JP2001255969A - Electronic equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate a countermeasure for two kinds of communication standards for a single connector, and to cause normal operation of electronic equipment, regardless of the relation between a power supply voltage and a signal voltage. SOLUTION: A polarity detecting means 1b detects the polarity of a power supply voltage supplied from signal lines 2b and 2c of a connection cable 2. A polarity-inverting means 1c inverts the polarity of the power supply voltage supplied from the connection cable 2, according to the polarity of the power supply voltage detected by the polarity detecting means 1b. A first communication control part 1g is based on the first communication standard. A second communication controlling part 1h is based on the second communication specification. A selecting means 1d selects one of the first and second communication control parts, and connects the selected communication control part to the signal line 2d and 2e of the connection cable 2. A control means 1e insulted electrically from the selecting means 1d, and the selecting means 1d is controlled, according to the detected result of the polarity of the polarity detecting means 1b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic apparatus, and more particularly, to receiving power from an external device via a connection cable and transmitting / receiving information to / from another device via a signal line included in the connection cable. Electronic devices that perform

[0002]

2. Description of the Related Art For example, peripheral devices for personal computers have generally been provided with a plurality of connectors conforming to different standards to enhance the connectivity with personal computers.

However, as the number of connectors increases, the area occupied by the connectors also increases, which causes a problem that it is difficult to reduce the size of the device. Therefore,
The inventor of the present invention, in the earlier application, equipped the electronic device with a communication control unit conforming to two different communication standards, and turned on and off the semiconductor switch according to the polarity of the power supplied from the connection cable. A method for selecting a communication control unit is proposed.

[0004]

By the way, in such a method, since the semiconductor switch is driven by the power supply voltage, there is a problem that it cannot cope with a case where the signal voltage exceeds the power supply voltage.

The present invention has been made in view of such a point, and an electronic apparatus which can cope with a plurality of communication standards and can operate even when a signal voltage exceeds a power supply voltage by one connector is provided. The purpose is to provide.

[0006]

According to the present invention, in order to solve the above-mentioned problems, power is supplied from the outside via a connection cable 2 shown in FIG. 1 and a signal line included in the connection cable 2 is provided. In the electronic device 1 for exchanging information with another device by 2d and 2e, the polarity detecting means 1b for detecting the polarity of the power supply voltage supplied from the connection cable 2 and the polarity detecting means 1b for detecting the polarity of the power supply voltage. A polarity inverting means 1c for inverting the polarity of the power supply voltage supplied from the connection cable 2 according to the polarity, a first communication control unit 1g conforming to the first communication standard, and a second communication standard. A compliant second communication control unit 1h and a selection unit 1d for selecting one of the first and second communication control units and connecting to the signal lines 2d and 2e of the connection cable 2
And a control unit 1e that is electrically insulated from the selection unit 1d and controls the selection unit 1d in accordance with the result of polarity detection by the polarity detection unit 1b. An electronic device is provided.

Here, the polarity detecting means 1b detects the polarity of the power supply voltage supplied from the connection cable 2. The polarity inversion means 1c inverts the polarity of the power supply voltage supplied from the connection cable 2 according to the polarity detected by the polarity detection means 1b. The first communication control unit 1g complies with the first communication standard. The second communication control unit 1h complies with the second communication standard. The selecting unit 1d selects one of the first and second communication control units, and selects the connection cable 2
To the signal lines 2d and 2e. Control means 1e
Is electrically insulated from the selection means 1d, and according to the polarity detection result by the polarity detection means 1b,
It controls the selecting means 1d.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a principle diagram illustrating the operation principle of the electronic device of the present invention. As shown in this figure, an electronic device 1 of the present invention includes a connector 1a, a polarity detection unit 1
b, polarity inversion means 1c, selection means 1d, control means 1e,
A printed wiring board 1f, a first communication control unit 1g, and
The second communication control unit 1h exchanges information with another electronic device via a connection cable 2 having a connector 2a, and receives power from the other electronic device.

The polarity detecting means 1b detects the polarity of a power supply voltage supplied from another electronic device via the signal lines 2b and 2c. The polarity inversion means 1c inverts the polarity of the power supply voltage supplied from another electronic device according to the polarity of the power supply detected by the polarity detection means 1b.

