JP2007244129A - Power supply - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power supply for effectively utilizing power stored in a storage device. <P>SOLUTION: The power supply 1 for combining a battery 8 and the storage device 2 comprising an electric double layer capacitor C for driving a portable device 7 is provided with a current limiting circuit 3 for limiting a current value of an output current Ic from the storage device 2 within a predetermined upper limit, and a control circuit 6 for changing the upper limit. The control circuit 6 changes the upper limit in response to a temperature Tc of the storage device 2 or an output voltage Vc from the storage device 2. An effect due to an internal resistance of the electric double layer capacitor C is reduced, and an available time of the power supply 1 and the portable device 7 is extended by relatively reducing the upper limit at a low temperature. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a power supply device using an electric storage device such as an electric double layer capacitor.

  Power storage devices represented by electric double layer capacitors have a longer life than secondary batteries represented by lithium ion secondary batteries, and can be charged and discharged with a large current. It is attracting attention as a device or a quick charging device. In addition, there is a promising use method in which one load device is driven while complementing the functions of the secondary battery by utilizing the characteristics. However, since a large current is handled, the internal resistance greatly affects the output characteristics. For example, handling at a low temperature becomes a problem.

  In addition, the following conventional technologies exist as technologies related to power storage devices typified by electric double layer capacitors.

  In the electric double layer capacitor built-in power supply device, the use lower limit voltage is set, and when the voltage between the terminals of the electric double layer capacitor falls below the use lower limit voltage, the discharge of the electric double layer capacitor is stopped (for example, Patent Document 1 below) reference).

  Considering that the internal resistance of the capacitor increases at a low temperature, the minimum stored voltage (use lower limit voltage) of the capacitor as a power source is set relatively high at a low temperature (for example, see Patent Document 2 below).

  The internal resistance is calculated based on the inter-terminal voltage of the secondary battery and the charge / discharge current, and the degree of deterioration of the secondary battery is determined based on the calculation result (for example, see Patent Document 3 below).

JP 2000-197277 A JP 2003-219564 A JP 2002-75461 A

  As described above, when an electricity storage device represented by an electric double layer capacitor is used as a power source, for example, handling at a low temperature becomes a problem. If the use lower limit voltage is fixed regardless of the temperature as in Patent Document 1, the use lower limit voltage is reached quickly at low temperatures, and power cannot be effectively extracted. In addition, as in Patent Document 2, even when the use lower limit voltage is set high at a low temperature, the stored power cannot be effectively used.

  Although problems related to the effective use of stored electricity have been described as an example at low temperatures, proper control of the output of the storage device in accordance with the characteristics of the storage device is also considered in terms of effective use of stored power even in other situations. Very important from.

  In addition, since a load cannot be driven appropriately if a deteriorated power storage device is used, a technique for determining deterioration of the power storage device by a simple method is also desired. Note that the technique disclosed in Patent Document 3 requires a complicated operation, which complicates the circuit.

  Therefore, an object of the present invention is to provide a power supply apparatus that can effectively use the stored power of the power storage device. Another object of the present invention is to provide a power supply device that can easily determine deterioration of an electricity storage device.

  In order to achieve the above object, a power supply device according to the present invention includes a power storage device that changes an output voltage according to stored power, and supplies power to a load device while using an external power source. A current limiting circuit that limits a current value of an output current of the power storage device to a predetermined upper limit value or less and a control circuit for changing the upper limit value are provided.

  For example, the control circuit changes the upper limit value according to the temperature of the power storage device.

  Specifically, for example, the control circuit sets the upper limit value to a predetermined first upper limit value when the temperature of the power storage device is a predetermined first temperature, and the temperature of the power storage device is higher than the first temperature. The upper limit value is set to a predetermined second upper limit value smaller than the first upper limit value when the predetermined second temperature is lower than the first upper limit value.

  For example, the control circuit changes the upper limit value according to the output voltage of the power storage device.

  For example, the control circuit changes the upper limit value according to the output voltage of the power storage device and the output current of the power storage device.

  Further, for example, the current limiting circuit includes a voltage conversion circuit that converts the output voltage of the power storage device into an instructed set voltage having a different voltage value and outputs the converted voltage, and the control circuit responds to the set voltage. To change the upper limit value.

