JP2005208959A - Loss current limiting circuit and mobile terminal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To ensure that a power supply from a battery provided in a mobile terminal and a power supply obtained through the rectification of a carrier wave to a contactless IC card function are switched from one to the other, while limiting loss currents due to pulling-down. <P>SOLUTION: This loss current limiting circuit includes: a pull-down part 420 that sets the level of a signal line low when a signal line for a selection signal 414 is electrically opened; a switch part 430 that is inserted between the pull-down part and ground 422 for turning the pull-down part and the ground on and off; a power supply switch part 410 that switches a main power supply 412 and an auxiliary power supply 416 from one to the other according to the selection signal coming via the signal line; and an auxiliary power supply detection part 432 that detects that auxiliary power is being supplied. When the auxiliary power is not supplied, the switch part turns off, opening a pull-down resistance, and thus preventing loss currents. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a loss current cut-off circuit and a portable terminal that cut off a loss current flowing by pull-down.

  Conventionally, in mobile cards such as credit cards and cash cards, fixed data information such as user information and user ID (Identification) has been stored in a magnetic storage medium provided in the mobile card. In addition, the increase in capacity and miniaturization of semiconductor storage media makes it possible to embed electronic components including semiconductor storage media in mobile cards, and not only store fixed data information but also read and write advanced data information. It became possible to do. As such a portable card, there is a non-contact type IC card that reads and writes data in a non-contact type via wireless data.

  The non-contact type IC card is introduced into, for example, a railway ticket gate system, and is practically used as a ticket when passing through a ticket gate. In addition, studies have been made to increase the versatility of mobile terminals by installing such non-contact IC cards in mobile terminals such as mobile phones.

  Here, if the above non-contact type IC card is simply mounted in a portable terminal and connected to the host computer of the portable terminal, the original advantage of the non-contact type IC card that operates by receiving power from the outside is not utilized. When the terminal is not turned on, the function of the contactless IC card cannot be used. A technique is known that can solve such problems and can smoothly start processing related to a non-contact type IC card without imposing a burden on the user (for example, Patent Document 1).

  In addition, a technology of a semiconductor integrated circuit device that seamlessly switches between a power source from a battery provided in the portable terminal and a power source obtained by rectifying a carrier wave in a non-contact IC card function has been constructed (for example, Patent Document 2). ).

JP 2003-141477 A JP 2003-036427 A

  The selection signal for selecting both the power sources is operated by the power source from the battery. Therefore, the selection signal is also invalidated when the battery is decreased or cannot be used. In order to prevent such a state, a pull-down function unit is provided at the input end of the selection signal.

  However, such a pull-down function unit causes a loss current during normal use, and is a serious problem for devices that require low power consumption such as portable terminals.

  The present invention has been made in view of the above-described problems of the conventional power supply selection circuit, and an object of the present invention is to contact the power supply from the battery provided in the portable terminal in a non-contact manner while blocking the loss current caused by pull-down. To provide a new and improved loss current cut-off circuit and a portable terminal capable of surely switching between a power source obtained by rectifying a carrier wave for an IC card function.

  In order to solve the above-described problem, according to one aspect of the present invention, when a signal line is electrically opened, a pull-down unit that lowers the level of the signal line; inserted between the pull-down unit and the ground A pull-down section and a switch section for turning on and off the ground. When the switch section is on, the pull-down section functions. When the switch section is off, a loss current flowing from the signal line through the pull-down section is generated. A loss current cut-off circuit is provided, characterized in that it is cut off.

  There are three signal line levels: high level, low level, and high impedance. The pull-down function by the pull-down unit is required only when the impedance is high. With such a configuration, when the pull-down is not required, that is, when a high-level or low-level voltage is applied to the signal line, the pull-down can be turned off, and loss current generation can be prevented.

  The loss current cut-off circuit further includes a power source switching unit that switches between a main power source and an auxiliary power source according to a selection signal via the signal line. When the auxiliary power source is supplied, the switch unit is turned on and the pull-down unit is turned on. May function, and when the auxiliary power is not supplied, the switch unit may be turned off to open the pull-down unit.

