High-voltage and low-voltage power switching excitation control system with low power consumption

Abstract

The invention relates to a high-voltage and low-voltage power switching excitation control system with low power consumption. The high-voltage and low-voltage power switching excitation control system consists of a power supply, an energy feedback circuit, a constant-current source control circuit, a high-voltage and low-voltage switching circuit, a lag comparison circuit, an H-bridge switch circuit, a magnet exciting coil, a current detecting circuit, an H-bridge driving circuit and an excitation sequential circuit, wherein the power supply consists of a high-voltage power supply and a low-voltage power supply; a high-voltage excitation path is simplified by the high-voltage and low-voltage switching circuit; pressure drop of devices which are selected and used for the high-voltage and low-voltage switching circuit on the path is low, power consumption of the high-voltage excitation path is reduced, so that heating is reduced, and the stability of the circuit is high; by the constant-current source control circuit, the power consumption is greatly reduced; and the H-bridge switch circuit is provided with MOS (metal oxide semiconductor) tubes with the same model, so that the switching characteristics of the switch tubes are consistent. Moreover, the pressure drop is low, consumed electric energy is also low; and the structure of the H-bridge driving circuit is simplified, the H-bridge driving circuit has a quick and complete protection function, the reliability of the system is greatly improved, and the size of the control circuit is reduced.

Description

technical field [0001] The invention belongs to the technical field of flow detection, and specifically relates to an excitation control system for switching high and low voltage power supplies of an electromagnetic flowmeter. Low-voltage switching circuit, H-bridge switching circuit and constant current source control circuit realize the switching excitation control system of high and low voltage power supply of electromagnetic flowmeter with less heat generation, higher efficiency and more reliable operation. Background technique [0002] Electromagnetic flowmeter is an instrument that measures the volume flow of conductive liquid according to the working principle of Faraday's law of electromagnetic induction. The excitation control system of the electromagnetic flowmeter applies a current that changes in a certain form to the excitation coil, and generates a magnetic field that changes in a certain form in the measuring tube. The conductive liquid flowing through the me...

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Problems solved by technology

However, this electromagnetic flowmeter excitation control system has the following disadvantages: (1) The constant current control circuit uses an open-loop operational amplifier as an error amplifier. Due to the large amplification factor and excessive adjustment, it is difficult to achieve current stability; (2) A common comparison circuit is used to control the power switching circuit. In actual implementation, due to noise interference in the environment, it is superimposed on the output signal of the current-sensing resistor, so that the power switching circuit frequently switches between high voltage and low voltage. , the output excitation current is unstable; (3) In the circuit, the energy stored in the coil is consumed in the form of heat energy by using a Zener diode, which is not conducive to reducing the power consumption and heat generation of the system

Although this excitation control system solves the difficulty of constant current control in the excitation control system of electromagnetic flowmeters based on switching between high and low voltage power sources, the power switching circuit is susceptible to interference and the heating problems of Zener diodes, it has the following deficiencies: (1) The high-voltage power supply has redundancy in the excitation path of the excitation coil, which causes the voltage drop to be shared on the redundant circuit, consumes power, and generates excess heat; at the same time, it increases the instability of the circuit

If the voltage drop is too large, the power consumption will be large, and the heat generated will be large, which will cause the excitation control system to heat up seriously.

(3) The high-voltage side of the H-bridge uses a current-controlled device, which has a large voltage drop, consumes a lot of power, and generates serious heat.

However, the power consumption is large and the heat generation is serious, which restricts the long-term stable and reliable operation of the electromagnetic flowmeter.

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