“The electrical system has always been a relatively sensitive unit in automobile safety, and many common small problems are caused by the unsatisfactory reliability of the electrical system. For electric vehicles, galvanic isolation is necessary due to the inclusion of more functional units, including traction inverters, temperature control and heating systems, and on-board chargers, which operate at completely different voltage levels. ).
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The electrical system has always been a relatively sensitive unit in automobile safety, and many common small problems are caused by the unsatisfactory reliability of the electrical system. For electric vehicles, galvanic isolation is necessary due to the inclusion of more functional units, including traction inverters, temperature control and heating systems, and on-board chargers, which operate at completely different voltage levels. ).
From past experience, electrical isolation for data transmission is achieved through optical technology with the help of LED sources and photodiode receivers. However, stimulated by the automotive market demand represented by electric vehicles, optocouplers have become the device of choice for electrical isolation. As a device that uses optical media to achieve isolation, the application of optocouplers greatly ensures the safety and reliability of the electrical system of new energy vehicles. Toshiba’s automotive-grade optocouplers are among the best.
As a relatively common isolation control device, the optocoupler encapsulates the light-emitting element and the photosensitive element in the same housing to ensure no external interference. The main advantage of the optocoupler is that it transmits signals in one direction. It realizes the smooth transmission of the signal through the transmission mode of electricity→optical→electricity. At the same time, the input side and the output side of the device are completely electrically isolated, with strong anti-interference ability and long service life. Long, high transmission efficiency advantages.
With the continuous development of new energy vehicles, the capacity of the battery pack in the car and the design complexity of the battery pack itself have also increased, which makes the safety of the battery pack particularly important. In the BMS (Battery Management System, battery management system) of electric vehicles, a variety of optocouplers are required to sample and monitor the data of various indicators of the battery pack. Take Toshiba’s automotive-grade optocoupler products as an example: in the BMS system of a new energy vehicle, TLX9376 and TLX9310 optocouplers control data transmission; photorelay (photorelay) – TLX9175J realizes the system control of the battery pack. The above-mentioned Toshiba products are all packaged in SO6 ultra-thin packages, with an operating temperature range of -40°C to 125°C (except for the TLX9175J, whose operating temperature is -55°C to 105°C). Toshiba’s optoelectronic products can perfectly meet the needs of in-vehicle applications in traditional vehicle, electric vehicle and hybrid vehicle inverter control (EV inverter) and intelligent power module (IPM) interface applications.
The TLX9175J automotive-grade photorelay we mentioned above, its main application direction not only includes the battery management system (BMS) on electric vehicles/hybrid electric vehicles, but also can be used in the field of Internet of Vehicles to realize remote control of vehicles and Remote reading of information and other functions. Toshiba TLX9175J can meet the AEC-Q101 test requirements that are far more stringent than consumer chips. With its long life, superior reliability and low power consumption, TLX9175J is used in the batteries of a number of electric vehicle manufacturers represented by Great Wall and Weilai. It is widely used in management system.
Structural characteristics of Toshiba optocoupler
Compared with traditional mechanical relays, photorelays have obvious technical advantages in many aspects. The first is the life of the relay. Also take the Toshiba TLX9175J photorelay as an example: the product receives LED light through the photodiode array and generates a voltage to drive the MOSFET to work. Since there is no mechanical contact, the TLX9175J does not need to worry about mechanical wear and tear. At the same time, there is no Noise caused by back EMF or bounce, greatly extending the life of the device. In addition, TLX9175J adopts a new high-power infrared LED MQW structure. After 100,000 hours of continuous operation, the output light attenuation rate of the new LED is much lower than that of traditional LEDs. This means that the life and stability of the TLX9175J with the new MQW structure will be superior compared to the traditional photorelay.
In terms of circuit size, Toshiba TLX9175J adopts 4pin SO6 package with a height of only 2.2mm. The ultra-small package size means that the height/thickness of the final product is reduced, which can improve the flexibility of circuit board design. Since the LED on the input side is driven by current, the input current required for the Toshiba TLX9175J output to turn on does not exceed 15mA, so the user can directly drive the photorelay using the pins of the MCU. In Contrast, ordinary mechanical relays require larger drive currents. In most cases, the user needs to add another Transistor to improve the driving capability of the MCU. Therefore, in low power consumption scenarios, Toshiba TLX9175J photorelay has more advantages.
In order to facilitate development engineers to better apply photorelays, Toshiba provides PSpice and LTspice models for circuit simulation, allowing developers to more conveniently and accurately implement circuit design and simulation of photorelays.
So how to reflect the above technical advantages in the actual design, we will simply show you an example of an electric vehicle battery total voltage monitoring circuit using photorelays and IC output optocouplers. It can be seen that the design of the voltage detection circuit is very simple. Through the design of photorelays and optocouplers, the battery is completely isolated from the MCU, and the MCU can also measure the total voltage of the battery, which can be obtained in emerging fields such as new energy vehicles. widely used. And Toshiba TLX9175J noiseless, low power consumption, space saving and other advantages make photorelays can be used in most environments that require battery voltage monitoring.
Photorelay application design example diagram
In order to meet the more powerful new energy vehicle power battery system, Toshiba has planned the TLX9160T to be mass-produced. Compared with the TLX9175J, which is suitable for 400V and below scenarios of 100-string battery packs, the TLX9160T has an operating voltage of up to 1500V, which can meet the application requirements of 200-string battery packs of 800-900V.
Toshiba has been deeply involved in the field of photorelays for many years, from front-end chip manufacturing to back-end component installation, it already has a mature process and a complete system. With its excellent innovation ability and keen sense of the market, Toshiba has integrated the latest MOSFET process design into photorelays and developed hundreds of high-quality photorelay products, helping everyone go further on the road of electrical isolation.
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