JP2013038989A - Power supply control circuit, electronic apparatus, and noise-canceling headphone - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent restart of energization of a load circuit when an input voltage temporarily rises after the energization is cut off, even with a switch maintained in an on state.SOLUTION: The power supply control circuit includes: a detection section that is connected with a power supply and monitors an input voltage from the power supply; a voltage conversion circuit that has an enable terminal and converts the input voltage from the power supply into a desired voltage to supply electric power to at least the detection section; a first switching element that is connected between the power supply and the enable terminal; and a control section that switches the first switching element from on to off operations by an input from the detection section.

Description

  The present disclosure relates to a power supply control circuit, an electronic device, and a noise canceling headphone. In particular, the present disclosure relates to a power supply control circuit, an electronic device, and a noise canceller that prevent resumption of energization when the input voltage temporarily rises after the energization is interrupted even when the switch remains on. Regarding ring headphones.

  In recent years, portable electronic devices have become widespread. For example, a user can enjoy various contents such as music contents such as music recorded on a CD (Compact Disc) or downloaded via the Internet, and video contents such as movies and concert videos even outdoors. .

  Many portable electronic devices use a battery as a power source, and when the user is using the electronic device, the battery may be insufficient. Therefore, in order to protect the load circuit in the electronic device, it is preferable that the power supply to the load circuit is cut off when the input voltage to the load circuit falls below a set value. For example, Patent Document 1 below discloses a protection circuit that includes a shut-off circuit, a start-up circuit, and an abnormality detection circuit, and that makes the shut-off circuit non-conductive when an abnormal value is detected as an input voltage or an output voltage. .

Japanese Patent No. 3171383

  In the technique described in Patent Document 1, when the input voltage is restored after the cutoff circuit is turned off, the cutoff circuit is turned on. Thereby, the restart of the protection circuit can be facilitated. However, in a portable electronic device, a switch that maintains an on state or an off state, such as a slide switch, may be used as a power switch. In the technique described in Patent Document 1, when the slide switch remains in the ON state, energization to the load circuit in the electronic device is resumed when the output voltage of the battery temporarily recovers for some reason. End up.

  Therefore, it is desired to prevent resumption of energization when the input voltage temporarily increases after the energization of the load circuit is interrupted even if the switch remains in the on state.

In a first preferred embodiment of the present disclosure, the power supply control circuit includes:
A detection unit, a voltage conversion circuit, a first switching element, and a control unit are provided.
The detection unit has a connection with a power source and monitors an input voltage from the power source.
The voltage conversion circuit has an enable terminal, converts an input voltage from the power source into a desired voltage, and supplies power to at least the detection unit.
A first switching element is connected between the power supply and the enable terminal.
A control part switches a 1st switching element from ON to OFF by the input from a detection part.

According to a second preferred embodiment of the present disclosure, the electronic device is
A load circuit, a switch, a detection unit, a voltage conversion circuit, a first switching element, a control unit, and a second switching element are provided.
The switch mechanically holds the first state or the second state.
The detection unit has a connection with a power source and monitors an input voltage from the power source.
The voltage conversion circuit has an enable terminal, converts an input voltage from the power source into a desired voltage, and supplies power to the detection unit and the load circuit.
A first switching element is connected between the power supply and the enable terminal.
The control unit has a reset terminal connected to the switch, and switches the first switching element from on to off by an input from the detection unit.
The second switching element is connected between the power source and the first switching element, and is turned on or off depending on whether the switch is in the first state or the second state. .

According to a third preferred embodiment of the present disclosure, the noise-canceling headphones are
A microphone, a signal processing unit, a switch, a detection unit, a voltage conversion circuit, a first switching element, a control unit, and a second switching element are provided.
A microphone collects noise.
A signal processing unit generates a noise canceling signal from the input of the microphone.
The switch mechanically holds the first state or the second state.
The detection unit has a connection with a power source and monitors an input voltage from the power source.
The voltage conversion circuit has an enable terminal, converts an input voltage from the power source into a desired voltage, and supplies power to at least the detection unit and the signal processing unit.
A first switching element is connected between the power supply and the enable terminal.
The control unit has a reset terminal connected to the switch, and switches the first switching element from on to off by an input from the detection unit.
The second switching element is connected between the power source and the first switching element, and is turned on or off depending on whether the switch is in the first state or the second state. .

