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Help me fix my SMPS design

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Fragrance

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Hi All Friends

81_1192169432.jpg


So finally I made it working by doing simple multivabrator but problem is that when load fluctuate, or some thing goes wrong the Q3 base collector get short what I did just add capacitor 1nF between base and ground, any good solution well come to safe the transistor Q3

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Fragrance
 

monnoliv

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Re: Need Help with smps

Hi,
1. You don't have any voltage limitation @ the output, but that shoud be Ok IF you have a load (to be calculated).
2. @ switch off, 2N2222 will suffer overvoltage too due to serial stray inductor and high dI/dt.
Regards,
 

Fragrance

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Re: Need Help with smps

monnoliv said:
Hi,
1. You don't have any voltage limitation @ the output, but that shoud be Ok IF you have a load (to be calculated).
2. @ switch off, 2N2222 will suffer overvoltage too due to serial stray inductor and high dI/dt.
Regards,

ok so what is the solution for the overvoltage

regrads
Fragrance
 

monnoliv

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Re: Need Help with smps

Hi, one of the solutions can be: for the point
1. A zener diode rated @ max voltage and power when there is no load.
2. A compact design between Q3-D1-C3 (never mind about L1).
Regards,
 

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