  For example, the control circuit determines the upper limit value according to the set voltage, and further changes the upper limit value according to the output voltage of the power storage device.

  Considering the characteristics of the storage device, the stored power of the storage device can be effectively extracted by changing the upper limit value according to the temperature of the storage device, the output voltage of the storage device, or the set voltage. . As a result, it is possible to expect an extension of the usable time of the power supply device and the load device.

  In addition, for example, when the output voltage of the power storage device becomes a predetermined voltage or less despite the control circuit changing the upper limit value, the control circuit determines that the power storage device is in a deteriorated state. .

  Thereby, it is possible to easily determine the deterioration of the electricity storage device by referring to the output voltage of the electricity storage device.

  Further, for example, the resistance value of the internal resistance of the power storage device increases as the power storage device deteriorates, and when the resistance value of the internal resistance is smaller than a predetermined deterioration threshold, the current of the output current of the power storage device Even if the value becomes equal to the set upper limit value, the upper limit value is set so that the output voltage of the electricity storage device is higher than the predetermined voltage.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to take out the electrical storage electric power of an electrical storage device effectively. Further, according to the present invention, it is possible to easily determine the deterioration of the electricity storage device.

  Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings. In the respective drawings to be referred to, the same portions are denoted by the same reference numerals. FIG. 1 is a schematic block diagram of a power supply device 1 according to an embodiment of the present invention.

  The power supply device 1 includes an electricity storage device 2, a current limiting circuit 3, a temperature detector 4, a voltage detector 5, and a control circuit 6.

  The electricity storage device 2 is composed of an electric double layer capacitor (electric double layer capacitor) C. The electric double layer capacitor C is composed of a single electric double layer capacitor. The electric double layer capacitor C may be configured by connecting a plurality of electric double layer capacitors in parallel. In this case, in order to optimize the control described later, it is desirable that the characteristics (such as the internal resistance value and the temperature dependence of the internal resistance value) of the plurality of electric double layer capacitors be the same. When variation in characteristics among a plurality of electric double layer capacitors cannot be ignored, it is desirable to form the electric double layer capacitor C with a single electric double layer capacitor. The positive electrode of an electric double layer capacitor C (hereinafter simply referred to as “capacitor C”) is connected to the current limiting circuit 3. The negative electrode of the capacitor C is connected to a ground line GND fixed at a reference potential (for example, 0 V).

  Now, the output voltage of the electricity storage device 2, that is, the voltage between both terminals of the capacitor C is represented by Vc, and the output current of the electricity storage device 2, that is, the discharge current of the capacitor C is represented by Ic.

The power output from the power storage device 2 is supplied to the portable device 7 as the load device of the power supply device 1 via the current limiting circuit 3. At that time, the current limiting circuit 3 limits the current value of the output current Ic of the power storage device 2. That is, the current limiting circuit 3 has a function of limiting the current value of the output current Ic from the power storage device 2 to a predetermined upper limit value or less. The upper limit value is hereinafter referred to as the upper limit value I _L.

  The current limiting circuit 3 is a linear regulator or a switching regulator that uses the output voltage Vc of the power storage device 2 as an input voltage. However, the voltage output from the current limiting circuit 3 is not necessarily a constant voltage. The voltage output from the current limiting circuit 3 is denoted by Vo. The voltage Vo is the output voltage of the power supply device 1. The current value of the current Ic flowing into the current limiting circuit 3 from the power storage device 2 and the current value flowing out of the current limiting circuit 3 into the portable device 7 can be different.

  With reference to the ground line GND, the output voltage Vo of the current limiting circuit 3 is supplied to the portable device 7 via the voltage input terminal 9 provided in the portable device 7. The mobile device 7 as the load device is, for example, a mobile phone or a mobile information terminal. The portable device 7 incorporates a battery 8 as a power source, and the portable device 7 is driven by using both the power supplied from the battery 8 and the power supplied from the power supply device 1 (voltage is Vo). To do. The battery 8 is a secondary battery such as a lithium ion secondary battery or a primary battery. When the battery 8 is a secondary battery, the battery 8 can be charged using the voltage Vo output from the power supply device 1.

