基才DC／DC开关稳压器的大功率LED恒流驱动设计

针对当前市面上DC／DCLED（发光二极管）专用恒流控制芯片价格高、不易购买的情况，阐述了基于市面常用DC／DC稳压器的高效率恒流稳压电源的通用设计方法，并给出了基于LM2596-ADJ开关稳压器的设计实例。与传统的恒压电源相比．电路增加了阻值很小的采样电阻以及由通用运算放大器组成的电压反馈回路和电流采样、放大反馈回路．同时增加了电压、电流反馈回路自动切换电路，使电路能根据负载大小在恒压和恒流模式之间自动切换。实验数据表明．基于该方法设计的LED恒流稳压电源恒流精度高，误差小于1％，效率超过87％，且电路工作稳定，元件取材广泛．价格低廉。

Design of LED driver based on the general DC/DC regulators

To the question that the special current controller for LED driver is expensive and hard to get from the market now,a general method on designing a high efficiency constant-current source for LED driver with the general DC/DC regulators is presented,which are cheap and can be easily got.A design example based on the adjustable output version of LM2596 is presented.Compared with the conventional DC/DC regulators,a current feedback made up of a small sense resistor and an operational amplifier are utilized to control the output current by monitoring and amplifying the voltage drop across the sense resistor.In order to clamp the output voltage does not exceed the maximum for a no load condition at the output,a voltage feedback consisting of a resistor divider and an operational amplifier is used.The example circuit can operate at the constant-current mode and constant-voltage mode automatically according to load.The experimental results show that the circuit works stably,and it presents over 87% efficiency and less than 1% current error.