High-voltage linear application (bridge-drive mode) will become a joke four years ago. It depends on the price competition of LED downstream lamps and the development of high-voltage linear technology. The driving mode of LED lighting lamps within 30W has been widely promoted. application. However, problems and controversies based on PF values, stroboscopic and other applications have become increasingly prominent. On the evening of January 30th, the “Lighting Industry Elite Meeting†organized various applications and technical measures arising from the application of high-voltage linear applications. discuss. The forum was hosted by Wu Jinshui and the text was organized by Chen Bingquan.
The linear power supply first reduces the voltage amplitude of the alternating current through the transformer, and then rectifies it by the rectifier circuit to obtain the pulsed direct current, and then filters to obtain the direct current voltage with a small ripple voltage. To achieve high precision DC voltage, it must be regulated by a voltage regulator circuit.
First, the linear power supply is the future development trend of power LED indoor lighting
Generally speaking, the thyristor is a device that controls the voltage. Since the conduction angle of the thyristor can be controlled by the circuit, the conduction angle of the thyristor also follows with the change of the output voltage Uo. Change. The voltage Ui applied to the primary of the main transformer also changes. That is, ~220V mains is only added to the primary of the main transformer after the thyristor control. When the output voltage Uo is high, the conduction angle of the thyristor is large, and most of the mains voltage is “released†by the thyristor (as shown in the figure above), so the voltage applied to the primary of the transformer, that is, the Ui is higher. This of course, after the rectification and filtering, the output voltage is relatively high. When the output voltage Uo is very low, the conduction angle of the thyristor is very small, and most of the mains voltage is “snapped†by the thyristor (as shown in the figure below), and only a very low voltage is applied to the transformer primary. That is, Ui is very low, which of course, after rectification and filtering, the output voltage is very low.
two. The main circuit of the linear power supply is as follows:
The linear power supply is actually a high-power triode (actually multiple parallel) at the output of the thyristor power supply. The control circuit can control the output current of the triode by outputting a small current to the base of the triode. The power supply system is regulated once more on the basis of the thyristor power supply. Therefore, the regulation performance of this linear regulated power supply is better than that of the switching power supply or the thyristor power supply by 1-3 orders of magnitude. However, the power transistor (also known as the regulating tube) generally occupies 10 volts. Each output of 1 amp is required to consume 10 watts of power inside the power supply. For example, the 500V 5A power supply has a loss of 50 watts on the power tube, accounting for the total output. The power is 2%, so the efficiency of the linear power supply is slightly lower than that of the thyristor power supply.
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