JP3501856B2 - Voltage drop guarantee circuit for in-vehicle camera - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an in-vehicle camera,
The present invention relates to a voltage drop guarantee circuit that guarantees a voltage drop when power is supplied to a vehicle-mounted camera. 2. Description of the Related Art Conventionally, for example, vehicles such as trucks and buses are equipped with a camera behind the vehicle body, and an image is displayed on a monitor installed in a driver's cab based on a video signal output from the camera. There is known a television system such as a rear confirmation device that outputs a signal to secure a view behind the vehicle body. Generally, a camera in such a television system supplies power from a battery from a monitor and outputs a video signal from the camera to the monitor. However, in such a television system, since power from a battery is supplied to a camera behind the vehicle body by a cable or the like, wiring is performed along a vehicle body panel having a complicated shape or assembly so as not to be exposed to the outside as much as possible. In some cases, a voltage drop has occurred due to the cable routing, and a sufficient voltage for driving the camera cannot be obtained. Therefore, as shown in FIG. 2, the voltage supplied to the camera through the voltage control circuit 1 on the monitor side and the reference voltage are compared by the voltage detection circuit 2, and the comparison result is sent to the error signal circuit 3. Monitor side error detection circuit 4
And a voltage drop guarantee circuit that raises the power supply voltage supplied from the voltage control circuit 1 to the camera 5 based on the voltage guarantee signal output from the error detection circuit 4. As shown in FIG. 3, a voltage detection circuit 2 is provided on the camera side, and its error signal is superimposed on a power supply via an error signal output circuit 6, an error signal modulation circuit 7, and an error signal superposition circuit 8. To the monitor side, and performs error detection through an error signal extraction circuit 9, an error signal demodulation circuit 10, and an error signal detection circuit 11 on the monitor side. Based on the detection result, the voltage control circuit 1 changes the voltage to the constant voltage circuit 1
A voltage drop guarantee circuit that raises the power supply voltage supplied to the camera 5 via the camera 2 has also been considered. [0007] In the voltage drop guarantee circuit shown in FIG.
Is superimposed on the same line, and the video signal extraction circuit 14 on the monitor extracts the superimposed video signal and outputs an image to the monitor. [0008] By the way, a voltage drop guarantee circuit for a vehicle-mounted camera configured as described above, for example,
The voltage drop guarantee circuit shown in FIG. 2 requires a dedicated signal line for feeding back the error signal to the monitor side, which causes a problem that the cost rises, and the voltage drop guarantee circuit shown in FIG. In this case, not only the circuit configuration becomes complicated and the cost rises, but also the monitor body and the camera body become large in size. SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and not only can a dedicated signal line be unnecessary, but also an in-vehicle vehicle having a simple circuit configuration and realizing inexpensive size. An object of the present invention is to provide a voltage drop guarantee circuit for a camera. [0010] In order to achieve the object, the invention according to claim 1 is a camera mounted on a vehicle body, a power supply means for supplying power to the camera, and the camera. Voltage detection means for comparing the supply voltage supplied to the power supply with a preset reference voltage and outputting the comparison result;
Muting means for muting at least a synchronization signal of a video signal output from the camera based on a comparison result of the voltage detection means, and synchronization signal detection means for detecting a synchronization signal of a video signal output from the camera. ,
The gist of the invention is to include a control means for adjusting a voltage supplied to the camera based on an output signal from the synchronization signal detection means. According to the first aspect of the present invention, the camera is mounted on the vehicle body, the power is supplied to the camera by the power supply means, and the supply voltage supplied to the camera by the voltage detection means is determined in advance. The set reference voltage is compared with the set reference voltage, and the comparison result is output. At least the synchronization signal of the video signal output from the camera is muted by the muting means based on the comparison result of the voltage detection means. The synchronization signal of the video signal output from the camera is detected based on the means, and the voltage supplied to the camera is adjusted by the control means based on the output signal from the synchronization signal detection means. Next, an embodiment of a voltage drop guarantee circuit for a vehicle-mounted camera according to the present invention will be described with reference to the drawings. In FIG. 1, a voltage drop guarantee circuit 20
A monitor is provided as power supply means for supplying power to a camera mounted on a vehicle body such as a large truck or a bus (not shown). The monitor is supplied with power from a battery. On the camera side of the voltage drop guarantee circuit 20, a voltage detection circuit 21 for comparing a supply voltage supplied from the monitor to the camera with a preset reference voltage and outputting the comparison result, A muting circuit 22 for muting a synchronization signal of a video signal output to a monitor based on a comparison result of the detection circuit 21; On the other hand, on the monitor side of the voltage drop guaranteeing circuit 20, a synchronizing signal for detecting the synchronizing signal of the video signal output from the camera via the muting circuit 22 and outputting the video signal to an image reproducing circuit (not shown). Detection circuit 23
And a control circuit 24 for adjusting the voltage supplied to the camera based on the output signal from the synchronization signal detection circuit 23. The control circuit 24 includes the oscillation circuit 2
