A linear drive circuit for led lighting fixtures

Abstract

The invention discloses a linear drive circuit for high light efficiency LED lighting fixtures, which is composed of four parts: an input protection circuit, a bridge rectifier, a constant current control circuit and an overvoltage shutdown circuit. The constant current control circuit is similar to the traditional linear drive circuit of LED lighting fixtures. The overvoltage shutdown circuit is connected in series between the negative terminal of the constant current control circuit and the negative terminal of the rectifier bridge. The input voltage sampling circuit, reference power supply, comparator CP , N-channel power switch tube, generally suitable for small and medium power LED light source lighting fixtures, with high luminous efficiency, small temperature rise of constant current control tube, small power-on surge current, wide input voltage range and so on.

Description

technical field [0001] The invention relates to the field of LED lighting, and more specifically, to a linear drive circuit for LED lighting lamps. Background technique [0002] LED light source has the advantages of environmental protection, energy saving, long service life, low driving voltage, etc., and is recognized as the most promising lighting source in the 21st century. Due to the limitation of cost, lamp size, EMI interference and other factors, in recent years, small and medium power LED lighting lamps, such as bulb lamps, light pipes, ceiling lamps, spotlights, etc., have mostly adopted linear drive methods. The traditional LED linear drive circuit with capacitor filter is mainly composed of insurance tube FUSE, varistor VR, bridge rectifier BR, filter capacitor C, series LED chipset, LED working current sampling resistor Rs, current amplifier CA, reference voltage source V ref , adjustment tube Q and bias circuit, etc., as attached figure 2 shown. Although thi...

AI Technical Summary

Problems solved by technology

Although this type of linear drive circuit has the advantages of fewer components, low cost, and low EMI, it can only work in power supply occasions where the AC input voltage does not vary by more than 5%, such as LED chipsets selected according to 220V input voltage, when AC input Voltage U IN When it is too high, the adjustment tube Q drain-source voltage V DS It will also increase synchronously, which not only makes the power supply efficiency drop rapidly, but also increases the temperature of the adjustment tube Q, which will lead to overheating and damage of the adjustment tube Q in severe cases; on the other hand, when the input voltage U IN low, the bridge rectifier BR output voltage V IN Less than the series LED chipset operating voltage V F When the current flowing through the series LED chipset drops, serious stroboscopic phenomenon will appear

The third is that the filter capacitor C has a large capacity, and the surge current at the moment of power-on is large, and it may be necessary to connect a thermistor with low reliability in series in the AC input circuit.

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