JP2007014064A - Electronic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electronic apparatus which can charge a charging means with power efficiently while preventing the output voltage drop of a power source, relating to an electronic apparatus which converts the power of a power source with a DC-DC converter and charges an accumulating means with it and drives a load circuit with power accumulated in the above accumulating means. <P>SOLUTION: A transistor is provided between the accumulating means and the load circuit and the current flowing to the accumulating means, and the load circuit is controlled with the voltage of the power source connected to the gate of the transistor. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electronic device that drives a circuit with power from a power source such as a solar cell, a thermoelectric conversion element, or a fuel cell having a high internal resistance.

  FIG. 5 shows a block diagram of an electronic device that drives a circuit with electric power such as a conventional solar cell (see, for example, Patent Document 1).

  5 includes a power source 101 that supplies power, a DC-DC converter 102 that boosts the power supplied from the power source 101, and a storage unit 104 that stores the power output from the DC-DC converter 102. And a load circuit 103. The output terminal of the power supply 101 is connected to the input terminal of the DC-DC converter 102, and the output terminal of the DC-DC converter 102 is connected to the power supply terminal of the power storage means 104 and the power supply terminal of the load circuit 103. The power supply 101, the DC-DC converter 102, the power storage means 104, and the ground terminal of the load circuit 103 are commonly grounded.

  In the conventional electronic device as shown in FIG. 5, when the amount of electric charge stored in the power storage means is insufficient, the DC-DC converter starts operation with the maximum output. At this time, if the internal resistance of the power supply is high, the power supply voltage suddenly drops, and the DC-DC converter tries to extract more current from the power supply. For this reason, the power supply voltage drops, and it becomes difficult to maintain the operation of the DC-DC converter.

  FIG. 6 shows a block diagram of another conventional electronic device that solves such a problem (see, for example, Patent Document 2).

  6 includes a power supply 101 that supplies power, a DC-DC converter 102 that boosts the power supplied from the power supply 101, and an auxiliary device that stores the power output from the DC-DC converter 102. Power storage means 107, power storage means 104 that stores power output from DC-DC converter 102, switch 106 that sends power from auxiliary power storage means 107 to power storage means 104, voltage of auxiliary power storage means 107, and power storage means 104 A control circuit 105 that detects a voltage and outputs a control signal to the switch 106 and a load circuit 103 that is driven by electric power stored in the power storage means 104 are provided. The output terminal of the power supply 101 is connected to the input terminal of the DC-DC converter 102, and the output terminal of the DC-DC converter 102 is connected to the input terminal of the switch 106, the power supply terminal of the auxiliary power storage means 107, and the voltage detection terminal 1 of the control circuit 105. The output terminal of the switch 106 is connected to the power supply terminal of the power storage means 104, the power supply terminal of the load circuit 103, and the voltage detection terminal of the control circuit 105. In addition, the power supply 101, the DC-DC converter 102, the control circuit 105, the load circuit 103, the auxiliary power storage means 107, and the ground terminals of the power storage means 104 are configured to be grounded in common.

That is, the power storage means 104 having a large capacity is disconnected from the output of the DC-DC converter 102 by the switch 106 and the auxiliary power storage means 107 is connected to the output of the DC-DC converter 102. However, the capacity of the auxiliary power storage means 107 had to be set to a capacity value that can maintain the operation of the DC-DC converter 102 even when a voltage drop occurs in the power supply 101.
JP 2003-204072 A JP 2001-298862 A

  In the conventional electronic device as shown in FIG. 5, since the power storage means and the load circuit are directly connected, the voltage of the power storage means gradually rises after the supply of power from the power source is started, so that the load circuit is indefinitely operated. It may become a state (malfunction state). At this time, if the load circuit includes a circuit that requires a large amount of power, such as a circuit that drives a motor or a circuit that generates sound, a large amount of through current flows. Once the through current flows, the voltage of the power storage means drops, and even when power is supplied from the power source, the voltage in a state where the load circuit becomes indefinite is held. Here, unless the power supply capability of the power supply exceeds the through current, the voltage of the power storage means does not increase and the load circuit does not operate. Further, even when the voltage of the power storage means becomes equal to or higher than the voltage band where the operation of the load circuit is indefinite, the load circuit and the power storage means are directly connected, so that the load circuit operates. This is particularly noticeable when a power generation source such as a solar cell is used as the power source. In a system using a power generation source such as a solar cell, it is necessary to store more power when light is irradiated and to cope with a sudden load. However, in the conventional electronic device, since the power storage means and the load circuit are directly connected, power is consumed by the load circuit, and electric charge cannot be stored in the power storage means.

