View Full Version : ‘hot path’ in a H-bridge

11-11-2011, 11:43 AM
Hi, there,
I have aquestion: Hardware developers discuss about the difficulties of a so called ‘hot path’ in a H-bridge. Which kinds of difficulties are here discussed ?

11-11-2011, 11:45 AM
Provide an example.

This is probably the wrong forum.

11-11-2011, 12:09 PM
What I assume you are talking about is an incorrect data set that you can send to an H-Bridge resulting in a short circuit condition that will blow up the circuit. It is good practice when using these devices to make sure to include a Fail-safe either in code or hardware to allow this never to happen. Take a look at this (http://coolelectronics.wordpress.com/articles/h-bridge-theory/) web site, and look at the 4th picture down. It should be quite obvious what would happen in this instance.

11-11-2011, 01:02 PM
This is less an issue than it once was due to the speed of modern power transistors, but not only the LOGIC, but the "Turn-off" time of transistors must be considered in an H bridge circuit.

A transistor does not stop conducting immediately when you stop sending current or voltage to it. If you turn on the other same-side transistor too quickly, EVEN IF THE LOGIC is correct, you can still have power being conducted through the wrong paths... and something will POP.

Be sure to consider the on/off times of your power transistors,drive logic, and all capacitance in the circuit when you do an H-bridge design. A slight delay between the OFF time of one transistor and the on time of another on the same leg is a good idea. If you don't want to mess with the calculations... you can include a variable delay, and "Sneak up" on an optimum a little at a time.


Phil Pilgrim (PhiPi)
11-11-2011, 03:30 PM

Welcome to the forum!

If you want to explore the subject further with Google, use the term "shoot through" rather than "hot path". You might get more hits.