JP2007257128A - Information terminal and cradle apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a connection method which does not malfunction when contact of metallic objects occurs even if there is an exposed electrode. <P>SOLUTION: An information terminal 2 has an identification resistance 53, and a cradle 1 determines whether a value of the identification resistance 53 is within upper and lower limits using comparators 11 and 12. Only if it is recognized that it is within the range, electric power is supplied from a connector 4 of the cradle. Thereby, even if a metallic piece contacts with a terminal, the resistance value is determined to be outside of the range and an electric current does not flow. If there is no information terminal, an electric current does not flow. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method of combining an information terminal and a cradle that can be attached to and detached from the information terminal. Cradles can be easily connected to other devices simply by placing an information terminal, and are used to connect a personal computer with a cable to transfer data or charge an information terminal.

  A conventional information terminal and cradle power supply system will be described below.

  Conventionally, a load device connection detection circuit of the type shown in FIG. 2 has been generally used. In FIG. 2, 1 is a cradle, 2 is an information terminal such as a personal computer or PDA, and the connector 3 is further connected to a power supply device, generally an AC adapter.

  Both devices 1 and 2 are provided with at least one connection detection terminal 5 in addition to a terminal related to power supply at a connector connecting the two, and the cradle 1 has its terminal connected to the ground potential. Is detected and power is supplied to the information terminal. That is, when the detection terminal 5 becomes the ground potential, the FET (field effect transistor) 14 is turned on, and power is supplied through the connector 4.

In a simpler case, the cradle 1 does not have a switch function and always supplies power to the information terminal 2 side.
Japanese Patent Application Laid-Open No. 2002-7302 JP 2000-286961 A

  However, in the above conventional configuration, when the information terminal side is provided with a drop resistance, an impact resistance, a waterproof performance, and at the same time, it is desired to easily attach and detach both, the respective connectors are as follows. It is necessary to take.

  The contact on the information terminal side is exposed for ease of attachment / detachment, it is not covered with a cover, etc., is a flat contact with no moving parts that can easily achieve waterproofing, and the contact part is slightly inside the housing. It is required that no impact or external force is applied directly to the terminal part due to dropping or the like by sinking.

  On the other hand, since the cradle side corresponds to the same connector conditions as the information terminal, the contact point is exposed to make the connector easy to attach and detach, the contact part has elasticity such as bending, and the information terminal side sinks the connector. It needs to protrude somewhat from the housing to facilitate connection.

  With such a configuration, when power is supplied to the information terminal side from the cradle side whose main application is stationary, all the power supply terminals or connection detection terminals are exposed. For example, if a metal object accidentally contacts the detection terminal and the power supply terminal, the power supply terminal may be unintentionally energized, which may cause a failure.

  The present invention solves the above-described conventional problems, and an object thereof is to provide a connection method that does not malfunction due to contact with a metal object even if it has an exposed electrode.

According to the first aspect of the present invention,
A cradle device that supplies power to an information terminal via a connector,
A detection unit (detection unit in FIG. 1) for detecting a resistance value of the identification resistor on the information terminal side through the connector;
A determination unit (determination unit in FIG. 1) for determining whether the correct information terminal is connected according to the resistance value of the identification resistor;
A power supply unit that supplies power to the information terminal based on a determination result of the determination unit or does not supply power to the information terminal (power supply unit of FIG. 1);
A cradle device characterized by comprising:
In spite of having an exposed power supply terminal on the cradle side, it has the effect of avoiding unintentional energization that may cause a failure even when a metal piece or the like is in contact with the cradle.

The invention of claim 2 according to the present invention comprises
An information terminal that receives power supply from the cradle device according to claim 1 via a connector,
An identification resistor for identifying the information terminal;
The information terminal is configured to transmit resistance value information of the identification resistor to the cradle device through a terminal of the connector.

  As described above, according to the information terminal and the cradle device of the present invention, unintentional energization that causes a failure even when a metal piece or the like accidentally contacts despite having an exposed power supply terminal. An excellent effect of avoiding is obtained.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 3.

(Embodiment 1)
FIG. 1 is a circuit diagram of a portion related to the present invention on the information terminal side and the cradle side in Embodiment 1 of the present invention.

