JPS61296383A - Electronic appliance - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] Field of Industrial Application The present invention relates to an electronic device that can drive both a cathode ray tube (hereinafter referred to as CRT) and a liquid crystal display (hereinafter referred to as LCD). TECHNOLOGY In conventional personal combinations, for example, as shown in Japanese Unexamined Patent Publication No. 59-91524, L is displayed on the display.
A portable device that uses a CD and is battery-powered has been developed, making it very convenient for outdoor use. However, LCDs are smaller than CRTs and have a lower display capacity. , when using CRT'i when used indoors.

Due to the difference in display configuration between LCD and CRT, an expansion device must be connected to drive the CRT, making the device larger. However, with the recent development of LCDs that have one-to-one correspondence with CRTs and the development of drive ICs that can drive both CRTs and LCDs, it has become possible to drive CRTs without connecting an expansion device. Case CRT and LCD
It is meaningless to drive both at the same time, and it is not preferable in terms of power consumption in portable and battery-powered devices.

(c) Problems to be Solved by the Invention The present invention has been made in view of the above problems, and provides an electronic device configured to prohibit driving of the built-in LCD when it is detected that a CRT is connected. It is something to do.

B.) Means for Solving the Problems The present invention provides means for detecting that a CRT is connected;
The present invention is constructed by means for stopping the LCD drive 'ff:M upon detection of the connection of the RT and for cutting off the electricity A'r to the LCD.

(e) Operation Since the present invention is configured as described above, when the CRT is connected, driving of the built-in LCD is prohibited.

(f) Example An embodiment of the present invention will be described below with reference to the drawings.

Figure 1 shows a personal computer osg for the 1llc collection. . (31 is a memory for storing data inputted from the keyboard (4) or data processed by the control circuit (1), and the writing and reading of data is controlled by the control circuit [1]. (5) is LCD and CF
This is a drive circuit that can drive both tT and video memory (6
Exchange of display data with 1?1 display data for all lines? LCD output buffer circuit (7) and CRT output buffer circuit (8)
Output to 1. Video memo January 6) LCD and CRT
It has a memory capacity that corresponds one-to-one with the display dots in the video memory (61), and is configured so that the display can be changed by rewriting the data in the video memory (61).The LCD output buffer circuit (
7) and the CRT output buffer circuit (8) are driven and controlled by enable signals (LCDEN, CRTEN J) generated from the input/output interface circuit (9; QIJ is the LCD output buffer circuit (8). 7)
If more output data is provided on the LCD, for example 600
It consists of a display with an X200 dot configuration. (ID
is the connector to which CRTCI3 shown in Figure 3 is connected,
R, G, B signals, etc. from the CRT output buffer circuit (8) are supplied. (13 is CRT output buffer circuit 1
It is connected to the output of 81 and the ratio detection circuit connects C to the connector υ.
It detects whether RTL5 is connected or not, and supplies the detection output to the input/output interface circuit (91.(14)
Reference numeral 1 denotes a power control circuit which controls the supply of power to the LCD IJ based on the CRT I/C. The control circuit (1) is connected to various parts by a signal bus a51 such as an address bus, a data bus, and a control bus, and sends and receives signals. The R signal of the R, G, B signal output of the circuit (8) is shown,
(161 is a voltage detector whose input is supplied with a divided voltage by resistor t171 (IFD), and the threshold and hold voltage are set to 1.2V. Connector (1) 1 is connected to CR
When 121 is not connected, the resistance σ7)(181(1
9 is a voltage detector (the input voltage of 161 is approximately 0.6 V
Since it is lower than the threshold voltage of 1.2V, the l-I''HH level signal is output from the voltage detector tlGI. Note that j is the voltage detector (161) that forcibly sets the output to a low level. It's a switch.

Figure 3 is a diagram showing the configuration of a typical input circuit of CRT σ2, in which a resistor (2p (2214)) has a voltage of about 2.9V applied to point A of the R signal input. Although the case is shown, a G or B signal may also be used.

Figure 4 is a diagram showing the configuration of the t-driver control circuit (1, 1+, -
12V' voltage is applied through the transistor L CD f
low level CRT configured to be supplied to lfl;
It is controlled via the inverter zl so that the control transistor (24J) becomes non-conductive by supplying the enable signal (CRT'ENJ), and the control transistor !241 controls the power supply to the LCDQtl. has been done.

Next, the operation of the present invention having such a configuration will be explained.

First, when the power switch (not shown) is turned on, the control circuit (
1) Initial clear processing is performed according to the program in the program memory (22). At this time, the control circuit checks the signal of the input/output interface circuit (9) and detects the signal from the detection circuit (131).

