Car driving circuit of LED lighting

Car driving circuit of LED lighting

LED lighting to belong to current control type semiconductor devices, figure 1 is LED the volt-ampere characteristics of curve. The figure 1, the curve that is steep, in general is guide LED almost no current flow through before; When the forward voltage, current voltage over open has accelerated, and shine brightness L and positive current IF approximate proportional to: L = KIF, among them, the ratio K as can be through the control of LED to control the light IF brightness. Therefore, in order to ensure the consistency of its brightness, usually by constant current source driver circuit.


Car battery voltage range for 9 V ~ 16 V, usually for 12 V, but when the automobile cold start battery voltage when can drop down to four V, and when the battery by generator power supply when directly defect, the voltage can be up to 36 V high pressure. So, for LED lamps and lanterns is concerned, vehicle to reliably constant current drive LED string, driving controller must have precise voltage and current regulation, protection circuit and the dimming function. Therefore, design a kind of good performance and voltage and constant current output driver circuit is necessary.

At present commonly used vehicle LED drive two methods control positive current.

(1) using LED curve to determine the V-I have the desired positive current need that voltage applied to LED. Its defect is: the forward voltage LED any of the changes will lead to the change of LED current, one of the ZhenLiu resistance of the pressure drop and power consumption will waste power and reduce battery life.

(2) use of constant current source to drive LED. Because this method will need to LED parallel in a circuit, and drive a parallel LED in every LED string to place a ZhenLiu resistance, it will lead to low efficiency and electricity with loss. Therefore, the two methods are not fully reflect the superiority of the LED due. In order to overcome the shortcomings of the existing vehicle LED drive, appeared the array of efficient vehicle LED intelligent control method. This method USES half bridge type DC-DC transform technique, and the wave rectifier technology, photoelectric coupling technique, etc, to ensure that the power circuit of the work efficiency; Put forward based on embedded system of intelligent control scheme, the scheme adopts the steady flow control and intelligent PWM control, and have light load open/short circuit protection and through pressure protection function. Figure 2 for LED array intelligent drive experiment circuit. As shown in figure 2 shows, CPU output of two way down the relative says completely PWM signal of A and B, respectively in switching device role, and make them take turns conduction; Through the high frequency transformer T will energy coupled to the subprime, then through fast recovery rectifiers D1, D2 for the whole wave rectifier, in order to the array of drive LED. Driving circuit of photoelectric LED array, accomplish the coupler drive current monitoring LED array, and feedback to the CPU, form a kind of intelligent current negative closed-loop control system to ensure the stability of the driving current reliability.


Car driving circuit of integration and LED the level of intelligence and more and more high. Similar PMU (power management unit) of the chip and the package will gradually replace the miniaturization of DuoGe single function circuit combinations of methods, in order to adapt to the board level is very limited space the application. At the same time, because of SCM, DSP chip embedded control and the development of technology, but through the software technology to realize the automation of the vehicle lighting system, so that the constant current drive LED accuracy and brightness of the automatic adjustment will be more accurate. Intelligent control has become a new generation of car drive design idea. LED

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