However, in the discussion of the theory, usually about the PN junction refers to the ideal knot. In an ideal junction is not considering its bulk resistance. In the actual device, not only the memory of the PN junction region in resistance, the body region in a semiconductor material existence of resistance, resistance exist in the contact surface of the semiconductor material and the outer electrode, the electrode material for the existence of resistance, the electrode material and the outer lead exposure exists resistance, outer lead existence of resistance, and so, in fact, there are a lot of resistance. Voltage temperature characteristics of led high bay light is a positive function. The actual measurement of an LED VF not only is the PN junction barrier voltage EPN, but also includes the resistor voltage. This had an impact on the actual voltage – a function of temperature between.
Usually in the Test mains led lights voltage – temperature relationship in a static thermostat, give LED for into a transient current, and read the voltage value within a very short time. The purpose of this approach is to exclude the current the voltage drop across the resistor. Small current test results, does not reflect the voltage of the mains led lights in the normal current – temperature relationship. A large current, the parasitic resistance can not be ignored. Current increases, the higher the temperature the greater the voltage drop on the parasitic resistance. And the voltage on the parasitic resistance is a function of temperature, the voltage on the parasitic resistance with increasing temperature will be significantly offset by the PN junction voltage drop.