  In the present disclosure, the detection unit monitors the input voltage from the power source, and when the detection unit detects a decrease in the input voltage, the detection unit sends a signal to the control unit to notify the decrease in the input voltage. The control unit inputs a signal from the detection unit, and turns off the first switching element connected between the power supply and the enable terminal of the voltage conversion circuit. When the first switching element is turned off, the voltage conversion circuit is disabled, and power transmission from the voltage conversion circuit is interrupted. Therefore, even if the input voltage is temporarily recovered after the input voltage from the power supply is reduced, the supply of power from the voltage conversion circuit to the subsequent circuit is prevented from being resumed.

  In the present disclosure, when the electronic device includes a switch that mechanically holds the first state or the second state, the second switching element is connected between the power source and the first switching element. The second switching element is turned on or off depending on whether the switch is in the first state or the second state, and the reset terminal of the control unit is connected to the switch. Therefore, even if the input voltage from the power supply decreases and the supply of power from the voltage conversion circuit to the load circuit is cut off, or even when the input voltage is temporarily recovered, the user can operate the electronic device. Without restarting the supply of power to the load circuit. In addition, when the user operates the switch, the control unit is reliably reset.

  According to the present disclosure, it is possible to prevent resumption of energization when the input voltage temporarily rises after the energization of the load circuit is interrupted even when the switch remains on.

FIG. 1 is a schematic configuration diagram illustrating an electronic apparatus according to an embodiment of the present disclosure. FIG. 2 is a table showing the relationship between the flip-flop as the control unit and the operating state of the electronic device. FIG. 3A is a front view illustrating an appearance of a noise canceling headphone according to a second embodiment. FIG. 3B is an enlarged perspective view showing a portion A of FIG. 3A. FIG. 4 is a schematic configuration diagram illustrating a noise canceling headphone according to an embodiment of the present disclosure.

Hereinafter, embodiments of a power supply control circuit, an electronic device, and a noise canceling headphone will be described. The description will be made in the following order.
<1. First Embodiment>
[Schematic configuration of power supply control circuit and electronic equipment]
(Power supply)
(Switching element)
(Voltage conversion circuit)
(Detection unit)
(Control part)
(switch)
(Load circuit)
[Outline of operation of power supply control circuit and electronic equipment]
(initial state)
(When the power is turned on by the user)
(When the battery level is low when the switch is on)
(When the user restarts)
<2. Second Embodiment>
[Schematic configuration of noise canceling headphones]
(microphone)
(Noise canceling circuit)
(switch)
[Outline of operation of noise canceling headphones]
<3. Modification>

  The embodiment described below is a preferable specific example of a power supply control circuit, an electronic device, and a noise canceling headphone. In the following description, various technically preferable limitations are attached. Examples of the power supply control circuit, the electronic device, and the noise canceling headphones are as follows unless otherwise specified to limit the present disclosure. It is not limited to the embodiment shown.

<1. First Embodiment>
[Schematic configuration of power supply control circuit and electronic equipment]
FIG. 1 is a schematic configuration diagram illustrating an electronic apparatus according to an embodiment of the present disclosure. As illustrated in FIG. 1, the electronic device 11 includes a load circuit 17, a switch 9, a detection unit 3, a voltage conversion circuit 5, a first switching element Sd 1, a control unit 7, and a second switching element. Sd2. Among these, the power supply control circuit 1 according to the embodiment of the present disclosure can be configured from the detection unit 3, the voltage conversion circuit 5, the first switching element Sd <b> 1, and the control unit 7.

(Power supply)
The power source 10 is a power source for supplying power necessary for driving each part of the load circuit 17 and the power source control circuit 1. The electric power from the power supply 10 is sent to the load circuit via the voltage conversion circuit 5 described later.

  As the power supply 10, specifically, for example, a battery can be used. FIG. 1 shows a configuration example in which a battery is used as the power source 10. As the battery, either a primary battery or a secondary battery may be used. Of course, solar cells, fuel cells, enzyme cells, etc. may be used as the batteries.

(Switching element)
A switching element Sd1 and a switching element Sd2 are connected in series between the power supply 10 and an enable terminal EN of the voltage conversion circuit 5 described later. The switching element Sd1 and the switching element Sd2 are specifically transistors, for example, but are not limited thereto. Examples of the transistor include a bipolar transistor, a field effect transistor, and an electrostatic induction transistor. In the following description, a bipolar transistor is used as the switching element Sd1 and the switching element Sd2. However, the present invention is not limited to this. Of course, the switching element Sd1 and the switching element Sd2 may not be the same type of switching element.

(Voltage conversion circuit)
Specifically, the voltage conversion circuit 5 is, for example, a DC (Direct Current) -DC converter that converts an input voltage from the power supply 10 into a desired voltage and outputs the voltage. As a control method of the DC-DC converter, either a PWM (Pulse Width Modulation) method or a PFM (Pulse Frequency Modulation) method may be used. The electric power that has undergone voltage conversion by the voltage conversion circuit 5 is sent to the load circuit 17 and the detection unit 3 described later.

