LED dimming device based on PWM

Abstract

The embodiment of the invention discloses an LED dimming device based on PWM. The device comprises an LED driving unit, a current detecting unit and a hysteresis control unit, wherein the LED driving unit is composed of an inductor L and a fly-wheel diode, and LEDs are controlled to be turned on or off through an MOS transistor. The current detecting unit comprises a sampling resistor connected to an LED lamp in series and a differential amplifier connected to the sampling resistor in parallel; the hysteresis control unit is composed of an amplifier and a not-and gate; the negative input end of the amplifier is connected with the output end of the differential amplifier, a set threshold voltage is input to the positive input end of the amplifier, the output end of the not-and gate is connected with a gate pole of the MOS transistor, and the input of the not-and gate is connected with the output end of the amplifier and a digital dimming signal. Due to the adoption of the LED dimming device, a current hysteresis control mode is used for solving the problem that peak current and average current are not consistent during current peak control, the subharmonic oscillation phenomenon with the duty ratio larger than 0.5 occurring during peak current control is avoided, and therefore a slope compensation circuit is not needed, and the circuit structure is relatively simple.

Description

technical field [0001] The invention relates to a dimming circuit, in particular to a PWM-based LED dimming device. Background technique [0002] LED lamps are becoming more and more popular. The luminous efficiency of LED lamps has surpassed the level of ordinary fluorescent lamps. It has the advantages of high luminous efficiency, long life, energy saving and environmental protection. However, the research on LEDs is changing rapidly. It is generally believed that constant current drive LED lamps are The best choice, the current control method has the mainstream peak current control, but it has the problem that the average current is inconsistent with the peak current. Contents of the invention [0003] The technical problem to be solved by the embodiments of the present invention is to provide a PWM-based LED dimming device. It can stably solve the shortcomings of peak current control. [0004] In order to solve the above technical problems, an embodiment of the pres...

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Problems solved by technology

[0002] LED lamps are becoming more and more popular. The luminous efficiency of LED lamps has surpassed the level of ordinary fluorescent lamps. It has the advantages of high luminous efficiency, long life, energy saving and environmental protection. However, the research on LEDs is changing with each passing day. It is generally believed that constant current drive LED lamps are The best choice, the current control method has the mainstream peak current control, but it has the problem that the average current is inconsistent with the peak current

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