In this regard, it is recommended to limit the starting current using an additional resistor connected in series with the filaments of the halogen lamps. After the lamp is switched on, this resistance is short-circuited using a voltage relay installed parallel to the lamp.
The disadvantage of such devices is the need to use one or two electromagnetic relays, parts that are not reliable enough, especially in a car that experiences vibration. In addition, at the moment of switching on, there is still a sudden increase in current, although to a smaller value than with conventional lamp switching circuits.
Specialists have developed a contactless device that does not require the use of a relay and ensures a smooth increase in current in the lamp. The device consists of an additional resistor R1, two diodes VD1 and VD2 and an electrolytic capacitor C.
When the low beam filament is switched on, a positive potential is applied to terminal 1. In this case, the diode VD1 connects the capacitor C in parallel to the lamp filament, and the resistor R1 in series with it.
When the high beam filament is switched on, positive potential is applied to terminal 2, and capacitor C is connected in parallel to the high beam filament through diode VD2.
With this connection scheme, the voltage on lamps EL1 and EL2 increases smoothly.
The resistance of cold filaments of conventional automobile low and high beam lamps is approximately an order of magnitude lower than their resistance in the heated state. The heating time constant of the lamp filament is 0.0014–0.003 s.
To avoid an unacceptably high current during the lamp switching on process, it is necessary that the rate of increase of the lamp filament resistance be greater than the rate of increase of the voltage. This is achieved by installing electrolytic capacitors with a capacity of 4000-6000 μF, a nominal voltage of 25 V.
[Original material on the website: Mercedesman.ru]
If you use these tips, then along with increasing the service life of the lamps, the life of the battery will also be extended due to the reduction of the starting current and the smoothness of its increase.