JP2020010428A - USB power supply device and USB power supply method - Google Patents

Abstract

To perform a proper voltage correction corresponding to resistance variations to a user open end.SOLUTION: A USB power supply device comprises a power source circuit, a bus line, an open end for a user, a capacitor, a switch circuit, a detection section, and a regulation section. The bus line connects output of the power source circuit with a receptacle. The open end is wire-connected from the receptacle in any form. The capacitor is provided in the vicinity of the open end and connected with the open end and has a known electrostatic capacity. The switch circuit is provided between an output end of the power source circuit and the receptacle on the bus line. The detection section detects a voltage value charged in the capacitor from the state where electrical charge is discharged, on the basis of an operation of the switch circuit. The regulation section regulates a resistance value for correction of an output voltage of the power source circuit on the basis of a detection result of the detection section.SELECTED DRAWING: Figure 2

Description

  The disclosed embodiments relate to a USB power supply device and a USB power supply method.

  Conventionally, an in-vehicle device mounted on a vehicle, such as a navigation device or a display audio device, has been known. In recent years, most of such in-vehicle devices conform to the USB (Universal Serial Bus) standard, have a USB power supply function, and have a connector (hereinafter, referred to as “Type A connector”) such as an A terminal (a so-called Type A connector) as an open end of power supply to a user. User open end ").

  Note that the USB VBUS power supply is output from the in-vehicle device and then cabled to the user open end. For example, since the arrangement position of the user open end differs for each type of vehicle, the cable wiring length may vary depending on the vehicle. There are many. Depending on the vehicle, a plurality of cables may be relayed by the relay device to the user open end.

  Since such a cable or relay device has a resistance value, the voltage drops due to the load current of the device connected to the user open end. The voltage drop may not satisfy the USB standard.

  As a countermeasure against such a case, for example, for a voltage drop due to cable resistance, a technique of correcting an output voltage according to a load current and holding a predetermined reference voltage has been proposed (for example, see Patent Document 1). .

JP-A-2006-045760

  However, the above-described conventional technology has room for further improvement in performing appropriate voltage correction according to the variation in resistance up to the user open end.

  Specifically, as described above, up to the user open end, the cable wiring length, the number of relay devices, and the like differ depending on the vehicle, so that the resistance to the user open end often varies. However, in the above-described related art, voltage correction is performed according to a constant coefficient, and thus cannot be properly corrected.

  An aspect of the embodiment has been made in view of the above, and provides a USB power supply device and a USB power supply method capable of performing appropriate voltage correction according to variation in resistance to a user open end. Aim.

  The USB power supply device according to one aspect of the embodiment is a USB power supply device based on the USB standard, and includes a power supply circuit, a bus line, an open end for a user, a capacitor, a switch circuit, a detection unit, An adjusting unit. The bus line connects an output of the power supply circuit and a receptacle. The open end is wired from the receptacle in any form. The capacitor is provided near the open end, is connected to the open end, and has a known capacitance. The switch circuit is provided between an output terminal of the power supply circuit on the bus line and the receptacle. The detection unit detects a voltage value charged in the capacitor from a state where electric charge is discharged, based on an operation of the switch circuit. The adjustment unit adjusts a resistance value for correcting an output voltage of the power supply circuit based on a detection result of the detection unit.

  According to an aspect of the embodiment, it is possible to perform appropriate voltage correction according to the variation in resistance up to the user open end.

FIG. 1 is a diagram illustrating a configuration example of a vehicle-mounted device according to a comparative example. FIG. 2 is a diagram illustrating a configuration example of the vehicle-mounted device according to the embodiment. FIG. 3 is a diagram illustrating a modified example of the configuration of the vehicle-mounted device according to the embodiment. FIG. 4 is a flowchart illustrating a processing procedure executed by the in-vehicle device according to the embodiment. FIG. 5 is a flowchart illustrating a modified example of the processing procedure executed by the in-vehicle device according to the embodiment.

  Hereinafter, embodiments of a USB power supply device and a USB power supply method disclosed in the present application will be described in detail with reference to the accompanying drawings. The present invention is not limited by the embodiments described below.

