JP2009296883A - Device and method for power supply - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To compensate variations in voltage and current at the end of a power supply line even if an AC adapter and electronic apparatus are connected to each other by two terminals. <P>SOLUTION: The positive electrode terminal of a power source 1 is connected to a terminal T1 via an internal resistor 7, and its negative electrode terminal is connected to a terminal T2 via a resistor 3 and an internal resistor 8. A current detecting circuit 2 detects an output current and supplies the current to a calculating circuit 5. A voltage detecting circuit 4 detects an output voltage and supplies the voltage to the calculating circuit 5. The calculating circuit 5 calculates resistance value when the internal resistors 7 and 8 are compounded to each other when there flow currents i1 and i2, and the calculated resistance values r1 and r2 are supplied to a control circuit 6. The control circuit 6 determines whether the supplied resistance values r1 and r2 conform to each other or not. When it is determined that the resistance values r1 and r2 substantially conform to each other, the voltage output from the power source part 1 is output successively as it is, and when it is determined that they are not in conformity, the voltage output from the power source part 1 is compensated and output. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a power supply apparatus and a power supply method for supplying a predetermined voltage and current to an electronic device even when the internal resistance of an extended power supply line changes.

  Currently, secondary batteries that can be repeatedly charged are used in various electronic devices. When charging the secondary battery, a voltage and a current that match the charging characteristics of the secondary battery are supplied from, for example, an AC (Alternating Current) adapter. Depending on the secondary battery, if a voltage and current that do not match the charging characteristics are supplied from the AC adapter, the secondary battery may be damaged.

  The AC adapter may be provided with a power supply line for connecting to an electronic device. Since this power supply line has a predetermined impedance (hereinafter referred to as “internal resistance”), the output terminal of the power supply line connected to the electronic device becomes lower than a predetermined voltage due to a voltage drop due to the internal resistance. Therefore, the voltage drop due to the internal resistance is corrected so that a predetermined voltage is obtained at the output terminal of the power supply line.

  For example, the output voltage Vo of the power supply device 2 increases (or decreases) in response to an increase (or decrease) in the load current Io. As a result, when the load current Io is large, a series resistance Rw connected to the load RL. Since the output voltage Vo of the power supply device body 2 is increased by the output voltage correction circuit 4 and the load current Io is small, the voltage drop due to the resistance component Rw becomes small. 4, the voltage drop is corrected so that the output voltage Vo is lowered, and thus the applied voltage Vm to the load RL is maintained substantially constant even when the load current Io increases or decreases (for example, patents). Reference 1).

JP-A-7-104870

  When the electronic device is connected to the AC adapter, the AC adapter is operated with low power, and a code signal (voltage) generated with the supplied low power is transmitted from the electronic device to the AC adapter. It is determined whether or not the electronic device has a correct correspondence relationship with the adapter, and when it is determined that the electronic device has a correct correspondence relationship, there is a device that outputs a large amount of power to the electronic device (for example, see Patent Document 2). .)

Japanese Patent Laid-Open No. 11-122809

  However, even if the voltage drop is corrected in advance as in Patent Document 1, the use of the AC adapter deteriorates the power supply line and increases the internal resistance, or is used for the AC adapter. In the case where an element deteriorated and outputs a voltage and current different from the predetermined voltage and current, the predetermined voltage and current could not be supplied to the electronic device from the AC adapter with the correct correction. .

  In particular, since the power supply line composed of a plurality of thin electric wires is twisted or stretched by being used by the user, the thin electric wires are cut, so that the internal resistance is increased. That is, by using the AC adapter, there is a problem that the internal resistance of the extended power supply line is increased, and the voltage supplied to the electronic device is decreased due to a voltage drop.

  Further, as in Patent Document 2, even when the code signal is transmitted from the electronic device to the AC adapter when the electronic device is connected to the AC adapter, large power is output from the AC adapter to the electronic device. Meanwhile, in order to transmit and receive signals between the AC adapter and the electronic device, it is necessary to provide a dedicated line for transmitting signals.

  For example, as shown in FIG. 23, a switching circuit 101 and a voltage detection circuit 102 are provided on the AC adapter side, and a communication circuit 103 and a voltage detection circuit 104 are provided on the electronic device side. The AC adapter and the electronic device are connected through three terminals 105, 106, and 107, and can communicate with each other via the terminal 106.

  As described above, the voltage and current values output from the AC adapter can be corrected with three terminals provided with a dedicated line for transmitting or transmitting / receiving signals. There were a problem that the method is different because there are many types, and a problem that it is expensive because one more terminal is added.

