Numerical control DC current source circuit design

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Numerical control DC current source circuit design

The system takes the DC current source as the core, and the AT89C52 single-chip microcomputer is the main controller. The output current of the DC power supply is set by the keyboard. The stepping level can be up to 1 mA, and the actual output current value and current setting value can be displayed by the liquid crystal. The system is controlled by a single-chip microcomputer to output digital signals. The analog output is output through a D/A converter (DAC7611), and then isolated and amplified by an operational amplifier to control the base of the output power tube. The output varies with the base voltage of the power tube. Current. The MCU system also takes into account the real-time monitoring of the constant current source. After the output current is converted by the current/voltage, the A/D conversion chip (ICL7135) is used to convert the analog quantity into the data amount in real time, and then analyzed and processed by the MCU. The feedback link makes the current more stable, thus forming a stable voltage-controlled current source. The actual test results show that the output current of the system is stable, does not change with load and ambient temperature, and has high precision. The output current error range is ±5mA, and the output current can be arbitrarily set within the range of 20mA~2000mA, so it can be applied in practice. The field of high stability low power constant current sources is required.

Solution 1: Various types of digital circuits are used to form a keyboard control system for signal processing, such as programmable logic devices such as CPLD. The scheme is complicated, the flexibility is not high, and the efficiency is low, which is not conducive to the expansion of the system, and the signal processing is difficult.

Solution 2: The AT89C52 single-chip microcomputer is used as the control unit of the whole machine. The output voltage value is changed by changing the input digital quantity of the DAC7611, so that the base voltage of the output power tube changes, and the output current is indirectly changed. In order to enable the system to detect the actual output current value, the current can be converted into a voltage, and the analog-to-digital conversion is performed by the ICL7135. The voltage is sampled in real time by the single-chip microcomputer, and then the data is processed and displayed. This system is more flexible, using software methods to solve the data preset and current step control, so that the system hardware is more concise, various functions are easy to implement, and can well meet the requirements of the topic.

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