JPS5863040A - Battery charging method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for charging a rechargeable secondary battery (hereinafter simply referred to as a battery). The present invention provides a new charging method that enables fast charging.

The demand for secondary batteries has increased with the increase in the number of portable boat-tab μ devices, and the power source for the l-tab μ video tape recorder (hereinafter referred to as YrR), which requires a relatively large current, is
Most of them use secondary batteries. Votab Ivv
'The secondary batteries used in the TR are based on past usage results.
Sealed lead-acid batteries (PB batteries) are common, but PB batteries aim to be smaller and lighter in terms of weight and volume.
2 devices are at a disadvantage. On the other hand, sealed nickel μ-cadmium batteries (NiCd batteries) have very low internal resistance, so they have excellent discharge characteristics at large currents, stable characteristics over a relatively wide temperature range, and other advantages. Many recent Vota 13 devices tend to use NiCd batteries because they can be easily charged quickly and have a charge/discharge cycle life of 300-500 times or more.

Rapid charging methods for NiCd batteries can be roughly divided into constant voltage charging methods and constant current charging methods. A typical constant voltage charging method is the joggle charging method, in which the battery is charged with a large current until the battery voltage reaches a predetermined value, and when the battery voltage reaches a predetermined value, the interrupted pulse-like charging is resumed with current. In this method, the charging current is reduced in response to a small voltage increase in the battery voltage. This method has the advantages of efficient rapid charging and the ability to prevent overcharging, but on the other hand, it requires a highly sensitive voltage switch and a high frequency converter, making the circuit complex, and it requires a pulsed charging current. It has drawbacks such as the need to seed the noise hanging in the air for use, and the need for a line filter to prevent noise from being superimposed on the power supply fins.

On the other hand, with the constant current charging method, in recent years, with the advancement of semiconductor technology, high performance transistors and operational amplifiers have become available at low cost, so it is possible to construct a constant current circuit with a simple circuit. This charging method is valued for its advantages such as not requiring noise countermeasures, which are a problem with the Zilog V charging method, since it handles such a large amount of current.

A typical constant current charging method is a method commonly referred to as a V-taper one-way method. This method charges the battery with a fairly constant large current until the battery voltage reaches a predetermined value, and stops charging with the large current when the battery voltage exceeds the predetermined value. This is a relatively efficient fast charging method that reduces the charging current according to the CR discharge curve.

Before explaining the present invention in detail, first, a V-taper type charging method will be explained. Figure 1 shows a charging pattern using a V-taper type, and Figure 2 shows a specific circuit example for obtaining the charging characteristics shown in Figure 1. In Figure 1, the horizontal axis shows charging time, and the vertical axis shows charging time. shows the battery voltage and charging current.

When a sufficiently discharged battery is charged using the V taper method, the charging current shows a change shown by i, and the battery voltage shows a change shown by ma.

During a period from time t to t8 at the initial stage of charging, constant current charging is performed with a relatively large current corresponding to the battery capacity IC.

At this time, the battery voltage gradually increases as charging progresses,
When the charging capacity reaches around α7c, the battery voltage increases rapidly. If charging is continued in this state with a large current around lc, the pressure inside the battery and the battery temperature will rapidly increase due to the generation of gas.

Sealed NiCd batteries are usually equipped with a safety valve, so they will not explode even if the internal pressure rises abnormally.
However, once the safety valve is activated and gas is released, the battery capacity deteriorates. In addition, continuous overcharging due to large currents can cause abnormal temperature rises and explosions due to ignition of hydrogen gas, so it is absolutely necessary to avoid using unreasonable methods.

Voltage is the factor that detects when the battery is fully charged.

It is limited to three things: temperature and internal pressure. Detecting internal pressure requires a pressure detection element, and an inexpensive detection method has not yet been realized.The generally widely used method is the voltage detection method, but in addition to this method, a temperature detection method is also used. be done. The purpose of temperature detection at this time is to change the detected voltage Vpay in accordance with changes in ambient temperature. Since the temperature detection method is different from the gist of the present invention, detailed explanation will be omitted here.

In FIG. 1, the charging current is gradually decreased along the CR discharge curve for 1 hour and 1° after the point at which the battery voltage reaches the control start voltage v(, that is, time t). Set the control start voltage MC to a safe voltage that will not cause the internal pressure and temperature of the battery to rise abnormally.If the CR discharge curve is set too steeply, it will take a long time to reach full charge, but if it is set too slowly, it will take a long time to reach full charge. 1, the subsequent charging current causes the battery voltage to rise above the control start voltage MAC.

