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JPH0558500

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DESCRIPTION JPH0558500
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
car stereo having a grill main body detachably mounted to an equipment main body, and the
equipment main body side exposed when the grill main body is removed from the equipment
main body The present invention relates to a car stereo adapted to prevent a short circuit at a
terminal of a connector of
[0002]
2. Description of the Related Art As a means of preventing theft accompanying the upgrading of
audio equipment such as car stereos, a grille body of a detached type has been commercialized.
This is intended to make it impossible to recognize the presence of the acoustic device by
removing the grill body from the device body when leaving the vehicle.
[0003]
FIGS. 1 and 2 show an example of such a detachable type car stereo, in which a grill main body
20 is detachably provided to an apparatus main body 10 embedded in a dashboard or the like of
a vehicle. There is. The fitting body 11 is provided with a fitting recess 11 for fitting the grill
body 20. A connector 12 is provided on the right side in the fitting recess 11.
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[0004]
A shutter 13 is slidably provided in the vicinity of the connector 12. By sliding the shutter 13 to
the closing side, each terminal described later in the connector 12 can be covered.
[0005]
A cassette insertion hole 14 is formed near the center of the fitting recess 11.
On the left side of the cassette insertion hole 14, a detachment detection switch 15 for detecting
the detachment of the grill body 20 is provided.
[0006]
The connector 12 is provided with a 5V power supply terminal 12a, a data input / output
terminal 12b, an 8V power supply terminal 12c, and a ground terminal 12d. A 5V power supply
circuit 17 and an 8V power supply circuit 18 are connected to the 5V power supply terminal 12a
and the 8V power supply terminal 12c. A microcomputer (hereinafter referred to as a
microcomputer) 19 is connected to the data input / output terminal 12 b.
[0007]
On the rear side of the grill body 20, a connector 21 connected to the connector 12 on the device
body 10 side is provided. Below the front surface side of the grill body 20, various function
buttons 22 such as a preset button are provided. At the middle stage on the front surface side of
the grill body 20, a display unit 23 for displaying information such as time and reception
frequency is provided. In the upper stage on the surface side of the grill body 20, a cassette
insertion port 24 communicating with the cassette insertion hole 14 on the device body 10 side
when the grill body 20 is mounted is formed.
[0008]
The connector 21 is provided with a 5V power supply terminal 21a, a data input / output
terminal 21b, an 8V power supply terminal 21c, and a ground terminal 21d corresponding to the
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respective terminals on the connector 12 side.
[0009]
A microcomputer 25 is connected to the 5V power supply terminal 21a and the data input /
output terminal 21b.
The microcomputer 25 sends out a control signal instructing to display information such as time
and reception frequency according to the operation mode of the various function buttons 22. The
display driver 26 controls the display operation of the display unit 23 based on the control signal
from the microcomputer 25. An illumination lamp 27 is connected to the 8V power supply
terminal 22c.
[0010]
In the car stereo having such a configuration, when the grill main body 20 is attached to the
apparatus main body 10, the attachment / detachment detection switch 15 is turned on, and the
microcomputer 19 detects this to judge the attachment of the grill main body 20. Is done.
[0011]
When the microcomputer 19 recognizes the attachment of the grill body 20, predetermined
control data is sent out to the data input / output terminal 12b.
[0012]
At this time, the connector 21 on the grill main body 20 side is connected to the connector 12 on
the device main body 10 side by mounting the grill main body 20, and 5 V is applied to the
microcomputer 25 on the grill main body 20 side through 5 V power supply terminals 21a and
12a. Drive power is supplied.
After receiving the drive power of 5 V, the microcomputer 25 performs a reset operation, and
then receives control data from the microcomputer 19 via the data input / output terminals 12b
and 21b, and based on this data, performs a predetermined operation on the display driver 26.
Or to
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[0013]
At this time, 8 V drive power is supplied to the 8 V power supply terminal 12c. For example,
when the lamp light switch (not shown) of the vehicle is on, the illumination lamp 27 is driven at
8 V drive power. Receive points.
[0014]
On the other hand, when the grill body 20 is removed from the device body 10, the detachment
detection switch 15 is turned off.
