Self-adaptive type LED driving circuit

Abstract

The invention discloses a self-adaptive type LED driving circuit. The self-adaptive type LED driving circuit comprises a fluctuation direct-current power source, a current control circuit and a current limiting or constant current circuit, wherein the fluctuation direct-current power source is used for generating direct-voltage signals with periodically-changed voltages, the current control circuit is used for changing the series-connection and parallel-connection relationship between LED strings to adapt to the periodical changes in the direct-voltage signals by themselves, and the current limiting or constant current circuit is used for carrying out current limiting on the direct-voltage signals or keeping the constant current of the direct-voltage signals to drive the current control circuit to run. The fluctuation direct-current power source, the current control circuit and the current limiting or constant current circuit are connected in series to form a closed loop. The current control circuit at least comprises two current control sub-units, each current control sub-unit comprises a first normally-closed switch, a second normally-closed switch, a fourth normally-closed switch, a first diode and a second diode. According to the self-adaptive type LED driving circuit, the LED strings can be connected in parallel or in series through the normally-closed switches according to the input voltage and the circuit current, the total voltage of the LED strings can be accordingly changed, and the LED strings can automatically adapt 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 As shown, when the input voltage is less than Vd (the sum of the voltages of multiple LEDs in series), the LED is in the off state and does not emit light, and when it is greater than Vd, the LED turns on and emits light. The disadvantage of this circuit is that the LED conduction angle is small and the frequency is small. The flicker is obvious, the electrical efficiency is low, and the harmonic distortion is very large

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