  The input or cutoff of the enable signal to the voltage conversion circuit 5 is switched by the switching element Sd1 and the switching element Sd2 connected in series between the power supply 10 and the enable terminal EN of the voltage conversion circuit 5. When the input of the enable signal is interrupted (may be the input of the disable signal), the operation of the voltage conversion circuit 5 is stopped, and the supply of power to the load circuit 17 and the detection unit 3 is stopped.

(Detection unit)
Specifically, the detection unit 3 is configured by a microcomputer including a CPU (Central Processing Unit), a memory, and the like, and monitors a decrease in input voltage from the power supply 10. When the detection unit 3 detects a decrease in the input voltage from the power supply 10, the detection unit 3 notifies the control unit 7 described later of the detection of the decrease in the input voltage.

(Control part)
Specifically, the control unit 7 includes a flip-flop. As the flip-flop, for example, an RS flip-flop with a clock input or a JK flip-flop can be used.

  The configuration example shown in FIG. 1 is an example in which the power supply control circuit is a synchronous circuit, but the power supply control circuit may be an asynchronous circuit. By making the power supply control circuit a synchronous circuit, the power supply control circuit can be easily designed.

  The input terminal DATA and the clock terminal CK of the control unit 7 are connected to the output terminal DATA and the clock terminal CK of the detection unit 3, respectively. An output signal and a clock signal from the detection unit 3 are input to the input terminal DATA and the clock terminal CK of the control unit 7, respectively.

  As shown in FIG. 1, the input terminal RESET of the control unit 7 is connected to the base of the switching element Sd2. The base of the switching element Sd2 is connected to the switch 9 of the electronic device 11 as will be described later. Therefore, the input terminal RESET of the control unit 7 is also connected to the switch 9 of the electronic device 11. The output terminal OUT of the control unit 7 is connected to the base of the switching element Sd1.

  Here, in the design of a power supply control circuit, a combination of a latch circuit using discrete parts (individual parts) such as transistors and resistors and a voltage monitoring IC called a reset IC (integrated circuit) is generally used. Is.

  However, since the latch circuit is assembled from discrete components, it is necessary to adjust the balance between the plurality of transistors. Further, in the configuration in which the reset signal from the reset IC is captured by the latch circuit, the number of parts increases and the area necessary for configuring the power supply control circuit increases. Furthermore, since there are variations in the reset ICs, the operation of the power supply control circuit may be unstable.

  In the present disclosure, since the flip-flop is used, the reset signal can be captured by one chip, and the number of components can be reduced. In the present disclosure, since the flip-flop is controlled by the microcomputer, the circuit design becomes easy. As will be described later, in the present disclosure, since the power supply control circuit 1 is reliably reset by the user's operation of the electronic device 11, the reliability of the power supply control circuit can be improved.

(switch)
The switch 9 is a switch for switching the operation state of the electronic device 11. FIG. 1 shows a case where the switch 9 is in the on state.

  The switch 9 is a switch that maintains an on state (first state) or an off state (second state). More specifically, the switch 9 is a switch in which an on state or an off state is mechanically held. The switch 9 may be any switch that maintains an on state or an off state. As the switch 9, for example, a slide switch, a rotary switch, a button switch, a toggle switch, a key switch, or the like can be used.

  One of the terminals of the switch 9 is connected to the base of the switching element Sd2, and the remaining terminal of the switch 9 is grounded.

(Load circuit)
The load circuit 17 is a circuit required for exhibiting the function of the electronic device 11 and is not particularly limited. Examples of the electronic device include, but are not limited to, a portable media player, an IC (integrated circuit) recorder, a portable radio, an electronic dictionary, and an LED (light-emitting diode) lighting device.

[Outline of operation of power supply control circuit and electronic equipment]
Hereinafter, an outline of operations of the power supply control circuit 1 and the electronic device 11 will be described with reference to FIGS. 1 and 2. In the following description, “H” indicates that an input or output signal is at a high level, and “L” indicates that an input or output signal is at a low level. Shall be shown. “X” indicates that the input or output signal is indefinite (which may be either H or L), and “↑” indicates a rising edge at which the input or output signal changes from L to H. Shall be shown. The same applies to the description in FIG.

(initial state)
First, a state in which the switch 9 is turned off and the electronic device 11 is not operating is referred to as an initial state. In the initial state, it is assumed that a power supply 10 is connected to the power supply control circuit 1. For example, the state before using the electronic device 11 (before the switch 9 is turned on) corresponds to the initial state.

