1. Classification by drive method
(1) Constant current type
The current output by the constant current drive circuit is constant, and the output DC voltage varies within a certain range with the size of the load resistance. The load resistance is small, the output voltage is low, and the larger the load resistance, the output voltage is The higher; the constant current circuit is not afraid of the short circuit of the load, but it is strictly prohibited to open the load completely; the constant current drive circuit is ideal for driving LEDs, but the price is relatively high; it should be noted that the maximum withstand current and voltage value used, which limits The number of LEDs used.
(2) Regulated type
When the parameters in the voltage stabilizing circuit are determined, the output voltage is fixed, but the output current changes with the increase and decrease of the load; the voltage stabilizing circuit is not afraid of the load open circuit, but it is strictly forbidden to completely short-circuit the load; driven by voltage stabilization The circuit drives the LEDs, and each string needs to be added with a suitable resistance to make each string of LED display brightness average; the brightness will be affected by the voltage change from the rectification.
2. Characteristics of LED drive power
(1) 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.
(2) High power factor
Power factor is the load requirement of the power grid. There are no mandatory indicators for household appliances under 70 watts. Although the power factor of a single power consumer with low power has a little impact on the power grid, 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 the 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.
(3) Drive method
Now there are two kinds of traffic: one is a constant voltage source for multiple constant current sources, and 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 driving method of direct constant current power supply, LEDs run in series or parallel. 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 mode will be better in terms of cost and performance. Perhaps it is the mainstream direction in the future.
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