What is Motor Driver Power Dissipation?

In power electronics, specifically motor control, power dissipation refers to the energy lost as heat within the driver integrated circuit (IC) or discrete MOSFETs. This heat is primarily generated by two phenomena: conduction losses and switching losses. If this heat is not properly managed, it can lead to thermal shutdown or permanent damage to the motor driver.

How to Calculate Driver Heat

This calculator uses the standard physics models for H-bridge motor drivers. Conduction Loss occurs because every MOSFET has a small internal resistance called RDS(on). When current flows through the motor, it flows through two MOSFETs in an H-bridge path. The formula used is P = I² × RDS(on) × 2.

Switching Loss occurs during the brief moments when the MOSFET transitions between the ON and OFF states. During this time, the transistor passes through its linear region where both voltage and current are present simultaneously. This loss is proportional to the PWM frequency, the supply voltage, and the speed of the switching (rise and fall times).

Why It Matters for Your Project

Knowing the total wattage helps you determine if your motor driver requires a heat sink, forced air cooling, or a larger PCB copper pour for thermal dissipation. High PWM frequencies result in smoother motor operation but increase switching losses significantly. By balancing frequency and thermal capacity, engineers can optimize for efficiency and longevity.

FAQs

How can I reduce heat? You can reduce heat by using a driver with lower RDS(on), reducing the PWM frequency, or lowering the motor current if the torque requirements allow it.

What is a safe temperature? Most motor driver ICs are rated for a junction temperature up to 150°C, but for reliability, it is best to keep the package temperature below 85°C to 100°C.