  Hereinafter, a case where the USB power supply device is an in-vehicle device 10 such as a navigation device or a display audio device will be described as an example.

  First, the configuration of an in-vehicle device 10 'as a comparative example of the present embodiment will be described with reference to FIG. FIG. 1 is a diagram illustrating a configuration example of an in-vehicle device 10 ′ according to a comparative example.

  As shown in FIG. 1, the in-vehicle device 10 ′ includes a microcomputer 11, a power supply IC (Integrated Circuit) 12, and a receptacle 20. The microcomputer 11 is a microcontroller, and includes a PWM (Pulse Width Modulation) control unit 11a and an enable control unit 11b.

  The PWM control unit 11a outputs a PWM signal for performing voltage output by PWM control to a voltage correction unit 12a described later. The enable control unit 11b controls the operation permission for the power supply IC 12 by an enable signal.

  The power supply IC 12 includes a voltage correction unit 12a, a switching circuit 12b, and a load current detection unit 12c. A voltage correction adjustment resistor R1 is connected to the voltage correction unit 12a.

  The voltage correction unit 12a performs voltage correction based on the PWM signal from the PWM control unit 11a, the load current detected by the load current detection unit 12c, and the voltage correction adjustment resistor R1. The voltage correction adjustment resistor R1 is individually tuned according to the connection form up to the user open end 32 for each vehicle, and the resistance value is constant.

  The switching circuit 12b includes a switching element, performs switching control on an input from an input power supply using a PWM signal reflecting a correction result of the voltage correction unit 12a, and outputs a voltage.

  The output of the power supply IC 12 and the receptacle 20 are connected by a bus line 100. The bus line 100 is provided with a Zener diode Z1, an inductor I1, an output capacitor C2, and a resistor R2 in this order from the power supply IC 12 side.

  Both ends of the resistor R2 are connected to the load current detector 12c, and the load current detector 12c detects the load current based on the input from the connection line.

  The receptacle 20 is a USB port of the vehicle-mounted device 10 ', and is connected to the user opening unit 30 via a cable. The user opening section 30 is, for example, a USB connector conversion box or a USB conversion cable end.

  The user opening section 30 includes a receptacle 31 and a user opening end 32. Between the receptacle 20 and the user opening section 30, for example, the length of the cable and the number of resistors vary depending on the type of vehicle. Here, only the VBUS line and the GND line are shown. For convenience, only the resistor R3 is shown on the VBUS line, and only the resistor R4 is shown on the GND line.

  In the vehicle-mounted device 10 'having such a configuration, as described above, the voltage correction adjustment resistor R1 is individually tuned according to the connection form, and is a constant coefficient. Accordingly, in the case where the resistance value up to the user open end 32 changes, the resistance value of the voltage correction adjustment resistor R1 may be small and the voltage may be corrected to be lower than the required value, even though the resistance value is large. It can happen. On the other hand, although the resistance value up to the user open end 32 is small, the resistance value of the voltage correction adjustment resistor R1 is large, and the voltage may be corrected so as to exceed a required value.

  Therefore, the USB power supply method according to the present embodiment further includes a switch circuit SW1, a capacitor C1 of a known capacity, a voltage detection unit 11e, and a correction resistance adjustment unit 13 in addition to the configuration of the comparative example described so far. I decided to prepare. The voltage detection unit 11 e is provided in the microcomputer 11 and detects the magnitude of the resistance up to the user open end 32 by the microcomputer 11. The correction resistance adjustment unit 13 switches the resistance value for correcting the output voltage of the power supply IC 12 according to the detected value.

  This will be specifically described with reference to FIG. FIG. 2 is a diagram illustrating a configuration example of the vehicle-mounted device 10 according to the present embodiment. Note that FIG. 2 corresponds to FIG. 1, and thus the description using FIG. 2 will mainly focus on differences from FIG. 1.

  As shown in FIG. 2, the in-vehicle device 10 according to the present embodiment is different from the example of FIG. 1 in that a switch circuit SW1 is further provided between the resistor R2 of the bus line 100 and the receptacle 20. Further, the in-vehicle device 10 is different from the example of FIG.

