| 摘要 |
PROBLEM TO BE SOLVED: To secure a thermal margin of a semiconductor switching element installed for driving a load without causing an increase in the size of the element. SOLUTION: In a state that a low-side LDMOS 16 is fully turned on, a current I1 does not flow and only a current I2 flows by the conductivity of a second diode circuit 22, since a drain voltage of the low-side LDMOS is almost zero and a first diode circuit 21 is held in a non-conductive state. When the current I2 flows, a gate voltage of the LDMOS 16 is lowered to "a voltage +Vf between a collector and an emitter of a bipolar transistor 18" (V is a voltage drop in a forward direction), to cause a rise of the drain voltage of the LDMOS 16, the first diode circuit 21 is brought into a conductive state according to the rise of the drain voltage, and thereby the current I1 is made to flow to the first diode circuit. By these operations, the drain voltage of the LDMOS 16 is fixed to "the gate voltage +3Vf of the LDMOS 16". COPYRIGHT: (C)2006,JPO&NCIPI
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