JP4891100B2 - Power reception control device, power reception device, and electronic device - Google Patents

Description

  The present invention relates to a power reception control device, a power reception device, and an electronic apparatus.

  In recent years, contactless power transmission (contactless power transmission) that uses electromagnetic induction and enables power transmission even without a metal part contact has been highlighted. Charging of telephones and household equipment (for example, a handset of a telephone) has been proposed.

  There exists patent document 1 as a prior art of non-contact electric power transmission. In Patent Document 1, data transmission from a power receiving device (secondary side) to a power transmitting device (primary side) is realized by so-called load modulation.

However, in Patent Document 1, a general diode is used to prevent a backflow of current from the voltage output node of the power receiving device. For this reason, there has been a problem that the power loss due to the forward voltage VF of the diode is large. Moreover, in this patent document 1, the problem which may occur at the time of combined use of non-contact power transmission and an AC adapter was not considered at all.
JP 2006-60909 A

  The present invention has been made in view of the technical problems as described above, and an object of the present invention is to provide a power receiving control device and a power receiving device that enable safe and efficient use of contactless power transmission and an AC adapter. It is to provide an apparatus and an electronic device. Another object of the present invention is to provide a power reception control device, a power reception device, and an electronic device that can prevent current backflow while minimizing power loss.

  The present invention is a contactless power that electromagnetically couples a primary coil and a secondary coil to transmit power from a power transmission device to a power reception device, and supplies power to a load from a voltage output node of the power reception device. A power reception control device provided in the power reception device of a transmission system, the power reception side control circuit for controlling the power reception device, a power supply voltage generation node generated from an induced voltage of the secondary coil, and the power reception device An output assurance circuit that controls a first transistor that is provided between the voltage output node and that is turned on when power is transmitted to the load. The output assurance circuit includes an AC adapter that supplies power to the load. When connection is detected, the first transistor is set to be turned off, and when the power supply voltage is lower than an operating lower limit voltage, the first transistor Settings to turn off, related from the voltage output node to the power reception control device to prevent backflow of current to the power supply voltage generation node.

  According to the present invention, since the first transistor is turned on during power transmission to the load, it is possible to supply power to the load with little power loss. On the other hand, when the connection of the AC adapter is detected, the first transistor is turned off, and current backflow from the voltage output node to the power supply voltage generation node is prevented. Furthermore, even when the power supply voltage is lower than the operating lower limit voltage, the first transistor is turned off, and current backflow is prevented. Therefore, even when the power supply voltage is lower than the operation lower limit voltage and the power receiving side control circuit is not operating normally, the first transistor can be turned off, and the backflow of current from the AC adapter can be prevented. Therefore, contactless power transmission and safe and efficient use of the AC adapter are possible.

  The present invention further includes a voltage detection circuit that activates a voltage detection signal when the power supply voltage becomes higher than a predetermined voltage, and the output assurance circuit includes at least the voltage detection signal until the voltage detection signal becomes active. The first transistor may be set to be turned off.

  In this way, it is possible to prevent the first transistor from being turned on when the power supply voltage is lower than the predetermined voltage.

  In the present invention, the power receiving side control circuit activates an authentication completion signal when ID authentication between the power receiving device and the power transmission device is completed, and the output assurance circuit receives at least the authentication completion signal. The first transistor may be set to be turned off until it becomes active.

  In this way, it is possible to prevent a situation where the first transistor is turned on even though the ID authentication is not completed.

  The present invention further includes a connection detection circuit that activates a connection detection signal when connection of the AC adapter is detected, and the output assurance circuit includes the first detection circuit when the connection detection signal is active. The setting may be made to turn off the transistor.

  In this way, when the AC adapter is connected, the first transistor can be turned off, so that backflow of current from the AC adapter can be prevented.

  The present invention also provides a contactless power supply for transmitting power from a power transmitting device to a power receiving device by electromagnetically coupling a primary coil and a secondary coil, and supplying power to a load from a voltage output node of the power receiving device. A power reception control device provided in the power reception device of a power transmission system, wherein a power reception side control circuit that controls the power reception device, a generation node of a power supply voltage generated from an induced voltage of the secondary coil, and the power reception device An output guarantee circuit that controls a first transistor that is provided between the voltage output node and is turned on when power is transmitted to the load, wherein the output guarantee circuit includes a power supply voltage lower than an operation lower limit voltage. In relation to a power reception control device configured to set the first transistor to be turned off when the voltage is low, and to prevent a backflow of current from the voltage output node to the power supply voltage generation node That.

  According to the present invention, since the first transistor is turned on during power transmission to the load, it is possible to supply power to the load with little power loss. On the other hand, when the power supply voltage is lower than the operation lower limit voltage, the first transistor is turned off, and the backflow of current from the voltage output node to the power supply voltage generation node is prevented. Therefore, even when the power supply voltage is lower than the operation lower limit voltage and the power receiving side control circuit is not operating normally, the first transistor can be turned off and current backflow can be prevented.

  The present invention further includes a voltage detection circuit that activates a voltage detection signal when the power supply voltage becomes higher than a predetermined voltage, and the output assurance circuit includes at least the voltage detection signal until the voltage detection signal becomes active. The first transistor may be set to be turned off.

  In the present invention, the first transistor is a P-type transistor in which a voltage at the voltage output node is supplied to a source and a substrate, and a pull-up resistor is connected between the source and the gate. The circuit may turn off the first transistor by setting a signal output to the gate of the first transistor to a high impedance state.

  In this case, since the gate and the source of the first transistor have the same potential due to the pull-up resistor, the first transistor can be reliably turned off.

  In the present invention, the output guarantee circuit includes an output guarantee transistor provided between a gate node of the first transistor and a low-potential side power source, a gate node of the output guarantee transistor, and the low potential. It may also include a pull-down resistor provided between the side power supply.

  In this way, even when the power supply voltage is low, the gate node of the output assurance transistor is set to the potential of the low potential power supply by the pull-down resistor, so that the output assurance transistor can be reliably turned off.

  Further, in the present invention, a second transistor is provided between the power supply voltage generation node and the first transistor, and the power receiving side control circuit connects the second transistor during power transmission to the load. Control to turn on may be performed.

  In this way, the voltage of the power supply voltage generation node can be supplied to the voltage output node during power transmission to the load.

  In the present invention, the second transistor may be a P-type transistor whose source and substrate are supplied with the voltage of the power supply voltage generation node and whose drain is connected to the drain of the first transistor. .

  In the present invention, a second pull-up resistor and a soft start capacitor may be provided between the source and gate of the second transistor.

  In this way, the adverse effect of the inrush current when the second transistor is turned on can be reduced.

