JP2012039759A - Power supply control device - Google Patents

Abstract

An object of the present invention is to detect connection of a power cable with a simple configuration while suppressing power consumption before the power cable is connected to a connector of an electrical device.
When a power cable 22 is not connected to a printer P, a magnetic switch 82 conducts between terminals A and B and a transistor T2 is turned on. For this reason, since the collector current of the phototransistor 75b of the photocoupler 75 increases and the FB voltage of the control IC 90 decreases and falls below the threshold value, the control IC 90 controls the element Q1 intermittently and outputs a low voltage to the secondary side. . When the power cable 22 is connected, the magnetic switch 82 cuts off the conduction between the terminals A and B by the action of the magnetic force of the magnet 102, and the transistor T2 is turned off. For this reason, since the collector current of the phototransistor 75b decreases and the FB voltage increases and exceeds the threshold value, the control IC 90 switches to normal oscillation control and controls the element Q1.
[Selection] Figure 1

Description

  The present invention relates to a power supply control device that supplies a power supply voltage to an electric device via a two-core power cable connected to a connector of the electric device.

  Conventionally, this type of power supply control device is connected to an electric device via a power cable, and a DC voltage rectified from the AC voltage is converted into an AC voltage by switching of a switching circuit driven by the control circuit to convert the transformer. An apparatus has been proposed in which an alternating voltage that is applied to the primary side and transformed to the secondary side of the transformer is rectified into a direct current voltage and supplied to an electrical device. (For example, refer to Patent Document 1). In this apparatus, a three-core cable having three connection terminals is used as a power cable, and two terminals connected to the current detection circuit among the three connection terminals are connected to the electrical equipment of the power cable. When the connection is released, the conduction is cut off and the flow of current to the current detection circuit is stopped. And the presence or absence of the connection of the power cable to the electric device is detected by detecting the presence or absence of the current flowing through the current detection circuit. In addition, when it is detected that the power cable is not connected to the electrical device, the control circuit switches the switching circuit so as to output a low voltage enough to ensure the operation of the current detection circuit to the secondary side. . Thus, it is possible to detect that the power cable is connected to the electric device while suppressing power consumption before the power cable is connected to the electric device.

JP 2003-299355 A

  However, in the above-described power supply control device, it is necessary to use a three-core power cable composed of three connection terminals in order to detect the connection of the power cable to an electrical device, so a two-core power source composed of two connection terminals. There are cases where the circuit configuration becomes complicated or the apparatus becomes larger than that using a cable.

  The main object of the power supply control device of the present invention is to detect connection of a power cable with a simple configuration while suppressing power consumption before the power cable is connected to a connector of an electrical device.

  The power supply control device of the present invention employs the following means in order to achieve the main object described above.

The power supply control device of the present invention is
A power supply control device for supplying a power supply voltage to an electric device via a two-core power cable connected to a connector of the electric device,
DC-AC conversion means for converting DC voltage from the power source into AC voltage by switching of the switching element;
Transforming means for transforming the converted AC voltage;
Output means for rectifying the transformed AC voltage into a DC voltage and outputting it as the power supply voltage to the power cable;
A control signal can be output to the switching element so that an AC voltage is output to the primary side with respect to the transformer, and when a start signal is input, the switching element is switched with a continuous oscillation operation. An integrated circuit that outputs the control signal and outputs the control signal so that the switching element is switched with an intermittent oscillation operation when the activation signal is not input;
A signal transmission means connected to the secondary side with respect to the transformer means, generating a signal in accordance with a current supplied from the secondary side, and transmitting the generated signal to the integrated circuit side;
A switch that is turned on and off in response to a physical action associated with the connection of the power cable to the connector or the release of the connection, and the activation signal is generated by the signal transmission means when the switch is turned on. And a switching means for switching a current supply state to the signal transmission means.

