Typical applications of MOSFETs in cordless power tools, covering drive architecture, selection parameters, package layout and future trends, provide a reliable reference for industrial customers.
I. Challenge-Oriented Start: Power Loss and Heat in Cordless Tools
With the advancement of lithium-ion battery technology, cordless power tools have become mainstream across construction, maintenance, and home DIY markets. However, their compact high-power designs face two critical challenges: low efficiency in power control and severe thermal management issues.
MOSFETs are key to solving these issues. With low R<sub>DS(on)</sub>, fast switching speed, and flexible packaging, they are widely used in motor drivers, battery protection circuits, and load switches.
II. Application Architecture: How MOSFETs Are Used in Drive Modules
Cordless power tools typically use full-bridge or half-bridge drive topologies, paired with PWM control for variable speed and smooth startup. MOSFETs play essential roles in:
Load Path Switching. Main power switching from battery to motor.
BLDC Motor Commutation. High-speed switching enables efficient commutation for brushless DC motors.
Battery Protection. Protection against reverse polarity and current surges using back-to-back MOSFET pairs.
Designs often select SOP-8, TO-252, or DFN packages for optimal thermal resistance and space efficiency.
III. Why MOSFETs Are Preferred in This Industry
Compared with mechanical relays or bipolar transistors, MOSFETs offer significant technical benefits:
|
Parameters |
Advantages |
|
On-resistance |
Low voltage (as low as a few milliohms), reducing energy consumption and extending battery life. |
|
Switching frequency |
Up to hundreds of kHz, adapting to high-frequency control requirements. |
|
Thermal characteristics |
Supports heatsink and PCB cooling designs. |
|
Voltage rating |
From 20V to 100V, adapting to various power levels. |
|
Stability |
Strong ESD and latch-up immunity, improving overall lifespan. |
IV. Case Study: 18V Cordless Impact Driver MOSFET Application
In the design of a leading brand's 18V cordless impact driver, the engineering team applied the following strategy:
Dual N-channel MOSFETs in a TO-252 package formed a full-bridge driver.
RDS(on) was kept under 8 mΩ to limit heat and power loss.
Thermal pad-equipped packages worked with aluminum heatsinks on PCB for heat dissipation.
On-chip ESD protection improved performance in noisy environments.
V. Future Outlook: Toward Smarter and Denser Systems
Future trends for MOSFET usage in cordless power tools include:
Smart Fault Detection, Integration of GaN/SiC, High-Density Power Modules, MCU-BMS Interoperability.
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