Low cost, low power consumption Currently, small AC motor speed control drives mostly use high-end protection components to prevent IGBT overcurrent damage, and are widely used in energy-saving household appliances and industrial drives below 5kW. Using high-voltage integrated circuit (HVIC) technology as a key means, the same characteristics can be provided for applications requiring high integration at the price of low-end products and consumer goods. Overcurrent and discrete protection IGBTs provide a reliable and convenient application foundation for high-efficiency speed control motor drives; however, overcurrent is also a potentially fatal problem for these devices. IGBT overcurrent states generally originate from the following three faults: phase-to-phase short circuit, short circuit to ground, and bridge arm continuity, as shown in Figures 1a, 1b, and 1c. Phase-to-phase short circuits may be caused by wiring errors, short circuits in motor leads, or phase-to-phase insulation breakdown. Short circuit to ground is a result of insulation breakdown to ground in the motor. The last fault, bridge arm continuity, is a result of IGBT mis-conducted current. Traditional protection schemes applicable to all the above-mentioned fault states are often implemented using hardware methods consisting of discrete sensors and analog components. For example, to prevent phase-to-phase short circuits and bridge arm continuity, overcurrent conditions are typically detected using Hall effect sensors connected in series with the negative terminal of the DC bus or shunt resistors connected to linear opto-isolators. Additionally, to provide protection against short-circuit to ground, an extra Hall effect leakage current sensor needs to be placed at the positive terminal of the AC input line or DC bus. The protection circuit can be implemented using high-speed comparators; however, in the event of a phase-to-phase short circuit, since the current direction may be positive or negative, if the Hall effect sensor is located on the motor phase output side, each sensor requires two comparators. In summary, the actual bill of materials for the protection circuit will include two Hall effect sensors or linear opto-isolators, two comparators, a voltage reference, resistors, capacitors, etc., and each Hall effect sensor also requires its own separate isolated power supply. Opto-isolators and Hall effect sensors used for gate drives typically introduce a delay of more than 2ms in the turn-off channel. Designers must consider this delay when selecting the dead time of the IGBT. Alternatively, an anti-saturation circuit can be used to protect the IGBT. This circuit detects the voltage drop between the collector and emitter when the IGBT is fully turned on. If the voltage drop exceeds a certain threshold, the anti-saturation circuit turns off the corresponding gate drive signal. An anti-saturation circuit composed of discrete components requires a comparator and voltage reference, a high-voltage diode, and resistors and capacitors. Regardless of the method used, the material consumption and assembly costs required for such a complex protection function make it unsuitable for cost-sensitive applications. If a soft turn-off (SSD) function that can provide a larger safety margin for the reverse bias safe operating area (RBSOA) is also needed, six additional opto-isolators and six buffer circuits with delayed turn-off capability are required. HVIC: On-chip Protection Today, high-voltage integrated circuit (HVIC) technology can provide single-chip current sensing solutions and can also integrate protection circuits into the IGBT gate driver. For example, IR's recently released series of single-chip HVIC devices combine CMOS circuitry with 600V or 1200V N-channel and P-channel LDMOS transistors, enabling level shifting from low to high voltage and vice versa. This allows the CMOS circuitry to perform high-side gate driving and signal processing based on the levels of a high-voltage floating power supply, with its floating capability allowing the handling of differential-mode signals with common-mode voltages up to 600V or 1200V. As a member of this type of HVIC, the IR22381Q integrates all six IGBT gate drivers and complete IGBT protection, including SSD functionality. The IR22381Q is a three-phase full-bridge driver with bleed drive, featuring rail-to-rail output stages with full-scale 200mA/300mA, undervoltage lockout on all power lines providing on-chip protection during power-up and power-down to prevent bridge arm conduction current and device failure. All six channels also have anti-saturation detection to handle phase-to-phase short-circuit conditions. The SSD function supports custom shutdown modes via a dedicated pin. Soft-turn-on limits voltage and current spikes, reduces electromagnetic interference, and all IR HVIC gate drivers offer up to 50V/dt immunity and can