High-efficiency and low-cost non-isolated light-emitting diode (LED) constant current driver

Abstract

The invention relates to a high-efficiency and low-cost non-isolated light-emitting diode (LED) constant current driver. The high-efficiency and low-cost non-isolated LED constant current driver comprises a load circuit, a control circuit and an inductive circuit, wherein the control circuit comprises a duty ratio control circuit and an operational amplifier, the control circuit samples current of the inductive circuit as a feedback signal of the control circuit, compares the feedback signal with reference voltage of the control circuit, and sends a resulting error signal to the duty ratio control circuit so as to control opening and closing a power switch of the load circuit to achieve the function of controlling output current, the load circuit comprises an input voltage end, the power switch, a semiconductor diode, an output capacitor and an LED load, and the inductive circuit achieves constant current control of the load circuit through a manner of series impedance sampling of inductance.

Description

technical field [0001] The invention relates to an LED constant current driver, in particular to a non-isolated LED constant current driver. Background technique [0002] At present, more and more step-down topology (Buck) is used in the design of non-isolated LED constant current drivers. This is because the Buck circuit has relatively good conversion efficiency, and its circuit structure is simple for design. Cost savings. [0003] Such as figure 1 As shown, the traditional step-down converter generally consists of an input voltage Vin, a power switch S1, a semiconductor diode D1, an inductor L, an output capacitor Cout and a sampling resistor Rsen in structure. The control circuit samples the current flowing through the inductor L through the sampling resistor Rsen as the feedback signal of the control loop, and then compares it with a fixed reference voltage VREF, and the generated error signal is sent to the duty cycle control circuit to control the conduction of the ...

AI Technical Summary

Problems solved by technology

[0007] However, there are two main defects in this design: one is that the sampling resistor is connected in series with the inductor, so the inductor current will generate a large conduction loss on the sampling resistor and reduce the efficiency; the other is that due to the existence of the sampling resistor, the system The cost of design will also increase accordingly, and this is the main shortcoming of traditional technology

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