  The power source switching unit selects a main power source when the selection signal is at a high level and an auxiliary power source when the selection signal is at a low level. When the main power source becomes unusable, the selection signal outputs a low level so that the auxiliary power source can be used. However, when the circuit element that generates the selection signal is operated by the main power supply, the selection signal is in an open (high impedance) state. In the above-described configuration, the pull-down unit functions by detecting the supply of the auxiliary power and it is determined that the selection signal is at the low level, so the auxiliary power can be selected as the power supply.

  The loss current cut-off circuit further includes an auxiliary power detection unit that detects that the auxiliary power is supplied, and turns on the switch when the auxiliary power supply is detected by the auxiliary power detection unit. When the auxiliary power supply is not detected, the switch unit may be turned off.

  With this configuration, it is possible to automatically detect the supply of auxiliary power. For example, when the auxiliary power source is an AC signal using a radio signal, it is detected that the carrier wave of the AC signal is equal to or higher than a predetermined level and is a carrier wave having a frequency to be received by the loss current cutoff circuit. This predetermined level may be the lowest level at which the auxiliary power supply can operate the loss current cutoff circuit.

  The selection signal may be a signal for selecting the main power supply when the main power is equal to or higher than an effective voltage to be supplied effectively. Further, the signal may be a logical product of this signal and an operation command of the semiconductor device including the loss current cutoff circuit. The effective voltage is a voltage sufficient for operating the loss current cutoff circuit, and the operation command of the semiconductor device is a non-contact type data read / write (short-range wireless standard ( This is a command issued from the functional unit as the portable terminal when performing (NFC) mode) or when transmitting / receiving data to / from the functional unit as the portable terminal.

  The near field communication (NFC) is a communication having a 13.56 MHz RF carrier frequency and a maximum communication speed of 212 Kbps, capable of non-contact communication only within a narrow range of about 10 cm. Refers to the method. In addition, both the semiconductor device including the loss current cutoff circuit and the functional unit as the portable terminal are provided in the portable terminal. The semiconductor device is mainly a non-contact IC card by NFC, and the portable terminal functional unit is input. It operates as an original portable terminal using a display unit and a display unit. The semiconductor device has, as external interfaces, a wireless interface connected to an antenna unit and the like, and a wired interface connected to a mobile terminal function unit.

  The selection signal outputs a high level so as to select the main power source when the main power source is not less than an effective voltage to be supplied effectively.

  In addition, a loss current cut-off circuit built in a portable terminal with a non-contact type read / write function for reading / writing data in a non-contact type via wireless data, the main power source being a battery of the portable terminal, the auxiliary power source The above-described loss current interrupting circuit is also provided, which is a power source obtained by rectifying a wireless AC signal supplied from the outside.

  The mobile terminal described above has a battery that can be charged by itself as a main power source, and the function as a mobile terminal and the function as a non-contact IC card are usually performed by the main power source. When the main power source becomes unusable, the function unit as a portable terminal becomes inoperable, but the function as a non-contact IC card can be operated by the auxiliary power source.

  When both the main power supply and the auxiliary power supply are supplied, exclusive control is performed by the semiconductor device including the loss current cutoff circuit, and the main power supply is selected. Since the auxiliary power supply is a radio signal, the electric energy that can be received varies depending on the distance from the separate device that generates the auxiliary power supply and the surrounding conditions. Therefore, the main power source is selected for stable and reliable non-contact communication.

  In order to solve the above-described problem, according to another aspect of the present invention, when a signal line is electrically opened, a pull-down unit that lowers the level of the signal line; and between the pull-down unit and the ground A switch unit that is inserted to turn on and off the pull-down unit and a ground; a power source switching unit that switches between a main power source and an auxiliary power source according to a selection signal via the signal line; and detects that the auxiliary power source is supplied A portable terminal having a function of a non-contact type IC card for reading and writing data in a non-contact manner via wireless data, comprising: a loss current cutoff circuit comprising an auxiliary power source detection unit for performing: When the supply of auxiliary power is detected, the switch section is turned on, the pull-down section functions, and when the supply of auxiliary power is not detected, the switch section is turned off. Characterized in that the loss current flowing through the pull-down portion from the signal line is interrupted, the mobile terminal is also provided.

  Examples of the portable terminal include a portable personal computer, a PDA (Personal Digital Assistant), and a cellular phone.

