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Technical article - teach you to design an adjustable regulated power supply circuit

How do we usually design an adjustable regulated power supply circuit? DC regulated power supply adopts the current international advanced high-frequency modulation technology. Its working principle is to broaden the voltage and current of switching power supply, realize the wide range regulation of voltage and current, and expand the application of current DC power supply. This paper will introduce some adjustable regulated power supply circuits

working principle

when inputting AC voltage and then applying a constant ultrasonic vibration of 150v-260v to them, the output voltage stabilization effect is good at 220V. Below and above this range, its efficiency will decline. A single-chip microcomputer is used for the first step control, so that the input voltage below 310V and above 90V is adjusted and controlled in the range of 190v-250v, and then the parameter regulator is used for voltage stabilization, which has a good effect

the AC voltage input from the mains fluctuates greatly. After the interference voltage such as high-frequency pulse is filtered out by the overvoltage absorption filter circuit, it is sent to the DC switching regulated power supply, AC sampling circuit and control execution circuit

the power of DC switching regulated power supply is small, but it can change the AC voltage of V into the DC voltage of +5v, +12v, -12v+ 5V voltage is supplied to the single-chip microcomputer, and ± 12V voltage is supplied to the high-power switch module of the control circuit

the single-chip microcomputer analyzes and judges the input voltage data collected by the sampling circuit and sends a control signal to the trigger circuit to control and adjust the output voltage

the control execution circuit is composed of SSR zero crossing switch high-power module and autotransformer with tap. RC absorption circuit is used between SSRs to absorb overvoltage and overcurrent, so that SSR will not be damaged during switching. The control executive circuit controls the 310V input voltage of 90 freezer): overload thermal relay (protecting the overload of blower and freezer) in the range of 190v-240v, and then sends it to the parameter regulator for accurate voltage stabilization

the parameter regulator consists of an LC oscillator with inductance and capacitance, and the oscillation frequency is 50Hz. No matter how the mains power changes, its oscillation frequency will not change, so the output voltage will not change, and the voltage stabilization accuracy is high. Even if the input voltage waveform is distorted greatly, it is a standard sine wave after oscillating by the parameter regulator. Therefore, the regulated power supply has strong anti-interference ability and purification ability

protection alarm circuit: when there is a situation endangering the safety of the equipment, only audible and visual alarms will be sent to remind the operator to take measures without cutting off the output voltage. When there is no output voltage, the temperature of the control box is too high, the mains power input is higher than 300V, and the mains power input is lower than 130v, an audible and visual alarm will be given. When the input current is too large, the input (output) air automatic switch will automatically jump off

three terminal adjustable voltage regulation circuit diagram

circuit working principle: 220V AC is reduced by transformer T to obtain 24V AC; After full bridge rectification and C1 filtering composed of VD1 ~ VD4, a DC voltage of about 33V is obtained. The voltage is stabilized by the integrated circuit LM317. Adjust the potentiometer RP to continuously adjust the output voltage. In the figure, C2 is used to eliminate parasitic oscillation, C3 is used to suppress ripple, and C4 is used to improve the transient response of regulated power supply. Vd5 and vd6 play a protective role in case of capacitor leakage at the output end or short circuit at the adjustment end. LED is the working indicator of regulated power supply, and resistance R1 is the current limiting resistance. A miniature voltmeter PV is installed at the output end, which can directly indicate the output voltage value

circuit diagram of adjustable regulated power supply V 1.5A

external series bypass transistor increases the rated output of 500mA 78mg or 79mg to 1.5A, which is suitable for laboratory adjustable power supply. The external bypass transistor of the circuit has no short-circuit protection, but this paper introduces how to add a protective transistor to avoid short-circuit

voltage 1 5. The current of 0.2A can be adjusted and stabilized, which has no impact on the use of most workpieces. The voltage supply

is composed of diode vd1-vd4 rectification, transistor vt2 and VT3 compound adjustment, transistor vt4 comparative amplification, regulator vd7 reference voltage source, regulator vd5 constant current source and resistors R1, R2, R3, transistor vt4 current limiting protection and detection resistance R0

if the output voltage changes for some reason (the input operator can change the working voltage or load current in a comfortable and natural manner, efficiently and permanently), the comparison and amplification part amplifies the change signal and sends it to the adjustment part to make it produce opposite changes to offset the change of the output voltage

potentiometer RP and resistor R6 sample the output voltage and send it to the comparison and amplification part of transistor vt4 to compare with the reference voltage of regulator vd7. In the circuit, the voltage regulator vd5 and resistors R1, R2 and R3 form a bias circuit, which makes the collector current IC passing through transistor VT1 change very little and can be considered as constant basically. Therefore, this part of the circuit is generally called constant current source load

in the circuit, the transistor vT5 and the detection resistance R0 form an overload and short-circuit protection circuit. When the load current exceeds the fixed value or is short circuited, the voltage drop on the detection resistance ro will be greater than the on voltage (0.5V) of vT5, making vT5 on, and most of the current sent by the constant current source flows into vT5, reducing the base current IB of the regulator, thereby limiting the output current of the regulator