Heating solution for H bridge transistor circuits

I want to talk about one of the major cause of heating in  H bridge and half bridge circuits which finally leads to failure. Though transistors in H bridge or half bridge may fail for many reasons, the most common cause of failure is "NO or SHORT DEAD TIME".

 DEAD TIME OF H BRIDGE CIRCUIT

From the theory behind H bridge mosfets or H bridge transistor circuits, power is delivered to the load when two diagonal transistors turns on. That is either (B and C ) or (A and D) from the image above.

The H bridge circuit is divided into two sides: Left side and right side. One of the principles guarding all H bridge circuits is that:
NO TRANSISTORS FROM THE SAME SIDE SHOULD TURN ON AT THE SAME TIME. Eg. A and C  or B and D.

When transistors from same side turns on, a phenomenon called shoot through will occur and that will produce a blasting sound, nice smell and  beautiful smoke.

In order to avoid shoot through, H bridge and half bridge circuit should be driven in such a way that, transistors from same side does not turn on and also transistors are only turn on diagonally.

In other to ensure that transistors are turned on only diagonally,  a small delay time known as dead time is introduced in the switching circuit. The delay circuit is ensures that one diagonal switch side is completely turned off before the next diagonal turns on.

Heating solution for H bridge transistor circuits

 Heating in H bridge transistor as a result no or short dead time can be solved by

 

 

H BRIDGE

H Bridge circuit is the arrangement of electronic switches in a pattern that forms the letter ''H'' during switching. The switches may be bipolar transistors, Mosfets, IGBTs, etc. 

These switches are controlled by logic signals in such a way that the four arranged switched connected in "H" turns on diagonally as shown below:

In H bridge circuit, never should two switches on the same side eg. A and C or B and D be turned on at the same time.

Turning A and B or C and D on at the same time will create a bombing sound and all your mosfets or transistor will produce beautiful smoke with a nice smell......Hahaha

H BRIDGE CIRCUIT FOR INVERTERS

In inverter systems, H bridges are mostly used for pure sine inverters with only few modified sine wave inverters using them.

H bridge inverters are best for me especially when it comes to their way of charging your batteries until float level. The circuit below is an H bridge circuit which can handle 1000W to 3000W 12V, 1000W to 4000W 24V, 1000W to 5000W 48V.  

Before you use any mosfet, please make sure your highest switching voltage is less than the maximum operating voltage of your mosfets by at least half. 

Example 48V inverters should use at least 100V mosfets using 75V may result in failure.

H BRIDGE DRIVER CIRCUIT

Click to View

CLICK TO VIEW

NB. without the addition of surge capacitors or not adding enough, your pure sine inverter will fail on inductive loads eg. fridges, air conditioners etc.

You can assume that 10000uf is for every 1000W.

There is something I omitted, that is a fast switching diode paralleled with a 47ohms resistor to feed the high sides and the low sides gates. 

Connect this in series to the output of your driver stage before connecting it to this H bridge. Its another form of protection against failure. 
Read more about this by clicking this link
http://manycircuits.blogspot.com/2017/05/mosfet-heating-solution-for-h-bridge.html