  Accordingly, an object of the present invention is to provide a power supply device and a power supply method capable of correcting fluctuations in voltage and current at the output terminal of a power supply line even if the AC adapter and the electronic device are connected with two terminals. There is to do.

In order to achieve the above-described problems, the present invention provides a power supply device that supplies a predetermined voltage and current to an electronic device.
The electronic device has voltage detection means,
The power supply device has output voltage control means for controlling the output voltage,
When a voltage lower than a predetermined voltage is detected by the voltage detection means, the electronic device and the voltage detection means communicate with each other, and the output voltage control means controls the output voltage so as to become the predetermined voltage. The power supply device.

Further, the present invention provides a power supply method for supplying a predetermined voltage and current from an electric power supply device to an electronic device.
The electronic device has a voltage detection step;
The power supply device has an output voltage control step for controlling the output voltage,
When a voltage lower than a predetermined voltage is detected by the voltage detection step, the electronic device and the voltage detection device communicate with each other, and control the output voltage so as to become the predetermined voltage by the output voltage control step. This is a power supply method.

  In this way, even if the internal resistance of the power supply line extending from the AC adapter changes, the predetermined voltage can be corrected based on the internal resistance, so that the predetermined voltage can always be supplied to the electronic device.

  According to the present invention, even when the internal resistance of the power supply line extending from the AC adapter changes while the AC adapter is used, a predetermined voltage can be provided to the electronic device.

  In addition, according to the present invention, a predetermined voltage can be provided to an electronic device even if there are variations in elements constituting the AC adapter and variations in manufacturing.

  Further, according to the present invention, even when the contact resistance of the portion connecting the AC adapter and the electronic device is high, and the voltage supplied to the electronic device is low, the predetermined voltage is reduced. Can be supplied.

It is a characteristic view for demonstrating this invention. It is a block diagram for demonstrating 1st Embodiment to which this invention was applied. It is a block diagram for demonstrating 2nd Embodiment to which this invention was applied. It is a characteristic view for demonstrating 2nd Embodiment to which this invention was applied. It is a basic diagram for demonstrating 2nd Embodiment to which this invention was applied. It is a flowchart for demonstrating 2nd Embodiment to which this invention was applied. It is a characteristic view for demonstrating 3rd Embodiment to which this invention was applied. It is a block diagram for demonstrating 3rd Embodiment to which this invention was applied. It is a characteristic view for demonstrating 3rd Embodiment to which this invention was applied. It is a flowchart for demonstrating 3rd Embodiment to which this invention was applied. It is a characteristic view for demonstrating the other example of 3rd Embodiment to which this invention was applied. It is a characteristic view for demonstrating the other example of 3rd Embodiment to which this invention was applied. It is a characteristic view for demonstrating 4th Embodiment to which this invention was applied. It is a characteristic view for demonstrating 4th Embodiment to which this invention was applied. It is a flowchart for demonstrating 4th Embodiment to which this invention was applied. It is a characteristic view for demonstrating 5th Embodiment to which this invention was applied. It is a circuit diagram for demonstrating an example which changes the voltage output from the AC adapter applied to embodiment of this invention. It is a characteristic view for demonstrating an example which changes the voltage output from the AC adapter applied to embodiment of this invention. It is a circuit diagram for demonstrating the 1st example which changes the voltage output from the AC adapter applied to embodiment of this invention digitally. It is a circuit diagram for demonstrating the 2nd example which changes the voltage output from the AC adapter applied to embodiment of this invention digitally. It is a circuit diagram for demonstrating the 1st example which changes the voltage output from the AC adapter applied to embodiment of this invention analogically. It is a circuit diagram for demonstrating the 2nd example which changes the voltage output from the AC adapter applied to embodiment of this invention analogically. It is a block diagram for demonstrating the conventional AC adapter.

  Embodiments of the present invention will be described below with reference to the drawings. First, in order to facilitate understanding of the present invention, an outline of the present invention will be described with reference to FIG. As an example, FIG. 1 shows a characteristic diagram of voltage and current output from an AC adapter when a secondary battery is charged. A voltage and current that have the characteristic A1 are output from the output terminal of the power supply line of the AC adapter. As an example of the secondary battery, a non-aqueous secondary battery such as a lithium-ion secondary battery or a polymer-lithium secondary battery is used. The non-aqueous secondary battery is first charged with a constant current and then charged with a constant voltage and a minute current. FIG. 1 is a characteristic diagram of voltage and current during charging.

