Invented by Nagel; Gerald M., Brnot; Nicholas, DeClerck; Michael, Kovnar; Sam, Bothe; Erik P.

Power tools are getting smarter, stronger, and safer every year. One new idea is making these tools even better by handling the way energy moves inside them. In this article, we will explore an exciting new patent application that shows how to control the flow of current in brushless motors used in power tools. We will break it down into simple parts for everyone to understand.

Background and Market Context

Power tools are everywhere. People use them for building houses, fixing cars, cutting wood, and many other jobs. Today, most high-end power tools use brushless direct current (BLDC) motors. These motors are popular because they last longer, use less energy, and can pack a lot of power in a small space. They also do not have brushes that wear out, so they need less fixing over time.

But even these advanced motors are not perfect. When you use a power tool, the motor inside turns on and off in steps. Every time the motor changes from one step to the next, a quick burst of energy, called a “transient current,” can bounce back into the battery. If this happens too often, it can make the tool act strange, cause the battery to wear out faster, and sometimes even make the tool pause or stop for a short moment.

For tool makers, this is a big deal. Everyone wants tools that work smoothly, run longer on a charge, and do not break down. If a company can solve these little problems, it will sell more tools and keep customers happy. This is why inventors and engineers work hard to find new ways to control what happens inside the motor, especially when switching from one phase to the next.

Over the past few years, battery technology and electronics have made big jumps forward. Power tools now use better batteries and smart controllers that can watch what is happening in real time and make quick adjustments. The market is full of brands competing on who can make the best, most reliable, and most user-friendly tool. This new patent fits right into this race to the top. It tries to fix a small, but important, problem that can make a huge difference in how well a power tool works and how long it lasts.

If this idea works as planned, people who use these tools will notice smoother operation, fewer pauses or stutters, and maybe even longer battery life. For professionals and anyone who uses power tools every day, this can mean more work done and less time fixing broken tools.

Scientific Rationale and Prior Art

To understand the new invention, we need to know a bit about how BLDC motors work. In these motors, you have several “phases.” Think of them like three different pipes carrying water. At any moment, some pipes are open, letting water flow, while others are closed. The motor controller decides which pipes to open and close, and in which order, to keep the motor spinning.

Inside each phase, there are coils of wire. When the controller sends current through a coil, it creates a magnetic field that pushes or pulls the spinning part of the motor, called the rotor. The controller uses special switches (often called “high-side” and “low-side” switches) to let current flow through these coils. By turning these switches on and off in the right order, the motor spins smoothly.

The problem shows up when the controller turns off one phase and quickly turns on the next. The coil that just turned off still has energy stored inside, like water in a pipe that suddenly has nowhere to go. If nothing is done, this leftover energy can rush back into the battery, causing a quick, sharp current in the wrong direction. This is called a negative transient current. Too many of these can make the battery unhappy, cause voltage drops, or mess up the tool’s control system.

In the past, engineers tried a few tricks to fix this. One way is to use bigger capacitors in the battery pack. Capacitors are like small buckets that can soak up those quick bursts of energy. But bigger capacitors take up more space, add weight, and cost more money. Another method is to tweak the way the controller turns the switches on and off. For example, it can leave a switch on a little longer or use a special timing pattern. These tricks help, but they do not solve the problem completely. Some energy still makes it back to the battery, and sometimes the timing change slows down the motor or makes it less precise.

Other inventions tried to add extra parts to the circuit, like special resistors or diodes, to give the extra energy a place to go. While this can work, it also makes the whole tool more complicated and can make it less reliable.

So, the challenge is to find a way to control where that leftover energy goes, without adding more parts, making the tool heavier, or slowing it down. The goal is to keep the motor running smooth, protect the battery, and keep the tool simple and tough.

This is where the new patent stands out. Instead of letting the current bounce back to the battery or making the switches work longer, it uses the existing switches in a smart way to “burn off” the extra energy inside the motor itself. It does this by quickly turning on two switches at just the right moment, letting the energy flow through the motor’s coils and turning it into harmless heat. This simple idea can make a big difference in tool performance and battery life.

