JP2005102440A - Power supply system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small and highly efficient power supply system capable of driving a load even when a power generating means having an output voltage lower than an actuating voltage of a step-up circuit is employed. <P>SOLUTION: The power supply system comprises a power generating section 10, a first step-up circuit 20 for converting generated power into first step-up power having a voltage higher than that of the generated power, and a second step-up circuit 30 for converting the generated power into second step-up power having a voltage higher than that of the generated power, and drives a load by the first step-up power. The first step-up circuit 20 is actuated by the second step-up power. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a power supply system for small electronic devices such as a mobile phone and a notebook computer.

  Conventionally, when the load does not operate because the output voltage of the power generating means is lower than the minimum operating voltage of the load, a booster circuit is connected to the power generating means in order to obtain the operating voltage of the load. Particularly in the power generation means having a high internal resistance, when the current is taken out, the output voltage is extremely lowered and often falls below the minimum operating voltage of the load. Therefore, the booster circuit is also effective for such power generation means.

  A schematic block diagram of a conventional power supply system is shown in FIG. In this conventional example, the fuel cell 11 is used in the power generation unit as an example of power generation means having a high internal resistance. As shown in FIG. 4, the fuel cell 11 that outputs power, the load 130 that performs a desired function, the secondary battery 12 that stores the power of the fuel cell 11, and the secondary battery 12 of the power of the fuel cell 11 Charging control means 61 for controlling the charging of the battery, a power conversion device 21 for converting the power of the fuel cell 11 and the stored power of the secondary battery 12 into power that can operate the load 130, and the stored power of the secondary battery 12 as power. Provided in a path for supplying power to the conversion device 21, and controls the supply of the stored electric power of the diode element 50 and the secondary battery 12 to the power conversion device 21, which prevents backflow of current from the power conversion device 21 to the secondary battery 12. And switch 120. In addition, since the voltage of the fuel cell 11 and the secondary battery 12 often differs in the charge control means 61, a DC-DC converter is used.

With the above configuration, even when the output voltage of the fuel cell 11 is lower than the minimum drive voltage of the load 130, the load 130 can be driven by being boosted by the power converter 21, and at the same time, the power of the fuel cell 11 is When the power is higher than the power required for driving the battery, the charging control means 61 charges the secondary battery 12 with the surplus power of the fuel cell 11, and the power of the secondary battery 12 is less than the power required for driving the load 130. In this case, the insufficient power can be supplemented by the stored power of the secondary battery 12 (see, for example, Patent Document 1).
JP 2002-315224 (page 2-3, FIG. 3)

  However, there are power generation means and conditions in which a voltage for starting up a booster circuit such as a power converter or a charge control means cannot be obtained. For example, the open circuit voltage of the power generation means is low, or when the starting current of the booster circuit is taken out from the power generation means, the internal impedance is extremely high, so that the voltage drops. In that case, since the booster circuit does not move, the load cannot be driven, and the power supply system becomes useless at all.

  The starting voltage of the booster circuit is determined by the threshold value of the switch element normally used in the booster circuit. Therefore, it is possible to lower this threshold and lower the minimum starting voltage. However, in this case, the leakage current increases and the efficiency decreases, that is, the efficiency of transferring the output power of the power generation means to the load decreases. In order to generate the power required by the load, it is necessary to enlarge the power generation means. Therefore, according to the above measures, the volume cannot be applied to a small electronic device, and the weight becomes heavy. Therefore, the measures cannot be actually used.

  The present invention relates to a power supply system to which a booster circuit is applied to drive a load, and can drive the load even when using a power generation means whose output voltage is lower than the starting voltage of the booster circuit. An object is to provide a highly efficient power supply system.

  In order to solve the above-described problems, in the present invention, a power generation unit that generates generated power, a first booster circuit that converts the generated power into first boosted power having a voltage higher than the voltage of the generated power, and A second booster circuit for converting the generated power into a second boosted power having a voltage higher than the voltage of the generated power, and a power supply system for driving a load with the first boosted power, The first booster circuit is activated by using the boosted power of 1.

