Analysis of LED lighting front cutting phase control dimming mode

Introduction: LED light-emitting principle is different from the traditional lighting is on the P-N junction, with the power of the LED light source, because of the use of the chip, the voltage and current parameters are different, so the internal wiring circuit structure and distribution are different, LED light source of various manufacturers on the optical drive requirements are not the same. Therefore, the control system and the light source electrical appliances have also become a common problem in the industry, while the diversification of LED control system is also a higher challenge. If the control system and lighting equipment is not complete, may cause the lights to go out or flashing, and may cause damage to the LED drive circuit and light source.

There are five types of LED lighting control in the market:

1, the cutting edge (FPC), SCR dimming

2, after the cutting edge (RPC) MOS dimming

3, 1-10VDC

4, DALI (digital addressable lighting interface)

5, DMX512 (or DMX)

Cutting edge control

The front dimming is the use of SCR circuit, from the AC phase 0, the input voltage chopping, until the thyristor conduction, the voltage input. The principle is to adjust the conduction angle of each half wave to change the sine wave, so as to change the effective value of AC current. With the advantages of high precision, high efficiency, small size, light weight, easy to control and so on, the front light modulator is dominant in the market.

Advanced phase control dimmer using thyristor as switching devices, also known as the advantages of controllable silicon dimmer FPC dimmer in the LED lighting lamp is dimming: low cost, compatible with the existing line, without re wiring. The disadvantage is that the dimming performance of FPC is poor, and the dimming range is usually reduced, and it will cause the minimum required load to exceed the rated power of a single or a small number of LED lamps. Because the thyristor half controlled switch properties, only open the current function, but not completely turn off current, even to the lowest level still has a weak current through LED, micro current luminous characteristics, makes the use of SCR dimmer exists after turning off the LED still exist weak luminescence phenomenon, has become the problem of free wiring LED dimming mode.

Figure: the cutting edge of the front wiring principle and the cutting edge to PWM