When the microcomputer 19 detects the off state of the detachment detection switch 15, the
transmission of control data to the data input / output terminal 12b is stopped.
As described above, since the control data is not sent to the microcomputer 25 side, the data
input / output terminal 12b on the connector 12 side and the data input / output terminal 21b
on the connector 21 side are erroneously contacted after the grill main body 20 is removed. Even
in this case, erroneous display or the like by the display unit 23 is prevented.
[0015]
Also, since the respective terminals in the connector 12 can be covered by sliding the shutter 13
to the closing side after removing the grille main body 20 from the apparatus main body 10,
electric shock or short circuit is prevented. It has become too.
[0016]
FIG. 3 shows another example of the detach type car stereo, and a protection circuit 16 is
provided inside the device body 10.
The protection circuit 16 is interposed between the 5V power supply terminal 12 a and the 8V
power supply terminal 12 c and the 5V power supply circuit 17 and the 8V power supply circuit
18.
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[0017]
When a short circuit occurs between the 5V power supply terminal 12a and the other terminal
or the 8V power supply terminal 12c and the other terminal, the microcomputer 19 detects the
short circuit and immediately drives the protection circuit 16 to 5V. The supply of power from
the power supply circuit 17 and the 8V power supply circuit 18 is cut off.
[0018]
As a result, even if one of the terminals on the side of the apparatus main body 10 to be exposed
is accidentally shorted or static electricity is generated on any of the terminals, the protection
circuit 16 is immediately driven, Damage to the internal circuit of the power device body 10 is
prevented.
[0019]
As described above, in the above-described conventional car stereo, after the grill main body 20
is removed from the device main body 10, the shutter 13 is slid to the closing side to make each
terminal in the connector 12 By covering the terminal, electric shock or short circuit is
prevented.
[0020]
In another car stereo, the protection circuit 16 is provided on the device body 10 side, and when
the microcomputer 19 detects a short circuit generated between any of the terminals, the
protection circuit 16 is immediately driven to supply a 5 V power supply circuit. The power
supply from the 17V and 8V power supply circuits 18 is shut off to prevent the internal circuit of
the device body 10 from being damaged.
[0021]
However, in the former car stereo, since the shutter 13 is provided slidably to prevent electric
shock or short circuit, etc., in the case of a car stereo with many restrictions such as size, the
shutter at the design stage It is extremely difficult to determine the location of the location 13 or
the location of the slide mechanism for sliding the shutter 13.
In addition, since it is necessary to provide the shutter 13 in a slidable manner, parts etc. for
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making the same slidable are also needed, and the number of parts is increased, resulting in a
drawback that the cost of the car stereo is increased.
Furthermore, the shutter 13 has many structures that can be manually opened and closed from
the viewpoint of cost etc., not only is the opening and closing operation of the shutter 13
troublesome, there are many forgetting to close the shutter 13, and it can not fulfill its original
purpose such as short circuit prevention. There are many.
[0022]
On the other hand, in the latter car stereo, although the protection circuit 16 provided on the
device body 10 side prevents damage to the internal circuit of the device body 10, the
construction focused on the prevention of damage to the internal circuit. As a result, the
prevention of short circuiting of the terminals is still not improved.
Further, since the protection circuit 16 is provided, the circuit configuration on the device body
10 side is complicated, and the cost of the car stereo is still increased as described above.
[0023]
The present invention has been made to cope with such a situation, and has a simple
configuration, and when the grill main body is removed from the device main body side,
predetermined driving power and data of the device main body side are output. An object of the
present invention is to provide a car stereo capable of performing reliable short circuit
prevention by setting voltages or terminal states of a plurality of terminals for output to 0 V or
an open state.
[0024]
[Means for Solving the Problems] In order to achieve the above object, the present invention is
directed to a car stereo having a grill main body detachably attached to an equipment main body,
in the above-mentioned equipment main body side. Desorption detection means for detecting
desorption of a grill body, a plurality of terminals for outputting predetermined drive power and
data to the grill body side, and supply restriction means for limiting supply of drive power and
data to these terminals The supply limiting means blocks the output of drive power and data to
the plurality of terminals when the detachment of the grille body is detected by the desorption
detection means.
