JPH0472737B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a power supply circuit for in-vehicle audio equipment.

[Conventional technology]

Automotive audio equipment generally has an ignition
Power supply voltage is supplied from the vehicle's battery via the switch's accessory key (one position of the ignition switch).

[Problem that the invention seeks to solve]

Generally, when turning off the power of in-vehicle audio equipment, the power switch of each device is used to turn off the power.In addition, when the driver leaves the car, the power of the in-vehicle audio equipment is turned off by turning off the ignition switch. are often cut together. In this case, the power to the audio equipment that is in operation is suddenly cut off, which causes DC voltage fluctuations in the signal line within the equipment, resulting in transient noise. In order to prevent such noise, general audio equipment is equipped with a muting circuit, and muting is performed by keeping the power supply circuit active for a certain period of time even after the power switch is turned off.

On the other hand, if the in-vehicle audio equipment is turned off using the accessory key, the power will be suddenly cut off, so mutating should be done appropriately, taking into account the response speed of the muting circuit and the time delay in detecting that the accessory key has been turned off. That is difficult. Alternatively, the circuit that realizes this becomes expensive.

Furthermore, in modern cars, devices that consume large current such as electric mirrors, electric windows, and automatic door lock devices are often supplied with power via the accessory key. Lines often have large voltage fluctuations, which adversely affect the operation of audio equipment.

[Means for solving problems]

In order to solve the above-mentioned problems, the power supply circuit of the in-vehicle audio equipment of the present invention includes a switch circuit and an ignition circuit that are directly connected to the in-vehicle battery and directly supply the output voltage of the battery to the power supply circuit of the in-vehicle audio equipment. - The switch circuit is configured to be connected to the accessory position of the switch to close the switch circuit when the switch selection position is at the accessory position, and to open the switch circuit after a certain delay time has elapsed from the time when the switch is disconnected from the accessory position. and a muting circuit connected to the accessory position of the ignition switch to mute the audio equipment when the switch selection position is disconnected from the accessory position.

[Effect]

When the ignition switch is in the accessory position, the vehicle audio equipment is supplied with power directly from the battery via the switch circuit. When the selected position of the ignition switch is removed from the accessory position, the muting circuit applies muting to the audio equipment while continuing to supply power to the audio equipment for a while after switching, and after a certain period of time the audio equipment is muted. Cut off the switch circuit to cut off the power supply voltage to the audio equipment.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a power supply circuit of an on-vehicle audio device as an embodiment of the present invention. In Figure 1, the positive voltage (+B) terminal of battery 1 is
It is directly connected to the contact 21 of the relay 2 and connected to the audio power line of the audio device 3 via the contact 21, and is also connected to the delay circuit 5 and the audio device 3 via the accessory switch 4 built into the ignition switch. It is connected to a muting circuit 6 built into the internal circuit.

The delay circuit 5 includes a diode 51, resistors 52 and 53, a capacitor 54, and a transistor 55, and the transistor 55 is turned on and off by the charging/discharging terminal voltage of the capacitor 54. The emitter side of the transistor 55 is grounded, and the collector side is directly connected to the +B terminal of the battery 1 via the excitation coil 22 of the relay 2. Moreover, the muting circuit 6 includes a resistor 61,
62, transistors 63, 64, etc., and receives a mute signal when the accessory switch 4 is turned off, grounding the audio signal line of the audio equipment and performing muting.

The operation of the embodiment apparatus shown in FIG. 1 will be explained below.
When the ignition switch is in the accessory position, that is, when the accessory switch 4 is turned on, the capacitor 54 of the delay circuit 5 is charged via the diode 51 and the resistor 52, and the charging voltage causes the transistor 55 to be charged. is conducting. Therefore, an exciting current flows from the battery 1 to the coil 22 of the relay 2, and the contact 21 is closed. Therefore, the audio equipment 3 receives power supply voltage directly from the battery 1 via the relay contact 21. The diode 23 is a surge absorbing diode.

Accessories currently being used for ignition switches
When the switch 4 is turned off, the capacitor 54 in the delay circuit 5 gradually discharges its charge through the resistor 53, but for a certain period of time the transistor 55 remains on; During this time, the battery voltage continues to be supplied to the audio equipment 3 via the contact 21. On the other hand, when the accessory switch 4 is turned off, a mute signal is input to the muting circuit 6 and the audio equipment 3 is muted.

When a certain delay time determined by the time constant of each element of the delay circuit 5 has elapsed, the transistor 55 turns off, turning off the relay 2, thereby cutting off the supply of power supply voltage to the audio equipment 3. Since the audio equipment 3 is muted, no noise is generated. In this way, the first
In the device shown in the figure, power continues to be supplied to the audio equipment for a while even after the accessory switch 4 is turned off, and the muting operation is performed while the equipment is operating stably, and then the power to the audio equipment is turned off. Therefore, it is possible to easily and stably mute, and the generation of noise can be prevented.

Various modifications are possible in carrying out the invention. For example, the delay circuit in the above-described embodiment is not limited to this, and can be configured as shown in FIG. 2, for example, if a short delay time is sufficient. This circuit connects the capacitor 54 directly to the relay coil 22 and connects the accessory
After the switch 4 is turned off, the relay is driven for a certain period of time only by the charge in the capacitor 54. Further, it is also possible to use an electronic element such as a transistor in addition to the relay 2, and the muting circuit 6 is not limited to this, and various known circuits can be used.

〔Effect of the invention〕

According to the present invention, it is possible to prevent noise from being generated in a vehicle-mounted audio device even when the accessory key of the ignition switch is turned off while the audio device remains in operation.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a power supply circuit of an in-vehicle audio device as an embodiment of the present invention, and FIG. 2 is a diagram showing a modified aspect of the present invention. 1...Battery, 2...Relay, 3...Audio equipment, 4...Accessory switch, 5...
Delay circuit, 6...mutating circuit.

Claims (1)

[Claims] 1. A switch circuit that is directly connected to an on-vehicle battery and supplies the output voltage of the battery directly to a power circuit of an on-vehicle audio device, and a switch circuit that is connected to an accessory position of an ignition switch so that the switch selection position is connected to the accessory position. a delay circuit connected to the accessory position of the ignition switch and configured to close the switch circuit when the ignition switch is in the accessory position and open the switch circuit after a certain delay time from when it is disconnected from the accessory position; A power supply circuit for an in-vehicle audio device, comprising a muting circuit that mutes the audio device when the switch selection position is separated from the accessory position.