Power dissipation

AN2650

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DocID14109 Rev 3

7.2

Static freewheeling

Only the RDS,on of the high and low side switches are used for free wheeling and

generating power dissipation.

7.3

Dynamic slew rate power dissipation

During the H-bridge switching, the voltage and the current chang in a triangular form with

the defined slew rate.

7.4

Power dissipation for one PWM phase

The temporary power dissipations, explained above, are summed for the complete PWM

phase.

PP

ON

t

Pulse

t

⁄

–

t

D

-------------------------------







P

FW

t

D

t

Pulse

t

⁄

–

–

t

D

-------------------------------------------







2P

SR

2t

⁄

⋅

t

D

-----------------







⋅⋅

+

⋅

+

⋅

=

PP

ON

t

D

2t

⁄

⋅

–

t

D

----------------------------







2P

SR

2

t

⁄

t

D

---------

⋅







⋅

⋅

+

⋅

=

P2 R

2

t

D

2t

⁄

⋅

–

t

D

----------------------------







⋅

2U I

t

⁄

t

D

---------







⋅⋅ ⋅

+

⋅⋅

=