The charging current after 0 o'clock opening t is set so that the battery voltage after the α discharge curve dtt is below the control start voltage VC and the curve is as slow as possible. Also, set the current value below Qlc, which will not cause abnormality to the battery.

If the charging current is set as explained above, rapid charging is possible in a relatively short time.

Next, a specific circuit example for realizing the charging pattern shown in FIG. 1 will be explained using FIG. 2. In Figure 2, (1)
1 indicates a battery, for example, 10 batteries are connected in series. (No is a constant current charging circuit, and the battery is charged with a constant current for the time shown in FIG. The current flowing through the battery α) is detected as a voltage drop across the resistor R7, which has a relatively low value (for example, 1Ω), and the charging current is adjusted so that the voltage value at the 0 point is equal to the reference voltage value at the 0 point. The transistor Ql controls the charging initial stage t, ~t
A period of 1 is an OFF state. Therefore, the reference voltage at point (c) is a value obtained by subtracting the voltage drop across diode D1 from the potential at point 0 determined by the division ratio of resistors R2 and R3. In addition.

Here, the resistance pair is the value of the enemy ship, 1, resistance R2 and R3
Since it takes several values, the influence of the resistance R1 has been omitted in the explanation.

The voltage detection circuit A (3) is a circuit that detects the voltage of the battery, and the voltage characteristic shown in FIG. 1 is outputted at the zero point. Voltage detection circuit B (4) is a Schmitt circuit with hysteresis characteristics (0 point output requires time t,
A voltage L01t is output during a period of ~t1.

Therefore, transistor Ql is in an OFF state. (C)
When the battery voltage at the point reaches the control start voltage maC, the voltage at the output point ω of the voltage detection circuit B (4) becomes a High voltage.
.

Transistor Q1 is turned on. At this time, assuming that the collector-emitter saturation voltage of the transistor Ql is zero, the potential at point 06 is determined by the parallel resistance value of the resistors R3 and R4 and the division ratio of the resistor RZ.

The potential at the zero point at this time is set so that the output current of the constant current charging circuit (g) is approximately αIC. That is, the charging current value after time t is determined. Transistor Q1
is ONI, and from time t1 to 1,1, the potential at the 0 point becomes lower than the potential at the peak point. This is because the potential at point 0 (b) drops immediately when fungistor Ql is in the ON state, but the potential at point 0 is determined by the amount of charge accumulated in capacitor CI, and Assuming that the input impedance of the non-drop, constant current charging circuit (21) is nearly infinite, the charge stored in the capacitor Ct is discharged only through the resistor pair.

Since the charging current to the battery is determined by the potential at point (c),
The charging current between time t1 and t8 gradually decreases in accordance with the discharge characteristics of C1 and R1. If the potential at point (C) reaches a potential that is lower than the potential at point 0 by the voltage drop of diode D1, from then on (the potential at point 6 becomes constant, and 1=the subsequent current value is set.

Note that the battery voltage after time t3 is stabilized at a potential lowered by a certain amount from the control start voltage MAC. At this time, in order to prevent the voltage at the output point ω of the voltage detection circuit B (4) from becoming a LOW potential again, the circuit B (4) is provided with a hysteresis characteristic, so that the voltage at the output point (D) becomes a LOW potential. The input voltage V and μ for this purpose is set to 1, for example, to the potential vh shown in FIG.

The above is an example of charging/<turn and a specific circuit of the V taper one-way type. This method has advantages such as being able to handle continuous charging current with a relatively simple circuit configuration and being able to perform relatively efficient rapid charging using CR discharge characteristics. It has its drawbacks.

The first problem is that it is not possible to recharge a battery that has undergone a small discharge. As already explained, if the CR discharge curve shown in FIG. 1 is made steep, it will take a long time to reach full charge.

At#) If it is made slow, the battery voltage after t1 will rise above the control start voltage mac, so the battery voltage after tt will be below the control start voltage mac9, and the curve will be as slow as possible. It is set to be.

However, what is the relationship between charging current and battery voltage after %t1?

It changes in relation to the battery's charging history up to that point.