  The present invention also provides a contactless power supply for transmitting power from a power transmitting device to a power receiving device by electromagnetically coupling a primary coil and a secondary coil, and supplying power to a load from a voltage output node of the power receiving device. A power reception control device provided in the power reception device of a power transmission system, wherein a connection detection signal is detected when a connection between a power reception side control circuit that controls the power reception device and an AC adapter that supplies power to the load is detected. The power reception side control circuit is related to a power reception control device that performs control to stop power transmission of the power transmission device when the connection detection signal is active.

  According to the present invention, the connection detection circuit detects whether or not the AC adapter is connected. When connection of the AC adapter is detected, power transmission from the power transmission device to the power reception device is stopped. Therefore, the AC adapter can be prioritized over the non-contact power transmission, and the situation where the non-contact power transmission is performed even though the AC adapter is connected can be prevented. Can be prevented.

  In the present invention, the power receiving side control circuit may stop power transmission of the power transmission device by not performing ID authentication processing with the power transmission device when the connection detection signal is active. Good.

  In this way, the power transmission of the power transmission device can be stopped using the ID authentication sequence successfully, and wasteful power consumption can be prevented.

  In the present invention, when the connection detection signal is active, the power receiving side control circuit transmits an AC adapter connection command for notifying that the connection of the AC adapter is detected to the power transmission device. Thus, the power transmission of the power transmission device may be stopped.

  In this way, power transmission of the power transmission device can be stopped using the AC adapter connection command even after normal power transmission is started.

  The present invention further includes a power reception control device according to any one of the above, a power reception unit that converts an induced voltage of the secondary coil into a DC voltage, and the first transistor, and controls power supply to a load. The present invention relates to a power receiving device including a power supply control unit.

  The present invention also relates to an electronic device including the power receiving device described above and a load to which power is supplied by the power receiving device.

  Hereinafter, preferred embodiments of the present invention will be described in detail. The present embodiment described below does not unduly limit the contents of the present invention described in the claims, and all the configurations described in the present embodiment are indispensable as means for solving the present invention. Not necessarily.

1. Electronic Device FIG. 1A shows an example of an electronic device to which the contactless power transmission method of this embodiment is applied. A charger 500 (cradle) which is one of electronic devices has a power transmission device 10. A mobile phone 510 that is one of the electronic devices includes a power receiving device 40. The mobile phone 510 includes a display unit 512 such as an LCD, an operation unit 514 including buttons and the like, a microphone 516 (sound input unit), a speaker 518 (sound output unit), and an antenna 520.

  Electric power is supplied to the charger 500 via the AC adapter 502, and this electric power is transmitted from the power transmitting device 10 to the power receiving device 40 by contactless power transmission. Thereby, the battery of the mobile phone 510 can be charged or the device in the mobile phone 510 can be operated.

  Note that the electronic apparatus to which this embodiment is applied is not limited to the mobile phone 510. For example, it can be applied to various electronic devices such as a wristwatch, a cordless telephone, a shaver, an electric toothbrush, a wrist computer, a handy terminal, a portable information terminal, or an electric bicycle.

  As schematically shown in FIG. 1B, power transmission from the power transmission device 10 to the power reception device 40 is performed on the primary coil L1 (power transmission coil) provided on the power transmission device 10 side and on the power reception device 40 side. This is realized by electromagnetically coupling the secondary coil L2 (power receiving coil) formed to form a power transmission transformer. Thereby, non-contact power transmission becomes possible.

2. FIG. 2 shows a configuration example of the power transmission device 10, the power transmission control device 20, the power reception device 40, and the power reception control device 50 according to the present embodiment. A power transmission-side electronic device such as the charger 500 in FIG. 1A includes at least the power transmission device 10 in FIG. In addition, a power receiving-side electronic device such as the mobile phone 510 includes at least the power receiving device 40 and a load 90 (main load). 2, the primary coil L1 and the secondary coil L2 are electromagnetically coupled to transmit power from the power transmitting apparatus 10 to the power receiving apparatus 40, and from the voltage output node NB7 of the power receiving apparatus 40 to the load 90. On the other hand, a non-contact power transmission (non-contact power transmission) system that supplies electric power (voltage VOUT) is realized.

  The power transmission device 10 (power transmission module, primary module) can include a primary coil L1, a power transmission unit 12, a voltage detection circuit 14, a display unit 16, and a power transmission control device 20. Note that the power transmission device 10 and the power transmission control device 20 are not limited to the configuration in FIG. 2, and some of the components (for example, the display unit and the voltage detection circuit) are omitted, other components are added, and the connection relationship Various modifications such as changing the above are possible.

  The power transmission unit 12 generates an AC voltage having a predetermined frequency during power transmission, and generates an AC voltage having a different frequency according to data during data transfer, and supplies the AC voltage to the primary coil L1. Specifically, as shown in FIG. 3A, for example, when data “1” is transmitted to the power receiving device 40, an AC voltage of frequency f1 is generated and data “0” is transmitted. Generates an alternating voltage of frequency f2. The power transmission unit 12 includes at least a first power transmission driver that drives one end of the primary coil L1, a second power transmission driver that drives the other end of the primary coil L1, and a resonance circuit together with the primary coil L1. One capacitor can be included.

  Each of the first and second power transmission drivers included in the power transmission unit 12 is an inverter circuit (buffer circuit) configured by, for example, a power MOS transistor, and is controlled by the driver control circuit 26 of the power transmission control device 20.

  The primary coil L1 (power transmission side coil) is electromagnetically coupled to the secondary coil L2 (power reception side coil) to form a power transmission transformer. For example, when power transmission is necessary, as shown in FIGS. 1A and 1B, a mobile phone 510 is placed on the charger 500 so that the magnetic flux of the primary coil L1 passes through the secondary coil L2. To make sure On the other hand, when power transmission is unnecessary, the charger 500 and the mobile phone 510 are physically separated so that the magnetic flux of the primary coil L1 does not pass through the secondary coil L2.

  The voltage detection circuit 14 is a circuit that detects the induced voltage of the primary coil L1, and is provided between, for example, the resistors RA1 and RA2 or the connection node NA3 of the RA1 and RA2 and GND (low-potential side power supply in a broad sense). A diode DA1 is included. Specifically, a signal PHIN obtained by dividing the induced voltage of the primary coil L1 by the resistors RA1 and RA2 is input to the waveform detection circuit 28 of the power transmission control device 20.

  The display unit 16 displays various states of the contactless power transmission system (during power transmission, ID authentication, etc.) using colors, images, and the like, and is realized by, for example, an LED or an LCD.

  The power transmission control device 20 is a device that performs various controls of the power transmission device 10, and can be realized by an integrated circuit device (IC) or the like. The power transmission control device 20 can include a control circuit 22 (power transmission side), an oscillation circuit 24, a driver control circuit 26, and a waveform detection circuit 28.