  Here, as an example, when the internal resistance of the power supply line becomes high due to deterioration of the power supply line, the output terminal has the characteristic A2. That is, a voltage that is output near the maximum current output from the AC adapter, for example, current i2 (hereinafter referred to as “maximum current i2”) is supposed to be output (hereinafter referred to as “reference voltage”). ) The voltage v2 is lower than v1 by Δv. Therefore, in this embodiment, when the voltage and current characteristics at the output terminal of the power supply line are the characteristic A2, the voltage and current output from the AC adapter are set to the characteristic A3, whereby the output terminal of the power supply line. , A voltage and a current having the characteristic A1 are supplied.

  A first embodiment to which the present invention is applied will be described with reference to the block diagram of FIG. In FIG. 2, the AC adapter side includes a power supply unit 1, a current detection circuit 2, a resistor 3, a voltage detection circuit 4, a calculation circuit 5, and a control circuit 6, and further includes a power supply line extending from the AC adapter. Internal resistors 7 and 8 are provided. The electronic device side includes a voltage detection circuit 11, a switch circuit 12, a current detection circuit 13, a resistor 14, and a load (hereinafter referred to as “set load”) 15 of the electronic device. The set load 15 includes at least a secondary battery.

  The power supply unit 1 can vary the voltage and current output by the control circuit 6. The positive terminal of the power supply unit 1 is connected to the terminal T 1 via the internal resistor 7, and the negative terminal thereof is connected to the terminal T 2 via the resistor 3 and the internal resistor 8. Internal resistors 7 and 8 indicate the internal resistance of the power supply line extended from the AC adapter, and terminals T1 and T2 indicate the output terminals of the power supply line extended from the AC adapter.

  The current detection circuit 2 is connected to both ends of the resistor 3 and the positive terminal of the power supply unit 1. In the current detection circuit 2, the current output from the terminals T 1 and T 2 is detected, and the detected current is supplied to the calculation circuit 5.

  The voltage detection circuit 4 is connected to the positive terminal of the power supply unit 1 and the connection point of the resistor 3 and the internal resistor 8. In the voltage detection circuit 4, the voltage output from the terminals T 1 and T 2 is detected, and the detected voltage is supplied to the calculation circuit 5.

  As an example, the calculation circuit 5 calculates resistance values obtained by combining the internal resistances 7 and 8 at the currents i1 and i2 shown in FIG. In the calculation circuit 5, the resistance value r1 calculated when the current i1 is a small current, even if the values of the internal resistances 7 and 8 change, suppresses the influence of the voltage drop most, and the original internal resistances 7 and 8 It is calculated as a value approximately equivalent to the value of. In the calculation circuit 5, the resistance value r2 calculated at the maximum current i2 is calculated as a value most reflecting the influence of the voltage drop when the values of the internal resistances 7 and 8 change. The calculated resistance values r1 and r2 are supplied to the control circuit 6.

  In the control circuit 6, it is determined whether or not the supplied resistance values r1 and r2 match. When it is determined that the resistance values r1 and r2 are substantially the same, the voltage output from the power supply unit 1 is continuously output as it is. When it is determined that the resistance values r1 and r2 do not match, the voltage output from the power supply unit 1 is corrected and output so as to have, for example, the characteristic A3 shown in FIG.

  In the electronic device, the voltage detection circuit 11 is provided between the terminals T1 and T2, and the supplied voltage is detected. A switch circuit 12, a set load 15, and a resistor 14 are provided between the terminals T1 and T2. The current detection circuit 13 is connected to both ends of the resistor 14 and a connection point between the switch circuit 12 and the set load 15. In the current detection circuit 13, the current supplied to the set load 15 is detected.

  In the current detection circuit 13, for example, when the maximum current i2 is detected, a signal is supplied to the voltage detection circuit 11. In the voltage detection circuit 11 to which a signal is supplied from the current detection circuit 13, for example, when the voltage v2 is detected, a control signal for turning off the switch circuit 12 is supplied to the switch circuit 12.

  In the voltage detection circuit 11, regardless of the signal from the current detection circuit 13, for example, when the voltage v2 is detected, a control signal for turning off the switch circuit 12 is supplied to the switch circuit 12. Also good.

  Thus, when the value of the internal resistances 7 and 8 of the power supply line increases due to the deterioration of the power supply line extending from the AC adapter, the voltage output from the terminals T1 and T2 decreases. A drop in the voltage output from the terminals T1 and T2 can be detected and the output can be corrected to a predetermined voltage.

