Half Bridge Gate Driver# Technical Documentation: FAN7382 High-Voltage Half-Bridge Gate Driver IC
## 1. Application Scenarios
### Typical Use Cases
The FAN7382 is a monolithic high-voltage, high-speed gate driver IC designed to drive both high-side and low-side N-channel power MOSFETs or IGBTs in a half-bridge configuration. Its primary function is to provide the necessary voltage level shifting, isolation, and drive current to efficiently switch power devices in high-voltage environments.
Key operational use cases include:
- Motor Drive Circuits : Driving three-phase brushless DC (BLDC) motors and permanent magnet synchronous motors (PMSMs) in applications requiring precise speed and torque control.
- Switched-Mode Power Supplies (SMPS) : Used in high-power AC-DC and DC-DC converters, particularly in half-bridge, full-bridge, and resonant LLC topologies.
- Uninterruptible Power Supplies (UPS) : Inverter and converter stages where efficient high-voltage switching is critical for power quality and conversion efficiency.
- Solar Inverters : Driving IGBTs or MOSFETs in the power stage for converting DC from photovoltaic panels to grid-compatible AC.
### Industry Applications
- Industrial Automation : Servo drives, spindle drives, and robotic arm controllers.
- Consumer Electronics : High-end audio amplifiers (class D) and large LCD/plasma TV power supplies.
- Automotive : Electric vehicle (EV) traction inverters, on-board chargers (OBC), and DC-DC converters (in qualified automotive-grade variants).
- Renewable Energy : Wind turbine converters and the aforementioned solar inverters.
- Telecommunications : High-efficiency rectifiers and power modules for base stations.
### Practical Advantages and Limitations
Advantages:
- High Voltage Capability : Bootstrap operation allows the high-side driver to operate with supply voltages up to 600V, suitable for direct off-line applications.
- Integrated Functions : Includes under-voltage lockout (UVLO) for both VCC and VB-VS, preventing malfunction at insufficient supply voltages. A shutdown feature allows for system protection.
- Fast Switching : Typical propagation delay times of 60ns (max) minimize dead time requirements, improving efficiency.
- Robustness : High dv/dt immunity and negative VS swing tolerance enhance reliability in noisy switching environments.
- Compact Solution : Replaces multiple discrete components (level shifters, drivers, isolators), saving board space and improving reliability.
Limitations:
- Bootstrap Limitation : The high-side driver requires a bootstrap capacitor and diode. This limits the maximum duty cycle and on-time for the high-side switch, as the capacitor must be periodically recharged when the low-side switch is on.
- Heat Dissipation : In high-frequency or high-current drive applications, the driver's internal power dissipation can become significant, requiring thermal management.
- No Isolation : While it provides level shifting, the FAN7382 does not provide galvanic isolation between the logic input and the high-voltage output. Isolation must be provided externally if required by safety standards (e.g., reinforced isolation for mains-connected circuits).
- Peak Current : While capable of sourcing/sinking several amperes peak, driving very large MOSFET/IGBT modules with extremely high gate charge (Qg) may require an additional pre-driver stage.
## 2. Design Considerations
### Common Design Pitfalls and Solutions
1. Pitfall: Bootstrap Circuit Failure
* Problem : Inadequate bootstrap capacitor (Cboot) sizing or a slow/inefficient bootstrap diode (Dboot) leads to insufficient voltage on the high-side supply (VB), causing poor high-side switch turn-on or UVLO faults.
* Solution : Calculate Cboot based on the gate charge (Qg) of the high-side MOSFET, the allowable VB droop, and
