LM317 input to output voltage difference allowed is 35 volts maximum. If there is input bypass, which means if there r any capacitors across the supply of the driver(which is quite possible), they will short the output for a very short time. This condition will drop more than 35 volts across the 317 and will become RIP.
On a second thought, why not use a resistor.
Gajanan Phadte
On a second thought, why not use a resistor.
Gajanan Phadte
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Be careful with MOST regulators. It is very easy to exceed Vin-Vout without thinking about it.
If you assume that the load will have a capacitor across the supply - then Vout at Switch-On will invariably be 0V all-be-it for only a short period of time.
If Vin exceeds 40V with Vout = 0V then the 317 regulator will DIE.
Most of simplistic solutions will be destroyed if there is a bypass cap: when you connect the supply, the cap is not charged, and zener/pseudo-zener/regulator will have to sustain the full charging voltage and current, for some microseconds or milliseconds.
This is normally sufficient to destroy them, if not the first time then after a reasonable number of attempts.
5v 100ma? 10mm 1w amber+white+R, which is 2v+3v and a tiny current drop for protection. That seems a bit more elegant than lighting up black diodes. 
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5v zener + R parallel to another 5v zener + R parallel to another 5v zener + R, but unfortunately, diode current handling doesn't double in parallel, it only increase 1.5x.
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Or a series string of 1n5407, since their surge capacity can fairly easily handle charge up of the bypass caps.
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5v zener + R parallel to another 5v zener + R parallel to another 5v zener + R, but unfortunately, diode current handling doesn't double in parallel, it only increase 1.5x.
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Or a series string of 1n5407, since their surge capacity can fairly easily handle charge up of the bypass caps.
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