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Boost Output Protection Explained






Nice article, I almost made it through the third paragraph without wishing for a flexV8 with 2.2V to 12V input and up to 7V 4A output & aluminum board with built in heatsink connection points.

Seriously good article though.
 
Yeah it's aimed at the new members that may not know
why their boost driver went into self-destruct...


Jerry

You can contact us at any time on our Website: J.BAUER Electronics
 
TI has some great learning resources, just gotta sift through 'em all. Good find, Jerry :-) Zeniers are one of my favorite components, but mainly because of the name and their weird personality. Always havin' breakdowns :p
 
:thanks:
I posted it more for the detailed explanation of what
occurs and why when the output of a Boost Driver is
unloaded/open rather than showing a method of protection...


Jerry

You can contact us at any time on our Website: J.BAUER Electronics
 
Putting a zener diode over the output is a good idea indeed, and will prevent blowing up the boost driver in case of a load disconnect. Adding the resistor may take some of the heat off the zener diode.

But in all cases it is important to consider the wattage rating of the zener diode and resistor. If you are boosting power for a 445 driven at 1.5 amps, your zener diode would probably be 7.2 volts or something in that order. Pushing 1.5 amps, that would result in a whopping dissipation of 10 watts, something a typical zender diode rated at ~1 watt will not survive for long.

If your boost converter has an enable pin, it would probably be better to detect the over-voltage condition and shut it down. It may power up again when the output caps charge drains, but will kick into protection as soon as the driver starts to ramp up the voltage again.
 
The resistor isn't to take heat off the Zener, it becomes the new sense resistor when current flows through the Zener. Make it a high value and the driver will regulate a few ma through the Zener, which it can handle all day.
 
Sorry, I just had to comment on how I got a chuckle seeing BenM reply, and then another BenM reply.

zeener...
zeenyer...
zeen-eeyay?
 
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