| 摘要 |
<p>1415476 Loudspeaker protection circuits BELTEK CORP 19 July 1973 [26 July 1972 2 Sept 1972] 34338/73 Heading H4J [Also in Division H2] A protective circuit for a loudspeaker SP and final stage transistors Q 6 , Q 7 of its amplifier has a relay with its contacts LS connected between the loudspeaker and amplifier output point P and its coil LC controlled by transistor means Q 4 connected to a time constant circuit including a capacitor C 1 , arranged so that there is a time lapse of preassigned time following closure of a power switch SW 1 before transistors Q 4 and Q 5 to energize the relay coil LC to close contacts LS; the capacitor C 1 having discharged to render Q 4 and Q 5 non-conductive so as to deenergize the relay coil LC either by an overcurrent detector circuit including a transistor Q 1 or by a D.C. voltage detector circuit with transistors Q 2 , Q 3 . The transistor Q 5 may be omitted when an additional diode is provided to effect rapid capacitor discharge on opening of the power switch, and an avalanche diode is connected between point b and the transistor Q 4 (Fig. 2, not shown). The overcurrent circuit may be arranged so that as transistor Q 1 becomes conductive on overload it makes a further transistor (Fig. 3, not shown) conductive to discharge the capacitor through a thyristor provided with a resetting switch. The voltage setting of the transistor Q 3 may be due to a Zener diode (Fig. 4, not shown).</p> |