The selecting means 1d connects the signal lines 2d and 2e to either the first communication control section 1g or the second communication control section 1h under the control of the control means 1e. The control means 1e controls the selection means 1d according to the detection result of the power supply polarity by the polarity detection means 1b. The selection means 1
d and the control means 1e are electrically insulated.

The printed wiring board 1f is a board that controls the main functions of the electronic device 1, and is operated by a power supply supplied from the polarity reversing means 1c. The printed wiring board 1f needs to be supplied with a positive pole of the power supply voltage on the upper side of the drawing and a negative pole on the lower side.

The first communication control unit 1g conforms to the first communication standard, and performs control for exchanging information with another electronic device (not shown). The second communication control unit 1h conforms to a second communication standard different from that of the first communication control unit 1g, and performs control for exchanging information with another electronic device (not shown).

Next, the operation of the above principle diagram will be described. Now, it is assumed that the connector 2a of the connection cable 2 connected to another electronic device (not shown) is connected to the connector 1a. The other electronic devices are based on the first communication standard, and the signal line 2b of the connection cable 2 has the plus side of the power supply, the signal line 2c has the minus side of the power supply,
It is assumed that a communication signal conforming to the first communication standard is applied to the signal lines 2d and 2e.

In such a case, the polarity detecting means 1b
Determines that the power supply polarity is normal, and
Operation is put on hold. As a result, the power supply voltage input via the connector 1a is supplied to the printed wiring board 1f as it is, and the printed wiring board 1f can operate normally.

At this time, the control means 1e detects from the detection result of the polarity detection means 1b that the power supply voltage supplied from the connector 1a is normal, and that the first communication standard is selected. Recognize And control means 1
e controls the selection means 1d to connect the signal lines 2d and 2e to the first
Is connected to the communication control unit 1g. As a result, the first communication control unit 1g can normally communicate with another electronic device (not shown).

Next, an operation in the case of connection to an electronic device (not shown) conforming to the second communication standard will be described. Now, the connection cable 2 is connected to an electronic device conforming to the second standard, and the connector 2 a is connected to the connector 1.
Assume that it is connected to a. At this time, it is assumed that the polarities of the signal lines 2b and 2c of the connection cable 2 are reversed to indicate that the signal lines are the second communication standard.

In such a case, the polarity detecting means 1b
Detects that the power supply polarity is inverted, and controls the polarity inversion means 1c to invert the power supply voltage. As a result, the power supply voltage input via the connector 1a is supplied to the printed wiring board 1f in a state where the polarity is inverted, and the printed wiring board 1f can operate normally.

At this time, the control means 1e detects from the detection result of the polarity detection means 1b that the power supply voltage supplied from the connector 1a is inverted, and selects the second communication standard. Recognize that you are. Then, the control means 1e controls the selection means 1d to control the signal lines 2d and 2d.
e is connected to the second communication control unit 1h. As a result, the second
The communication control unit 1h allows normal communication with another device (not shown).

As described above, in the electronic apparatus of the present invention, the polarity of the power supply voltage is detected by the polarity detection means 1b, and when the polarity is reversed, the polarity of the power supply voltage is inverted by the polarity inversion means 1c. The control means 1e controls the selection means 1d in accordance with the polarity thereof to select either the first communication control section 1g or the second communication control section 1h. Communication with the electronic device can be performed by the same connector 1a.

The selection means 1d and the control means 1e are
As described above, the selection means 1d is insulated.
Can operate normally even when the signal voltage supplied to the power supply exceeds the power supply voltage.

Next, an example of an embodiment of the present invention will be described. FIG. 2 is a circuit diagram showing a configuration example of the embodiment of the present invention. In this figure, an electronic device 20 according to the present invention includes a connector 21, a power supply polarity unifying circuit 22, a main circuit 23, resistors 24a to 24d, and optical relays 25a to 25d.
25d.

The connector 21 is a 4-pin connector, and includes a + power supply line, a ground (GND) line, and signal lines A1 and A
2 and is fitted to a connector 50b provided at the end of the connection cable 50. Note that connector 2
1 and the connector 50b are in a male-female relationship.

The power supply polarity unifying circuit 22 includes an FET (Field
Effect Transistor) 22a and 22b, and diodes 22c and 22d.
3 is controlled so that only a voltage of a determined polarity is applied. Here, the FETs 22a and 22b are N-channel power MOSFETs (Metal Oxide Semiconductor FETs).
And diodes 22c and 22d
Are constituted by Schottky barrier diodes.

