Introduction to linear power supplies and how they work


Introduction to linear power supplies: The linear power […]

Introduction to linear power supplies:
The linear power supply is an energy conversion device that first converts the alternating current through a transformer to reduce the amplitude of the voltage, and then rectifies the internal rectifier circuit to obtain a pulsed continuous current, and then it is filtered to obtain a DC voltage with a small ripple.
The linear power supply works:
The linear power supply is actually a high power triode at the output end of the transformer. The control circuit can control the output current of the triode by sending a small current to the base of the triode, so that the energy system is regulated once more on the basis of the transformer. Therefore, the voltage regulation performance of this linear regulated power supply is 1 to 3 orders of magnitude better than that of a switching power supply or a transformer. However, the power transistor (also known as the regulator tube) usually occupies 10 volts. Each 1 amp output requires consuming 10 watts of power inside the power supply. For example, the 500 V 5A power supply has a 50 watt loss in the feed tube, which represents the total output. The power is 2%, so the linear power supply is a little less efficient than the transformer.
The advantages of the linear power supply: stable performance, without high frequency ripple and other interferences. Disadvantages of linear power: heat, low energy efficiency. No super power supply available
The voltage feedback circuit of the linear power supply is operated in a linear (amplified) state, and the voltage of the switching power supply is a tube adjusted to the voltage operating in the saturation and cutoff regions. say, the switching state. The linear power supply takes samples of the output voltage and then feeds it to the comparison voltage amplifier, which acts as the input of the voltage regulation tube to control the adjustment tube so that its junction voltage changes with the input , thus adjusting the output voltage. However, the switching power supply changes the output voltage by changing the working cycle of the adjusting tube to change the duty cycle. Of the main features: although the technology of the linear power supply is mature, but the production cost is not low, the price has already lost too much advantage compared to the switching power supply, but the linear power supply can achieve a high stability Smaller, its own interference and noise are relatively small, but due to the working frequency (50 Hz), the transformer is relatively large, the efficiency is low, the overall volume is large, it is more cumbersome and the input voltage range is high; The power supply is a high frequency operating state. The size of the transformer is relatively small and relatively light, but the ripple output is greater than that of the linear power supply, but the structure is simple, the cost is low and the efficiency is high (the efficiency of the power supply switching in the market can reach 90). More than% has replaced the linear power supply on many occasions, which is the trend of energy development in the future.