Stacked Overvoltage Battery Protector Reference Design

The design ensures voltage monitoring, helps integration with numerous displays, and gives safety by way of fuse-blowing mechanisms for security.

Secondary-level protectors are actually required for 48V-60V battery techniques in industrial functions. The TIDA-00108 reference design from Texas Devices (TI) presents a strong stacked structure that ensures high-accuracy voltage detection for 10s-15s sequence rechargeable cells. Throughout the bq7718xy household, every cell is monitored independently, that includes an embedded delay timer to stop false tripping of inline fuses. The design applies to varied industries, together with energy instruments, storage battery safety, and digital automobile (EV) bikes.

The answer operates independently of current monitoring Analog Entrance-Finish (AFE) and cell-balancing techniques, providing seamless integration with 5-, 10-, and 15-series (S) displays and protectors. It gives exact digital management of an correct self-controlled inline present fuse. A key function is the one-time fuse blow mechanism, which completely disables the circuit, isolating the pack and rendering it inoperable for enhanced security and safety.

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The secondary stack system reference design consists of three key useful blocks. First, the cell enter filters and safety community are outlined in line with the bq7718 gadget specs. These filters guarantee correct voltage and present administration on the enter stage. Second, the design incorporates three bq771xx units organized in a stacked 3-S configuration, combining particular person output indicators in a logic OR utilizing an analogue scheme. This serial association helps voltage translation from floor as much as 60V. Lastly, the inline fuse blowing mechanism is electronically managed by an NMOS FET linked to a self-protecting fuse, making certain secure disconnection when vital.

The cell banks are emulated in laboratory testing utilizing a cell financial institution simulator. The simulator routes cell voltages by way of a low-pass filter community designed per the gadget specs, which additionally limits the differential present into the bq7718 gadget. The bq7718 sequence independently displays every cell, with an embedded delay timer that stops untimely triggering. 

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The gate voltage of the NMOS FET is calculated to vary between 3V and 10V. When activated, the FET pulls the fuse to blow open by way of the heater resistance of the self-controlled, state-of-the-art fuse, making certain dependable safety. This unit is programmed to use hundreds starting from 3A to 30A, enabling thorough PCB efficiency testing beneath various situations.

Key circuit parameters, together with the conventional working present throughout each charging and discharging, the utmost fault voltage, and the secondary safety circuit’s response time to an overvoltage situation, information the choice of the gadget specification. Based mostly on the system’s overvoltage safety (OVP) threshold, output delay timer, and output drive necessities, the secondary safety gadget will be chosen for the design.

TI has examined this reference design. It comes with a invoice of supplies (BOM), schematics, meeting drawing, printed circuit board (PCB) structure, and extra. The corporate’s web site has extra information in regards to the reference design. To learn extra about this reference design, click on right here.