  In addition, when a DC-DC converter is used in the load circuit, there may be a mechanism that allows more current to flow when the power supply voltage is low. At this time, in the conventional electronic device, when the supply of power from the power source is started, the voltage of the power storage means gradually increases, so that a large amount of current flows through the load circuit when the voltage is low. For this reason, the voltage of the power storage means causes a voltage drop, and there is a disadvantage that the voltage does not increase.

  In the electronic device as shown in FIG. 6, the control circuit 105 needs to detect and compare the voltages of both the auxiliary power storage means 107 and the power storage means 104 to control the switch 106. The control circuit 105 is designed for the system. I had to.

  Furthermore, since two power storage means, that is, the auxiliary power storage means 107 and the power storage means 104 are required, there is a problem in applying to a small portable device.

  The present invention has been made in view of the inconveniences of the related art, and in the case of charging power to a large power storage unit, an electronic device capable of efficiently storing electric charge in the power storage unit while preventing an output voltage drop of a power source is provided. It is intended to provide.

  In order to solve the above-described problems, the present invention provides an electronic device whose power source is a power source with high internal resistance such as a fuel cell, wherein a transistor is provided between the power storage unit and the load circuit and the ground terminal, and the power storage unit and the load circuit are provided. The flowing current is controlled by the voltage of the power source connected to the gate of the transistor.

  According to the electronic apparatus of the present invention, the power source and the DC-DC converter can stably output power, and the load circuit can be stably driven even when the power is turned on. Furthermore, the entire system can be reduced in size. In particular, it is effective for an electronic device driven by a power source having a large internal resistance, for example, a lithium secondary battery, a solar cell, a thermal generator, a fuel cell, or the like.

  FIG. 1 is a block diagram of an electronic apparatus according to a first embodiment of the present invention. The electronic apparatus according to the first embodiment includes a power source 1, a DC-DC converter 2, a power storage unit 4, a transistor 5, and a load circuit 3.

  The output terminal of the power supply 1 is connected to the input terminal of the DC-DC converter 2 and the gate of the transistor 5, and the output terminal of the DC-DC converter 2 is connected to the first terminal of the storage means 4 and the power supply terminal of the load circuit 3. The second terminal of the power storage means 4 and the drain of the transistor 5 are connected. Here, the ground terminal of the power source 1, the ground terminal of the DC-DC converter 2, and the source of the transistor 5 are connected to the first GND, the ground terminal of the load circuit 3, the drain of the transistor 5, and the second of the storage means 4. Connect the terminal to the second GND.

  In the present invention, the DC-DC converter 2 may be a DC-DC converter of a type that boosts using a self-induced current of a coil generated by turning on and off a current flowing through the coil by a switching element, and a switched capacitor. A DC-DC converter of a system may be used. Furthermore, when the output voltage of the power supply 1 is sufficiently high, a step-down DC-DC converter may be used, or both may be used in combination.

  FIG. 3 shows a circuit block diagram of a switching type step-up DC-DC converter as an example. The DC-DC converter includes a coil 10, a diode 11, a transistor 12, an output control circuit 13, and a capacitor 14. The input terminal 15 is connected to one terminal of the coil 10, and the other terminal of the coil is connected to the anode of the diode 11 and the drain of the transistor 12. The cathode of the diode 11 is connected to the power supply terminal and output monitor terminal of the output control circuit 13, one pole of the capacitor 14, and the output terminal 16 of the DC-DC converter 2. Then, the source of the transistor 12, the ground terminal of the output control circuit 13, and the other terminal of the capacitor 14 are connected to serve as the ground terminal of the DC-DC converter.

  The operation of the DC-DC converter shown in FIG. 3 is performed by inputting the pulse signal generated by the output control circuit 13 to the gate electrode of the transistor 12 and switching the transistor to boost the power flowing through the coil 10 to the output terminal 16. Is output. The output control circuit 13 monitors the voltage at the output terminal 16 at the output monitor terminal and adjusts the switching of the transistor.

  The power storage unit 4 has a role of storing output power of the DC-DC converter 2 and supplying power to the load circuit 3. As the power storage means, for example, a lithium secondary battery or an electric double layer capacitor is used.