For example, when recharging a battery that has been fully discharged to about x-hw LOV, the charging pattern shown in Figure 1 will be used. When a battery in a charged state is forcibly recharged, the charging pattern shown by the solid line in FIG. 3 is obtained. Third
In the figure, the voltage of the battery forcibly started to be recharged at 1 hour to suddenly rises and reaches the control start voltage MAC in a short time. At this point, the voltage detection circuit B (4
) is activated, and the charging current decreases along the CR discharge curve shown by the solid line il. However, when recharging a battery that is close to fully charged, α
Since the discharge curve 1m is too slow, the battery voltage does not drop immediately, but changes as shown by the solid line v1. At this time, the battery voltage increases beyond the safe voltage, and the internal pressure of the battery also increases. As a result, the safety valve will operate and the battery capacity will deteriorate. When recharging a battery that is close to fully charged, it is sufficient to use the steep CR discharge curve shown by the broken line i.
At this time, it is possible to obtain a characteristic that the change in battery voltage does not exceed the control start voltage C, which is indicated by the broken line M and N. However, in the conventional (1) taper-type charging method, it is not easy to change the steepness of the CR discharge curve depending on the discharge history. Therefore, as mentioned above, the conventional charging circuit has a voltage detection circuit B! 417 hysteresis characteristics, and a battery that is close to fully charged is not recharged with a large current, but this method is inconvenient for those who actually use the battery, and the battery is not fully charged. Although there are cases where the device is operated until the battery is fully discharged, it is often necessary to recharge the battery in preparation for the next operation after operating the device for a suitable period of time. Also, if the battery is left unused for a long time, the remaining charge of the battery will decrease due to natural discharge, but when recharging the battery at this time, please discharge it sufficiently and then recharge it. There was an obvious inconvenience to it.

The second problem is the setting of the potential ma shown in FIG.

This potential ma is the potential that determines whether or not to recharge the battery with an initial large current when the battery is set in a charger. The battery voltage changes depending on the remaining charge.

Therefore, the higher the electric potential h is set, the more the battery with a large amount of remaining charge, that is, the battery that is close to a full charge, can be completely recharged.

However, in reality, potential 1 cannot be set to a low value for safety reasons.
This is because, as the set values of are different, if the potential mah is set according to the characteristics of a given battery, there is a risk of overcharging depending on the battery as described in the first problem section. If the electric potential h is set to a low value, it has the disadvantage that only batteries with a small remaining charge can be recharged.

The third problem is the setting of the CR discharge curve. As already explained, the CR discharge curve is not steep.

The slope is set to be gentle enough to prevent overcharging. However, considering the buffiness of the battery, the CR discharge curve is set to be a steep curve that will not cause overcharging for safety reasons. This means that it takes longer to fully charge the battery. This also means that the charging time required to reach full charge varies greatly depending on the battery. This is because the charging current after the CR discharge curve is set to a low current below (llc), so if the rated capacity of the battery is slightly increased, the charging time due to the low current will be greatly increased.

By combining a constant current charging circuit and a constant voltage charging circuit, the present invention is capable of recharging regardless of past charging/discharging current amounts, can also be used as an overcharge prevention circuit, and can prevent buffing of battery characteristics. It is possible to automatically set a charging current decreasing curve corresponding to the above-mentioned CR discharge curve according to the amount of charge, and it is possible to complete charging efficiently in an extremely short time compared to the conventional V-taper type. It has the following characteristics.

The present invention will be described in detail below with reference to one drawing. Figure 4 shows
A charging pattern when a constant current charging circuit and a constant voltage charging circuit are used in combination is shown. Constant current charging is started at time t, and the current value at this time is indicated by i$.
The battery voltage V gradually increases during the constant current charging period and reaches the control start voltage MAC.

After 6 hours t8, where the time at this time is tl, if you switch to the constant voltage charging circuit and control the charging circuit so that the battery voltage is always constant, the charging current at that time will be ~1
Takes the change indicated by @. At the time of tl, the battery is not yet fully charged, and if a fully charged state is defined as 100%, the amount of charge is about 1, for example, 80%. When constant-voltage charging is performed, the charging current after t decreases according to the amount of charge up to that point, and the charging current force E is constant, which is indicated by ta.
If the current value is less than the current value indicated by 1, the battery voltage will decrease compared to the control start voltage maC, and if it is thicker, the battery voltage will increase. The charging current is current value I.

becomes the minimum value. Let the time at this time be ts. It has been confirmed through experiments that the battery reaches a fully charged state close to 100% at the minimum point of the charging current during the constant voltage charging period. This phenomenon is not related to battery variations or the amount of charge remaining before recharging.

