Voltage-controlled Current-limited switcher circuit

  
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My product requires a voltage-controlled, current-limited power supply and for a number of years I have used various switcher chips with an op-amp to feed back a current sense voltage to the feedback pin. For the last couple of years I have been using an LM22680, but I seem to get variable results board to board. (Output voltage not consistent) I
Voltage-controlled Current-limited switcher circuit - schematic

supply my circuit with an off the shelf 24 VDC switching power supply and the idea is to drive a variable load at a maximum of 1 amp. I have used WebBench for the different circuits that I have used. 3) Is there a better solution I should pursue I have used an LM25010 in the past, but the 1. 25 amps proved to be too much current. Would it work in conjunction with the op-amp feedback circuit (According to the datasheet, their is a ripple voltage requirement at the feedback pin, that may not be provided by the op-amp. ) The boards are exactly the same. The only differences are the components and the solder connections. Some boards will generate 21 volts at 1 amp and others will only generate 18 volts at 1 amp, with the same 20 ohm load. The boards do have the same voltage unloaded. So, I suppose it could be the variation in resistance values of the op-amp feedback circuit, but those components are all from the same run, so it seems unlikely they would vary significantly. Something I forgot to mention: I have also seen significant variations in ripple voltage present on the output from board to board under the same load conditions. I think it`s safe to say, in general, I have had issues with National/TI switcher chips in the past that were "unofficially" acknowledged by National/TI support staff, who suggested I migrate to other devices. Being a small company that can`t afford to make a "market mistake" by delivering an...



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