JPH075598Y2 - In-vehicle equipment current detection circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application This invention relates to a current detection circuit for an on-vehicle device.

(B) Conventional technology In a so-called booster-type radio switching unit, which has been conventionally used in combination with an on-vehicle audio device such as a car stereo, which is installed later, using a genuine radio installed in an automobile As the current detection circuit, for example, a current detection circuit as shown in FIG. 5 has been provided.

Since a voltage of about 12 [V] is applied to the terminals ACC1 and ACC2 of the current detection circuit 30 of the radio switching unit (not shown) from the battery (not shown), the relay 31 operates. , The contact circuit 32 of the relay 31 is closed.

When the power switch 34 of the genuine radio A (hereinafter referred to as radio) 33 shown in FIG. 6 is turned on, a voltage of about 12 [V] is generated by the parallel circuit composed of the diode 35 and the resistor 36 from the terminal ACC1 and the power switch. Power is supplied to the radio 33 via 34,
The radio is configured to be active.

A parallel circuit composed of the diode 35 and the resistor 36 is connected to the (+) input terminal and the (-) input terminal of the operational amplifier 37 of the current detection circuit 30 via the resistors 38 and 39, respectively, and further the operational amplifier 37 And the (+) input terminal are connected via a resistor 40 to form a comparator circuit, and the voltage at the point of the comparator circuit is compared with the voltage at the point.

In this case, as shown in FIG. 6, the threshold level SL of this comparator circuit is set to about 50 [mA] as the current value flowing in the parallel circuit of the diode 35 and the resistor 36.

Now, since the power switch 34 is turned on, a current of about 170 [mA] is supplied to the radio 33. The current causes a current difference between both ends of the parallel circuit of the diode 35 and the resistor 36, and the voltage at the point decreases with respect to the point. Then, the voltage at the point and the voltage at the point are input to the operational amplifier 37 via the resistors 38 and 39, and as a result, they are equal to or higher than the threshold level SL of the comparator circuit.
Output voltage decreases, and the transistor 41 is turned on.

As a result, a power of about 12 [V] is supplied from the collector of the transistor 41 to the rear-mounted amplifier 42 through the line 43, and the rear-mounted amplifier 42 is in an operating state, so that a desired broadcast can be heard. Become.

Next, when the power switch 34 of the radio 33 is turned off, the current consumption of the radio 33 becomes 0, so the diode 35 and the resistor 36
No current flows in the parallel circuit of, and therefore, the potential difference between the points is configured to be equal to or lower than the threshold level SL of the converter circuit, so that the output voltage of the operational amplifier 37 rises and the transistor 41 is turned off. Therefore, power is not supplied to the amplifier 42 that is installed later, and the amplifier 42 does not enter the operating state.

(C) Problems to be solved by the invention However, recently, in addition to the conventional genuine radio A or genuine radio B, electronically tuned models such as genuine radio C or genuine radio D shown in FIG. Models with built-in digital clocks have come to be used as genuine radios.

These models, even if the power switch of the genuine radio is turned off (shown as OFF in Fig. 6) as shown in the same figure,
For example, when a current that greatly exceeds the threshold level SL is constantly consumed for a timepiece display device, and the threshold level SL of the current detection circuit 30 is fixed to the conventional current value of about 50 (mA). However, the transistor 41 of the current detection circuit 30 is always on, and an unnecessary current is constantly supplied to the amplifier 42 or the like that is attached later.

This invention was made in view of the above points,
It is an object of the present invention to provide a current detection circuit for an in-vehicle device that enables sensitivity switching regardless of the current consumption of a genuine radio and can be used in combination with a rear-mounted car component. .

(D) Means for Solving the Problem The current detection circuit of the vehicle-mounted device according to the present invention is a vehicle-mounted acoustic system including a genuine radio mounted in the vehicle and a vehicle-mounted device such as a car stereo that is attached later. A current detection circuit for a vehicle, which comprises a rectifier, at least two resistors, and an external terminal for switching the detection sensitivity, and which is mounted later when mounted on a vehicle when the power switch of the genuine radio is off. The power supply to the equipment is cut off.

(E) Function According to the present invention, in the current detection circuit of the booster type vehicle-mounted acoustic system that is configured by the genuine radio installed in the vehicle and the vehicle-mounted device such as the car stereo that is installed later, Since an external terminal for switching the detection sensitivity is provided, even with a genuine radio of any current consumption, it is possible to cut off the power supply of the in-vehicle device such as a car stereo installed after the power switch of the genuine radio is off. it can.

(F) Embodiment An embodiment of the current detection circuit of the vehicle-mounted device according to the present invention will be described with reference to FIGS. 1 to 4.

