A DC constant voltage power supply is a device that converts 220V AC power to a stable DC voltage output. It must undergo four stages: transformation, rectification, filtering, and regulation to complete the process.
The working principles of the four stages are as follows:
Direct Current Power Transformer: A step-down transformer that converts the 220V AC voltage from the power grid into the required AC voltage and supplies it to the rectifying circuit. The transformer's ratio is determined by the secondary voltage of the transformer.
(2) Direct Current (DC) Power Rectifier and Filtering Circuit: The rectifier circuit converts the alternating current voltage Ui into pulsating DC voltage. The filtering circuit then removes the larger ripple components, resulting in a DC voltage U1 with reduced ripple. Common rectifier and filtering circuits include full-wave rectifier filtering and bridge rectifier filtering.
(3) DC Power Supply Filtering Circuit: This circuit can largely filter out the AC components from the output voltage of the rectifier circuit, resulting in a relatively smooth DC voltage. The filter capacitors C should satisfy the condition RL-C = (3~5)T/2, where T is the period of the input AC signal and RL is the equivalent load resistance of the rectifier and filtering circuit. 36V aviation power supply, 400Hz variable frequency power supply, 115/200V power supply, 27V DC power supply, 400Hz power supply, aviation power supply
(4) DC Voltage Stabilization Circuit: The function of the voltage stabilization circuit is to maintain a stable output DC voltage,不受the fluctuations of the AC power grid voltage and the load variations. Common integrated voltage regulators include fixed three-terminal regulators and adjustable three-terminal regulators. The CW317 (LM317) series is a commonly used adjustable positive voltage regulator, with output voltages adjustable from 1.25V to 37V. The simple circuit requires only one fixed resistor and a potentiometer as external components. The chip features protection against overvoltage, overheating, and safe operating area. It offers a high output current of 1.5A. The typical circuit is as shown below, where resistor R1 and potentiometer R2 form the output voltage regulator. The expression for the output voltage Uo is: Uo = 1.25(1 + R2/R1). Typically, R1 is chosen to be 120-240 ohms, and the voltage difference between the output and adjustment terminals is the reference voltage of the regulator (typically 1.25V).
