Abstract: A power module is provided with an insulating substrate with a heat sink being bonded to one surface thereof and a circuit pattern being formed on the other surface. The circuit pattern is formed by an electrode layer. A switching semiconductor element and a free wheeling diode that is connected to a switching semiconductor element in anti-parallel therewith are placed on the circuit pattern. A controlling IC for controlling the switching semiconductor element is placed on the free wheeling diode. Thus, it is possible to make the entire power module compact, and it becomes possible to provide an inexpensive power module which can prevent the controlling IC from malfunctioning due to heat generated by the switching semiconductor element.

Abstract: An inverter circuit to reduce a resistor for overcurrent detection and decrease the number of filters in an inverter circuit for supplying polyphase power. Transistors each having a current detection terminal and a protective diode for regenerative current are adopted as switching elements on an “L” side and their current detection terminals are connected in common to a resistor. Therefore, a voltage drop caused by a current flowing in the resistor becomes larger when an overcurrent flows in at least one of the transistors and further when an overcurrent flows in a switching element on an “H” side even if no overcurrent flows in any one of the transistors.

Abstract: Current sense voltages (VCSl˜VCSn), which are the detected values of n (≧2) IGBTs connected in parallel, are converted into digital form, and thereafter, are subjected to an operation processing. After the current sense voltages (VCSl˜VCSn) are converted into collector currents (Il˜In) by use of constants (Gl˜Gn and VOFFSETl˜VOFFSETn)(step 103), current deviations (&Dgr;Il˜&Dgr;In) respectively defined as differences of the collector currents (Il˜In) from the average (IAVG) thereof are calculated (step 104, 105). Drive control voltages (VDl˜VDn) are renewed by changes (&Dgr;VDl˜&Dgr;VDn) which are respectively obtained by multiplying the current deviations (&Dgr;Il˜&Dgr;In) by factors (Kij)(step 106, 107). The drive control voltage (VDl˜VDn) are converted into analogue form, and thereafter, supplied to n IGBTs as their gate voltages (VGE).

Abstract: A capacitive element is charged with no excessive flow of current so that a potential to effect the operation of a switching element can be obtained with stability. A capacitor (30) is charged with a circulating current from a load (40). On the charging path, a resistor (21) is provided in series to prevent an excessive flow of the charging current. Between terminals (V.sub.B, V.sub.S) of an upper-arm driving circuit (25) which receive a voltage to effect the operation of an IGBT (34) of an upper arm, the capacitor (30) and the resistor (21) are provided to suppress a decrease in potential (V.sub.B) at the terminal (V.sub.B).