  FIG. 2 is a table showing the relationship between the flip-flop as the control unit and the operating state of the electronic device. As shown in FIG. 2, in the initial state, the switch 9 is off, so that the switching element Sd2 is off. Therefore, no enable signal is input to the voltage conversion circuit 5, and no power is supplied from the voltage conversion circuit 5 to the load circuit 17. As shown in FIG. 2, in the initial state, both the input RESET and the output OUT of the flip-flop are set to H.

(When the power is turned on by the user)
Next, assuming that the input voltage from the power supply 10 is sufficiently high, the user turns on the switch 9 (hereinafter, the state in which the user turns on the switch 9 is referred to as “state 2” as appropriate). . When the switch 9 is turned on from the off state, the base of the switching element Sd2 is grounded, and the switching element Sd2 is turned on.

  Since the output OUT of the flip-flop is H, the switching element Sd1 is on, and the power supply voltage as an enable signal is applied to the enable terminal EN of the voltage conversion circuit 5 via the switching element Sd1 and the switching element Sd2. The Then, a power supply voltage is supplied from the voltage conversion circuit 5 to the detection unit 3, and the load circuit 17 is energized from the voltage conversion circuit 5, so that the electronic device 11 is in an operating state.

  When the input voltage from the power supply 10 is sufficiently high, the input DATA from the microcomputer to the flip-flop is L. On the other hand, when the switch 9 is changed from the off state to the on state, the input terminal RESET of the flip-flop is grounded, and the input RESET of the flip-flop becomes L. Since the output OUT of the flip-flop is H, the output OUT of the flip-flop is also H in state 2.

  Here, as shown in FIG. 1, for example, it is assumed that the electronic device 11 uses a battery as a power source. In this case, it is conceivable that the remaining battery level decreases while the electronic device 11 is being used. Therefore, even if the switch 9 remains on, it is desirable that the power supply to the load circuit 17 is interrupted inside the electronic device 11 when the remaining battery level decreases.

(When the battery level is low when the switch is on)
Next, it is assumed that the input voltage from the power source 10 is lower than the set value set in the detection unit 3 when the switch 9 is on (hereinafter, the input voltage from the power source 10 is detected when the switch 9 is on. The state where the value is lower than the set value set in the section is appropriately described as “state 3”.) That is, it is assumed that a decrease in input voltage from the power supply 10 is detected at the input terminal BAT of the detection unit 3.

  At this time, the output DATA from the microcomputer as the detection unit 3 is set to H. That is, the input DATA from the microcomputer to the flip-flop becomes H. When the input DATA of the flip-flop becomes H, the output OUT of the flip-flop is set to L by the rise of the clock signal input from the microcomputer.

  Then, the switching element Sd1 is turned off, and the application of the power supply voltage as the enable signal to the enable terminal EN of the voltage conversion circuit 5 is stopped. Accordingly, the energization from the voltage conversion circuit 5 to the detection unit 3 and the load circuit 17 is interrupted.

  As described above, in the state 3, since the switching element Sd1 is turned off, the energization to the load circuit 17 is cut off, and the electronic device 11 is in a non-operating state.

  Here, if the power switch of the electronic device is a button switch that returns to its original position when the pressed finger is released, once the power supply to the load circuit is cut off inside the electronic device, the load The non-conduction state to the circuit can be maintained.

  However, when a switch that is mechanically held in an on state or an off state is used as a power switch of the electronic device, for example, when the output voltage of the battery is temporarily recovered, the electronic device The energization of the load circuit inside is resumed.

  For example, when the battery is a chemical battery, a chemical reaction is used to generate a voltage, so that the output voltage can change depending on the usage environment. In addition, for example, when the vehicle moves from outdoors to indoors in winter, the output voltage that has been reduced outdoors may be recovered indoors due to an increase in the temperature around the battery.

  When the electronic device is an electronic device that does not have a display unit that visually notifies the user of the remaining battery level, the user is less likely to notice a change in the power supply voltage. In such an electronic device, if the output voltage of the battery is temporarily recovered and the load circuit can be energized, the battery may leak.

  Therefore, even when the output voltage of the battery is temporarily recovered, it is desirable that energization of the load circuit that has been interrupted is not resumed when the power switch is in the ON state.

  In the present disclosure, even when the output voltage of the battery is temporarily recovered, the switching element Sd1 is kept off, so that the power supply voltage as the enable signal is not applied to the enable terminal EN of the voltage conversion circuit 5. Not.