  The control circuit 22 (control unit) controls the power transmission device 10 and the power transmission control device 20, and can be realized by, for example, a gate array or a microcomputer. Specifically, the control circuit 22 performs various sequence control and determination processes necessary for power transmission, load detection, frequency modulation, foreign object detection, and attachment / detachment detection.

  The oscillation circuit 24 is constituted by a crystal oscillation circuit, for example, and generates a primary side clock. The driver control circuit 26 generates a control signal having a desired frequency based on the clock generated by the oscillation circuit 24, the frequency setting signal from the control circuit 22, and the like, and the first and second power transmission drivers of the power transmission unit 12. To control the first and second power transmission drivers.

  The waveform detection circuit 28 monitors the waveform of the signal PHIN corresponding to the induced voltage at one end of the primary coil L1, and performs load detection, foreign object detection, and the like. For example, when the load modulation unit 46 of the power reception device 40 performs load modulation for transmitting data to the power transmission device 10, the signal waveform of the induced voltage of the primary coil L1 changes as shown in FIG. . Specifically, when the load modulation unit 46 reduces the load to transmit data “0”, the amplitude (peak voltage) of the signal waveform decreases, and when the load increases to transmit data “1”, The amplitude of the signal waveform increases. Therefore, the waveform detection circuit 28 performs peak hold processing of the signal waveform of the induced voltage and determines whether or not the peak voltage exceeds the threshold voltage, so that the data from the power receiving device 40 is “0”. Whether it is “1” or not. Note that the method of waveform detection is not limited to the method of FIGS. 3 (A) and 3 (B). For example, whether the load on the power receiving side has increased or decreased may be determined using a physical quantity other than the peak voltage.

  The power reception device 40 (power reception module, secondary module) can include a secondary coil L2, a power reception unit 42, a load modulation unit 46, a power supply control unit 48, and a power reception control device 50. The power reception device 40 and the power reception control device 50 are not limited to the configuration in FIG. 2, and various modifications such as omitting some of the components, adding other components, and changing the connection relationship. Is possible.

  The power receiving unit 42 converts the AC induced voltage of the secondary coil L2 into a DC voltage. This conversion is performed by a rectifier circuit 43 included in the power receiving unit 42. The rectifier circuit 43 includes diodes DB1 to DB4. The diode DB1 is provided between the node NB1 at one end of the secondary coil L2 and the generation node NB3 of the DC voltage VDC, and DB2 is provided between the node NB3 and the node NB2 at the other end of the secondary coil L2. , DB3 is provided between the node NB2 and the VSS node NB4, and DB4 is provided between the nodes NB4 and NB1.

  The resistors RB1 and RB2 of the power receiving unit 42 are provided between the nodes NB1 and NB4. A signal CCMPI obtained by dividing the voltage between the nodes NB1 and NB4 by the resistors RB1 and RB2 is input to the frequency detection circuit 60 of the power reception control device 50.

  The capacitor CB1 and the resistors RB4 and RB5 of the power receiving unit 42 are provided between the node NB3 of the DC voltage VDC and the node NB4 of VSS. A signal ADIN obtained by dividing the voltage between the nodes NB3 and NB4 by the resistors RB4 and RB5 is input to the position detection circuit 56 of the power reception control device 50.

  The load modulation unit 46 performs load modulation processing. Specifically, when desired data is transmitted from the power receiving device 40 to the power transmitting device 10, the load at the load modulation unit 46 (secondary side) is variably changed in accordance with the transmission data, and FIG. As shown, the signal waveform of the induced voltage of the primary coil L1 is changed. For this purpose, the load modulation unit 46 includes a resistor RB3 and a transistor TB3 (N-type CMOS transistor) provided in series between the nodes NB3 and NB4. The transistor TB3 is on / off controlled by a signal P3Q from the control circuit 52 of the power reception control device 50. When the load modulation is performed by controlling on / off of the transistor TB3, the transistors TB1 and TB2 of the power supply control unit 48 are turned off, and the load 90 is not electrically connected to the power receiving device 40.

  For example, as shown in FIG. 3B, when the secondary side is set to a low load (impedance is large) in order to transmit data “0”, the signal P3Q becomes L level and the transistor TB3 is turned off. As a result, the load of the load modulator 46 becomes almost infinite (no load). On the other hand, when the secondary side is set to a high load (low impedance) in order to transmit data “1”, the signal P3Q becomes H level and the transistor TB3 is turned on. As a result, the load of the load modulation unit 46 becomes the resistance RB3 (high load).

  The power supply control unit 48 controls power supply to the load 90. The regulator 49 adjusts the voltage level of the DC voltage VDC obtained by the conversion in the rectifier circuit 43 to generate the power supply voltage VD5 (for example, 5V). The power reception control device 50 operates by being supplied with the power supply voltage VD5, for example.

  The transistor TB2 (P-type CMOS transistor) is provided between the generation node NB5 (output node of the regulator 49) of the power supply voltage VD5 and the transistor TB1 (node NB6), and receives a signal from the control circuit 52 of the power reception control device 50. Controlled by P1Q. Specifically, the transistor TB2 is turned on when ID authentication is completed (established) and normal power transmission is performed, and turned off when load modulation is performed. A pull-up resistor RU2 is provided between the power supply voltage generation node NB5 and the node NB8 of the gate of the transistor TB2.

  The transistor TB1 (P-type CMOS transistor) is provided between the transistor TB2 (node NB6) and the voltage output node NB7 of VOUT, and is controlled by a signal P4Q from the output guarantee circuit 54. Specifically, it is turned on when ID authentication is completed and normal power transmission is performed. On the other hand, when the connection of the AC adapter is detected or the power supply voltage VD5 is smaller than the operation lower limit voltage of the power reception control device 50 (control circuit 52), the power supply voltage VD5 is turned off. A pull-up resistor RU1 is provided between the voltage output node NB7 and the node NB9 of the gate of the transistor TB1.

  The power reception control device 50 is a device that performs various controls of the power reception device 40 and can be realized by an integrated circuit device (IC) or the like. The power reception control device 50 can be operated by a power supply voltage VD5 generated from the induced voltage of the secondary coil L2. The power reception control device 50 can include a control circuit 52 (power reception side), an output guarantee circuit 54, a position detection circuit 56, an oscillation circuit 58, a frequency detection circuit 60, and a full charge detection circuit 62.

  The control circuit 52 (control unit) controls the power receiving device 40 and the power receiving control device 50, and can be realized by, for example, a gate array or a microcomputer. Specifically, the control circuit 52 performs various sequence control and determination processes necessary for ID authentication, position detection, frequency detection, load modulation, full charge detection, and the like.

