Pioneer Electronic Corporation

Kunihiro Miyata

Jun Honda

Kazuhiro Hayashi

Ryuichi Shinoda

Michitaka Fujita

A direct current voltages detecting circuit is provided for monitoring output voltage of the power amplifier. A direct current signal is produced when a direct current voltage is detected. A cutoff circuit responds to the direct current signal and renders an output stage of the power amplifier a cutoff state. A failure determining circuit is provided to respond to the direct current signal and to produce an abnormality signal. In response to the abnormality signal, a power supply cutoff circuit operates to cutoff a power supply of the power amplifier.

Protection circuit for a power amplifier

A protective apparatus for a power transistor which detects an abnormal temperature of a power transistor and cuts a load to the power transistor to prevent possible breakdown of the power transistor. The protective apparatus comprises detecting means which detects a junction temperature of the power transistor on the real time basis from a base-emitter voltage of the power transistor. When the junction temperature of the power transistor is excessively high, a protective circuit produces an output signal, and a muting circuit applies muting to an input signal to or a current flow through the power transistor.

Protective apparatus for power transistor

A karaoke device which automatically returns the level of a microphone volume to a presettled level at the beginning or end of individual music pieces, and which is capable of gradually reducing the gain of the microphone amplifier by a predetermined value when an output volume from the microphone amplifier becomes excessively loud during the playing of a music piece. The karaoke device includes an adjustor for adjusting the level of the microphone volume in accordance with a manual instruction or an instruction from a control circuit; a level detector for detecting when the volume level is greater than a predetermined level; a music piece detector for detecting a beginning or end of each music piece; and a control circuit that compares a standard volume level and the volume level of when a detected signal is outputted from the music piece detector, and controls the adjustor to equalize the output level to the previously stored standard level. According to the second aspect of the invention, a comparator compares the output level from the adjustor and a predetermined reference level to lower the output level until the music piece terminates.

Growing community of inventors

Tokyo, Japan

Kunihiro Miyata