1 Introduction

In modern industrial production, thyristors have been widely used due to their mature technology, large current and high voltage. In the automatic control system composed of thyristors, many of them are constant current and voltage closed-loop control constant voltage applications. However, most of the current constant current and constant voltage thyristor devices and products are restricted by sensors and control circuits, and are bulky, complicated in circuits, difficult to debug, and low in control accuracy. And because of the use of shunt and voltage divider for sampling, there is no isolation measure, the electromagnetic interference of the control circuit is large, and it is difficult to interface with the computer. The application of thyristor constant current and constant voltage equipment is in a more difficult state. The constant current and constant voltage equipment using thyristors has a large application space due to its wide range of constant voltage (0 to several hundred volts) and constant current (0 to several hundred amperes). The constant current and constant voltage intelligent module produced by our company solves the contradiction between this application and manufacturing.

Compared with the traditional constant current and constant voltage equipment, the constant current and constant voltage intelligent module adopts linear Hall sensor, high-precision control circuit and modular production technology. The characteristics of small size and convenient use will surely obtain a large number of applications.

2. Working principle

(1) Main working circuit

The main circuit of the constant current and constant voltage intelligent module (rectifier) ​​is shown in Figure 1. It is a three-phase fully controlled rectifier bridge composed of six thyristors, and a DC voltage of 0-50V can be obtained by changing the conduction angle of the control circuit.

figure 1

figure 2

The working principle diagram of the control system is shown in Figure 2

(1) Adoption of Hall sensor

Hall effect sensor is a new type of current and voltage sampling device. Its working principle is to use the Hall effect of Hall element to induce voltage in a magnetic field to convert current and voltage into voltage signals. The advantages of the Hall sensor are high conversion coefficient, electrical isolation, fast response speed, and good linearity, which have great benefits for improving the performance of the whole machine.

2. Control system characteristics

(1) The linear Hall sensor is used to achieve electrical isolation, improve the performance of the whole machine, make the set voltage (0-10V) have a good linear relationship with the output voltage and current, and overcome the phase shift angle and output voltage of the thyristor The disadvantage of non-linearity.

(2) Voltage feedback and current feedback adopt two independent circuits, which do not affect each other, and can realize automatic conversion through external level.

(3) Multiple protection functions make it safer and more convenient to use.

(4) The digital phase shift control circuit is used to make the trigger more accurate and reliable.

3. The main technical parameters and functions of the constant current and constant voltage smart module

Due to the use of high-precision Hall sensors and precision amplifying circuits, modular products shorten the signal transmission distance between the control circuit and the phase shift circuit, the main circuit, and have the characteristics of low interference, so that the constant current and constant voltage module has higher control accuracy , It has greater advantages than other products with the same function.

(1) Higher control accuracy is within the range of good linearity on the thyristor control curve (constant voltage is 100V-350V, constant current is about 35%-75%I (maximum set current)), and the voltage regulation accuracy is 0.5 %, the accuracy of steady current is within 1%, in the range of poor linearity, the accuracy of voltage stabilization is not more than 1%, and the accuracy of steady current is not more than 2%.

(2) Grid adjustment rate: Grid change ±20%, output change (within the adjustment range) is not more than ±1%.

(3) High linear correspondence, 0-10V setting has a good linear relationship with output current (voltage), and the nonlinearity is not more than 5%.

In addition to the constant current and constant voltage function, the module also has the following functions:

Multiple protection functions, three protection functions of overcurrent, overheating, and lack of phase protection make the module application safer.

Sampling signal output, Hall sensor sampling signal output, external current and voltage display can be connected.

Prohibit the constant current and constant voltage function. If you are not satisfied with the internal constant current and constant voltage effect, you can connect an external control circuit and directly use the sensor sampling signal.

4. Applications of constant current and constant voltage modules

The constant current and constant voltage intelligent module is characterized by its high control circuit precision, good balance, wide working voltage range, good current impact resistance, simple installation and use, high reliability, small size, maintenance-free, and is conducive to miniaturization of power supplies. It can be widely used in various occasions such as motor, generator excitation, DC screen (battery charging), laser power supply, magnetizing equipment, UPS power supply and so on. It is more widely used in the application of "suspension superimposed" linear power supply, which is widely used in modern foreign countries. Can reflect the characteristics of the module.

(1) Basic application principle diagram (Figure 3)

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(2) Application principle diagram of AC constant current and constant voltage in electroplating and electrolysis (Figure 4)

(3) Application in floating superimposed linear power supply (Figure 5)

This device is used for high-precision high-power linear regulated power supplies, which greatly reduces the power consumption of the GTR, greatly improves the efficiency and reliability, and can use a smaller power GTR to reduce the cost. The use of constant current and constant voltage modules not only improves accuracy, but also greatly reduces the size of the power supply.