  The output guarantee circuit 54 is a circuit that guarantees the output of the power receiving device 40 at a low voltage (at 0 V). In other words, the transistor TB1 is controlled, and when the connection of the AC adapter is detected or the power supply voltage VD5 is smaller than the operation lower limit voltage, the transistor TB1 is set to be turned off, and the current from the voltage output node NB7 to the power receiving device 40 side is set. Prevent backflow.

  The position detection circuit 56 monitors the waveform of the signal ADIN corresponding to the waveform of the induced voltage of the secondary coil L2, and determines whether the positional relationship between the primary coil L1 and the secondary coil L2 is appropriate. Specifically, the signal ADIN is converted into a binary value by a comparator, and it is determined whether or not the positional relationship is appropriate.

  The oscillation circuit 58 is constituted by a CR oscillation circuit, for example, and generates a secondary clock. The frequency detection circuit 60 detects the frequency (f1, f2) of the signal CCMPI and determines whether the transmission data from the power transmission device 10 is “1” or “0” as shown in FIG. To do.

  The full charge detection circuit 62 (charge detection circuit) is a circuit that detects whether or not the battery 94 of the load 90 is in a fully charged state (charged state). Specifically, the full charge detection circuit 62 detects the full charge state by detecting on / off of the LEDR used for displaying the charge state, for example. That is, when the LEDR is extinguished continuously for a predetermined time (for example, 5 seconds), it is determined that the battery 94 is fully charged (charging is completed).

  The load 90 includes a charge control device 92 that performs charge control of the battery 94 and the like. The charge control device 92 (charge control IC) can be realized by an integrated circuit device or the like. Note that, like a smart battery, the battery 94 itself may have the function of the charging control device 92.

3. Output Assurance Circuit In FIG. 4A, a mobile phone 510 (electronic device, portable device in a broad sense) has a built-in power receiving device 40, and contactless power with a charger 500 (electronic device in a broad sense). The battery can be charged by transmission. On the other hand, the mobile phone 510 is also provided with a connection terminal of an AC adapter 522 (external power supply device in a broad sense), and the battery can be charged by connecting the AC adapter 522.

  If the contactless power transmission and the AC adapter 522 can be used together as shown in FIG. 4A, the mobile phone 510 can be used by using the compact AC adapter 522 even when the charger 500 is not held at the place of going. Can be charged and convenience can be improved.

  However, when the mobile phone 510 is placed on the charger 500 and the AC adapter 522 is connected to the mobile phone 510, or the mobile phone 510 is placed on the charger 500 with the AC adapter 522 connected, the AC adapter It has been found that there is a problem that current flows backward from the 522 side to the power receiving device 40 side. In addition, there is a problem that it is wasteful to perform contactless power transmission even though the AC adapter 522 is connected.

  Further, as shown in FIG. 4B, a method of providing a general discrete diode DD4 between the voltage output node NB7 and the node NB6 in order to prevent the backflow of current from the AC adapter 522 side is also considered. It is done. However, according to this method, in the case of normal power transmission, a voltage drop is generated by the forward voltage VF of the diode DD4, so that there is a problem that power loss is large.

  Therefore, in the present embodiment, when the connection of the AC adapter 522 is detected, the AC adapter 522 is prioritized over the contactless power transmission, and a method of supplying power to the load by the AC adapter 522 is adopted. . In addition, a method is employed in which the backflow of current from the AC adapter 522 is prevented by a transistor (parasitic diode) instead of a normal diode.

  FIG. 5 shows a configuration example of the power supply control unit 48 and the like. The control circuit 52 is supplied with the power supply voltage VD5 generated from the induced voltage of the coil L2, and controls the power receiving device 40.

  The first transistor TB1 is provided between the generation node NB5 of the power supply voltage VD5 and the voltage output node NB7 of the power receiving device 40, and is turned on when power is transmitted to the load 90. Specifically, the transistor TB1 is a P-type transistor in which the voltage VOUT of the voltage output node NB7 is supplied to the source and substrate (substrate), and the pull-up resistor RU1 is connected between the source and gate.

  The second transistor TB2 is provided between the power supply voltage generation node NB5 and the transistor TB1, and is turned on when power is transmitted to the load 90. Specifically, the transistor TB2 is a P-type transistor whose source and substrate are supplied with the voltage VD5 of the power supply voltage generation node NB5 and whose drain is connected to the drain of the transistor TB1. A second pull-up resistor RU2 is provided between the source and gate of the transistor TB2. Then, the control circuit 52 on the power receiving side performs control to turn on the transistor TB2 by setting the signal P1Q to the L level during power transmission to the load 90. On the other hand, in a period before the completion of ID authentication, such as a load modulation period, control is performed to turn off the transistor TB2 by setting the signal P1Q to the H level.

  The output guarantee circuit 54 sets the signal P4Q and controls the transistor TB1. Specifically, when connection of the AC adapter 522 that supplies power to the load 90 is detected, a setting is made to turn off the transistor TB1. Further, when the power supply voltage VD5 is lower than the operation lower limit voltage (for example, 1.5 V) of the circuit such as the control circuit 52, the transistor TB1 is set to be turned off. This prevents the current from the AC adapter 522 from flowing backward from the voltage output node NB7 of VOUT to the power supply voltage generation node NB5 of VD5. The operating lower limit voltage (minimum operating voltage) is a voltage that can guarantee the normal operation of the circuit (a voltage at which the inverter circuit etc. operates normally). For example, the threshold voltage of the P-type transistor and the N-type transistor This voltage is equivalent to the sum of threshold voltages.

  For example, FIG. 6 shows a device cross-sectional view of a P-type transistor TB1. The voltage VOUT is supplied to the source 404 (P-type impurity region) and the substrate 400 (N-type well) of the transistor TB1. Specifically, the substrate 400 is set to the potential of the voltage VOUT through the N-type impurity region 402. The node NB6 is connected to the drain of the transistor TB1. The “substrate” is a region where a transistor is formed. In this embodiment, an N-type well formed in a P-type well (P-type substrate) as shown in FIG. 6 is also called a “substrate”.

  With the connection as shown in FIG. 6, a parasitic diode DD1 is formed between the drain 406 of the transistor TB1 and the substrate 400. The diode DD1 is a diode having a forward direction from the node NB6 to the NB7. Therefore, when the AC adapter 522 that outputs the power supply voltage is connected to the node NB7, the parasitic diode DD1 can prevent the current from the AC adapter 522 from flowing back to the node NB6.

  The transistor TB1 is turned on when the signal P4Q becomes L level during normal power transmission. At this time, the current from the node NB6 to the NB7 flows through the channel of the transistor TB1, not the parasitic diode DD1. Therefore, unlike the case of FIG. 4B, there is no voltage drop due to the forward voltage VF of the diode, so that the power loss in the transistor TB1 can be minimized.

