| 摘要 |
PURPOSE:To improve the reliability for detecting a disconnection of a thin film type head by detecting a fact that a head terminal voltage rises and exceeds a prescribed threshold, and also executing a decision by detecting a fact that its exceeding time is longer than a prescribed time. CONSTITUTION:If a thin film type head is disconnected, when a signal a1 is in a high level, a transistor 10 cannot make a current flow out, and its emitter voltage b1 rises to about 0V. In the same way, when a signal a2 is in a high level, an emitter voltage b2 also rises to 0V. Accordingly, the time exceeding a threshold voltage C becomes long, and time of a high level of output signals d1, d2 of voltage comparators 15, 16 becomes long. Accordingly, at the time of rise of a pulse signal (f) of a pulse width Tw synchronizing with a rise of an output signal (e) of an OR circuit, the signal (e) is in a high level, and an output signal (g) of a D-type FF circuit 29 is set to a high level. The signal (g) is reset at the time of a low level of the output signal (e) of the OR circuit. In this way, a disconnection of a thin type head whose inductance is small can be detected exactly. |