  The current limiting circuit 3 incorporates a current detector (not shown in FIG. 1) that detects the current value of the output current Ic of the power storage device 2. The detection result of the current detector, that is, information specifying the current value of the detected output current Ic is transmitted to the control circuit 6.

  The temperature detector 4 detects the temperature of the electricity storage device 2. This detected temperature is represented by Tc. The detection result of the temperature detector 4, that is, information specifying the detected temperature Tc is transmitted to the control circuit 6. The temperature detector 4 is composed of, for example, a thermistor (not shown) arranged so as to be thermally coupled to the surface of the capacitor C.

  The voltage detector 5 detects the voltage value of the output voltage Vc of the electricity storage device 2. The detection result of the voltage detector 5, that is, the information specifying the voltage value of the detected output voltage Vc is transmitted to the control circuit 6.

The output current Ic, the temperature Tc, and the output voltage Vc are sequentially detected, for example, at a predetermined sampling period. The control circuit 6 sets the upper limit value I _L on the basis of the values detected, the current value of the output current Ic controls the current limiting circuit 3 so as not to exceed the upper limit value I _L.

Since the portable device 7 is driven by using the power supply device 1 and the battery 8 in parallel, even if an upper limit value I _L is provided for the output current Ic, the upper limit value I _L is changed as will be described later. However, there is no problem in the operation of the mobile device 7.

Hereinafter, a method of setting the upper limit value I _L by the control circuit 6 (modified method) illustrates the first, second and third setting method. The control circuit 6 can employ any setting method among the first to third setting methods. A setting method combining them can also be adopted.

  The discharge end voltage (use lower limit voltage) of the capacitor C is represented by Vc_min. As exemplified later with reference to FIG. 8, a voltage conversion circuit such as a boost chopper circuit is driven by the output voltage Vc of the capacitor C. When the voltage Vc decreases, the circuit efficiency of the boost chopper circuit and the like decreases while increasing the boost ratio and increasing the current Ic. In order to avoid this, the discharge end voltage Vc_min is set in advance. When the voltage Vc becomes equal to or lower than the discharge end voltage Vc_min, the power supply device 1 (for example, the control circuit 6) stops the discharge by the capacitor C.

[First setting method]
The first setting method will be described. First, the characteristics of the capacitor C will be described.

  As shown in FIG. 2, it can be considered that the capacitor C includes an internal resistance Rc connected in series with the capacitance component. As shown in FIG. 3, the resistance value of the internal resistance Rc has a characteristic of increasing at a low temperature. Even if the resistance value of the internal resistance Rc is a large value, if the discharge of the capacitor C which is the same as that at the time of high temperature is allowed, the time until the voltage Vc reaches the discharge end voltage Vc_min is shortened. That is, the usable time of the power supply device 1 and the portable device 7 is shortened.

  FIG. 4 is a diagram showing the time change of the voltage Vc when the capacitor C is discharged at a constant current. A solid line 61 indicates that the resistance value of the internal resistance Rc is zero, a solid line 62 indicates that when the resistance value of the internal resistance Rc is relatively small, and a solid line 63 indicates that the resistance value of the internal resistance Rc is relatively large. It represents that. When comparing the case where the resistance value of the internal resistance Rc is relatively small and the case where the resistance value is relatively large, the latter can be used for a shorter usable time (in FIG. 4, the shorter time is represented by reference numeral 64).

In consideration of the above circumstances, in the first setting method, the upper limit value _IL is changed according to the temperature Tc of the capacitor C. Specifically, the upper limit value I _L is decreased as the temperature Tc decreases.

For example, room temperature (for example, 25 ° C.) is represented by T ₁ , and a lower temperature (for example, 0 ° C.) is represented by T ₂ (T ₁ > T ₂ is satisfied). Then, the upper limit value I _L at the time of Tc = T ₂ is to be smaller than the upper limit value I _L at the time of Tc = T _1, the control circuit 6 changes the upper limit value I _L in accordance with the temperature Tc.

