LED lighting brightness stability and energy saving

Since 2010, advanced countries such as Europe, the United States, and Japan have successively begun the implementation of the ban on incandescent light bulbs, which is based on light sources that limit low luminous efficiency. Incandescent light bulbs are disabled, replaced by light sources including light bulbs, cold cathode tubes, LEDs, etc., and LED light sources will be the best choice.

The working principle and characteristic of LED light source The light emitting diode is the diode that the semiconductor material synthesizes, is made up of PN interface, when the forward voltage is applied, the electron and the hole combine to release the energy in the form of photon, therefore has the luminescent characteristic. The light source is generated within millimeters of the PN interface. The wavelength of the emitted light varies depending on the characteristics of the material. There are red, yellow, green, and blue light emitting diodes. The brightness of light emitting diodes can be adjusted by the operating voltage (current). In a large range of operating current, the brightness of the light-emitting diode increases with the increase of the current.

LED lighting brightness stability LED brightness varies with the size of the current, and the light-emitting diode manufactured by the voltage and current curves are slightly different, so the brightness of LED lighting often with the power supply voltage changes and can not be stable. In order to maintain the brightness and stability, a constant current LED driver is required. The constant current driver enables the light emitting diode to operate in a fixed current mode and thus has high brightness stability. The constant current driver also allows the LED to operate at a constant current for a long period of time.

The T6316 is a constant current driver. It is a constant current LED driver with 4 channels. The output current can be determined according to the external resistor. T6316 has ±6% precision current and channel ± 3% matching accuracy, can be used for street lamps, lamps and other lighting equipment. For energy-saving considerations, the system design must consider the constant current driver's voltage across 0.5V~2V. Since the light emitting diodes work under constant current for a long time, their cross voltage drops slightly, and this change must also be considered in the system design.

LED lighting energy saving considerations The advantages of LED lighting are energy saving and safety, but due to constant current work considerations, energy consumption also increases relatively, so the lighting system design aims at low energy consumption. As mentioned earlier, the voltage drop of the constant current driver is within 2V, that is, the design with low energy consumption is considered. If the power supply voltage of the system and the voltage drop of the series LED exceed 2V, the voltage converter must be considered to achieve the low energy consumption target. , but still maintain a constant current mode of operation. Low-power voltage converters operate in a switching mode, and rely on a feedback circuit to control the switching period to achieve a stable output voltage. However, in order to maintain the constant current operating state of the light emitting diode, the feedback circuit controls the converter switching period based on the output current.

The T6322 is a step-down constant-current LED driver whose current is determined by the external resistor and can support up to 1.5A output current, providing ±5% accuracy current and high power efficiency (low power consumption) and high power line adjustment capability.

In the LED lighting products currently flooded with the market, their power input systems are of two types: a front-end AC power input system plus a back-end constant current control module. Such products include refrigerated cabinet light strips, indoor fixtures, and street lamps. Table lamp, MR16, AR111 and so on. The other type is AC power direct input system integrated AC/DC converter and constant current circuit. Such products include bulb type LED lamps such as E27 and GU10, PAR lamps, T5 and T8 LED lamps.

In addition to selecting the constant voltage power supply with better front-end efficiency, the power supply module controlled by the back-end constant power supply adopts a more efficient power supply design based on its product characteristics. Its advantage lies in the front end AC/DC power supply, such as switching power supply, DC adapter and other constant voltage power supply, which can be highly selective and have many safety certification schemes, thereby reducing the design threshold.

The second type of power supply design incorporates an AC/DC circuit and a constant current circuit, so it can meet the design requirements of a smaller space. However, there are some difficulties in designing from the considerations of power factor, power supply efficiency, and safety regulations. Therefore, in today's market, such products rarely achieve high luminous efficiency and high power factor (>0.9).

This article summarizes LED lighting products to achieve high luminous efficiency, and then become the next generation of major light sources, the first consideration is the power module design, select the correct design architecture for different lighting products. In addition, power supply control ICs must also improve power supply efficiency, power factor, and reliability in order to develop products suitable for LED lighting needs.