  Further, the semiconductor device provided with the above-described loss current cut-off circuit is not only a function of the non-contact type IC card as described above but also a non-contact type capable of reading / writing data from / to a separate non-contact type IC card. A reader / writer function may also be provided. Furthermore, these non-contact type communications are made according to the near field wireless standard (NFC), and the non-contact type IC card function unit such as an antenna unit may be shared.

  As described above, according to the present invention, in a loss current cutoff circuit having a non-contact IC card function or a semiconductor device or portable terminal including the same, the loss current caused by pull-down is cut off from the battery provided in the portable terminal. The power source and the power source obtained by rectifying the carrier wave for the non-contact IC card function can be switched reliably.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the present specification and drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted.

(First embodiment: use example 1)
In the present embodiment, a mobile terminal having a semiconductor device provided with a loss current interrupting circuit, particularly a mobile phone having a function as a non-contact IC card via the semiconductor device is taken as an example.

  FIG. 1 is a schematic diagram for explaining a ticket gate system using a mobile phone as a non-contact IC card in the present embodiment. In FIG. 1, a user 100 carries a mobile phone 110, and a ticket gate 112 includes a reader / writer device 114 and a ticket gate passing plate 116.

  Briefly describing the ticket gate system of FIG. 1, the user 100 takes out the mobile phone 110 and approaches the ticket gate 112. When the mobile phone 110 is placed over a reader / writer device 114 provided in the ticket gate 112, the reader / writer device 114 has a non-contact IC card (actually a non-contact IC card function built in the mobile phone 110). Semiconductor device) is detected, and communication between such devices is started.

  First, the reader / writer device 114 performs mutual authentication with the contactless IC card unit of the mobile phone 110, confirms the balance of the prepaid boarding fee, and deducts the boarding fee. When such a settlement is completed, the ticket gate passing plate 116 is placed (118), and the user 100 is allowed to pass the ticket gate. As a result, the user 110 can pass through the ticket gate 112.

(Second embodiment: use example 2)
In the present embodiment, as in the first embodiment, a mobile phone including a semiconductor device provided with a loss current cutoff circuit is taken as an example.

  FIG. 2 is a schematic diagram illustrating a merchandise settlement system that uses a mobile phone as a contactless IC card in the present embodiment. In FIG. 2, a user 100 puts a product in a shopping basket 130 and carries a mobile phone 110. The cash register 132 includes a reader / writer device 134, a settlement gate 136, and an amount display unit 138.

  The user 100 puts the product with the IC tag attached to the shopping basket 130 and passes through the settlement gate 136 provided in the cash register 132. The settlement gate 136 reads all IC tags attached to the passed product. The read result is processed by the cash register 132 and displayed on the money amount display unit 138 as a total amount. When the user 100 confirms the amount, he / she makes a payment by placing the mobile phone 110 within a predetermined range 140 of the reader / writer device 134 provided in the register 132.

  Here, the settlement gate 136 automatically reads only the IC tag attached to the product, and does not communicate with the non-contact IC card function unit of the mobile phone 110. The reason why payment is not automatically performed by the payment gate 136 is to confirm the payment amount with the user 100 and to prevent unauthorized payment. In this regard, a non-contact IC card using such a short-range wireless standard (NFC) requires processing within a predetermined communication range (about 10 cm) and is suitable for such a commodity settlement system.

  Communication between the reader / writer device 134 and the mobile phone 110 as a mobile terminal is performed by electromagnetic induction using an antenna formed of a loop coil. For example, in the present embodiment, information such as credit, prepaid, and user authority is held in a non-contact IC card unit provided in the mobile phone 110, and an electric signal based on the information is converted into an electromagnetic wave signal via an antenna, and further a reader An electrical signal is restored via the antenna of the writer device 134. In this way, settlement processing between both devices is performed.

(Third Embodiment: Semiconductor Device Provided in Mobile Terminal)
In the present embodiment, a semiconductor device having a function as a non-contact type IC card, connected to the main function of a portable terminal, and processing shared information between the two will be described.

  FIG. 3 is a block diagram showing a schematic configuration of the semiconductor device 200 as described above. The semiconductor device 200 is roughly composed of an analog unit 210, a card function unit 220, and a control unit 230.