  In the power supply control device of the present invention, the integrated circuit outputs a control signal so that the switching element is switched with a continuous oscillation operation when a start signal is input, and switches when the start signal is not input. A control signal is output so that the element is switched with an intermittent oscillation operation. In addition, it has a switch that turns on and off in response to a physical action associated with connection to or disconnection from the power cable connector, and a signal generated according to the current supplied from the secondary side when the switch is turned on The current supply state to the signal transmission means is switched so that the start signal is generated by the signal transmission means for transmitting the signal to the integrated circuit side. As a result, when the power cable is not connected to the connector of the electrical device, the voltage is output to the secondary side with the intermittent oscillation operation of the switching element, so that useless power consumption can be suppressed. Also, when the power cable is connected to the connector, the start signal is transmitted from the signal transmission means to the integrated circuit side using the voltage output to the secondary side with intermittent oscillation operation. Can be detected. And since the detection of the connection of the power cable is performed by a physical action and the use of the two-core power cable is enabled, the circuit is compared with the one that detects the connection using the three-core power cable. It is possible to prevent the configuration from becoming complicated. As a result, it is possible to detect the connection of the power cable with a simple configuration while suppressing power consumption before the power cable is connected to the connector of the electrical device.

  Further, in the power supply control device according to the aspect of the present invention that supplies a power supply voltage to a device in which the connector is provided with a magnet member as the electrical device, the switch is configured as the physical action of the power cable. The action of the magnetic force from the magnet member by approaching the magnet member with connection to the connector and the action of the magnetic force from the magnet member by separating from the magnet member with release of the connection It can also be a magnetic switch that receives the release. Alternatively, in the power supply control device according to the aspect of the present invention that supplies a power supply voltage to a device in which a light shielding plate is provided on the connector as the electrical device, the switch receives a current supplied to the secondary side. A light-emitting element that emits light, and a light-receiving element that switches a current supply state to the signal transmission means based on the presence or absence of light reception, and as the physical action, accompanying the connection of the power cable to the connector The light shielding plate is located between the light receiving and emitting elements by blocking the light path from the light emitting element to the light receiving element due to the light shielding plate being positioned between the light receiving and emitting elements. It may be a switch that receives the opening of the optical path due to disconnection.

  In the power supply control device of the present invention, the integrated circuit has a voltage corresponding to a deviation between the voltage and the target voltage when the voltage of the signal transmitted from the signal transmission means is within a predetermined range. The control signal is generated so that the switching element is switched with the continuous oscillation operation together with feedback control to be output to the next side, and the voltage of the signal transmitted from the signal transmission means is within the predetermined range. A circuit that generates the control signal so that the switching element is switched with the intermittent oscillation operation when the switching element is outside, and the voltage of the start signal switches from outside the predetermined range to within the predetermined range It can also be a signal. In this way, the signal transmission means can be used for both the transmission of the feedback signal and the transmission of the activation signal, so that it is different from the case where the means for separately transmitting the feedback signal and the transmission of the activation signal are provided. Thus, the connection of the power cable can be detected with a simpler configuration.

FIG. 3 is a circuit diagram showing a circuit configuration of the AC adapter 10. FIG. 2 is a configuration diagram showing a configuration of a power cable 22 and a connector 100 of a printer P. Explanatory drawing which shows the mode of operation | movement of the magnetic switch 82. FIG. A circuit diagram showing circuit composition of AC adapter 10A of a modification. The block diagram which shows the structure of the power cable 22A and connector 100A of a modification. Explanatory drawing which shows the mode of the change of the optical path of the photocoupler 85. FIG.

  Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a circuit diagram showing a circuit configuration of an AC adapter 10 according to an embodiment of the present invention. As shown in the figure, the AC adapter 10 according to the present embodiment uses a power cable 22 connected to the connector 100 (see FIG. 2) of the printer P and a commercial power supply (such as AC100V) as a predetermined DC voltage (such as DC20V or 42V). And a power supply circuit 20 that supplies power to the printer P through connection between the power cable 22 and the connector 100. The printer P is configured as a well-known ink jet printer that performs printing by discharging ink onto a fed sheet, and includes various drive motors and print heads that are driven by power supply. A load L is provided.