  That is, in FIG. 5, when the connection of the AC adapter 522 that supplies power to the voltage output node NB7 is detected, the transistor TB1 is turned off under the control of the output guarantee circuit 54 (control circuit 52). Specifically, based on a signal from the control circuit 52 (connection detection circuit), the signal P4Q enters a high impedance state, and the transistor TB1 is turned off. Accordingly, the parasitic diode DD1 of the transistor TB1 functions as a backflow prevention diode, and current backflow from the AC adapter 522 to the power receiving device 40 is prevented. As a result, the voltage from the AC adapter 522 is transmitted to the power supply voltage generation node VD5, and a situation in which a malfunction occurs can be prevented.

  In FIG. 5, the control circuit 52 operates with the power supply voltage VD5 generated by contactless power transmission. The contactless power transmission is not always performed. For example, when the mobile phone 510 is separated from the charger 500 in FIG. 4A, the contactless power transmission is completed and the power supply voltage VD5 is supplied to the control circuit 52. Disappear. Therefore, if the transistor TB1 is turned on / off only by a signal from the control circuit 52 without providing the output guarantee circuit 54 of FIG. 5, the transistor TB1 cannot be turned off when the power supply voltage VD5 is not supplied. There is a problem that backflow cannot be prevented. That is, in FIG. 4A, if the mobile phone 510 is separated from the charger 500 with the AC adapter 522 connected, the transistor TB1 cannot be turned off, so that the current from the AC adapter 522 flows backward to the power supply voltage generation node NB5. End up. As a result, an unintended voltage appears at the node NB5, which may cause a system malfunction.

  In this regard, in FIG. 5, the output assurance circuit 54 performs a setting to turn off the transistor TB1 when the power supply voltage VD5 is lower than the operation lower limit voltage.

  Specifically, the output assurance circuit 54 sets the signal P4Q output to the gate of the transistor TB1 to a high impedance state. Thus, the nodes NB7 and NB9 are set to the same potential by the pull-up resistor RU1, and the transistor TB1 is turned off. Therefore, even when the power supply voltage VD5 is lower than the operation lower limit voltage, the reverse flow of the current from the AC adapter 522 can be prevented by the diode DD1.

  On the other hand, in normal power transmission, turning on the transistor TB1 realizes efficient power transmission without voltage drop due to the diode. Therefore, according to this embodiment, contactless power transmission and an AC adapter can be used safely and efficiently.

4). Detailed Configuration Example FIG. 7 shows a detailed configuration example of the output assurance circuit 54 and the control circuit 52, and FIGS. 8A and 8B show signal waveform examples for explaining the operation of these circuits. .

  The output guarantee circuit 54 in FIG. 7 includes an output guarantee transistor TD1 (N-type CMOS transistor) provided between the node NB9 of the gate of the transistor TB1 and GND (low potential side power supply), and a gate of the transistor TD1. A pull-down resistor RDW provided between the nodes ND1 and GND is included to constitute an N-type open drain transistor.

  According to this output guarantee circuit 54, even when the power supply voltage VD5 becomes lower than the operation lower limit voltage and the signal CNT from the control circuit 52 is in an indefinite state, the node ND1 is at the GND level (for example, 0 V) by the pull-down resistor RDW. Set to As a result, the transistor TD1 is turned off and the signal P4Q is set to a high impedance (HIZ) state, so that the nodes NB7 and NB9 have the same potential by the pull-up resistor RU1. As a result, even when the transistor TB1 is turned off and the power supply voltage VD5 is lower than the operation lower limit voltage, it is possible to prevent a reverse current flow.

  The voltage detection circuit 72 (low voltage detection circuit) performs a power supply voltage detection process. Specifically, as indicated by A1 in FIG. 8A, when the power supply voltage VD5 becomes higher than a predetermined voltage (operation lower limit voltage), the voltage detection signal XVDET is made active (L level). “X” in XVDET means negative logic. Then, the output guarantee circuit 54 performs setting to turn off the transistor TB1 until at least the voltage detection signal XVDET becomes active. That is, the transistor TD1 is turned off and the signal P4Q is set to a high impedance state.

  When the ID authentication between the power transmission device 10 and the power receiving device 40 is completed (established), the control circuit 52 activates the authentication completion signal XIDCMP (L level) as indicated by A2 in FIG. To do. Note that “X” in XIDCMP means negative logic. Then, the output guarantee circuit 54 performs a setting to turn off the transistor TB1 at least until the authentication completion signal XIDCMP becomes active.

  The connection detection circuit 74 performs connection detection processing for the AC adapter 522. Specifically, as shown at B1 in FIG. 8B, when the connection of the AC adapter 522 is detected, the connection detection signal ACDET is made active (H level). Then, the output guarantee circuit 54 performs a setting to turn off the transistor TB1 when the connection detection signal ACDET is active.

  Specifically, the control circuit 52 is provided with a NOR circuit NORD (logic gate in a broad sense). The NORD receives signals XVDET, XIDCMP, and ACDET, and outputs a signal CNT to the output guarantee circuit 54. When either of the signals XVDET and XIDCMP is at H level (inactive), the signal CNT becomes L level (inactive) and the transistor TD1 is turned off. As a result, the transistor TB1 is turned off and current backflow is prevented.

  On the other hand, when the signals XVDET and XIDCMP are both at L level (active) and the signal ACCDET is at L level (inactive), the signal CNT becomes H level (active) as indicated by A3 in FIG. Become. That is, when all of the signals XVDET, XIDCMP, and ACDET are at L level, the signal CNT becomes H level and the transistor TD1 is turned on. As a result, the signal P4Q becomes L level, the transistor TB1 is turned on, and normal power transmission by non-contact power transmission becomes possible.

  Further, as shown at B1 in FIG. 8B, when the connection of the AC adapter 522 is detected and the signal ACDET becomes H level (active), the signal CNT is unconditionally set at L level (inactive) as shown at B2. And the transistor TD1 is turned off. As a result, the transistor TB1 is turned off and the backflow of the current from the AC adapter 522 is prevented.

  According to the configuration of FIG. 7, the NOR circuit NORD does not operate normally because the power supply voltage VD5 is low, and the transistor TD1 is turned off by the pull-down resistor RDW and the transistor TB1 is turned off even when the signal CNT is indefinite. Therefore, the reverse current can be prevented. When the power supply voltage VD5 rises normally, ID authentication is completed, and the signals XVDET and XIDCMP become L level, the transistors TD1 and TB1 are turned on, and normal power transmission can be started. On the other hand, when the connection of the AC adapter 522 is detected, the signal CNT is unconditionally set to the L level, and the transistors TD1 and TB1 are turned off, so that the backflow of current from the AC adapter 522 can be prevented immediately.

