LED driver design in Lighting

The arrangement of LED and led source standard decide the basic driver requirement ,the main function of led driver is limiting the led current under a certain working condition ,
However ,no matter how the input or output voltage change ,the most common thing we use is that adopting transformer to Electrical isolation .The paper discuss the factors should be considered for LED lighting design.

LED drivers are confronted with many challenges , like forward voltage changes with the temperature and current ,but there is a difference between different unit ,batch ,suppliers’LED. Otherwise , color dot of LED will drift with the change of current and temperature.

In addition ,we usually use many  LED in applications which involves the Led arrangement . single series led is the first choice arrangement since no matter how the forward voltage changes ,how the input voltage drifts ,this arrangement can offer excellent current matching performance.
Of course users can adopt parallel connection, tandem-parallel combination and cross linking or other arrangement to “mutual matching” led forward voltage application and obtain other advantages. For example ,when using cross linking ,if one of the led is open caused by malfunction ,there is only one led driver’s current becomes double to reduce the impact to the circuitry  to the greatest extent .
The arrangement of LED and led source standard decide the basic driver requirement ,the main function of led driver is limiting the led current under a certain working condition ,no matter how input voltage and output voltage change .

The basic operating circuit diagram of LED driver shows as figure 2, the so-called “isolation” means there is no physical electrical connection between AC line voltage and LED (Input and output ) .The most commonly used is adopting transformer to isolate electric , but  “non-isolation” means it doesn’t use high-frequency transformer to make the electric apart.

It should be noted that in LED lighting design ,AC-DC power conversion and  constant-current can using different configurations .

1) Integral configuration , it means both two mix together in lighting fixture .its superiority includes optimization efficiency and easy install ect.

2) Distributed configuration ,it means both exist alone .it simplified safety concerns and increase the flexibility .

LED Driver can use constant-voltage (CV) output work according to different application ,which input a certain current under clamp bits of voltage .and led driver can also use constant-current(CC) output work ,the design can strictly limit current ,and it also can adopt constant-current constant-voltage (CCCV) output work ,which offer constant output power ,so the forward voltage of laden LED determine the current .

On the whole , LED Lighting design should consider the following factors:

Output power: involving LED forward voltage range ,current and led arrangement ect.

Power supply: AC-DC power supply ,DC-DC power supply ,directly using AC power driver.

Function request : dimmer requirements , dimmer mode(simulate digital or multi-stage) ,Lighting control

Requirement : energy efficiency ,power factor ,size ,cost ,fault treatment (protection features) ,comply with standards and reliability ect.

More consideration: mechanical connection ,install ,fix/replacement ,lift time ,logistics ect.