A DC stabilized power supply is a device that converts 220V AC power to a steady DC voltage output. It must go through four stages: transformation, rectification, filtering, and stabilization. The working principles of these stages are as follows:
(1) DC Power Transformer: A step-down transformer that converts the 220V AC voltage from the power grid into the required AC voltage, supplying it to the rectifying circuit. The transformer's turns ratio is determined by the secondary voltage of the transformer.
(2) Direct Current (DC) Power Rectification and Filtering Circuit: The rectification circuit converts the alternating current voltage Ui into a pulsating DC voltage. It is then passed through a filtering circuit to remove larger ripple components, resulting in a DC voltage U1 with reduced ripple. Common rectification and filtering circuits include full-wave rectification filtering and bridge rectification filtering.
(DC Power Supply Filter 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 meet 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 filter 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 Power Supply Voltage Stabilization Circuit: The function of the voltage stabilization circuit is to maintain a stable output DC voltage, unaffected by changes in AC grid voltage and load. Common integrated voltage regulators include fixed three-terminal regulators and adjustable three-terminal regulators. Common adjustable positive voltage integrated regulators are the CW317 (LM317) series, which offer adjustable output voltages from 1.25V to 37V. The simple circuit requires only one fixed resistor and a potentiometer as external components. The chip features transition, overheat, and safety operating area protection, with a maximum 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), with R1 typically ranging from 120 to 240 ohms. The voltage difference between the output and adjustment terminals is the reference voltage of the stabilizer (typically 1.25V).
