| With the rapid development of semiconductor lighting technology,the performance of semiconductor light-emitting diodes(LEDs)has been greatly improved,so that LED devices are becoming more and more widely used.And in constant exploration and discovery,alternating current light emitting diode(AC-LED)has been invented that can be directly driven by AC voltage.Compared with traditional DC-LED devices,AC-LED devices have various advantages,and they have different performances in electrical,thermal,and optical properties.This paper starts with the thermal characteristics of AC-LED devices,and proposes a method and device for measuring the thermal resistance and junction temperature of AC-LED devices ?sing AC pulse signals,and verifies the accuracy and feasibility of the method through experiments.This paper was organized as follows:In charpter 1,the development history of LED devices and the development and application prospects of AC-LED devices are briefly introduced.The structural characteristics of AC-LED devices are also described.The traditional methods of heat generation and junction temperature testing of LED devices are briefly introduced.The necessity of studying thermal characteristics of AC-LED devices.In charpter 2,Compared with DC-LED1 device junction temperature detection method,a method for testing AC-LED device using AC pulse signal and its implementation steps are proposed.A narrow pulse is used as the voltage source signal to act on the AC-LED device,and the temperature sensitivity coefficient(current)of the AC-LED device is tested.A linear formula is fitted between the junction temperature and the current amplitude of the AC-LED device.We obtained the thermal resistance value of the AC-LED device,and then obtained the junction temperature of the AC-LED device with the thermal resistance value as a bridge.In order to obtain the junction temperature of the AC-LED device in the actual working state,we pass the sine wave voltage signal into the AC-LED device,and measure the optical power Po and the electric power(Pe=IVcos?)of the AC-LED device,when operating in AC.And we calculated the junction temperature under this working condition.And the influence of pulse width on the junction temperature of the AC-LED device was explored.AC-LED die was measured by using different pulse width AC voltages as the voltage source to measure the AC-LED bare chiptemperature,so that determining ideal AC pulse width range.In charpter 3,the main characteristic parameters of the AC-LED device are described in detail.The AC pulse signal source used in this experiment and the system composition for measuring the thermal resistance and junction temperature of the AC-LED device using the AC pulse signal are introduced.And we introduced AC-LED device structural characteristics and current and voltage signals.the AC-LED temperature sensitivity coefficient and thermal resistance are experimentally measured,the junction temperature of the AC-LED device is calculated by the thermal resistance,and the junction temperature of the AC-LED device operating under a sinusoidal voltage is calculated.Finally,we compared the junction temperature test of AC-LED die and calculated values to verify the accuracy and feasibility of this method.The advent of AC-driven LED devices has not only greatly facilitated the application of LED lamp products,but also greatly reduced the power consumption of AC and DC conversions,and reduced the use of electronic components in switching power supplies.It has solved the problem that the lifespan of electronic components is far below.The problem of the lifetime of the LED device greatly increases the service life of the entire lamp.Through the research and analysis of the thermal characteristics of AC-LED devices and the measurement of the junction temperature of AC-LED devices ?sing AC pulse signals,it will be helpful to further study the overall performance of AC-LED devices.It is very important to study the thermal characteristics of AC-LED devices in the future. |
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