Innoscience Technology

Increased demand for convenient eco-friendly travel, mobile energy storage, and small power solutions has driven rapid market developments. Battery protection system (BMS) technology needs further advancement to improve battery safety and efficiency. GaN technology supports this by improving efficiency, power density, and thermal performance, improving the overall conversion efficiency of power systems. With no parasitic body diode and bidirectional control, one (1) innoscience’s bi-directional (VGaN) device can effectively replace two (2) traditional MOS Silicon pairs. Innoscience’s VGaN series brings these advantages to Over Voltage Protection (OVP) and BMS applications.

A 48V/180A BMS demo is the latest Innoscience design solution to support a high-side same-port BMS application. This design adopts Innoscience’s latest 100V VGaN product, the INV100FQ030A, which is packaged in a 4mm x 6mm² FCQFN and offers a maximum on-resistance of 3.2mΩ. No heat sink is required with a maximum temperature rise of less than 50°C. The 16-string charging and discharging battery protection system uses the controllable bidirectional conduction and cut-off features of VGaN, enabling four operational states: normal charging and discharging, charging protection, discharging protection, and sleep mode. 

Innoscience’s 48V/180A high-side BMS solution is ideal for home batteries, portable charging stations, e-scooters, e-bikes etc., optimizing battery life and safety through efficient charge and discharge control. It reduces temperature rise and system costs while ensuring a compact, portable design. 

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GaN high electron mobility transistors, HEMTs, or HFETs, have been fabricated using a 600 V process that produces devices with on-resistances down to 70 mΩ. Unidirectional and bidirectional devices were fabricated on the same wafer for performance comparison. A p-GaN gate is used to obtain normally-off properties in the devices.

To produce the bidirectional HFET, a second gate (G2) is added to the drift zone close to drain D1 and is used as the controlling gate for one direction of operation (Figure 1). The bidirectional GaN HFET is symmetrical and can carry the same current in both directions.

The addition of the second gate didn’t materially impact device performance. The specific on-resistance for the bidirectional FET is the same in both directions and 3% higher than for the unidirectional devices. The off-state drain leakage current up to 600 V was below 5 µA for both devices. In a 10 A, 400 V clamped inductive switching test, both devices demonstrated slew rates of 60 V/ns during turn-off.

In another case, a device has been developed for topologies like Vienna rectifiers in power factor correction circuits, current-sources inverters in renewable energy systems, and solid-state circuit breakers. On an equivalent performance basis, the device is 4x smaller than a SiC bidirectional FET, 3x smaller than two uni-directional GaN devices, and 9x smaller than a traditional silicon solution (Figure 2).

USB port OVP protection

A 40 V, 4.8 mΩ bidirectional, normally-off, enhancement mode (e-mode) GaN transistor is available in a wafer-level chip-scale (WLCSP) package for lower power and voltage applications. It’s designed to replace back-to-back Si MOSFETs in battery management systems (BMS), overvoltage protection (OVP) applications, switching circuits for multiple power sources in standby and backup power systems, and high-side load switches in bidirectional converters. In addition to their low on-resistance, these devices are characterized for operation at 1 MHz.

ARPA-E CIRCUITS

The Advanced Research Projects Agency-Energy (ARPA-E) Creating Innovative and Reliable Circuits Using Inventive Topologies and Semiconductors (CIRCUITS) program sponsored the development of a GaN-based four-quadrant switch (FQS).

An FQS replaces two FETs, two IGBTs, and two diodes with a single device that provides bidirectional voltage control and current flow. It uses two gates to block the voltage of either polarity and supports current flow in either direction. The use of FQSes will reduce parts count, resulting in higher power densities, higher reliability, and lower-cost solutions.

Lateral GaN technology enables the fabrication of FQSes because the voltage-blocking region can be shared between the two sections of the device. That’s not possible with vertical structures used for Si and SiC devices. Prototype FQSes have been fabricated using 650 V GaN technology with a threshold voltage of 4 V. Being fabricated with GaN; these devices support fast switching and low losses for compact and high-efficiency solutions.

E-bikes and more

For battery-powered devices like electric bicycles (E-bikes) and energy storage systems, a 100 V bidirectional GaN-on-Si e-mode device is offered in a 4.0 x 6.0 mm flip-chip quad flat no-lead (FCQFN) package. These devices are rated for 100 A and have a maximum RDD(on) of 3.2 mΩ with a VG of 5 V and a typical QG of 90 nC with a VDD of 50 V.

This device’s applications include protection in a battery management system, (BMS) high-side switch in bidirectional converters, and switching circuits in multiple power supply systems. A BMS application can be paired with an analog front-end (AFE) IC that supports cell balancing and a gate driver (Figure 3). With proper heatsinking, this single-gate device is rated for 120 A.

Summary

Bidirectional GaN switches with ratings from 40 to 650 V have been developed. They can simplify and shrink a variety of applications, from portable electronics to e-bike battery systems, multi-kW motor drives, and renewable energy inverters.

References

100V bi-directional GaN IC for 48V/60V Battery Management System (BMS) applications, Innoscience
Bi-directional GaN FETs, Nexperia
Bidirectional GaN HFETs for T-type converter power conversion, Ferdinand-Braun-Institut
Bi-directional GaN Power ICs open up new possibilities in off-grid applications, Navitas
Transistors for Electric Motor Drives, Advanced Research Projects Agency-Energy

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Littelfuse, Inc.has revealed the newest member of its eFuse Protection IC lineup, the LS0502SCD33S. This novel development introduces the Single Cell Super Capacitor Protection IC, tailored explicitly for charging backup power sources under extreme conditions, setting a new benchmark in the sector. 

Backup power is essential in numerous settings, but lithium-ion batteries’ limited temperature tolerance often restricts their application. In response, Littelfuse engineered the LS0502SCD33S, leveraging supercapacitor technology to deliver a solution that excels in a broad temperature range and offers superior power/energy density. This single-cell approach ensures a reliable and compact backup option.

A standout feature of the LS0502SCD33S is its proficiency in effortlessly managing high operational voltages (above 3 V), eliminating the necessity for intricate power management arrangements. The LS0502SCD33S protects against potential system impairments with its integrated input overvoltage and current protection mechanisms. It offers an adaptable, all-in-one, and space-efficient solution for storage capacitors or capacitor banks. Additionally, it incorporates an ideal diode for reverse blocking to maintain performance and efficiency when the input voltage drops.

The LS0502SCD33S Single Cell Super Capacitor Protection IC is ideally suited for various SuperCap uses, such as: Automotive dash cameras; Smart utility meters; IoT gadgets; Industrial handheld devices; Portable electronics with removable batteries.

The LS0502SCD33S stands out by supporting an extensive array of protection functionalities, such as Over-Current Protection (OCP) and Over-Voltage Protection (OVP), while also being energy-efficient and facilitating automatic primary/backup switchover, distinguishing it from competing products.

Beyond its protective capabilities, the LS0502SCD33S offers numerous advantages. It enhances reliability and extends the lifespan, helping manufacturers lower maintenance costs. Moreover, it promotes extended battery durability and minimizes the end-products’ size due to its compact design, an essential feature for devices that require prolonged standby times.

The LS0502SCD33S is a comprehensive backup storage capacitor system solution that integrates input overvoltage, overcurrent protection, a reverse blocking switch, and supercapacitor charging control circuits. It ensures balanced charging for two-cell supercapacitor configurations, operates with a minimal 2.5 μA current draw after the storage component is fully charged, and signals the disconnection of the input supply, allowing the primary system to react swiftly.

The eFuse Single Cell Protection ICs are available in tape and reel format in quantities of 5,000.

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