  Therefore, according to the present disclosure, even when the input voltage from the power supply is temporarily recovered while the power switch is turned on, it is possible to prevent the energization of the load circuit that has been interrupted once from being resumed. In other words, according to the present disclosure, the electronic device is prevented from being in an operating state without the user's intention.

(When the user restarts)
Next, for example, suppose that the user turns the switch 9 on again after turning the switch 9 off. In this case, since the user wants to operate the electronic device 11, it is necessary to resume energization of the load circuit 17.

  Once the user turns off the switch 9, the switching element Sd2 is turned off. In addition, since the switching element Sd1 is off, the energization from the voltage conversion circuit 5 to the detection unit 3 and the load circuit 17 remains cut off.

  At this time, when the switch 9 is once turned off, the input RESET of the flip-flop becomes H, and the flip-flop is reset.

  Further, for example, when the user replaces the battery, the battery is removed from the electronic device 11 so that power is not supplied to the flip-flop. In this case, the flip-flop is also reset.

  Thus, when the switch 9 is turned off or the battery is replaced by the user, the blocking of the enable signal to the voltage conversion circuit 5 is released, and the electronic device 11 returns from the state 3 to the initial state. .

  In the state where the electronic device 11 is operating (state 2), when the user turns off the switch 9 after using the electronic device 11, the switching element Sd2 is turned off, so that the detection unit 3 and The energization from the voltage conversion circuit 5 to the load circuit 17 is interrupted. In this case, flip-flop resetting is not required.

  According to the present disclosure, the power supply control circuit is surely reset by a user operation on the electronic device, so that the reliability of the power supply control circuit can be improved.

<2. Second Embodiment>
[Schematic configuration of noise canceling headphones]
FIG. 3A is a front view illustrating an appearance of a noise canceling headphone according to a second embodiment. FIG. 3B is an enlarged perspective view showing a portion A of FIG. 3A. As shown in FIG. 3A, the appearance of the noise canceling headphone 21 is composed of a headband 43, two sliders 45L and 45R, two hangers 47L and 47R, two housings 53L and 53R, and two ear pads 55L and 55R. The

  FIG. 4 is a schematic configuration diagram illustrating a noise canceling headphone according to an embodiment of the present disclosure. As shown in FIGS. 3A and 3B and FIG. 4, the noise canceling headphone 21 includes a microphone 26, a noise canceling circuit 27, a switch 29, a detection unit 23, a voltage conversion circuit 5, and a first switching. The device includes an element Sd1, a control unit 7, and a second switching element Sd2. That is, the noise canceling headphone 21 includes the power supply control circuit 2 of the present disclosure as a part thereof. 3A, FIG. 3B, and FIG. 4, illustration of an equalizer circuit, a filter circuit, a power amplifier, and the like is omitted.

  As shown in FIG. 3B, the noise canceling circuit 27, the power supply control circuit 2, and the battery as the power supply 10 are stored in, for example, one housing 53L.

  The headband 43 is formed in a curved shape along the user's head, and supports the entire noise canceling headphone 21 by contacting the user's head when the noise canceling headphone 21 is worn. A cushioning material such as rubber or sponge may be provided on at least a part of the inner surface of the headband 43 that is in contact with the top of the user's head.

  Sliders 45L and 45R are provided at both ends of the headband 43. As shown in FIG. 3A, the sliders 45L and 45R are made of, for example, three members so that they can expand and contract. For example, the slider 45L illustrated in FIG. 3A includes a combination of an upper cover body 45La, a rail 45Lb, and a lower cover body 45Lc. Therefore, when the noise canceling headphone 21 is worn, the degree of expansion / contraction of the sliders 45L and 45R can be adjusted in accordance with the distance between the user's ear and the top of the head.

  Thereby, the user can obtain a feeling of wearing according to his / her physical characteristics and preferences. Further, when the noise canceling headphones 21 are not used, the user can save the storage space for the noise canceling headphones 21 by setting the sliders 45L and 45R in a contracted state.

  Hangers 47L and 47R are provided at the ends of the sliders 45L and 45R, respectively. As shown in FIG. 3B, the hanger 47L is rotatably supported on the joint surface with the lower cover body 45Lc with an axis L1 perpendicular to the joint surface as a rotation axis. The hangers 47L and 47R support the housing 53L including the ear pad 55L and the housing 53R including the ear pad 55R, respectively.

  The hangers 47L and 47R have, for example, an arc shape. As shown in FIG. 3B, the housing 53L is rotatably supported with an axis L2 connecting both ends of the arc as a rotation axis.

