Power amplifiers are often subjected to high voltages, large currents, fast switching, and reactive loads. These operating conditions can introduce electrical stress that leads to instability, reduced performance, or even device failure if not managed properly. Because of this, incorporating protection features into the design is essential for reliable operation in real-world applications.
One protection technique is under-voltage lockout (UVLO). UVLO prevents the amplifier from operating when the supply voltage is below a defined threshold, where internal circuitry may not behave predictably. By forcing the device into a known safe state during power-up, brownout, or transient conditions, UVLO helps avoid partial switching, excess power dissipation, and unnecessary stress on the output stage.
A key challenge in switching amplifiers is preventing unintended turn-on during high dv/dt transitions. In a typical half-bridge configuration, the output devices do not switch on and off at exactly the same time. When one device turns off and the other turns on, the rapid voltage change can couple through the parasitic drain-gate (Miller) capacitance of the off device. This Miller current can raise the gate voltage above its threshold and unintentionally turn the device back on, creating a shoot-through condition that can damage the amplifier.
Figure 1: Before and After Active Miller Clamping
Active Miller clamping addresses this by holding the gate of the off transistor low during switching events. As shown in Figure 1, the clamp provides a low-impedance path that prevents the gate voltage from rising due to Miller current. The clamp engages when the device is turned off and remains active until it is commanded back on. This results in more controlled switching behavior, fewer false turn-on events, and improved reliability in high-speed and high-voltage operation.
Apex Microtechnology power modules integrate these key protection features such as UVLO and active Miller clamping directly into the design, reducing the need for external circuitry and simplifying system implementation. The MSA303, the newest addition to our Integrated Power Module family, extends this approach by incorporating Silicon Carbide Schottky Barrier free-wheeling diodes in parallel with the body diode of each MOSFET. This eliminates the need for external output protection diodes while improving efficiency and robustness, enabling a more compact and reliable solution.
600V, 40A SiC 3-Phase Integrated Power Module
3 Fully Independent Half-bridges Integrated Gate Driver
Compact Design - 30mm x 42mm
Body Size
Under-voltage lockout (UVLO)
Active Miller Clamping
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