USB PORT CONTROLLER AND ELECTRONIC APPARATUS

Abstract

Disclosed herein is a USB port controller on a sink side. The USB port controller is compatible with a USB Type-C. A sink equipped with the USB port controller includes a power supply terminal, a capacitor connected to the power supply terminal, and a discharge resistance and a discharge switch connected in series with each other between the power supply terminal and a ground line. The USB port controller includes a discharge control unit configured to turn on the discharge switch when no voltage is supplied from a source to the power supply terminal.

Claims

1. A universal serial bus port controller on a sink side, the universal serial bus port controller being compatible with a universal serial bus Type-C, a sink equipped with the universal serial bus port controller including a power supply terminal, a capacitor connected to the power supply terminal, and a discharge resistance and a discharge switch connected in series with each other between the power supply terminal and a ground line, the universal serial bus port controller comprising: a discharge control unit configured to turn on the discharge switch when no voltage is supplied from a source to the power supply terminal.

2. The universal serial bus port controller according to claim 1, wherein the discharge switch is included in the universal serial bus port controller.

3. The universal serial bus port controller according to claim 1, wherein the discharge resistance is included in the universal serial bus port controller.

4. The universal serial bus port controller according to claim 1, wherein the discharge switch is a depletion transistor, and the discharge control unit applies an off-level driving voltage to a control terminal of the discharge switch when a voltage is supplied from the source to the power supply terminal.

5. The universal serial bus port controller according to claim 1, wherein the universal serial bus port controller is integrated on one semiconductor substrate.

6. An electronic apparatus comprising: the universal serial bus port controller according to claim 1.

7. An electronic apparatus comprising: a universal serial bus receptacle including a power supply terminal and a grounding terminal; an internal circuit; a capacitor connected between the power supply terminal and a ground line; an input switch connected between the power supply terminal and the internal circuit; a discharge resistance and a discharge switch connected in series with each other between the power supply terminal and the ground line; and a discharge control unit configured to turn on the discharge switch when no voltage is supplied from a source to the power supply terminal.

8. The electronic apparatus according to claim 7, wherein the discharge switch is a depletion transistor, and the discharge control unit applies an off-level driving voltage to a control terminal of the discharge switch when a voltage is supplied from the source to the power supply terminal.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] FIG. 1 is a block diagram of a feeding system;

[0034] FIG. 2 is an operation sequence diagram of the feeding system of FIG. 1;

[0035] FIG. 3 is a diagram of assistance in explaining reconnection between a source and a sink;

[0036] FIG. 4 is a block diagram of a feeding system according to an embodiment;

[0037] FIG. 5 is a diagram of assistance in explaining operation performed at a time of reconnection between a feeding device and a power receiving device in the feeding system of FIG. 4;

[0038] FIG. 6 is a circuit diagram illustrating an example of a configuration of a discharge switch and a discharge control unit;

[0039] FIG. 7 is a circuit diagram illustrating a modification of the discharge switch and the discharge control unit;

[0040] FIG. 8 is a circuit diagram illustrating a modification of the discharge switch and the discharge control unit; and

[0041] FIG. 9 is a circuit diagram illustrating another configuration example of the discharge switch and the discharge control unit.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Outline of Embodiments

[0042] An outline of a few illustrative embodiments of the present disclosure will be described. This outline describes, in a simplified manner, a few concepts of one or a plurality of embodiments as an introduction to the following detailed description for a purpose of basic understanding of the embodiments, and does not limit the scope of the technology or the disclosure. This outline is neither a comprehensive outline of all conceivable embodiments nor intended to identify important elements of all of the embodiments or demarcate the scope of a part or all of embodiments. For convenience, “one embodiment” may be used to refer to one embodiment (an example or a modification) or a plurality of embodiments (examples or modifications) disclosed in the present specification.

[0043] A USB port controller according to one embodiment is compatible with a USB Type-C. A sink equipped with the USB port controller includes a power supply terminal, a capacitor connected to the power supply terminal, and a discharge resistance and a discharge switch connected in series with each other between the power supply terminal and a ground line. The USB port controller includes a discharge control unit configured to turn on the discharge switch when no voltage is supplied from a source to the power supply terminal.