  The in-vehicle device 10 is different from the example in FIG. 1 in that the microcomputer 11 further includes a resistance adjustment control unit 11c, a pulse control unit 11d, and a voltage detection unit 11e. 1 in that the voltage correction unit 12a is connected to the correction resistance adjustment unit 13 instead of the voltage correction adjustment resistance R1.

  Further, the in-vehicle device 10 is different from the example of FIG. 1 in further including a voltage dividing circuit 14 and a temperature sensor 15.

  First, the switch circuit SW1 is turned on / off by a pulse signal output from the pulse control unit 11d. The capacitor C1 is provided, for example, between the receptacle 31 and the user open end 32.

  The resistance adjustment control unit 11c of the microcomputer 11 performs control to cause the correction resistance adjustment unit 13 to switch the constant of the voltage correction resistance according to the detection value of the voltage detection unit 11e. The pulse control unit 11d controls on / off of the switch circuit SW1 by a pulse signal.

  The pulse control unit 11d can reduce an error due to temperature variation by changing the ON control time of the switch circuit SW1 according to each temperature based on the detection value of the temperature sensor 15.

  The voltage detection unit 11e is connected to the detection line 200 branched from between the switch circuit SW1 of the bus line 100 and the receptacle 20, and detects a voltage by A / D conversion.

  In addition, the voltage detection unit 11e can reduce errors due to temperature variations by changing the threshold value of the detection voltage according to each temperature based on the detection value of the temperature sensor 15.

  The correction resistance adjustment unit 13 switches the constant of the voltage correction resistance based on the control of the resistance adjustment control unit 11c. The voltage dividing circuit 14 is provided for level conversion between the VBUS voltage and the microcomputer input. The temperature sensor 15 detects a temperature and outputs a detected value to the microcomputer 11.

  The vehicle-mounted device 10 configured as described above performs voltage correction in the following procedure, for example, at a timing before shipment as a product or at the time of replacement. First, in a state where no device is connected to the user open end 32, the switch circuit SW1 is turned off under the control of the pulse control unit 11d.

  Then, it waits for a certain time until the electric charge at the user open end 32 is discharged by the voltage dividing circuit 14. After that, the voltage detector 11e confirms that the voltage has dropped to a certain voltage (for example, near 0 V).

  After the discharge of the user open end 32, the switch circuit SW1 is turned on under the control of the pulse control unit 11d. When the switch circuit SW1 is turned on, the capacitor C1 is charged. The electric charge charged to the capacitor C1 while the switch circuit SW1 is on is determined by the time constant of the resistance value up to the user open end 32 and the capacitance of the capacitor C1, and based on this, the switch circuit SW1 is turned on. Is a time during which the capacitor C1 is not fully charged.

  Then, under the control of the pulse control unit 11d, the switch circuit SW1 is turned off from on. After being turned off, the voltage is detected by the voltage detector 11e. Here, if the detected voltage level is large, it can be determined that the resistance value up to the user open end 32 is small. If the level of the detected voltage is low, it can be determined that the resistance value up to the user open end 32 is high.

  The resistance adjustment control unit 11c determines such a magnitude based on, for example, a threshold according to the detected voltage level, and causes the correction resistance adjustment unit 13 to switch the constant of the voltage correction resistance according to the determination result.

  This makes it possible to perform appropriate voltage correction according to the variation in resistance up to the user open end 32.

  In the configuration example shown in FIG. 2, the case where the capacitor C1 is provided, for example, between the receptacle 31 of the user opening section 30 and the user opening end 32 has been described. A measuring jig provided with C1 may be connected from the outside.

  FIG. 3 is a diagram illustrating a modified example of the configuration of the vehicle-mounted device 10 according to the embodiment. That is, as shown in FIG. 3, the capacitor C1 is not provided between the receptacle 31 and the user open end 32, but is provided, for example, on the measuring jig 40, and the measuring jig 40 is externally connected to the user open end. 32, the above-described procedure of voltage correction may be executed.

