JP3015617B2 - Information processing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information processing apparatus such as a personal computer, and more particularly to an information processing apparatus capable of preventing inconvenience caused by connection with external peripheral devices.

[0002]

2. Description of the Related Art In general, peripheral devices such as a printer and a communication modem device are often externally connected to an information processing apparatus such as a personal computer. These peripheral devices are separate from the information processing device and have their own power supply, and are connected to the information processing device by a dedicated signal line. When the power supply of the peripheral device is on when the power supply is off, a leak current flows from the peripheral device to the information processing device via the signal line, thereby causing various failures. Hereinafter, the situation will be briefly described.

FIG. 4 shows a conventional information processing apparatus (here, a notebook personal computer) and peripheral devices. As shown in the figure, the peripheral device 60 is connected to the input / output connector 11 of the notebook computer 50 by a signal line 16 and further connected to the input / output (I / O) device 14. The I / O device 14 performs a signal transmission / reception operation with the peripheral device 60 using a DC voltage V _CC supplied from a power supply device (not shown) via the power supply line 13 as an operation power supply. The notebook computer 50 includes a reset IC 19 for performing a system reset. The reset IC 19 connects the resistor 1 to the power supply line 13 when the power is turned on (when the system is started).
8, the charge voltage 2 of the capacitor 17 connected via
0 (the solid line 61 in FIG. 6A) exceeds a predetermined threshold voltage V _TH (FIG. 6), the reset signal 21
(FIG. 2B) is output.

Now, the power supply line 13 of the notebook personal computer 50
Is off, and the power of the peripheral device 60 is on, a leak current flows from the peripheral device 60 to the I / O device 14 via the signal line 16. The I / O device 14 generally has a CMOS structure including a p-type FET (field effect transistor) 55 and an n-type FET 56 as shown in FIG.
A transistor is used as a component, and a signal 58 to a peripheral device is output by a drive signal 57 from the notebook computer. For this reason, when the power supply of the notebook personal computer 50 is off and the peripheral device 60 is on, a leakage current flows into the CMOS transistor. May be destroyed. Such a phenomenon similarly occurs in the input stage.

Therefore, conventionally, as shown in FIG. 4, resistors 51, 52 and the like are inserted into a signal line, and this signal line is connected to a power supply line 13 via diodes 53, 54 and the like. The leak current is allowed to escape to the power supply line 13 at the ground level.

[0006]

However, in such a case, the leakage current flows into the capacitor 17 via the power supply line 13 and the resistor 18 and charges the capacitor 17. Therefore, in the power-off state, the charge voltage 20 (broken line 59 in FIG. 6A) already exceeds the threshold voltage V _TH , and a normal system reset is not performed when the power supply of the notebook computer is turned on. It will be.

As described above, in the conventional information processing apparatus, when the power supply of the device in the information processing apparatus is turned off, the leakage current flowing from the externally connected peripheral device side causes the information processing apparatus side to perform the above-described operation. There is a problem that such troubles occur.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an information processing apparatus capable of preventing device destruction due to a leak current and ensuring a normal reset operation at the time of startup. It is in.

[0009]

According to a first aspect of the present invention, there is provided an information processing apparatus having an input / output device for transmitting / receiving a signal to / from an externally connected peripheral device via a signal line. In (i) in the state where the power of the input / output device is off, a conversion means for converting a leak current flowing through the signal line from the peripheral device side in a power-on state into a voltage, and (ii) A switch that is inserted into the signal line and disconnects the signal line using an output voltage of the conversion unit as an operation power supply when a power supply of the input / output device is off.

According to a second aspect of the present invention, in the information processing apparatus according to the first aspect, when the power supply of the input / output device is off, the output voltage of the conversion means is selected. A selector for selecting a supply voltage to the input / output device when the power is on,
The switch disconnects the signal line when the power of the input / output device is off, and uses the signal line when the power of the input / output device is on, using a voltage selected by the selector as an operation power supply. Connection is performed.