  As a result, the first booster circuit can be driven without lowering the minimum starting voltage of the first booster circuit. As described above, it is possible to lower the minimum starting voltage of the first booster circuit by lowering the threshold value of the switch element used in the first booster circuit. However, this causes a leakage current and wastes the electric power generated in the power generation unit.

  According to this solution, since the efficiency of the first booster circuit does not decrease, the output power of the power generation unit can be used for the load with high efficiency. Therefore, it is not necessary to increase the volume of the power generation unit.

  More preferably, the second booster circuit is connected to the input terminal and the power supply terminal of the first booster circuit to boost the power generated by the power generation unit.

  As a result, the first booster circuit is driven by the output power of the power generation unit, and the first booster circuit has a small capacity for supplying power for starting the first booster circuit. It becomes possible to incorporate it with a circuit and a control circuit. Therefore, the volume of the circuit portion can be further reduced.

  The first booster circuit continues to operate with the first boosted power supplied via the rectifier circuit, and detects a voltage of the first boosted power supplied via the rectifier circuit. And the second booster circuit is stopped when the first boosted power supplied via the rectifier circuit is equal to or higher than a desired voltage.

  In the present invention, a structure in which the output voltage of the first booster circuit is returned to the power supply terminal of the first booster circuit is preferable.

  As a result, after the first booster circuit is activated, the circuit can be continuously driven with the output voltage of the first booster circuit. When this means is not used, it is necessary to always drive the second booster circuit and supply power for driving the first booster circuit. On the other hand, in this means, the second booster circuit may be used only at the time of starting the first booster circuit, and the capacity and size of the second booster circuit can be reduced. Therefore, since the second booster circuit can be made small by the means of this solution, the power supply system can be miniaturized.

  However, in this structure, the power of the power generation unit is supplied to the load via the second booster circuit. Further, when the first booster circuit is activated, the power flowing from the second booster circuit to the first booster circuit is reduced due to the influence of the load. In order to compensate for such power loss, it is necessary to improve the output of the power generation unit or the capacity of the second booster circuit. Therefore, these lead to an increase in the size of the power generation unit or the second booster circuit.

  Therefore, the rectifier circuit of this means can prevent the power of the power generation unit from flowing to the load via the second booster circuit. Therefore, when the first booster circuit is started, the output power of the second booster circuit can be used only for starting the first booster circuit. Further, when the first booster circuit is activated, it is possible to prevent the power flowing from the second booster circuit to the first booster circuit from being reduced due to the influence of the load. That is, the output power of the power generation unit can be efficiently used for starting the first booster circuit, and can be used to efficiently drive the load via the first booster circuit. As described above, the second booster circuit can be further reduced, and the power supply system can be made compact.

  A diode element, preferably a Schottky diode is preferably used for the rectifier circuit. This is because the forward voltage drop is small and the output of the first booster circuit can be efficiently returned to the power supply terminal of the first booster circuit. This also leads to miniaturization of the power supply system.

  Further, since the driving of the second booster circuit is stopped according to the voltage of the first boosted power, the second booster circuit is not driven under the conditions, and the efficiency can be improved. As a result, the size of the second booster circuit can be reduced, and the entire volume can be reduced.

  One specific method for controlling the driving of the second booster circuit is to use an enable terminal.

  It is preferable that the voltage of the first boosted power is higher than the voltage of the second boosted power as the voltage of the first boosted power desired for stopping the driving of the second booster circuit. This is a state that occurs when the first booster circuit is activated, and the above description means that when the first booster circuit is activated, the second booster circuit is stopped.

  When the output power of the power generation unit is used in a load via the first booster circuit or the like, the power generation unit must generate the power consumed or leaked in the first booster circuit or the like simultaneously with the power for driving the load. I must. Therefore, when the efficiency of power transmission from the power generation unit to the load is low, it is necessary to increase the output power of the power generation unit, and for this purpose, it is necessary to increase the volume of the power generation unit. Conversely, if a system that efficiently uses the power output from the power generation unit to drive the load is created by minimizing unnecessary power leakage and consumption, a power supply system can be produced in a size that can be applied to small electronic devices. It becomes possible.