After time ts, when the fully charged battery is continuously charged by the constant voltage circuit, the battery voltage increases along the curve indicated by 1. This is because the temperature of the battery rises and chemical reactions become active. The increase in charging current after t- is
Initially it is gradual, but it gradually increases sharply. If charging is continued in this state, the pressure inside the battery will increase due to the generation of gas, the safety valve attached to the sealed NiCd battery will operate, and the battery capacity will deteriorate due to the release of gas.

Therefore, as will be described later, initial constant current charging is performed, and when the battery voltage reaches the control start voltage MAC, the circuit is switched to a constant voltage charging circuit, and the minimum value of the charging current during the constant voltage charging period is detected and charging is performed. If a configuration is adopted in which the battery is stopped, extremely efficient charging can be performed in a short period of time.

Next, a specific circuit of the present invention will be explained. FIG. 5 shows an embodiment of the present invention, and the same symbols as in FIG. 2 have the same functions. FIG. 6 shows a charging pattern when the specific circuit example shown in FIG. 5 is used.

In FIG. S, at the initial stage of charging, the voltage at the output terminal ω of the voltage detection circuit C (5) and the voltage at the output terminal @ of the current control circuit (6) are at Lot potential. Therefore, transistors Q1 and 02 are in the OFF state. At this time, the charging current of the constant current charging circuit (2) is determined by the potential at the point O, which is determined by the division ratio between the resistors R2 and R3. During the constant current charging period, the battery voltage gradually increases. The battery voltage is output to the output terminal ω via the voltage detection circuit ACIII. The voltage detection circuit C (II is a VYU1MITSU circuit that generates a voltage at its output terminal ωKH1GK when the voltage of the battery becomes equal to or higher than the control start voltage 70) does not have the J'sIl:ST9V characteristic.

Therefore, when the battery voltage falls below the control start voltage macQ, the transistor Q2 is turned on.
state. Assuming that the collector-emitter voltage vC when transistor Q2 is completely turned on is zero, the potential at the 0 point at this time is the difference between resistor RIO and resistor R3, which are relatively small compared to resistor R3. Parallel resistance value and resistance R
The potential is determined by the division ratio of 2.

At this time, the charging current to the battery decreases. When the charging current decreases, the battery voltage decreases by 9, and as a result, the voltage at the output terminal ω of the voltage detection circuit C(6) becomes a LOW potential. Therefore, transistor Q2 is turned off, the charging current increases again, and the battery voltage also rises. Since the transistor Q2 is actually used in an unsaturated state and operates as a variable resistor, this operation is actually performed continuously, and the current value l between t1 and t1 shown in FIG. decide. That is, the charging current at time t1 is an open μm system determined by resistors R2 and R3, but the charging current between time t8 and t is determined by voltage detection circuit A (frame, voltage detection circuit C ( Il,
) A closed loop control system with negative feedback is formed by the fungistor Q2, and during this period it operates as a constant voltage charging circuit.

The details of the current control circuit (81 will be described later), but when the charging current during the constant voltage charging period of this circuit (61) becomes the minimum, the voltage at the output terminal ω becomes aHigh voltage.

One of the voltages at the output terminal ω is input to the voltage detection circuit C(6), and the other is input to the transistor Q1. Output end 0
When the voltage is a high voltage, the output terminal ω of the voltage detection circuit C(6) is forced to a LOW potential regardless of the battery voltage at the 0 point. Therefore, transistor Q2 is turned off. On the other hand, since the fungistor Q1 is in the ON state at this time, assuming that the potential between the collector and emitter is zero, the potential is 0.
The potential at the point is determined by the parallel resistance value of resistors R4 and R3 and the resistor R2.
It is determined by the division ratio. The current value at this time is shown in Figure 6.
This is the current value indicated by 1, and is set to a low current value below ale that allows continuous charging.

Since the charging current is rapidly reduced after time tl, the voltage of the battery is also reduced as shown in FIG. 6, and no abnormal voltage/temperature or pressure increases occur.

Also, until now, when the minimum value of charging current was detected.

We have explained this formula for rapidly reducing the charging current value from 1 to 11 as shown in Fig. C, but the method is as follows: 1. There is no need to suddenly decrease the charging current value (it is also possible to use a method of gradually decreasing the charging current using the CR discharge curve. The circuit configuration at this time is the diode D1 shown in Fig. 2,
A resistor R1 and a capacitor CI are added to the circuit shown in FIG.
It is sufficient to adopt a configuration in which the transistor Q2 is connected through O.

