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No switch mode led drivers for car indicators (direction flashers)

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Flyback

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Many cars still use incandescent indicator lamps, and relays to flash them on and off.
LEDs powered by switch mode led drivers are not wanted for car indicators because of the repetitive inrush that you get into the input filter capacitance of a switch mode led driver's input capacitor. -So its either relays flashing incandessant lamps, or relays flashing leds powered by linear led drivers (linear led drivers have very little input capacitance).

is this true that switch mode led drivers are no good for car indicators (turning indicators)
 
No, but lamp fault detection circuits expect a certain current to operate so a dummy load may be needed. Inrush is ok just like tungsten filaments.
 
There can also be strange problems with the current detection if the current taken by the indicators isn't steady. If the sampling happens to fall on the periods when the current is low, it will appear that the current is low, and the car may behave as though the indicator has blown. That can happen randomly, depending on how the sampling lines up with the current taken by the lamp.
 
There can also be strange problems with the current detection if the current taken by the indicators isn't steady
I think if there is any filtering on the input of the PWM circuit there should be constant current pulled from the battery. If the PWM is running in the 200khz to 2mhz range you can't have that all over the car.
inrush that you get into the input filter capacitance of a switch mode led driver's input capacitor.
The inrush from a light bulb is also high. I think adding a resistor to the filter should limit the inrush.
Some PWMs have a low voltage lockout. If the PWM stops working at 6 volts then the caps will need to charge from 6 to 12V. Less inrush!
 
Flyback

I think there is a much better choice. I have few indicators on my car that are at full brightness all the time and I don't like it. O/D off. traction, Track OFF come to mind. If the turn signals are full bright, I probably could care less.

So, for momentary indicators, it would not matter to me (turn signal, the ABS system engages traction), but O/D off annoys me at full bright.

I would propose the use of the DIM signal that would lower the brightness to a lower level. Headlight or park light signal would work.
 
I would think the cost:benefit is too high to make it desirable to put a switch-mode driver into a low-luminosity lamp that is only powered sometimes. A resistor makes more sense. The power/heat consumption are small anyway. For LED headlights/spotlights, an SMPS might be considered.

There doesn't have to be any inrush current in a switch-mode driver. A simple chopper converter using a series inductor won't have any inrush.
 
the charge up of capacitance for a SMPS can in fact emulate the current surge of a tungsten lamp but may not be enough to sustain the current needed for lamp failure false detect
 
There doesn't have to be any inrush current in a switch-mode driver. A simple chopper converter using a series inductor won't have any inrush.
..surely there will be inrush into the input capacitor.....all smps have an input capacitor
 
SMPS due to 1000x higher frequency will have much lower capacitance... again the load requirements are ill defined.
 
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