  By the above means, that is, by controlling the operation of the rectifier circuit and the second booster circuit, wasteful energy consumption can be reduced, efficiency can be improved, and the power supply system can be downsized.

  It has a control circuit that detects the voltage of the generated power and controls the operation of the first booster circuit so that the voltage of the generated power becomes equal to or higher than a desired voltage.

  The output power of the power generation unit draws a substantially quadratic curve having a peak with respect to the voltage. Accordingly, when the voltage corresponding to the maximum value of the output power of the power generation unit falls below the input voltage of the first booster circuit, that is, the output voltage of the power generation unit, the output power of the power generation unit decreases and becomes inefficient. The control of the first booster circuit is to prevent this. This makes it possible to operate the power generation unit and the first booster circuit with high efficiency.

  In relation to the above, in the design of the power supply system, it is preferable to determine the specifications of the power generation unit in consideration of the efficiency of the first booster circuit from the power consumption profile of the load. The specifications of the power generation unit are internal impedances. In the fuel cell, factors related to this include the electrode area and the inter-electrode distance related to the size of the power generation unit. The size determined by this method is the size of the smallest power supply system, and the power supply system is driven with high efficiency.

  The power generation unit uses at least one of a group consisting of a fuel cell, a solar cell, a thermoelectric conversion element, electromagnetic induction, and a piezoelectric conversion element.

  These are power generation means that can output only a very small voltage in an open circuit when used with a small number of cells or when the dimensions are small. However, by using the second booster circuit together, the first booster circuit can be driven even when the power generation unit is applied. Therefore, it is not necessary to increase the size of the power generation unit, and it can be applied as a power supply system for small electronic devices. In particular, in the fuel cell, a mechanism for supplying fuel to the electrode is required for each cell. However, according to this means, the number of cells can be reduced, so that it is effective as a power supply system for small electronic devices.

  A switched capacitor type booster circuit is used for the second booster circuit.

  As the booster circuit, there is a booster circuit in which a coil, a Schottky diode, and a capacitor are combined. In this type, the thickness increases by the height of the coil. On the other hand, the switched capacitor type does not require a height, and if the capacitance is small, it can be built in the IC chip. Therefore, since the second booster circuit can be made small by the means of this solution, it is possible to create a power supply system having a size suitable for application to a small electronic device.

  In addition, it is more preferable to use a semiconductor integrated circuit formed on an SOI substrate as the second booster circuit element, because the leakage current can be further reduced.

  As a result, the second booster circuit can extremely reduce the minimum drive voltage.

  In addition, the minimum startup voltage of the second booster circuit is lower than the minimum startup voltage of the first booster circuit, and the booster voltage is generated as much as necessary to start up the first booster circuit. It is possible to reduce the size.

  A system having a voltage detection circuit for detecting the output voltage of the first booster circuit and generating a signal for stopping the driving of the second booster circuit when the output voltage is higher than the starting voltage of the first booster circuit; By doing so, it is possible to efficiently supply power to the first booster circuit.

  In addition, a system having a control circuit that is connected between the power generation unit and the first booster circuit control terminal and controls the maximum power of the output of the power generation unit, effectively supplies the power of the power generation unit to the first booster circuit. It becomes possible.

  As described above, in order to solve the above-described problems, in the present invention, the power generation unit that generates the generated power and the first boosted power that converts the generated power into the first boosted power having a voltage higher than the voltage of the generated power. And a second booster circuit that converts the generated power into a second boosted power having a voltage higher than the voltage of the generated power, and drives the load with the first boosted power. Thus, the first booster circuit is activated using the second boosted power.

  As a result, the first booster circuit can be driven without lowering the minimum starting voltage of the first booster circuit. That is, since the output power of the power generation unit can be used for the load with high efficiency without reducing the efficiency of the first booster circuit, the volume of the power generation unit can be reduced.

  The first booster circuit has a voltage detection circuit that maintains the operation by the first boosted power supplied via the rectifier circuit and detects the voltage of the first boosted power supplied via the rectifier circuit. When the first boosted power supplied via the rectifier circuit becomes equal to or higher than a desired voltage, the driving of the second booster circuit is stopped.

