In modern Energy Storage Systems (ESS), efficient and stable operation is crucial for energy management and applications. With the rapid development of renewable energy and the growing emphasis on energy utilization efficiency, ESS is becoming an essential technical support for achieving energy transition. Within this system, thermistors and DC-DC converters, as critical components of ESS, play indispensable roles in temperature monitoring and energy conversion, respectively. This article will explore the key roles and technical characteristics of thermistors and DC-DC converters in ESS, as well as related solutions introduced by Murata.
Thermistors assist in temperature monitoring and protection in ESS
ESS is primarily used to store electrical energy and provide stable power output, with its core component being the battery module. As a highly sensitive temperature sensor, the thermistor plays a vital role in the battery module of ESS.
Most batteries used in ESS (such as lithium-ion batteries) are highly sensitive to temperature. Thermistors monitor the temperature of battery packs in real-time, ensuring that the batteries operate within a safe temperature range. Additionally, during charging and discharging, batteries generate heat, which, if accumulated excessively, may lead to thermal runaway or even fires. Thermistors can trigger protection circuits when the temperature exceeds a set threshold, cutting off the power or reducing the output. In low-temperature environments, battery performance may degrade or even suffer damage; thermistors can monitor such low-temperature states and prompt the system to activate preheating functions.
On the other hand, thermistors can also optimize battery performance, as battery charging and discharging characteristics are closely related to temperature. Temperature data provided by thermistors can help the system optimize charging and discharging parameters, thereby improving energy utilization efficiency. Through precise temperature control, thermistors help prevent overheating or overcooling-induced battery aging, thus extending battery life.
Thermistors play a crucial role in fault diagnosis and predictive maintenance. If the temperature of a particular cell or region rises abnormally, thermistors can issue timely alerts to prevent the issue from escalating. Additionally, temperature data collected by thermistors can be used for historical analysis, helping predict battery aging trends or potential fault points, thereby providing a basis for operational and maintenance decisions.
Thermistors also help adapt to the diverse scenarios of energy storage, as ESS may be deployed indoors or outdoors with significant environmental temperature variations. The high sensitivity and wide temperature measurement range of thermistors allow them to adapt to various scenarios. In renewable energy fields such as wind and photovoltaic energy, thermistors in ESS help manage battery temperature fluctuations, ensuring system stability and reliability.
Thermistors serve as temperature sensors in ESS applications
Thermistors are semiconductor devices whose resistance value changes with temperature. They are primarily used in temperature sensing and current control applications and can serve as temperature sensors in ESS applications. Based on the way their resistance value changes with temperature, thermistors are divided into two major types: Positive Temperature Coefficient (PTC) thermistors and Negative Temperature Coefficient (NTC) thermistors.
PTC thermistors increase their resistance value as temperature rises, and they are mainly used for overcurrent protection, temperature switches, and self-recovery protection for heating devices. In electronic devices, when the current exceeds the rated value, the PTC thermistor in series with the protected circuit increases its resistance value through self-heating, thereby suppressing the excessive current. Additionally, PTC thermistors can act as temperature switches. When the system temperature exceeds a preset value, the PTC resistance increases, triggering the corresponding switch action.
NTC thermistors, on the other hand, decrease their resistance value as temperature rises. This characteristic can be used to monitor the temperature of electronic components or devices to ensure their proper operation. In some applications, NTC thermistors are used to compensate for temperature changes in devices, maintaining stable performance.
Thermistors are ubiquitous in our daily lives. They are used not only as thermometers and temperature sensors in air conditioners but also as temperature controllers in smartphones, electric kettles, and irons. Furthermore, thermistors are widely applied in various power devices for current control. Recently, with the increasing electrification of vehicles, thermistors have been extensively used in electric vehicle projects, such as onboard battery packs and LiDAR. Moreover, thermistors find broad applications in various industrial and energy projects, including EV fast-charging infrastructure, solar inverters, energy storage inverters, and battery packs.
Murata has introduced various types of thermistors to meet the needs of ESS applications. Murata's thermistor products are divided into two main series: NTC thermistors and PTC thermistors. The NTC thermistor series includes the NCU for high-reliability applications, the NCP for consumer-grade applications, and the NCG for conductive glue mounting. The PTC thermistor series features PRF for overheating protection and PRG for overcurrent protection. Among these, the NCU series is widely used in automotive and energy projects.
Murata's NCU series is an SMD-type NTC thermistor. Thanks to its unique structure, the external copper electrodes provide high reliability, enabling flexible application in variety demanding temperature detection scenarios. It is a flagship product among Murata's thermistors and is suitable for high-reliability markets such as automotive, industrial, and energy. It enables wide-temperature-range detection and temperature compensation functions.
