JPH08308103A - Hybrid power source - Google Patents

Abstract

PURPOSE: To suppress the fluctuation of the voltage applied across a load which occurs when the voltage of a capacitor fluctuates by controlling the ratio of the electric current from a battery to that from a large-capacitance capacitor by means of a current control circuit and establishing a specific relation between the time average values of the electric currents flowing to the load connected to a power source and flowing from the battery. CONSTITUTION: A hybrid power source is provided with a battery 1, large- capacitance capacitor 2, and current control circuit 4. The circuit 4 controls the ratio of the electric currents flowing from the battery 1 and capacitor 2. The hybrid power source controls the electric currents Ia (t) and Ib (t) flowing to a load 3 connected to the power source and flowing from the battery 1 so that σb <σa can be obtained when σa =(ξT<b> Ta (Ia(t)-Iam)<2> dt)/Iam<2> /(Tb-Ta) and σb =(ξT<b> Ta (Ib(t)-Ibm)<2> dt)/Ibm<2> /(Tb-Ta) during periods of time Ta and Tb, where Iam and Ibm respectively represent the time average values of the currents Ia (t) and Ib (t). Therefore, a power source having a high energy efficiency can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hybrid power source which is excellent in energy density, output density and life characteristics and has high energy utilization efficiency.

[0002]

2. Description of the Related Art Batteries are generally divided into primary batteries that can be discharged only once and secondary batteries that can be repeatedly charged and discharged.

The battery can be used as a constant voltage source, and the voltage across the battery is kept constant during discharging.

Further, a large capacity capacitor can be charged and discharged many times, and its life characteristics are generally superior to those of a battery.
In addition, it has excellent output density and can draw a large current instantaneously, but the voltage across both ends decreases proportionally as it discharges, and the energy density is 1/10 to 1 of that of a battery.
It is 1/00.

Therefore, the large-capacity capacitor has a relatively small capacity and is mainly used in a backup system or the like in which the voltage drop does not pose a problem.

Although a battery has a certain fixed capacity, all of it cannot be extracted as energy, and its utilization efficiency generally depends on its discharge current. The larger the discharge current, the smaller the utilization efficiency tends to be. is there.

Even if the discharge currents have the same time average, when the discharge currents change with time, the utilization efficiency becomes smaller than that of constant current discharge, and the larger the rate of change, the smaller the efficiency. is there.

Further, in the case of a secondary battery, the cycle life becomes shorter as the discharge current becomes larger or the time fluctuation thereof becomes larger.

Large-capacity capacitors such as electric double-layer capacitors have a smaller change in utilization efficiency than a battery due to discharge current and time variation thereof, and generally have a long cycle life, but at present, per unit volume, per unit weight. The energy densities of 1 and 2 are both 1/10 or less as compared with the battery.

Therefore, by combining a battery with a high energy density and a large-capacity capacitor with excellent output density and life characteristics, the utilization efficiency does not change as much as the battery with respect to the discharge current and its variation with time, A power source with excellent density and life characteristics and high energy utilization efficiency can be achieved.

[0011]

It is desirable to use a battery at a constant current in terms of utilization efficiency and life. However, the load current generally fluctuates in many cases. Therefore, it is conceivable to connect the capacitor and the battery in parallel to absorb the fluctuation. However, in this case, the voltage applied to the load changes due to the decrease in the voltage of the capacitor, which is not preferable.

The present invention pays attention to such a problem, and corresponds to a battery and a capacitor with respect to a load current, and a discharge current of the battery to be applied to the load when the load current is large and a load when the load current is small. It is an object of the present invention to provide a hybrid power source in which the sum of the discharge current of the battery flowing through the capacitor and the sum of the charge current of the battery to the capacitor is controlled as close as possible.

[0013]

The present invention is to achieve the above object, and comprises a battery, a large-capacity capacitor, and a current control circuit, wherein the current control circuit is a battery and a current from the large-capacity capacitor. Of the current Ia (t) flowing to the load connected to the power source and the current Ib (t) flowing from the battery by controlling the ratio of Ia, Ibm, and between time Ta and Tb, σ _a = (∫ _Ta ^Tb (Ia (t) -Iam) ² dt) / Iam ² / (Tb-T
a), σ _b = (∫ _Ta ^Tb (Ib (t) -Ibm) ² dt) / Ibm ² / (Tb-Ta), control is performed so that σ _b <σ _a It is a hybrid power source.

Further, it is characterized by a specific circuit configuration that achieves the above conditions.

