LED driver types, Constant Current vs. Constant Voltage

First, let’s talk about what is the LED drive power? It can convert the power supply to a specific voltage and current to drive the LED voltage converter. Generally, the input of the LED drive power supply includes high-voltage power frequency AC (ie, commercial power), low-voltage DC, high-voltage DC, low-voltage high-frequency AC (Such as the output of an electronic transformer). The output of the LED drive power supply is mostly a constant current source that can change the voltage with the change of the LED forward voltage drop value.

The core components of LED power supply include switching controller, inductor, switching component (MOSfet), feedback resistor, input filter device, output filter device, etc. According to the requirements of different occasions, there must be input overvoltage protection circuit, input undervoltage protection circuit, LED open circuit protection, overcurrent protection and other circuits.

LED driver types, Classification by driving method

Constant Current LED Driver

Constant Voltage LED Driver

Constant voltage LED driver

Characteristics of LED drivers

(1) High reliability

Like the driving power of LED street lamp, it is installed at high altitude, which is not convenient for maintenance, and the cost of maintenance is also large.

(2) High efficiency

LED is an energy-saving product, and the efficiency of the driving power supply is higher. It is very important for the heat dissipation of the power supply installed in the lamp. The efficiency of the power supply is high, its power consumption is small, and the heat generated in the lamp is small, which reduces the temperature rise of the lamp. It is beneficial to delay the light decay of LED.

(3) High power factor

Power factor is the load requirement of the power grid. Generally, household appliances under 70 watts have no mandatory indicators. Although the power factor of a single consumer with low power is a little low, it has little effect on the power grid, but the amount of lighting used at night is large, and the similar loads are too concentrated, which will cause serious pollution to the power grid. For LED drive power of 30 watts to 40 watts, it is said that in the near future, there may be certain index requirements for power factors.

(4) Drive method

Now there are two kinds of traffic: one is a constant voltage source for multiple constant current sources, each constant current source separately supplies power to each LED. In this way, the combination is flexible, all the way LED failure, does not affect the work of other LEDs, but the cost will be slightly higher. The other is the direct constant current power supply, that is, “Zhongke Huibao” changed to the driving mode, LED series or parallel operation. Its advantage is that the cost is a bit lower, but the flexibility is poor, and it is necessary to solve the problem of a certain LED and not affect the operation of other LEDs. These two forms coexist for a period of time. The multi-channel constant current output power supply method will be better in terms of cost and performance. Perhaps it is the mainstream direction in the future.

(5) Surge protection

LED’s ability to resist surge is relatively poor, especially the ability to resist reverse voltage. It is also important to strengthen protection in this regard. Some LED lights are installed outdoors, such as LED street lights. Due to the induction of the grid load and the induction of lightning strikes, various surges will be invaded from the grid system, and some surges will cause damage to the LED. Therefore, the analysis of the “Zhongke Huibao” drive power supply should have some deficiencies in surge protection. As for the frequent replacement of power supplies and lamps, the LED drive power supply must have the ability to suppress the intrusion of the surge and protect the LED from damage.

(6) Protection function

In addition to the conventional protection function, it is best to increase the LED temperature negative feedback in the constant current output to prevent the LED temperature from being too high; to meet the safety regulations and electromagnetic compatibility requirements.

The advantages and disadvantages of the overall constant current and channel-by-channel constant current working methods

Compared with the overall constant current, the channel-by-channel constant current has more disadvantages and higher cost. But it can really protect the LED and extend the life of the LED, so the constant current is the future trend.