  The power supply circuit 20 includes, as main components, a first rectifier circuit 30 that rectifies a commercial power supply and outputs a DC voltage, and converts the DC voltage output from the first rectifier circuit 30 into an AC voltage by switching. A switching circuit 40; a transformer 50 that transforms the AC voltage converted by the switching circuit 40; a second rectifier circuit 60 that rectifies the AC voltage transformed by the transformer 50 and outputs a DC voltage; and a second rectifier. A constant voltage control circuit 70 for controlling the output of a photocoupler 75 (shown separately for a light emitting diode 75a as a light emitting element and a phototransistor 75b as a light receiving element) in accordance with the DC voltage output from the circuit 60; A cable connection detector 80 for detecting whether the cable 22 is connected to the connector 100 of the printer P; And a control IC90 for generating and outputting a signal for switching control to the switching circuit 40 in accordance with the output from the puller 75. The side on which the first rectifier circuit 30, the switching circuit 40, and the control IC 90 are disposed across the transformer 50 is referred to as a primary side, and the second rectifier circuit 60 and the constant voltage control circuit 70 are disposed. The side is referred to as the secondary side.

  The first rectifier circuit 30 includes a diode bridge 32 in which four diodes connected to a commercial power supply are combined, and a smoothing capacitor C1 connected to the diode bridge 32. In the first rectifier circuit 30, the commercial power supply is full-wave rectified by the diode bridge 32, and a DC voltage smoothed by the smoothing capacitor C <b> 1 is output.

  The switching circuit 40 has a switching element Q1 such as a MOS FET whose gate is connected to the control IC 90 via the resistor R2 and whose drain is connected to the transformer 50, and for current detection connected to the source of the switching element Q1. It is comprised by resistance R3. In the switching circuit 40, the DC voltage output from the rectifier circuit 30 is converted into an AC voltage by the switching operation of the switching element Q1.

  The transformer 50 includes a primary winding 52 connected to the output side of the first rectifier circuit 30 and the drain of the switching element Q1 of the switching circuit 40, and a secondary winding 54 connected to the second rectifier circuit 60. And an auxiliary winding 56 connected to the smoothing capacitor C2 via the diode D2. In this transformer 50, an AC voltage converted by the switching operation of the switching element Q1 is applied to the primary winding 52, whereby an AC voltage corresponding to the winding number ratio of each winding is supplied to the secondary winding 54 or the auxiliary winding. Induced by winding 56.

  The second rectifier circuit 60 includes a diode D3 connected to the secondary winding 54 of the transformer 50 and a smoothing capacitor C3 connected to the diode D3. In the second rectifier circuit 60, a DC voltage obtained by smoothing the AC voltage induced in the secondary winding 54 of the transformer 50 by half-wave rectification is output as an output voltage between the Vout terminal and the GND terminal of the power cable 22. To do.

  Here, FIG. 2 is a configuration diagram showing the configuration of the power cable 22 and the connector 100 of the printer P. 2A shows a state of connection between the power cable 22 and the connector 100, FIG. 2B shows a connection surface connected to the connector 100 of the power cable 22, and FIG. The connection surface connected to the power cable 22 is shown. The power cable 22 includes two connecting magnets 94 disposed in the vicinity of both ends of the connection surface, and two terminal holes 96 serving as power supply terminals (Vout terminal, GND terminal). In addition, a part of the magnetic switch 82 of the cable connection detection unit 80 is exposed from the connection surface of the power cable 22. On the other hand, the connector 100 of the printer P is connected to two iron plates 104 disposed in the vicinity of both ends of the connection surface so as to face the connection magnet 94 in a connected state where the power cable 22 is connected. Two terminal pins 106 connected to a power supply control circuit (not shown) of the printer P provided at positions opposed to the two terminal holes 96 and a position facing the magnetic switch 82 partially exposed are provided. It is comprised with the magnet 102 for an operation | movement. The power cable 22 is configured as a so-called magnet plug that is connected to the connector 100 when the connecting magnet 94 and the iron plate 104 are attracted to each other by magnetic force. In addition, the exposed surface of the magnetic switch 82 and the facing surface of the working magnet 102 that faces the exposed surface of the magnetic switch 82 are configured to have different magnetic poles. For this reason, the magnetic switch 82 and the actuating magnet 102 act to attract each other by the magnetic force as the power cable 22 is connected to the connector 100. Further, as the power cable 22 is detached from the connector 100, the action of the attractive force due to the magnetic force is eliminated. Thus, the actuating magnet 102 functions as a magnet for actuating the magnetic switch 82 by the action of the attractive force due to the magnetic force.