  In this case, since a general-purpose product can be used for the user opening section 30, the operator can easily carry out the switching operation of the voltage correction resistance if the measurement jig 40 is carried. In addition, for example, a USB device such as a USB memory can be used as the measurement jig 40 if it has a known capacitance and ensures that products of the same type are always used.

  Next, a processing procedure executed by the vehicle-mounted device 10 according to the present embodiment will be described. FIG. 4 is a flowchart illustrating a processing procedure executed by the vehicle-mounted device 10 according to the present embodiment.

  As shown in FIG. 4, first, in a configuration example shown in FIG. 2, in a state where no device is connected to the user open end 32, or in a modification shown in FIG. In the connected state, the pulse control unit 11d turns off the switch circuit SW1 (Step S101).

  Then, the microcomputer 11 waits for the discharge of the user open end 32 (step S102). Then, it is determined whether the VBUS voltage has dropped below a predetermined voltage Vstart (step S103). Voltage Vstart is, for example, near 0V.

  Here, if the VBUS voltage is lower than the voltage Vstart (step S103, Yes), the pulse control unit 11d turns on the switch circuit SW1 (step S104). If not (step S103, No), the processing from step S102 is repeated.

  Subsequently, the charge waiting of the capacitor C1 is performed (step S105). Here, the charge waiting time is a time during which the capacitor C1 is not fully charged.

  After the pulse control unit 11d turns off the switch circuit SW1 (step S106), the microcomputer 11 waits for stabilization of the detection voltage of the voltage detection unit 11e (step S107). This waits until the A / D terminal voltage is stabilized, taking into account the time constant of the A / D conversion circuit of the voltage detection unit 11e.

  Then, the voltage detector 11e detects the voltage (Vad) (Step S108). Although not shown, the A / D conversion values may be obtained an arbitrary number of times, and the average value may be used as Vad.

  Then, Vad is determined using the respective voltage thresholds V1, V2, V3 (step S109), and the correction resistors Ra, Rb, Rc, Rd are switched according to the determination result (steps S110 to S113). Here, it is assumed that V1 <V2 <V3, but the magnitudes of the correction resistors Ra, Rb, Rc, and Rd are not determined by the magnitudes of V1 to V3. It is assumed that V1 to V3 merely determine the correction resistors Ra, Rb, Rc, and Rd to be switched.

  If Vad <V1, the correction resistance adjustment unit 13 switches the correction resistance to, for example, the correction resistance Ra (Step S110). If V1 ≦ Vad <V2, the correction resistance adjustment unit 13 switches the correction resistance to, for example, the correction resistance Rb (step S111).

  If V2 ≦ Vad <V3, the correction resistance adjustment unit 13 switches the correction resistance to, for example, the correction resistance Rc (step S112). If V3 ≦ Vad, the correction resistance adjustment unit 13 switches the correction resistance to, for example, the correction resistance Rd (step S113). Then, the process ends.

  As the Vad determination threshold such as V1, V2, and V3, for example, an average value, a minimum value, and a maximum value of A / D conversion values obtained by executing steps S101 to S108 a plurality of times may be used. .

  By performing such a processing procedure, it is possible to perform appropriate voltage correction according to the variation in resistance up to the user open end 32.

  As shown in FIG. 4, the processing procedure of steps S101 to S107 is common to the modified example described below, and may be hereinafter referred to as “common processing”.

  Next, a modified example of the processing procedure executed by the vehicle-mounted device 10 according to the present embodiment will be described. FIG. 5 is a flowchart illustrating a modification of the processing procedure executed by the vehicle-mounted device 10 according to the present embodiment.

  As shown in FIG. 5, first, common processing is executed (step S201). Then, the voltage detector 11e detects the voltage (Vad) (Step S202).

  Then, Vad is determined using a predetermined voltage threshold Vth (step S203). If Vad <Vth (step S203, Yes), the process proceeds to step S205. Otherwise (step S203, No), a retry wait is performed for a predetermined time (step S204), and the processing from step S202 is repeated.

  Here, the predetermined time for retry waiting is, for example, a value equal to or longer than the A / D sampling period. Also, each time a retry is performed, the number of retries is counted up.

