EV battery stack voltage levels continue increasing from 400 V to 800 V – even as high as 1 kV – enabling automakers to achieve reduced weight, increased torque, high efficiency and faster charging.

Isolated semiconductors enable low-voltage digital and analog circuits to safely operate with high-voltage batteries while achieving the required level of galvanic isolation. Isolated voltage sensors, current sensors, ADCs and CAN transceivers are a few examples of signal-chain ICs requiring low-voltage DC bias on both sides of the isolation boundary. The UCC12051-Q1 is a low-voltage isolated DC/DC power module leveraging TI’s integrated magnetic laminate, planar transformer technology to provide up to 500 mW of 5-V to 5-V (or 3.3-V) bias while achieving 5-kV_RMS isolation.

Battery management systems (BMSs) and traction inverters are two of the most critical EV subsystems where the 800-V domain needs to be isolated from the chassis.

BMSs use a pre-charge circuit when connecting high-voltage battery terminals to subsystems. The 5-kV_RMS TPSI3050-Q1 isolated switch driver replaces mechanical pre-charge contactors to form a smaller, more reliable solid-state solution. To prevent passenger exposure to high voltages, the BMS frequently monitors the insulation between each terminal of the battery (HV+ and HV–) to the metal chassis. Solid-state relays (such as the TPSI2140-Q1) work with a battery-pack monitor (such as the BQ79631-Q1) to detect insulation faults in 800-V BMSs faster and with higher accuracy than solid-state photorelays. The TPSI2140-Q1 enables the use of <1-MΩ resistors and withstands over 300% more avalanche current than traditional photorelays to help enable safer human-system interaction.

The block diagram shown in Figure 10 is an example of a traction inverter highlighting the use of isolated gate drivers to drive high-voltage insulated-gate bipolar transistor (IGBT) or silicon carbide (SiC) modules in a three-phase, DC/AC inverter configuration. These modules often co-package as many as six IGBT or SiC switches, requiring up to six isolation transformers, powering six independent gate-driver ICs. To minimize PCB area by reducing the number of external transformers, the UCC14240-Q1 is a dual-output, mid-voltage, isolated DC/DC power module that can enable higher performance in traction inverter, gate-driver bias applications.

Isolated DC/DC modules such as the UCC14240-Q1 and UCC12051-Q1 are not limited to a particular bias function, and therefore lend themselves to a variety of power architectures. With some sacrifice in scalability, it is possible to realize even higher degrees of integration by combining signal chain and power into a single IC package. Examples include power plus a digital isolator (the ISOW7841A-Q1), power plus an ADC (the AMC3336-Q1) and power plus an amplifier (the AMC1350-Q1).