An information processing apparatus according to a third aspect of the present invention is characterized in that an input / output device for transmitting / receiving a signal to / from an externally connected peripheral device via a signal line and a power supply of the apparatus main body are turned on. And a reset circuit that outputs a system reset signal according to the charge voltage of the capacitor. (I) The peripheral device in a power-on state when the power of the input / output device is off. Conversion means for converting a leak current flowing through the signal line from the signal line into a voltage, and (ii) when the power supply of the apparatus main body is off, the output voltage of the conversion means is used as an operating power supply to charge the capacitor. And discharge means for discharging.

[0012]

In the information processing apparatus according to the first aspect of the present invention,
In a state where the power of the input / output device is off, a leak current flowing through the signal line from the peripheral device whose power is on is converted into a voltage, and the switch operates using the leak current as an operating power. Thus, when the power supply of the input / output device is off, the signal line is disconnected, and the inflow of leak current is prevented.

[0013] In the information processing apparatus according to the second aspect of the present invention, in addition to the operation of the first aspect, when the power of the input / output device is on, the switch operates using this power as an operating power, and the signal line is operated. Is connected.

In the information processing apparatus according to the third aspect of the present invention, when the power supply of the input / output device is off, the leak current flowing through the signal line from the peripheral device side in the power-on state becomes a voltage. It is converted, and the discharging means operates using this as an operating power supply. Thereby, the charge of the capacitor is discharged.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings.

FIG. 1 shows a notebook personal computer and peripheral equipment according to an embodiment of the present invention. In this figure,
The same parts as those in the conventional example (FIG. 4) are denoted by the same reference numerals, and description thereof will not be repeated.

The features of this embodiment are as follows.
An analog switch 15 is provided between the input / output connector 11 and the I / O device 14. When the power supply line 13 is off and the power of the peripheral device 60 is on, the analog switch 16 is turned off (disconnected). Another object of the present invention is to block the flow of leakage current from the peripheral device.

The second feature of this embodiment is that when the power supply line 13 is off, the capacitor 1
7 for discharging the charge of 7
Has been established.

First, the first feature will be described.

As shown in the figure, a current / voltage converter 24 is connected to a signal line (here, an input signal line) between the input / output connector 11 and the analog switch 15 via diodes 22 and 23, thereby causing a leak. Current 2-3V
To a voltage V _L of about This voltage is
The power is supplied as an operating power to the analog switch 15 via the switch 7. The power supply line 13 has a voltage / signal converter 2
8 is connected, and outputs a gate signal of "L" level when the power supply line 13 is off, and outputs an "H" level when it is on. The analog switch 15 is “H”
The active operation is performed. After all, the power supply line 13 is closed when the power supply line 13 is off, and is opened when the power supply line 13 is on. Accordingly, I
It is possible to prevent leakage current from flowing into the / O device 14.

When the power supply line 13 is turned on, the analog switch 15 operates using a voltage supplied from the power supply line 13 via a forward diode 29 as a power supply.

Next, the second feature will be described.

The output side of the current / voltage converter 24 is connected to a voltage / signal converter 25 having the same configuration as the above-mentioned voltage / signal converter 28, whereby the output voltage of the current / voltage converter 24 is changed to a signal. The signal is converted into a level and input to the input terminal of the AND gate 31. The other inverting input terminal of the AND gate 31 is connected to the output side of a voltage / signal converter 33 having the same configuration as the voltage / signal converter 28 described above. The voltage / signal converter 33 converts the supply voltage V _CC from the power supply line 13 into a signal level and supplies the signal level to the AND gate 31. The operating power supply voltage of the AND gate 31 is the power supply V _L to the analog switch 15.
Is supplied.

The voltage / signal converter 33 is connected to the power line 13
Outputs an "L" level signal in an off state, and outputs an "H" level signal in an on state. In addition, since the current / voltage converter 24 outputs a voltage of 2 to 3 V as described above when the power of the peripheral device 60 is on, the voltage / signal converter 25 converts the voltage to an “H” level signal. Convert and output. Therefore, when the power supply line 13 is off, the output of the AND gate 31 becomes "H" level and is supplied to the base of the transistor 32, and the transistor 32 is turned on, so that the charge of the capacitor 17 is discharged. .

On the other hand, when the power supply line 13 is turned on, the output of the voltage / signal converter 33 becomes "H" level, and the output of the AND gate 31 also becomes "L" level.
The transistor 32 is turned off, the capacitor 17 is charged, and the charge voltage 20 becomes the threshold voltage V
_The reset signal 19 is output from the reset IC 19 when the threshold value _TH is exceeded.

