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Gtek International Co., Limited
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Application Q&A
3. What to consider when selecting LED power supply?
a. Lighting system designed to work in direct drive mode
The combined LED forward voltage range (upper and lower) must fall within LED power supply's constant current voltage range. For example, the LED Vf spec is 3.4~3.6V, when 6 are connected in series the combined Vf will be 20.4~21.6V. In this case, a 24V unit must be selected with constant current region of 18~24V.
For models with active PFC and system PF requirement is >0.9, load usage must be higher than as specified in the PFC spec. Relationship between PF and output load can be found in figure 1. The typical requirement is 75% load or above. Double check the spec for the model you are using to confirm actual requirement.
In areas with unstable AC voltage such as heavy industrial zone or generator supply utility,please select general usage LED series from table 1.
b. Lighting system designed to work with driver IC
The start up voltage of driver IC should be as close to the power supply rated voltage as possible.
Driver IC needs stable voltage to function properly. So, it is highly recommended to use general usage series from table 1.
For models with active PFC and system PF requirement is >0.9, load usage must be higher than as specified in the PFC spec. Relationship between PF and output load can be found in figure 1. The typical requirement is 75% load or above. Double check the spec for the model you are using to confirm actual requirement. When using driver IC, possible system EMI issue could arise. After completing lighting system design,EMI must be double checked. For suggestion on system EMI problem solving,refer to question 11.
Figure 1: PF versus output load
a. Lighting system designed to work in direct drive mode
The combined LED forward voltage range (upper and lower) must fall within LED power supply's constant current voltage range. For example, the LED Vf spec is 3.4~3.6V, when 6 are connected in series the combined Vf will be 20.4~21.6V. In this case, a 24V unit must be selected with constant current region of 18~24V.
For models with active PFC and system PF requirement is >0.9, load usage must be higher than as specified in the PFC spec. Relationship between PF and output load can be found in figure 1. The typical requirement is 75% load or above. Double check the spec for the model you are using to confirm actual requirement.
In areas with unstable AC voltage such as heavy industrial zone or generator supply utility,please select general usage LED series from table 1.
b. Lighting system designed to work with driver IC
The start up voltage of driver IC should be as close to the power supply rated voltage as possible.
Driver IC needs stable voltage to function properly. So, it is highly recommended to use general usage series from table 1.
For models with active PFC and system PF requirement is >0.9, load usage must be higher than as specified in the PFC spec. Relationship between PF and output load can be found in figure 1. The typical requirement is 75% load or above. Double check the spec for the model you are using to confirm actual requirement. When using driver IC, possible system EMI issue could arise. After completing lighting system design,EMI must be double checked. For suggestion on system EMI problem solving,refer to question 11.
Figure 1: PF versus output load
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