Robots and industrial automation equipment have become an indispensable part of industrial production process. Now robots are gradually developing into the domestic and commercial markets, appearing before consumers in different forms and functions. These robots need stable power to drive their motors and control systems, in which MOSFETs (Metal Oxide Semiconductor Field Effect Transistors) play an important role. This paper will show you the development history of the MOSFET and the functional characteristics of the power MOSFET introduced by onsemi.
MOSFET has a long history of continuous evolution
The theory behind field effect transistors (FETs) has been known since 1920-1930, 20 years before the invention of bipolar junction transistor (BJTs), but development has been slow due to the lack of appropriate semiconductor materials and the immaturity of technology. At the time, Julius Edgar Lilienfeld (of the United States) proposed a transistor model with two metal contacts on each side and a metallic plate (aluminum) on the top of the semiconductor. An electric field on a semiconductor surface formed from a voltage provided by a metallic plate that controls the current between metal contacts is the original concept of an FET. William Shockely introduced the junction field effect transistors (JFETs) in 1952.
MOSFET was successfully experimented on for the first time in 1960 by Mohamed M. Atalla and Dawon Kahng of Bell Labs, the operating principles of which differ considerably from those of BJT invented by Shockely et al, and it is significantly more important than BJT in the design and manufacture of LSI circuits because a MOSFET is cheaper and has the advantage of a small footprint and high integration. MOSFET has become an essential component of modern electronics and is the most frequently manufactured device in history.
MOSFET has faster switching speeds (very suitable for digital signals), smaller sizes, significantly lower power consumption, and higher density (suitable for large scale integration) than BJT. In addition, MOSFET is cheaper and has relatively simple processing steps, resulting in high manufacturing yields.
In recent years, MOSFET has gradually improved its effectiveness due to the development trend of MOSFET components moving towards scaling and miniaturization. MOSFET has promoted rapid exponential growth of electronic semiconductor technology and supported digital signal processing applications such as memory chips and microprocessors. More and more integrated circuits for analog signal processing can be realized with MOSFET. The application field is becoming more and more extensive.
Power MOSFETs are becoming increasingly important in the market
A power MOSFET is a type of MOSFET that deals specifically with high-power voltages and currents, and is also a power semiconductor. Early power applications used BJT as a switching device, but its shortcomings led to the development of the power MOSFET. After continuous research and improvement, MOSFET became an alternative to BJT, with power MOSFETs becoming commonly used in switching mode power supplies (SMPS), computer peripherals, automobiles, and motor control applications.
Power MOSFETs have the advantage of switching quickly and being efficient at low voltages. Power MOSFETs and IGBT (insulated-gate bipolar transistor) have isolated gateways and are therefore easier to drive. The disadvantage of power MOSFETs is that the gain is low, and sometimes the gate drive voltage is even lower than the voltage actually controlled.
With the continued evolution of MOSFET and CMOS technology, MOSFETs have been used in integrated circuits since 1960, which is why the design of power MOSFETs has been realized. Power MOSFETs have been sold since the 1970s and there is now a wide variety of related products on the market.
Power MOSFETs are the most common power semiconductor devices in the world because they enable low-gate drive power, fast switching speed, and advanced paralleling capability, as well as featuring wide bandwidth, ruggedness, easy drive, simple biasing, easy use, and easy repair, especially for the widest range of low-voltage (less than 200 V) switches, including most power supplies, DC-DC converters, low-voltage motor controllers, and many other applications, with considerable market space.
Select the appropriate MOSFET based on application requirements
There are many MOSFET manufacturers in the market, and the models and types are as many as a school of silver carps moving down a stream. As a result, engineers often have difficulty in selecting a MOSFET. Of course, before choosing a MOSFET, you should first look at the datasheet provided by the manufacturer, and then choose the appropriate product according to your own application requirements.
In selecting a MOSFET, first check the voltage level, and then the RDS (on), rated current, and power dissipation. However, since MOSFETs are affected by operating temperatures, it is necessary to first understand the test conditions of the device. The values on the datasheet are "maximum"or "typical"ones, which affect the actual performance of the device.
In addition, a MOSFET can be selected in four steps. First, decide whether to select an N-channel or P-channel. If the MOSFET is used in low-voltage side switches, an N-channel MOSFET should be used, due to the voltage required to shut down or conduct devices. When a MOSFET is connected to the bus and load grounding, the high-voltage side switch is used, which is usually a P-channel MOSFET.
Then select the MOSFET rated current, which should be the maximum current that the load can withstand in all cases, that is, the peak current generated by the system in continuous mode and pulse spikes, so just select the device that can withstand this maximum current.
Next, thermal requirements are identified, and designers must consider worst-case and realistic system heat dissipation requirements, recommending that worst-case calculations be the primary consideration to provide a greater margin of safety to ensure that the system does not fail.
Finally, to determine switch performance, there are many parameters that affect switch performance, but the most important is the loss of switches generated by capacitance, which is charged at each switch and therefore affects device efficiency.
A power MOSFET that improves operation efficiency of the motor
In recent years, with the rapid development of robotic and automated equipment applications, a large number of motors have been used to control the movement of machine parts and themselves, requiring a large amount of power MOSFETs to drive the motors. onsemi introduced the NTBLS1D5N10MC, a single-pole, N-channel power MOSFET for motor-driven applications.
onsemi’s NTBLS1D5N10MC is a single-pole, N-channel power MOSFET that supports TOLL packaging, can output 100 V, 1.53 mΩ, 312 A power, has low RDS (ON), low total gate charge (QG) and capacitance, has low switching noise/electromagnetic interference (EMI), is Pb-free, compatible with halogen-free/brominated flame retardant (BFR) free devices, complies with RoHS standards, minimizes conduction losses, minimizes drive losses, and can be applied to robotics and automation equipment, power tools, battery-powered vacuum cleaners, UAVs/drones, material handling, BMS/storage, home automation, etc. Common end products include motor control, industrial power supply, and solar inverters.
Conclusion
Robots and automation equipment use a large number of motors to drive machines, so the use of an efficient, stable power MOSFET to drive motors will be the key to improving the operation efficiency of the equipment. onsemi is one of the major MOSFET providers, providing a variety of MOSFET product lines and launching corresponding power MOSFETs for motor-driven applications, which will be the best choice for robotics and automation equipment applications.