| 摘要 |
<p>PROBLEM TO BE SOLVED: To surely protect a CRT drive circuit from a damage by preventing transmission to the drive circuit when a synchronizing signal frequency exceeds an allowable range. SOLUTION: When frequencies of synchronizing signals H-SYNC, V-SYNC are in the allowable range, a switch part 130 of a protection circuit 140 transmits the synchronizing signals H-SYNC, V-SYNC outputted from a state signal generation circuit 110 to the CRT drive circuit 20. On the other hand, when the frequencies of the synchronizing signals H-SYNC, V-SYNC exceed the allowable range, a switch drive part 120 activates a switch drive signal SDRV in a prescribed time (where, a time required for that the frequency exceeding the allowable range restores to an original state) according to a state signal SBLK generated from the state signal generation circuit 110. The switch part 130 suppresses the transmission to the CRT drive circuit 20 by ground short- circuiting the synchronizing signals H-SYNC, V-SYNC according to this switch drive signal SDRV.</p> |
