How to Adjust the Light of High Power led Beads

With the continuous improvement of LED brightness, from the initial level of less than 20 1m/W to the current level of 130 1m/W, the demand for dimming LED lamps is increasingly urgent. At present, there are constant-voltage LED driving power supplies (such as output voltage 12V or MV), which can be used for constant-voltage LED lamps, generally low-power LED lamps. You can use resistance to limit the current; There is also a constant-current LED driving power supply, which is generally used to drive constant-current high-power LED lamps. Pulse modulation (PWM) dimming technology can be directly used for constant voltage LED lamps. However, for constant-current LED lamps, if PWM dimming technology is directly used, the load adjustment rate of LED driving power supply can not meet the requirements of PWM control frequency, which leads to the inability to modulate the current with low duty ratio during dimming, and the average value of output current can not be reduced, resulting in high peak current. This will cause irreversible damage to the LED. At present, this dimming is mostly done by post-DC/DC, and generally DC/DC will have a dimming port. This scheme has the following disadvantages: First, it has high cost but low reliability. Second, it will adversely affect the electromagnetic compatibility (EMC) of the system. In order to solve the EMC problem, additional EMC filter lines need to be added.

The technical problem to be solved by the utility model is to provide a dimming circuit for high-power LED lamps in view of the above-mentioned prior art, which can solve the dimming problem of high-power LED lamps and solve the problems of reliability and electromagnetic compatibility. The technical scheme adopted by the utility model to solve the above technical problems is as follows: a high-power LED lamp dimming circuit is used for performing pulse modulation dimming on an LED light emitting circuit, and the LED light emitting circuit comprises a plurality of LED lamps connected in series, triodes and feedback resistors, and the anode of the first LED lamp among the plurality of LED lamps connected in series is connected with the anode of an external constant current power supply. The cathode of the last LED lamp among a plurality of LED lamps connected in series is connected with the collector of a triode, the emitter of the triode is connected with the first end of a feedback resistor, and the second end of the feedback resistor is connected with the cathode of an external constant current power supply. The base of the triode is also connected with the output pin of the constant current controller, and the first end of the feedback resistor is connected with the feedback input pin of the constant current controller. Compared with the prior art, the constant-current controller and the linear adjusting tube are added in the circuit, and the output end of the constant-current controller is used as a feedback reference source to adjust the VCE voltage of the triode in the LED light-emitting circuit, thus ensuring the voltage on the feedback resistor to be constant, and further ensuring that the current flowing through the LED does not exceed the output end of the constant-current controller divided by the resistance value of the feedback resistor. At this time, the dimming function of LED can be completed by adding the pulse modulation signal to the linear adjustment tube. This scheme can solve the shortcoming that the constant current drive power supply can not perform PWM dimming.

Fig. 1 is the circuit diagram of the dimming circuit of the high-power LED lamp in the embodiment of the utility model.

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The utility model will be further described in detail with the embodiment of the attached drawings. As shown in figure 1, the dimming circuit of high-power LED lamp includes a constant current controller of model AL8400, a linear adjusting tube Q2 and a resistor R 1. The base of the linear regulating tube Q2 is connected to the external pulse width modulation signal output terminal PWM, and the collector of the linear regulating tube Q2 is connected to the output pin of the constant current controller M; The LED lighting circuit comprises a plurality of LED lamps, a triode Ql and a feedback resistor R2 connected in series, wherein the anode of the first LED lamp Dl in the plurality of LED lamps is connected with the anode of an external constant-current power supply, the cathode of the last LED lamp Dn in the plurality of LED lamps is connected with the collector of the triode Ql, the emitter of the triode Q 1 is connected with the first end of the feedback resistor R2, and the second end of the feedback resistor R2 is connected with the cathode of the external constant-current power supply; The base of transistor Q 1 is also connected to the OUTput pin out of constant current controller M, the first end of feedback resistor R2 is connected to the feedback input pin FB of constant current controller W, the first end of resistor R 1 is connected to the anode of external constant current power supply, and the second end of resistor R 1 is connected to the output pin out of constant current controller M. Capacitor C 1 and capacitor C2 are peripheral elements. In this embodiment, the linear adjustment transistor Q2 is also a triode. Taking the voltage of 0.2V output from the feedback pin of constant current controller M of model AL8400 as the feedback reference source, the VCE voltage of transistor Q 1 is adjusted with the output of AL8400 to ensure that the voltage on feedback resistor R2 is always 0. 2V to ensure that the maximum current flowing through the LED lamp does not exceed 0. 2V/R2。 At this time, the PWM signal is added to the linear adjustment tube Q2, and the dimming function of the LED lamps Dl-Dn can be completed.

Claim 1. The invention relates to a dimming circuit of a high-power LED lamp, which is used for performing pulse modulation dimming on an LED light-emitting circuit. The LED luminous circuit comprises a plurality of LED lamps connected in series, triode oil and a feedback resistor (R2), and the anode of the first LED lamp in the plurality of LED lamps connected in series is connected with the anode of an external constant current power supply. The cathode of the last LED lamp among a plurality of LED lamps connected in series is connected with the collector of triode oil, the emitter of triode oil is connected with the first end of feedback resistor (R2), and the second end of feedback resistor (analog) is connected with the cathode of external constant current power supply. The collector of the linear adjustment tube is connected with the output pin of the constant current controller (Ni), the base of the triode is also connected with the output pin of the constant current controller (Ni), and the first end of the feedback resistor (R2) is connected with the feedback input pin of the constant current controller (Ni).

The utility model relates to a dimming circuit of a high-power LED lamp, which is used for pulse modulation dimming of an LED light emitting circuit. The LED luminous circuit comprises a plurality of LED lamps, triodes and feedback resistors connected in series, wherein the anode of the first LED lamp in the plurality of LED lamps connected in series is connected with the anode of an external constant current power supply, the cathode of the last LED lamp is connected with the collector of the triode, and the emitter of the triode is connected with the first end of the feedback resistor. The second end of the feedback resistor is connected with the cathode of an external constant current power supply, and is characterized in that the LED dimming circuit comprises a constant current controller and a linear regulating tube, the base of the linear regulating tube is connected with the output end of an external pulse width modulation signal, the collector of the linear regulating tube is connected with the output pin of the constant current controller, the base of a triode is also connected with the output pin of the constant current controller, and the second end of the feedback resistor is connected with the feedback input pin of the constant current controller. Compared with the prior art, the utility model can solve the defect that the constant current driving power supply can not perform PWM dimming.