withstand transient negative voltages. Each output driver features a high-pulse-current buffer stage to minimize drive crosstalk. Inputs utilize pull-down Schmitt triggers for noise immunity and to prevent false turn-on of MOSFETs or IGBTs. Extremely low quiescent current facilitates bootstrap power supply, and a programmable dead time is also provided. Therefore, this technology saves six discrete opto-isolators, two Hall effect sensors, two comparators, and other additional circuitry, including discrete buffer or SSD circuitry and IGBT driver discharge circuitry. When implementing a discrete approach, the discharge circuit typically requires an additional opto-isolator. Since the IR22381Q allows bootstrap power supply, this method also eliminates the need for four floating power supplies. HVIC technology integrates all these functions into a single monolithic device, significantly reducing design complexity, material costs, device size, and manufacturing time, while improving reliability. Figure 2a shows an application circuit of this HVIC, which integrates a three-phase gate drive and IGBT anti-saturation protection for each high-side and low-side output. Figure 2b also shows the internal circuitry of the anti-saturation detection (DSD) function in this chip. The maximum high-side float voltage can be as high as 600V to 1200V. Overcurrent detection is achieved by detecting the collector-emitter voltage drop VCE when the IGBT is turned on using an external diode and comparing it with a fixed 8V threshold. The detection result has a 1ms delay, and a 3ms latch-up delay also avoids the influence of IGBT turn-on delay on overcurrent detection. Once an oversaturation state is detected, the output stage immediately enters a high-impedance state and activates the SSD drive, turning off the IGBT with an appropriate drive impedance through the SSDH/L pin. The SSD process is maintained for 7ms to smoothly release the IGBT gate charge under high collector current levels. An external resistor connected in series with the 75Ω internal resistor to the dedicated SSD pin controls the discharge impedance. Short-circuit information can be shared with other high-side or low-side drivers via the input/output pin SY_FLT, allowing the main driver—used for short-circuit detection—to communicate with other drivers through this local network. Once activated, the short-circuit signal freezes the output states of all other drivers and ignores any input states; the main driver also freezes its own state until the SSD process occurs. After the soft shutdown process, the SY_FLT signal is deactivated, and diagnostic information is sent to the main controller via the FAULT/SD pin. Subsequently, the main driver pulls the FAULT/SD pin low, forcing a hard shutdown. The FAULT/SD pin can be used to shut down all other drivers in the local network and report fault status to the main controller for fault diagnosis. To detect IGBT oversaturation, the collector voltage is read using an external high-voltage diode. This diode is typically biased by an internal pull-up resistor connected to the local power line (VB or VCC). When the IGBT is turned on, the diode also conducts, and the current flowing through it depends on the value of the internal pull-up resistor. In high-end circuits, the bias current of the anti-saturation circuit may be related to the size of the bootstrap capacitor. Too low a resistance value will lead to high current and exacerbate the discharge of the bootstrap capacitor. Therefore, a typical pull-up resistor is around 100kΩ, which is the internal pull-up value. Since the DSH/DSL pin impedance is very low when the IGBT is on (the path from the external diode to the IGBT is a low-impedance path), the pull-up resistor can only control the pin impedance when the IGBT is off. If so, the corresponding dV/dt generated at the IGBT output during commutation will inject a considerable current into the anti-saturation detection pin (DSH/L) through the stray capacitance of the diode. Providing an active bias for the detection diode can potentially greatly reduce this coupling noise. The DSH/L pin has an active bias structure. The DSH/L pin has active pull-ups corresponding to VB/VCC and active pull-downs corresponding to VS/COM. This dedicated bias circuit can reduce the DSH/L pin impedance when the voltage exceeds the VDESAT threshold. Low impedance helps suppress noise and avoids current injection through parasitic capacitance. When the IGBT is fully turned on, the detection diode is forward biased, and the DSH/L pin voltage decreases. In this respect, the passivation bias circuit can reduce the diode bias current. The IR22318Q provides a suitable single-chip IGBT drive solution for AC induction motors and brushless DC/AC motors with a drive power of up to 10–15 HP, using a 400V three-phase AC power supply (550V DC bus), as well as a wider range of general-purpose drives.