  The housings 53L and 53R store an audio processing circuit, a driver unit, and the like. 3B shows a configuration example in which the microphone 26, the noise canceling circuit 27, the power supply control circuit 2, and the battery as the power supply 10 are stored in the one housing 53L, but the present invention is not limited thereto. The audio processing circuit, the driver unit, the noise canceling circuit 27, and the like may be stored in the housing 53R, or may be distributed and stored in the housing 53L and the housing 53R. However, with respect to the microphone, it is preferable that the microphone is provided in each of the housing 53L and the housing 53R in order to enhance the noise canceling effect.

(microphone)
The microphone 26 is a transducer for collecting noise inside or outside the housing. The noise information collected by the microphone 26 is sent to a noise canceling circuit 27 described later as an electrical signal. The microphone 26 may be a condenser type, ribbon type, moving coil type, or the like, but is not limited thereto.

(Noise canceling circuit)
The noise canceling circuit 27 includes a processor such as a digital signal processor (DSP), for example, and is a circuit that generates a noise canceling signal from an input of a microphone. Specifically, the noise canceling circuit 27 generates a reverse phase component of the noise collected by the microphone and sends it as a noise canceling signal. By supplying the noise canceling signal to the driver unit, the noise component is canceled out, and the noise perceived by the user is reduced.

  In the configuration example shown in FIG. 3B, a battery as the power source 10 is stored in the housing 53L. That is, in the configuration example shown in FIG. 3B, the power source for driving the noise canceling circuit 27 is independent of the power source for driving a playback device such as a music playback player. Therefore, the noise canceling headphone 21 is driven by using the battery stored in the housing 53L as a power source.

(switch)
For example, the housing 53 </ b> L is provided with a switch 29 for switching power supply or cutoff for driving the noise canceling circuit 27. Specifically, the switch 29 is, for example, a slide switch that is mechanically held in an on state or an off state. Therefore, when the user wants to obtain the noise canceling effect, the user turns on the switch 29. When the user turns on the switch 29, the noise canceling process is continued until the user turns off the switch 29 next time.

  As necessary, for example, the housing 53L is further provided with function buttons 28a and 28b for switching the noise canceling characteristics as shown in FIG. 3B. For example, the required noise canceling characteristics differ when the user is on an airplane, when the user is on a train, or when the user is in an office.

  The function buttons 28a and 28b have, for example, a connection with a detection unit 23 described later, and instructions from the user are transmitted to the detection unit 23 when the function buttons 28a and 28b are operated by the user.

(Detection unit)
In the second embodiment, the detection unit 23 monitors the decrease in the input voltage from the power supply 10 as in the detection unit 3 of the first embodiment. When the detection unit 23 detects a decrease in the input voltage from the power supply 10, the detection unit 23 notifies the control unit 7 of the detection of a decrease in the input voltage.

  The detection unit 23 also controls the entire system of the noise canceling headphones 21. As shown in FIG. 4, the communication between the detection unit 23 and the processor in the noise canceling circuit 27 is performed via a line between COM terminals. For example, when the energization of the detection unit 23 from the voltage conversion circuit 5 is interrupted, the processor in the noise canceling circuit 27 is stopped via the line between the COM terminals. For example, when the function buttons 28 a and 28 b for switching the noise canceling characteristics are provided on the housing 53 </ b> L, the detection unit 23 communicates with the noise canceling circuit 27 to perform the noise canceling characteristics. Switch.

  For example, when the user presses the function button 28a, the detection unit 23 sends a command signal to the processor in the noise canceling circuit 27, analyzes surrounding sounds, and selects an appropriate mode. For example, when the user presses the function button 28b, the detection unit 23 switches the noise canceling characteristics of the noise canceling headphones 21 to a monitor mode that makes it easy to hear surrounding sounds.

  For example, the housing 53L is provided with a jack 58j for connecting the cord 57. The jack 58j is electrically connected to the sound processing circuit inside the housing 53L. On the other hand, a plug 57p for insertion into the jack 58j is provided at the tip of the cord 57. For example, a music player is connected to the other end of the cord 57. That is, data such as music content is sent from the player to the noise canceling headphones 21 via the code 57.

[Outline of operation of noise canceling headphones]
Next, an outline of the operation of the noise canceling headphone 21 will be described with reference to FIG. In FIG. 4, only the driver unit 25 and the microphone 26 stored in the housing 53L are illustrated in order to facilitate understanding of the present disclosure, and the driver unit and the microphone stored in the housing 53R are not illustrated. ing. For example, when the noise canceling circuit 27 is stored only in one housing 53L, the communication between the driver unit and the microphone stored in the housing 53R is a transmission line or magnetic field communication arranged in the headband 43. Etc.

