# H-Bridge power calculation

Discussion in 'General Electronics Chat' started by ManeeshaN, May 11, 2010.

1. ### ManeeshaN Thread Starter New Member

Feb 17, 2010
8
0
Hi friends,

I am using H-Bridge LMD 18201(from National) in my design for controlling direction of motor movement. I wanted to know how do we exactly calculate the power dissipation of an H-Bridge. This H-Bridge uses 4 MOSFETS.

After some ground work this is what i found: Total Power dissipation of H-Bridge = Ptot = Pq + Pcond + Psw

Pq evice power consumption under quiescent, no load, conditions
= (Logic Supply Voltage x Logic Supply Current) + (Load supply Voltage x Load Supply Current (under no load conditions))

Conductive Power Dissipation, Pcond = 2 x Irms^2 x Rds(on)

Switching Power Dissipation, Psw(combination of energy dissipated by switches and protection diodes during the ON/OFF switching action.) = (Eon + Eoff) x F

Can anyone please tell me if this way of calculating power dissipation is correct.

2. ### mik3 Senior Member

Feb 4, 2008
4,846
63
Yes, it is a correct way to calculate the total power dissipation in a chip. You consider all the elements where power is dissipated and add them. Some of them might be negligible and you can ignore them.