V input adapter design, please consider the PMP8812. It is exactly what you want.
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In reply to Michael Pahl:
the PMP8812 is not a low cost design. I would just like to understand what parameters determine the lowest possible input voltage when using adapter power. I will measure it on my design.
In reply to Michael Gilge:
The PMP8812 is the best starting place for the design you want. It is not listed as a cost optimized solution because it is a synchronous driven flyback. A cost optimized solution would be a diode rectified flyback, so the PMP8812 cannot compete with our other designs in this respect.
You could take the PMP8812 and make it low cost component by component, which in my opinion is easier than designing a new power stage but that is your call.
The following paper outlines how to design a flyback with one of our parts. To make it wide-Vin and a different device, just change the values in the parameters than the standard values. http://www.ti.com/lit/an/slva305c/slva305c.pdf
The biggest changes for a wide Vin design is the transformer, and the APD divider. You will want to ensure the bias winding is providing enough voltage for the IC to remain powered. Additionally the output inductance and the output capacitance should be checked to ensure the full load is available at the full input range and the ripple is not too high. You will also want to calculate the duty cycle for the full range of the input to ensure the design can support lower input voltages but not slip into DCM in higher input voltages.
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