  Note that the configurations of the output assurance circuit 54, the control circuit 52, and the like of the present embodiment are not limited to those shown in FIG. That is, the output guarantee circuit 54 performs a setting to turn off the transistor TB1 at least when the power supply voltage VD5 is lower than the operation lower limit voltage (predetermined voltage), thereby preventing a backflow of current from the voltage generation node NB7. Any circuit can be used. Alternatively, any circuit may be used as long as the transistor TB1 is set to be turned off until the ID authentication between the power transmission device 10 and the power reception device 40 is completed, and the backflow of the current from the voltage generation node NB7 is prevented. For example, a modification in which the voltage detection circuit 72 is not provided or the connection detection circuit 74 is not provided is possible. Further, it is possible to modify the constituent elements of the output guarantee circuit 54 or to add other constituent elements.

  FIG. 9A shows a configuration example of the voltage detection circuit 72. The voltage detection circuit 72 includes resistors RE1 and RE2 provided in series between the power supply voltages VD5 and GND, a current source IS1 provided in series between VD5 and GND, and an N-type transistor TE1. The connection node NE1 of the resistors RE1 and RE2 is connected to the gate of the transistor TE1, and the voltage detection signal XVDET is output from the connection node NE2 of the current source IS1 and transistor TE1. In FIG. 9A, since the transistor TE1 is turned off when the power supply voltage VD5 is lower than a predetermined voltage (for example, 1.5 V) set as the operation lower limit voltage, the signal XVDET is at the level of VD5. . On the other hand, when the power supply voltage VD5 is higher than a predetermined voltage (for example, 1.5 V), the transistor TE1 is turned on, so that the signal XVDET becomes L level.

  FIG. 9B shows a configuration example of the connection detection circuit 74. The connection detection circuit 74 includes resistors RE3 and RE4 and an operational amplifier OPE (comparator) provided in series between the output node of the voltage VAC of the AC adapter 522 and GND. A connection node NE3 of resistors RE3 and RE4 is connected to the non-inverting input terminal of the operational amplifier OPE, and the reference voltage VREF is input to the inverting input terminal. In FIG. 9B, when the output voltage VAC of the AC adapter 522 becomes higher than a predetermined voltage (for example, 4.0 to 4.5 V) and the voltage of the node NE3 becomes higher than the reference voltage VREF, the output of the operational amplifier OPE A certain connection detection signal ACDET becomes H level.

5. First Modification Next, a first modification of the present embodiment will be described. For example, in FIG. 10, the connection detection circuit 74 of the AC adapter 522 is provided, but the transistor TB1 and the output guarantee circuit 54 of FIG. 5 are not provided, and a diode DD4 is provided instead. The diode DD4 is a diode whose forward direction is from the node NB6 to the NB7, and prevents reverse current flow when the AC adapter 522 is connected. Providing such a diode DD4 has the advantage that there is a voltage drop due to the forward voltage VF during normal power transmission and power efficiency is deteriorated, but the output guarantee circuit 54 is not required.

  In FIG. 10, the connection detection circuit 74 activates the connection detection signal ACDET when the connection of the AC adapter 522 that supplies power to the load 90 is detected. Then, the control circuit 52 on the power receiving side performs control to stop the power transmission of the power transmission device 10 when the connection detection signal ACDET is active. By doing in this way, when the AC adapter 522 is connected, contactless power transmission is stopped, so that useless power can be prevented from being consumed.

  In other words, when the AC adapter 522 is connected, it is sufficient to charge the battery 94 with the output voltage VAC from the AC adapter 522. When contactless power transmission is performed, power is wasted on the power transmission side. Will happen. In this regard, such a situation can be prevented if power transmission of the power transmission device 10 by contactless power transmission is stopped when connection of the AC adapter 522 is detected.

  The stop of the power transmission of the power transmission device 10 can be realized by the following method, for example. For example, in the first method, when the connection detection signal ACDET is active, the control circuit 52 on the power receiving side stops the power transmission of the power transmission device 10 so as not to perform the ID authentication process with the power transmission device 10. Let

  Specifically, when the AC adapter 522 is not connected, the power reception control device 50 performs an ID authentication process when the reset is released by power transmission for position detection from the power transmission device 10 or the like. That is, an authentication frame that informs its own ID is transmitted to the power transmission device 10. When the permission frame is received from the power transmission device 10, the ID authentication process is completed. After that, a power transmission start frame is transmitted to the power transmission device 10, thereby starting normal power transmission.

  On the other hand, when the connection detection circuit 74 detects the connection of the AC adapter 522, the power reception control device 50 does not perform the ID authentication process after the reset is released. In this way, the power transmission device 50 determines that the electronic device on the power receiving side is a foreign object or the like, and thus does not perform normal power transmission. Thereby, it is possible to prevent unnecessary contactless power transmission from being performed when the AC adapter 522 is connected.

  In the second method, when the connection detection signal ACDET is active, the control circuit 52 on the power receiving side transmits an AC adapter connection command (connection flag) to the power transmission device 10, thereby Stop power transmission. This AC adapter connection command is a command (frame) for notifying the power transmission apparatus 10 that the connection of the AC adapter 522 has been detected.

  Specifically, for example, as shown in FIG. 4A, the mobile phone 510 is placed on the charger 500, the ID authentication is completed, and normal power transmission is performed, and the AC adapter 522 is connected to the mobile phone 510. May be connected to. In such a case, since the ID authentication has already been completed, the power transmission of the power transmission device 10 cannot be stopped by the first method described above.

  In this regard, in the second method, such connection of the AC adapter 522 is constantly monitored, and when a connection is detected, an interrupt is generated and an AC adapter connection command is transmitted to the power transmission apparatus 10. Specifically, for example, an AC adapter connection command is transmitted by load modulation of the load modulation unit 46. In this way, even when the AC adapter 522 is connected in a state where normal power transmission is performed, power transmission of the power transmission device 10 can be stopped immediately, and useless contactless power transmission is continued. Can be prevented. That is, after the AC adapter 522 is connected, contactless power transmission by the power transmission device 10 is stopped, and the battery 94 is charged by the power from the AC adapter 522.

  Note that the power transmission stopping method of the power transmission device according to the first modification can be realized not only by the circuit having the configuration shown in FIG. 10 but also by the circuit having the configuration described with reference to FIGS. For example, when applied to the circuit having the configuration shown in FIG. 7, when connection of the AC adapter 522 is detected, the transistor TB1 is turned off to prevent backflow, and ID authentication processing is not performed or an AC adapter connection command is transmitted. Thus, the power transmission of the power transmission device 10 may be stopped.