  As shown in FIG. 4, the power supply control circuit 2 is connected between the battery serving as the power supply 10 and the noise canceling circuit 27. Accordingly, the supply of power from the voltage conversion circuit 5 to the noise canceling circuit 27 is controlled by the operation of the switch 29 by the user and the switching element Sd1 being turned on or off by the control unit 7.

  For example, when the user turns the switch 29 from the off state (initial state) to the on state (state 2), the voltage conversion circuit 5 is enabled and power is supplied from the voltage conversion circuit 5 to the noise canceling circuit 27. .

  An input signal related to noise information sent from the microphone 26 is input to the input terminal MICIN of the noise canceling circuit 27. Further, an input signal 59 from the player is input to the input terminal AUDIOIN of the noise canceling circuit 27.

  The noise canceling circuit 27 generates a noise canceling signal from an input signal related to noise information, and performs addition with the input signal 59 from the player. A signal obtained by addition to the noise canceling signal is sent to the driver unit 25. Therefore, the driver unit 25 performs acoustic conversion of the signal in which the noise component is canceled, and the user can obtain the noise canceling effect.

  Now, it is assumed that the remaining battery level is reduced during use of the user's noise canceling headphones 21 (state 3). Then, the first switching element Sd1 is turned off by the control unit 7 and the power supply to the noise canceling circuit 27 is cut off, but the user cannot directly know the change in the power supply voltage. Therefore, when the input voltage from the power supply 10 is temporarily recovered, the power supply to the noise canceling circuit 27 may be resumed without the user's knowledge.

  Therefore, for example, in a noise-cancelling headphone that does not include a battery remaining amount display means, when the battery remaining amount is reduced while the noise-cancelling headphone is being used, the power supply to the noise-cancelling circuit is cut off. desirable. Furthermore, it is desirable that the energization to the noise canceling circuit is not resumed even if the output voltage of the battery is temporarily restored after the energization to the noise canceling circuit is interrupted.

  In the noise canceling headphone 21, when the remaining battery level is reduced during use (state 3), the power supply control circuit 2 cuts off the power supply from the voltage conversion circuit 5 to the noise canceling circuit 27. Furthermore, even when the output voltage of the battery is temporarily recovered, the switching element Sd1 remains off, so that the noise canceling circuit 27 from the voltage conversion circuit 5 is supplied as in the first embodiment. The power supply is not resumed. Thereafter, when the user turns off the switch 29 or replaces the battery, the block of the enable signal to the voltage conversion circuit 5 is released.

  According to the second embodiment, since the noise canceling headphones include the power supply control circuit, it is possible to cut off the energization to the noise canceling circuit when the remaining battery level decreases while the noise canceling headphones are in use. it can. In addition, after the power supply control circuit cuts off the power to the noise canceling circuit, even if the output voltage of the battery is temporarily recovered with the switch turned on, the power supply to the noise canceling circuit is resumed. Can be prevented. Therefore, according to the present disclosure, even when the input voltage from the power supply is temporarily recovered while the power switch is on, the noise canceling headphones are prevented from being in an operating state without the user's intention. The

  Thus, the power supply control circuit according to the present disclosure is suitable for application to an electronic device including a switch that holds an on state or an off state. In particular, the present disclosure is suitable for an electronic apparatus that uses a battery as a power source and does not have a display unit that visually notifies the user of the remaining battery level.

<3. Modification>
As mentioned above, although embodiment of this indication was described concretely, this indication is not limited to the above-mentioned embodiment, and various modification based on the technical idea of this indication is possible.

  For example, a latch circuit can be used as the control unit instead of the flip-flop.

  The power supply control circuit according to the embodiment is not limited to the noise-cancelling headphones, and can be applied to any electronic device including a switch that maintains a switching state. For example, the technology of the present disclosure can be applied to a laptop computer, an electronic book reader, a smartphone, a mobile phone, a hearing aid, a medical device, a toy, and the like.

  As a noise canceling method, either a feedback method or a feedforward method can be applied. The noise canceling process may be a digital process or an analog process.

  Note that the configurations and methods described in the above-described embodiments are merely examples, and different configurations and methods may be used as necessary. The configurations and methods of the above-described embodiments can be combined with each other without departing from the gist of the present disclosure.