  A second embodiment to which the present invention is applied will be described with reference to the block diagram of FIG. In the second embodiment, the voltage supplied from the AC adapter is transmitted to the AC adapter from the electronic device that the voltage v2 is lower than the reference voltage by the voltage Vr on the electronic device side. Further, in the second embodiment shown in FIG. 3, the internal resistances 7 and 8 of the power supply line extending from the AC adapter are shown on the terminal T1 side for easy explanation. This is equivalent to the internal resistor 7 shown on the terminal T1 side and the internal resistor 8 shown on the terminal T2 side.

  A current detection circuit 21 and internal resistors 7 and 8 are provided in series between the positive terminal of the power supply unit 1 and the terminal T1. The negative terminal of the power supply unit 1 is connected to the terminal T2.

  In the current detection circuit 21, the current output from the terminals T1 and T2 is detected. The detected current is supplied from the current detection circuit 21 to the voltage detection circuit 22, the signal reception circuit 23, and the calculation circuit 24, respectively.

  The voltage detection circuit 22 is connected to the connection point between the current detection circuit 21 and the internal resistor 7 and the terminal T2. In the voltage detection circuit 22, the voltage output from the terminals T 1 and T 2 is detected, and the detected voltage is supplied to the calculation circuit 24. The voltage detection circuit 22 may detect the voltage only when the supplied currents become the currents i1 and i2, and supply the detected voltage to the calculation circuit 24.

  The signal receiving circuit 23 receives a signal transmitted from an electronic device connected via terminals T1 and T2, as will be described later. At this time, when a voltage v2 lower than the reference voltage v1 is detected on the electronic device side, a signal is generated and transmitted to the AC adapter. Therefore, by receiving the signal, the voltage supplied from the AC adapter However, on the electronic device side, it can be determined that the voltage is v2. When the signal is received by the signal receiving circuit 23, the signal is supplied from the signal receiving circuit 23 to the calculation circuit 24.

  In the calculation circuit 24, for example, when the currents i1 and i2 shown in FIG. In the calculation circuit 24, the resistance value r1 calculated for the small current i1 suppresses the influence of the voltage drop even when the values of the internal resistances 7 and 8 change, and the original internal resistances 7 and 8 are suppressed. It is calculated as a value approximately equivalent to the value of. In the calculation circuit 24, the resistance value r2 calculated at the maximum current i2 is calculated as a value most reflecting the influence of the voltage drop when the values of the internal resistances 7 and 8 change. The calculated resistance values r1 and r2 are supplied to the control circuit 6.

In addition, when a signal is supplied from the signal receiving circuit 23, it can be determined that the voltage supplied from the AC adapter is the voltage v2 in the electronic device. The value of the internal resistance of the power supply line is calculated from the difference between the supplied voltage Vd and the voltage v2 and the current Id supplied from the current detection circuit 21.
(Vd−v2) / Id = r1 + r2 Formula (1)

The control circuit 25 determines the voltage Vr to be corrected from the voltage Vd supplied from the voltage detection circuit 22 and the voltage v2, and sets the voltage supplied from the AC adapter on the electronic device side as the reference voltage v1. The power supply unit 1 is controlled.
Vd−v2 = Vr Formula (2)

  In the electronic device, the voltage detection circuit 26 is provided between the terminals T1 and T2, and the switch circuit 28 and the set load 15 are provided between the terminals T1 and T2. The voltage detection circuit 26 detects the voltage supplied from the AC adapter. The detected voltage is supplied from the voltage detection circuit 26 to the control circuit 27.

  In the control circuit 27, when the voltage supplied from the voltage detection circuit 26 becomes, for example, the voltage v <b> 2 shown in FIG. 4, a control signal is supplied to the switch circuit 28. In response to a control signal supplied from the control circuit 27, the switch circuit 28 is turned off for a predetermined time, and a signal as shown in FIG. 5A is generated as a current. The generated signal is transmitted to the AC adapter and detected by the signal receiving circuit 23 via the current detection circuit 21.

  Further, by providing a current control circuit 29 indicated by a dotted line, for example, a signal as shown in FIG. 5B may be generated. For example, when the voltage detection circuit 26 detects the voltage v 2, a control signal is supplied from the control circuit 27 to the current control circuit 29. In accordance with the control signal supplied from the control circuit 27, the current control circuit 29 changes the value of the current for a predetermined time to generate a signal as shown in FIG. 5B. The generated signal is transmitted to the AC adapter and detected by the signal receiving circuit 23 via the current detection circuit 21.