Invention Description and Key Innovations

The new patent describes a power tool with three main parts: a brushless motor with several phases, a switching circuit with “high-side” and “low-side” switches, and an electronic controller that tells the switches what to do.

Here is how it works in plain language:

When you pull the trigger on your power tool, the controller starts turning the switches on and off in a special order to make the motor spin. Normally, it does this by sending a signal called Pulse Width Modulation (PWM) to the switches. This signal is like turning a light on and off very fast, and the “duty cycle” is how much of the time the light is on versus off. By changing the duty cycle, the controller can make the motor go faster or slower.

But every time the controller moves from one step to the next, there is leftover energy in the coil that just turned off. If nothing is done, the energy can rush back to the battery, causing all the problems we talked about earlier.

The new idea is for the controller to use the switches in a new way. Right after turning off one phase and before turning on the next, the controller quickly turns on two switches at the same time (for example, two high-side switches). This lets the leftover energy in the coil flow into another coil, where it gets turned into a small amount of heat. The energy does not go back to the battery. The controller does this by sending a special “pulse” with its own duty cycle, usually smaller than the main PWM duty cycle.

The key parts of this invention are:

1. Sequential Energizing and Dissipation: The controller turns on the right switches to make the motor spin (“energizing”), and then, right before switching to the next phase, it turns on a different pair of switches to let the leftover energy “dissipate” safely inside the motor.

2. Smart Use of Switches: Instead of adding new parts, the controller uses the existing high-side and low-side switches in new combinations. For example, after energizing one phase with a high-side and a low-side switch, the controller might briefly turn on two high-side switches or two low-side switches to let the energy flow and get used up.

3. Custom Pulse Signals: The controller sends different pulse signals for spinning the motor and for dissipating energy. The pulse for dissipation can have a different “on time” (duty cycle) than the main PWM signal. This gives fine control over how much energy is burned off and ensures the motor keeps running smoothly.

4. Less Stress on the Battery: By keeping the negative transient currents from reaching the battery, the tool runs smoother, and the battery lasts longer. It also helps the tool’s safety features work better, since the current sensors get more accurate readings.

5. No Extra Parts: The system does not need extra resistors, diodes, or capacitors. It just uses the switches and controller already found in modern brushless power tools, making it easy to add to new designs.

Let’s look at a simple example. Imagine the controller has just finished energizing Phase U and is about to switch to Phase V. Normally, the leftover energy in Phase U could rush back to the battery. With this new method, the controller quickly turns on two high-side switches (for example, UH and VH). This lets the energy in Phase U flow into another path inside the motor, where it is turned into heat. The controller decides how long to keep these switches on, making sure just the right amount of energy is used up.

The patent also includes methods for switching between different combinations of switches, depending on which phases are active. For each step in the six-step commutation sequence (the common way to run a three-phase brushless motor), the controller can decide which switches to use for dissipation. The timing and duty cycle of these dissipation pulses can change, depending on the motor’s speed, how hard you are pressing the trigger, or other factors.

The invention uses current sensors and position sensors (like Hall effect sensors) to keep track of what is happening inside the motor. The controller watches these sensors to decide when and how long to dissipate the energy, making the whole process smart and automatic.

In tests and examples, this new control method shows much smoother current flow from the battery, with fewer drops or spikes during motor commutation. This means less electrical noise, fewer interruptions, and better overall tool performance.

Another important thing is that the method works for both high-capacitance and low-capacitance battery packs. In cheaper or smaller batteries, where this problem is even worse, the new control method makes a big difference.

For tool makers, this invention means they can build smarter, more reliable tools without making them more expensive or complicated. For users, it means tools that work better, last longer, and feel smoother in the hand.

Conclusion

This new patent for controlling energy in brushless power tools is a big step forward. By using the tool’s own switches in a smart way, it keeps leftover energy from bouncing back into the battery. This makes the tool run smoother, helps the battery last longer, and avoids adding extra parts or complexity. The idea is simple, but its impact is huge for users and tool makers alike. As more power tools use brushless motors, inventions like this will help set the best brands apart and make every job easier.

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