  In the constant voltage control circuit 70, the anode side is connected to the Vout terminal via the resistor R4, the light emitting diode 75a that emits light by receiving the supply of the secondary side current, and the collector are connected to the FB terminal to be described later of the control IC 90 on the primary side. A divided voltage connected between a photodiode 75 comprising a photocoupler 75b connected and connected to the ground and receiving light emitted from the light emitting diode 75a and through which a collector current flows, and between the Vout terminal and the ground (GND terminal). Resistors R5 and R6, a Zener diode TD1 whose anode side is grounded, a collector is connected to the cathode side of the light emitting diode 75a, an emitter is connected to the cathode side of the Zener diode TD1, and the base is the voltage dividing resistors R5 and R6. Transistor T1 connected to the connection point, transistor T1-based - is constituted by a condenser C4 connected between the collector. In this constant voltage control circuit 70, the secondary output voltage divided by the voltage dividing resistors R5 and R6 is input to the base of the transistor T1, the transistor T1 is turned on, and a predetermined Zener voltage is applied to the Zener diode TD1. When a voltage exceeding (breakdown voltage) is applied, a current flows through the light emitting diode 75a. In addition to this case, a current may flow through the light emitting diode 75a, which will be described in detail later. When the current flowing through the light emitting diode 75a changes due to the change in the output voltage on the secondary side, the amount of light received by the phototransistor 75b changes and the collector current changes, so the voltage applied to the FB terminal of the control IC 90 changes. become. For this reason, a signal (voltage) corresponding to the output voltage on the secondary side is input to the FB terminal of the control IC 90.

  The cable connection detection unit 80 includes a transistor T2 having a collector connected to a connection point between the light emitting diode 75a and the collector of the transistor T1, and an emitter grounded to the ground, and an A terminal and a transistor connected to the Vout terminal via a resistor R7. The magnetic switch 82 is configured to switch between conduction with the B terminal connected to the base of T2 and interruption of conduction. Here, FIG. 3 is an explanatory view showing a state of operation of the magnetic switch 82. FIG. 3A shows a state of the magnetic switch 82 when the power cable 22 is detached from the connector 100. In this case, the magnetic switch 82 is located at the initial position by the urging force of the spring 82a and conducts the A terminal and the B terminal. Therefore, a current corresponding to the voltage output to the Vout terminal flows through the resistor R7, the A terminal, and the B terminal through the base of the transistor T2, and the transistor T2 is turned on. On the other hand, FIG. 3B shows a state of the magnetic switch 82 when the power cable 22 is connected to the connector 100. In this case, as described above, the magnetic switch 82 and the actuating magnet 102 act to attract each other by the magnetic force as the power cable 22 is connected to the connector 100, so that the magnetic force is resisted against the biasing force of the spring 82a. The switch 82 is attracted to the operating magnet 102 side (upper side in the drawing) to cut off the conduction between the A terminal and the B terminal. For this reason, the current flowing through the base of the transistor T2 is cut off, and the transistor T2 is turned off.

  The control IC 90 is configured as an IC chip for controlling the switching of the switching element Q1, and includes an FB terminal connected to the collector of the phototransistor 75b, a switching element Q1 and a current detecting element for detecting the current value of the switching element Q1. An IS terminal to which a potential at a connection point with the resistor R3 is input, a GND terminal connected to the ground, an OUT terminal for outputting a control signal for switching to the gate of the switching element Q1, a resistor R1 and a diode D1 Are connected to the diode bridge 32 of the first rectifier circuit 30 via the VH terminal to which the voltage for starting the control IC 90 is input, and are induced by the auxiliary winding 56 of the transformer 50 to provide the diode D2 and the smoothing capacitor C2. VCC terminal to which rectified and smoothed DC voltage is input Equipped with a. The control IC 90 is driven by the voltage input from the VH terminal when the switching control is not performed, and is induced by the auxiliary winding 56 of the transformer 50 and input from the VCC terminal while the switching control is performed. Driven by.

