Involvement:Expert (understands the inner workings) - Ownership:1 week to 1 month
These units are small (17mm diameter, 3mm (approx) height) and easy to use if you have a good soldering iron.
They provide good efficiency if Vin is close to Vout (4*NiMh with a 3.5 to 4.0Vf LED, for exemple).
Reverse polarity protection is efficient and does not reduce performance (only the current needed by the chip itself flows thru the diode. The diode Vdrop is +/-0.5V while the AMC7135 regulates down to 2.7V, so it will regulate down to 3.2V which is enough for most power LEDs)
Price is low.
These circuit boards require proper heat dissipation.
They are inefficient if the input voltage is much higher than the output(under 75% afficiency) and run hot in this case.
10% output accurency may be a problem in some cases (1000mA Imax LEDs for exemple).
I glued mines with Loctite thermal adhesive compound (one little drop on each chip cover) upside down, this provides cooling and holding. And with a little 1.5mm hole on the board, you can have all 4 wires on the same side.
The way they work (linear regulator) can be a problem at high input voltage (more than 5V), but in fact it is not, because with 4*1.2V NiMh you have 3.6V to 5.6V Vin.
Buying 4*AMC7135 boards can be a better choice, so you can remove some chips to have the desired current (and also some spare chips for some mods...)
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