JPH067635Y2 - TV camera power supply - Google Patents

Description

[Detailed Description of the Invention] (Industrial field of application) The present invention relates to a television camera that is an external synchronization type and outputs a video composite signal to a power line, regardless of the cable length between the camera and the power source. Regarding a device that provides a stable power supply.

(Prior Art) Conventionally, as shown in JP-A-47-3773, there is a TV camera and a power source which are separated from each other. According to this method, when the cable line connecting the TV camera and the power supply becomes long, the voltage loss in the cable line cannot be ignored (4.4Ω × current value loss at 100 m). In order to solve this problem, in the above publication, the voltage actually applied to the TV camera via the cable wire is compared with the reference voltage, and the difference voltage is frequency-converted and fed back to the power supply via the cable wire, The output voltage from the power supply is variably controlled according to this frequency signal.

(Problems to be solved by the invention) However, according to this method, the television camera itself must be a special one having a reference voltage source, a differential amplifier, and a Vf converter, and the television camera that has been conventionally used. Must be improved by adding the above configuration to.

In addition, in recent years, an external synchronization type camera that receives a synchronization signal from the outside has been proposed, and there is a method of superimposing a video signal on a power cable line in order to reduce the number of lines connecting the camera to a power source. Proposed and being implemented. In this case, the cable for connecting the camera to the power supply will be superposed with the external synchronizing signal, the composite signal of the video signal and the synchronizing signal, and the DC signal for the power source. Superimposing the signals was technically complicated.

(Means for Solving the Problem) The present invention provides a stable power supply voltage irrespective of the cable length in a television camera of this external synchronization type, in which the composite signal from the camera and the external synchronization signal are superimposed on the power supply line. It is to provide a power supply device for a television camera that can be supplied.

To this end, the present invention provides a sync separation circuit in which the power supply circuit extracts only a sync signal from a composite signal from the television camera, a sync signal from the sync separation circuit, and a sync signal from the sync signal generator. A phase comparison circuit for comparing and outputting a signal corresponding to the phase difference between the two signals, a voltage control circuit for outputting a voltage control signal corresponding to the signal from the phase comparison circuit, and the television corresponding to the voltage control signal And a variable voltage source for varying an output voltage value supplied to the camera via the superimposing circuit and a cable line.

(Function) The external synchronizing signal supplied to the television camera and the synchronizing signal in the composite signal output from the television camera have opposite polarities and the same phase. However, when the synchronizing signal output from the television camera is supplied to the power supply circuit through the cable line, a delay occurs due to the propagation characteristic of the cable (for example, 0.5 μS per 100 m). Therefore, a phase difference occurs with the actual external synchronization signal. The phase comparison circuit detects the phase difference by comparing the sync signal separated from the composite signal by the sync separation circuit with the external sync signal, and the voltage value supplied to the television camera is changed according to the phase difference. It is something that is done.

(Embodiment) The drawings are block diagrams showing an embodiment of the present invention. In the figure, a camera 2, a power supply circuit 4, and a sync signal generator 6 for generating an external sync signal are connected via a superposing circuit 5 by one cable line 8. Therefore TV camera 2
The composite signal of the external synchronizing signal, the video signal from the television camera 2 and the synchronizing signal is superimposed on the cable line 8 supplying power to the. The sync separation circuit 10 in the power supply circuit 4 separates only the sync signal from the composite signal. The phase comparison circuit 12 compares the separated sync signal with the external sync signal and generates an output signal corresponding to the phase difference. This output signal is the voltage control circuit 1
It is converted by 4 into the corresponding voltage control signal. The voltage supplied from the variable voltage source 16 to the television camera 2 is changed by this voltage control signal.

In this way, when the cable is long and the phase difference is large, the power supply voltage supplied to the television camera 2 is high, and when the cable is short and the phase difference is small, the supply voltage is low.

(Effect of the Invention) As described above, according to the present invention, a stable power supply voltage can be always supplied to a television camera of an external synchronization type and a method of superimposing a video composite signal on a power supply line regardless of the cable length. Further, the present invention can be applied to any camera of the above system without adding special improvement.

[Brief description of drawings]

 The drawing is a block diagram showing an embodiment of the present invention. 2 ... Camera, 4 ... Power supply circuit, 6 ... Sync signal generator, 8 ... Cable, 10 ... Sync separation circuit, 12 ... Phase comparison circuit, 14 ... Low-pass filter, 16 ... Variable voltage source .

Claims (1)

[Scope of utility model registration request] 1. A sync signal generator for generating an external sync signal, a television camera for receiving a sync signal from the sync signal generator and outputting a video signal and a composite signal of the sync signal to a power supply line, and the television. A power supply circuit for supplying power to the camera, a power supply circuit, a superimposing circuit for superimposing signals from the synchronization signal generator and the television camera, and a cable wire connecting the superimposing circuit and the television camera.
In a power supply device for a television camera having: a power source circuit, a sync separation circuit for extracting only a sync signal from a composite signal from the TV camera, a sync signal from the sync separation circuit, and a sync signal from the sync signal generator. A phase comparison circuit that outputs a signal corresponding to the phase difference between the two signals, a voltage control circuit that outputs a voltage control signal corresponding to the signal from this phase comparison circuit, and a voltage control signal corresponding to the voltage control signal A power supply device for a television camera, comprising: a variable voltage source for varying an output voltage value supplied to the television camera via the superposition circuit and a cable line.