  The control IC 90 is configured to apply (pull up) a predetermined voltage to the FB terminal using a voltage input from the VH terminal or the VCC terminal. Further, as described above, the FB terminal is connected to the collector of the phototransistor 75b. For this reason, when the current flowing through the light emitting diode 75a increases due to a decrease in the current flowing through the load L of the printer P, the collector current of the phototransistor 75b increases, so the voltage applied to the FB terminal (hereinafter referred to as the FB voltage) is It becomes smaller than a predetermined voltage. In this case, the control IC 90 generates a control signal for switching by adjusting the duty ratio so that the ON time of the switching element Q1 is shortened, and outputs the generated control signal from the OUT terminal. Thereby, the output voltage on the secondary side of the transformer 50 can be reduced. On the other hand, when the current flowing through the light emitting diode 75a decreases due to an increase in the current flowing through the load L of the printer P, the collector current of the phototransistor 75b decreases, so the FB voltage increases and approaches a predetermined voltage. Become. In this case, the control IC 90 generates a control signal for switching by adjusting the duty ratio so that the ON time of the switching element Q1 becomes long, and outputs the generated control signal from the OUT terminal. Thereby, the output voltage on the secondary side of the transformer 50 can be increased. As described above, the control IC 90 performs feedback control of the switching element Q1 using the collector current of the phototransistor 75b as a feedback signal acting on the FB terminal so that the output voltage on the secondary side becomes a desired voltage. Further, in the control IC 90, when the FB voltage is in a predetermined range exceeding the threshold value Vref, a control signal is generated so that the switching element Q1 is switched at a regular oscillation frequency with such feedback control ( Hereinafter referred to as normal oscillation control). On the other hand, when the FB voltage is less than the threshold value Vref and out of the predetermined range, a control signal is generated so that the switching element Q1 is switched with an oscillation frequency in intermittent oscillation (burst mode) (hereinafter referred to as intermittent oscillation control). Called).

  Next, the operation of the thus configured AC adapter 10 of the present embodiment, particularly the operation when the power cable 22 is connected to the connector 100 of the printer P will be described. First, a state where the power cable 20 is not connected to the connector 100 will be described. Here, in the present embodiment, the switching element Q1 is switched by the control IC 90 even when the power cable 20 is not connected, and thus a voltage is output to the secondary side. At this time, in the cable connection detection unit 80, since the magnet switch 82 is not affected by the magnetic attractive force from the operating magnet 102 of the connector 100 (see FIG. 3A), the terminals A and B are electrically connected. The transistor T2 is turned on. Therefore, a current flows from the output terminal Vout through the resistor R4, the light emitting diode 75a, and the collector-emitter of the transistor T2. As a result, the collector current of the phototransistor 75b flows, and the FB voltage at the FB terminal of the control IC 90 decreases. In this embodiment, the FB voltage in this case is configured to be lower than the threshold value Vref described above. Therefore, in a state where the power cable 20 is not connected to the connector 100, the control IC 90 performs intermittent oscillation control, so that a relatively low voltage is output as the output voltage on the secondary side. The transistor T2 continues to be turned on by this output voltage, and the FB voltage at the FB terminal of the control IC 90 is kept below the threshold value Vref, so that the intermittent oscillation control is continued. This state will be continued.