  The control of the second embodiment will be described with reference to the flowchart of FIG. In step S1, the AC adapter and the electronic device are connected, and power is supplied from the AC adapter to the electronic device. In step S <b> 2, the current detection circuit 21 detects a current. In step S3, it is determined whether or not the detected current is greater than or equal to current i1. If it is determined that the detected current is equal to or greater than the current i1, the control moves to step S4, and if it is determined that the detected current is less than the current i1, the control returns to step S2.

  In step S4, the voltage detection circuit 26 detects the voltage supplied from the AC adapter. In step S5, it is determined whether or not the detected voltage is equal to or lower than voltage v2. If it is determined that the detected voltage is equal to or lower than the voltage v2, the control shifts to step S6. If it is determined that the detected voltage exceeds the voltage v2, the control returns to step S4.

  In step S6, a signal is generated by the switch circuit 28 or the current control circuit 29 under the control of the control circuit 27, and is transmitted from the electronic device to the AC adapter. In step S7, the current detection circuit 21 detects a current. In step S8, the detected current is supplied to the signal receiving circuit 23, and the signal receiving circuit 23 detects whether or not a signal from the electronic device has been received. If it is determined that a signal from the electronic device has been received, control proceeds to step S9. If it is determined that a signal from the electronic device has not been received, control returns to step S7.

  In step S9, the calculation circuit 24 calculates the above equation (1). In step S10, the control circuit 25 controls the power supply unit 1 based on the above-described formula (2), and the corrected voltage is supplied from the AC adapter to the electronic device.

  A third embodiment to which the present invention is applied will be described with reference to the characteristic diagram of FIG. In the third embodiment, for example, when a signal is not transmitted from an electronic device even if the voltage supplied from the AC adapter is equal to or lower than the voltage v2, the voltage supplied from the AC adapter is increased. At this time, in the third embodiment, the voltage output from the AC adapter is corrected and increased by, for example, the voltage Vr, and a signal is output from the electronic device. For example, the voltage output from the AC adapter is increased as indicated by characteristic A4.

  The third embodiment will be described with reference to the block diagram of FIG. In the current detection circuit 21, a current output from the AC adapter is detected, and the detected current Id is supplied to the voltage detection circuit 22, the signal reception / calculation circuit 31, and the control circuit 32. In the voltage detection circuit 22, the output voltage is detected, and the detected voltage is supplied to the signal reception / calculation circuit 31.

  The signal reception / calculation circuit 31 detects a signal from the current Id supplied from the current detection circuit 21. When a signal is detected, a signal is supplied from the signal reception / calculation circuit 31 to the control circuit 32. In the signal reception / calculation circuit 31, the power supply line extended from the AC adapter based on the current Id supplied from the current detection circuit 21 and the voltage supplied from the voltage detection circuit 22 as described above. The internal resistances r1 and r2 are calculated.

  In the control circuit 32, even when the current detected by the current detection circuit 21 becomes a current value to which a signal is supplied from the electronic device, if the signal is not received, the voltage output from the AC adapter converts the signal from the electronic device. The voltage Vr is corrected higher until reception.

  When this third embodiment is applied to a charger built in an electronic device, the voltage at the maximum current i2 can be set to a voltage close to the charging voltage after constant voltage control.

  Further, when this third embodiment is applied to an AC adapter, variations in the output voltage can be suppressed, and the output voltage can be set to the minimum necessary voltage. Furthermore, since the heat generation of the charging circuit incorporated in the electronic device can be suppressed, the charging circuit can be reduced in size.

  In the third embodiment, the voltage output from the AC adapter is increased digitally at predetermined time intervals as indicated by the solid line in FIG. 9, but as indicated by the broken line in FIG. The voltage output from the AC adapter in an analog manner may be increased.

  The third embodiment will be described with reference to the flowchart of FIG. In step S11, the AC adapter operates. In step S12, the current detection circuit 21 detects a current. In step S13, it is determined whether or not the detected current is a prescribed current so that a signal is supplied from the electronic device. If it is determined that the detected current is the specified current, the control moves to step S14, and if it is determined that the detected current is not the specified current, the control returns to step S12.