6). Second Modification Example Next, a second modification example of the present embodiment will be described. In the second modification, the functions of the transistors TB1 and TB2 in FIG. 5 are realized by one transistor. That is, in FIG. 5, the two transistors TB1 and TB2 are used for preventing the backflow of current from the AC adapter 522 and controlling the power supply to the load 90, but this is realized with only one transistor.

  For example, in order to prevent the backflow of current from the AC adapter 522, as shown in FIG. 11A, the substrate of the P-type transistor TF is connected to the voltage output node NB7 side of VOUT. That is, the switch means SW1 is turned on and the switch means SW2 is turned off to supply the voltage of VOUT to the substrate. Then, the transistor TF is turned off by the signal PQ. In this way, the parasitic diode DD1 is formed between the nodes NB7 and NB5 as described with reference to FIG. 6, and the reverse flow of current from the node NB7 to NB5 can be prevented by the diode DD1. That is, the transistor TF can function as the transistor TB1 in FIG. In this case, it is desirable to control the signal PQ by the output guarantee circuit 54 as well.

  On the other hand, when normal power transmission is performed, the substrate of the transistor TF is connected to the generation node NB5 side of the power supply voltage VD5 as shown in FIG. That is, the switch means SW2 is turned on and the switch means SW1 is turned off to supply the voltage of VD5 to the substrate. Then, the transistor TF is turned on by the signal PQ. In this way, normal power transmission becomes possible. That is, the transistor TF can function as the transistor TB2 in FIG.

7). Third Modification Next, a third modification of the present embodiment will be described. In the third modification, the inrush current when the power supply control transistor is turned on is reduced, and soft start is realized.

  For example, in FIG. 12A, when the power supply control transistor TB2 is turned on at the start of normal power transmission, an inrush current from the node NB5 to NB6 is generated. When such an inrush current occurs, a surge may be applied to the power supply voltage VD5 as shown in FIG. 12B, and the power reception control device 50 may be reset. When the power reception control device 50 is reset, although the ID authentication is completed and power transmission is started, the sequence state is returned to the reset state, and the ID authentication is performed again.

  For this reason, in FIG. 12A, a soft-start capacitor CSF is provided in parallel with the second pull-up resistor RU2 between the source and gate of the second transistor TB2. In this way, when normal power transmission is started and the transistor TB2 is turned on, the steep voltage change of VD5 as shown in FIG. 12B can be mitigated by the capacitor CSF. Therefore, the situation where the power reception control device 50 is reset can be prevented, and a stable operation of contactless power transmission can be realized.

  The method for realizing the soft start is not limited to the method for providing the soft start capacitor CSF. For example, when turning on the transistor TB2, a method of slowly changing the voltage level of the signal P1Q from the H level to the L level may be employed.

8). Operation Next, an outline of the operation on the power transmission side and the power reception side in the present embodiment will be described with reference to the flowcharts of FIGS.

  When the power transmission side is powered on and powered on (step S1), the power transmission side performs temporary power transmission for position detection (step S2). By this power transmission, the power supply voltage on the power receiving side rises and the reset of the power reception control device 50 is released (step S11). Then, the power receiving side sets the signal P1Q to the H level and sets the signal P4Q to the high impedance state (step S12). As a result, the transistors TB2 and TB1 are both turned off, and the electrical connection with the load 90 is interrupted.

  Next, the power receiving side uses the position detection circuit 56 to determine whether or not the positional relationship between the primary coil L1 and the secondary coil L2 is appropriate (step S13). If the positional relationship is appropriate, the power receiving side starts an ID authentication process and transmits an authentication frame to the power transmission side (step S14). Specifically, authentication frame data is transmitted by the load modulation described with reference to FIG.

  When the power transmission side receives the authentication frame, the power transmission side performs determination processing such as whether or not the IDs match (step S3). When the ID authentication is permitted, a permission frame is transmitted to the power receiving side (step S4). Specifically, data is transmitted by the frequency modulation described with reference to FIG.

  The power receiving side receives the permission frame and, if the content is OK, transmits a start frame for starting contactless power transmission to the power transmitting side (steps S15 and S16). On the other hand, the power transmission side receives the start frame and starts normal power transmission when the content is OK (steps S5 and S6). The power receiving side sets the signals P1Q and P4Q to the L level (step S17). As a result, both the transistors TB2 and TB1 are turned on, so that power transmission to the load 90 is possible, and power supply to the load (output of VOUT) starts (step S18).

  14 and 15 are flowcharts for explaining a power transmission stopping method when AC adapter connection is detected. As shown in FIG. 14, after the reset is released and the signal P1Q is set to the H level and the signal P4Q is set to the high impedance state (steps S11 and S12), it is detected whether or not the AC adapter 522 is connected ( Step S12-2). If connection of the AC adapter is detected, after waiting for a predetermined time (step S12-3), the process returns to step S12. In this way, when the connection of the AC adapter 522 is detected, the authentication frame is not transmitted in step S14, and ID authentication is not performed. Therefore, when the connection of the AC adapter 522 is detected, power transmission from the power transmission side is stopped, so that a situation in which useless contactless power transmission is performed can be prevented.

  FIG. 15 shows a process that is always performed in a normal power transmission state, for example. That is, in this state, when connection of the AC adapter is detected on the power receiving side (step S31), an AC adapter connection interrupt is generated (step S32). Then, the power receiving side transmits an AC adapter connection command to the power transmission side by load modulation (step S33). When receiving the AC adapter connection command (step S21), the power transmission side shifts to the standby mode and stops power transmission (step S22). Thus, for example, in FIG. 4A, contactless power transmission can be stopped even when the AC adapter 522 is connected with the mobile phone 510 placed on the charger 500, which is useless. Power consumption can be prevented.

  Although the present embodiment has been described in detail as described above, it will be easily understood by those skilled in the art that many modifications can be made without departing from the novel matters and effects of the present invention. Accordingly, all such modifications are intended to be included in the scope of the present invention. For example, in the specification or drawings, terms (AC adapter, GND, mobile phone / charger, etc.) described at least once together with different terms (external power supply device, low-potential side power supply, electronic device, etc.) in a broader sense or the same meaning ) May be replaced by the different terms anywhere in the specification or drawings. All combinations of the present embodiment and the modified examples are also included in the scope of the present invention. Further, the configuration and operation of the power reception control device, the output guarantee circuit, and the control circuit, and the power transmission method when detecting the AC adapter connection are not limited to those described in the present embodiment, and various modifications can be made.

