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application of nu501 in led fluorescent lamp power supply

NU501 is a linear constant current IC, the variety is 15-60mA, every 5mA is divided into a file, with a simple, versatile, high precision.

I. Product characteristics

Nu501 series is a simple constant current component, very easy to use in a variety of LED lighting products.It has excellent load and power supply regulation rate and minimum output current error, NU501 series LED current can be very stable, even in the Large area of ​​the light source, the power supply and load fluctuation range can make LED brightness uniform, and increase the LED life.

In addition to supporting a wide supply range, the NU501’s VDD pin can be used as an output enable (OE) function, can be used with digital PWM control circuit to achieve more accurate gray-scale current adjustment applications.

The NU501’s very small operating voltage can be used as a diode currentregulative diode (CRD) when VDD and VDD pins are shorted together. A string of LED, that can make the current constant.

In the case of high voltage power supplies and low LED load voltage applications, multiple NU501s can be used in series to distribute the excess voltage.This unique overvoltage sharing technique is well suited for applications over a wide range of supply voltages, Chip manufacturers do not have.

2. Application circuit design considerations

NU501 linear constant current components, the application should be considered when the power consumption and cooling problems. The higher the component current, the lower the output voltage drop of the NU501 to avoid high heat from the NU501. The method to reduce the output is as follows:

1, in the case of maintaining constant current, try to reduce the supply voltage.

2, in the case of maintaining constant current, try to increase the constant current series circuit in the number of LED.

3, in the case of constant current can be maintained in the constant current series circuit, coupled with the buck resistor to reduce the output voltage NU501.

4, the system power supply for more than 24v working environment, it is recommended in the VDD and VN pin parallel connection of a 0.1uF to 10uF capacitor to increase the current stability and reliability.


application of nu501 in led fluorescent lamp power supply


1. The role of RC buck in the figure is to reduce the pressure drop. Different number of LED series, calculate the capacitance of different capacity. For example: input 220V, 35-40LED series with 474 capacitors, 20-25 with 334 capacitors.

2. Eliminating the need for RC buck applications, in the input for the 220V applications, to be 80-90 small power LED in series to use. For LED, such as: 3528, straw hat, 110V applications in the number of input LED halved, 35-45 stars in series with the use of LED,

3. The lower the input and output voltage drop, the higher the efficiency, the voltage drop should take into account the MOS cooling capacity.

4. Available models of the NU501 series are, 1A15, 1A18, 1A20, 1A25. Constant current accuracy,

5.1A18 for the measured current output between 18.4-18.8mA, depending on the error between the chips.

6. More suitable for, LED bulb, corn lamp, T5 lamp. Features Low cost, simple workmanship,

4. Summary of advantages and precautions

Cost about 2 yuan power supply program

At present, the number of Taiwan Science and Technology to develop a specifically for the LED lighting ICNU501, to achieve a low-cost constant current drive program, according to the design of the entire constant current drive power supply total cost of about RMB2 yuan.

parameter settings:

1, D1 ~ D4 through four diodes to form a rectifier bridge, AC220V AC output through the rectifier bridge DC DC.

2, C1 capacitor selection

C1 is the electrolytic capacitor circuit is mainly played a role in filtering and can improve efficiency, in order to ensure its higher efficiency, the best choice for more than 10UF, 220V AC rectification is 311V DC, the estimated value of the capacitor voltage To 300V or more.

3, the MOS switch in the circuit is mainly to bear the pressure drop, such as string 75 LED beads in the circuit, so, MOS tube to bear the pressure drop of about 70V or so, so it will compare the heat Large, need to add heat sink for heat treatment, in order to reduce the heat, the same can also be used by the MOS switch more current.

4, NU501 is 15ma to 60ma constant current design, so the choice of output current, according to their current needs to choose the size to achieve the constant current source you want.

With NU501 isolated applications, the need to add a switching power supply in the pre-class, the isolation through the front stage to show, NU501 is only a constant current role. The current switching power supply technology has been developed quite mature, cost is also high, and a variety of certification, CE, UL and so are easy to pass, or most manufacturers have adopted a variety of certification, so we just used to save development Time, just put the NU501 IC board on the light can, road constant current, high precision.

In LED lighting module applications are increasingly popular, because after using NU501, no need to use other constant current source.

NU501 applied to the soft light, hard light, monochrome should have a good performance, is to replace the traditional best choice for resistance.
Tag: Linear Constant Current High Voltage Power Supply Low LED Load Voltage

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