  Next, a case where the power cable 22 is connected to the connector 100 of the printer P will be described. When the power cable 20 is connected to the connector 100, in the cable connection detection unit 80, the magnet switch 82 receives the action of an attractive force due to the magnetic force from the operating magnet 102 of the connector 100 (see FIG. 3B), so the terminal The conduction between A and B is cut off, and the transistor T2 is turned off. As a result, the collector-emitter of the transistor T2 is cut off, and the current flowing through the light emitting diode 75a gradually decreases. Immediately after the transistor T2 is turned off, the output voltage on the secondary side is in a low voltage state, so that a current flows from the light emitting diode 75a to the Zener diode TD1 via the collector-emitter of the transistor T1. It is not. For this reason, the collector current of the phototransistor 75b gradually decreases, and the FB voltage at the FB terminal of the control IC 90 gradually increases. When the FB voltage exceeds the threshold value Vref, the control IC 90 switches from intermittent oscillation control to normal oscillation control, and a voltage necessary for operating the load L of the printer P is output to the secondary side with feedback control. The switching element Q1 is controlled as described above. In this way, the connection of the power cable 20 to the connector 100 can be detected, and the intermittent oscillation control can be switched to the normal oscillation control. For this reason, when the FB voltage exceeds the threshold value Vref, that is, the signal input to the FB terminal due to the collector current of the phototransistor 75b becomes less than the threshold value Vref and becomes equal to or higher than the threshold value Vref. It can be said that it functions as an activation signal for switching. Since the detection of the connection of the power cable 20 is performed using the low voltage output to the secondary side by the intermittent oscillation control, the power consumption can be suppressed. In addition, since the operation magnet 102 for operating the magnetic switch 82 of the cable connection detection unit 80 is provided in the connector 100 and the two-core power cable 22 is used, compared with the one using the three-core power cable. And a simple circuit configuration. Further, the lower limit of the predetermined range for performing feedback control is set as the threshold value Vref, and the intermittent oscillation control and the normal oscillation control are switched with the threshold value Vref as a boundary. Therefore, the signal and the constant voltage control when the connection of the power cable 22 is detected. It is possible to switch the control by inputting without distinguishing it from the feedback signal for use. Thereby, it can be set as a simpler structure compared with what provides the circuit which outputs the signal which detected the connection of the power cable 22 separately. When the power cable 20 is removed from the connector 100, the attractive force due to the magnetic force acting on the magnetic switch 82 from the actuating magnet 102 is eliminated, and the magnetic switch 82 returns to the initial state by the urging force of the spring 82a. For this reason, the terminals A and B are made conductive, the transistor T2 is turned on, and the state is switched again to the intermittent oscillation control.

  Here, the correspondence between the components of the present embodiment and the components of the present invention will be clarified. The switching circuit 40 of this embodiment corresponds to “DC / AC conversion means” of the present invention, the transformer 50 corresponds to “transformation means”, the second rectifier circuit 60 corresponds to “output means”, and the control IC 90 The constant voltage control circuit 70 including the photocoupler 75 corresponds to “integrated circuit”, corresponds to “signal transmission means”, and the cable connection detection unit 80 corresponds to “switching means”. The magnetic switch 82 corresponds to a “switch”.

  According to the AC adapter 10 of this embodiment described in detail above, when the power cable 22 is not connected to the connector 100 of the printer P, the magnetic switch 82 that is not affected by the magnetic force from the operating magnet 102 provided on the connector 100. Is connected between the terminals A and B and the transistor T2 is turned on, so that the collector current of the phototransistor 75b of the photocoupler 75 increases, the FB voltage of the control IC 90 decreases and falls below the threshold Vref, and the control IC 90 has the element Q1. Is controlled intermittently to output a low voltage to the secondary side. When the power cable 22 is connected, the magnetic switch 82 is actuated by receiving the attractive force generated by the magnetic force from the actuating magnet 102, cuts off the conduction between the terminals A and B, and the transistor T2 is turned off. The collector current of the phototransistor 75b decreases and the FB voltage increases to exceed the threshold value Vref, and the control IC 90 switches to normal oscillation control to control the element Q1. As a result, when the power cable 22 is not connected, the switching element Q1 is intermittently controlled to output a low voltage to the secondary side, so that wasteful power consumption before the power cable 22 is connected can be suppressed. it can. Further, it is possible to switch to normal oscillation control by detecting that the power cable 22 is connected using the low voltage output to the secondary side by intermittent oscillation control. Since the operation magnet 102 for operating the magnetic switch 82 of the cable connection detection unit 80 is provided on the connector 100, the connection can be detected even when the two-core power cable 22 is used. A simple circuit configuration can be obtained as compared with a case where connection is detected using a cable. Furthermore, since the signal for detecting the connection of the power cable 22 is output from the constant voltage control circuit 70, the configuration is simpler than that in which a circuit for outputting the connection detection signal is provided individually. Can do.

