| 摘要 |
PROBLEM TO BE SOLVED: To obtain a heater control circuit which is further improved in safety measure performance. SOLUTION: The heater control circuit 1 is a heater control circuit which detects the abnormality of the heater temperature and compulsorily switches off the supplied power supply and is constructed of, for example, a heater relay compulsory switch-off releasing circuit 10 and a phase control generating circuit 11. Furthermore, it comprises a counter for counting ON period of the relay and a memory function part for supporting the OFF state of the relay, and by comparing a counter value counted and a resister value for the compulsory switching-off which the system side sets, safety performance of heater control at the time of soft runaway is enhanced. Detection of existence of the soft runaway is made by whether the comparison matches or not, and the counter value is obtained by counting the ON period of the heater relay by a zero cross signal of the supplied power supply, and by comparing this counted counter value and the register value for compulsory switching-off set by the system side, and if they match, the compulsory switch-off function is released, thereby safety of heater control at the time of soft runaway can be further enhanced. COPYRIGHT: (C)2005,JPO&NCIPI
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