JPH066731A - Video signal output device - Google Patents

Abstract

PURPOSE:To reduce current consumption and to extend a device operation time by disconnecting a power supply for a circuit to be driven only for the connection of a television to convert a digital signal into a video signal When the TV is not connected by a device driven by a battery and connected to the TV to display an image on the TV. CONSTITUTION:This video signal output device is provided with a pin connection detecting means 15 for detecting whether a pin is connected to a jack for outputting a video signal or not, a signal conversion circuit 16 for converting a digital signal into a video signal and a power supply control means 14 for controlling the ON/OFF of power supply to be supplied to the circuit 16.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a jack for outputting a video signal, which is driven by a battery, has a liquid crystal display means in the main body of the apparatus, and displays an image similar to the image displayed on the liquid crystal on a television. The present invention relates to a video signal output device for outputting to.

[0002]

2. Description of the Related Art FIG. 3 shows a block configuration of a conventional video signal output device. In FIG. 3, 31 is a battery for supplying power to the apparatus, 32 is a liquid crystal for displaying an image, 33 is a video RAM for storing image data to be displayed on the liquid crystal 32 and the television 37, and 34 is a video. RA
A timing control circuit that reads out the data of M33 and generates a timing signal required by the liquid crystal 32 and the signal conversion circuit 35, and 35 converts a video signal for connecting the digital signal provided from the timing control circuit 34 to an external television. Is a signal conversion circuit, 36 is a video jack for taking out a video signal to the outside, and 37 is a television for displaying the same image as the liquid crystal. A frame surrounding 31, 32, 33, 34, 35, and 36 indicates a range of video signal output, and a frame surrounding 32 to 36 indicates that the battery 31 supplies power and operates.

[0003]

However, in the above-mentioned conventional apparatus, the power is supplied to the signal conversion circuit 35 that operates only for connecting the television 37 even when the television 37 is not connected, and therefore the battery is correspondingly large. There was a problem that the current of was consumed. The present invention is intended to solve such a problem, and an object thereof is to provide a video signal output device in which power is not supplied to a signal conversion circuit when a television is not connected.

[0004]

In order to achieve the above object, the present invention controls a pin connection detecting means for detecting whether a pin is inserted in a video jack and a power supply supplied to a signal conversion circuit. Power supply control means is provided, and the power supply control means supplies power to the signal conversion circuit when the output of the pin connection detection means indicates that a pin is inserted in the video jack.

[0005]

Therefore, according to the present invention, when the video signal output device is not connected to the TV (when the pin for connecting the TV to the video jack is not inserted), power is not supplied to the signal conversion circuit and power saving is achieved. Can be achieved.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the configuration of a video signal output device in an embodiment of the present invention. In FIG. 1, 10 is a battery, 11 is a liquid crystal, 12 is a video RAM, 13 is a timing control circuit, 14 is a power supply control means, 15 is a pin connection detection means, 16 is a signal conversion circuit, 17 is a video jack, and 18 is a television. The parts other than the power supply control means 14 and the pin connection detection means 15 are the same as the blocks 31 to 37 of the conventional example (FIG. 3). 2 shows a concrete example of the power supply control means and the pin connection means in the embodiment of the present invention.

Below, the power supply control means 14 and the pin connection detection means
I will explain about the details of 15. In FIG. 2, reference numeral 21 is a video jack, and pin 1 is connected to the video signal 20 which is the output of the signal conversion device 30. The 2nd and 3rd pins are connected to the ground, and the 4th pin is connected to + 5V through the pull-up resistor 22 and input to the power supply control circuit 24 as a pin insertion detection signal 23. Pins 1 and 3 of the video jack 21 are used as a video signal for connecting the video signal output device to the television, and pins 2 and 4 are the video jack 21.
Used to detect pin insertion into.

Reference numeral 24 is a power supply control circuit for controlling the power supply to the signal conversion circuit 30, reference numeral 25 is an NPN transistor for inverting the pin insertion detection signal 23, the emitter is ground and the base is pin insertion detection signal. 23, the collector is pulled up through pull-up resistor 27 and pull-up resistor 28 to P
It is connected to the base of the NP transistor 26. Reference numeral 26 denotes a PNP transistor for controlling the power supply supplied to the signal conversion circuit 30, the emitter of which is connected to +5 V and the collector of which is connected to the power supply of the signal conversion circuit 30. When the video pin is not inserted into the video jack 21, the pin 4 and the pin 2 of the video jack 21 are in the connected state, so that the pin insertion detection signal 23 is connected to the ground. In this state, the base of the NPN transistor 25 is connected to the ground and the NPN transistor 25 is turned off.
Therefore, the base of the PNP transistor 26 is a pull-up resistor.
It is pulled up to + 5V via 28 and 27,
The PNP transistor 26 is also turned off, and no power is supplied to the signal conversion circuit 30. When the video pin is inserted into the video jack 21, the pin 4 and the pin 2 of the video jack 21 are unconnected. In this state, a current is supplied from +5 V to the base of the NPN transistor 25 via the pull-up resistor 22, and the NPN transistor 25 turns on. That is, the base of the PNP transistor 26 also has a pull-up resistor 28.
A current flows through the PNP transistor 26, and the signal conversion circuit 30 is supplied with power.

[0009]

As is apparent from the above-described embodiment, the present invention is effective when the television is not connected to the video signal output device.
Since the current to the signal conversion circuit can be reduced, the operation time of the battery can be extended.

[Brief description of drawings]

FIG. 1 is a block diagram of a video signal output device according to an embodiment of the present invention.

FIG. 2 is a circuit diagram of a power supply control means and a pin connection detection means of a video signal output device according to an embodiment of the present invention.

FIG. 3 is a block diagram of a conventional video signal output device.

[Explanation of symbols]

10, 31 ... Battery, 11, 32 ... Liquid crystal, 12, 33 ... Video RAM, 13, 34 ... Timing control circuit, 14 ... Power supply control means, 15 ... Pin connection detection means, 16, 30, 35 ... Signal conversion circuit, 17, 21, 36 ... Video Jack, 18, 37
... TV, 20 ... Video signal, 22, 27, 28 ... Pull-up resistance, 23 ... Pin connection detection signal, 24 ... Power control circuit, 25 ... NPN transistor, 26 ... PNP transistor, 29 ... Power supply line.

Claims (1)

[Claims] 1. Pin connection detection means for detecting whether or not a pin is connected to a jack for outputting a video signal,
A signal conversion circuit for converting a digital signal into a video signal,
A power supply control means for controlling on / off of a power supply supplied to the signal conversion circuit, and turning on the power supply control means when an output of the pin connection detection means indicates that a pin is connected. Characteristic video signal output device.