The Design Of High-precison Constant Current LED Drive Circuit With Novel Thermal-shutdown Function And Low-power

Currently, with the world’s growing shortage of energy resources, this situation prompted us to improve awareness of energy saving. In this context, the energy saving LED lighting is increasingly favored by the market. LED lighting as a green lighting light source is occupying a more and more important role in the lighting field with high luminous efficiency, low power consumption, longe-lived,rich colors,good adjustability,energy saving and environmental protection. As Scientific research shows,when the forward voltage across the LED small changes, it will lead to dramatic changes in the current. Then heat production of LED will rapidly increase which will result in the failure of LED. Therefore, we use constant current drive way to design LED driver circuit in most cases. With the widespread application of high-power white LED lighting and decorative lighting, demand for high-power white LED driver chip is growing. output power increases so that the chip temperature rises significantly. This will lead to a sharp increase in driving ability MOS tube,will cause an increase in IC failure rate.In order to play high-power energy-efficient LED lighting in the area of superiority,This requires that we need to design a highly integrated, long life, high efficiency, high reliability constant current driver chip,Using it to meet the needs of LED lighting in the practical application of.Aiming at the shortcomings of current LED driver chip constant current output,power, stability, and single over-temperature protection function, this paper designed a new over-temperature protection, high-precision, low-power LED constant current driver chip:(1)This paper describes LED’s development history, strengths and weaknesses and its application. The paper take a general description of LED including the luminous principle, characteristic parameters( luminous flux, luminous intensity, brightness and color temperature, etc.), several properties( optical properties, electrical properties and thermal properties) and limit parameters.As the over-temperature protection circuit of current driver chip has the shortcomings of high stable voltage, high power consumption and so on.Previous studies have focused on reducing the power consumption of the circuit, raising the temperature detection accuracy and circuit switching speed and other aspects.The design has achieved the function of double temperature hysteresis and thermal buffer protection. The time-domain and temperature range are adjustable in this stage of buffer. The circuit has atemperature hysteresis interval of 6 ℃ and 23 ℃ in the thermal buffer jump points and thermal break point respectively which avoids the thermal oscillation in circuit. The span of the normal work area of the circuit can be expanded in this design, a stable and efficient operation of the circuit. While the design of low-power PTAT voltage generating circuit to achieve two PTAT voltage with low-power output, to achieve a buffer chip over temperature protection.(3)In order to improve the accuracy of the output current, this paper presents a solution by using high-precision current mirror and trimming circuit. Our program used the clamping action of the power NMOS transistor’s drain with the operational amplifier,While the MOS transistor is worked by the way of common source and common-gate, the circuit of the power NMOS transistor will operate in the linear region to achieve constant current output, achieving the purpose of low power consumption.