Continue to Site

Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

H BRIDGE, what do you thing will happen here.

Status
Not open for further replies.

kinarfi

Well-Known Member
This is similar to what I call a relay race, What you think will happen as the input transverses from B to A and back, same for B to C & back?
NFETs are IRF2805 (175 amp), PFETs are paralleled IRF4905 (74 amp each).
Power is from a car battery + the alternator.
Will I have a short for a microsecond, will I fry FETs, Will I have a wonderful, power H bridge? Will it explode and kill me? :)
Your expert opinions will be appreciated.
 

Attachments

  • untitled.PNG
    untitled.PNG
    16.3 KB · Views: 170
You need Break before Make in both directions. Otherwise the shoot-through current spike can be huge (Ron of both P and N fets can be a few mOhm).

This is usually handled in software if driving the bridge from a micro, or by using a commercial H-Bridge driver IC, which includes the steering logic.
 
There are people who believe that a shoot through spike is OK for a few microseconds.

My experience is that it will work during testing and then fail after you have begun to depend on it. During bench testing, the current limit of your bench supply will protect the transistors. But when you put it in a vehicle, the current is virtually unlimited. If you are lucky it will blow up right away. The pieces of exploding MOSFET are small, so be sure to wear safety glasses. A fuse might prevent a fire, but it isn't fast enough to protect semiconductors.
 
the easiest thing to do is simply use H bridge driver IC's and be done with it. depending on what type you use there are many possible ways to drive an H bridge and have some level of shoot through and other safety features built right in to the design.
 
Status
Not open for further replies.

Latest threads

New Articles From Microcontroller Tips

Back
Top