The mainstream DC sub-power supplies are categorized into three major types based on their working circuit structure: silicon-controlled rectifier (SCR) DC power supplies, linear DC power supplies, and switching DC power supplies.
(1) In simple terms, silicon-controlled rectifier (SCR) power supplies regulate output voltage and current levels by adjusting the conduction angle of the SCR. Thanks to their robust output power and the advantage of ultra-high power supply specifications, SCR power supplies are irreplaceable by transistor linear power supplies and switching power supplies.
(2) Linear power supplies achieve voltage and current adjustments and stabilization by controlling the base of a transistor, also known as a regulating tube. This process is akin to a secondary stabilization on a silicon-controlled rectifier (SCR) power supply, resulting in a superior output power quality. However, due to the typical 5-10V voltage drop across the power regulating tube, efficiency is lower than that of SCR power supplies. For every 1A of output current, an additional 5-10W of power consumption is incurred, particularly for low-voltage, high-current specifications where efficiency ratings are even lower.
(3) Switched-mode power supplies adjust output voltage and current by controlling the pulse width of PWM signals, achieving stable voltage and current. Due to their high operating frequency, they eliminate the need for silicon-controlled rectifiers and linear power supplies' power transformers, being replaced by high-frequency transformers. This results in compact size and high efficiency, also known as high-frequency switched-mode power supplies. Initially limited by high-frequency power semiconductor devices, switch-mode power supply technology was not yet mature, and silicon-controlled rectifier and linear power supplies were irreplaceable. With the advancement of high-frequency semiconductor devices, the operating frequency and power of semiconductor power devices have increased, making switch-mode power supply technology more mature. Manufacturers with strong technical capabilities have achieved reliability and performance metrics that can match and even surpass conventional linear power supplies. Additionally, with their compact size and lightweight design, switch-mode DC power supplies are gradually replacing silicon-controlled rectifier and linear DC power supplies, especially for high-power specifications. This trend is particularly evident in the gradual withdrawal of silicon-controlled rectifier and linear DC power supplies from the market, including 36V aviation power supplies, 400Hz frequency converter power supplies, 115/200V power supplies, 27V DC power supplies, 400Hz power supplies, and aviation power supplies.
Currently, the high-power DC power supply market in China still lags behind international brands in terms of optimization of high-frequency switching circuit structures. The reliability and performance indicators do not meet the standards of industry manufacturers. Many domestic manufacturers are still using silicon-controlled rectifiers (SCRs) and linear circuit structures to produce high-power specifications of SCR and linear power supplies. However, these technologies are largely obsolete abroad and have been replaced by high-frequency switching circuits. Therefore, when selecting power supplies based on demand, the standard for evaluating the quality of DC power supplies cannot be directly determined by simple circuit structures or power supply names.
