As a kind of light emitting diode, deep ultraviolet uvc-led has positive nonlinear IV characteristic. And the main market of uvc-led VF value range is large, the typical value is 5 ~ 7V. Therefore, it is recommended to use constant current IC for accurate current control in the actual drive circuit. In order to save cost, resistance series voltage divider can be used in some cases. However, it is not recommended to use other LEDs in series for partial voltage, which may lead to LED overload and burnout.

1、 Three typical driving schemes

A: Constant current IC drive

The constant current IC completes the conversion from constant voltage to constant current, which is suitable for the application scenarios of mainboard power supply above 9V. The small range fluctuation of the main board power supply voltage will not affect the lamp bead current. And different batches of VF difference led in this scheme work current value also get very good consistency control.

B: Series resistance voltage divider

Driven by a constant voltage power supply higher than the lamp bead VF, the voltage at both ends of the LED is regulated by series resistance. The final current control scheme is common in blue and white light industry. In the application of uvc-led, a typical method is to connect a 150 Ω resistor in series under 12V constant voltage to control the circuit current at about 40mA.

C: Series blue photodiode partial voltage

In some cases, in order to simplify the circuit, the direct use of indicator lamp for voltage division to exercise the effect of resistance voltage division.

2、 Comparison of IV characteristics of three schemes

The research objects in this comparison are uvc-led with VF of 5V, uvc-led of 7V, blue LED of 2.67v and resistance of 175 Ω at 40mA.

Scheme A: according to the characteristics of constant current IC (nu501c), it can be found that when the load VF changes from 5V to 7V, the output current almost has no fluctuation

Scheme B: under 12V constant voltage, the actual working current difference between the two VF is 28ma and 39mA, with a difference of 28.2%

Scheme C: when the series LED is divided into voltage, the characteristic that the voltage increases sharply with the current is retained. Under the same 12V, the working current of uvc-led circuit with VF = 7V is 24Ma, and the current of 5V VF is directly more than 100mA. This may directly lead to LED burn out and reduce the yield of finished products.

3、 Summary and comparison

4、 Availability of resistance series scheme

How to evaluate the current fluctuation caused by series scheme? DUVTek "current fluctuation assessment tool under resistance series voltage divider driving mode" can be usedhttp://www.iduser.cn/solution/5/。