Ignition Control Circuit for Power Tools
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Solution Overview
Problem
Existing ignition arrangements for semiconductor circuits, particularly TRIACs, in electric power tools face issues with unreliable restart protection and reduced efficiency due to delayed ignition and power factor losses, especially in small power tools.
Innovation Solution
A monitoring arrangement that generates an ignition pulse independently of the electrical voltage at a connection point of the semiconductor circuit, using controlled switches and a voltage or current source, allowing for earlier ignition and improved power factor by adapting to the specific circuit structure and voltage requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a DIAC-TRIAC circuit with resistance network is used for phase control, then the power consumption of the electric motor can be regulated, but the ignition is delayed and power factor losses occur
Solution Approach 1:
A capacitor is introduced as an intermediary energy storage element that accumulates energy during the AC cycle and releases it at the optimal moment to trigger the TRIAC. This mediator enables earlier ignition without requiring continuous resistance network adjustment, thereby reducing power factor losses while maintaining power regulation capability.
Solution Approach 2:
The invention changes the operating parameters by using a capacitor-based ignition system instead of resistance-based phase control. This parameter change allows the TRIAC to be triggered at an earlier point in the AC cycle, improving the power factor while still enabling power consumption regulation through other means.
2Ease of operation
If the manually operable mains switch can be locked in the on position, then convenient operation is achieved, but unintentional start-up risk increases
Solution Approach 1:
A monitoring arrangement continuously monitors the switch position and provides feedback to a control circuit. This feedback mechanism enables the system to detect when the switch is in the ON position and prevent ignition accordingly, maintaining operational convenience while eliminating unintentional start-up risks through intelligent control.
Solution Approach 2:
The system performs preliminary monitoring of the switch position before allowing ignition to occur. By checking the switch state in advance and preventing ignition when inappropriate conditions exist, the system ensures safe operation while maintaining user convenience throughout the device's operation.
3Reliability
If restart protection is implemented to prevent unintentional start-up, then safety is improved, but device complexity increases
Solution Approach 1:
The restart protection function is merged with the existing ignition control circuitry for the TRIAC. By combining these functions into a single integrated control system, the patent achieves reliable restart protection without proportionally increasing device complexity, as the same monitoring and control resources serve dual purposes.
Solution Approach 2:
The control circuit is designed with multi-functionality, serving both the ignition control of the TRIAC and the restart protection functions. This universal approach allows a single circuit to perform multiple safety and control tasks, reducing overall device complexity while maintaining comprehensive protection capabilities.
4Loss of energy
If a monitoring arrangement with independent voltage or current source is used, then earlier ignition and improved power factor are achieved, but device complexity increases
Solution Approach 1:
The monitoring arrangement utilizes the existing AC voltage or current in the circuit as its own power source, eliminating the need for separate power supply components. This self-service approach enables the monitoring system to operate using readily available circuit energy, achieving earlier ignition and improved power factor without adding significant complexity through external power sources.
Data Source
Figure 1~2
AI summary
Circuit arrangement (2) for controlling an ignitable semiconductor circuit (1) with an ignition control input (3) to control the power consumption of an electrical load (M), in particular an electric motor in a power tool. A monitoring arrangement (4) is provided to monitor an electrical voltage at a connection point (A1) of the ignitable semiconductor circuit (1) and/or at a connection point (AM) of the electrical load (M) and to generate an ignition pulse at the ignition control input (3) of the ignitable semiconductor circuit (1), wherein a voltage source or current source (5) independent of the monitored electrical voltage is provided for generating the ignition pulse.