  In FIG. 1, 1 is a cradle and 2 is an information terminal.

  In the cradle 1, 3 is a connector for connection with the power supply device, and 4 is a connector for connection with an information terminal. Reference numeral 11 detects a resistance value by a comparator, performs determination on the upper limit side and outputs by open drain, 12 also detects resistance value by a comparator, and performs determination on the lower limit side. Reference numeral 13 indicates a transistor for comparing the comparators 11 and 12. An FET (electrolytic effect transistor) 14 is used for the purpose of inverting the output and functions as a switch between the cradle 1 and the information terminal 2.

  Reference numerals 21 and 22 denote resistors, which form a combined resistance value together with the identification resistor 53 on the information terminal 2 side. Reference numeral 23 denotes a resistor, and reference numeral 31 denotes a capacitor. The resistor 23 and the capacitor 31 constitute an integration circuit and have a function of removing noise from the input signal. Reference numerals 24 and 25 denote resistors, which divide the power supply voltage and generate a lower reference voltage. Reference numerals 26 and 27 denote resistors, which similarly divide the power supply voltage and generate an upper reference voltage. Reference numerals 28, 29, and 30 serve as resistors to pull up the comparators 11 and 12 and the transistor 13.

  Reference numeral 51 denotes a connection connector to the cradle 1 on the information terminal 2 side, which is coupled to the connector 4 on the cradle 1 side for each terminal. 52 is a circuit load on the information terminal side.

  The circuit operation of the cradle 1 and the information terminal 2 configured as described above will be described with reference to FIG.

First, the resistance value is selected so as to satisfy the following conditions.
“1” A lower reference voltage is generated by dividing the resistance of the resistor 24 and the resistor 25.
“2” The upper reference voltage is generated by the divided voltage of the resistor 26 and the resistor 27.
“3” A voltage at the time of opening the connector 4 higher than the upper reference voltage (hereinafter referred to as an open voltage) is generated by the divided voltage of the resistor 21 and the resistor 22.
“4” A voltage at the time of connector connection (hereinafter referred to as connection voltage) so that an intermediate potential between the above-mentioned upper reference voltage and lower reference voltage is obtained by the parallel connection of the identification resistor 53 and the resistor 22 and the divided voltage of the resistor 21. ) Is generated.

  That is, the resistance values are selected so that the open circuit voltage, the upper reference voltage, the connection voltage, and the lower reference voltage are in order from the highest.

  The resistor 23 and the capacitor 31 are configured to have a time constant sufficiently larger than the chattering noise so that chattering noise generated when the connector 4 and the connector 51 are attached / detached does not occur.

  The resistor 28 can be driven by the comparators 11 and 12, and a constant capable of driving the base of the transistor 13 is selected.

  The resistor 29 can be driven by the transistor 13 and a constant capable of driving the FET 14 is selected.

The operation of the electric circuit of the present invention with the constants determined as described above will be described with reference to FIG.
[1] First, the state when the information terminal side is not connected will be described. Since the connector 51 is not connected to the connector 4, the identification resistor 53 is not connected. The voltage at the time of opening is applied to the negative input terminal of the comparator 11 and the positive input terminal of the comparator 12 by the divided voltage of the resistors 21 to 22. Since this voltage is higher than both the above-mentioned upper reference voltage and lower reference voltage, the comparator 11 is at the ground potential, the comparator 12 is at the output open, the ground potential is applied to the base of the transistor 13 by the wired OR, and the transistor 13 is turned off. Thus, the FET 14 is turned off by the resistor 29, and no voltage is output to the connector 4 as a result.
[2] Next, the state when the information terminal side is connected will be described. The connector 4 and the connector 51 are connected, the identification resistor 53 is connected in parallel with the resistor 22, and the above-mentioned connection voltage is applied to the negative input terminal of the comparator 11 and the positive input terminal of the comparator 12 by voltage division with the resistor 21. Is applied. Since this voltage is lower than the above-mentioned upper reference voltage and higher than the lower reference voltage, the output of the comparator 11 is opened and the output of the comparator 12 is also opened, so that a voltage is applied to the base of the transistor 13 by the resistor 28 and the transistor 13 is As a result, the FET 14 is turned on, and a voltage is output to the connector 4 as a result.
[3] Finally, a state when the connector 4 is short-circuited with a metal object will be described. Since both ends of the resistor 22 are short-circuited, the ground potential is applied to the negative input terminal of the comparator 11 and the positive input terminal of the comparator 12. Since this voltage is lower than any of the above-described upper reference voltage, lower side, and reference voltage, the comparator 11 is open and the comparator 12 is the ground potential output. Therefore, the ground potential is applied to the base of the transistor 13 by the wired OR. The transistor 13 is turned off, and the FET 14 is turned off by the resistor 29. As a result, no voltage is output to the connector 4.