5, a counter circuit 26 to which an oscillation frequency from the oscillation circuit 25 and a stop signal from the synchronization signal detection circuit 23 are inputted, and a rising stop signal from the counter circuit 26 being inputted, and being electrically connected to the battery. A voltage step-up circuit 27 is provided for supplying power supplied from the battery to the camera. In the above configuration, when a main switch (not shown) is turned on, power from the battery is supplied to the camera via the voltage step-up circuit 27. The power supplied to the camera is compared with the supply voltage and a preset reference voltage by a voltage detection circuit 21. If the supply voltage is lower than the reference voltage, the power supply is supplied to the muting circuit 22. And a video signal stop signal is output, and the muting circuit 22 mutes the synchronization signal of the video signal output from the video processing circuit (not shown) to the monitor side. Therefore, the synchronization signal detecting circuit 23 on the monitor side
Are muted by the muting circuit 22 and no synchronization signal of the video signal is input. In the voltage step-up circuit 27, the count of the counter circuit 26 advances in synchronization with the oscillation frequency of the oscillation circuit 25, and the supply voltage of the power supplied from the battery is increased stepwise in accordance with the count output. While supplying it to the camera. Then, the supply voltage of the power supply and the reference voltage, which have been increased stepwise, are compared again with the voltage detection circuit 21. When the respective voltage values match and become an appropriate voltage, the voltage detection circuit 21 outputs the muting circuit. A release signal is output to 22. The muting circuit 22 receives the release signal and outputs a video signal output from the video processing circuit to the synchronization detection circuit 23. The synchronization detection circuit 22 outputs this video signal to the counter 26. The video signal is output to a video reproduction circuit, and the video from the camera is displayed on a monitor. The counter 26 stops counting based on the output from the synchronizing signal detecting circuit 23 to stop the voltage increase of the voltage step-up circuit 27. Hereinafter, the power supply is maintained with the stopped voltage value fixed. To the camera side. As described above, when a voltage drop due to cable routing is detected and raised to an appropriate voltage, a command signal for starting and stopping the rise is determined by whether or not a video signal is output to the monitor side. For the detection, for example, an inexpensive signal line that does not require a dedicated signal line 31 for feedback as shown in FIGS. 2 and 4 can be provided. The modulation circuit 7 and the demodulation circuit 1 shown in FIGS.
0, the signal superimposing circuits 8, 13 and the signal extracting circuit 14 are not required, and the circuit configuration can be simplified, inexpensive, and downsized. 4 and 5, the same reference numerals are given to the same circuit configurations as those in the above-described embodiment or the conventional example, and the description thereof will be omitted. In the above embodiment, an example in which the video signal is muted by the supplied voltage has been disclosed. However, in practice, only the synchronizing signal may be muted. Further, the synchronization signal may be slightly lowered so that the normal image is not affected but the synchronization detection circuit can detect it. The circuit for adjusting the voltage may increase or decrease the voltage in accordance with the detected synchronization signal, in addition to the step of increasing the voltage. As described above, the voltage drop guarantee circuit for a vehicle-mounted camera according to the present invention comprises: a camera mounted on a vehicle body; a power supply means for supplying power to the camera;
A voltage detection unit that compares a supply voltage supplied to the camera with a preset reference voltage and outputs the comparison result; and a video signal output from the camera based on a comparison result of the voltage detection unit. Muting means for muting at least a synchronizing signal; synchronizing signal detecting means for detecting a synchronizing signal of a video signal output from the camera; and a voltage supplied to the camera based on an output signal from the synchronizing signal detecting means. By providing the control means for adjusting, not only the need for a dedicated signal line can be eliminated, but also the circuit configuration can be simplified, and the cost and size can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit diagram showing a voltage drop guarantee circuit of a vehicle-mounted camera according to the present invention. FIG. 2 is a circuit diagram showing a conventional voltage drop guarantee circuit of a vehicle-mounted camera. FIG. 3 is a circuit diagram showing a voltage drop guarantee circuit of another conventional vehicle-mounted camera. FIG. 4 is a circuit diagram in a case where a muting circuit is provided in a voltage drop guarantee circuit of the conventional vehicle-mounted camera corresponding to FIG. 2; FIG. 5 is a circuit diagram in a case where a muting circuit is provided in the voltage drop guarantee circuit of the conventional vehicle-mounted camera corresponding to FIG. 3; [Description of Signs] 20 ... Voltage drop guarantee circuit 21 ... Voltage detecting means 22 ... Muting means 23 ... Synchronous signal detecting means 24 ... Control means

Claims (1)

(57) Claims 1. A camera mounted on a vehicle body, power supply means for supplying power to the camera, a supply voltage supplied to the camera, and a preset reference voltage. a comparison and a voltage detecting means for outputting a comparison result, and muting means for muting at least the synchronization signal of the video signal to be the camera or RaIzuru force based on the comparison result of the voltage detecting means, said camera A synchronizing signal detecting means for detecting a synchronizing signal of a video signal outputted from the camera, and a control means for adjusting a voltage to be supplied to the camera based on an output signal from the synchronizing signal detecting means. Voltage drop guarantee circuit for in-vehicle cameras.