JPS637993Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a cassette car stereo that is equipped with a power lead terminal and a power supply terminal for external equipment, and also has a built-in tape playback circuit and FM reception circuit.
In particular, it relates to improvements in the power supply switching circuit.

As shown in Figure 1, conventional commercially available FM
The cassette car stereo 1 with a built-in receiver has a power lead terminal 3 for supplying power to the AM receiver 2 that is already installed in the car as a genuine device.
is provided, and is connected from the power supply terminal 4 on the cassette car stereo 1 side through the power lead terminal 3.
Power is supplied to AM receiver 2.

That is, the conventional cassette car stereo 1 has a second
As shown in the figure, it includes a power lead terminal 3 for an external device (AM receiver), a power supply terminal 4 that receives power from a car battery, a speaker terminal 5, an antenna terminal, a tape playback circuit 6, an FM reception circuit 7, It has a built-in output amplification circuit 8 that amplifies the tape playback signal and the FM reception signal, and when the cassette is installed, a pair of movable pieces 9 and 9' come into contact with the tape side terminals Ta and Ta', and when the cassette is removed, a pair of movable pieces 9 and 9' come into contact with the tape side terminals Ta and Ta'. Movable pieces 9 and 9' connect radio side terminals Ra and
Tape/radio selector switch S1 in contact with Ra′
Further, the pair of movable pieces 9 and 9' of the tape/radio changeover switch S1 are connected to the radio side terminal.
A selection switch S2 is provided for selectively operating the FM receiving circuit 7 or an external AM receiver when switching to Ra and Ra'. Therefore, in such a conventional car stereo, when the cassette is attached and the tape/radio selection switch S1 is switched to the tape side, the power from the power supply terminal 4 is transferred to the movable part of the tape/radio selection switch S1. 9
Power is supplied to the tape playback circuit 6 through the tape playback circuit 6 through the movable pieces 9 and 9', and the tape playback signal from the playback head 10 is amplified by the output amplification circuit 8 and played back by the speaker. It's summery. And at this time, the FM receiving circuit 7
Since power is not supplied to the external AM receiver 2 and the external AM receiver 2, priority is given to the tape playback operation.

Next, when the cassette is removed and the tape/radio selector switch S1 is switched to the radio side,
Power from the power supply terminal 4 is supplied to the common terminal of the selection switch S2 through one movable piece 9, and when the movable piece 11 of the selection switch S2 is switched to the FM side terminal FM, the power is supplied to the FM receiving circuit 7. At the same time, the tape/radio selector switch S1
It is configured to supply power to the output amplification circuit 8 through the other movable piece 9'.

Therefore, when the tape/radio selection switch S1 is switched to the radio side and the movable piece 11 of the selection switch S2 is switched to the FM side terminal FM,
The FM reception signal can be heard on the speaker through the output amplification circuit 8, and the selection switch S
When the movable piece 11 of 2 switches to the AM terminal AM,
It is configured to cut off the power supply to the FM reception circuit 7 and the output amplification circuit 8 and at the same time supply power to the AM receiver as an external device, thereby putting the external AM receiver into an operating state.

According to such a conventional car stereo, the tape/radio selector switch S1 has a pair of movable pieces 9 and 9'.
Since a two-circuit type device is required, the shape of the switching switch S1 becomes large, which is undesirable for car stereos that require miniaturization, as space is restricted.

The present invention was proposed in view of the above, and it is possible to convert the tape/radio selector switch into a single circuit having one movable piece by electrically switching the output amplification circuit to activate or deactivate it. The switch can be configured with a small type, and the changeover switch is made smaller, making it suitable for small car stereos with limited space.

The car stereo of the present invention has a circuit configuration as shown in FIG. 3, and the same parts as the conventional circuit shown in FIG. 2 are given the same numbers.

The tape/radio selector switch S3 of the present invention has one movable piece 12, the common terminal 13 of which is connected to the power supply terminal 4 and the power line of the output amplifier circuit 8, and the tape side terminal Ta is connected to the tape side terminal Ta. It is connected to the power supply line 14 of the reproduction circuit 6, and the radio side terminal Ra is connected to the common terminal 15 of the selection switch S2.
It is connected to the. The FM side terminal FM of the selection switch S2 is connected to the power supply line 16 of the FM receiving circuit 7, and the AM side terminal AM is connected to the power supply lead terminal 3 for external equipment. A control transistor 17 controls an amplification transistor (not shown) of the output amplification circuit 8, and its base is connected via a resistor 18 to the AM side terminal AM of the selection switch S2. The control transistor 17 is set to render the output amplifier circuit 8 inactive when it is conductive.

Since the present invention has the circuit configuration as described above, when a cassette is attached and the tape/radio selector switch S3 is switched to the tape side, power from the power supply terminal 4 is supplied to the output amplifier circuit 8. At the same time, the signal is supplied to the tape reproducing circuit 6 through the movable piece 12 of the tape/radio selector switch S3.
In this case, since no control voltage is applied to the base of the control transistor 17, it is non-conductive, and the output amplifier circuit 8 is in an operating state, so that the tape playback signal from the playback head 10 is transmitted to the output amplifier circuit 8. It can be amplified and played through a speaker.

Next, when the cassette is removed and the tape/radio selector switch S3 is switched to the radio side,
Power from the power supply terminal 4 is supplied to the common terminal 15 of the selection switch S2 through the movable piece 12, and simultaneously supplied to the output amplifier circuit 8, and the movable piece 19 of the selection switch S2 is switched to the FM side terminal FM. Since power is sometimes supplied to the FM reception circuit 7, the FM reception signal can be heard through the output amplifier circuit 8 through the speaker. When the movable piece 19 of the selection switch S2 is switched to the AM side terminal AM, the power supply to the FM receiving circuit 7 is cut off, and at the same time power is supplied to the AM receiver as an external device. can be brought into operation. At this time, since a control voltage is applied to the base of the control transistor 17, the control transistor 17 becomes conductive, and the output amplifier circuit 8 is in an inactive state.

Therefore, when the AM receiver is operating, the output amplifier circuit on the car stereo side is in an inactive state due to electrical switching, so no noise signal is generated from the speakers on the car stereo side.

Since the present invention is configured as described above,
Unlike conventional tape/radio selector switches that required two circuits, the power supply circuit can be switched using a single-circuit tape/radio selector switch, which saves space by using a small switch. This makes it practical for use as a cassette car stereo with radio, which requires a small size.

[Brief explanation of drawings]

Figure 1 shows a cassette car stereo with an FM receiver.
Figure 2 is a schematic circuit configuration diagram of a conventional cassette car stereo with an FM receiver, and Figure 3 is a schematic circuit diagram of the cassette car stereo with an FM receiver according to the present invention. be. 3...Power lead terminal, 4...Power supply terminal,
6... Tape playback circuit, 7... FM reception circuit, 8
...output amplification circuit, S3...tape/radio selection switch, S2...selection switch, 17...control transistor.

Claims (1)

[Scope of utility model registration request] A cassette car stereo is equipped with a power lead terminal for external equipment and a power supply terminal, and also has a built-in tape playback circuit and an FM reception circuit.A common terminal is connected to the power supply terminal, and when the cassette is installed, the tape playback circuit is When the power is supplied and the cassette is removed, the FM
Tape that supplies power to the receiving circuit or external equipment.
a radio selector switch; a common output amplification circuit that is operated by operating voltage from a common contact of the tape/radio selector switch and amplifies the signals of the tape playback circuit and the FM receiver circuit; A cassette car stereo with a radio, comprising a control transistor that disables the output amplification circuit when switched to supply power.