[0015]

[Operation] The use efficiency of the battery is improved by smoothing the time change of the current flowing to the load with the large-capacity capacitor,
Improves power density and life characteristics.

Further, by connecting a resistor in series to the battery, the DC resistance of the battery when viewed from the load becomes larger than the DC resistance of the large-capacity capacitor, and the current flowing from the battery flows with respect to the time fluctuation. The time variation of the current becomes small. In this case, since only a resistor is used for current control, it can be used for controlling a relatively large current, but there is a disadvantage that energy loss due to heat generation of the resistor becomes large.

Further, by connecting the battery, the large-capacity capacitor, and the resistor in series by the relay, it is possible to increase any one of the DC resistances of the two when viewed from the load. According to this method, when a relatively large current flows through the load, the large-capacity capacitor mainly supplies the current, and when a relatively small current flows, the battery mainly supplies the current to the load, and the battery also charges the large-capacity capacitor. This makes it possible to reduce the time variation of the current flowing from the battery with respect to the time variation of the current flowing in the load. In this case, since the current flowing through the battery can be controlled by the relay depending on the magnitude of the current flowing through the load, the time fluctuation of the current flowing through the battery can be made smaller, but the energy loss due to the heat generation of the resistor and the current when switching the relay Has the disadvantage that it changes discontinuously.

Further, by controlling the charging and discharging currents to the large capacity capacitor, the current flowing to the load from each of the battery and the large capacity capacitor can be controlled arbitrarily, so that the current flowing to the battery is made constant. It becomes possible, and the utilization efficiency becomes almost the same as the case of constant load discharge, and the utilization efficiency becomes maximum. However, since the current control mainly uses semiconductor elements, there is a limit to the control of large current.

[0019]

【Example】

Example 1 FIG. 1 shows a schematic diagram of Example 1. When the current flowing through the load 3 changes with time, the current control device 4
Causes the current flowing from the battery 1 to be smoothed, and the difference is discharged or absorbed by the large-capacity capacitor 2. More specifically, when the current flowing through the load 3 is large, the current is mainly supplied from the large-capacity capacitor 2, and when the current flowing through the load 3 is small, the current is mainly supplied from the battery 1,
At the same time, the large capacity capacitor 2 is charged from the battery 1.

As an example of the current control device 4 that achieves this, the resistors (battery external resistor 6 and charge control resistor 7) were used in the first embodiment, but in the other cases, a relay is used (second embodiment) and semiconductors. There are cases where an element or the like is used (Example 3). Hereinafter, the current control device 4 of the first embodiment will be described.

Current is supplied to the load 3 from the battery 1 and the large-capacity capacitor 2. Since the voltage across the large-capacity capacitor 2 decreases in proportion to the discharge amount, the D / D converter 5 is connected in series. A constant voltage is applied to the load 3 regardless of the amount of discharge. On the contrary, by utilizing this voltage drop, the charge control resistor 7 is arranged between the battery 1 and the large-capacity capacitor 2, and the current corresponding to the discharge amount of the large-capacity capacitor 2 is supplied to the battery 1
Supplied from

The battery 1 and the large-capacity capacitor 2 have internal resistances Rbi and Rci, respectively.

Now, assuming that the battery external resistance 6 (resistance value Rb) is connected in series to the battery 1 and the current flowing to the load 3 is Ia (t) and the current flowing from the battery 1 is Ib (t), the respective times are In the steady state, the fluctuations δIa and δIb are δIb = δIa × Rci ÷
It becomes (Rbi + Rb). That is, by connecting the battery external resistance 6 to the battery 1, the time variation of the current flowing from the battery 1 can be suppressed with respect to the time variation of the current flowing to the load 3.

Example 2 FIG. 2 shows a schematic diagram of Example 2. The current detector 8 is connected to the load 3 in series, and the load 3
The time average Iam of the current Ia (t) flowing to
The arithmetic circuit 9 always compares Ia (t) with Iam.

When Ia (t)> Iam, the power is mainly supplied from the large-capacity capacitor 2 to the load 3 by switching the relay 10 connected to the arithmetic circuit 9 to the B side. The ratio of the currents from the battery 1 and the large-capacity capacitor 2 at this time is determined by the value of the control resistor 11.

When Ia (t) <Iam, the relay 10 is turned on.
By switching to the side, power is mainly supplied from the battery 1 to the load 3, and when Ia (t)> 0, the battery 1 outputs Ia (t)
When <0, the large-capacity capacitor 2 is also charged from both the battery 1 and the load 3. A D / D converter 5 is connected in series to supply electric power from the large-capacity capacitor 2 to the load 3, and a constant voltage is applied to the load 3 regardless of the amount of discharge.

