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Building a MOSFET H-Bridge: Essential Guide for Motor Control Projects

Building a MOSFET H-Bridge: Essential Guide for Motor Control Projects

February 08, 2025

Creating an H-bridge using MOSFETs is a fundamental skill in electronics, especially for motor control applications. As a leading MOSFET supplier and authorized semiconductor distributor, we’ll walk you through the process of building an efficient H-bridge circuit using quality components.

What Makes MOSFET H-Bridges Special?

MOSFET H-BridgesH-bridges are essential circuits that enable bidirectional control of DC motors. While there are various ways to construct an H-bridge, MOSFETs offer several advantages:

  • Higher efficiency with lower heat generation
  • Fast switching capabilities
  • Minimal voltage drop across the switches
  • Suitable for high-current applications

Required Components

Component Quantity Specifications
N-channel MOSFETs 4 WSF3036(A) or similar 30V/36A
Gate Drivers 2 Dual channel, bootstrap capable
Bypass Capacitors 4 100nF ceramic
Bootstrap Capacitors 2 100nF/50V

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Step-by-Step H-Bridge Construction

1. Circuit Layout Planning

H-bridge-layoutThe H-bridge layout is crucial for optimal performance. Position the MOSFETs in an H configuration with:

  • High-side MOSFETs (Q1 & Q3) at the top
  • Low-side MOSFETs (Q2 & Q4) at the bottom
  • Motor connections between the pairs
  • Keep gate driver traces short to minimize inductance

2. MOSFET Selection Guidelines

When selecting MOSFETs for your H-bridge, consider these crucial parameters:

VDS Rating:Should be at least 20% higher than your maximum supply voltage

Current Rating:Choose MOSFETs with ID rating 50% above your maximum motor current

RDS(on):Lower RDS(on) means better efficiency but higher cost

Gate Charge:Lower Qg enables faster switching frequencies

Recommended WINSOK MOSFETs for H-Bridge Applications
WSF3036(A)
  • VDS: 30V
  • ID: 36A
  • RDS(on): 9.5mΩ
  • Package: TO-252-2L
WSF40N06
  • VDS: 60V
  • ID: 50A
  • RDS(on): 12mΩ
  • Package: TO-252-2L

3. Gate Driver Implementation

Proper gate driving is essential for efficient MOSFET switching:

Key Considerations:
  • Use dedicated gate driver ICs for reliable switching
  • Implement bootstrap circuits for high-side MOSFETs
  • Add gate resistors (10-100Ω) to control switching speed
  • Include pull-down resistors (10kΩ) on gate inputs

4. Protection Mechanisms

Overcurrent Protection

Implement current sensing with shunt resistors and comparators

Thermal Protection

Add thermal sensors near MOSFETs

Dead-time Control

Ensure adequate dead-time (typically 1-2μs) between switching transitions

Flyback Diodes

Use fast recovery diodes or rely on MOSFET body diodes with proper rating

Common Issues and Solutions

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Overheating MOSFETs

Causes:

  • Insufficient heat sinking
  • High switching losses
  • Poor PCB thermal design

Solutions:

  • Add proper heatsinks
  • Optimize switching frequency
  • Improve PCB thermal vias

Shoot-through Current

Causes:

  • Insufficient dead-time
  • Poor gate driver timing
  • EMI issues

Solutions:

  • Increase dead-time
  • Improve layout
  • Add snubber circuits

Need Professional Assistance?

MOSFET distributorAs an authorized MOSFET distributor, Olukey provides:

  • Technical consultation for your H-bridge design
  • High-quality WINSOK MOSFETs with guaranteed specifications
  • Sample availability for testing and validation
  • Volume pricing for production quantities

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