Core power device for robotics – three major core application scenarios

(Primary Application Market for MOSFETs)

(24V/48V battery pack)

(The robot's "last centimeter")

Humanoid Robot Market Size and Leading Manufacturers

Application Domains and Leading Manufacturers

WORK REPOET

WORK REPOET

To reduce conduction loss (improve efficiency), a low on‑resistance is required. However, devices with low Rds(on) usually feature high gate charge (Qg) and parasitic capacitances (Ciss, Coss, Crss), which slows down the switching speed and increases switching loss. Under high‑frequency PWM control in robots (tens to hundreds of kHz), switching loss becomes quite prominent.

Impact on robots: Reduced system efficiency causes severe heat generation, limiting power density and battery life. At high frequencies, switching loss may even exceed conduction loss and become the primary heat source.

In a bridge circuit (e.g., a three-phase full-bridge circuit), the MOSFET's body diode acts as a freewheeling diode during the dead-time period. However, this diode exhibits a large reverse recovery charge (Qrr), a long reverse recovery time (trr), and a "hard" reverse recovery characteristic.

Impact on robots:

• This generates significant peak current and voltage oscillations, which cause severe electromagnetic interference and compromise the stability of the control system.

• Increases switching losses and, in extreme cases, may pose a "short-circuit" risk, potentially burning out the components.

• This limits the increase in switching frequency, thereby affecting the response speed and control accuracy of the current loop.

Insufficient driving capability can result in slow switching transitions and increased power loss; excessive driving overshoot may cause gate oscillation and EMI issues.

Impact on robots:

• Switching waveform distortion leads to inaccurate control and motor torque pulsation.

• Excessive EMI levels require resolution through complex filtering and shielding techniques, which increases both cost and device size.

• High requirements are placed on the driving chip's peak current, negative-voltage shutdown capability, and protection functions (e.g., saturation release detection).

MOSFETs are subjected to both high voltage and large current at the instant of switching. Device failure is highly likely if the operating point exceeds its Safe Operating Area (SOA). This is especially true under dynamic operating conditions of robots such as emergency stop, motor stall and abrupt load changes.

Impact on robots: Device burnout is one of the most common failures of servo drivers. Insufficient robustness limits robot applications in scenarios with high overload and high‑dynamic‑performance requirements.

The robotic joint space is extremely limited, necessitating highly integrated and compact actuators (high power density); however, all energy losses ultimately convert into heat, which must be dissipated within the confined space.

Impact on robots:

• The use of high-performance heat sinks or liquid cooling increases cost and structural complexity.

• An excessively high junction temperature (Tj) can increase Rds(on), create positive feedback, accelerate thermal failure, and reduce long-term reliability.

The parasitic inductance in the PCB layout and the parasitic capacitance of the MOSFET can form an LC resonant circuit. Under high-frequency switching conditions, severe oscillations may occur in the drain voltage (Vds) and the gate voltage (Vgs).

Impact on robots:

Overvoltage breakdown of the MOSFET; unintended conduction, leading to a direct short circuit between the upper and lower transistors; measurement signal distortion, which affects the accuracy of current sampling.

Multiple MOSFETs are often connected in parallel to meet high‑current requirements. However, current cannot be evenly distributed due to device‑parameter dispersion, such as Vgs(th) and Rds(on).

Impact on robots: Individual devices may bear excess current and fail prematurely from local overheating, triggering a cascading failure effect. Careful component selection and matching are required, which raises costs and process complexity.

The robotics industry—particularly the consumer and collaborative robotics segments—is highly cost-sensitive. MOSFETs capable of meeting the aforementioned high-performance and high-reliability requirements (e.g., those offered by leading international manufacturers such as Infineon and TI) are expensive.

Impact on robots:A challenging trade-off between performance and cost sometimes requires sacrificing certain performance metrics.