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Keep Hybrid Powertrain Drives Noise Free By Rejecting dV/dt Noise With Isolated-Gate Drivers

2nd July 2013
ES Admin
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High common-mode noise is a significant problem that automotive system designers must overcome when designing a practical and reliable powertrain drive system. Common-mode noise (also known as dV/dt noise) is generated naturally within a system when there is high-frequency switching in the high-voltage power inverters and other power supplies. This article will discuss the various sources of dV/dt noise in a hybrid powertrain drive and suggest several approaches to minimize the effects of the noise on the drive electronics.
Sources And Effects Of Powertrain Drive Common-Mode Noise

In a typical hybrid powertrain drive subsystem, there are High-side and Low-side portions of the motor drive subsystem, with each side providing three phases of high current to power the motor. When the gate drivers switch the High-side and Low-side IGBTs in sequence, high dV/dt noise is generated. For example, a typical powertrain that is connected to a high-voltage (400V DC) supply with the switching rise and fall time of 50ns, will generate a dV/dt noise of 400V/50ns, or ~ 8kV/μs whenever the gate-driver switches.

If a short-circuit condition should occur due to some faults, additional overshoot voltage (v=L*di/dt) will add on to the DC rail voltage due to a large short-circuit current transient, di/dt, that fl ows through the circuit stray inductance, L. The gate-driver circuits must be capable of handling this additional dV/dt noise so they can maintain control and execute the correct protection protocol. Additionally, the requirements for higher DC-rail supply voltages to power larger hybrid vehicles, such as trucks and buses, and faster switching frequencies to reduce conduction loss are all leading to increasing the system requirement to incorporate higher dV/dt noise rejection. Today, hybrid powertrain drive circuits with a dV/dt noise rejection of 15kV/μs are employed to maintain overall system performance, reliability and robustness. Download the full White Paper below.

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