Power modules for energy transfer and management of ESS systems
Nowadays, ESS systems mainly appear in the form of modular solutions. Usually ESS systems include battery modules, management modules (thermal management/energy management/battery management) and power conversion modules. For example, in the power conversion module of the ESS system, MPPT or 3P T inverter is mainly used to provide energy conversion and transmission. There are a large number of SiC or GaN Mos transistor. The driving current of these switching transistor is larger and the driving process needs to be more efficient, and fast gate voltage switching to reduce energy loss due to delays.
A complete ESS management module usually contains a large number of CAN bus, RS485, RS232 interfaces, as well as MCU, cell monitoring chips, etc. Such interfaces and chips also require electrical isolation in applications. In response to these two types of actual needs, Murata provides gate isolation drive modules and low-height SMD type interface isolation module solutions.
Isolated DC-DC converters for IGBT, SiC, MOS, and GaN
Murata offers a series of isolated DC-DC converters specifically designed for gate driver circuits, suitable for IGBT, SiC, MOS, and GaN product lines. These converters are commonly used in applications such as renewable energy, motion and control, mobility, and healthcare solutions. The features include ultra-low isolation capacitance of 3pF, optimized bipolar output voltage for IGBT/SiC and MOS gate drives, a DC link voltage withstand capability of up to 3kV, reliability against partial discharge, and dv/dt immunity sustaining over 80kV/µs at 1.6kV for extended durations.
Murata has also commercialized insulated DC-DC converters tailored for next-generation GaN power semiconductors capable of handling high frequencies, contributing to rapid power conversion required in various applications. The MGN1 series 1W output DC-DC converters are designed to deliver the voltages needed for GaN device gate drivers.
The MGN1 series devices offer a thin, small-footprint, surface-mount solution that can be easily integrated into space-constrained systems. They also feature a lightweight design, providing greater deployment flexibility. The available output voltages are +8V, +12V, and +6/-3V.
One of the key attributes of the MGN1 series DC-DC converters is the ultra-low isolation capacitance of 2.5pF (typical). This minimizes transient coupling on the isolated gate, preventing signal distortion. Additionally, this helps alleviate system EMI issues. With a common-mode transient immunity (CMTI) exceeding 200kV/μs, these converters are highly suitable for GaN-based systems with high switching speeds, ensuring the integrity of gate driver signals. Their immunity to partial discharge allows reliable operation under high-voltage conditions.
The DC-DC converters in Murata’s MGN1 series support a continuous isolation withstand voltage of 1.1kV. These converters feature a creepage and clearance distance of 6.5mm and an operating temperature range of -40°C to +105°C, enabling installation in challenging environments. Additionally, they incorporate reverse polarity and short-circuit protection mechanisms.
DC-DC converters for interface isolation
Murata also introduces a new generation of NXE and NXJ series of SMD modules, which have the differentiation factor of miniaturization and are space-saving customer solutions. These modules feature built-in transformers and adopt fully automated production and testing systems for higher reliability, and cost-effective. They support a solder temperature of 260°C, and complies with AEC-Q104 standards. NXE and NXJ series support isolated communication power supply, adopt CAN bus, RS485, RS232 interface, support AS-Interface (Asi), an industrial network solution device layer bus technology. These modules provide isolated positive and negative voltages for voltages for analogue circuitry and are suitable for Industrial applications such as image signal and sensor isolation.
The NXE series supports 3kVDC isolation test voltage, 2.1-3pF (typical) isolation capacitance, and delivers 1W-2W power. The reinforced type complies with 125Vrms, while the basic type 250Vrms safety approvals. It adopts an open frame SMD package and operates within a temperature range of -40°C to 105°C. The NXJ series supports 4.2kVDC isolation test voltage, 2-2.5pF (typical) isolation capacitance, and delivers 1W-2W power. The reinforced type complies with 200 to 250Vrms, and the basic type complies with 250Vrms safety approvals. It also adopts an open frame SMD package and operates within a temperature range of -40°C to 110°C.
Conclusion
Thermistors and DC-DC converters play core roles in temperature monitoring and energy management within ESS, jointly forming the technological foundation for the efficient, safe, and intelligent operation of ESS. The high sensitivity and reliability of thermistors ensure that battery modules operate within the optimal temperature range, reducing risks associated with overheating and overcooling, thereby extending battery lifespan. Meanwhile, DC-DC converters achieve dynamic energy distribution among different devices through precise voltage regulation and efficient energy transfer, meeting the diverse needs of the system. Murata provides a comprehensive range of thermistors and DC-DC converter products, driving ESS toward greater efficiency, intelligence, and sustainability.