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Burned schottky diode

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r2m

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Hi,
I use a PWN circuit to run a DC motor
the motor uses less then 10A and the circuit components are a 50A mosfet and a 3A schottkey as a flyback diode.

But...

The diode is burning when the motor is on heavy load and I cannot understand why.

The mosfet is kia50n03 and the diode is ss34, I'm using 16V from lithium cells and a 775 motor.
Help?..
 

Hi,

Please post complete schematic and application details like switching frequency...

the motor uses less then 10A
Give more details. Is this the average current, or peak current....

When I google for "775 motor" then there are many different results

Klaus
 

Hi,

Please post complete schematic and application details like switching frequency...


Give more details. Is this the average current, or peak current....

When I google for "775 motor" then there are many different results

Klaus


Hi
Thanks for the reply.
Unfortunately, I don't have the schematic since it is not self made, i bought it, but it is a standard PWM circuit
DC-motor-speed-governor-PWM-speed-regulation-LED-dimming-10A-5V-16V-ultra-high-linearity-band.jp.jpg

I said less then 10A because I'm almost sure my batteries cannot supply more then that..
I'm starting to think maybe the 40V limit of the schottky is the problem and not the current.
By the way, it started when the motor was loaded, almost stalled.
 

Hi,

Unknown circuit, no useful informations about current --> impossible to give good advice.

I'm starting to think maybe the 40V limit of the schottky is the problem
Surely not.

Klaus
 

If the frequency is high enough, the average current in the diode will be equal to the motor current when the duty cycle is 50%.
That is just an example, I don't know which duty cycle and motor load that will give the maximum current in the diode.
It seems that the diode is underrated.
 

Many Schottky devices are not avalanche-rugged.

The 3A rating, if this is the low side catch-diode of
a cheap buck controller, seems inadequate against
your 10A motor current (which it must carry for the
duration of the "low" phase, violating a time-averaged
If rating at anything over 30% duty at 10A).

'Scope waveforms ought to tell whether this is a
current or voltage induced failure. A finger on the
rectifier will tell you if it's power dissipation. Heh.

Which, 10A*1V*(1-duty), can't be ignored either.
What the datasheet says can be handled for V (I=0)
and I (V=Vf+?) is not what can be handled at once
and what can be handled, depends on how helpful you
were regarding cooling.
 

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