LED drive power to choose why choose constant current power supply?
Abstract：LED is a light emitting diode, its characteristic curve and the general diode is fundamentally the same, when the applied voltage reaches the diode on-voltage, the slight change of the applied voltage can cause the drastic change of the diode current. LED constant current drive power supply selection is to ensure that the current in the LED is unchanged, no matter how the voltage changes, the current flowing through the LED is unchanged, to ensure the life of the LED and light decay.
LED is a light emitting diode, its characteristic curve and the general diode is fundamentally the same, when the applied voltage reaches the diode on-voltage, the slight change of the applied voltage can cause the drastic change of the diode current. LED constant current drive power supply selection is to ensure that the current in the LED is unchanged, no matter how the voltage changes, the current flowing through the LED is unchanged, to ensure the life of the LED and light decay.
Suppose that a constant voltage source with an output of 12V is selected, and a 16 ohm resistor is connected in series to supply power to three 0.5W 5630 lamp beads. The lamp bead voltage is calculated according to 3.3V, the current flowing through the lamp bead Io=(12-3*3.3)/16=0.131A, and the power of A single lamp bead is P=0.131*3.3=0.4323W. As the temperature of the lamp bead increases, the voltage of the single lamp bead drops to 3V. At this time, the current Io=(12-3*3)/16=0.187A, the current increases 56mA., and the power becomes P=0.187*3=0.561W, exceeding the power consumption of the lamp bead. For a long time, it has a great impact on the life and light decay of LED lamp beads.
Therefore, the key to affect the life of the LED is the temperature, when the LED temperature increases, its junction resistance is reduced, that is, the current voltage is reduced. Under the same voltage, the increase in temperature will cause the LED current to increase, and the increase in current will further improve the temperature, so that the vicious cycle will burn the LED. Moreover, the light decay of the LED is also related to temperature, and the time decay of the temperature increases, showing a bright but not bright appearance.
There are two reasons for the increase in temperature: first, the quality problem, the poor thermal conductivity in the LED package, the temperature in the LED tube core can not be transferred to the appearance (internal heat and external cool), even if the heat dissipation device is added, the internal heat can not be emitted in full, and then some low-grade products do not add heat dissipation devices; The second is the temperature rise caused by the power supply, when the LED is switched on, because of its nonlinear, small change in the power supply will cause the LED current to change sharply, and then cause the temperature to increase.
Suppose that a constant voltage source with an output of 12V is selected, and a 16 ohm resistor is connected in series to supply power to three 0.5W 5630 lamp beads. The lamp bead voltage is calculated according to 3.3V, the current flowing through the lamp bead Io=(12-3*3.3)/16=0.131A, and the power of A single lamp bead is P=0.131*3.3=0.4323W. As the temperature of the lamp bead increases, the voltage of the single lamp bead drops to 3V. At this time, the current Io=(12-3*3)/16=0.187A, the current increases 56mA., and the power becomes P=0.187*3=0.561W, exceeding the power consumption of the lamp bead. For a long time, it has a great impact on the life and light decay of LED lamp beads.
Therefore, the key to affect the life of the LED is the temperature, when the LED temperature increases, its junction resistance is reduced, that is, the current voltage is reduced. Under the same voltage, the increase in temperature will cause the LED current to increase, and the increase in current will further improve the temperature, so that the vicious cycle will burn the LED. Moreover, the light decay of the LED is also related to temperature, and the time decay of the temperature increases, showing a bright but not bright appearance.
There are two reasons for the increase in temperature: first, the quality problem, the poor thermal conductivity in the LED package, the temperature in the LED tube core can not be transferred to the appearance (internal heat and external cool), even if the heat dissipation device is added, the internal heat can not be emitted in full, and then some low-grade products do not add heat dissipation devices; The second is the temperature rise caused by the power supply, when the LED is switched on, because of its nonlinear, small change in the power supply will cause the LED current to change sharply, and then cause the temperature to increase.
