Protecting led lights

[BERT T]

I have been looking at the effects of 12v led lamps being supplied with a slightly higher than normal voltage, such as when running the engine or connected to shore power to charge the batteries where the voltage can rise to around 14.3 volts. Apparently this can reduce the life of the led lamps quite considerably so I am wondering is it worth fitting a regulated supply something like this: http://www.ebay.co.uk/itm/DC-8-40V-...o=SIC.MBE&ao=1&asc=20140107083358&meid=543c0a especially for any lamps that are on the mast.

 

[sailorman]

2 yrs on mine are ok with charger & engine

 

[alahol2]

See this thread also... http://www.ybw.com/forums/showthread.php?419939-LED-power-supply

 

[jdc]

I have been looking at the effects of 12v led lamps being supplied with a slightly higher than normal voltage, such as when running the engine or connected to shore power to charge the batteries where the voltage can rise to around 14.3 volts. Apparently this can reduce the life of the led lamps quite considerably so I am wondering is it worth fitting a regulated supply something like this: http://www.ebay.co.uk/itm/DC-8-40V-...o=SIC.MBE&ao=1&asc=20140107083358&meid=543c0a especially for any lamps that are on the mast.

It's extremely difficult to conceive of a good (or even half competent) design of power supply or load resistor for an LED which would be 100% ok at 12V and fail at 14.3V, particularly for a 12V system where 14.4 is the usual charging Voltage.

Nonetheless I agree that masthead LEDs can and do fail quite frequently. This is because although the circuitry, in particular the LEDs, can take over-current in the forward direction for a surprisingly long time (eg 10,000 hours, which is > 1 year continuous operation), they are killed almost at once by reverse breakdown, which takes only a few tens of Volts for a few microseconds. A lightning strike within a mile or two will do this easily! So protection is a good idea. A diode across the LED is a good start, reverse biassed when the LED is forward biassed. But you still need to ensure that in the event of a very fast (think less than a nanosecond) edge, the protection circuit protects before the Voltage rises on the LED to a level which will cause breakdown. This requires some care about parasitic inductances and possibly the addition of some capacitance to slow edges.

It's possible that the extra regulated PSU achieves this level of protection, but if it does, it won't be the mere reduction of a Volt or two that does the trick; the added protection will be a side effect, and as good or better protection could be achieved with fewer and cheaper (and more reliable) components.

 

[elton]

A constant current supply is the proper way to drive LEDs. Provided it's designed correctly, it will regulate for higher voltages, and will deal with a degree of undervoltage equally well.