Assuming that CRTσ2 is not connected now, the voltage detector (161) of the detection circuit 03 shown in Fig. 82 is at a high level, and the control circuit fll determines that the CFt T 024 is not connected, and the LCDH' A low level LCD enable signal (LCDEN) for driving is supplied to the LCD output buffer circuit (71) via the input/output 1/7/8 circuit (9). At this time, the CRT enable signal (CRTEN) is at high level. , the CRT output buffer circuit (8) is rendered inoperable and the CFtT enable signal (CRT
The power supply control circuit (14) shown in FIG.
1 is a control transistor (2
By conducting the transistor with 4J conduction,
A driving voltage of -12V is supplied to LCDQI. In this way, the data input from the keyboard (41) and the data processed by the control circuit fi+ are transferred to the drive circuit (51
and Video Memo January 6) are supplied as display data to the LCD QO via the LCD output 6977 circuit (7), thereby displaying on I, CDCl [li].

Next, the operation when a CRT is connected will be explained.

When the power switch is turned on after connecting the CRT1 and the 21'jt connector συ, the control circuit ill checks the signal of the input/output interface circuit +91 in the initial clear process as described above, and detects the signal of the detection circuit (131). In this case, as shown in FIG. 3, the voltage at point A of CR12 is supplied to the voltage detector aO of the detection circuit ff3, and the resistance (171) of the detection circuit U (171 is the resistance of CRTCIZ) is supplied to the voltage detector aO of the detection circuit ff3.
21), so about 1.5V outside the potential at point A is supplied to the input of voltage detector 1) 61, and the threshold voltage is 1.2V or more, so 1! The output of the pressure detector (IQ) is set to low level. Upon detection of the low level signal, it is determined that the suppression circuit peak CRT (13) is connected, and contrary to the above, the CFtT enable signal (Cf't
TEN) is set to low level, and the LCD enable signal (LCDEN) is set to high level.

As a result, the CRT output buffer circuit (8) is set to an active state, and the LCD output 6977 circuit (7) is set to an inactive state. In this way, the display data outputted from the second drive circuit 15) is sent to the CR via the CRT output cover 7 front circuit (81).
The signal is supplied to the TC 125 and displayed.

At this time, the output of the LCD output buffer circuit (71) is in a high impedance state, but if noise occurs in the signal line, a meaningless display due to the noise may be displayed on the LCD rl(fi). Therefore, in this application, CF
? When the T enable signal (CRTENJ becomes low level and is supplied to the YL source control circuit), the control transistor 12.it becomes conductive, the transistor is also made non-conductive, and the drive voltage (-12V) to LCDN1tJ is set.
This prevents unnecessary display from occurring due to noise.

As shown in FIG. 5, the input circuit of the CRTC 121 is not pulled up to the power supply by the resistor T2IJ (2z).

If a voltage of approximately 2.9v is not generated at point A,
Even if CRTat is connected to the connector, the detection circuit (1
Since the output of 3I does not go to low level, such a CR
In the case of T(121), when the switch (201) is closed, it is forcibly set to a low level to instruct the connection of the CRT(12).

Furthermore, in the embodiment, the connection of the CRTat is automatically detected based on the voltage change of the signal line of the CRT output buffer circuit tR+, but in other embodiments, the connector 1)
] It is also possible to provide mechanical detection by providing a switch that is closed when the connector of the CRTi 121 is connected to the J section.

Furthermore, although a personal computer is shown in the embodiment, the present invention can also be applied to other electronic devices such as a word processor.

(G) Effects of the Invention As described above, the electronic device of the present invention has a common video memory and a drive circuit, is configured to be able to drive both an LCD and a CRT, and is provided with means for detecting that the CRT is connected. , when it is detected that a CRT is connected, the built-in L
Prohibits driving of CDs.

This reduces power consumption and prevents unnecessary displays from being displayed on the LCD due to noise, etc.

This will be useful for battery-powered electronic devices with built-in large LCDs.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of the electronic device of the present invention, @
2 is a circuit diagram showing the configuration of the detection circuit shown in FIG. 1, FIG. 6 is a circuit diagram showing the main parts of a CRT, and FIG. 4 is a circuit diagram showing the configuration of the power supply control circuit shown in FIG. 1. (1)...Control circuit, (2)...Program memory, 131...Memory 2 (41...Keyboard, (5
1... Drive circuit, (61... Video memory, (71
...LCD output 3777 circuit, (81...CRT output buffer circuit, (9)...I/O interface-7 eighth circuit, IIUI-L CD, [Ia・CRT, (1
31-...Detection circuit, (14+...[Fishing control circuit. Applicant Sanyo Electric Co., Ltd. and one other representative Patent attorney Shizuka Sano Figure 1

Claims (1)

[Claims] (1) In an electronic device configured to selectively drive both a built-in LCD and an externally connected CRT using a common drive circuit and video memory, means for detecting that a CRT is connected; By detection by said means, L
An electronic device characterized by comprising means for prohibiting driving of a CD.