[0044] When the discharge switch provided to the sink is turned on while the source is not connected to the sink, the charge of the capacitor is discharged, and the voltage of the power supply terminal is decreased. Hence, when the source is connected to the sink next time, the remaining charge of the capacitor is zero or very small, so that a rise in the voltage of the power supply terminal of the source is suppressed. Thus, at a time of reconnection, the voltage of the power supply terminal of the source is lower than a threshold voltage. A bus switch (output switch) of the source is therefore immediately turned on, so that feeding can be started in a short time.

[0045] In one embodiment, the discharge switch may be included in the USB port controller.

[0046] In one embodiment, the discharge resistance may be included in the USB port controller.

[0047] In one embodiment, the discharge switch may be a depletion transistor. The discharge control unit may apply an off-level driving voltage to a control terminal of the discharge switch when a voltage is supplied from the source to the power supply terminal.

[0048] In one embodiment, the USB port controller may be integrated on one semiconductor substrate. “integrated” includes a case where all of circuit constituent elements are formed on the semiconductor substrate and a case where main circuit constituent elements are integrated. A part of resistances, capacitors, etc., may be provided on the outside of the semiconductor substrate, for adjustment of circuit constants. Integrating the circuit on one chip can reduce a circuit area and hold characteristics of the circuit elements uniform.

[0049] An electronic apparatus according to one embodiment includes a USB receptacle including a power supply terminal and a grounding terminal, an internal circuit, a capacitor connected between the power supply terminal and a ground line, an input switch connected between the power supply terminal and the internal circuit, a discharge resistance and a discharge switch connected in series with each other between the power supply terminal and the ground line, and a discharge control unit configured to turn on the discharge switch when no voltage is supplied from a source to the power supply terminal.

[0050] In one embodiment, the discharge switch may be a depletion transistor, and the discharge control unit may apply an off-level driving voltage to a control terminal of the discharge switch when a voltage is supplied from the source to the power supply terminal.

Embodiment

[0051] A preferred embodiment will hereinafter be described with reference to the drawings. Identical or equivalent constituent elements, members, and processing illustrated in each drawing are identified by the same reference numerals, and repeated description thereof will be omitted as appropriate. In addition, the embodiment is not restrictive of the disclosure and the technology but is illustrative, and all features described in the embodiment and combinations thereof are not necessarily essential to the disclosure and the technology.

[0052] In the present specification, a “state in which a member A is connected to a member B” includes not only a case where the member A and the member B are physically directly connected to each other but also a case where the member A and the member B are indirectly connected to each other via another member that does not essentially affect a state of electric connection between the member A and the member B or does not impair functions or effects produced by the coupling of the member A and the member B.

[0053] Similarly, a “state in which a member C is connected (provided) between the member A and the member B” includes not only a case where the member A and the member C or the member B and the member C are directly connected to each other but also a case where the member A and the member C or the member B and the member C are indirectly connected to each other via another member that does not essentially affect a state of electric connection between the member A and the member C or the member B and the member C or does not impair functions or effects produced by the coupling of the member A and the member C or the member B and the member C.

[0054] FIG. 4 is a block diagram of a feeding system 100 according to an embodiment. The feeding system 100 is compliant with a USB Type-C standard. The feeding system 100 includes a feeding device (referred to also as a source) 200 and a power receiving device (referred to also as a sink) 300. The feeding device 200 and the power receiving device 300 are connected to each other via a USB cable 106.

[0055] The feeding device 200 is, for example, included in an electronic apparatus 102. The electronic apparatus 102 may be an AC adapter. The power receiving device 300 is included in a battery driven type electronic apparatus 400 such as a smart phone, a tablet terminal, a digital camera, a digital video camera, or a portable audio player.

[0056] A configuration of the source side, that is, the electronic apparatus 102 side will first be described.

[0057] The electronic apparatus 102 includes the feeding device 200 and a receptacle 108. The feeding device 200 includes a power supply circuit 202, a feeding side PD controller (hereinafter referred to as a feeding side controller) 204, a bus switch SW11, and capacitors C11 and C12. The USB cable 106 is detachably connected to the receptacle 108 of the electronic apparatus 400. Incidentally, there is also a charge adapter in which the receptacle 108 is omitted and the USB cable 106 is integral with the electronic apparatus 102.