  Thereby, it becomes possible to prevent the power of the power generation unit from flowing to the load via the second booster circuit. In addition, since the driving of the second booster circuit is stopped according to the voltage of the first boosted power, the second booster circuit is not driven under the conditions, and the efficiency can be improved.

  As described above, according to the present invention, there is provided a power supply system for a small electronic device such as a mobile phone or a notebook computer, wherein a booster circuit is applied to drive a load, and a power generation means having an output voltage lower than the starting voltage of the booster circuit. Even when it is used, it is possible to provide a small power supply system that can drive a load.

  FIG. 1 is a schematic block diagram of a power supply system according to the present invention. As shown in FIG. 1, the present invention includes a power generation unit 10 that generates power, a first booster circuit 20 that boosts the power output from the power generation unit 10, and a second booster that activates the first booster circuit 20. Booster circuit 30, voltage detection circuit 40 for controlling ON / OFF of second booster circuit 30, diode element 50 for allowing power of second booster circuit 30 to flow only to first booster circuit 20, first booster A control circuit 60 for controlling the circuit 20 is provided. A load circuit such as an electronic device is driven using the power output from the first booster circuit 20.

  The present invention relates to a power supply system when a small electronic device such as a notebook computer, a mobile phone, a digital still camera, or a PDA is used as a load circuit. Therefore, the required characteristics are small size, light weight, high energy density, and high reliability. In order to obtain a high energy density, the ratio between the power consumption and the output power when driving the load circuit with the generated power, that is, high efficiency is required.

  In the present embodiment, as a specific example of the structure, a methanol fuel cell is directly used for the power generation unit 10, a switched capacitor is used for the second booster circuit 30, and a Schottky diode is used for the diode element 50.

  In the present invention, even when the output voltage of the power generation unit 10 is lower than the minimum drive voltage of the first booster circuit 20 or the load circuit, power can be supplied efficiently, and the power supply has a size that can be mounted on a small electronic device. The system is provided.

  A comparison of the specifications of various power supply systems using direct methanol fuel cells is shown in FIG. As the structure of the power supply system using the fuel cell, the following three types can be considered. (1) The type of FIG. 1 that combines a single-cell fuel cell that does not forcibly supply fuel and a booster circuit, (2) A fuel cell that forcibly supplies fuel, (3) Forcibly supplies fuel A type in which multiple cells are connected in series with a non-performing fuel cell. Among these, (1) is a power supply system of a present Example.

  FIG. 2 is a schematic view from above showing the power supply system of Comparative Example (2). A pipe 110 is connected to the electrode 70, the air supply compressor 100, and the fuel supply pump 110, and a fuel tank 80 is provided. Although only a single cell is written on the electrode 70, a plurality of cells are actually stacked in this depth direction. In addition, there are drive control circuits for the compressor 100 and the pump 110. Characteristically, since the fuel is forcibly supplied, the internal impedance is low and the electrode area is small. However, since it takes electric power to drive the fuel supply system such as the pump and piping, the power generation amount and the fuel volume must be increased accordingly, the drive control circuit is necessary, the fuel supply system and the control There are disadvantages such as taking a volume with the system.

  FIG. 3 is a schematic view from above showing the power supply system of Comparative Example (3). An extremely large number of electrodes 70 are arranged in a plane, and the fuel is naturally fed from the fuel tank 80 through the pipe 110 to this. The plurality of electrodes 70 have a gap so as not to contact each other, and are connected in series. Since the internal impedance is high, the electrode area is large and the volume of the fuel tank 80 is also large. The feature is the simplest structure, but the number of series is extremely large. This is because the direct methanol fuel cell has a high internal impedance and a low output voltage, and the drive voltage of the electronic device is high. Further, in a series connection of a plurality of cells, the performance variation of only one cell causes a rapid deterioration of the cell, and thus the whole cannot be energized. Therefore, no variation in performance is allowed, and in this state, it is difficult to manufacture a highly reliable product as a power source for small electronic devices.