After the current control circuit +61 Fi and the output terminal V once output the H1gh voltage, that state is maintained. Therefore, when recharging a new battery, the current control circuit (8)
The battery may be reset automatically, or a manual reset button may be pressed when recharging.

FIG. 7 shows charging patterns when recharging batteries with different charging materials. The charging pattern when fully discharged and recharged with a large current shows the voltage change V and the charging current change i, shown by the solid line in FIG. 7. This characteristic has already been described in detail.

When the battery is recharged, the charging pattern changes as shown by the dashed line in FIG. In the initial stage of charging, charging is performed with a large current I· near the rated capacity 111c, and during this period the battery voltage rises rapidly. When the battery voltage reaches the control start voltage MAC, the charging current decreases rapidly as shown by the stone. The decreasing curve is automatically determined so that the battery voltage remains constant, and varies depending on the remaining charge before recharging, but even at this time, the current decreases! Charging is completed at the minimum point of 1°. Therefore, the current 1. Detect the minimum value of and change the charging current to 1. If the current value is changed to less than (ie) indicated by □, it is possible to recharge even a battery with a small amount of discharge.

Next, a sample circuit configuration example of the current control circuit (6) shown in FIG. 5 will be described. The current control circuit (61, as already explained, is a circuit that detects the minimum value of the charging current during the constant current charging period.In practice, it is not necessary to strictly detect the minimum value of the charging current; :.

A value near the minimum value is sufficient.

Fig. 8 shows a specific circuit example of the current control circuit (IIOjgl). Fig. 9 shows the waveforms of each part in Fig. 8. In Fig. 8, the charging current is Voltage waveform (al W is input according to the voltage waveform (ml)
12 The circuit surface that can be used by using the terminal voltage of the resistor R7 shown in FIG. 5 is an oscillation circuit), which outputs a rectangular wave shown in FIG. 9 (6). Note that the oscillation circuit can also be replaced by rectangular wave shaping of the commercial power supply at home. Circuit 0 (11) and circuit 0 are path shaping circuits, so the path μ shown in Figure 9 and the following is Output.

Each of these paths ν can be easily formed using the rising edge or the rising edge of the output of the oscillation circuit.
The circuit (8) is a sampling μ-hold voltage circuit, which samples the input voltage waveform (O) at the output of the path shaping circuit (0), and performs sampling between each bus. Hoard the voltage. Therefore, the sump y hold circuit (8
6 circuits 111+ whose output waveforms (a2B, Fig. 9G) change as shown by dotted lines are voltage comparison circuits, and the input (a
Compare the voltage Vpels of l) and (at). The timing of comparison is only during the period when the output ■ of the path shaping circuit is at High voltage (11) (! Compare the second voltage level ν, and use the result as
-FF) (Input to 1:l.

The output of the voltage comparator circuit (9) outputs a LOW voltage when the potential at (at) is higher than the potential at (11) li during the positive pulse period indicated by @, and when the potential at (at) is higher than the potential at (a
When the potential is lower than l), outputs H1gh voltage @
(at)'7) Voltage and (s+2) voltage νpeν
As is clear from the diagram shown in FIG. 9, ω is reversed when the charging current is near the minimum point. Therefore,
By using the circuit configuration shown in FIG. 8, it is possible to detect the vicinity of the minimum value of the charging current. In addition, voltage comparator circuit II)
t) The output is not limited to the configuration that outputs 111gk voltage when the voltage level μ between (11) and (at) is reversed, but when the potential difference between (Maro 1) and at) is constant and becomes peμ A configuration that outputs a high voltage may also be used.
The output of 9-FF circuit- is the voltage comparator circuit (the output of 91 is H
When the voltage reaches the igh voltage, the I11gh voltage is output. Therefore, after detecting the vicinity of the minimum value of the charging current, a high voltage is output to the terminal (6) regardless of the battery voltage.
) is a reset switch to restart the operation.

Note that the circuit shown in Figure 8 is used when the battery voltage reaches the start of control. It starts operating when the voltage reaches the voltage max.