In this case, for example, it is determined in advance a plurality of threshold temperature to change the upper limit value I _L, so as to switch the upper limit value I _L stepwise according to a result of comparison between the temperature Tc and the threshold temperature. Further, for example, the upper limit value I _L to be set may be expressed as a function of the temperature Tc, and the upper limit value I _L may be continuously changed according to the detected temperature Tc according to the function. In setting the function, a function representing the relationship between the resistance value of the internal resistance Rc and the temperature Tc may be considered.

FIG. 5 shows the change over time of the voltage Vc at a low temperature. The solid line 65 represents the case where the upper limit value I _L is unchanged without using the first setting method, and the solid line 66 represents the case where the upper limit value I _L is reduced using the first setting method. Yes. As can be seen from FIG. 5, by using the first setting method, the usable time of the power supply device 1 and the portable device 7 can be extended by an amount corresponding to the time represented by reference numeral 67.

[Second setting method]
Next, the second setting method will be described.

  As is well known, the terminal voltage (output voltage Vc) of the capacitor C changes in accordance with the stored power (stored power) of the capacitor C, and the terminal voltage decreases as the stored power decreases. On the other hand, due to the influence of the internal resistance Rc, the terminal voltage decreases more as the discharge current increases. Therefore, when a large current is discharged particularly when the stored power is low, the time until the discharge end voltage Vc_min is reached is shortened, and the usable time of the power supply device 1 and the portable device 7 is shortened.

Considering the above circumstances, in the second setting method, the upper limit value _IL is changed according to the terminal voltage of the capacitor C (that is, the output voltage Vc of the power storage device 2). Specifically, the upper limit value I _L is decreased as the voltage Vc decreases.

At this time, for example, a plurality of threshold voltages for which the upper limit value I _L is to be changed are determined, and the upper limit value I _L is switched stepwise according to the comparison result between the voltage Vc and each threshold voltage. Further, for example, the upper limit value I _L to be set may be represented as a function of the voltage Vc, and the upper limit value I _L may be continuously changed according to the detected voltage Vc according to the function.

6, in a case where to discharge the capacitor C under the conditions of Ic = I _L, a diagram showing the time variation of the voltage Vc. A solid line 69 represents that when the upper limit value I _L is not changed without using the second setting method, and a solid line 70 represents that when the upper limit value I _L is changed according to the voltage Vc. ing. As can be seen from FIG. 6, by using the second setting method, the usable time of the power supply device 1 and the portable device 7 can be extended by an amount corresponding to the time represented by reference numeral 71.

Further, even if the stored power of the capacitor C is the same, the voltage Vc can change according to the current Ic due to the influence of the internal resistance Rc. Therefore, when setting the upper limit value I _L in accordance with the voltage Vc, may further consider the detection result of the current Ic. That may be determined the upper limit value I _L in accordance with the voltage Vc and current Ic. Thus, more appropriately it is possible to change the upper limit value I _L, it is possible to further extend the usable time of the power supply device 1 and the portable device 7.

For example, first, while determining the reference value of the upper limit value I _L in accordance with the voltage Vc, with reference to the detected value of the current Ic in the same timing (current value), determining the correction value corresponding to the detected value of the current Ic . Then, a value obtained by adding the correction value to the reference value, and finally adopted as the upper limit value I _L. The correction value is, for example, a positive value that increases as the detected value of the current Ic increases.

Furthermore, the final upper limit value I _L may be determined in consideration of the temperature Tc.

[Third setting method]
Next, the third setting method will be described. When the first or second setting method is adopted, the current limiting circuit 3 does not need to function as a voltage conversion circuit such as a constant voltage circuit. However, the current setting circuit 3 functions as a constant voltage circuit. It is adopted on the assumption that Various known or well-known circuit configurations can be applied to the current limiting circuit 3 in order to cause the current limiting circuit 3 to function as a constant voltage circuit. By incorporating a constant voltage circuit into the power supply device 1, the versatility of the power supply device 1 is enhanced.