Since the FETs 22a and 22b and the diodes 22c and 22d are directly inserted into the power supply line, the FETs 22a and 22b must have an allowable current value that is equal to or larger than the maximum current value flowing into the main circuit 23.

The main circuit 23 is a part that controls the main functions of the electronic device 20. Driver 23a and driver 23
b conforms to different communication standards A and B, respectively.
In the case of a normal device, either one of them is provided. The main circuit 23 is supplied with power supplies VCC and GND, and also supplied with a CNTS signal which is referred to by a control unit inside the main circuit 23 when switching communication protocols.

The resistors 24a to 24d are protection resistors,
An excessive current is prevented from flowing into the light emitting section of the optical relay. Optical relays 25a to 25d are connected to pins 3 and 4 and driver 23 according to the power supply voltage applied to pins 1 and 2.
The connection with the a and 23b is interrupted appropriately.

The optical relays 25a to 25d are optical MOS-F
It is constituted by an ET relay, and changes its conduction state according to the polarity of the power supply voltage applied to pins 1 and 2. In this example, when the plus side and the minus side are supplied to pins 1 and 2 respectively, the semiconductor switch inside the optical relay becomes conductive, and the minus side and the plus side are supplied to pins 1 and 2 respectively. , The internal semiconductor switch is in an insulated state. Since the internal semiconductor switch is controlled by the light from the light emitting unit, the light emitting unit and the semiconductor switch are electrically insulated.

Next, the operation of the above embodiment will be described. First, as shown in FIG. 3A, an operation when the electronic device 40 conforming to the communication standard A and the electronic device 20 according to the present invention are connected by the connection cable 50 will be described.

The connector 50a of the connection cable 50 is a connector conforming to the communication standard A. Here, FIG.
As shown in (B), a 4-pin connector is used, 1 pin is a + power source, 2 pin is GND, 3 pin is a signal line A1, and 4 pin is a signal line A2.

The connector 50b has a connector and a male connector,
In a female relationship. The pin arrangement is exactly the same as that of the connector 50a. That is, as shown in FIG. 3B, the connection of the connection cable 50 for the communication standard A is such that the pins of the same number of the connector 50a and the connector 50b are connected.
The pin is a + power source, the pin 2 is GND, and the pins 3 and 4 are signal lines A1 and A2 of the A communication standard, respectively.

When the electronic device 40 and the electronic device 20 are connected by the connection cable 50 in this manner, in the electronic device 20, a positive power supply is connected to pin 1 and a GND is connected to pin 2. In this case, the diode 22c is in a forward bias state, while the diode 22d is in a reverse bias state. As a result, a current flows through the diode 22c, no current flows through the diode 22d, and a current flows into the VCC of the main circuit 23 through the diode 22c.

The gate terminal of the FET 22b has "H" (+
Power supply) is applied. Here, as shown in FIG.
When the voltage applied to the gates of the FETs 22a and 22b is "H", a current flows between the source and the drain,
When the voltage applied to the gate is “L”, the source
No current flows between the drains. Therefore, the FET 22b
A current flows through the source terminal and the drain terminal of the transistor. Conversely, the gate terminal of the FET 22a is "L" (GN
Since D) is applied, no current flows through the source terminal and the drain terminal of the FET 22a.

As a result, from the GND of the main circuit 23 to the FET
A current flows through the source terminal and the drain terminal of 22b, and finally flows out to the 2nd pin of the connector 21. In summary, the current flowing from the pin 1 flows into the VCC terminal of the main circuit 23 via the diode 22c, and the current flowing from the GND terminal flows to the pin 2 via the source and the drain of the FET 22b. Then, the power supply voltage is normally supplied to the main circuit 23.

At this time, the optical relays 25a, 25b
Is in a forward bias state, while the optical relay 25
c and 25d are in a reverse bias state. here,
As shown in FIG. 5A, when the light emitting portion of the optical relay is in a forward bias state, light is emitted from the light emitting portion and the MOS-FE
It is incident on the gate of T. As a result, the MOS-FET is turned on as shown in the equivalent circuit of FIG.
On the other hand, as shown in FIG. 6A, when the light emitting portion of the optical relay is in a reverse bias state, no light is emitted from the light emitting portion. As a result, as shown in the equivalent circuit of FIG. MOS-
The FET enters an insulating state. FIG. 7 summarizes the above.

