| 摘要 |
<p>PURPOSE:To increase the reliability of protective device, by using the signal in response to the temperature of moving coil and that in response to the amplitude of drive signal. CONSTITUTION:The signal from the input terminal 1 is fed to the moving coil Rs of the speaker SP via the amplifier 2 and the switch SW. The signal in response to the temperature change in the coil Rs is obtained by the bridge circuit BC taking this coil Rs as one side. This signal is fed to the adder ADD by forming the first signal in response to the temperature of the coil Rs via the LPF, and level adjuster VRt. Further, the signal from the switch SW is formed into the second signal in response to the amplitude of the drive signal of speaker via the variable resistor VR and fed to the adder ADD. Further, the output of the adder is given to the memory section MA, and when the first and seceon signals exceed a given signal level respectively, the control section CC is operated and the drive signal is interrupted with the switch SW. Thus, the reliability of the protective device can be increased.</p> |