  When the third setting method is adopted, the current limiting circuit 3 converts the voltage Vc into a voltage Vo having a different voltage value and outputs the converted voltage Vo. At this time, the voltage value of the voltage Vo is set to an arbitrary voltage value within a predetermined range by a voltage setting circuit (not shown). Information for specifying the voltage value of the voltage set by the voltage setting circuit (hereinafter referred to as the set voltage Vs) is transmitted to the control circuit 6. The control circuit 6 makes the voltage Vo equal to the set voltage Vs while referring to the detected value (voltage value) of the voltage Vo sent from a voltage detector (not shown) for detecting the voltage value of the voltage Vo. Thus, the current control circuit 3 that functions as a constant voltage circuit is controlled.

By the way, when the constant voltage circuit is configured as a booster circuit, when the set voltage Vs (= Vo) is increased, the boost ratio is increased and the circuit efficiency of the booster circuit tends to be lowered. For this reason, even when the same power is output from the capacitor C, if the set voltage Vs is increased, the output current Ic from the capacitor C increases. Therefore, if the upper limit value I _L is not changed regardless of the set voltage Vs, the time until the discharge end voltage Vc_min is reached when the set voltage Vs is high, and the usable time of the power supply device 1 and the portable device 7 is shortened. Will be shorter.

Considering the above circumstances, in the third setting method, the upper limit value _IL is changed according to the set voltage Vs. Specifically, the upper limit value I _L is decreased as the set voltage Vs increases. As a result, the usable time of the power supply device 1 and the portable device 7 can be extended.

At this time, for example, a plurality of threshold voltages for which the upper limit value I _L is to be changed are determined, and the upper limit value I _L is switched stepwise according to the comparison result between the set voltage Vs and each threshold voltage. Further, for example, the upper limit value I _L to be set may be expressed as a function of the set voltage Vs, and the upper limit value I _L may be continuously changed according to the set voltage Vs according to the function.

Further, upon setting the upper limit value I _L (changed) in accordance with the set voltage Vs, further it may be changed to the upper limit value I _L in accordance with the output voltage Vc of the electric storage device 2.

For example, the set upper limit value I _L to a certain first upper limit value I _L1 in accordance with the set voltage Vs. When the power supply device 1 is operated under the restriction of the first upper limit value I _L1 , the control circuit 6 refers to the detected value (voltage value) of the output voltage Vc and sets the detected value of the output voltage Vc. Accordingly, the upper limit value I _L is further changed from the first upper limit value I _L1 to another value. However, at this time, the upper limit value I _L is set so as not to exceed the first upper limit value I _L1 . Specifically, with reference to the first upper limit value I _L1 , the upper limit value I _L is decreased as the voltage Vc decreases.

Incidentally, in consideration of the output current Ic or the temperature Tc of the electric storage device 2 further final limit I _L may be set.

[Deterioration judgment]
FIG. 7 shows the relationship between the cumulative discharge time (number of charge / discharge) of the capacitor C and the resistance value of the internal resistance Rc when the capacitor C is discharged under certain conditions. Due to its characteristics, the capacitor C gradually deteriorates as the resistance value of the internal resistance Rc increases with use. Then, the resistance value of the internal resistance Rc finally reaches a predetermined deterioration threshold value R _TH , and when the discharge is further continued, the resistance value further increases.

In the power supply device 1, when the resistance value of the internal resistance Rc is less than the degradation threshold value R _TH, the capacitor C is determined to be in a normal state, when the resistance value of the internal resistance Rc is greater than the degradation threshold value R _TH, the capacitor C Is judged to be in a deteriorated state.

Then, the control circuit 6 sets the upper limit value I _L using the method described above, assuming that the capacitor C is in a normal state. Indeed if the capacitor C is in the normal state "(i.e., the case of Rc <R _TH), even becomes equal to the upper limit value I _L the current value of the current Ic is set, the voltage Vc from the discharge end voltage Vc_min The control circuit 6 sets the upper limit value I _L so that “high is also maintained”. Therefore, if the capacitor C is in the normal state, the control of changing the upper limit value I _L that has been described above, it is not that the voltage Vc becomes less than the discharge cutoff voltage Vc_min.

Using this, the control circuit 6 can determine whether or not the capacitor C is in a deteriorated state based on the voltage Vc. In other words, despite doing changes the upper limit value I _L, as has been described above, when the voltage Vc becomes less than the discharge cutoff voltage Vc_min, the control circuit 6, the capacitor C is experiencing a degraded state Judgment can be made.

