Hi !
I want to make a DC-DC converter with TPS54302. It must output 14V from 16-18V at the input. The output must be limited to 1-1.5A.
Based on TI recommendations I came up with this schematic: TPS54302 Converter.pdf
As this is my first attempt to make a switching converter, I want to discuss it with you to make sure that everything is fine.
The current limitation circuit I took it from another TI document: SNVA532.pdf. But here it is uesed with other IC, the LM2596. Do you think it will work on TPS54302 too ? I adjusted the opamp amplification to output 1100 mV when the current is 1.5A on the shunt resistor. 500 mV is needed to turn on the 1N4148 diode and another 600 mV to compensate for the TPS reference voltage on the feedback pin. If the current on the output is greater than 1.5A, a small current will start flowing from opamp to the feedback pin, changing the feedback divisor and lowering the output voltage.
I also want to ask you if it's ok how I made the adjustment of the opamp gain, so that I can adjust the current limit ?

 

That's a lot of work and expense just to save ~1 to ~2 Watts of Heat-Dissipation.
I would work on something like making your Load tolerant to a ~17-Volt-Supply instead.
Or just using a standard and cheap Linear-Regulator.
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If you want to help me, please respect my desire and answer what I asked, not anything else. Thank you !

 

There's a bit of a snag with that design. . .
What happens if you short out the output? The op-amp circuits reduces the output voltage, until it reduces it down to 2.7V. Below 2.7V the op-amp will cease to function. What happens then?

 

That will not happen where I will use this circuit. It is not an universal power supply, It is used just to charge an AGM Battery. So the voltage will not drop more than 11V.

 

Where did "17-Volts" come from ????
Is this an AC-Mains-Transformer plus Bridge-Rectifier ?,
and, are You just trying to design a simple Battery-Charger ?
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It comes from a SMPS.
No, not a SIMPLE battery-charger. I want to design a good and conplex battery-charger.
If you want to suggest me to do it in other way, please don't ! I am ONLY interested in this particular circuit and not anything else.

 

That will not happen where I will use this circuit. It is not an universal power supply, It is used just to charge an AGM Battery. So the voltage will not drop more than 11V.

OK. Fair enough.
If it's a complex battery charger, how does it swap from Absorption to Float, and how is the Float voltage temperature compensated?
Have you considered the Texas's dedicated battery charger ICs?
https://www.ti.com/power-management...;Switch-Mode Buck-boost&338=Lead Acid&1152=6&

 

I have simulated the circuit in Tina-TI and without the current limiter I have a clean output voltage, but when the current limiter is activated I got to much ripple on the output voltage (400-500mV). Is this normal ? I don't like it al all...

 

I have simulated the circuit in Tina-TI and without the current limiter I have a clean output voltage, but when the current limiter is activated I got to much ripple on the output voltage (400-500mV). Is this normal ? I don't like it al all...

What frequency is the ripple?

 

I don't remember exactly, but I think is lower that 400KHz... I think around 100KHz. The simulation takes 25 minutes to do it again...