Do you really understand the constant current and constant voltage of the LED power supply?

 

Constant current, that is, the output current is constant, but the power supply current is not fixed, the nominal voltage is only the safe upper limit; constant voltage, that is, the output voltage is constant, but the output current is not fixed, the nominal current is only the maximum Upper limit. Most electrical power adapters, such as mobile phones and notebooks, are constant voltage power supplies. Constant current power supply is mainly used in chargers, LED drivers, power supplies for electrolytic reactions, etc.
Second, the difference between led constant voltage power supply and constant current power supply

Under the allowable load condition of the constant voltage source power supply, the output voltage is constant and does not change with the load change. It is usually applied to small power LED modules and small power LED strips. The constant voltage source is the regulated power supply that we often say, and it can keep the voltage unchanged under the condition that the load (output current) changes.
Third, how to change the current of the constant voltage power supply

 

If you want to change the current of the constant voltage power supply, you can use the sampling resistor to control the MOS tube after the operation of the op amp. By changing the driving voltage to change the internal resistance of the MOS, design a constant current source. If it is only current limiting, it will exceed the direct shutdown.

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Fourth, the constant voltage power supply problem for LED lights

Due to the nonlinearity of the characteristic curve of the LED, a small voltage change causes a large current change, so it is generally a constant current drive, which also ensures the stability of the operating voltage. LEDs mainly require constant current and do not have to be constant voltage. The switching power supply of the common single-chip solution in the market is not suitable for direct use in LEDs, and it is better to add a constant current part. Whether the LED is connected in series or in parallel, the better driving method is: isolated power + constant current circuit

Fifth, an example of constant current constant voltage power supply

 

A constant current constant voltage power supply, by adjusting the voltage adjustment and current adjustment of the panel, the power supply no-load output voltage is set at 100V, the constant current value is adjusted at 1A, and the power supply automatically changes the power supply as the load resistance changes. Through the above introduction, we can know that when the output current is less than 1A, the power supply is in constant voltage operation, and strive to keep the output voltage at 100V, and the output current changes with the magnitude of the load, and when the current When the value tends to be greater than 1A, the power supply is in a constant current mode, and the output current is kept at 1A, and the output voltage varies with the magnitude of the load. When the output voltage is 100V, the load resistance is negotiated to 100 ohms, and the output current is negotiated at 1A, which is the turning point of the two working states of the power supply. The power supply can be said to be a constant voltage state or a constant current state.