  When it is determined that the capacitor C is in a deteriorated state, the control circuit 6 stops discharging the capacitor C and outputs a deterioration signal for specifying that the capacitor C is in the deteriorated state. The deterioration signal is transmitted to, for example, an LED (Light Emitting Diode) provided in the power supply device 1 or the portable device 7, a display unit such as a liquid crystal display, an audio output unit including a speaker, and the like. Then, the user is notified of the deterioration of the capacitor C or the notification that the capacitor C should be replaced, for example, visually or audibly.

[Current limit circuit]
FIG. 8 shows a circuit diagram of a boost chopper circuit as an example of the current limiting circuit 3. The step-up chopper circuit of FIG. 8 includes a current detector 15, an inductor 16, a switch 17 including a FET (Field Effect Transistor), a diode 18, and a capacitor 19.

  A pair of input terminals 11 and 12 are provided on the input side of the current limiting circuit 3, and a pair of output terminals 13 and 14 are provided on the output side of the current limiting circuit 3. Both the negative voltage side input terminal 12 and the negative voltage side output terminal 14 are connected to a ground line GND fixed at a reference potential (for example, 0 V). The input terminal 11 on the positive voltage side is connected to the positive voltage output terminal (that is, the positive electrode of the capacitor C) of the power storage device 2, and the output terminal 13 on the positive voltage side is connected to the voltage input terminal 9 of the portable device 7. . The voltage Vc is applied to the input terminal 11, and the output current Ic of the electricity storage device 2 flows through the input terminal 11.

  The input terminal 11 is connected to one end of the inductor 16 through the current detector 15. The other end of the inductor 16 is connected to the anode of the diode 18 and one terminal 17a of the switch 17 (for example, the drain of the FET). The other terminal 17b (for example, the source of the FET) of the switch 17 is connected to the ground line GND. The control circuit 6 makes the two terminals 17a and 17b of the switch 17 conductive or non-conductive by giving a control signal to the control terminal of the switch 17 (for example, the gate of the FET). Hereinafter, regarding the switch 17, a state where both terminals 17 a and 17 b are conductive is expressed as “ON”, and a state where both terminals 17 a and 17 b are non-conductive is expressed as “OFF”.

  The cathode of the diode 18 is connected to one end of the capacitor 19 and the output terminal 13. The other end of the capacitor 19 is connected to the ground line GND. With reference to the ground line GND, the voltage appearing at the output terminal 13 is the voltage Vo described above.

  The current detector 15 includes a shunt resistor interposed in series with a line connecting the input terminal 11 and the inductor 16, for example, and detects a current flowing through the line, that is, a current value of the output current Ic of the power storage device 2. The detection result of the current detector 15, that is, information for specifying the current value of the detected output current Ic is transmitted to the control circuit 6. Further, the voltage value of the voltage Vo appearing at the output terminal 13 is detected by a voltage detector (not shown), and information for specifying the detected voltage value of the voltage Vo is also transmitted to the control circuit 6.

The control circuit 6 sets the upper limit value I _L using the method described above, and controls the switch 17 on / off so that the output current Ic does not exceed the upper limit value I _L.

Under the limitation of the upper limit value I _L , the control circuit 6 controls, for example, the duty ratio for turning on / off the switch 17 at a predetermined frequency and turning on the switch 17 while referring to the voltage value of the voltage Vo. As a result, the voltage Vo is maintained at a constant voltage (for example, the set voltage Vs).

  Note that ripple (ripple voltage or ripple current) appears in the voltage and current appearing at the input terminal 11 and the voltage appearing at the output terminal 13 as the switch 17 is switched from ON to OFF or from OFF to ON. However, when discussing Vc, Ic and Vo, such ripples are ignored. That is, Vc, Ic, and Vo are values obtained by removing such ripple frequency components (average values ignoring the ripple components).

