LED Driver suitable for DALI Dimming Module
LED Driver
of Constant Voltage
and Constant Current
method and Suitable for Dimming Control method
1. Overview of LED Driver suitable for dimming control
…Recently, LED lighting is installed in all buildings, and lighting dimming control is performed for efficient lighting management and energy saving. The representative dimming control method is DALI Dimming Module using the DALI protocol and wireless dimming control method are adopted. However, sometimes it is not reviewed at the design stage, and the LED luminaire equipped with a constant current type of SMPS, which is impossible to control dimming in the field, is installed. Dimming control applied in the original design drawing is not realized. To solve this problem, LED lighting equipped with SMPS of constant voltage or constant current voltage (CCCV) type capable of dimming control must be supplied. We introduce the basic LED lighting principle and dimming control data for constant voltage and constant current method.
2. What is LED? LED(Light Emitting Diode) : A semiconductor device that emits light when a voltage is applied in
a forward direction
Luminescence is at the PN junction, since the energy of the former is directly converted to light energy, it does not require heat or energy macroscopically. Electrons and holes injected into the semiconductor from the electrode flow through another energy band (conductor band or atomic band) and recombine beyond the band near the PN junction. When recombined, a significant amount of energy is emitted as photons or light, in the band gap.The intensity of light is determined with respect to the amount of current, and if the maximum rated current is exceeded, the device will be damages, and if it is shortened or severe, it cannot be used.
When driving with a constant voltage, the current also changes due to the difference in the device or the change in the forward drop voltage due to the device temperature.
A method of limiting direct current by connecting a resistance or constant current diode in series using a direct current power source that generates a constant voltage higher than the forward drop voltage of the light emitting diode is well performed.
3. LED luminaire
… luminaire composition : luminaire + LED Converter (LED Driver) + LED substrate…LED Converter(LED Driver or SMPS) : Switched Mode Power Supply
- As a device for supplying power to the LED chip installed in the LED luminaire, it is a device that receives AC input and converts it to DC that can drive the LED. It must supply power to the LED with a constant amount of DC voltage or current. The LED’s light-emitting diodes generate efficient light. In order to supply such a constant voltage and current, a constant voltage method and a constant current method of SMPS (LED Driver) are required.
…The lifespan of LED lamps depends on the electrolytic capacitor of the LED converter.
- When using a high specification domestic long life capacitor.
Use Environment 105°C ---> 10,000Hours , 95°C ---> 20,000 Hours, 85°C ---> 40,000Hours, 75°C ---> 80,000Hours
Each 10°C lower life can double.
…LED luminaire composition : luminaire + LED Converter (LED Driver) + LED substrate
…LED array and LD converter voltage current is determined according to the set : 10 series 4 parallel (ex: 3.7V * 10 = 37V, 10mA * 10 * 4 = 400mA)
4. LED Dimming(PWM control method)
PWM(Pulse Width Modulation) : Pulse width modulationIn the case of general LED luminaires, when dimming, if dimming is adjusted by PWM method (with pulse width) in a waveform of constant DC voltage, the amount of current is adjusted to reduce the output (voltage and illuminance) of the LED.
On the other hand, PWM control is to control the output by adjusting On and Off time. For example, if you turn it ON for 1ms and then turn it OFF for 1ms, on average, 12V x 1ms / 2ms = 6V, and the output is reduced. The On time for the entire cycle is called the Duty Ratio.
PWM control (limiting amount of current) method is a characteristic of maintaining constant current in SMPS of constant current method. This PWM type dimming control is not compatible. It is compatible with constant voltage or constant current constant voltage (CCCV: constant current method including constant voltage compensation circuit).
5. Comparison of constant voltage and constant current method according to dimming control
6. Conclusion
For dimming control of LED luminaires (DALI Dimming Module, Wireless Dimming Module, and 0-10V DC Dimming Module applies dimming control method), SMPS (LED Driver) in LED luminaire should consist of constant voltage method or constant current constant voltage method SMPS do.