The four-pin TO-247-4L package, which uses Kelvin-connected signal-source terminals for gate drive, can reduce the effect of the inductances of the source wires inside the package, thereby further enhancing the high-speed switching performance of MOSFET chips.
This helps improve the efficiency of mid- and large-class high-efficiency switched-mode power supplies (equivalent to 80 PLUS of ※1 power TITANIUM/PLATINUM).
As DTMOS speeds and currents increase, the inductance components of the source wires inside the package affect the high-speed switchability of the package. By providing the signal source terminal for the gate drive, the current in the power line and the current in the gate drive line can be separated to reduce the influence of the inductance of the gate-source voltage.
For >3-pin packages (TO-247)
The back electromotive voltage VLS (=LS*dID/dt) is generated by the inductance component L Source of the source wire and the slope dI dID/dt of the drain current of the voltage VGS applied between the gate and the source of the FET chip. The actual applied voltage is reduced from the set gate voltage by this back electromotive force, and the switching speed, especially turn-on, is slowed down.
For >4-pin packages (TO-247-4L)
Moving the source terminal on the drive side from a location close to the FET chip separated from the source wire on the load side makes it less susceptible to the drive voltage. This makes it possible to improve the high-speed switching performance of the FET chip.
When we looked at the gate-source voltage waveforms in the immediate vicinity of MOSs, we confirmed that the on-time of TO-247-4L packages was shortened by the L Source. In the actual measurement, we confirmed that the turn-on loss of the TO-247-4L package (part number: TK62Z60X) was reduced by 19% compared with the turn-on loss of the TO-247 package (part number: TK62N60X).
Regarding the effect of reducing the turn-on loss, we confirmed that the switching speed was improved in both the simulation and the actual measurement.
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