<< Deformation, etc. >>
According to the characteristics of the capacitor C as described above, by changing the upper limit value I _L of the discharge current of the capacitor C (Ic), effectively the stored power of the capacitor C by reducing the influence of the voltage drop due to the internal resistance It can be taken out. As a result, the usable time of the power supply device 1 and the portable device 7 can be extended.

In the case of using a method that does not refer to the detection value of the voltage Vc when setting the upper limit value I _L, the voltage detector 5 of Figure 1 may be omitted. Similarly, when using a method that does not refer to the detection value of the temperature Tc when setting the upper limit value I _L, the temperature detector 4 in FIG. 1 can be omitted.

  Further, a charging device for charging the capacitor C shown in FIG. 1 is built in the power supply device 1 of FIG. 1 or provided outside the power supply device 1.

  Although the electric double layer capacitor C has been exemplified as the power storage device 2, any power storage device whose output voltage changes according to the stored power can be used as the power storage device according to the present invention. For example, the electricity storage device according to the present invention may be a capacitor or a secondary battery classified other than an electric double layer capacitor, or may be an electricity storage device that cannot be clearly classified as a capacitor or a battery. May be.

  Moreover, although the portable apparatus 7 was illustrated as a typical load of the power supply device 1, the portability of the load of the power supply device 1 is not ask | required.

1 is a schematic block diagram of a power supply device 1 according to an embodiment of the present invention. It is an internal equivalent circuit schematic of the capacitor | condenser of FIG. It is a figure showing the temperature dependence of the internal resistance of FIG. It is a figure showing the time change of the output voltage of a capacitor when the capacitor of FIG. 1 is discharged with a constant current. It is a figure for demonstrating the 1st setting method of the upper limit by the control circuit of FIG. It is a figure for demonstrating the 2nd setting method of the upper limit by the control circuit of FIG. It is a figure showing the relationship between the total discharge time and internal resistance of the capacitor | condenser of FIG. FIG. 2 is a circuit diagram of a boost chopper circuit as an example of the current limiting circuit of FIG. 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Power supply device 2 Power storage device 3 Current limiting circuit 4 Temperature detector 5 Voltage detector 6 Control circuit 7 Portable device 8 Battery 9 Voltage input terminal 15 Current detector C Electric double layer capacitor

Claims (9)

In a power supply device that includes a power storage device whose output voltage changes according to stored power, and supplies power to a load device while using an external power source in combination,
A current limiting circuit for limiting the current value of the output current of the electricity storage device to a predetermined upper limit value or less;
And a control circuit for changing the upper limit value. The power supply apparatus according to claim 1, wherein the control circuit changes the upper limit value according to a temperature of the power storage device. The control circuit sets the upper limit value to a predetermined first upper limit value when the temperature of the power storage device is a predetermined first temperature, and a predetermined second temperature in which the temperature of the power storage device is lower than the first temperature. 3. The power supply device according to claim 2, wherein when the temperature is a temperature, the upper limit value is set to a predetermined second upper limit value that is smaller than the first upper limit value. The power supply apparatus according to claim 1, wherein the control circuit changes the upper limit value according to the output voltage of the power storage device. The power supply apparatus according to claim 1, wherein the control circuit changes the upper limit value according to the output voltage of the power storage device and the output current of the power storage device. The current limiting circuit includes a voltage conversion circuit that converts the output voltage of the power storage device into a specified set voltage having a different voltage value and outputs the converted voltage.
The power supply apparatus according to claim 1, wherein the control circuit changes the upper limit value according to the set voltage. The power supply apparatus according to claim 6, wherein the control circuit further changes the upper limit value according to the output voltage of the power storage device after setting the upper limit value according to the set voltage. . The control circuit determines that the power storage device is in a deteriorated state when the output voltage of the power storage device becomes a predetermined voltage or less despite the control circuit changing the upper limit value. The power supply device according to any one of claims 1 to 7. The resistance value of the internal resistance of the electricity storage device increases with the deterioration of the electricity storage device,
When the resistance value of the internal resistance is smaller than a predetermined deterioration threshold, even if the current value of the output current of the power storage device becomes equal to the set upper limit value, the output voltage of the power storage device is the predetermined value. The power supply device according to claim 8, wherein the upper limit value is set so as to be higher than a voltage.

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