1 is a circuit diagram of a current detection circuit, FIG. 2 (a) is a circuit diagram of an adapter having a resistor for switching the threshold level of the current detection circuit, and FIG. 2 (b) is a threshold of the current detection circuit. The circuit diagram of the adapter with a built-in resistor for switching the level and the circuit for the genuine radio with a clock display device. Fig. 3 shows the current detection circuit, the genuine radio, the cassette deck and the power amplifier installed later. FIG. 4 is a block diagram in which the above is combined, and FIG. 4 is a graph showing the relationship between the threshold level of the current detection circuit and the change in power consumption by turning on / off the power switch of the genuine radio.

First, the current detection circuit of FIG. 1 will be described.

A voltage of about 12 [V] from a battery (not shown) is applied to the terminals IN-B and ACC of the current detection circuit 1.

The terminal IN-B is connected so that power can be supplied to the operational amplifier 2 and the relay 3 can be driven. Further, the terminal IN-B is connected from the terminal AMP-B via the transistor 4 constituting the switching circuit, for example, after mounting. Is configured to supply power to a load such as an amplifier.

The terminal ACC has a first parallel circuit composed of resistors 6 and 7 for setting the current sensitivity and a second parallel circuit composed of resistors 8 and 9 for setting the current sensitivity via the contact circuit 5 of the relay 3. Via a current detection unit D configured by connecting a diode 10 in parallel to the serial circuit of a load of a genuine radio (not shown)
Is connected to a terminal TU-B for supplying power to.

Further, the terminals AD1 and AD2 are provided so that the resistance value of the first parallel circuit can be easily switched by adding an adapter.

The voltage detected by the current detection unit D by the current I of the load (not shown) connected to the terminal TU-B, that is, the voltage at the point and the voltage at the point are (-) of the operational amplifier 2 via the resistors 11 and 12. ) Input terminal and (+) input terminal respectively.

The output of the operational amplifier 2 and the (+) input terminal are resistors 13
The output of the operational amplifier 2 is configured to rise or fall depending on the magnitude of the potential difference between the points because the comparator circuit is connected via the.

Further, since the output of the operational amplifier 2 is connected to the base of the transistor 4, the transistor 4 can be switched depending on the magnitude of the potential difference between the points.

In the current detection circuit configured as described above, the terminal ACC and the terminal IN-B of the current detection circuit 1 are now about 1
Since the voltage of 2 [V] is applied, the relay 3 operates and the contact circuit 5 of the relay 3 closes.

Then, if a load is connected to the terminal TU-B, a current I corresponding to the load flows through the current detector D and a potential difference is generated between the points. The voltage between the points is input to the operational amplifier 2 via the resistors 11 and 12, so that if the threshold level of the comparator circuit composed of the operational amplifier 2 is significantly exceeded, the output voltage of the operational amplifier 2 drops and the transistor 4 is turned on. It is possible to supply a voltage of about 12 [V] to another load connected to the terminal AMP-B in the ON state.

Next, when the load is disconnected from the terminal TU-B, the current I of the current detection unit D becomes 0, and the potential difference between the points becomes less than the threshold level of the comparator circuit configured by the operational amplifier 2. The output voltage rises and the transistor 4 is turned off, so the terminal AMP-B
Is 0 [V] due to the resistance of 15, and power cannot be supplied to another load connected to the terminal AMP-B.

When changing the threshold level of the converter circuit, the terminals ad1, ad2, ad3 of the adapter A formed by the resistor 14 provided for switching the current detection sensitivity shown in FIG. , AD3 respectively, the resistance value of the portion corresponding to the first parallel circuit decreases due to the resistance 14 of the adapter A, so the potential difference between points decreases, and as a result, the threshold level of the comparator circuit rises. Then, the detection sensitivity has been switched.

Since the detection sensitivity of the current detector D can be arbitrarily set by switching the resistance value of the resistor 14 in this way, the state of the terminal AMP-B can be reliably controlled by the magnitude of the current I of the current detector D.

Next, an example in which the current detection circuit 1 is used in combination with a genuine radio, a cassette deck and a power amplifier, which will be installed later, will be described with reference to FIG.

Now, the genuine radio A with relatively low current consumption shown in Fig. 4
When listening to the radio on the radio (hereinafter referred to as 16) 16, the power switch (not shown) of the radio 16 is turned on. If the current consumption of the radio 16 exceeds the threshold level SL1 of the current detection circuit 1, about 12 [V]
The voltage of the diode 1 from the terminal AMP-B of the current detection circuit 1
7 and is added to the base of the transistor 18 of the cassette deck 20 and the base of the transistor 19 of the power amplifier 22.