  In summary, when the connector 4 is opened and short-circuited, the power supply voltage is not output to the connector 4, and only when the information terminal 2 is connected to the connector 4, the power supply voltage is output to the connector 4.

With the above configuration and operation, the following information terminal and cradle connection form is possible.
<1> In order to make the information terminal side sturdy, the connector terminal portion, which is a weak point in strength, is not provided with a convex portion. On the other hand, the cradle side is provided with a connector having a convex portion for contact with the information terminal side connector regardless of the power supply side.
<2> Since the cradle side is the power supply side, power can be supplied even when the information terminal side has no power source or when the battery is completely discharged.
<3> Regardless of whether power is supplied from the convex part, even if the information terminal is not connected or if it is accidentally shorted with a metal object, voltage is not output to the connection connector terminal and no current flows. Does not lead to failure.

  As described above, according to the present embodiment, unintended energization can be avoided by a simple circuit configuration even when a convex terminal is provided on the power supply side.

  In the above description, the detection function is single, but a plurality of detection circuits are provided, for example, arranged at the left and right ends of the connector, and there is a normal connection only when a correct detection signal is obtained from both detection circuits. It can be considered a reliable device by allowing energization.

  In addition, by setting a plurality of ranges with appropriate resistance values, recognition of multiple types of peripheral devices corresponding to each is performed, and processing corresponding to peripheral devices such as switching the power supply voltage to be supplied by peripheral devices, for example Is possible.

  In the above judgment, the comparator is fixed by a combination of fixed resistors. However, using a microcomputer, an AD converter, and a non-volatile memory element, the change over time of the resistance value due to contact deterioration is recorded, and the resistance that changes over time. It is possible to correspond to an appropriate range for the value, and when the terminal deterioration reaches the limit due to the change over time, it is possible to stop the power supply and indicate that the use limit has been reached and prompt the exchange.

  In FIG. 1, the description has been made on the assumption that a comparator is used. However, a similar function can be realized by using a transistor.

  In addition, when the load side has a power supply unit such as a battery, the load side first supplies voltage to the supply side, and the supply side supplies power to the load side as a trigger. A configuration that avoids energization due to contact is feasible.

  The information terminal and the cradle device according to the present invention are excellent in avoiding unintentional energization that causes a failure even when a metal piece or the like is in contact with the information terminal in spite of having an exposed power supply terminal. It is useful for combining the information terminal and the cradle that can be attached and detached.

The circuit diagram of the part relevant to the present invention on the information terminal side and cradle side in Embodiment 1 of the present invention The circuit diagram of the part relevant to the present invention on the conventional information terminal side and cradle side

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cradle 2 Information terminal 3 Connection connector with power supply device 4 Connection connector with information terminal 11, 12 Comparator 13 Transistor star 14 FET (electrolytic effect transistor)
21, 22, 23, 24, 25, 26, 27, 28, 29, 30 Resistor 31 Capacitor 51 Connector to cradle 52 Circuit load on information terminal side 53 Identification resistor

Claims (2)

A cradle device that supplies power to an information terminal via a connector,
A detection unit for detecting a resistance value of the identification resistor on the information terminal side via the connector;
A discriminator for discriminating whether the correct information terminal is connected according to the resistance value of the discriminating resistor;
A power supply unit that supplies power to the information terminal based on a determination result of the determination unit or does not supply power to the information terminal;
A cradle device comprising: An information terminal that receives power supply from the cradle device according to claim 1 via a connector,
An identification resistor for identifying the information terminal;
An information terminal that transmits resistance value information of the identification resistor to the cradle device via a terminal of the connector.

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