This application note introduces Hall Effect linear current sensor integrated circuits that are capable of enabling high bandwidth sensing in hybrid electric vehicles and other high current sensing applications. It provides a functional description of analog signal path and bandwidth, packaging, digital temperature compensation and core design, and the A1366 accuracy such as the sensitivity and QVO.
A new linear current Hall-effect sensor IC has been developed to accommodate the accuracy and bandwidth requirements of hybrid electric vehicle (HEV) inverter current sensing applications. The device uses a proprietary SIP package, and it employs next-generation chopper stabilization signal conditioning and filtering circuitry that combine to provide a low-noise, analog output signal at up to 120 kHz bandwidth. Industry leading accuracy levels are made possible by the introduction of proprietary, piecewise, linear temperature compensation that stabilizes the zero field offset and output sensitivity over the full operating temperature range without impacting the high bandwidth signal path. The device is ideal for all current sensing applications using a core configuration that require high frequency operation. The HEV inverter application is used as an example in this paper.
A full bridge driver in a typical HEV inverter converts DC battery voltage to 3-phase AC voltage to drive an AC motor connected to the drive train (see Figure 1).
The inverter phase currents are measured, and the resulting information is used to control the pulse-width modulated (PWM) inverter switches (typically IGBTs). The inverter control loop requires high bandwidth current sensor ICs with high accuracy in order to maximize motor torque and overall motor efficiency. High side current sensor ICs with fast response times also enable over-current protection. The Allegro™ A1366 linear Hall-effect sensor IC has been designed to meet the high bandwidth, high accuracy requirements of HEV inverter applications. In these applications, the linear Hall-effect sensor IC is typically placed in the gap of a ferromagnetic “C” core, which surrounds each inverter phase conductor in the motor (see Figure 2). As current flows in the conductor, the core concentrates the resulting magnetic field through the single inline package (SIP).
Allegro’s proprietary design features make the A1366 an ideal sensor IC for use in HEV inverters, high current motor control, or any other high frequency, high current applications. These features include special packaging, advanced chopper and filtering techniques, and a digital temperature compensation algorithm. These innovations make possible an industry leading, high accuracy, 120 kHz bandwidth linear Hall-effect sensor IC that performs well in HEV current sensor applications.
This paper will focus on the next-generation package, as well as on the IC design innovations and their influences on sensor IC performance. It will also include a brief application discussion on core design.