A fast-switching intelligent power MOSFET with thermal protection and negative gate protection

Recently, thermal protection circuits have been added to power MOSFETs to improve their reliability. However, integrating a protection circuit into a power MOSFET causes parasitic bipolar transistors to form. These parasitic bipolar transistors cause a leakage that passes from the drain terminal to the gate terminal when a negative gate voltage is applied against a source voltage. Therefore, these MOSFETs cannot be used in a high-side switch circuit without some form of negative gate protection. To solve this problem, we proposed an intelligent power MOSFET with built-in thermal protection and negative gate protection, which we called the thermal FET. However, the switching speed of this MOSFET is fairly slow because it includes a gate resistor of about 5 to 10 k/spl Omega/ in its thermal shutdown circuit. Here, we describe a fast-switching intelligent power MOSFET whose switching speed is about two orders of magnitude faster than our previous thermal FET. This was achieved by replacing the gate resistor with a MOSFET. We also developed a new form of negative gate protection for the additional MOSFET. We call this highly reliable fast-switching intelligent power MOSFET an FS-Thermal FET. The FS-Thermal FET can be used in the upper arms of H-bridge circuits and high-side switch circuits, as well as in low-side switch circuits, with this new form of negative gate protection.