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I have AC 85-265V to 0.3A 8-12W DC 22-40V Internal constant current power supply for LED spot lights. This is the exact model https://www.lightinthebox.com/en/p/0-3a-8-12w-dc-22-40v-to-ac-85-265v-internal-constant-current-power-supply-driver-for-led-spot-lights_p1875439.html?prm=1.18.104.0

When connected to the AC main (120v) the driver short circuits by the AC connection points, resulting in a large spark and destroyed driver. However, this does not occur if the DC output is wired to a 32v LED chip, and the driver works fine.

Questions. Are internal constant current drivers required to be connected to a load (eg. LED COB) before the AC current is switched on?

If this is the case, how would I prevent the driver from short-circuiting in the event that the LED chip dies?

Any help or insight on why this is happening would be appreciated, thank you.

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  • \$\begingroup\$ Wonder why they reduced the price to $2 . No instruction guide? \$\endgroup\$ – Sunnyskyguy EE75 Oct 5 '18 at 7:48
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Are internal constant current drivers required to be connected to a load (eg. LED COB) before the AC current is switched on?

In this case, apparently yes.

If this is the case, how would I prevent the driver from short-circuiting in the event that the LED chip dies?

You would need to put some sort of voltage limiter in parallel with the LED. But if the LED dies, this limiter will have to dissipate the same power (actually, slightly more) as the LED itself.

It sounds like the design cuts too many corners in order to cut cost; they've eliminated any sort of proper voltage limit in the switchmode controller. If the load goes open-circuit, the voltage just keeps rising until something inside the driver fails.

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  • \$\begingroup\$ Dave, I used a string of 5 watt zeners in parallel with a variable load (MOV testing). The zeners in series were set to clamp at a voltage just above a normal "high" load, so the feedback loop was not broken. \$\endgroup\$ – Sparky256 Oct 5 '18 at 2:23

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