  The transistor 5 adjusts the current flowing between the source and the drain in accordance with the output voltage of the power supply 1. Here, the threshold voltage of the transistor 5 is adjusted according to the output characteristics of the power source 1. By connecting the transistor 5 to the power storage means 4, the amount of current entering the power storage means 4 can be adjusted according to the output voltage of the power source 1. For example, when the output voltage of the power source 1 is always 1 V or higher, the voltage is adjusted to about 0.7 V, and when the output voltage of the power source 1 is about 0.5 V, the voltage is adjusted to about 0.2 V. Therefore, the transistor 5 can adjust the amount of current entering the power storage means 4 according to the output voltage of the power source 1.

  The load circuit 3 includes a power supply IC such as a DC-DC converter in addition to a general application circuit.

  Next, the operation of the electronic apparatus of the first embodiment shown in FIG. 1 will be described.

  The output power of the power source 1 is boosted by the DC-DC converter 2 and stored in the power storage means 4. When the power storage means 4 is charged to some extent, the DC-DC converter 2 does not draw current from the power source 1 beyond the power supply capability of the power source 1. When the power storage means 4 is completely discharged, the output of the DC-DC converter 2 is pulled by the voltage of the power storage means 4, so that the DC-DC converter 2 exceeds the power supply capability of the power source 1 to draw current. And Here, since the transistor 5 whose gate is connected to the output of the power source 1 is connected between the power storage unit 4 and the ground terminal, the power that the transistor 5 flows into the power storage unit 4 in accordance with the output voltage of the power source 1 is obtained. Can be controlled. As a result, the DC-DC converter 2 can maintain the boosting operation without lowering the output voltage of the power source 1.

  That is, since the output voltage of the power supply 1 is controlled so as not to be lower than the threshold voltage of the transistor 5, the threshold voltage of the transistor 5 is set in accordance with the capability of the power supply 1, thereby Regardless, the output of the power source 1 can be boosted by the DC-DC converter 2 and can be efficiently stored in the power storage means 4.

  With such a circuit configuration, since the load circuit 3 is driven by the power storage means 4 and the transistor 5 connected in series, the impedance viewed from the load circuit 3 is increased by the impedance of the transistor 5. As a circuit configuration as shown in FIG. 1, this can be solved by connecting the load circuit 3 to a second ground terminal different from the transistor 5 and directly driving it by the power storage means 4.

  According to the present invention as described above, the output voltage of the power source 1 does not drop rapidly even when no charge is stored in the power storage means 4 without adding a complicated control circuit. 4 can stably store electric power.

  FIG. 2 is a block diagram of an electronic apparatus according to the second embodiment of the present invention. The electronic device according to the second embodiment includes a power source 1, a DC-DC converter 2, a power storage unit 4, a transistor 5, a control circuit 6, a switch 7, and a load circuit 3.

  The output terminal of the power source 1 is connected to the input terminal of the DC-DC converter 2 and the gate of the transistor 5. The output terminal of the DC-DC converter 2 is connected to the detection terminal of the control circuit 6, the first terminal of the storage means 4, and the switch 7. Are connected to each other, the control terminal of the control circuit 6 is connected to the control terminal of the switch 7, the other terminal of the switch 7 is connected to the power supply terminal of the load circuit 3, and the second terminal of the power storage means 4 is connected to the transistor 5. Connect the drain. Here, the ground terminal of the power source 1, the ground terminal of the DC-DC converter 2, and the source of the transistor 5 are connected to the first GND, the ground terminal of the load circuit 3, the control circuit 6, the switch 7, the drain of the transistor 5, The second terminal of the power storage means 4 is connected to the second GND.

  The control circuit 6 monitors the voltage of the power storage means 4 at the detection terminal, and when the voltage of the power storage means 4 reaches a preset voltage, sends a signal to the switch 7 to turn on the switch 7. A circuit block diagram of an example of the control circuit 6 is shown in FIG. The control circuit 6 includes resistors 21 and 22 connected between the detection terminal 27 and the ground terminal 29, a comparator circuit 24 in which a connection point between the resistors 21 and 22 is connected to an input terminal, and the other input of the comparator circuit 24. A constant voltage output circuit 23 connected to the terminal, a delay circuit 25 connected to the output terminal of the comparator circuit 24, and an inverter circuit 26 connected to the output terminal of the delay circuit 25. The output terminal of the inverter circuit 26 is connected to the control terminal 28 of the control circuit 6, and the ground terminal of each element is connected to the ground terminal 29 of the control circuit 3.

