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Categories of LED Drive Circuits

1) By LED drive mode, LED drive circuits can be classified into two types:

(1) Constant current LED Drive Circuit

A. Under constant current circuit , electrical current output remains stable and constant while voltage output varies with load resistance values. Higher load resistance is, so is voltage input; and vice verse.

B. Constant current LED drive circuit can still work under short-cut circuit circumstance while no open circuit is allowed.

C. As for LED, constant current circuit is rather plausible although the price is undesirable.

D. Please pay attention to the max on-load current and voltage, for which primarily limits the use of LEDs quantity.

(2) Voltage Regulatory LED Drive Circuits

A. For voltage regulatory circuit, the voltage input remains stable as the current changes with load resistance value.

B. No short cut circuit is allowed for voltage regulatory LED driver circuit.

C. Working in voltage regulatory circuit, proper resistance values can only keep LED light uniformly.

D. LED brightness will varies with voltage input

2) By circuit structures, LED drive circuits can be divided into RC Buck drive circuit, Rs Buck drive circuit, transformer buck drive circuit, electronic transformer buck drive circuit, RCC buck drive circuit, PWM controlled buck drive circuit.

(1) RC Buck drive circuit

In RC buck drive circuit, transient current passing through LEDs is great under high frequency charge and discharge, which eventually causes damage to LED chip. Moreover RC buck drive circuit is much more affected by grid voltage fluctuation with low power efficiency and reliability.

(2) Rs buck LED drive circuit

In Rs buck LED drive circuit, voltage buck-down is realized by buck resistors, thus leading to a large amount of energy loss and low power efficiency and dependability.

(3)Transformer or electronic transformer buck LED drive circuit

Transformer or electronic transformer buck LED drive circuit is designed with power supply featured by small volume, lightly-overweight, low power efficiency of 45%-60% and low dependability.

RCC buck drive circuit has the advantage of wide range voltage, relatively high power efficiency reaching up to 70%-80%, and is widely applied in lots of electric circuits. However, the biggest weakness of RCC buck drive circuit is that oscillation frequency is discrete and switching frequency is hard to control. What is worse, RCC buck drive circuit bears much higher load voltage ripple factor with poor adaptability to overloading or under-loading.

(6) PWM buck drive circuit is one of the most reliable electric circuit adopted today. By means of PWM technique, digital signal processor can take charge of analog circuit and finally acquire regulatory voltage or constant current. PWM buck drive circuit is characterized by high power efficiency up to 80%-90%, regulatory voltage input or constant current drive with high reliability.

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