  Subsequently, in step S205, the number of retries (N) is determined. A large value of N indicates that the time until Vad <Vth is long, that is, the resistance to the user open end 32 is small. Therefore, the resistance to the user open end 32 decreases as the value of N increases.

  Conversely, a small value of N indicates that the time until Vad <Vth is short, that is, the resistance up to the user open end 32 is large. Therefore, the smaller the value of N, the greater the resistance up to the user open end 32.

  In accordance with this concept, the correction resistors Ra, Rb, Rc, and Rd are switched according to the determination result of step S205 (steps S206 to S209). Here, it is assumed that a <b <c.

  If c ≦ N, the correction resistance adjustment unit 13 switches the correction resistance to, for example, the correction resistance Ra (Step S206). If b ≦ N <c, the correction resistance adjustment unit 13 switches the correction resistance to the correction resistance Rb (Step S207).

  If a ≦ N <b, the correction resistance adjustment unit 13 switches the correction resistance to, for example, the correction resistance Rc (step S208). If N <a, the correction resistance adjustment unit 13 switches the correction resistance to, for example, the correction resistance Rd (step S209). Then, the process ends.

  According to the processing procedure of such a modified example, it is also possible to perform appropriate voltage correction according to the variation in resistance up to the user open end 32.

  In the processing procedures shown in FIGS. 4 and 5, for convenience of explanation, the case where the switchable correction resistors are four types of the correction resistors Ra, Rb, Rc, and Rd is described as an example. It does not limit the number of possible types.

  As described above, the vehicle-mounted device 10 (corresponding to an example of “USB power supply device”) according to the present embodiment includes the power supply IC 12 (corresponding to an example of “power supply circuit”), the bus line 100, and the user open end 32. (Corresponding to an example of “open end for user”), capacitor C1, switch circuit SW1, voltage detector 11e (corresponding to an example of “detector”), and correction resistance adjuster 13 (“adjuster”). ).

  The bus line 100 connects the output of the power supply IC 12 and the receptacle 20. The user open end 32 is connected by wire from the receptacle 20 in any form. The capacitor C1 is provided near the user open end 32, is connected to the user open end 32, and has a known capacitance. The switch circuit SW1 is provided between the output terminal of the power supply IC 12 on the bus line 100 and the receptacle 20. The voltage detection unit 11e detects a voltage value charged in the capacitor C1 from a state in which electric charges are discharged, based on an operation of the switch circuit SW1. The correction resistance adjustment unit 13 adjusts a resistance value for correcting the output voltage of the power supply IC 12 based on the detection result of the voltage detection unit 11e.

  Therefore, according to the in-vehicle device 10 according to the present embodiment, it is possible to perform appropriate voltage correction according to the variation in resistance up to the user open end 32.

  Further, the in-vehicle device 10 according to the present embodiment includes a pulse control unit 11d (corresponding to an example of a “control unit”) that controls the switch circuit SW1. The pulse control unit 11d turns off the switch circuit SW1 and discharges the charge of the capacitor C1, and thereafter, the capacitor C1 calculated based on the time constant between the resistance value up to the user open end 32 and the above-mentioned capacitance becomes full. During an elapsed time during which charging is not performed, the switch circuit SW1 is turned on.

  Therefore, according to the vehicle-mounted device 10 according to the present embodiment, it is possible to prevent the capacitor C1 from being fully charged and the voltage detecting unit 11e from being unable to detect an appropriate voltage value.

  The voltage detector 11e is connected to the detection line 200 branched from the bus line 100 between the switch circuit SW1 and the receptacle 20 on the bus line 100, and acquires the voltage value while performing digital conversion. The pulse control unit 11d turns off the switch circuit SW1 after the lapse of the elapsed time, and the voltage detection unit 11e acquires the voltage value after a lapse of a predetermined time after the switch circuit SW1 is turned off.

  Therefore, according to the in-vehicle device 10 according to the present embodiment, since the voltage value is acquired after the detection voltage of the voltage detection unit 11e is stabilized, accurate detection can be performed.