The analog unit 210 includes a power control circuit 250 and a main power regulator 254. The power supply control circuit 250 controls the power supply of the main power supply 252 input from the MV _DD terminal, and turns on / off the output in accordance with a signal from the BAT_EN terminal or the like. The main power regulator 254 converts the electrical energy supplied from the power control circuit 250 into a power supply voltage used in the semiconductor device 200. The main power regulator 254 also has the effect of stabilizing this power supply voltage.

  The card function 220 includes an overvoltage protection circuit 260, an auxiliary power regulator 262, a modulation circuit 264, a demodulation circuit 268, a carrier wave detector 270, and a clock detector 272.

  In the overvoltage protection circuit 260, when auxiliary power rectified from an externally supplied AC signal is supplied from the CP terminal and the voltage exceeds a predetermined voltage, the voltage is discharged as a current, and the voltage is kept constant. . The limited electric energy is converted into a constant power supply voltage used in the semiconductor device 200 in the auxiliary power regulator 262. Here, although the outputs of the main power regulator 254 and the auxiliary power regulator 262 are connected to each other, either one is selected by exclusive processing of both regulators.

  The modulation circuit 264 modulates the transmission signal supplied from the SPU 288, and the modulated signal is transmitted from the antenna 266 via the wireless interface. On the other hand, the signal received from the antenna 266 is demodulated into an electrical signal that can be processed by the SPU 288 by the demodulation circuit 268 and transmitted to the SPU 288.

  The carrier detector 270 determines whether a carrier wave is included in the radio wave received by the antenna 266. When the carrier wave detector 270 determines that a carrier wave is included, a carrier wave detection signal is output from the carrier wave detector 270 to the power supply control circuit 250. The clock extractor 272 extracts a clock based on the radio wave input from the antenna 266 and supplies the extracted clock to a clock selector (not shown). The clock selector selects either the clock supplied from the clock extractor 272 or a clock of 13.56 MHz, for example, input from the outside, and supplies the selected clock to each part of the semiconductor device 200. The overall operation of the card function unit 220 is controlled by a CPU 280 of the control unit 230 described later.

The control unit 230 includes a CPU 280, a ROM 282, an EEPROM 284, an SRAM 286, an SPU 288, a DES engine 290, a CRC 292, a UART (Universal Asynchronous Receiver Transmitter) 294, an I ² C_I / F 296, an I / O 296, The components are interconnected by an internal bus.

  The CPU 280 is a main controller that comprehensively controls operations in the semiconductor device 200, and executes program codes stored in, for example, the ROM 282 or the EEPROM 284 under the control of an operating system (OS). The SRAM 286 stacks data from the CPU 280 and assists execution of the program. As an example of the operation in the CPU 280, there is execution of an application relating to processing of data transmitted / received via the card function unit 220.

  The SPU (signal processing unit) 288 performs transmission / reception processing of data modulated / demodulated via the card function unit 220. The DES engine 290 encrypts and decrypts data transmitted / received via the card function unit 220 using a procedure public key encryption. The CRC 292 performs a cyclic redundancy check of data received via the card function unit 220, that is, an error check.

Further, the UART 294, I ² C_I / F 296, and I / O 298 constitute a wired interface for the semiconductor device 200 to communicate with the main functions of a portable terminal (not shown) such as a cellular phone, a PDA, or a personal computer. To do.

  In the present embodiment, the CPU 280 receives a carrier wave detection notification from the card function unit 220 carrier wave detector 270 and performs a process corresponding thereto. The CPU 280 switches the operation mode (non-contact IC card mode, portable terminal mode) according to the state of the card function unit 220 or a command signal from an external portable terminal function unit, and the inside of the semiconductor device 200 is changed according to the communication phase. Control.

  Further, a specific address in the memory space of the SRAM 286 is assigned to an internal state flag for indicating the presence / absence of carrier wave detection from the carrier wave detector 270 and the internal state of the semiconductor device 200, and the CPU 280 is in communication state. The setting contents of the internal state flag are updated in accordance with changes in the internal state.

