Electronic – Inexpensive switching regulator with internal inductor & diode

If you're stuck using linear regulators, you can put big power resistors in series with the inputs of the regulators to drop the voltage and share some of the heat dissipation. You're dissipating the same amount of power either way, but it might make it easier to fit on your board or whatever.

If you're using an LM7833, for instance, and supplying 150 mA, the datasheet says the dropout is 2 V, so the input voltage has to always be above 5.3 V. From a 14 V supply at 150 mA, this is a 2 W, 56 Ω resistor. The resistor just needs air circulation around it, not a heatsink, and then your regulator only needs a 500 mW heatsink instead. The highest power dissipated in the regulator will be at the current when resistor and regulator are both dissipating the same power, which in this case is about 95 mA.

• Integrated DC-DC buck regulators for 12 Volts 1 Ampere do exist, from manufacturers like Recom, R-78C12-10. These are drop in replacements for the popular 7812 type linear regulators - thus, totally integrated packages, as desired.

• Yes: If your load is pulling 1 Ampere at 12 Volts with 22 Volt source, the regulator is dissipating (22 - 12) * 1 = 10 Watts as heat.

• If desired power quality is not met by the switching regulator chosen, a hybrid approach, such as using an adjustable integrated switching regulator set to 14 Volts or so, followed by a low drop-out linear regulator, would give the best of both worlds - low heat, yet low ripple.