Power Tool Intermediate Circuit Precharge for Capacitor Offset Voltage
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Solution Overview
Problem
Existing power tools with intermediate circuits fail to optimize the charging behavior of additional capacitors, leading to inefficient energy storage and supply, particularly in maintaining a stable auxiliary voltage.
Innovation Solution
Incorporating a precharge circuit within the intermediate circuit to set an offset voltage for the additional capacitor, allowing for optimal charging behavior by regulating the offset voltage based on mains voltage characteristics, and using a precharge circuit connected in parallel with the additional capacitor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the additional capacitor is used to store energy in the intermediate circuit, then the energy storage capacity increases, but the capacitor voltage may exceed the maximum voltage rating of the capacitor
Solution Approach 1:
The precharge circuit charges the additional capacitor to an offset voltage before the main charging operation. This preliminary action ensures that the capacitor starts from a controlled initial state, preventing the voltage from exceeding the maximum rating during subsequent charging while still allowing sufficient energy storage capacity.
2Reliability
If the offset voltage of the additional capacitor is increased, then the auxiliary voltage supply capability improves, but the energy storage capacity decreases
Solution Approach 1:
The precharge circuit adjusts the offset voltage parameter to an optimal value that balances the auxiliary voltage supply capability and energy storage capacity. By controlling the precharge voltage level, the system achieves sufficient auxiliary supply while maintaining adequate energy storage for transient requirements.
3Quantity of substance
If the additional capacitor is charged to maximum capacity, then the energy availability increases, but the charging time and transient response performance deteriorate
Solution Approach 1:
The precharge circuit performs a preliminary charging operation that brings the capacitor to an optimal initial voltage state. This preliminary action reduces the subsequent charging time required to reach full energy availability, improving transient response performance while maintaining sufficient energy capacity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Ensures sufficient energy storage and supply to the auxiliary voltage, enabling efficient operation of the power tool by optimizing the initial state of charge and voltage levels, allowing for the use of capacitors with different voltage ratings and reducing the size of the additional capacitor.
Implementation Method 1
the intermediate circuit has a precharge circuit (40) which is or can be used to set an offset voltage of the additional capacitor (35)
Implementation Method 2
the switching branch has an additional capacitor (35) which can be discharged if necessary via a discharge circuit (37) included in the intermediate circuit (30) by means of a switching element (34) included in the switching branch (33)
Data Source
AI summary
A mains-operable power tool having a mains connection, a rectifier connected downstream of the mains connection, and an electric motor with an upstream motor stage, wherein the rectifier and the motor stage are connected via an intermediate circuit having a smoothing capacitor connected in parallel with the rectifier and a switching branch connected in parallel with the rectifier, wherein the switching branch has an additional capacitor which can be discharged if necessary via a discharge circuit included in the intermediate circuit by a switching element included in the switching branch, wherein the intermediate circuit has a precharge circuit which is or can be used to set an offset voltage of the additional capacitor.