As described above, the relay 10 and the control resistor 1
By using 1, the time variation of the current flowing from the battery 1 can be suppressed with respect to the time variation of the current flowing to the load 3, and the current utilization efficiency of the battery 1 can be improved.

The second embodiment is superior to the first embodiment in that the battery external resistor 6 is not provided, so that the energy loss due to the resistance is small and the relay 10 can perform more detailed current control. Further, the inferior point is that since the contact type relay is used, the current changes discontinuously at the time of switching, and the maximum value of the controllable current is small.

Example 3 FIG. 3 shows a schematic diagram of Example 3. In this circuit, in order to reduce the time variation of the current from the battery 1, the load current is checked and the current is controlled by the load current.

The current detector 8 is connected to the load 3 in series, and the arithmetic circuit 9 which presets the time average Iam of the current Ia (t) flowing to the load 3 or obtains it by measurement compares Ia (t) with Iam. Always do.

When Ia (t)> Iam, the discharge current control circuit 13 connected to the arithmetic circuit 9 causes the large-capacity capacitor 2 to
A current is supplied only by Ia (t) -Iam, and the charging current control circuit 12 does not charge the large-capacity capacitor 2.

When 0 <Ia (t) <Iam, the discharge current control circuit 13 does not discharge the large-capacity capacitor, and the charge current control circuit 12 discharges only Iam-Ia (t) from one battery 1 to the large-capacity capacitor. Charge to 2.

When Ia (t) <0, the discharge current control circuit 13 does not discharge the large-capacity capacitor 2, and the charge current control circuit 12 causes Iam from the battery 1 and-from the load 3.
The large capacity capacitor 2 is charged by Ia (t).

A D / D converter 5 is connected in series to supply electric power from the large-capacity capacitor 2 to the load 3, and a constant voltage is applied to the load 3 regardless of the amount of discharge.

As described above, by using the charge current control circuit 12 and the discharge current control circuit 13, the current flowing from the battery 1 can be made constant at Im and the current utilization efficiency can be improved.

The advantage of the third embodiment over the first and second embodiments is that since no resistor is used, the energy loss is small, the time variation of the current from the battery 1 can be reduced to 0, and the operation circuit 9 The point is that the current can be controlled arbitrarily. Further, as a disadvantage, a semiconductor element such as a Darlington transistor must be used at least in the final stage for both the charge current control circuit 12 and the discharge current control circuit 13, so that the maximum controllable current is small. Is.

In the hybrid power sources in the above three examples, the cyclic load current as shown in FIG. 4 (this is one cycle) was generated by the electronic load device, and its discharge characteristic was measured. The cycle in this figure is 50 seconds. Further, the battery 1 is an AA Ni-Cd battery (nominal capacity 2200 mAh, internal impedance 13 mΩ at 1 kHz), and the large-capacity capacitor 2 is an electric double layer capacitor (nominal capacity 100 F,
An internal resistance of 8 mΩ) was used.

In addition, as a conventional example, the discharge characteristic of only the battery 1 was also measured. FIG. 5 shows the time variation of the current flowing from the battery 1 during one cycle. In this figure, (a)
Shows the current change of the battery in the conventional configuration, and (b) (c) (d) show the current load of the capacitor and the battery in the configurations shown in Examples 1, 2 and 3, respectively. It shows the current that charges the capacitor. here,
As the battery discharge current up to 10 seconds and the battery discharge current (charge current to the capacitor) after 10 seconds become closer, the battery efficiency or life is improved.

From this figure, it is found that the variation of the negative overcurrent is equal to the current flowing from the battery 1 in the conventional example, but the time variation (that is, σb) of the current flowing from the battery 1 is small in the embodiment. Recognize. Using this periodic negative overcurrent, the following charge / discharge test was conducted. Battery 1 was subjected to constant current charging at 200 mA for 15 hours. The voltage across battery 1 after completion of charging was about 1.4V.

Next, discharging is performed by the periodic negative overcurrent shown in FIG. 4, the discharging is terminated when the voltage across the load 3 reaches 0.7 V, and the current flowing through the load 3 during discharging is changed with time. Integrated value (this is referred to as current utilization capacity), product of current flowing through load 3 and voltage across load 3 at that time integrated over time (this is referred to as power utilization capacity), and discharge current of battery 1. [Sigma] b was calculated from the change over time (data in FIG. 5 and the like). Further, the constant current charge and the discharge by the periodic negative overcurrent were regarded as one charge / discharge unit, and the ratio of the current utilization capacity before and after this was performed 100 times (this is referred to as the deterioration rate) was obtained.

