Single-Phase AC Chopping Circuit Without Rectifier Bridge
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Solution Overview
Problem
Existing single-phase AC motor driving circuits face limitations in stepless speed regulation, efficiency, power factor, and complexity, particularly due to the need for rectifying bridges and large capacitors, which increase cost and complexity while reducing efficiency and power factor.
Innovation Solution
An AC chopping circuit that directly chops AC power without a rectifying bridge, using a switching circuit, synchronizing signal generating circuit, switch driving circuit, and auxiliary power supplying circuit to control the switching of transistors based on AC power polarity, eliminating the need for rectifying bridges and reducing component count and complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a rectifying bridge is used in the AC motor driving circuit, then the circuit can provide stable DC power, but the device complexity and cost increase
Solution Approach 1:
The patent removes the rectifying bridge from the traditional AC motor driving circuit, extracting this component to simplify the overall circuit structure. The AC chopping circuit directly processes AC power without requiring conversion to DC, thereby reducing device complexity and cost while maintaining reliable operation through synchronized switching control
Solution Approach 2:
The AC chopping circuit performs multiple functions: it directly chops AC power to control motor speed, provides stepless speed regulation, and maintains power factor correction capabilities. This multi-functional approach replaces the traditional rectifying bridge-based DC conversion system, reducing overall circuit complexity while maintaining stable power supply to the motor
2Reliability
If a rectifying bridge and large capacitor are used, then the power supply is stable, but the efficiency and power factor decrease
Solution Approach 1:
The patent employs periodic AC chopping control where the switching circuit operates in synchronization with the AC power source cycles. The synchronizing signal generating circuit detects AC polarity and generates periodic control signals that switch the power transistor on and off during each AC cycle, enabling stepless speed regulation while maintaining power factor and reducing energy losses associated with traditional rectifying bridges and large capacitors
3Reliability
If a rectifying bridge and large capacitor are used, then the power supply is stable, but the cost increases
Solution Approach 1:
The patent extracts and removes the rectifying bridge and large capacitor from the traditional circuit configuration. By directly chopping AC power using the switching circuit synchronized with the AC source, the design eliminates expensive components while maintaining stable motor operation through precise timing control based on AC polarity detection
4Manufacturing precision
If stepless speed regulation is implemented, then the motor control precision improves, but the device complexity increases
Solution Approach 1:
The synchronizing signal generating circuit provides feedback by detecting the AC power source polarity and generating corresponding control signals. This feedback mechanism enables the switching circuit to achieve stepless speed regulation by adjusting the duty cycle in real-time synchronization with the AC cycles, maintaining precise motor control while keeping the circuit relatively simple through intelligent control rather than complex hardware
Data Source
AI summary
According to some embodiments, AC chopping circuit includes a switching circuit, a synchronizing signal generating circuit, a switch driving circuit and an auxiliary power supplying circuit. In some examples, the switching circuit are coupled to an AC power source and a load. In certain examples, the synchronizing signal generating circuit provides a synchronizing signal which is related to a polarity of the AC power source. In some examples, the switching circuit is controlled based at least in part on the synchronizing signal.