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[0025]
In the car stereo according to the present invention, when the grill main body is removed from
the main body of the device, it is intended to completely prevent a short circuit between a
plurality of exposed terminals due to its construction. . When the detachment of the grille body is
detected by the detachment detection means, the output of drive power and data to a plurality of
terminals is blocked by the supply limiting means
[0026]
Therefore, at the time of detachment of the grill main body, the voltage and terminal states of the
plurality of terminals on the device main body side can be 0 V or open state, and further 0 V or
open state, which is conventionally required. It is also unnecessary to use a shutter for covering a
plurality of terminals on the device body side, a slide mechanism for sliding the shutter, and a
protective circuit for preventing damage to the internal circuit when a short circuit occurs. it can.
[0027]
Embodiments of the present invention will be described below in detail with reference to the
drawings.
In the drawings described below, the same reference numerals are given to parts common to
FIGS.
[0028]
FIG. 4 shows the internal structure of the device body 10 according to the car stereo of the
present invention, and the connector 12 has a 5V power supply terminal 12a, data input / output
terminals 12b and 12e, and an 8V power supply terminal 12c. It is done.
The 5 V power supply terminal 12 a and the 8 V power supply terminal 12 c are connected to
the microcomputer 19 via the power supply limiting circuits 30 and 40.
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[0029]
The data input / output terminals 12b and 12e and the detachment detection switch unit 15A are
also connected to the microcomputer 19.
[0030]
The detachment detection switch unit 15A is provided with a pull-up resistor 15a and a resistor
15b.
The detachment detection switch unit 15A adopts a voltage value method, and the
microcomputer 19 can recognize the detachment of the grill body 20 based on the change in the
voltage value of the detachment detection switch unit 15A.
In addition, in the detachment detection switch unit 15A, not only the voltage value system but
also the mechanical detachment detection switch 15 as shown in FIG. 1 may be adopted.
[0031]
The microcomputer 19 is provided with a detachment detection unit 19a for detecting the
detachment of the grill main body 20 by the voltage value change of the detachment detection
switch unit 15A.
The detection result of the attachment / detachment detection unit 19a is taken into the CPU
19b.
[0032]
The CPU 19b transmits predetermined data to the data input / output terminals 12b and 12e
through the data transmission switching unit 19c, or the connector 12 when the grill main body
20 is removed from the apparatus main body 10 with respect to the control unit 19d. And sends
out a control signal for setting the input / output terminal voltage of each terminal to 0V or open.
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[0033]
The data transmission switching unit 19c is provided with switches 19e and 19f which are
turned on / off based on a control signal from the control unit 19d.
A resistor 51 and a diode 52 are interposed in the data line 50.
[0034]
The power supply limiting circuit 30 is provided with a transistor 31, and a reference power
supply (5 V) is supplied to the collector side.
A transistor 32 for limiting a bias current is interposed between the collector and the base of the
transistor 31. Connected to the base of the transistor 31 is a zener diode 33 that generates a
constant voltage when a bias current is supplied.
[0035]
Connected to the base side of the transistor 32 is a transistor 34 for limiting the base current of
the transistor 32. The control unit 19 d is connected to the base of the transistor 34.
[0036]
When the transistor 34 is turned on, for example, by the control signal from the control unit 19d,
the base current of the transistor 32 is reduced and the transistor 32 is turned off. As a result, no
bias current flows between the collector and the base of the transistor 31, and the transistor 31
is turned off.
[0037]
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The power supply limiting circuit 40 is provided with a transistor 41, and a reference power
supply (8 V) is supplied to the collector side. Connected to the base of the transistor 41 is a
transistor 42 for limiting the base current of the transistor 41. The control unit 19 d is connected
to the base side of the transistor 42. Then, when the transistor 42 is turned on by the control
signal from the control unit 19 d, the base current of the transistor 41 decreases and the
transistor 41 is turned off.
[0038]
In the figure, reference numerals 35 and 43 denote pull-down resistors, respectively.
