Circuit breaker is a device used to protect circuits from overcurrent, overload, and short circuit damage. It is not used to protect personnel from electric shock, and the device used to prevent such electric shock is called residual current device (RCD) or ground fault circuit breaker (GFCI). This device can detect leakage current and cut off the circuit. The design of electromechanical circuit breakers can be traced back to the 1920s and are still widely used today. Compared with early fuse designs, circuit breakers have significant advantages - they can be reused, and early fuses must be replaced after one use. Nowadays, with the development of wide bandgap semiconductor technology, solid-state circuit breakers are occupying a larger market share. Compared with silicon-based semiconductors, wide bandgap semiconductor switches have lower on state losses and higher efficiency during normal operation. Solid state circuit breakers (also known as electronic circuit breakers) do not contain mechanical components because their switching core is a semiconductor. It detects fault states and cuts off circuits through electronic components to ensure the safety and reliability of the electrical system. Solid state circuit breakers have the characteristics of faster response speed, dynamic adjustment, and can also be connected to intelligent networks, and support remote monitoring. Its application scenarios are very extensive, covering residential, commercial, and industrial communication (AC) systems; It can also be used in high-voltage direct current (HV DC) systems, such as as as an isolation switch for high-voltage batteries in electric vehicles.  

Solid state circuit breaker block diagram

The following figure shows a schematic diagram of a solid-state circuit breaker solution using Ansenmei's recommended product. The most critical component is the switch that replaces traditional electromagnetic relays. The gate driver is used to control switches, while the interface module enables communication between devices. The other core part is the detection module, which includes current detection and temperature detection functions. To enhance system performance, ground fault circuit breakers (GFCI) can be integrated.

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Silicon carbide JFET

A junction field-effect transistor (JFET) is a unipolar transistor that primarily relies on majority carriers for conduction. It is similar to MOSFET, both working based on the principle of electric field effect, belonging to voltage controlled devices, and does not require bias current.

The main difference between the two is that JFET is a depletion type device (i.e. default on state) that requires a reverse bias voltage to turn off and maintain the off state. Although some semiconductor relay applications can benefit from this default on state, most applications require a default off state. By adding some external components, a default off switch can be constructed even when no power is applied.

Figure 1 shows the cross-sectional structure of SiC JFET with VGS=0 and drain source voltage VDS almost zero. This structure represents one of the thousands of parallel units in a JFET chip. An ON Semiconductor SiC JFET has two PN junctions (diodes): drain gate and gate source. In this unbiased state, there is a highly conductive channel between the drain and source, allowing electrons to flow freely in both directions, thereby achieving the unique low on resistance characteristics of Anson SiC JFET.

Ansenmei can provide three series of products: SiC JFET, SiC Cascoe JFET, and SiC Combo JFET, each with its unique performance and suitable for different application scenarios. Among them, SiC JFET can enable solid-state circuit breakers (SSCBs) to operate at the extreme temperature of the casing material up to 175 ° C; And SiC material itself can withstand higher temperatures.

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Figure 1: Schematic diagram of longitudinal JFET structure with labeled current path

SiC JFET

·Normally open SiC JFET

·Having the lowest Rds

· RDS(VGS 2V) = 7 mΩ, RDS(VGS 0V) = 8 mΩ

·Suitable for circuit breakers and current limiting applications

·The gate source voltage (VGS) of JFET in conducting state can directly reflect the device junction temperature (TJ), which is an ideal solution for self-monitoring power devices

SiC Cascode JFET

·Co packaged with silicon-based MOSFET

·Constant off type

·Support standard gate drive

·Built in JFET gate resistor

·Suitable for high-frequency switch applications

SiC Combo JFET

·Capable of independently controlling the gates of MOS transistors and JFETs, achieving precise control of switch dV/dt

·Can directly drive the gate of JFET, reducing RDS (ON) by 10%~15% under VGS=+2V conditions

·Simplify the parallel use of multiple JFETs

·Adopting the same gate driving method as discrete JFET+MOSFET

·Significant savings in circuit board space

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Figure 2: Schematic diagram of symbols for JFET (top image), Cascoe JFET (bottom left image), and Combo JFET (bottom right image)

Product Core Value

Ansenmei EliteSiC Combo JFET

SiC Combo JFET Model: UG4SC075005L8S

Integrate a 750V SiC JFET and a low-voltage Si MOSFET into a single TOLL package.

· 750 V, 120 A

·Ultra low on resistance RDS (ON): 5 m Ω at 25 ° C, 175 Ω? 12.2 m Ω at ° C

·Having constant off characteristics

·Optimize the parallel operation performance of multiple devices

·The maximum working temperature can reach 175 ° C

·Capable of high pulse current

·Excellent device robustness

·Short circuit withstand capability

·Adopting a leadless TOLL package (MO-229)

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Figure 3: Comparison of on resistance between UG4SC075005L8S and competitors (unit: m?)

Combo JFET Evaluation Board

This evaluation board showcases a solid-state circuit breaker design based on the Anson Mei Combo JFET device UG4SC075005L8S.

SiC Combo JFET is a composite device composed of a low-voltage Si MOSFET and a high-voltage SiC normally on JFET. The gates of SiC JFET and Si MOSFET can be independently connected. Compared with the standard common source common gate structure, SiC Combo JFET has the following advantages: lower on resistance RDS (ON) achieved through driving, fully controllable switching speed, and junction temperature detection capability.

About The Author

This is reported by Top Components, a leading supplier of electronic components in the semiconductor industry

They are committed to providing customers around the world with the most necessary, outdated, licensed, and hard-to-find parts.

Media Relations

Name: John Chen

Email: salesdept@topcomponents.ru

This is reported by Top Components, a leading supplier of electronic components in the semiconductor industry. They are committed to p with the most necessary, outdated, licensed, and hard-to-find parts.

Media Relations Name: John Chen

Email: salesdept@topcomponents.ru