  In step S <b> 14, the signal reception / calculation circuit 31 receives a signal. In step S15, when it is determined that the signal is received by the signal reception / calculation circuit 31, the control shifts to step S17, and when it is determined that the signal reception / calculation circuit 31 does not receive a signal, the control proceeds to step S16. Move. In step S16, as shown in FIG. 9, it correct | amends so that the voltage output by the voltage Vr may become high. Then, control returns to step S14. In step S17, the flowchart shown in FIG. 6 is called. When the control of the called flowchart ends, the control returns from step S17 to step S12.

  Another example of the third embodiment will be described with reference to the characteristic diagrams of FIGS. When the current detected by the current detection circuit 21 is, for example, the current i3 shown in FIG. 11, the signal reception / calculation circuit 31 receives a signal transmitted from the electronic device. In 26, the voltage v2 lower than the reference voltage v1 by the voltage Vr is detected.

  As described above, when the signal output from the electronic device is received even though the current output from the AC adapter is a small value, the voltage output from the AC adapter is reduced by correcting the voltage Vr, for example, as shown in FIG. Then, when the signal from the electronic device is not received, the voltage output from the AC adapter is stopped from being lowered, and the voltage at that time is supplied to the electronic device.

  As described above, when the voltage output from the AC adapter is high, a signal is transmitted from the electronic device regardless of the magnitude of the current. Therefore, as shown in FIG. 12, the voltage output from the AC adapter is lowered.

  Note that the voltage output from the AC adapter is digitally lowered at predetermined time intervals as shown by the solid line in FIG. 12, but it is analogized from the AC adapter as shown by the broken line in FIG. The output voltage may be lowered.

  A fourth embodiment to which the present invention is applied will be described with reference to FIGS. 13 and 14. In the fourth embodiment, the voltage output from the AC adapter is changed every predetermined time as shown in FIG. In this way, it is confirmed that a signal is transmitted from the electronic device by reducing the voltage supplied from the AC adapter to the electronic device every predetermined time.

  If a signal is not transmitted from the electronic device when a low voltage at the predetermined time is output from the AC adapter, it is determined that the voltage detected by the voltage detection circuit 26 of the electronic device is lower than the voltage v2, As shown in FIG. 14, a voltage higher than the voltage currently output from the AC adapter by a voltage Vr is supplied to the electronic device.

  In addition, when the electric current more than the electric current i4 in FIG. 14 is output from an AC adapter, as shown in FIG. 13, the voltage output from an AC adapter can be changed.

  Here, the fourth embodiment will be described with reference to the flowchart of FIG. In step S21, the AC adapter and the electronic device are connected, and power is supplied from the AC adapter to the electronic device. In step S22, the current output from the AC adapter is detected by the current detection circuit 21.

  In step S23, it is determined whether or not the detected current is equal to or greater than a set current i4. If it is determined that the detected current is greater than or equal to current i4, control is transferred to step S24, and if it is determined that the detected current is less than current i4, control is returned to step S22.

  In step S24, a timer operation is started. In step S25, it is determined whether or not a predetermined time has been reached. If it is determined that the predetermined time has been reached, control is passed to step S26, and if it is determined that the predetermined time has not yet been reached, control is returned to step S24.

  In step S26, the signal reception / calculation circuit 31 receives the signal. In step S27, if it is determined that the signal is received by the signal reception / calculation circuit 31, control is transferred to step S24. Move. In step S28, as shown in FIG. 9, it correct | amends so that the voltage output by the voltage Vr may become high. Then, control returns to step S22.

  A fifth embodiment to which the present invention is applied will be described with reference to the characteristic diagram of FIG. In the fifth embodiment, the current for detecting the internal resistance of the power supply line is detected not by the maximum current i2 output from the AC adapter but by the current i5 that is lower than the maximum current i2. .

Based on the value detected by the current i5, correction is performed assuming the maximum current i2. Since the value of the internal resistance of the power supply line does not change depending on the current, for example, the voltage Vr2 can be calculated from Equation (3), and the voltage output from the AC adapter can be corrected.
Vr5 / i5 = Vr2 / i2 = r1 + r2 Formula (3)

  As an example, when the voltage Vr5 when the current i5 = 0.5A is 0.5V, and the current i2 = 1A, the voltage Vr2 = 1.0V.

  The current i5 is preferably set at a position where the difference from the maximum current i2 becomes small because the voltage decreases as the difference from the maximum current i2 increases.