The main functional unit of the portable terminal connected via the wired interface of the UART 294, I ² C_I / F 296, I / O 298 can also access the SRAM 286 to detect the communication state and internal state of the semiconductor device 200. it can. Therefore, the portable terminal equipped with the semiconductor device 200 reads the information of the semiconductor device 200, displays the balance of the stored money that has been prepaid when passing through the ticket gate, and is “checkout” when using the credit function at the cash register. Etc. can be displayed.

  Further, as described above, in the semiconductor device 200, the main power supply 252 and the auxiliary power supply are selected and used. Usually, the main power supply 252 provided in the portable terminal, that is, the battery, is used for ensuring communication with a separate reader / writer device. Used. When the voltage of the battery falls below a predetermined threshold value, the function as a portable terminal is stopped, but the semiconductor device 200 that can be operated by an external auxiliary power supply operates by selecting the auxiliary power supply.

  With the above-described configuration, the mobile terminal can share the functions as the original mobile terminal and the function as a non-contact type IC card, and possess more versatile electronic devices by using both of them together. It becomes possible. In the above embodiment, the case where the semiconductor device 200 has the card function unit 220 as a non-contact type communication form has been described. However, the present invention is not limited to this case, and the card reader / writer function unit is also included. Can be configured. At this time, the reader / writer function unit can share the components such as the card function unit 220 and the antenna unit.

(Fourth embodiment: Loss current cutoff circuit provided in portable terminal)
In the present embodiment, a loss current cutoff circuit that switches between a main power source provided in a mobile terminal and an auxiliary power source generated by an external radio signal will be described.

  FIG. 4 is a block diagram showing a schematic configuration of the loss current cutoff circuit 400 as described above. The loss current interruption circuit 400 includes a power supply switching unit 410.

  The power supply switching unit 410 outputs either the main power supply 412 or the auxiliary power supply 416 as the power supply for the loss current cutoff circuit 400 in accordance with a selection signal 414 from a circuit element operated by the main power supply 412. In a normal state, the loss current cut-off circuit 400 is operated by the main power supply 412. Therefore, when the power supply from the main power supply 412 is effective, that is, when the voltage of the main power supply 412 is equal to or higher than a predetermined threshold value that allows sufficient operation of the circuit, the selection signal 414 selects the main power supply 412. The contact point C of the power supply switching unit 410 is connected to the contact point A. Here, the selection signal 414 may be a logical product of the operation command of the near field wireless standard (NFC) in addition to the threshold value.

  When the selection signal 414 is at a low level, the power supply switching unit 410 outputs an auxiliary power supply 416 supplied from the outside. That is, the contact C of the power supply switching unit 410 is connected to the contact B.

  However, under the loss current cut-off circuit 400 shown in FIG. 4, when the voltage of the main power supply 412 is lower than a predetermined threshold value and the selection signal 414 becomes invalid, the selection signal 414 is in an open (high impedance) state. It becomes. Usually, in the input of the digital element, such an open state is determined to be high level or indefinite, and the power supply output cannot be switched to the auxiliary power supply 416.

  FIG. 5 is a block diagram showing a schematic configuration of a loss current cutoff circuit 400 that solves the above-described problem. The loss current cut-off circuit 400 includes a pull-down unit connected to the selection signal 414 in addition to the power supply switching unit 410.

  The pull-down unit 420 is formed of a resistor or the like and is grounded to the ground 422. With such a configuration, even when the voltage of the main power supply 412 is lower than the threshold value and the input of the selection signal 414 is in an open state, the selection signal 414 is fixed at a low level, and the auxiliary power supply 416 can be selected as the output power supply. .

The selection signal 414 is normally supplied with a high level, and the main power supply 412 is selected. Here, when the circuit configuration including the pull-down unit 420 as described above is taken, a loss current I _loss 424 flows from the signal line of the selection signal 414 through the pull-down unit 420. This loss current I _loss is determined from the high level voltage of the selection signal 414 and the resistance value of the pull-down unit 420. The resistance value is 10 kΩ to 100 kΩ. If the resistance value is increased further, problems such as weakness against external noise and high space occupancy occur. The loss current I _loss is a serious problem for devices that require low power consumption such as portable terminals.

