In smart factories, the improvement of motor efficiency will bring a wide range of benefits. This article will show you the important features of ADI's isolated gate driver.
Fast switching increases efficiency of motor operation
According to the data of the International Energy Agency, the power consumed by motor drive systems accounts for 40% of global electricity consumption. The improvement of motor efficiency will bring great benefits to the required energy conservation and carbon reduction. By controlling MOSFET or IGBT during operation and controlling the current of the motor according to the speed of turns on or off commanded by the user, the efficiency of motor operation will be greatly improved.
In power electronics (such as drive technology), IGBT is often used as high voltage and a high current switching. These power transistors are controlled by voltage, and their main losses occur during switching. In order to minimize switching losses, shorter switching time is required. However, fast switching also implies the danger of high voltage transients, which may affect or even damage processor logic. Therefore, the gate driver that provides the appropriate gate signal for IGBT will also perform the function of providing short circuit protection and influence the switching speed. Some of these features will be crucial when selecting the gate driver.
During switching, the transistor will be in a state where both high voltage and high current are applied. According to Ohm's Law, this will lead to certain losses, depending on the duration of these states, so the goal is to minimize these time periods. The main impact factor here is the gate capacitance of the transistor, which must be charged/discharged in order to realize switching, and higher transient current will accelerate this process. Therefore, drivers that can provide a higher gate current for a longer period of time can play a more positive role in switching losses.
Reduction of electromagnetic interference and realization of voltage overshoot control
ADI has worked hard to promote the development of Industrial 4.0 technology. Its ADuM4122 isolated gate driver, an isolated dual drive strength output driver using iCoupler® technology, enables designers to take full advantage of more efficient power switching technology to help customers maximize the efficiency of the motion system and minimize its electromagnetic (EM) emissions when migrating to higher density automation.
The ADuM4122 is a simple dual drive strength output driver that can efficiently toggles between two slew rates controlled by digital signals. Compared with the current discrete solution with 20 or more pins or complex integrated solutions, the ADuM4122 is smaller in size and has only 8 pins, and thus can be used under a variety of operating conditions.
The ADuM4122 uses iCoupler® technology to achieve high precision isolation, providing 5 kV rms isolation in an 8-lead wide-body SOIC package. These isolation components combine high-speed CMOS and monolithic transformer technology to provide better performance characteristics than alternative products (such as a combination of pulse transformers and gate drivers).
The ADuM4122 operates from an input supply voltage range of 3.3 V to 6.5 V and is compatible with lower voltage systems. Unlike gate drivers using high voltage level translation methodologies, the ADuM4122 provides true galvanic isolation between the input and output regions. The ADuM4122 also includes two output pins to facilitate slew rate control of the two output drive strengths. The VOUT pin follows the logic of the VIN+ pin, while the boosted output VOUT_SRC can be toggled to follow the VIN+ pin or set to high impedance. The toggling of the slew rate is controlled by the primary side, and slew rate control can reduce electromagnetic interference (EMI) and realize voltage overshoot control.
In addition, if the internal temperature of the ADuM4122 exceeds the thermal shutdown temperature, the internal thermal shutdown sets the output low. Therefore, the ADuM4122 reliably controls the switching characteristics of IGBT and MOSFET configurations at various switching voltages, enabling simple slew rate control.
Improved system functionality for high performance applications
Each output pin of the ADuM4122 supports a 2 A output current (<3 Ω RDSON_X), has a 3 A peak short-circuit current, supports 3.3 V to 6.5 V, VDD1, and 4.5 V to 35 V, VDD2, has a positive going threshold with under voltage lock out (UVLO) function at 3.3 V VDD1, and there are multiple positive going threshold UVLO options on VDD2, including 4.4 V (typical) positive going threshold with UVLO at grade A, 7.3 V (typical) positive going threshold with UVLO at grade B, and 11.3 V (typical) positive going threshold with UVLO at grade C.
The ADuM4122 also supports precise timing characteristics, with falling edge propagation delay up to 48 ns, CMOS input logic level, high common-mode transient immunity > 150 kV/µs, high operating junction temperature of 125 ℃, default low output, selectable slew rate control, safety and regulatory approvals, UL 1577 recognition, 1 minute at 5 kV rms, CSA component acceptance notice 5A, and VDE conformity certificate, conforming to DIN V VDE V 0884-10 and VIORM = 849 V peak.
The ADuM4122 further improves the functionality of the system with high common-mode transient rejection and low propagation delay. It can be applied to switched power supplies, isolated IGBT and MOSFET gate drivers, industrial inverters and other products, and is suitable for high performance applications such as motion control, robotics, and energy.
Easily set slew rate to improve product development speed
To speed up product development, ADI has also introduced an evaluation board that supports the ADuM4122. The EVAL-ADuM4122EBZ evaluation board provides jumpers and screw terminals for configuring different drive conditions. The EVAL-ADuM4122EBZ board handles square wave and DC values on the VIN+ and SRC pins.
The ADuM4122 operates at voltages up to 35 V. The logic level on the VIN+ pin voltage controls the VOUT output, while the SRC pin controls whether the VOUT_SRC pin is set to high impedance or follows the logic of the pulse width modulation (PWM) input provided by the user on VIN+. When an external series gate resistor is combined with the outputs from the VOUT and VOUT_SRC pins, an isolated gate driver can have two easily selectable slew rates.
The EVAL-ADuM4122EBZ board tests the device's propagation delay, drive strength, slew rate selection, and input logic. It has 3 A short-circuit output capability, output power device resistance <3 Ω, output voltage range of 35 V, and supports output and input UVLO. The pad placement is suitable for various switch types and external series gate resistors. With screw terminals for easy connectivity, it can be placement for capacitive load testing, and the slew rate can be easily set using jumpers.
Conclusion
In the past, when using gate drivers, in order to ensure compliance with EM system regulations at all operating points, the system was usually over-engineered, but the utilization rate was insufficient. ADI's ADuM4122 isolated gate drivers can dynamically realize the transition from slower to faster switching, thus optimizing EM emissions without sacrificing efficiency. In short, when you try to reduce emissions and power consumption, you don't need to sacrifice performance. It will be one of the best choices when you develop power supply systems.