Therefore, in the present example, the optical relays 25a,
25b becomes conductive, while the optical relays 25c, 25c
d is in an insulating state. As a result, the pins 3 and 4 are connected to the driver 23a, and communication can be performed based on the communication standard A.

Since the CNTS signal indicating the state of pin 1 is in the state of "H", the microprocessor included in the main circuit 23, for example, recognizes that the communication standard A is selected. However, it becomes possible to execute a protocol conforming to the communication standard A even at the software level.

By the above operation, a normal power supply voltage is supplied to the main circuit 23. Further, in the main circuit 23, the driver 23a is selected, and the microprocessor executes the program conforming to the communication standard A by the CNTS signal, so that information is normally transmitted and received between the electronic device 40 conforming to the communication standard A. It is possible to do.

Next, as shown in FIG. 8, the operation when the electronic device 60 conforming to the communication standard B and the electronic device 20 according to the present invention are connected by the connection cable 70 will be described. The connector 70a of the connection cable 70 has the communication standard B
It is a connector conforming to. Here, as shown in FIG. 8B, a 4-pin connector is used, 1 pin is a + power source,
Pin is GND, pin 3 is signal line B1, pin 4 is signal line B
Let it be 2.

The connector 70b is the same as the connector 21
In a female relationship. The pin arrangement is such that one pin is GND, two pins are + power supply, three pins are signal lines B1 and four pins are signal lines B2. That is, the connection cable 70 for the communication standard B
Is connected to one of the connectors 70a as shown in FIG.
The pins correspond to the two pins of the connector 70b,
Pins are connected to pin 1 of the connector 70b. In the connector 70b, pin 1 is GND, pin 2 is + power, pins 3 and 4 are signal lines B1 and B2 of the communication standard B.

As described above, when the electronic device 60 and the electronic device 20 are connected by the connection cable 70, as shown in FIG. Is connected. In this case, the diode 22c is in a reverse bias state, while the diode 22d is in a forward bias state. As a result, no current flows through the diode 22c, a current flows through the diode 22d, and a current flows into the VCC of the main circuit 23 through the diode 22d.

The gate terminal of the FET 22b is "L" (G
ND) is applied, and “H” (+ power supply) is applied to the gate terminal of the FET 22a. Therefore,
A current flows through the source terminal and the drain terminal of the FET 22a. Conversely, no current flows through the source terminal and the drain terminal of the FET 22b. As a result, the main circuit 23
, A current flows from the GND through the source and the drain of the FET 22a, and finally flows out to pin 1 of the connector 21. In summary, the current flowing from the pin 2 flows into the VCC terminal of the main circuit 23 via the diode 22d,
The current flowing out of the GND terminal flows out to pin 1 via the source and the drain of the FET 22a, so that the power supply voltage is normally supplied to the main circuit 23.

At this time, the optical relays 25a, 25b
Is in a reverse bias state, and the optical relays 25c and 25d are in a forward bias state. As a result, the optical relays 25a,
25b is insulated, and the optical relays 25c and 25d are in a conductive state.
b, and can communicate based on the communication standard B.

At this time, the microprocessor of the main circuit 23 recognizes that the communication standard B has been selected because the CNTS signal is in the "L" state, and the protocol conforming to the communication standard B also at the software level. Execute

By the above operation, a normal power supply voltage is supplied to the main circuit 23. Further, in the main circuit 23, the driver 23b is selected, and the microprocessor executes the program conforming to the communication standard B by the CNTS signal.
It is possible to reliably exchange information with the server.

As described above, although the electronic device 20 has only a minimum number of connector pins, it can automatically support the two communication standards A and B simply by changing the connection cable. Becomes possible.

Therefore, according to the present invention, it is possible to support a plurality of communication standards with a single electronic device by simply replacing the cable, thereby improving usability. For example, in a fingerprint verification device with a personal authentication function, which is a security device, the same device can be used in various situations, and the trouble of updating and backing up data can be reduced.

Further, since there are a plurality of communication standards that can be supported, the number of connectable devices increases accordingly, and as a result,
Connection limit is reduced. Further, it is possible to develop a product corresponding to two types of communication specifications while maintaining upward compatibility with existing equipment by adding a few circuits. Therefore, the development cost can be reduced and the development speed can be reduced.

Since the number of pins of the connector can be minimized, the size of the connector can be reduced. As a result, the size of the electronic device and the size of the cable can be reduced, and the cost can be reduced.

