Design of LED Driver Circuit Based on ZXSC300 Series DC-DC Controller

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Overview:
As an alternative to low-voltage lighting for halogen lamps, LED lighting is becoming increasingly popular. Unlike halogen bulbs, LEDs have no problems with low efficiency, poor reliability, and short life. This article describes a new approach to driving high-power LEDs in DC lighting systems that delivers 95% efficiency, longer life, and withstands higher electrical and mechanical shocks.

In the circuit shown in Figure 1, the ZXSC300 series DC-DC controller drives an external switch that operates in buck mode. Table 1 lists the bill of materials for the 12V power system. By increasing the value of R2, a higher system voltage can be provided. For example, to obtain a voltage of 24V, it is only necessary to change the value of R2 to 2.2kΩ, and the capacitor C1 must also have a higher rated voltage. The basic working principle of the circuit is as follows:

When Q1 is turned on, current flows through the LED, capacitor C2, and inductor. When the voltage drop across R1 reaches the threshold voltage of the Isense pin, Q1 turns off and remains for a fixed time, and the energy in the inductor flows through D1 and the LED. After this fixed time, Q1 is turned back on, and so on.

Figure 1: LED driver using a buck mode DC-DC converter.
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