A control circuit capable of achieving rapid commutation of an electromagnet.
Release time:
2020-07-30
An electromagnet is an electrical device that uses the electromagnetic attraction generated by a current-carrying coil wrapped around an iron core to actuate mechanical components and perform desired motions. It is an electromagnetic component that converts electrical energy into mechanical energy. Due to its simplicity of control, operational stability, and reliability, it is widely used in switching mechanisms found in office automation (OA) products and financial electronic devices. However, with ongoing advances in technology, there are ever-increasing demands on product operating speeds. The conventional electromagnet control circuit, however, imposes limitations on the response speed of electromagnets [1], thereby hindering further improvements in product performance. This paper, taking the channel-switching mechanism in OA products as an example, analyzes the shortcomings of the traditional electromagnet control circuit and introduces a novel control circuit based on improvements to the conventional design, enabling rapid electromagnet switching. Analysis of the Shortcomings of the Traditional Electromagnet Control Circuit In typical electromagnet switching mechanisms used in OA product conveyor channels, the working principle involves using a linear electromagnet to switch the channel direction between two positions via a switching block. The traditional control circuit for the electromagnet is shown in Figure 2. It employs a single MOSFET, V1, to drive the electromagnet. When the input signal ON_OFF is high, the D and S terminals of V1 become conductive, allowing the DC36V power supply to energize the electromagnet, thus connecting the channel to direction 1. Conversely, when the input signal ON_OFF is low, V1 turns off its output, and under the action of the return spring, the electromagnet reverts to channel direction 2. In the figure, V2 is a freewheeling diode that clamps and provides continuous current flow across the electromagnet’s terminals after V1 turns off its output. Its primary function is to prevent damage to the MOSFET V1 and other components of the power supply. F1 is a fuse that provides short-circuit protection. The aforementioned traditional control circuit has the following drawbacks: slow switching speed. The reason is that after V1 turns off its output, the magnetic energy stored in the electromagnet is converted into electrical energy and slowly dissipated through the freewheeling diode V2. During this dissipation process, a residual current flows in the circuit, giving the electromagnet a certain holding force, which prevents it from quickly returning to its original position under the action of the return spring.
An electromagnet is an electrical device that uses the electromagnetic attraction generated by a current-carrying coil with an iron core to actuate mechanical devices and perform desired actions. It is an electromagnetic component that converts electrical energy into mechanical energy. Due to its simplicity of control, operational stability, and reliability, electromagnets are widely used in switching mechanisms for office automation (OA) products and financial electronic equipment. However, technological advancements continually place new demands on product operating speeds. The conventional electromagnet control circuit, with its inherent limitations, restricts the response speed of electromagnets [1], thereby hindering further improvements in product operating speed. This paper, taking the channel-switching mechanism in OA products as an example, analyzes the shortcomings of traditional electromagnet control circuits and introduces a novel control circuit that builds upon the conventional design to achieve rapid electromagnet switching.
Analysis of the Disadvantages of Traditional Electromagnetic Controlling Circuits
The reversing mechanism for solenoids commonly used in the conveying channels of OA products operates on the principle of using a linear solenoid to switch the channel direction in two opposite directions. The conventional control circuit for the solenoid is shown in Figure 2. A single MOS transistor V1 drives the solenoid: when the input signal ON_OFF is high, the drain (D) and source (S) terminals of V1 become conductive, allowing the 36V DC power supply to energize the solenoid, thereby connecting the channel in direction 1. Conversely, when the input signal ON_OFF is low, V1 turns off its output, and under the action of the return spring, the solenoid returns to channel direction 2. In the figure, V2 is a freewheeling diode that clamps and provides a path for the reverse voltage across the solenoid after V1 turns off its output. Its primary function is to prevent damage to the MOS transistor V1 and other components of the power supply. F1 is a fuse that provides short-circuit protection. The aforementioned conventional control circuit has the following drawbacks: slow switching speed. This is because, after V1 turns off its output, the magnetic energy stored in the solenoid is converted into electrical energy and slowly dissipated through the freewheeling diode V2. During this dissipation process, the resulting loop current exerts a certain holding force on the solenoid, preventing it from quickly returning to its original position and switching directions under the action of the return spring.
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