  On the other hand, (1) is more advantageous than other types in terms of size and manufacturing. Table 1 shows a comparative example of specifications of various power supply systems when a mobile phone is used as a small electronic device.

  In (1), the volume is not taken up by the fuel supply system and its control system as in (2), so the size is small.

  The volume of the fuel tank or fuel supply system in (1) is almost the same as that in (3), but the volume of the electrode part is greatly different. The electrode (1) is a single cell, while (3) is connected to a plurality of cells. Therefore, in (3), the volume between the cells increases the volume of the electrode part. Due to the number of cells, (1) is also very advantageous in terms of manufacturing.

  Further, in (4), a booster circuit or the like having a efficiency of only about 50% of (1) was used as a comparative example. This is the case where control of the switched capacitor, which is the second booster circuit 30, prevention of current backflow by the diode element 50, control of the booster circuit by the control circuit 60, and the like are not performed as in the present invention. In order to drive the load circuit, it is necessary to increase the amount of power generation and the amount of fuel correspondingly to the low efficiency compared with (1). Therefore, the size of the electrode and the fuel tank has become extremely large.

  That is, according to the present invention, it is possible to produce a power supply system that is optimal for application to a mobile phone.

  The present invention is not limited to the above embodiments.

It is a schematic block diagram of the power supply system of the Example by this invention. It is a schematic diagram from the upper surface which shows the power supply system of a comparative example (2). It is a schematic diagram from the upper surface which shows the power supply system of a comparative example (3). It is a schematic block diagram of a prior art example. Comparison of specifications of various power supply systems using direct methanol fuel cells.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Power generation part 11 Fuel cell 12 Secondary battery 20 1st voltage booster circuit 21 Power converter 30 2nd voltage booster circuit 40 Voltage detection circuit 50 Diode element 60 Control circuit 61 Charge control means 70 Electrode 80 Fuel tank 90 Compressor 100 Pump 110 Piping 120 Switch 130 Load

Claims (11)

A power generation unit that generates generated power;
A first booster circuit connected to the power supply and boosting the electromotive force;
A second booster circuit connected to the power source for boosting the electromotive force and generating power for driving the first booster circuit;
The power supply system according to claim 1, wherein the first booster circuit is driven by an output voltage of the first booster circuit.   The power supply system according to claim 1 or 2, wherein a minimum startup voltage of the second booster circuit is lower than that of the first booster circuit.   A voltage detection circuit for detecting an output voltage of the first booster circuit and generating a signal for stopping the driving of the second booster circuit when the output voltage is higher than a starting voltage of the first booster circuit; The power supply system according to any one of claims 1 to 3.   5. The power supply system according to claim 1, further comprising: a control circuit that is connected between the power generation unit and the first booster circuit control terminal and controls the maximum power of the output of the power generation unit. A power generation unit that generates generated power;
A first booster circuit for converting the generated power into a first boosted voltage having a voltage higher than the voltage of the generated power;
A second booster circuit that converts the generated power into a second boosted voltage having a voltage higher than the voltage of the generated power;
A power supply system for driving a load with the first boosted voltage, wherein the first booster circuit is activated by the second boosted voltage. The first booster circuit continues to operate with the first boosted power supplied via the rectifier circuit, and detects a voltage of the first boosted power supplied via the rectifier circuit. Having a detection circuit;
2. The power supply system according to claim 1, wherein when the first boosted voltage supplied via the rectifier circuit is equal to or higher than a desired voltage, driving of the second booster circuit is stopped.   3. The control circuit according to claim 1, further comprising a control circuit that detects a voltage of the generated power and controls an operation of the first booster circuit so that the voltage of the generated power becomes equal to or higher than a desired voltage. Power system.   The power supply apparatus according to claim 1, wherein the power supply is a fuel cell.   The power supply device according to any one of claims 1 to 7, wherein the power source is any one selected from a solar cell, a thermoelectric conversion element, an electromagnetic induction, and a piezoelectric conversion element.   10. The power supply device according to claim 1, wherein the second booster circuit is a switched capacitor type booster circuit.   The power supply device according to claim 1, wherein the second booster circuit is a semiconductor integrated circuit formed on an SOI substrate.

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