Battery disconnect switch
Semiconductors for compact, heat resistant and reliable cutoff designs
In the unlikely event of an accident or emergency, it’s absolutely crucial for a commercial, construction and agricultural vehicle (CAV) to be able to shut off entirely by itself. That’s why it needs a battery disconnect switch. In particular, this feature is becoming increasingly essential as heavy-duty trucks and other CAVs come equipped with a growing number of autonomous and semi-autonomous driving capabilities.
Safety and security come first
To uphold safety standards, today’s CAVs are equipped with a 24 V vehicle electrical system and a redundant 24 V, in addition to a 12 V supply for the cabin’s comfort features. A key function of the system is the battery disconnect switch. This master cutoff introduces an isolator to ensure the batteries in the 24 V main network are properly separated from the redundant 24 V network. For guaranteed reliability in areas with extreme weather, from excessive cold to sweltering heat, a battery disconnect switch design must withstand and work reliably in a range of harsh conditions and environments.
System diagram: CAV battery disconnect switch
Meeting market demands for master switches
Smaller is better here, as a small battery disconnect switch solution is easier to integrate, costs less and requires less development effort. Ideal dimensions measure just 100 x 50 mm. Battery switch customers also look for designs with various specifications, such as:
- Thickness: 1.3 mm
- Electrical resistance: 60 µOhm
- Thermal resistance (non-isolated version): 0.1 K/W
- Thermal resistance (isolated version): ~ 0.2 K/W
- No. of copper-filled laser vias per MOSFET: 300
- RDS(on) from terminal to terminal: 110 µOhm
Benefit from low on-state resistance: Infineon MOSFETs
Thanks to Infineon’s low ohmic MOSFETs, the on-state resistance of the entire battery disconnect switch is less than 160 uΩ, from terminal to terminal. The eight MOSFETs account for just 67 uΩ at room temperature. At a 120°C board temperature and 500 A current, this increases to roughly 100 uΩ. In terms of architecture, typically the demonstrator consists of eight low ohmic MOSFETs connected in parallel and mounted on a structured copper IMS (insolated metal substrate) board, along with a gate driver circuit. Four transient voltage suppressor diodes protect the MOSFETs against excessive overvoltage.
Teamed up to decrease size, increase resistance
The ADR battery disconnect switch from Infineon and Schweizer enables the power relay to be replaced by a bi-stable smart circuit-breaker board, without alerting the existing control logic and the control unit. It’s also possible to simply integrate it mechanically into the existing battery box. A further advantage of the Infineon and Schweizer high current relay replacement solution: no software changes are required to benefit from the same ADR functions, restriction free.
A cost-effective cutoff system solution
There are many reasons why opting for a system solution from Infineon for your battery disconnect switch project makes sense. For instance, our high-quality system solution boasts FiT rates of <0.05 ppm. In terms of costs, our bi-stable semiconductor power switchboard provides a better price-performance ratio than a mechanical relay. You can also count on it to turn on and off fast, enabling safe operation in critical situations. Finally, for your peace of mind, a system solution from Infineon is engineered to be extremely robust against short circuits.
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