The results are shown in (Table 1). In Example 1, the values of the battery external resistance 6 and the charge control resistance 7 were the same, and in Table 1 the values are shown as the control resistance. Further, both the charging current control circuit 12 and the discharging current control circuit of Example 3 used Darlington transistors in the final stage.

[0042]

[Table 1]

From this result, the following can be said. (1) The current utilization capacity increases as σ _b decreases.

(2) In the power supplies of Examples 1 and 2, as the value of the control resistance increases, σ _b also decreases and the current utilization capacity increases, but the power utilization capacity also decreases accordingly.

(3) Even with the same σ _b , the power usage capacity of 2 is larger than that of the first embodiment. (4) In the third embodiment, the power usage capacity does not decrease even though σ _b decreases.

(5) The deterioration rate decreases as σ _b increases. Therefore, σ _b can be reduced by the methods of Examples 1 to 3, and as a result, current utilization efficiency, power utilization efficiency, and life characteristics are improved as compared with the battery alone.

[0047]

As described above, according to the present invention, it is possible to achieve a power source having excellent energy density, output density and life characteristics and high energy utilization efficiency.

[Brief description of drawings]

FIG. 1 is a block configuration diagram of a hybrid power supply according to an embodiment of the present invention.

FIG. 2 is a block diagram of a hybrid power source according to another embodiment of the present invention.

FIG. 3 is a block diagram of a hybrid power supply according to another embodiment of the present invention.

FIG. 4 is a diagram showing a variable load pattern.

FIG. 5 is a diagram showing a variation pattern of current flowing from a battery.

[Explanation of symbols]

 1 Battery 2 Large Capacitor 3 Load 4 Current Control Circuit 5 D / D Converter 6 Battery External Resistance 7 Charge Control Resistor 8 Current Detection Section 9 Arithmetic Circuit 10 Three-way Switch 11 Control Resistor 12 Charge Current Control Circuit 13 Discharge Current Control Circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akihiko Yoshida 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Atsushi Nishino 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (6)

[Claims] 1. A hybrid power supply comprising a battery, a large capacity capacitor, and a current control circuit, wherein the current control circuit controls the ratio of the current from the battery and the large capacity capacitor, and a load connected to the power supply. To the current Ia (t) flowing from the battery and the current Ib (t) flowing from the battery to Iam, Ibm,
In addition, between time Ta and Tb, σ _a = (∫ _{T a} ^Tb (Ia (t) -Ia
m) ² dt) / Iam ² / (Tb-Ta), σ _b = (∫ _Ta ^Tb (Ib (t) -Ibm) ² d
A hybrid power supply characterized by controlling so that σ _b <σ _a when t) / Ibm ² / (Tb-Ta). 2. A resistor and a battery connected in series, a D / D converter and a large-capacity capacitor connected in series, and a load are connected in parallel, and a connecting portion between the resistor and the battery, and The hybrid power supply according to claim 1, wherein a connection portion between the D / D converter and the large-capacity capacitor is connected via a resistor. 3. When the internal resistances of the battery and the large-capacity capacitor are Rbi and Rci, respectively, and the value of the resistance connected in series between the battery and the load is Rb, Rbi + Rb> Rci. The hybrid power source according to claim 2. 4. A battery, a D / D converter and a large-capacity capacitor connected in series, and a load and a current detection unit connected in series are respectively connected in parallel via a three-way switch, and the battery 2. The connection part of the three-way changeover switch and the connection part of the D / D converter and the large-capacity capacitor are connected via a resistor, and the current detection part controls the three-way changeover switch. Hybrid power supply. 5. A battery, a discharge current control circuit connected in series, a D / D converter, a large-capacity capacitor, and a load connected in series and a current detector are connected in parallel,
2. The hybrid power supply according to claim 1, wherein the connection between the battery and the load and the connection between the D / D converter and the large-capacity capacitor are connected via a charging current control circuit. 6. A discharge current control circuit determines a current flowing from a large-capacity capacitor to a load based on a value of a current flowing through the load measured by a current detection unit, and a charging current control circuit determines a large current from the battery or both the battery and the load. The hybrid power source according to claim 5, wherein the charging currents to the capacitance capacitors are controlled respectively.