Since a voltage of about 12 [V] is applied to the collectors of the transistors 18 and 19, the transistors 18 and 19 are turned on, and the amplifier 21 of the cassette deck 20 and the amplifier 23 of the power amplifier 22 have a voltage of about 12 [V]. Is added, the amplifiers 21 and 23 are in the operating state.

Then, the output 24 of the radio 16 passes through the signal attenuator 26 in the radio switching unit 25, is further amplified by the amplifiers 27, 21 and 23 and is guided to the terminal OUT so that a desired broadcast can be heard. On the other hand, when the power switch of the radio 16 is off, the terminal
Since AMP-B is 0 [V], the transistors 18 and 19 are not turned on, so that the amplifier 21 of the cassette deck 20 and the amplifier 23 of the power amplifier 22 do not operate and consume no power.

Next, a cassette (not shown) in the cassette deck 20
When set to, switches S1 and S2 in cassette deck 20
The terminal T and the terminal C are turned on. Since a voltage of about 12 [V] is applied to the bases of the transistors 18 and 19 via the diode 28, the amplifier 21 and the amplifier 23 are provided.
Becomes active again. Then, the signal of the magnetic head H is amplified by the amplifier 29, and further passes through the switch S1 and the amplifier 2
It is amplified by 1,23 and led to the terminal OUT.

Now, when combining the genuine radio E, which consumes more current than the genuine radio A as shown in FIG. 4, the cassette deck 20 and the power amplifier 22, the threshold level of the current detection circuit 1 should be SL2. The detection sensitivity of the current detection circuit 1 may be reduced. In this case, the adapter A shown in FIG. 2 (a) may be used, and if the resistance value of the resistor 14 of the adapter A is appropriately changed, it becomes like a genuine radio F. It is also compatible with genuine radios with even higher current consumption.

Further, for example, in the case of a genuine radio having a built-in clock display device and only the clock display device of the genuine radio is desired to be constantly operated, the adapter B shown in FIG. 2B is used, and the terminal AD1 of the current detection circuit 1 is used. , SD2, AD3 to the terminals of adapter B ad1, ad
If the clock display device (not shown) of the genuine radio is connected to terminals 2, ad3 and terminal ad3, the voltage of about 12 [V] is supplied to the power source of the clock display device without passing through the contact circuit 5 of the relay 3. Is applied from the terminal ad3, the clock display can be operated at all times, and the threshold level of the current detection circuit 1 can be set arbitrarily with the resistor 14. It is possible to control the power supply of.

The current detection circuit 1 has a hysteresis characteristic because of the resistor 13, so that the current detection circuit 1 does not malfunction even in an automobile in which the power supply changes a lot.

(G) Effect of the Invention According to the current detection circuit of the vehicle-mounted device of the present invention, a genuine radio of any current consumption can be used in combination with a vehicle-mounted audio device such as a cassette deck or a power amplifier to be mounted later.

Moreover, it has excellent features such as easy implementation because it can be constructed at low cost.

[Brief description of drawings]

1 to 4 show an embodiment according to the present invention.
Fig. 2 is a circuit diagram of the current detection circuit, Fig. 2 (a) is a circuit diagram of an adapter incorporating a resistor for switching the threshold level of the current detection circuit, and Fig. 2 (b) is switching the threshold level of the current detection circuit. Circuit diagram of an adapter with a built-in resistor to add a circuit for a genuine radio with a clock display device. Fig. 3 shows a combination of a current detection circuit, a genuine radio, a cassette deck and a power amplifier to be installed later. FIG. 4 is a block diagram, FIG. 4 is a graph showing the relationship between the threshold level of the current detection circuit and the change in current consumption due to the on / off state of the power switch of the genuine radio, and FIG. 5 is a circuit diagram of a conventional current detection circuit, and FIG. The figure is a graph showing the relationship between the threshold level of the conventional current detection circuit and the change in current consumption due to the on / off state of the power switch of the genuine radio. 1: current detection circuit, 2: operational amplifier 3: relay, 4: transistor 5: contact circuit 6,7,8,9,11,12,14,15,: resistor 10: diode ACC, TU−B, IN−B , AMP-B, AD1, AD2, AD3: Terminal A, B: Adapter ad1, ad2, ad3: Terminal

Claims (1)

[Scope of utility model registration request] 1. A current detection circuit for a vehicle-mounted acoustic system comprising a genuine radio mounted on a vehicle and a vehicle-mounted device such as a car stereo, which is mounted later, the current detection circuit including at least two rectifiers. An in-vehicle device comprising a resistor and an external terminal for switching the detection sensitivity, and when the power switch of the genuine radio is turned off, the power supply to the in-vehicle device to be installed later is cut off. Current detection circuit for equipment.