KAWASAKI, Japan—Toshiba Electronic Devices & Storage Corporation ("Toshiba") has launched a gate driver photocoupler, “TLP5814H,” with an output of +6.8A/-4.8A, in a small size SO8L package, that incorporates an active Miller clamp function for driving silicon carbide (SiC) MOSFETs. Volume shipments start today.

In circuits such as inverters, where MOSFETs or IGBTs are used in series, gate voltage can be generated by a Miller current[1] when the lower arm[2] is turned off, causing malfunctions such as short circuits in the upper and lower arms[3]. A commonly used protection function to prevent this is the application of a negative voltage to the gate when it is turned off.

For some SiC MOSFETs, which commonly feature higher voltage, lower on-resistance and faster switching characteristics than silicon (Si) MOSFETs, sufficient negative voltage cannot be applied between the gate and source. In this case, an active Miller clamp circuit can be used to flow the Miller current from the gate to ground, preventing the short circuiting without the need to apply the negative voltage. However, there are cost-cutting designs that reduce the negative voltage applied to the gate when the IGBTs are turned off, and in these cases, gate drivers with a built-in active Miller clamp are an option for consideration.

The new product has a built-in active Miller clamp circuit, so there is no need for an additional power supply for negative voltage and external active Miller clamp circuits. This provides a safety function for the system and also promotes system miniaturization by reducing the number of external circuits. The active Miller clamp circuit has a channel resistance of 0.69Ω (typ.) and a peak clamp sinking current rating of 6.8A, making it suitable as a gate driver for SiC MOSFETs, which are highly sensitive to changes in gate voltage.

TLP5814H has an operating temperature rating of -40 to 125°C, achieved by enhancing the optical output of the infrared emitting diode on the input side and optimizing the design of the photo detector devices (photodiode arrays) to improve optical coupling efficiency. This makes it suitable for industrial equipment that require strict thermal management, such as photovoltaic (PV) inverters and uninterruptible power supplies (UPSs). Its propagation delay time and propagation delay skew are also specified in the operating temperature rating range. Its package, a small size SO8L, 5.85×10×2.1mm (typ.), helps improve the flexibility of parts layout on a system board. In addition, it features a minimum creepage distance of 8.0mm, allowing it to be used for applications requiring high insulation performance.

Toshiba will continue to develop photocoupler products that contribute to enhancing the safety function of industrial equipment.

Notes:

[1] Miller current: Electric current generated when high dv/dt voltage is applied to capacitance between the drain and gate of a MOSFET or between the collector and gate of an IGBT.

[2] The lower arm is the part that draws current from the load of a circuit that uses power devices, such as inverters in series to the negative power supply (or ground). The upper arm is the part that supplies current from the power supply to the load.

[3] Short circuited in the upper and lower arms: A phenomenon in which the upper and lower power devices turn on at the same time due to a malfunction caused by noise or the malfunction of power devices due to Miller current during switching.

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