The current / voltage converter 24 has, as shown in FIG. 2, for example, a transistor 41 having an input connected to the emitter, an output connected to the collector, and a base connected to the ground via a Zener diode 42; The circuit comprises a capacitor 43 connected between the ground and a capacitor 44 connected between the output and the ground.

In the voltage / signal converters 25, 28 and 33, for example, as shown in FIG. 3, a base and an emitter are connected to inputs via resistors 46 and 47, respectively, a collector is grounded, and an emitter is connected. Is connected to the output. As shown in this figure, when the input changes from 0 V to V _CC , the output changes from “L” to “H”.

In this embodiment, the analog switch 1
Although the operating power supply No. 5 is made from the leak current of the two input signal lines, a leak current of more input signal lines may be used, and a leak current flowing from the output signal line instead of the input signal line may be used. Of course, the leakage current of both input and output signal lines may be used.

[0029]

As described above, according to the first aspect of the present invention, when the power supply of the input / output device is off, the leak current flowing from the peripheral device side in the power-on state via the signal line is used. Since the current is converted into a voltage and the switch is operated using the voltage as an operation power supply, the signal line is cut off when the power supply of the output device is off, and the inflow of leak current is prevented. Therefore, there is an effect that destruction of the input / output device can be effectively prevented.

According to the second aspect of the present invention, when the power of the input / output device is on, the switch is operated using this power as the operating power. Lines are connected and normal operation is ensured.

In the information processing apparatus according to the third aspect of the present invention, when the power supply of the input / output device is off, the leakage current flowing through the signal line from the peripheral device side in the power-on state is converted into a voltage. After the conversion, the discharging means is operated using the power as an operating power source. Therefore, when the power source on the input / output device side is off, the charge of the capacitor is discharged, and the normal reset operation at the time of starting the system is secured. This has the effect.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a notebook personal computer and a peripheral device to which a device protection circuit and a reset malfunction prevention circuit according to an embodiment of the present invention are applied.

FIG. 2 is a circuit diagram showing a current / voltage converter in FIG.

FIG. 3 is a circuit diagram showing a voltage / signal converter in FIG. 1;

FIG. 4 is a block diagram showing a conventional notebook computer and peripheral devices.

FIG. 5 is an explanatory diagram showing a main part in the I / O device in FIG. 4;

FIG. 6 is a timing chart for explaining a reset operation of the notebook computer of FIG. 4;

[Explanation of symbols]

 Reference Signs List 10 notebook computer 13 power supply line 14 I / O device 15 analog switch 16 input / output signal 17 capacitor 18 resistor 19 reset IC 22, 23, 27, 29 diode 24 current / voltage converter 25, 28, 33 voltage / signal converter 31 AND gate 32 Transistor 60 Peripheral device

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G06F 3/00 G06F 1/24

Claims (3)

(57) [Claims] 1. An information processing apparatus having an input / output device for transmitting / receiving a signal to / from an externally connected peripheral device via a signal line, wherein a power-on state is provided when the input / output device is turned off. A conversion means for converting a leak current flowing from the peripheral device side through the signal line into a voltage, and a conversion means inserted into the signal line, wherein the power supply of the input / output device is turned off. An information processing apparatus, comprising: a switch that disconnects the signal line using an output voltage as an operation power supply. 2. The input / output device according to claim 1, further comprising: when the power of said input / output device is off, an output voltage of said conversion means is selected. A selector for selecting a supply voltage of the input / output device, wherein the switch uses the voltage selected by the selector as an operation power source, disconnects the signal line when the power of the input / output device is off, and An information processing apparatus, wherein the signal line is connected when the power of the entry output device is on. 3. An input / output device for transmitting / receiving a signal to / from an externally connected peripheral device via a signal line, a capacitor charged by turning on a power supply of the apparatus main body, and a charge voltage of the capacitor. A reset circuit that outputs a system reset signal, wherein a leak current flowing through the signal line from the peripheral device side in a power-on state when the power of the input / output device is off. And a discharging unit for discharging the charge of the capacitor using the output voltage of the converting unit as an operating power supply when the power supply of the apparatus main body is off. apparatus.