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which switching pattern for DC brush motor ?

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anotherbrick

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hello dear forum,

I drive a 24V dc brush motor with H bridge

switching.JPG

I use switching pattern 1 but this time the lower MOSs get hot, upper stay cold
can I use switching pattern 2 ?
what is advantage or disadvantage of pattern 2 ?

please advise

thank you
 

Hi,

read about
* slow decay (1) --> better RPM control
* fast decay (2) --> better torque control

Klaus
 
Message #1 contains very little information.

What is the PWM Switching Frequency?
What is the Duty Cycle?
I assume, the Dead-Time is correct?
How many Amps flows through the Motor?
What is the ON Resistance of the MOSFETS?
Do you have heat sinks on those MOSFETS?
Do you have external reverse bias diodes?
URL for the MOSFET Datasheet?

PWM Pattern #1 ...
Q3 is never used = COLD
Q1 and Q4 are used during ON-TIME
Q2 and Q4 are used during OFF-TIME ( Braking ) <= these two (2) MOSFET's are getting HOT

Pattern #1 and Pattern #2 should both work well.
Pattern #2 has higher switching losses.
Both patterns are Slow Decay, neither is Fast Decay

It is difficult to determine what you are doing wrong.
 

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