Subsequently, the operation of the car stereo having such a configuration will be described with
reference to FIG. First, when the grill body 20 is attached to the device body 10, the voltage value
of the attachment / detachment detection switch unit 15A decreases, whereby the attachment /
detachment detection unit 19a detects attachment of the grille body 20 (step 501). Then, the
detachment detection unit 19a sends out a detection signal indicating attachment of the grill
body 20, whereby the CPU 19b recognizes the attachment.
[0039]
When the CPU 19b recognizes the attachment of the grill body 20, after performing the terminal
setting processing at the time of attaching the grille, the grill state is set to "ON" and a control
signal for instructing the "ON" state is sent. After outputting to the control unit 19d, the
operation shifts to the normal operation (steps 502 to 504).
[0040]
That is, when the control unit 19d sends an off signal to the power supply limiting circuits 30,
40, the transistors 31 and 41 are turned on by the reverse operation.
As a result, the terminal voltages of the 5V power supply terminal 12a and the 8V power supply
terminal 12c are raised to 5V and 8V, respectively (that is, in the "H" state).
[0041]
In data transmission switching unit 19c, both switches 19e and 19f are turned on based on the
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control signal from control unit 19d, whereby both data input / output terminals 12b and 12e
are in the active state. (In other words, it becomes "H" state).
[0042]
On the other hand, when the grill body 20 is detached from the apparatus body 10, the voltage
value of the detachment detection switch unit 15A rises to the voltage between the terminals of
the pull-up resistor 15a, so that the detachment detection unit 19a is released Is detected (step
501).
Then, the detachment detection unit 19a sends out a detection signal indicating detachment of
the grill body 20, whereby the CPU 19b recognizes the detachment.
[0043]
When the CPU 19b recognizes the detachment of the grill body 20, after performing the terminal
setting processing at the time of detachment of the grille, the grille state is set to "decoupled",
and the control signal for instructing this "decoupled" state is controlled. It outputs to the part
19d (steps 505 and 506).
[0044]
That is, when the control unit 19d sends the on signal to the power supply limiting circuits 30,
40, the transistors 31, 41 are turned off by the above-described operation.
As a result, the terminal voltages of the 5V power supply terminal 12a and the 8V power supply
terminal 12c are lowered to 0 V (that is, they are brought into the “L” state).
[0045]
In data transmission switching unit 19c, both switches 19e and 19f are turned off based on the
control signal from control unit 19d, whereby data input / output terminals 12b and 12e are "L"
and respectively. "Open"
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[0046]
As described above, in the present embodiment, when the detachment detection unit 19a detects
the detachment of the grill main body 20 by the decrease of the voltage value of the detachment
detection switch unit 15A and the CPU 19b recognizes the detachment, the control unit 19d A
control signal is sent to the power supply limiting circuits 30, 40 and the data transmission
switching unit 19c.
Thus, the terminal voltages of the 5V power supply terminal 12a and the 8V power supply
terminal 12c are set to "L", and the terminal voltages or terminal states of the data input / output
terminals 12b and 12e are set to "L" and "open state". .
[0047]
Therefore, since no voltage is applied to the terminals on the side of the device body 10 when the
grill body 20 is detached, a short circuit does not occur even if the terminals are touched by
mistake. In addition, since each terminal on the device body 10 is not applied with a voltage, the
shutter 13 for covering each terminal on the device body 10, which is conventionally required,
and a slide mechanism for sliding the shutter 13, The protective circuit 16 or the like for
preventing damage to the internal circuit when a short circuit occurs is also unnecessary.
[0048]
As a result, the structure of the device body 10 can be simplified, and reliable short circuit
prevention can also be performed.
[0049]
As described above, according to the car stereo of the present invention, when the grill body is
detached, the voltage or the state of the terminals of the plurality of terminals on the device body
side is 0 V or an open state. And a shutter for covering a plurality of terminals on the device main
body side conventionally required, a slide mechanism for sliding the shutter, and a protection
circuit for preventing damage to the internal circuit when a short circuit occurs. Since the need
for etc. is eliminated, a short circuit can be reliably prevented, and the configuration of the device
body is simplified, so that the cost can be reduced.
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