  FIG. 6 is a block diagram showing a schematic configuration of the improved loss current cutoff circuit 400. The loss current cutoff circuit 400 includes a power supply switching unit 410, a pull-down unit 420, a switch unit 430, and an auxiliary power supply detection unit 432. Since the power supply switching unit 410 and the pull-down unit 420 already described as components are substantially the same in function, a duplicate description is omitted.

  The switch unit 430 is inserted between the pull-down unit 420 and the ground 422 to turn on and off the pull-down unit 420 and the ground 422. In addition, the auxiliary power source detection unit 432 detects that the auxiliary power source 416 is supplied and outputs it to the switch unit 430. The switch unit 430 is turned on by a detection signal from the auxiliary power source 416.

With such a configuration, even when a high level is supplied to the selection signal 414 to use the main power supply 412, if the supply of the auxiliary power supply 416 is not detected by the auxiliary power supply detection section 432, the pull-down section 420 is opened and the loss is lost. The current I _loss is not generated.

(Fifth Embodiment: Semiconductor Device Provided in Mobile Terminal)
In the present embodiment, a semiconductor device in which the loss current cutoff circuit described in the fourth embodiment is replaced with a specific circuit block is shown.

  FIG. 7 is a block diagram schematically showing the semiconductor device according to the present embodiment. The semiconductor device 500 is an excerpt of the portion related to the present embodiment of the semiconductor device described in the third embodiment, and specifically realizes the loss current cutoff circuit described in the fourth embodiment. It is.

  The semiconductor device 500 includes a main power supply regulator 254, a power supply control circuit 250 and an auxiliary power supply regulator 262 that also function as a power supply switching unit, a carrier wave detector 270 as an auxiliary power supply detection unit, and a pulldown resistor 510 as a pulldown unit. , And a transistor 520 as a switch portion. Here, since the components already described as the components in the third embodiment have substantially the same functions, the redundant description is omitted, and the added configuration is mainly described here.

  The power supply control circuit 250 turns on / off the connection between the main power supply 252 and the main power supply regulator 254 according to the input of the BAT_EN terminal. AC power input from the outside as auxiliary power is converted into direct current by the rectifier 530 and supplied to the auxiliary power regulator 262.

The semiconductor device 500 uses one power source selected from the main power source 252 and the auxiliary power source. Normally, a high level signal is input to a BAT_EN (Battery Enable) terminal and an RF_DIS (Radio Frequency disable) terminal to select the main power supply 252. In response to this, the output of the inverter 532 in the power supply control circuit 250 becomes a low level, the main power supply 252 and the main power supply regulator 254 are connected, and the transistor 534 of the auxiliary power supply regulator 262 is turned off to turn off the auxiliary power supply regulator 262. The output is released. Therefore, the power source supplied as V _DD is only the power source by the main power source 252. Here, the transistor 520 can include a diode (not shown) as a protective element in order to prevent circuit breakdown due to a reverse voltage.

  When the auxiliary power is not supplied to the semiconductor device 500, no carrier wave is detected by the carrier wave detector 270, a low level signal is output, and the transistor 520 as the switch unit is turned off. Accordingly, the pull-down resistor 510 is in an open state, and generation of loss current can be prevented. The auxiliary power is supplied for a short time with respect to the supply time of the main power supply 252, and even if the auxiliary power is supplied while the main power supply 252 is supplied, there is no problem.

  In the circuit of FIG. 7, the main power supply 252 and the main power regulator 254 are not directly connected but via the power supply control circuit 250 when the main power supply 252 is not selected as a signal required for operation. This is because the battery is overdischarged.

  Next, the case where the main power supply 252 is consumed and becomes a predetermined threshold value or less will be described. In this state, the power supply from the main power supply 252 is closed, and a low level is not applied to the BAT_EN terminal or the RF_DIS terminal. At this time, when auxiliary power is supplied, a high level as a carrier detection signal is output to the transistor 520 from the carrier detector 270 that operates in response to the supply of the auxiliary power. The transistor 520 is turned on by this carrier wave detection signal, and the pull-down resistor 510 performs the original pull-down function. With this pull-down function, the signal line connected to the BAT_EN terminal or the RF_DIS terminal indicates a low level, the power control circuit 250 is turned off, and the auxiliary power regulator 262 is turned on. Here, the transistor 534 included in the auxiliary power supply regulator 262 operates with a power supply from the auxiliary power supply.

