Adjustable constant flow source driving circuit for LED

Abstract

The invention discloses an adjustable constant flow source driving circuit for an LED (light-emitting diode). The driving circuit comprises an operation amplifier, a transistor and a single chip system, wherein the positive phase input end of the operation amplifier is connected with a reference voltage circuit, the grid electrode of the transistor is coupled with the output end of the operation amplifier through a resistor R4, the LED is connected between the drain electrode of the transistor and the reference voltage circuit, the single chip system is connected with the positive phase input end of the operation amplifier, the source electrode of the transistor is connected with the negative phase input end of the operation amplifier to form a current-series negative feed-back system, a grounded voltage sampling resistor R6 is connected between the source electrode of the transistor and the negative phase input end of the operation amplifier, nodes A are formed between the source electrode of the transistor and a voltage sampling resistor R6, the single chip system is used for adjusting the control voltage of the positive phase input end of the operation amplifier according to the voltage signals acquired from the nodes A, and a grounded divider resistor R5 is connected between the resistor R4 and the grid electrode of the transistor. The driving circuit is controlled by the single chip system, thus current change can be steadily and continuously controlled when the voltage on the positive phase input end of the operation amplifier is adjusted.

Description

technical field [0001] The invention relates to an adjustable constant current source drive circuit for LEDs. Background technique [0002] In today's increasingly serious energy and environmental problems, LEDs with the characteristics of high efficiency, energy saving, environmental protection, and long life have gained people's attention. If LED lighting can replace the current low-efficiency and high-energy-consuming traditional lighting, it will undoubtedly alleviate The current increasingly urgent problems of energy shortage and environmental degradation play a decisive role. [0003] The volt-ampere characteristics of LEDs are the same as those of ordinary diodes. Small fluctuations in forward voltage will lead to sharp changes in forward current. The magnitude of LED forward current will change with ambient temperature. When the environment reaches a certain temperature, The allowable forward current of the LED will decrease sharply. In this case, if the large curre...

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Problems solved by technology

[0003] The volt-ampere characteristics of LEDs are the same as those of ordinary diodes. Small fluctuations in forward voltage will lead to sharp changes in forward current. The magnitude of LED forward current will change with ambient temperature. When the environment reaches a certain temperature, The allowable forward current of the LED will decrease sharply. In this case, if the large current is still passed, it will easily cause the LED to age and shorten the service life. In order to solve this problem, it is necessary to provide a constant current LED with an adjustable constant current value. Drive circuit

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