  In addition, this invention is not limited to the embodiment mentioned above at all, and it cannot be overemphasized that it can implement with a various aspect, as long as it belongs to the technical scope of this invention.

  In the above-described embodiment, the magnetic switch 82 is operated by the magnetic attractive force in the cable connection detection unit 80. However, the present invention is not limited to this, and the magnetic switch 82 may be operated by the magnetic repulsive force.

  In the embodiment described above, both the signal when the connection of the power cable 22 is detected and the feedback signal for constant voltage control are output from the constant voltage control circuit 70. However, the present invention is not limited to this. The signal when the connection of 22 is detected and the feedback signal for constant voltage control may be output from separate circuits. However, in order to have a simple configuration, the configuration as in this embodiment is preferable.

  In the above-described embodiment, the cable connection detection unit 80 is configured using the magnetic switch 82 that is operated by the magnetic force from the operation magnet 102 provided in the connector 100. Any configuration can be used as long as it can detect the connection to the connector 100. For example, it may be configured using a photocoupler whose optical path is switched by a blocking plate provided in the connector 100. A modified example in that case will be described. 4 is a circuit diagram showing a circuit configuration of an AC adapter 10A according to a modified example, FIG. 5 is a configuration diagram showing a configuration of the power cable 22A and the connector 100A according to the modified example, and FIG. It is explanatory drawing which shows the mode of a change of an optical path. 4-6, the same code | symbol is attached | subjected about the same structure as FIGS. 1-3, and the description is abbreviate | omitted. As shown in FIG. 4, the cable connection detection unit 80A of the power supply circuit 20A includes a transistor T2 having the same configuration as that of the present embodiment, a light emitting diode 85a whose anode side is connected to the output terminal Vout and whose cathode side is connected to the GND terminal, A photocoupler 85 (not shown in the figure) is composed of a phototransistor 85b having a collector connected to the output terminal Vout via a resistor R7 and an emitter connected to the base of the transistor T2. Further, as shown in FIG. 5, a light shielding plate 107 is provided in the connector 100A. On the other hand, the power supply connector 22A is formed with a receiving groove 85c so that the light shielding plate 107 fits in the state connected to the connector 100A. The receiving groove 85c is formed between the light emitting diode 85a and the phototransistor 85b as shown in FIG. Therefore, when the power cable 22A is detached from the connector 100A, the optical path from the light emitting diode 85a to the phototransistor 85b is opened as shown in FIG. 6A. At this time, since a collector current flows through the phototransistor 85b, the transistor T2 can be turned on. Therefore, as in the present embodiment, when the power cable 22A is disconnected from the connector 100A, the current flowing through the light emitting diode 75a increases and the collector current of the phototransistor 75b increases. For this reason, the voltage of the FB terminal falls below the threshold value Vref, and intermittent oscillation control is performed. Further, when the power cable 22A is connected to the connector 100A, as shown in FIG. 6B, the light shielding plate 107 fits into the receiving groove 85c. Therefore, the light path from the light emitting diode 85a to the phototransistor 85b is blocked by the light shielding plate 107. Therefore, as in the present embodiment, since the transistor T2 is turned off, the current flowing through the light emitting diode 75a is reduced, and the collector current of the phototransistor 75b is reduced. For this reason, the voltage at the FB terminal gradually increases and exceeds the threshold value Vref, and the intermittent oscillation control is switched to the normal oscillation control. Thus, as in the present embodiment, it can be detected that the power cable 22A is connected to the connector 100A of the printer P, and the same effects as in the present embodiment can be achieved.

