I would like to use the ZXLD1350 LED driver IC to provide constant current to some NiMH batteries to charge them.

However the negative terminal of the LEDs go to an inductor instead of ground.

My aim is to swap the LEDs below for my battery, however when ZXLD1350 is off, I need my negative battery terminal to go down to ground.

I tried making a circuit that does this with a depletion-mode P-MOS but they are quite hard to source and I'm not entirely sure if this is a viable way to do this.

Is there something else I can use instead of a depletion pmos?

Is there a better solution to this (assuming one has to use a led IC)

Here's an image of what I've designed so far:

  • \$\begingroup\$ A battery charging circuit needs to prevent batteries from being over-charged (and/or it needs to prevent too high a current when the battery is near full charge.) Lack of such protection is unsafe, and may lead to fire and/or explosion. What do you plan to use to make your charger safe? \$\endgroup\$ – Math Keeps Me Busy May 5 at 19:39
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    \$\begingroup\$ @math keeps me busy - in the case of NiMH it’s typically ok to trickle charge indefinitely at C/10 or below. \$\endgroup\$ – Frog May 5 at 19:44
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    \$\begingroup\$ @Frog. That is not my understanding. "As NiMH batteries are intolerant to overcharge, trickle charging tem has to be undertaken with care.... 0.1C...is considered too high for NiMH batteries and it is generally accepted that for most NiMH batteries trickle charging should be accomplished at a rate of about 0.05C...it is advisable not to leave them trickle charging for too long. It is better not to trickle charge and to replenish any self-discharge before use." electronics-notes.com/articles/electronic_components/… \$\endgroup\$ – Math Keeps Me Busy May 5 at 20:27
  • \$\begingroup\$ youe partial desigh has the mosfet in the wrong place ans is missing the flyback diode., \$\endgroup\$ – Jasen May 5 at 23:59
  • \$\begingroup\$ @MathKeepsMeBusy I will add a switch to kill the power, I'd like to first work out the constant current source section of my circuit \$\endgroup\$ – JC123 May 6 at 5:27

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