Q:

H-Bridge MOSFETS getting hot with no load

I have the following circuit:

The circuit is working fine, but the problem is that when there is no load, the IRF9540 are getting hot. When they are in load, they are cold. For sure, I think it's a problem with the gate-source resistors.
I measured the voltage drop between G-S on the IRF9540 and I have the following values: -3.5V in no load and ~-11V in load. 
I don't know how to tune the circit to remove this no-load heating, so I'm asking for your help. Thank you ! 

A:

The trouble lies in the design of the gate driver.  When transistor Q5 is off, resistors R1 and R3 form a voltage divider that sets the gates of Q1 and Q3 at half the supply voltage, nominally 6V.  This is enough to turn on both FETs at the same time, causing a current to flow through them.  Since you are measuring only -3.5V instead of -6V, it appears that the current is large enough to cause the supply voltage to sag.  The reason the P-channels are getting hot is they have lower trans-conductance than the N-channels, and are seeing the majority of the voltage drop.  
You need to re-design the gate driver so that only one of the FETs in each half-bridge can be on at a time.  The other FET must have its Vgs close to zero volts.