1A and 1B are explanatory diagrams of contactless power transmission. Configuration examples of the power reception device, the power reception control device, and the like according to the present embodiment. 3A and 3B are explanatory diagrams of data transfer by frequency modulation and load modulation. 4A and 4B are explanatory diagrams of a problem when the AC adapter is connected. Configuration example of output guarantee circuit, control circuit, etc. The device sectional view of a transistor. A detailed configuration example of an output guarantee circuit, a control circuit, and the like. 8A and 8B are signal waveform examples for explaining the operation of this embodiment. 9A and 9B are configuration examples of a voltage detection circuit and a connection detection circuit. Explanatory drawing of the 1st modification of this embodiment. FIG. 11A and FIG. 11B are explanatory diagrams of a second modification of the present embodiment. 12A and 12B are explanatory diagrams of a third modification of the present embodiment. The flowchart explaining operation | movement of this embodiment. The flowchart explaining operation | movement of this embodiment. The flowchart explaining operation | movement of this embodiment.

Explanation of symbols

L1 primary coil, L2 secondary coil, TB1, TB2, first and second transistors,
RU1, RU2 pull-up resistor, TD1 output guarantee transistor,
RDW pull-down resistor,
DESCRIPTION OF SYMBOLS 10 Power transmission device, 12 Power transmission part, 14 Voltage detection circuit, 16 Display part,
20 power transmission control device, 22 control circuit (power transmission side), 24 oscillation circuit,
26 Driver control circuit, 28 Waveform detection circuit, 40 Power receiving device, 42 Power receiving unit,
43 rectifier circuit, 46 load modulation unit, 48 power supply control unit, 50 power reception control device,
52 control circuit (power receiving side), 54 output guarantee circuit, 56 position detection circuit,
58 oscillation circuit, 60 frequency detection circuit, 62 full charge detection circuit, 72 voltage detection circuit,
74 connection detection circuit, 90 load, 92 charge control device, 94 battery

Claims (13)

The contactless power transmission system for electromagnetically coupling a primary coil and a secondary coil to transmit power from a power transmitting device to a power receiving device and supplying power from a voltage output node of the power receiving device to a load. A power reception control device provided in the power reception device,
A power receiving side control circuit for controlling the power receiving device;
Output for controlling a first transistor which is provided between a generation node of a power supply voltage generated from an induced voltage of the secondary coil and the voltage output node of the power receiving device and which is turned on when power is transmitted to the load Including warranty circuit,
The output guarantee circuit is:
When connection of an AC adapter that supplies power to the load is detected, the first transistor is set to be turned off, and the power supply voltage is lower than an operation lower limit voltage. 1 is set to turn off the transistor to prevent a backflow of current from the voltage output node to the power supply voltage generation node ;
The first transistor is a P-type transistor in which a voltage of the voltage output node is supplied to the source and the substrate, and a pull-up resistor is connected between the source and the gate.
The output guarantee circuit is:
An output assurance transistor provided between the node of the gate of the first transistor and the low-potential side power supply;
A pull-down resistor provided between a node of the gate of the output assurance transistor and the low-potential side power supply;
The output guarantee circuit is:
A power reception control device , wherein a signal output to the gate of the first transistor is set to a high impedance state to turn off the first transistor . In claim 1,
A voltage detection circuit that activates a voltage detection signal when the power supply voltage is higher than a predetermined voltage;
The output guarantee circuit is:
The power reception control device, wherein the first transistor is set to be turned off at least until the voltage detection signal becomes active. In claim 1 or 2,
The power receiving side control circuit includes:
When ID authentication between the power receiving device and the power transmitting device is completed, an authentication completion signal is activated,
The output guarantee circuit is:
The power reception control device, wherein the first transistor is set to be turned off at least until the authentication completion signal becomes active. In any one of Claims 1 thru | or 3,
A connection detection circuit that activates a connection detection signal when connection of the AC adapter is detected;
The output guarantee circuit is:
The power reception control device, wherein the first transistor is set to be turned off when the connection detection signal is active. The contactless power transmission system for electromagnetically coupling a primary coil and a secondary coil to transmit power from a power transmitting device to a power receiving device and supplying power from a voltage output node of the power receiving device to a load. A power reception control device provided in the power reception device,
A power receiving side control circuit for controlling the power receiving device;
Output for controlling a first transistor which is provided between a generation node of a power supply voltage generated from an induced voltage of the secondary coil and the voltage output node of the power receiving device and which is turned on when power is transmitted to the load Including warranty circuit,
The output guarantee circuit is:
When the power supply voltage is lower than the operation lower limit voltage, the first transistor is set to be turned off, and a backflow of current from the voltage output node to the power supply voltage generation node is prevented .
The first transistor is a P-type transistor in which a voltage of the voltage output node is supplied to the source and the substrate, and a pull-up resistor is connected between the source and the gate.
The output guarantee circuit is:
An output assurance transistor provided between the node of the gate of the first transistor and the low-potential side power supply;
A pull-down resistor provided between a node of the gate of the output assurance transistor and the low-potential side power supply;
The output guarantee circuit is:
A power reception control device , wherein a signal output to the gate of the first transistor is set to a high impedance state to turn off the first transistor . In any one of Claims 1 thru | or 5 ,
A second transistor is provided between the power supply voltage generation node and the first transistor,
The power receiving side control circuit includes:
A power reception control device that performs control to turn on the second transistor during power transmission to the load. In claim 6 ,
The power reception control device, wherein the second transistor is a P-type transistor whose source and substrate are supplied with the voltage of the power supply voltage generation node and whose drain is connected to the drain of the first transistor. . In claim 7 ,
A power reception control device, wherein a second pull-up resistor and a soft start capacitor are provided between a source and a gate of the second transistor. The contactless power transmission system for electromagnetically coupling a primary coil and a secondary coil to transmit power from a power transmitting device to a power receiving device and supplying power from a voltage output node of the power receiving device to a load. A power reception control device provided in the power reception device,
A power receiving side control circuit for controlling the power receiving device;
A connection detection circuit that activates a connection detection signal when connection of an AC adapter that supplies power to the load is detected;
The power receiving side control circuit includes:
When the connection detection signal is active, control is performed to stop power transmission of the power transmission device. In claim 9 ,
The power receiving side control circuit includes:
When the connection detection signal is active, the power reception control device stops power transmission of the power transmission device by not performing ID authentication processing with the power transmission device. In claim 9 or 10 ,
The power receiving side control circuit includes:
When the connection detection signal is active, the power transmission of the power transmission device is stopped by transmitting an AC adapter connection command for notifying that the connection of the AC adapter is detected to the power transmission device. A power reception control device characterized by the above. A power reception control device according to any one of claims 1 to 11 ,
A power receiving unit that converts an induced voltage of the secondary coil into a DC voltage;
A power receiving device including the first transistor and including a power supply control unit that controls power supply to a load. A power receiving device according to claim 12 ,
An electronic apparatus comprising: a load to which power is supplied by the power receiving device.

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