Working Principle of DC Regulated Power Supplies
1, Working principle of DC stabilized power supply
A DC stabilized power supply is a device that converts 220V AC power into a stabilized output DC voltage. It requires four stages of transformation, rectification, filtering, and stabilization to complete.
The working principle of the four stages is as follows:
(1) Power transformer: It is a step-down transformer that converts the 220V AC voltage of the power grid into the required AC voltage and sends it to the rectifier circuit. The transformation ratio of the transformer is determined by the secondary voltage of the transformer.
(2) Rectification and filtering circuit: The rectification circuit converts the AC voltage Ui into a pulsating DC voltage. After filtering out larger ripple components through a filtering circuit, a DC voltage U1 with smaller ripple is output. Common rectification and filtering circuits include full wave rectification filtering, bridge rectification filtering, etc.
(3) Filter circuit: It can filter out most of the AC components in the output voltage of the rectifier circuit, thereby obtaining a relatively smooth DC voltage. Each filter capacitor C satisfies RL-C=(3-5) T/2, or T is the input AC signal period, and RL is the equivalent load resistance of the rectifier filter circuit.
(4) Voltage regulator circuit: The function of a voltage regulator circuit is to stabilize the output DC voltage, which does not vary with changes in AC grid voltage and load. The commonly used integrated voltage regulators include fixed three terminal voltage regulators and adjustable three terminal voltage regulators. The output voltage of commonly used voltage regulators can be adjusted from 1.25V to 37 volts, and simple circuit external components only require a fixed resistor and a potentiometer. The chip has transition, overheating, and * * working area protection, with a maximum output current of 1.5A. The resistor R1 and potentiometer R2 form an output voltage regulator, and the expression for the output voltage Uo is: Uo=1.25 (1+R2/R1). R1 is generally taken as 120-240 ohms, and the voltage difference between the output terminal and the adjustment terminal is the reference voltage of the regulator (typical value is 1.25V).
2, Application of DC stabilized power supply
DC stabilized power supply is an indispensable device in the field of electronic technology. Common DC stabilized power supplies mostly adopt the series feedback stabilized principle, and adjust the output voltage by adjusting the potentiometer in the sampling resistor branch of the output terminal. Due to the nonlinearity and narrow adjustment range of potentiometer resistance changes, it is difficult for ordinary DC stabilized power supplies to achieve adjustment of output voltage.
3, The prospect of DC stabilized power supply
In recent years, with the development of technology, the operating frequency of DC stabilized power supplies has increased from tens of kilohertz to hundreds of kilohertz; Research has shifted towards the topology theory, working principle, modeling analysis, and other aspects of high-frequency power supplies; The development and application of DC stabilized power supplies have become increasingly mature.