[0058] The receptacle 108 includes a VBUS terminal for supplying a bus voltage V.sub.BUS, a GND terminal for supplying a ground voltage V.sub.GND (0 V), and CC ports.

[0059] The power supply circuit 202 generates the bus voltage V.sub.BUS. The power supply circuit 202 may include an AC/DC converter that receives AC 100 V from an external power supply (for example, a commercial alternating-current power supply) not illustrated and converts AC 100 V into a direct-current bus voltage V.sub.BUS. The bus voltage V.sub.BUS generated by the power supply circuit 202 is supplied to the power receiving device 300 via a bus line of the USB cable 106 and the bus switch SW11.

[0060] The feeding side controller 204 is a port controller for a USB Type-C and a USB-PD. The feeding side controller 204 and a USB port controller 500 are connected to each other via CC lines. The feeding side controller 204 can detect that the power receiving device 300 is connected to the feeding device 200, on the basis of the state of CC pins on the USB port controller 500 side. In addition, the feeding side controller 204 and the USB port controller 500 can communicate with each other via the CC lines. The feeding side controller 204 and the USB port controller 500 negotiate the voltage level of the bus voltage V.sub.BUS to be supplied by the feeding device 200. The feeding side controller 204 controls the power supply circuit 202 so as to provide the determined voltage level, and performs on-off control of the bus switch SW11.

[0061] In the USB Type-C standard, after the feeding side controller 204 detects the connection of the power receiving device 300 to the feeding device 200, the feeding side controller 204 turns on the bus switch SW11 on condition that the bus voltage V.sub.BUS_SRC of the VBUS terminal is lower than a predetermined threshold value vSafe0V.

[0062] A configuration of the sink side, that is, the electronic apparatus 400 will next be described.

[0063] The electronic apparatus 400 includes a battery 402, a receptacle 404, a load (system) circuit 406, and the power receiving device 300. The battery 402 is a rechargeable secondary battery. The load circuit 406 includes a CPU, a memory, a liquid crystal display, an audio circuit, etc. The electronic apparatus 102 is detachably connected to the receptacle 404 via the USB cable 106.

[0064] The power receiving device 300 receives power from the electronic apparatus 102, and charges a charging circuit 410. The power receiving device 300 includes the charging circuit 410, the USB port controller 500, a bus switch SW21, capacitors C21 and C22, a discharge resistance R21, and a discharge switch SW22.

[0065] The charging circuit 410 receives the bus voltage V.sub.BUS from the feeding device 200 via the USB cable 106 and the bus switch SW21, and charges the battery 402. On the power receiving device 300 side, the bus voltage V.sub.BUS will be referred to also as an input voltage, and described as V.sub.BUS_SNK. The charging circuit 410 is constituted by a step-down DC/DC converter, a linear regulator, or a combination thereof.

[0066] A system voltage V.sub.SYS corresponding to at least one of the bus voltage V.sub.BUS_SNK and a voltage V.sub.BAT of the battery 402 is supplied from the charging circuit 410 to the load circuit 406. The load circuit 406 includes a multi-channel power supply including a power management IC, a DC/DC converter, a linear regulator, etc., a microcomputer, a liquid crystal display, a display driver, etc.

[0067] The capacitors C21 and C22 are connected to both ends of the bus switch SW21. In addition, the discharge resistance R21 and the discharge switch SW22 are connected between the VBUS terminal of the receptacle 404 and the ground line and in parallel with the capacitor C21.

[0068] The USB port controller 500 includes a CC pin circuit 510, a discharge control unit 520, and a processor 530. The CC pin circuit 510 includes a pull-down resistance that pulls down the CC pins. Incidentally, in a case where the power receiving device 300 has a dual power role (DPR) that allows switching between the sink and the source, the CC pin circuit 510 is configured to be switchable between a state in which the CC pins are pulled down (that is, the sink) and a state in which the CC pins are pulled up (that is, the source).

[0069] As described above, the USB port controller 500 performs negotiation with the feeding side controller 204 via the CC lines. A transceiver for communication via the CC lines is included in the CC pin circuit 510.