Further, the voltage Vr5 can be calculated from the voltage V22 detected by the voltage detection circuit 22 and the voltage V26 detected by the voltage detection circuit 26 as shown in Expression (4).
(V22−V26) = Vr5 Formula (5)

  An example of changing the voltage output from the AC adapter to which the above-described embodiment is applied will be described with reference to the circuit diagram of FIG. Although not shown, the primary winding 41a of the transformer 41 is rectified and supplied with controlled commercial power. A current based on the duty ratio is supplied to the primary winding 41a, and an induced voltage is generated in the secondary winding 41b. A diode 42 and a capacitor 43 for rectifying the output induced power are connected to the secondary winding 41b.

  A cold line Lc serving as a reference for the voltage output from the AC adapter is derived from a connection point between the secondary winding 41 b and the capacitor 43. A hot line Lh having a predetermined potential difference is derived from the cold line Lc from the connection point of the diode 42 and the capacitor 43.

  Resistors 44 and 45 are inserted in series between the hot line Lh and the cold line Lc. One input terminal of the operational amplifier circuit 46 is connected to the connection point of the resistors 44 and 45, and the other input terminal is connected to the cathode of the constant voltage diode 47. The output of the operational amplifier circuit 46 is supplied to the control feedback circuit 54. The anode of the constant voltage diode 47 is connected to the cold line Lc.

  The operational amplifier circuit 46 detects a signal for making the voltage output from the AC adapter a constant voltage. As an example, a signal output from the operational amplifier circuit 46 is shown in FIG. 18B.

  A resistor 48 is inserted in the cold line Lc. Two input terminals of the operational amplifier circuit 49 are connected to both ends of the resistor 48. The output of the operational amplifier circuit 49 is supplied to the control feedback circuit 54.

  In the operational amplifier circuit 49, a signal for making the current output from the AC adapter a constant current is detected. As an example, FIG. 18C shows a signal output from the operational amplifier circuit 49.

  The resistors 50 and 51 are provided in parallel with the resistor 48. Two input terminals of the operational amplifier circuit 52 are connected to both ends of the resistor 51. The output terminal of the operational amplifier circuit 52 is connected to the connection point of the resistors 44 and 45 via the resistor 53.

  The operational amplifier circuit 52 detects a voltage to be corrected based on the detected current. That is, in the operational amplifier circuit 52, when the internal resistance of the power supply line changes, a signal for changing the magnitude of the voltage to be corrected is output. As an example, FIG. 18D shows a signal output from the operational amplifier circuit 52.

  18A shows the voltage and current output from the AC adapter, and FIG. 19E shows the signal output from the control feedback circuit 54. Based on the signal shown in FIG. 19E, the duty ratio supplied to the primary winding 41a is controlled.

  A first example in which a voltage output from an AC adapter applied to this embodiment is digitally changed will be described with reference to the circuit diagram of FIG. Resistors 61, 62, 63, and 64 are inserted in series between the hot line Lh and the cold line Lc. The cathode of the constant voltage diode 47 is connected to the connection point of the resistors 61 and 62.

  A terminal 65 a of the switch circuit 65 is connected to a connection point between the resistors 61 and 62. Terminal 65 b of switch circuit 65 is connected to the connection point of resistors 62 and 63. A terminal 65 c of the switch circuit 65 is connected to a connection point between the resistors 63 and 64. The output terminal of the switch circuit 65 is connected to the other input terminal of the operational amplifier circuit 46.

  The switch circuit 65 is controlled by the control circuit 66, and any one of the terminals 65a, 65b, and 65c is selected. The output terminal of the operational amplifier circuit 46 is connected to the cold line Lc via the resistor 67 and to the control feedback circuit 54.

  With reference to the circuit diagram of FIG. 20, a second example in which the voltage output from the AC adapter applied to this embodiment is digitally changed will be described. Resistors 71, 72, 73, and 74 are inserted in series between the output terminal of the operational amplifier circuit 46 and the cold line Lc.

  The terminal 75 a of the switch circuit 75 is connected to the output terminal of the operational amplifier circuit 46. A terminal 75 b of the switch circuit 75 is connected to a connection point between the resistors 71 and 72. A terminal 75 c of the switch circuit 75 is connected to a connection point between the resistors 72 and 73. A terminal 75 d of the switch circuit 75 is connected to a connection point between the resistors 73 and 74. An output terminal of the switch circuit 75 is connected to the control feedback circuit 54.

  The switch circuit 75 is controlled by the control circuit 76, and any one of the terminals 75a, 75b, 75c, and 75d is selected.

