An Adaptive LED Driving Circuit

Abstract

The invention discloses an adaptive LED driving circuit, which comprises: a fluctuating DC power supply, used to generate a DC voltage signal with periodic voltage changes; a current control circuit, used to change the series and parallel relationship between LED strings, so as to Adaptive to the periodic change of the DC signal; a current limiting or constant current circuit, used to limit or constant current the DC voltage signal, and drive the current control circuit to run; the fluctuating DC power supply, the current control circuit and the current limiting Or the constant current circuit is connected in series to form a closed loop; the current control circuit includes at least two current control subunits, and each current control subunit includes a first normally closed switch, a second normally closed switch, a fourth normally closed switch, a a diode and a second diode. The LED strings of the present invention can be connected in parallel or in series through a normally closed switch according to the input voltage level and the magnitude of the circuit current, thereby changing the total voltage of the LED strings and automatically adapting to changes in the input voltage.

Description

technical field [0001] The invention relates to LED lighting tools, in particular to an adaptive LED drive circuit which changes the series-parallel structure of its own LED strings as the input voltage changes. Background technique [0002] At present, LED lighting is very popular. LED is a constant voltage device, and its current and voltage characteristics are similar to diodes. Therefore, it is necessary to limit the LED to work within the allowable current range to avoid LED damage due to overcurrent. Generally, LED lamps are driven by a DC power supply. The mains power is converted into DC power by a high-frequency switching power supply to drive the LED to emit light. The constant current circuit makes the LED work within a safe current range. The problem with this method is that the circuit is complex, there are many components, the cost is high, and the reliability is reduced; the second is that the volume becomes larger after the driving power is added, the design ...

AI Technical Summary

Problems solved by technology

The problem with this method is that the circuit is complex, there are many components, the cost is high, and the reliability is reduced; the second is that the volume becomes larger after the driving power is added, the design of the lamp body must consider the space for the driving power, and the design flexibility of the whole lamp is reduced; The third is that the circuit works in a high-frequency state of 30KHz-150KHz, which will inevitably produce electromagnetic interference; the fourth is that the driving power needs to use electrolytic capacitors, and electrolytic capacitors have a life limit, generally about 8000 hours, relatively speaking, the LED life can reach 30000 Hours or more, so the life of the driving power limits the life of the LED lamp, and many LED lamp failures are caused by power failures

[0003] In order to solve these problems, there are some AC drive LED circuits that do not need a driving power supply. Since the voltage of a single LED is generally about 3.2V, which is far lower than the mains voltage, multiple LEDs are used in series to make the total voltage close to the mains. Voltage, and then through the current limiting circuit (current limiting resistor) to make the LED work, such as figure 1 shown, when the input voltage is less than V d (It is the sum of the voltages of multiple LEDs in series) when the LED is in the cut-off state and does not emit light, the LED turns on and emits light when it is greater than Vd. The disadvantages of this circuit are that the LED conduction angle is small, the stroboscopic is more obvious, and the electrical efficiency is low. Very high harmonic distortion

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