[0070] Data (PDO) that defines the bus voltage V.sub.BUS requested by the power receiving device 300 and a maximum current is defined in the USB port controller 500. When the electronic apparatus 102 and the electronic apparatus 400 are connected to each other, the feeding side controller 204 and the USB port controller 500 perform negotiation, and determine the voltage level of the bus voltage V.sub.BUS on the basis of the PDO. In addition, the USB port controller 500 performs on-off control of the bus switch SW21. The processor 530 executes a software program, and thereby performs negotiation with the feeding side controller 204. The processor 530 may be a microcontroller independent of the USB port controller 500.

[0071] The discharge control unit 520 monitors the voltage V.sub.BUS_SNK of the VBUS terminal of the receptacle 404. The discharge control unit 520 is configured to turn on the discharge switch SW22 when the bus voltage V.sub.BUS is not supplied from the electronic apparatus 102 to the VBUS terminal. The discharge control unit 520 turns off the discharge switch SW22 when detecting that the bus voltage V.sub.BUS is supplied from the electronic apparatus 102 to the VBUS terminal.

[0072] A configuration of the feeding system 100 has been described above. Operation thereof will next be described.

[0073] FIG. 5 is a diagram of assistance in explaining operation performed at a time of reconnection between the feeding device 200 and the power receiving device 300 in the feeding system 100 of FIG. 4.

[0074] Before time t.sub.0, the power receiving device 300 and the feeding device 200 are connected to each other by the USB cable 106, and a bus voltage V.sub.BUS of 5 V is supplied from the feeding device 200 to the power receiving device 300.

[0075] In this state, the VBUS terminal of the receptacle 404 is supplied with the bus voltage V.sub.BUS of 5 V, and therefore the discharge control unit 520 holds the discharge switch SW22 off.

[0076] When the USB cable 106 is disconnected at time to, the bus switch SW11 of the feeding device 200 is turned off, a discharge path not illustrated conducts, the capacitor C12 is discharged, and the voltage V.sub.BUS_SRC decreases toward 0 V. The USB port controller 500 turns off the bus switch SW21.

[0077] When the USB cable 106 is disconnected, the voltage V.sub.BUS_SNK on the power receiving device 300 side decreases. When the discharge control unit 520 detects the decrease in the voltage V.sub.BUS_SNK at time t.sub.1, the discharge control unit 520 determines that the feeding of the bus voltage V.sub.BUS is stopped, and turns on the discharge switch SW22. Consequently, the capacitor C21 is discharged, and the voltage V.sub.BUS_SNK rapidly decreases to 0 V.

[0078] At time t.sub.2, the feeding device 200 and the power receiving device 300 are connected to each other by the USB cable 106 again. The feeding side controller 204 of the feeding device 200 detects that the power receiving device 300 is connected to the feeding device 200, on the basis of the state of the CC ports.

[0079] At time t.sub.2, the charge of the capacitor C21 of the power receiving device 300 is zero. Hence, even when the feeding device 200 and the power receiving device 300 are connected to each other, the voltage V.sub.BUS_SRC does not rise, and the voltage V.sub.BUS_SRC maintains a state of being lower than the threshold voltage vSafe0V.

[0080] At time t.sub.3, when the feeding side controller 204 detects that the voltage V.sub.BUS_SRC is lower than the threshold value vSafe0V, the feeding side controller 204 turns on the bus switch SW11. Consequently, the voltages V.sub.BUS_SRC and V.sub.BUS_SNK rise.

[0081] In the power receiving device 300, when the discharge control unit 520 detects that the bus voltage V.sub.BUS_SNK is supplied, the discharge control unit 520 turns off the discharge switch SW22. Consequently, a discharge path including the discharge resistance R21 and the discharge switch SW22 is interrupted.

[0082] Operation of the feeding system 100 has been described above.

[0083] According to this feeding system 100, when the feeding device 200 is not connected to the power receiving device 300, the discharge switch SW22 provided to the power receiving device 300 is turned on. Consequently, the charge of the capacitor C21 is discharged, and the voltage V.sub.BUS_SNK of the VBUS terminal is decreased. Hence, when the feeding device 200 is connected to the power receiving device 300 next time, the remaining charge of the capacitor C21 is zero or very small, so that a rise in the voltage V.sub.BUS_SRC of the VBUS terminal of the feeding device 200 can be suppressed. Thus, at a time of reconnection, the voltage V.sub.BUS_SRC is lower than the threshold voltage vSafe0V, so that the bus switch SW11 of the feeding device 200 is immediately turned on, and feeding can be started in a short time.

