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High power LED drive control system faces four major challenges
Visit:3314 Date:2016-07-07

With high-power LED technology matures, high-power LED driver design is particularly important. Depending on the nature of high-power LED devices, if the drive current is too large or the temperature is too high, the LED elements beyond the tolerance range, it can easily cause damage to the LED devices. Hence the need for a constant current, constant temperature control, and a reliable, complete protection function LED drive system.

1, high-power LED drive control technology features

LED drive power in accordance with the rules of the electricity grid and demand characteristics in the design and selection of LED drive power is need to consider the following aspects:

(1) LED street lamp drive power should not be installed at a height so that maintenance work will cause inconvenience, but also the maintenance cost is large, and therefore need to select a high-performance drive power.

(2) high-power LED is energy-efficient products, drive power requirements and therefore also higher. LED luminous efficiency will increase as the LED temperature decreases, therefore extremely important for the internal cooling LED LED normal operation. High-performance power supply, the loss of power is small, the heat within the LED will be small, it delayed the lighting or monitor temperature. To reduce the LED light failure have a positive effect.

(3) current LED driver, there are two main ways, first, a plurality of constant current power supply constant voltage power supply, each LED constant current power supply will be individually memorized for each circuit, this approach is extremely flexible, such as a LED appears failure, does not affect the normal work of the other LED but its high cost. The other is a direct constant current power supply, LED in series or in parallel operation by way of its lower cost, but less flexibility. Multiple constant current power supply mode has a large advantage in terms of cost and performance, the focus of development.

(4) LED anti-surge capacity is poor, especially anti-reverse voltage capability. Some LED display or lights installed outdoors because lightning sensing and enable the network load, so the power system will be a variety of surge, bad influence on the LED. Therefore, the LED driving power supply needs to have the ability to inhibit invasion of surge, in order to ensure that the LED is not compromised.

(5) When the lamp for outdoor installation, the power structure should be moisture-proof, water-proof housing should wear.

(6) In addition to the regular power supply for protection, it is best to increase the LED temperature negative feedback to prevent LED temperature is too high and affect the stability of the light output.

2, high-power LED drive control system challenges

When precision constant current power supply design has reached a stable power output, stable power source is necessary for stable conditions in the stability of the power supply, the current output of the light source in the long hours of work in the case will fluctuate. In order to get a stable current, the LED light to enhance stability, by controlling the peripheral voltage constant current source, by adjusting the magnitude of the voltage to the output current. LED drive circuit design system control section focus on single-chip, combined with the keyboard and LED digital display, sampling the voltage from the A / D compared by feedback and input voltage, adjust them appropriately, then the D / A's analog voltage to the input voltage.

Combined with high-power LED in development at home and abroad, LED driving system mainly faces the following challenges:

Lifetime (1) of the driver circuit should be improved, in particular the life of key components such as a capacitor will have a direct impact on the life of the power supply.

(2) LED drive should be to a higher conversion efficiency goal, because no optical output power are in the form of heat distribution, the conversion efficiency is too low and will have a bad effect on the LED energy saving effect.

(3) efficiently dimming LED dimming through a larger proportion, while ensuring at low brightness and high brightness color characteristics constant.

(4) to reduce its cost, low-power applications in today's workplace, the proportion of constant current drive power cost has been occupied by nearly 35%, which is the cost of the light source, which prevents LED promotion in the market to some extent.

3. The method of high-power LED driver circuit connected

Although the high-power LED light efficiency is high, but the release of a single LED luminous flux is not, therefore usually several LED connections. A plurality of LED basic connection method in series, parallel, and serial and mixed three.

(1) series

Advantages of LED series is the same as the inflow branch of each LED current, the brightness of each LED light is also the same. As support on the road at any one LED fails, it will cause all LED support on the road are stopped working. If an LED short circuit, constant current mode under no influence on the circuit, but in the constant voltage drive, it will make other LED voltage increases, so the current will increase and may cause damage to the LED.

(2) in parallel

Parallel support on the road, each LED working voltage, in order to make the work of each LED current is the same, the same voltage requirements of each LED. However, due to the difference between LED element parameters and the voltage LED will increase as the temperature decreases, resulting in the current work are different. If the cooling performance is not good, it is very likely to exceed the rated current of the LED element is damaged, it usually is not used in parallel mode.

(3) serial baker

LED in parallel or in series LED circuit requires a higher current or voltage, it is possible to consider the hybrid connected to current or voltage required is reduced to an appropriate level. The method of mixing after the first series are connected in parallel and after the first two major series parallel connection, high reliability, and the LED light brightness is relatively uniform.

4, Conclusion

High power LED drive power for effective power conversion efficiency, has strict requirements for precision constant current, electromagnetic compatibility, battery life, etc., so the design phase of LED driving system should make use of digital control, in order to avoid regulator linearity problem so stable improve the accuracy of the state and get a stable current to ensure the normal operation of high-power LED.



 
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