# Short circuit protection for a boost converter

Is it possible to add short circuit protection to a boost converter?

My initial instinct was no, as the switch does not directly control the input to the inductor and this means the minimum output is Vin or so.

But are there ways to protect such a converter?

• What topology are you using? Jan 20, 2011 at 2:22
• @reemrevnivek A simple SMPS boost converter. Is there a specific topology? Jan 20, 2011 at 13:23
• There are several. You can have the basic design (not sure what it's called but I'm 90% sure it's what you're referring to), but there's also SEPIC, Ćuk, inverting buck/boost, isolated (noniverting) buck/boost, switched capacitor, and there are probably more. There's definitely more than one way to do the job. See dren.dk's answer. Jan 22, 2011 at 0:53

Here's a linear tech app note http://cds.linear.com/docs/Design%20Note/dn154f.pdf

If you're not using much current, sometimes a simple solution is to just use a thermal fuse in front of the converter, or even a simple lm317 type current limiter. The second will give you a voltage drop, which may or may not be a problem. Another easy solution is a good current limited voltage regulator in front of the boost converter and dedicated only to the boost converter, so if there is a short it doesn't bring the rest of your rail down.

In boost PFC applications, there is peak current limiting usually through a combination of two current transformers (one sensing the switch current, the other sensing the diode current) which works by collapsing the duty cycle of the converter, reducing the output voltage and (if the load is not CC) the current.

There is no way to protect against a hard short except for opening some sort of limiting device (i.e. fuse)

The problem with boost converters is there is a DC path through the diode, so shutting off he converter doesn't stop the DC path. A seperate overcurrent protection circuit is usually the only solution.

• For such a circuit, what would you suggest? I was thinking of a polyswitch/resettable fuse (suggested by bt2) as the supply may be occasionally short circuited. It is for surge testing a device against a 60V transient which could be continuous. Jan 20, 2011 at 14:27
• You need to evaluate worst-case conditions, and in particular how much power your supply can provide. Semiconductors often fail before a polyfuse trips, unless they are suitably over-rated and have enough thermal mass to tough it out until the fuse trips. Jan 20, 2011 at 18:51

A SEPIC converter can be current limited, here's an example: http://dren.dk/carpower.html