  In the present embodiment, the present invention is applied to the AC adapter 10 that controls the power supply to the printer P. However, the present invention is not limited to this, and any device that operates with the power from the AC adapter may be a portable personal computer. The present invention may be applied to any other electric device such as a computer, a video camera, a music player, or a portable information terminal.

  10, 10A AC adapter, 20, 20A power circuit, 22, 22A power cable, 30 first rectifier circuit, 32 diode bridge, 40 switching circuit, 50 transformer, 52 primary winding, 54 secondary winding, 56 auxiliary Winding, 60 second rectifier circuit, 70 constant voltage control circuit, 75 photocoupler, 75a light emitting diode, 75b phototransistor, 80, 80A cable connection detector, 82 magnetic switch, 82a spring, 85 photocoupler, 85a light emission Diode, 85b Phototransistor, 85c Receiving groove, 90 Control IC, 94 Connecting magnet, 96 Terminal hole, 100, 100A Connector, 102 Actuating magnet, 104 Iron plate, 106 Terminal pin, 107 Shading plate, A, B terminal, C1 , C2, C3, C Condenser, D1, D2, D3 diodes, L load, P printer, Q1 switching element (MOS type FET), R1, R2, R3, R4, R5, R6, R7 resistors, T1, T2 transistors, TD1 Zener diode.

Claims (4)

A power supply control device for supplying a power supply voltage to an electric device via a two-core power cable connected to a connector of the electric device,
DC-AC conversion means for converting DC voltage from the power source into AC voltage by switching of the switching element;
Transforming means for transforming the converted AC voltage;
Output means for rectifying the transformed AC voltage into a DC voltage and outputting it as the power supply voltage to the power cable;
A control signal can be output to the switching element so that an AC voltage is output to the primary side with respect to the transformer, and when a start signal is input, the switching element is switched with a continuous oscillation operation. An integrated circuit that outputs the control signal and outputs the control signal so that the switching element is switched with an intermittent oscillation operation when the start signal is not input;
A signal transmission means connected to the secondary side with respect to the transformer means, generating a signal in accordance with a current supplied from the secondary side, and transmitting the generated signal to the integrated circuit side;
A switch that is turned on and off in response to a physical action associated with the connection of the power cable to the connector or the release of the connection, and the activation signal is generated by the signal transmission means when the switch is turned on. And a switching means for switching a current supply state to the signal transmission means. The power supply control device according to claim 1, wherein a power supply voltage is supplied to a device in which a magnetic member is provided in the connector as the electrical device.
The switch has, as the physical action, an action of a magnetic force from the magnet member by being close to the magnet member as the power cable is connected to the connector, and the magnet as the connection is released. A power supply control device that is a magnetic switch that receives the release of the action of magnetic force from the magnet member by being separated from the member. The power supply control device according to claim 1, wherein a power supply voltage is supplied to a device in which a light shielding plate is provided on the connector as the electrical device.
The switch includes a light emitting element that emits light upon receiving a current supplied to the secondary side, and a light receiving element that switches a current supply state to the signal transmission unit based on whether light is received or not. As a function, the light shielding plate is positioned between the light receiving and emitting elements in connection with the connection of the power cable to the connector, and the light path from the light emitting element to the light receiving element is interrupted and the connection is released. Accordingly, the power control device is a switch that receives the opening of the optical path when the light shielding plate is out of the position between the light emitting and receiving elements. The power supply control device according to any one of claims 1 to 3,
The integrated circuit performs feedback control so that when a voltage of a signal transmitted from the signal transmission means is within a predetermined range, a voltage corresponding to a deviation between the voltage and a target voltage is output to the secondary side. And generating the control signal so that the switching element is switched with the continuous oscillation operation, and when the voltage of the signal transmitted from the signal transmission means is outside the predetermined range, the switching element is A circuit for generating the control signal to be switched with an intermittent oscillation operation;
The power supply control device, wherein the activation signal is a signal for switching a voltage from outside the predetermined range to within the predetermined range.

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