  Further, the capacitor C1 is provided between the receptacle 20 and the user open end 32 in the vicinity of the user open end 32, and the pulse control unit 11d is connected to the user open end 32 in a state where no device is externally connected. The switch circuit SW1 is controlled so as to start discharging and charging the capacitor C1.

  Therefore, according to the in-vehicle device 10 according to the present embodiment, the magnitude of the resistance up to the user open end 32 can be accurately measured.

  The capacitor C1 is provided inside a measurement jig 40 (corresponding to an example of a “jig”) provided to be connectable to the user open end 32 from the outside. On the other hand, the switch circuit SW1 is controlled so as to start discharging and charging the capacitor C1 while the measuring jig 40 is connected from the outside.

  Therefore, according to the in-vehicle device 10 according to the present embodiment, the magnitude of the resistance up to the user open end 32 can be accurately measured. Further, the magnitude of the resistance from the user open end 32 to the user open end 32 can be easily measured simply by connecting the measuring jig 40 regardless of the inner structure.

  In the above-described embodiment, the in-vehicle device 10 is an example of a USB power supply device. However, any device that conforms to the USB standard and has a function of supplying VBUS power may be used in a vehicle. Instead, the present embodiment can be applied.

  Further effects and modifications can be easily derived by those skilled in the art. Thus, the broader aspects of the present invention are not limited to the specific details and representative embodiments shown and described above. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and equivalents thereof.

Reference Signs List 10 in-vehicle device 11 microcomputer 11d pulse control unit 11e voltage detection unit 12 power supply IC
13 Correction resistance adjustment unit 20 Receptacle 32 User open end 40 Measurement jig 100 Bus line 200 Detection line C1 Capacitor SW1 Switch circuit

Claims (6)

A USB power supply device conforming to the USB (Universal Serial Bus) standard,
Power supply circuit,
A bus line connecting an output of the power supply circuit and a receptacle,
An open end for a user wired in any form from the receptacle,
A capacitor provided near the open end and having a known capacitance connected to the open end;
A switch circuit provided between the output terminal of the power supply circuit and the receptacle on the bus line,
Based on the operation of the switch circuit, a detection unit that detects a voltage value charged to the capacitor from a state where electric charge has been discharged,
An adjustment unit that adjusts a resistance value for correcting the output voltage of the power supply circuit based on a detection result of the detection unit. A control unit for controlling the switch circuit,
The control unit includes:
After the charge of the capacitor is discharged by turning off the switch circuit, during the elapsed time during which the capacitor is not fully charged, calculated based on the time constant of the resistance value and the capacitance up to the open end, The USB power supply device according to claim 1, wherein the switch circuit is turned on. The detection unit,
It is connected to a detection line branched from the bus line between the switch circuit and the receptacle on the bus line, and acquires the voltage value while performing digital conversion,
The control unit includes:
After the lapse of the elapsed time, the switch circuit is turned off,
The detection unit,
The USB power supply device according to claim 2, wherein the voltage value is acquired after a predetermined time has elapsed since the switch circuit was turned off. The capacitor is
Provided near the open end between the receptacle and the open end,
The control unit includes:
4. The USB power supply device according to claim 2, wherein the switch circuit is controlled so as to start discharging and charging the capacitor in a state where no device is externally connected to the open end. 5. . The capacitor is
It is provided inside a jig provided so as to be connectable to the open end from outside,
The control unit includes:
4. The USB according to claim 2, wherein the switch circuit is controlled so as to start discharging and charging of the capacitor in a state where the jig is externally connected to the open end. 5. Power supply. A power supply circuit, a bus line connecting an output of the power supply circuit to a receptacle, an open end for a user wired from the receptacle in an arbitrary form, and A capacitor having a known capacitance connected near the open end and connected to the open end; and a switch circuit provided between the output end of the power supply circuit and the receptacle on the bus line. A USB power supply method using a USB power supply device,
Based on the operation of the switch circuit, a detection step of detecting a voltage charged in the capacitor from a state where electric charge has been discharged,
Adjusting the resistance value for correcting the output voltage of the power supply circuit based on the detection result of the voltage.

Images