[0084] When the bus voltage V.sub.BUS is supplied from the feeding device 200 to the power receiving device 300, the discharge switch SW22 is off, and therefore unnecessary power consumption in the discharge path can be prevented.

[0085] FIG. 6 is a circuit diagram illustrating an example of a configuration of the discharge switch SW22 and the discharge control unit 520. The discharge control unit 520 needs to be on in a state in which the power supply voltage V.sub.BUS is not supplied to the USB port controller 500. The discharge switch SW22 includes a transistor M21. The transistor M21 is a depletion N-channel metal oxide semiconductor field effect transistor (MOSFET).

[0086] The discharge control unit 520 includes a driver 522. The driver 522 is inoperable and outputs 0 V when the power supply voltage V.sub.BUS is not supplied. The depletion MOSFET is a normally on device. The depletion MOSFET is set in an on state by a gate voltage of 0 V.

[0087] The driver 522 becomes operable when the power supply voltage V.sub.BUS is supplied. The driver 522 can select and output a negative driving voltage V.sub.NEG in an operable state. The driver 522 may include a negative charge pump. The discharge switch SW22 can be turned off by application of the negative voltage V.sub.NEG to the gate of the depletion MOSFET discharge switch SW22.

[0088] The driver 522 may be configured to output the negative voltage V.sub.NEG at all times in the operable state in which the power supply voltage V.sub.BUS is supplied. Alternatively, the driver 522 may be configured to be able to control the output between 0 V and the negative voltage V.sub.NEG in the operable state. In addition, the positions of the discharge switch SW22 and the discharge resistance R21 may be interchanged.

[0089] FIG. 7 is a circuit diagram illustrating a modification of the discharge switch SW22 and the discharge control unit 520. In this modification, the transistor M21 as the discharge switch SW22 is integrated in the USB port controller 500. The USB port controller 500 has a discharge pin DISCHG. The transistor M21 is connected between the discharge pin DISCHG and the ground line. The discharge resistance R21 is connected between the discharge pin DISCHG of the USB port controller 500 and the VBUS terminal. According to this modification, the number of external parts can be reduced.

[0090] FIG. 8 is a circuit diagram illustrating a modification of the discharge switch SW22 and the discharge control unit 520. In this modification, in addition to the transistor M21, the discharge resistance R21 is integrated in the USB port controller 500. The USB port controller 500 has a discharge pin DISCHG. The transistor M21 and the discharge resistance R21 are connected between the discharge pin DISCHG and the ground line. The transistor M21 and the discharge resistance R21 may be interchanged. The discharge pin DISCHG of the USB port controller 500 is directly connected to the VBUS terminal. According to this modification, the number of external parts can be further reduced.

[0091] FIG. 9 is a circuit diagram illustrating another configuration example of the discharge switch SW22 and the discharge control unit 520. The discharge switch SW22 includes a transistor M22. The transistor M22 is a depletion P-channel MOSFET.

[0092] The discharge control unit 520 includes a pull-up resistance R22 connected between the gate and the source of the transistor M22 and a driver 524 that controls the gate of the transistor M22. The output of the driver 524 has a high impedance in an inoperable state in which the power supply voltage V.sub.BUS is not supplied. At this time, the gate and the source of the transistor M22 are short-circuited by the pull-up resistance R22. Thus, a gate-to-source voltage is 0 V, and the discharge switch SW22 is on.

[0093] The driver 524 outputs a voltage higher than the voltage V.sub.BUS in an operable state in which the power supply voltage V.sub.BUS is supplied. The transistor M22 is thereby turned off.

[0094] In the case of FIG. 9, at least one of the transistor M22, the discharge resistance R21, and the pull-up resistance R22 may be integrated in the USB port controller 500.

[0095] The embodiments are illustrative, and it is to be understood by those skilled in the art that there are various modifications of combinations of constituent elements and processing processes of those embodiments and that such modifications are also included in the scope of the present disclosure or the present technology.