For example, this indication can also take the following composition.
(1)
A detector having a connection to a power source and monitoring an input voltage from the power source;
A voltage conversion circuit having an enable terminal, converting the input voltage from the power source into a desired voltage and supplying power to at least the detection unit;
A first switching element connected between the power supply and the enable terminal;
And a control unit that switches the first switching element from on to off by an input from the detection unit.
(2)
A switch that mechanically holds the first state or the second state;
Second switching connected between the power source and the first switching element and switched on or off depending on whether the switch is in the first state or the second state And further comprising an element,
The control unit further includes a reset terminal,
The power supply control circuit according to (1), wherein the reset terminal is connected to the switch.
(3)
The power supply control circuit according to (2), wherein the switch is a slide switch.
(4)
The power supply control circuit according to any one of (1) to (3), wherein the detection unit is a microcomputer.
(5)
The power supply control circuit according to any one of (1) to (4), wherein the control unit is a flip-flop.
(6)
A load circuit;
A switch that mechanically holds the first state or the second state;
A detector having a connection to a power source and monitoring an input voltage from the power source;
A voltage conversion circuit that has an enable terminal, converts the input voltage from the power source into a desired voltage, and supplies power to the detection unit and the load circuit;
A first switching element connected between the power supply and the enable terminal;
A control unit having a reset terminal connected to the switch, and switching the first switching element from on to off by an input from the detection unit;
Second switching connected between the power source and the first switching element and switched on or off depending on whether the switch is in the first state or the second state An electronic device provided with an element.
(7)
The electronic device according to (6), wherein a battery is driven as the power source.
(8)
A microphone that collects noise,
A signal processing unit for generating a noise canceling signal from the input of the microphone;
A switch that mechanically holds the first state or the second state;
A detector having a connection to a power source and monitoring an input voltage from the power source;
A voltage conversion circuit that has an enable terminal, converts the input voltage from the power source into a desired voltage, and supplies power to at least the detection unit and the signal processing unit;
A first switching element connected between the power supply and the enable terminal;
A control unit having a reset terminal connected to the switch, and switching the first switching element from on to off by an input from the detection unit;
Second switching connected between the power source and the first switching element and switched on or off depending on whether the switch is in the first state or the second state Noise-canceling headphones with elements.

DESCRIPTION OF SYMBOLS 1, 2 ... Power supply control circuit 3, 23 ... Detection part 5 ... Voltage conversion circuit 7 ... Control part 9, 29 ... Switch 10 ... Power supply 11 ... Electronic device 17 ..Load circuit 21 ... Noise canceling headphones 26 ... Microphone 27 ... Noise canceling circuit EN ... Enable terminal RESET ... Reset terminal

Claims (8)

A detector having a connection to a power source and monitoring an input voltage from the power source;
A voltage conversion circuit having an enable terminal, converting the input voltage from the power source into a desired voltage and supplying power to at least the detection unit;
A first switching element connected between the power supply and the enable terminal;
And a control unit that switches the first switching element from on to off by an input from the detection unit. A switch that mechanically holds the first state or the second state;
Second switching connected between the power source and the first switching element and switched on or off depending on whether the switch is in the first state or the second state And further comprising an element,
The control unit further includes a reset terminal,
The power supply control circuit according to claim 1, wherein the reset terminal is connected to the switch. The power supply control circuit according to claim 2, wherein the switch is a slide switch. The power supply control circuit according to claim 2, wherein the detection unit is a microcomputer. The power supply control circuit according to claim 2, wherein the control unit is a flip-flop. A load circuit;
A switch that mechanically holds the first state or the second state;
A detector having a connection to a power source and monitoring an input voltage from the power source;
A voltage conversion circuit that has an enable terminal, converts the input voltage from the power source into a desired voltage, and supplies power to the detection unit and the load circuit;
A first switching element connected between the power supply and the enable terminal;
A control unit having a reset terminal connected to the switch, and switching the first switching element from on to off by an input from the detection unit;
Second switching connected between the power source and the first switching element and switched on or off depending on whether the switch is in the first state or the second state An electronic device provided with an element.   The electronic device according to claim 6, wherein a battery is driven as the power source. A microphone that collects noise,
A signal processing unit for generating a noise canceling signal from the input of the microphone;
A switch that mechanically holds the first state or the second state;
A detector having a connection to a power source and monitoring an input voltage from the power source;
A voltage conversion circuit that has an enable terminal, converts the input voltage from the power source into a desired voltage, and supplies power to at least the detection unit and the signal processing unit;
A first switching element connected between the power supply and the enable terminal;
A control unit having a reset terminal connected to the switch, and switching the first switching element from on to off by an input from the detection unit;
Second switching connected between the power source and the first switching element and switched on or off depending on whether the switch is in the first state or the second state Noise-canceling headphones with elements.

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