LED Driver ZD1680

The input voltage of LED driver ZD1680 is 7V~12V, and it automatically adjusts the appropriate output voltage according to the number of LEDs driven.

ZD1680 has 6 drive terminals. There are 6 corresponding "allow input" terminals, so each drive terminal can be controlled separately. In addition, there are short circuit and open circuit alarm output terminals, which can be used to monitor the driving status of the LED.

The circuit of ZD1680 driving low-power LED is shown in Figure 1. When the sampling resistance Rsense is 0.12Ω, the driving power is 10W, and 100 LEDs with a power of 0.1W can be driven; when Rsense is 0.6Ω, the driving power is 15W, and 15 LEDs with a power of 1W can be driven.

Figure 2 is a circuit for driving 15 power LEDs, VBATT is 7V~12V, VDD is 5V, and the EN and CE pins of the driver are connected to VDD. At this time, according to the formula recommended in the product manual, the driving voltage Vout=0.5(R5+R6)/R6, R5=120kΩ. R6=1kΩ. Therefore, the calculated value Vout=60.5V. However, the actual measured values ​​are shown in the attached table, which have a slight error with the calculated values.

The driving current ILED=500/Rset, where "500" is the number recommended in the product manual. When Rset is 10kΩ, the calculated value is 500/10kΩ=50mA. That is, each driver can output 50mA current. If the six driver terminals are short-circuited, there should be 300mA current, but the actual measurement is only 180mA. It can be seen that the recommended coefficient "500" is not reliable. The coefficient calculated based on the actual measured value is 290, that is, ILED=290/Rset. It is calculated that one driver outputs 50mA, and the Rset value is 5.8kΩ.