FIG. 10 shows a second specific circuit example of the current control circuit (6), and FIG. 11 shows waveforms at various parts in FIG. In FIG. 10, a voltage waveform (a
) is input. The voltage waveform ω is inverted and amplified by the inverting amplifier circuit 071, and its output Bs is shown in FIG.
It changes in the same way as the voltage waveform shown by fi. Diode D3
is for correcting the voltage drop caused by the diode D2. The diode D2 and capacitor tc2 are a peak hold circuit and hold the maximum value of the inverted voltage waveform. The 0 circuit whose output from the beak hoard circuit is indicated by a broken line (b2) in FIG. 11 is a voltage comparison circuit.
Compare the voltage level μ of (bl) and (b2).0If both inputs are the same -Vpe~, the output of the voltage comparison circuit -) is LO
The potential is W, and if the voltage difference exceeds a certain level, the potential becomes High. When the output (d) reaches the ILgh potential, the charging current is near the minimum value, so! ! With the circuit configuration shown in FIG. 10, it is possible to detect the vicinity of the minimum value of the charging current. When recharging a new battery, the charge on capacitor C2 can be discharged using a switch.

As is clear from the above explanation, according to the present invention, initial charging is performed using a constant current charging method, and when the battery voltage reaches the control start voltage, the method is switched to a constant voltage charging method, and when the charging current is near the minimum value. Since the charging current is detected and the charging current is rapidly reduced, it has various advantages.

The first advantage is that the degree of decrease in charging current during the constant voltage charging period automatically changes according to the battery's past charging and discharging history, so it can be fully charged in a short time and extremely efficiently regardless of the past history. The point is that it can be done.

The advantage of 1152 is that the charging current decreases once during the constant voltage charging period, and once it reaches a fully charged state, the charging current increases again as the temperature rises, so the vicinity of the minimum value of the charging current during the constant voltage charging period can be detected. If possible, it would be possible to know when the battery is fully charged.

The third advantage is that since the constant voltage charging method is used in combination with the constant current charging method, charging due to excessive current and overcharging can be prevented. Therefore, the battery can be recharged regardless of its past charging/discharging history.

Although a description of battery temperature compensation has been omitted here, a temperature rise in the battery is detected using an element such as a thermistor whose resistance value changes depending on the temperature.

It may be appropriate to suddenly reduce the charging current slightly before the charging current reaches the minimum value, but it does not go against the spirit of the present invention.

Alternatively, a method may be used in which a temperature rise is detected using an element such as the thermistor, and the minimum value of the charging current is detected based on the temperature rise.

[Brief explanation of drawings]

Figure 1 is a diagram of the conventional V-taper one-type charging pattern;
The figure shows the specific circuit contingency of the conventional V-taper one-way type, Fig. 3 shows the charging pattern when batteries with different charging and discharging history are charged by the conventional V-taper dynamic type, and Fig. 4 shows detailed explanation of the present invention. Figure 5 is a diagram showing a charging pattern when a constant current charging method and a constant voltage charging method are used together. The WiG diagram is a charging pattern diagram according to the present invention, FIG. 7 is a charging pattern diagram when batteries with different charging and discharging histories are charged using the charging method according to the present invention, and FIG. Figure 10 is a circuit diagram showing the second embodiment for detecting the minimum value of the charging current, Figure 11 is a waveform diagram of each part of Figure 8 of Figure 9, It is a waveform diagram of each part. a) - battery, (2) constant current charging circuit, 13) - voltage detection circuit A s fi + - voltage detection circuit C, (6) -
・・Voltage detection circuit〆, (8) - Sump ~ Hode circuit,
191-・Voltage comparison circuit, -1 oscillation circuit, fi1+U-
Basis inverting circuit, 0η...inverting amplifier circuit, fist-one peak μhold circuit, wire...voltage comparison circuit agent Yoshihiro Morimoto Fig. 8 11 Fig. 9---0(1r) <d ) Figure 1θ Figure 11 □・□Q(V') ------0(V)

Claims (1)

[Claims] L Charging is performed with a large current from the charging start point to the first battery voltage detection point, and after the first battery voltage detection point is detected, constant voltage charging is performed, and during the constant voltage charging period. A battery charging method characterized by detecting a minimum charging current and switching to low current charging that allows continuous charging. 2. Detecting that a first voltage corresponding to the charging current during the constant voltage charging period and a second voltage obtained by delaying the first voltage have become a certain voltage difference, and determining the minimum charging current. 2. The battery charging method according to claim 1, further comprising detecting a value. a The difference between the first voltage waveform obtained by inverting the voltage change corresponding to the charging current change during the constant voltage charging period and the output voltage of the maximum value holding circuit that holds the maximum value of the first voltage waveform is a constant value. 2. The battery charging method according to claim 1, wherein the minimum value of the charging current is detected by detecting that the charging current has reached the minimum value.