How do I spot a blown LED?

[ReeceyBurger123]

Re: How do I spot a blown LED?

It doesn't turn on in the first place tom it wont because the circuit for the rest of the bulbs wont be fully complete as it wont be going back into the booster there for it wont fire on.

[budm]

Re: How do I spot a blown LED?

The boost will turn on first and then the error will kick in when the Boosted Voltage is too high due to open circuit (open LED) otherwise how would the detection circuit knows that you have bad LED without applying enough Voltage high enough to run on the LED and see if there is current draw or too much current draw before shutting down the circuit?
It functions the same for CCFL inverter circuit, the shutdown circuit will kick in if the it does not detect the CCFL (OPEN HIGH Voltage due to no load), the inverter will try to fire up the lamp with >2KV first then the the dection circuit kicks in if there is error.

[ReeceyBurger123]

Re: How do I spot a blown LED?

Ok I guess that either my multimeter is too slow to pick that sudden charge up when it first fires thats why I need a scope but just saving the money to get one when I do dare say wont be long before I get another one of these craps in and I will check and see if the booster starts or not.

[budm]

Re: How do I spot a blown LED?

Typical protection of LED driver circuit.
OB3350 protection:
OVP Protection:
OB3350 shuts down the output if the output voltage is higher than the predetermined threshold level. In case of LED failing, the current of LED and the resulted voltage drop on sensing resistor is nearly zero; the converter will run at maximum duty cycle that boosts the output voltage to a very high level. To prevent this happen, the output voltage is monitored through Pin OVP and converter is shut down if the output voltage exceeds the predetermined level. This protection is latched and OB3350 can be reset from VIN or PWM.

VOUT SHORT Protection:
VOUT short condition is monitored by the voltage at pins OVP.
During normal operation, when the voltage at OVP pin drops below a threshold of approximately 0.2V, the VOUT-short protection function is activated and the GATE is turned off.
This state is latched and can be reset from VIN or PWM.

Thermal Shutdown:
The OB3350 includes a thermal protection circuit.
When the junction temperature exceeds 160°C
(typical), the controller and current sources shut down and do not restart until the junction temperature drops below 140°C (typical).

[ReeceyBurger123]

Re: How do I spot a blown LED?

Thanks for the info budm going to get reading