Changes in DC power supply output
DC power supply is a commonly used electronic equipment, which ensures a stable voltage output when the grid voltage fluctuates or the load changes. A low ripple, high precision voltage regulator source has important practical applications in the field of instrumentation, industrial control and measurement. The design of this design with the transformer output of two groups of 17.5V AC winding, the design of three regulated power supply, two of which 3V-15V adjustable, the other group of fixed output +5V; rated operating current of 1.2A, and has a "+", "-" step voltage Adjustment function, the minimum step of 0.12V, ripple factor is not greater than 4%. And has a digital potentiometer X9318 to adjust the unit reference voltage change to form a highly reliable, small ripple and high precision voltage control DC adjustable voltage regulator power supply hardware circuit and microcontroller control.
Composition:
1, the power transformer will be 220V, 50Hz AC voltage into a low voltage AC voltage and output DC voltage is roughly equivalent.
2, rectifier circuit using the diode's unidirectional conductivity of low-voltage alternating current into a unidirectional pulsating voltage, can be half-wave, full-wave rectifier points.
3, filtering circuit using the impedance characteristics of inductance and capacitance, the rectified unidirectional pulsating current in the AC component filtered out, the unidirectional pulsating current into a smooth DC current.
4, voltage regulator circuit When the grid voltage fluctuations or load changes will lead to loads on the DC power obtained on the unstable, affecting the performance of electronic equipment, with a voltage regulator tube, that is, the use of a number of negative feedback way of regulating the circuit, so that it automatically adjusts the unstable factors so as to obtain a stable voltage.
Basic requirements
① with the transformer output of two 17.5V AC winding, the design of three regulated power supply, two of which 3V-15V adjustable, the other fixed output +5V;
② The maximum output current of each group: 750 mA;
③ The efficiency of each group is greater than 75%, measured under the conditions of 500mA output, should be reserved in the DC / DC input current measurement terminal;
In order to realise program control, MCU control interface should be reserved.
The output of DC power supply is not always constant, for example, when the DC power supply works in constant voltage state, its output voltage will be due to the change of input voltage or due to the change of the load and the output voltage will be caused by the change of the output voltage slightly, when the DC power supply is in the constant current working state, its output current will also be due to the change of the input voltage or due to the change of the load and the output voltage will be caused by the change of the output voltage slightly.
