Power Tool Braking With Energy Feedback and Brake Chopper Control

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Solution Overview

Problem

Existing power tool braking methods, such as short-circuit braking, brake chopper use, and recuperation, face issues of user protection, tool compactness, and efficient energy feedback, with potential damage to electronics and increased complexity or weight.

Innovation Solution

A method for braking a power tool that regeneratively brakes the motor, feeds back electrical energy to the power supply or DC link, and uses a brake chopper only when excess energy exceeds limit values, optimizing power loss and avoiding separate controllers.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If short-circuit braking is used, then braking torque is generated to slow down the power tool, but the electronics must withstand high initial short-circuit currents which can cause damage

Engineering Contradiction:

Improvebraking speedVSAvoidelectronics reliability

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The brake chopper is activated before the full short-circuit current develops to preemptively limit the current magnitude. By switching on the braking resistor in advance, the system prevents the dangerous current spike from occurring, thereby protecting the electronics while still achieving effective braking.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The brake chopper acts as an intermediary component between the motor and the power supply device. It introduces a controlled resistance path that mediates the energy dissipation process, allowing the system to achieve braking torque without subjecting the electronics to damaging current levels.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of operation

If a brake chopper is used as a braking resistor, then controlled braking is achieved, but additional hardware parts increase weight and volume

Engineering Contradiction:

Improvebraking controlVSAvoidpower tool weight

Core Design Contradiction:

Ease of operationVSWeight of moving object

Solution Approach 1:

The brake chopper is designed to serve multiple functions: it provides controlled braking, protects the power supply device from overcurrent damage, and enables energy feedback to the battery. By consolidating these functions into a single component, the system achieves better braking control without proportionally increasing weight and volume.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Loss of energy

If recuperation is used to feed back energy, then energy efficiency improves, but the power supply device may be damaged by excessive braking current

Engineering Contradiction:

Improveenergy feedback efficiencyVSAvoidpower supply device reliability

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The control system continuously monitors the braking current and power supply device status, dynamically adjusting the brake chopper activation timing and duration. This feedback mechanism ensures that energy is fed back to the battery efficiently while preventing current levels that would damage the power supply device.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The braking system operates dynamically by adjusting the brake chopper duty cycle based on real-time conditions. During recuperation, the system modulates the braking resistance to match the power supply device's current acceptance capability, thereby protecting the device while maximizing energy recovery.

Inventive Principle:

Principle #15Dynamics

4Power

If brake chopper is designed for high pulse powers, then braking capability improves, but costs and installation space increase

Engineering Contradiction:

Improvebraking powerVSAvoidinstallation space

Core Design Contradiction:

PowerVSArea of stationary object

Solution Approach 1:

Instead of designing the brake chopper for maximum continuous high power, the system uses partial action by activating the brake chopper only during specific braking phases when high pulse power is needed. This allows the use of a smaller, more compact brake chopper that suffices for intermittent high-power demands rather than requiring oversized components for continuous operation.

Inventive Principle:

Principle #16Partial or excessive action

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

Enables efficient energy feedback, protects users with short braking times, and maintains a compact power tool design by effectively managing excess energy through a brake chopper, preventing damage to electronics.

Implementation Method 1

the brake chopper being configured to connect a resistor to the DC link to thereby turn the energy in the braking resistor into heat

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Implementation Method 2

The motor of the power tool can be braked in a controlled manner during recuperation and thus become the generator. The energy delivered can be fed back to the DC link and transferred from there to the power supply devices.

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentUS20250379533A1Method for braking a power tool, and power tool

Publication Date: 2025.12.11 HILTI AG

AI summary

A method for braking a power tool (10) is provided, the power tool (10) being a battery-operated or mains-operated power tool and including a brake chopper, and at least pert of the electrical energy that is released when the power tool (10) is braked being fed back to a power supply device (14) or a DC link of the power tool (10).