  The control circuit 6 sends a signal obtained as a result of comparing the voltage obtained by dividing the voltage of the detection terminal 27 by the resistors 21 and 22 with the voltage of the constant voltage output circuit 23 in the comparator circuit 24 via the delay circuit 25 and the inverter circuit 26. Output from the control terminal 28 of the control circuit 6.

  The switch 7 is provided between the power storage unit 4 and the load circuit 3 and is turned on / off by a signal from the control circuit 6 to control power supply to the load circuit 3.

  Next, the operation of the electronic device of the second embodiment shown in FIG. 2 will be described.

  The output power of the power source 1 is boosted by the DC-DC converter 2 and stored in the power storage means 4. Here, since the transistor 5 is connected to the power storage means 4, the power flowing into the power storage means 4 can be controlled by causing the transistor 5 to flow a current according to the output voltage of the power supply 1.

  Next, when the voltage of the storage means 4 reaches a voltage value preset in the control circuit 6, the control circuit 6 outputs a signal from the control terminal to the control terminal of the switch 7. Upon receiving the control signal, the switch 7 is turned on, and the power of the power storage unit 4 is output to the load circuit 3. When the voltage of the storage means 4 becomes equal to or lower than the voltage value preset in the control circuit 6, the control circuit 6 sends a signal from the control terminal to the control terminal of the switch 7, and turns off the switch 7. Once the power storage unit 4 and the load circuit 3 are disconnected, the power storage unit 4 does not supply power to the load circuit 3 unless the voltage of the power storage unit 4 again exceeds a predetermined voltage value.

  By configuring as described above, the same effect as that of the first embodiment can be obtained, and the power source and the DC-DC converter can be stably operated without using the auxiliary power storage means as in the conventional electronic device. In addition, since the control circuit only needs to monitor the voltage of one power storage means, it can be performed with a general-purpose voltage detector, so that it is possible to provide an electronic device suitable for a small portable device. .

It is a block diagram of the electronic device of the 1st Example of this invention. It is a block diagram of the electronic device of the 2nd Example of this invention. It is a block diagram which shows an example of the DC-DC converter of the electronic device of this invention. It is a block diagram which shows an example of the control circuit of the electronic device of this invention. It is a block diagram of the conventional electronic device. It is a block diagram of the conventional electronic device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,101 Power supply 2,102 DC-DC converter 3,103 Load circuit 6,105 Control circuit 7,106 Switch 13 Output control circuit 23 Constant voltage output circuit 25 Delay circuit

Claims (7)

In an electronic device comprising a power source, a DC-DC converter connected to the power source, a power storage means connected to the output of the DC-DC converter, and a load circuit driven by the power of the power storage means,
An electronic device in which a transistor is provided between the power storage means and a ground terminal, and a gate of the transistor is connected to a connection point between the power source and the DC-DC converter.   The electronic device according to claim 1, wherein a ground terminal of the power storage unit and the load circuit is connected to a second ground terminal.   The electronic device according to claim 1, wherein the power source is a power source having a high internal resistance, such as a solar cell, a thermoelectric conversion element, or a fuel cell. A power supply, a DC-DC converter connected to the power supply, a control circuit connected to the DC-DC converter, a power storage means connected to the DC-DC converter, and a load circuit driven by the power of the power storage means In an electronic device in which the control circuit controls on / off of a switch provided between a connection point between the DC-DC converter and the power storage means and the load circuit,
An electronic device in which a transistor is provided between the power storage means and a ground terminal, and a gate of the transistor is connected to a connection point between the power source and the DC-DC converter.   The electronic device according to claim 4, wherein a ground terminal of the power storage unit, the load circuit, the control circuit, and the switch is connected to a second ground terminal.   The electronic device according to claim 4, wherein the power source is a power source having a high internal resistance, such as a solar cell, a thermoelectric conversion element, or a fuel cell. In the electronic device that converts the power of the power source with a DC-DC converter and charges the power storage means, and drives the load circuit with the power stored in the power storage means,
An electronic device in which a transistor is provided between the power storage unit and a ground terminal, and a current flowing through the power storage unit is controlled by a voltage of the power source connected to a gate of the transistor.

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