  Thus, by switching the switch circuits 65 and 75 by the control circuits 66 and 76, the voltage output from the AC adapter can be changed digitally as shown by the solid line in FIG. 9 and FIG. In the first and second examples shown in FIGS. 19 and 20, the voltage output from the AC adapter can be increased and decreased depending on the direction in which the switch circuits 65 and 75 are switched.

  A first example in which the voltage output from the AC adapter applied to this embodiment is changed in an analog manner will be described with reference to the circuit diagram of FIG. The collector of the NPN transistor 82 is connected to the hot line Lh via resistors 44 and 81. The emitter of the transistor 82 is connected to the cold line Lc through the resistor 83. The base of the transistor 82 is connected to the control circuit 84.

  In this way, by controlling the transistor 82 with the control circuit 84, the voltage output from the AC adapter can be changed in an analog manner as indicated by a broken line in FIG.

  A second example in which the voltage output from the AC adapter applied to this embodiment is changed in an analog manner will be described with reference to the circuit diagram of FIG. The emitter of the PNP transistor 92 is connected to the hot line Lh via the resistor 91. The collector of the transistor 92 is connected to one input terminal of the operational amplifier circuit 46 through the resistor 93. The base of the transistor 92 is connected to the control circuit 94.

  In this way, by controlling the transistor 92 by the control circuit 94, the voltage output from the AC adapter can be changed in an analog manner as indicated by a broken line in FIG.

  The present invention is not limited to the above-described embodiment of the present invention, and various modifications and applications are possible without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 1 Power supply part 2, 13 Current detection circuit 3, 14 Resistance 4, 11 Voltage detection circuit 5 Calculation circuit 6 Control circuit 7, 8 Internal resistance 12 Switch circuit 15 Load of electronic equipment

Claims (12)

In a power supply device that supplies a predetermined voltage and current to an electronic device,
The electronic device has voltage detection means,
The power supply device has an output voltage control means for controlling an output voltage,
When the voltage detection means detects a voltage lower than the predetermined voltage, the electronic device and the voltage detection means communicate with each other, and the output voltage control means controls the output voltage so as to become a predetermined voltage. A power supply device characterized by that.   The power supply apparatus according to claim 1, wherein the power supply apparatus includes a signal reception unit that receives a signal from the electronic device.   When a voltage lower than the predetermined voltage by a first voltage is detected, the control means increases the output voltage by the first voltage when the signal receiving means receives a signal. The power supply device according to claim 2, wherein the power supply device is a power supply device. In the control means,
3. The output voltage is sequentially increased at predetermined time intervals in steps of the first voltage until a signal supplied from the electronic device is detected by the signal receiving means. The power supply device described in 1. In the control means,
If the signal supplied from the electronic device is not detected by the signal receiving means even when the output voltage is increased, the signal receiving means detects the signal supplied from the electronic device at predetermined time intervals until the signal receiving means detects the signal. 3. The power supply apparatus according to claim 2, wherein the output voltage is sequentially decreased in steps corresponding to the first voltage.   3. The power supply apparatus according to claim 2, wherein the output voltage is made lower than the predetermined voltage at predetermined time intervals, and a signal supplied from the electronic device is detected by the signal receiving means. In a power supply method for supplying a predetermined voltage and current from a power supply device to an electronic device,
The electronic device has a voltage detection step,
The power supply device has an output voltage control step for controlling an output voltage,
When the voltage detection step detects a voltage lower than the predetermined voltage, the electronic device and the voltage detection device communicate with each other, and the output voltage control step controls the output voltage to be a predetermined voltage. A power supply method characterized by:   The power supply method according to claim 7, wherein the power supply device includes a signal reception step of receiving a signal from the electronic device.   When a voltage lower than the predetermined voltage by a first voltage is detected, the control step increases the output voltage by the first voltage when the signal reception step receives a signal. The power supply method according to claim 8, wherein: In the control step,
9. The output voltage is sequentially increased in steps of the first voltage at predetermined time intervals until a signal supplied from the electronic device is detected in the signal reception step. The power supply method described in 1. In the control step,
If the signal supplied from the electronic device is not detected in the signal receiving step even when the output voltage is increased, the signal supplied from the electronic device is detected at predetermined time intervals until detected in the signal receiving step. The power supply method according to claim 8, wherein the output voltage is sequentially decreased in steps corresponding to the first voltage.   9. The power supply method according to claim 8, wherein the output voltage is made lower than the predetermined voltage at predetermined time intervals, and a signal supplied from the electronic device is detected in the signal receiving step.

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