Further, as compared with the case where two connectors are used to support two types of communication standards, only one connector is required, so that the device size and cost can be reduced.

Further, using the optical relays 25a to 25d,
3 pins and 4 with driver 23a or driver 23b
Since the connection with the pin is changed, the driver 23a or the driver 23b can be reliably selected even when the signal voltage is higher than the power supply voltage.
For example, in the RS-232C standard, the signal voltage is ± 15 V
However, even if the power supply voltage of the device is 3.3 V, it is possible to comply with such a standard.

In the above-described embodiment, a circuit composed of a diode and an FET is used as the power supply polarity unifying circuit 22, but such a circuit is merely an example. It is also possible.

[0052]

As described above, according to the present invention, power is supplied from the outside via a connection cable, and information is exchanged with another device via a signal line included in the connection cable. In an electronic device, a polarity detection unit that detects the polarity of a power supply voltage supplied from a connection cable, and a polarity inversion unit that inverts the polarity of a power supply voltage supplied from the connection cable in accordance with the polarity detected by the polarity detection unit And selecting a first communication control unit conforming to the first communication standard, a second communication control unit conforming to the second communication standard, and one of the first and second communication control units. A selector connected to the signal line of the connection cable, and a controller that is electrically insulated from the selector and controls the selector in accordance with a polarity detection result by the polarity detector. Yes As a result, it is possible to support two types of communication standards with a single connection terminal, and it is possible to operate the electronic device normally regardless of the relationship between the power supply voltage and the signal voltage. Become.

[Brief description of the drawings]

FIG. 1 is a principle diagram for explaining the operation principle of the present invention.

FIG. 2 is a circuit diagram showing a configuration example of an embodiment of the present invention.

3A is a diagram illustrating a state in which the electronic device illustrated in FIG. 2 is connected to an electronic device that conforms to communication standard A, and FIG. 3B is a diagram illustrating a connection relationship of a connection cable; .

FIG. 4A is a diagram for explaining names of respective parts of the FET, and FIG. 4B is a diagram for explaining an outline of an operation thereof.

FIG. 5A is a diagram showing a state where the optical relay is in a forward bias state, and FIG. 5B is an equivalent circuit at that time.

FIG. 6A is a diagram showing a state where the optical relay is in a reverse bias state, and FIG. 6B is an equivalent circuit at that time.

FIG. 7 is a diagram illustrating a relationship between a bias state and a conduction / insulation state of the optical relay.

8A is a diagram showing a state in which the electronic device shown in FIG. 2 is connected to an electronic device conforming to the communication standard B, and FIG. 8B is a diagram showing a connection relationship of connection cables. .

9 is a diagram illustrating a state of each unit of the embodiment in the connection relationship illustrated in FIG. 8;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Electronic equipment, 1a ... Connector, 1b ... Polarity detection means, 1c ... Polarity inversion means, 1d ... Selection means, 1e
... Control means, 1f ... Printed wiring board, 1g ... First
1h ... second communication control unit, 2 ... connection cable, 2a ... connector, 20 ... electronic device, 21
…… Connector, 22 …… Power supply polarity unified circuit, 22a, 2
2b ... FET, 22c, 22d ... Diode, 23
... Main circuit, 23a, 23b ... Drivers, 24a-2
4d: resistance, 25a to 25d: optical relay, 40, 6
0 ... electronic equipment, 50, 70 ... connection cable, 50
a, 50b, 70a, 70b ... connector

Claims (3)

[Claims] 1. An electronic device which is externally supplied with power via a connection cable and transmits and receives information to and from another device via a signal line included in the connection cable. Polarity detecting means for detecting the polarity of the power supply voltage to be supplied; polarity inverting means for inverting the polarity of the power supply voltage supplied from the connection cable in accordance with the polarity detected by the polarity detecting means; A first communication controller conforming to a standard, a second communication controller conforming to a second communication standard, and selecting one of the first and second communication controllers, A selection unit connected to the signal line, and the selection unit is electrically insulated, and a control unit that controls the selection unit in accordance with a result of polarity detection by the polarity detection unit; An electronic device comprising: 2. The electronic apparatus according to claim 1, wherein said selection means and said control means are constituted by optical relays. 3. The electronic apparatus according to claim 1, further comprising a communication protocol selection unit that selects a communication protocol in accordance with a result of the polarity detection by the polarity detection unit.