  In the above example, when the auxiliary power is not supplied, the transistor 520 is off, but neither power is supplied. In other words, since the semiconductor device 500 is inoperable, there is no need to shift to a special state. .

(Sixth embodiment: semiconductor device provided in portable terminal)
In the present embodiment, the signal level relationship of the semiconductor device described in the fifth embodiment will be described in detail.

  8A, 8B, and 8C are explanatory diagrams for explaining the relationship between the levels of the BAT_EN terminal and the RF_DIS terminal when the main power supply and the auxiliary power supply are supplied. Here, the logic level “1” is set when the main power supply or the auxiliary power is supplied, and the logic level “0” is set when the main power supply or auxiliary power is not supplied. For BAT_EN and RF_DIS, the high level is “1”, the low level is “0”, and the open (high impedance) is “HiZ”.

  FIG. 8A illustrates the case where the pull-down resistor 510 and the transistor 520 are omitted from FIG. Here, when the main power source is “1”, BAT_EN and RF_DIS are “1”. However, when the main power supply is 0, the BAT_EN and RF_DIS are “HiZ” 610 and cannot be switched to the intended auxiliary power supply.

  FIG. 8B illustrates a case where only the pull-down resistor 510 is connected to the BAT_EN and RF_DIS signal lines in FIG. 7 and the other end is grounded without going through the transistor 520. In this case, it is understood that when the main power source is “0”, BAT_EN and RF_DIS are “0”, and switching to the intended auxiliary power source is performed. However, when the main power supply is “1”, BAT_EN and RF_DIS are “1” 620, and a loss current flows from the signal line via the pull-down resistor 510.

  FIG. 8C illustrates the case where the transistor 520 is inserted between the pull-down resistor 510 of FIG. 8B and the ground. In such a case, when both the main power supply and the auxiliary power supply are “1”, BAT_EN and RF_DIS are “1” 630 and a loss current via the pull-down resistor 510 flows as described in FIG. 8B. However, in the normal state where the main power supply is “1” and the auxiliary power supply is “0”, the pull-down resistor 510 stops functioning when the transistor 520 is turned off, and BAT_EN and RF_DIS are “1” 632. Such a loss current does not occur. 8B is different from that explained in FIG. 8B in that when both the main power supply and the auxiliary power supply are “0”, BAT_EN and RF_DIS become “HiZ” 634. Since it is invalid and it is not necessary to operate the semiconductor device 500, “HiZ” in this state can be ignored.

(Seventh embodiment: a modification of a loss current cutoff circuit provided in a mobile terminal)
In the sixth embodiment, when both the main power supply and the auxiliary power supply are supplied, the transistor 520 serving as the switch unit is turned on, causing a loss current. This is because when the main power is disabled, the signal indicating that the main power is disabled is also disabled, and it is impossible to continuously determine that the main power is disabled. This is based on the idea of preventing loss current when power is supplied and auxiliary power is not supplied. The present embodiment is a modification of the above-described semiconductor device, and uses the main power on / off information to prevent loss current regardless of whether auxiliary power is supplied.

  FIG. 9 is a block diagram showing a schematic configuration of a loss current cutoff circuit 700 obtained by modifying the loss current cutoff circuit 400 shown in FIG. The loss current cut-off circuit 700 includes a power switching unit 410, a pull-down unit 420, a switch unit 430, and a main power-off memory holding unit 710. Since the power supply switching unit 410, the pull-down unit 420, and the switch unit 430, which have already been described as constituent elements, have substantially the same functions, a duplicate description is omitted.

  The main power off memory holding unit 710 stores the main power off signal 712 in a nonvolatile manner. This main power supply off signal 712 is externally controlled immediately after the main power supply 412 becomes ineffective, that is, in a short period of time from when it falls below a predetermined threshold voltage recognized as effective until the main power supply 412 becomes invalid. This signal is set by the unit. In the present embodiment, the high level is set in the main power-off storage holding unit 710 when the main power source 412 becomes invalid, and the low level is set when the main power source 412 becomes valid again by charging the battery.

