| 摘要 |
<P>PROBLEM TO BE SOLVED: To protect a protective transistor from thermal damages, without fail, while suppressing unnecessary overheat detection with respect to the protective transistor. <P>SOLUTION: When the temperature of the diode 3 detected becomes higher than a protection control start temperature, the forward voltage Vf of the diode 3 becomes lower than the threshold voltage Vth of a threshold-producing circuit 13 and a comparator 9 outputs an overheat-detecting signal of L level, while an MOSFET (metal oxide semiconductor field effect transistor) 2 goes into a current cut-off state. A first threshold correcting circuit 14 raises the threshold voltage Vth thereof to be higher, the larger current IL which flows through the MOSFET 2 becomes. A power supply voltage VB becomes higher, the higher a second threshold correcting circuit 15 raises the threshold voltage Vth thereof. The higher a third threshold correcting circuit 16 of the threshold voltage Vth thereof becomes, the higher the surrounding environmental temperature of an IC (integrated circuit) 11 becomes. <P>COPYRIGHT: (C)2010,JPO&INPIT |
