When Regulators Just Won’t Cut It

Now here’s a cool part that anyone interested in electronics should know about: the V-Infinity V78xx. These small devices are DC-DC buck converters which can source up to 2A and are designed as drop-in replacements for TO-220 package linear regulators:

V-Infinity V7803-500

Why use these over standard regulators? Efficiency. A standard linear regulator reduces a given input voltage while maintaining roughly the same current from input to output. Thus, the efficiency of such a device is approximately equivalent to the output voltage divided by the input voltage. So if you wanted to regulate a 4.75V source (three AA batteries, for example) down to 3.3V, your best-case efficiency would be 3.3/4.75 = 69%. In reality this number will be slightly lower because power is consumed by the regulator’s control circuitry. Either way, this figure is pretty poor, and leads to significant power loss at high load. The following graphs compare the efficiencies and losses of a standard regulator and the V-Infinity V7803-500 (where Vin = 4.75V and Vout = 3.3V):

Efficiency Comparison (Vin = 4.75, Vout = 3.3)Power Loss Comparison (Vin = 4.75, Vout = 3.3)These results look pretty impressive to me. If we’re pulling 500mA at 3.3V, the losses in the V-Infinity converter are only 183mW – just a quarter of the 730mW lost by the regulator. What this means: no heat sink required.

So what’s the catch? Price. A single 3.3V linear regulator can be had for just one of your dollars. The V7803-500, at the time of this writing, costs $6.12. So is it worth getting? Well, that depends on your application. If we’re talking battery power, these devices may greatly extend the life of your device. If your project is running on mains power, perhaps regulators are fine, but DC-DC converters could help save the planet. The power is yours!

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6 Responses to When Regulators Just Won’t Cut It

  1. Craig says:

    Dimension Engineering also do switchmode regulators designed as a drop-in for 78-series linear regulators. I’ve used a couple with good results, but I’m not sure how the price compares to the V-Infinity units.

    • Mike says:

      Cool, thanks for letting me know! Their 25W, 3A adjustable switching regulator looks very impressive. The price is a little high, but for that capability it’s really neat.

  2. Luke Olson says:

    Thanks for turning me on to this IC. I’m pretty new to electronics and have been messing with small AVR projects. Recently I discovered how inefficient the 7805 was and was really disappointed. The Dimension Engineering product looked good until I saw the price of $15 which is too much in my opinion. A little over $6 I can do!

  3. Pingback: Experimenting with Buck Converters | Non-Lexical Vocables

  4. M. Joshi says:

    Just in-case someone else is reading this useful blog like me, the V-Infinity V78xx series DC-DC buck converters have now been rebranded by their parent company CUI Inc.:


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