  By configuring as described above, the switch unit 430 can be turned on only when the main power supply 412 is disabled, that is, the pull-down unit 420 can be enabled, and loss current can be prevented regardless of the supply of auxiliary power. it can.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to the example which concerns. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

  For example, in the above-described embodiment, the main power supply and the auxiliary power supply have been described using the battery of the portable terminal and the external supply power supply. In addition, a resistor is used as the pull-down unit and a transistor is used as the switch unit. However, if such a function is realized, it can be configured by other circuit elements.

  The present invention can be applied to a loss current interruption circuit and a portable terminal that interrupt a loss current flowing by pull-down.

It is the schematic explaining the ticket gate system which uses the mobile telephone in 1st Embodiment as a non-contact-type IC card. It is the schematic explaining the goods settlement system which uses the mobile telephone in 2nd Embodiment as a non-contact-type IC card. 1 is a block diagram illustrating a schematic configuration of a semiconductor device. It is a block diagram showing the schematic structure of the loss current interruption circuit. It is a block diagram showing the schematic structure of the loss current interruption circuit. It is a block diagram showing the schematic structure of the loss current interruption circuit. FIG. 10 is a block diagram schematically illustrating a semiconductor device according to a fifth embodiment. It is explanatory drawing explaining the relationship of the level of a BAT_EN terminal and RF_DIS terminal when the main power supply and auxiliary power are supplied. It is explanatory drawing explaining the relationship of the level of a BAT_EN terminal and RF_DIS terminal when the main power supply and auxiliary power are supplied. It is explanatory drawing explaining the relationship of the level of a BAT_EN terminal and RF_DIS terminal when the main power supply and auxiliary power are supplied. FIG. 7 is a block diagram illustrating a schematic configuration of a modification of the loss current cutoff circuit of FIG. 6.

Explanation of symbols

400 Loss current cut-off circuit 410 Power source switching unit 412 Main power source 414 Selection signal 416 Auxiliary power source 420 Pull-down unit 430 Switch unit 432 Auxiliary power source detection unit

Claims (6)

A pull-down section that lowers the level of the signal line when the signal line is electrically opened;
A switch unit that is inserted between the pull-down unit and the ground to turn on and off the pull-down unit and the ground;
With
A loss current cut-off circuit, wherein the pull-down unit functions when the switch unit is on, and a loss current flowing from the signal line through the pull-down unit is cut off when the switch unit is off. A power supply switching unit capable of switching between a main power supply and an auxiliary power supply according to a selection signal via the signal line;
The switch unit is turned on when the auxiliary power is supplied and the pull-down unit functions, and when the auxiliary power is not supplied, the switch unit is turned off and the pull-down unit is opened. Item 2. The loss current cutoff circuit according to Item 1. An auxiliary power detection unit for detecting that the auxiliary power is supplied;
The switch unit is turned on when supply of auxiliary power is detected by the auxiliary power source detection unit, and the switch unit is turned off when supply of auxiliary power is not detected. Loss current cutoff circuit.   3. The loss current cut-off circuit according to claim 2, wherein the selection signal is a signal for selecting a main power supply when the main power is higher than an effective voltage to be supplied effectively. A loss current cut-off circuit built in a portable terminal with a non-contact type read / write function that reads / writes data wirelessly via wireless data:
2. The loss current cut-off circuit according to claim 1, wherein the main power source is a battery of the portable terminal, and the auxiliary power source is a power source obtained by rectifying a wireless AC signal supplied from outside. A pull-down section that lowers the level of the signal line when the signal line is electrically opened;
A switch unit that is inserted between the pull-down unit and the ground to turn on and off the pull-down unit and the ground;
A power supply switching unit capable of switching between a main power supply and an auxiliary power supply according to a selection signal via the signal line;
An auxiliary power detection unit for detecting that the auxiliary power is supplied;
A portable terminal with a function of a non-contact IC card that includes a loss current cut-off circuit with a non-contact data read / write via wireless data:
When the supply of auxiliary power is detected by the auxiliary power supply detection unit, the switch unit is turned on, the pull-down unit functions, and when the supply of auxiliary power is not detected, the switch unit is turned off, and the signal line A portable terminal characterized in that a loss current flowing through a pull-down section is cut off.

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