JP2003348763A - Charge control method - Google Patents

Abstract

(57) [Summary] PROBLEM TO BE SOLVED: To charge two batteries using one adapter.
When charging, preferentially charging one battery. SOLUTION: The first adapter is used by using one adapter (20).
And charging the second battery (50, 64).
Adapter voltage (Vcc) and first battery voltage
(V _BATT1) And the first battery
The difference obtained by subtracting the voltage of the battery is smaller than the specified voltage
In the meantime, the first battery is not charged and the second battery is not charged.
Charge the battery preferentially. The difference is larger than the predetermined voltage
When the threshold is high, the first battery is charged. The above prescribed
The voltage is 0.6V. The voltage of the first battery is
Voltage and the voltage of the second battery is higher than the reference voltage.
Precharge the first battery and charge the second battery
Charge. The charging current at the time of preliminary charging is the charging at the time of full charging
1/10 of the current. The reference voltage is 2.9V.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging circuit for charging a battery (secondary battery), and more particularly to a charging control method for controlling charging of two batteries connected to an adapter.

[0002]

2. Description of the Related Art A rechargeable battery charge control circuit of this type is a circuit for controlling charging of a rechargeable battery, and is interposed between an adapter and a rechargeable battery. This is a circuit for controlling the flowing charging current. The secondary battery, ie, a rechargeable battery, may be, for example, a lithium ion battery. Hereinafter, a conventional charge control circuit for a secondary battery will be described with reference to the drawings.

As shown in FIG. 1, a conventional charge control circuit 10 for a secondary battery is interposed between an adapter 20 and a secondary battery (lithium ion battery) 30 and is connected to the secondary battery 30 from the adapter 20. It controls the charging current I _BATT to flow.

Specifically, the adapter 20 generates an adapter voltage Vcc. The adapter 20 has an anode (cathode) 21 and a cathode (anode) 22, between which a charging control circuit 10 for a secondary battery described later is connected. That is, the secondary battery charge control circuit 10 is connected to the anode 21 of the adapter 20 by the charge control transistor TR1.
And a charging current sense resistor R1. The charge control transistor TR1 is a power transistor, and is configured by a p-channel field effect transistor. A resistor R2 is connected between the source and the gate of the charge control transistor TR1. Charge control transistor TR1, charge current sense resistor R1, and resistor R2
Is called a peripheral circuit of the charge control circuit 10 for the secondary battery. That is, the charge control circuit 1 for the secondary battery
0 and its peripheral circuits are connected between the anode 21 of the adapter 20 and the anode (cathode) 31 of the secondary battery 30.

[0005] The charge control circuit 10 for a secondary battery includes a VCC terminal, a CNT terminal, a CS terminal, a BAT terminal, and a GN terminal.
It has a D terminal. The VCC terminal is called a power supply terminal, and CN
The T terminal is called a control terminal. The GND terminal is called a ground terminal. The VCC terminal is connected to the anode 21 of the adapter 20 and the source of the charge control transistor TR1. C
The NT terminal is connected to the gate of the charge control transistor TR1. The CS terminal is connected to the drain of the charge control transistor TR1. The BAT terminal is a secondary battery 30
Are connected to the anode terminal 31. The charging current sense resistor R1 is connected between the BAT terminal and the CS terminal. The GND terminal is grounded.

Referring to FIG. 2, the charging control circuit 10 for a secondary battery will be described in detail in a simplified manner. The main functions of the secondary battery charge control circuit 10 are a constant current charging function, a constant voltage charging function, and a pre-charge switching function. The charging control circuit 10 for a secondary battery includes a constant current control circuit unit 11 that controls a constant current charging function and a constant voltage control circuit unit 12 that controls a constant voltage charging function.
And CN controlling the power transistor TR1
T control circuit section 12 'and precharge detection circuit section 1
And 3.

[0007] The constant current control circuit section 11 has a charge current sense.
Power is applied to keep the potential difference between both ends of the resistor R1 constant.
The transistor TR1 is controlled to charge the rechargeable battery 30 with a constant current.
It is a circuit for supplying electricity. The constant voltage control circuit unit 12
Battery voltage (battery voltage) V of secondary battery 30_BATTDetect
And this battery voltage V_BATTDoes not exceed a certain voltage
As described above, the power transistor TR1 is controlled to
This is a circuit for charging 0. Pre-charge detection circuit 1
3 is the battery voltage V_BATTIs detected, and the battery voltage V _BATTBut
When the voltage is 2.9 V or more (within the range of A2 in FIG. 3), the PNP type
The base potential of the bipolar transistor Q5 is threshold
Voltage and control the current. Also, reserve
The power detection circuit unit 13 detects the battery voltage V_BATTIs 2.9V or less
(Fig. 3, A1 range) PNP type bipolar tiger
The base potential of transistor Q6 becomes the threshold voltage.
Control the pre-charge current.

More specifically, the constant current control circuit 11 includes a constant current source CI1, an amplifier A1 connected to the CS terminal and the BAT terminal via buffers BUF1 and BUF2, respectively, for quadrupling the difference voltage, and a constant current source CI1. A source CI2, a CC amplifier A2 that compares a constant current charging reference voltage Vcl generated from a constant current charging reference voltage generating circuit, which will be described later, with an output of the amplifier A1, and an NPN that is turned on / off by an output of the CC amplifier A2. And a bipolar transistor Q1. The base of the NPN bipolar transistor Q1 is connected to the output terminal of the CC amplifier A2, and the emitter is grounded.

The CNT control circuit section 12 'includes an error amplifier A3 for comparing the constant current source CI3, the battery voltage V _BATT from the BAT terminal with the regulator voltage Vch output from the constant voltage control circuit section 12, and an error amplifier A3. And an NPN-type bipolar transistor Q2 that is turned on and off by the output of the amplifier A3. The base of the NPN type bipolar transistor Q2 is connected to the output of the error amplifier A3, the emitter is grounded, and the collector is connected to the CNT terminal. Thereby, constant current control (CC) and constant voltage control (CV) are performed.

The constant voltage control circuit section 12 has a Zener voltage V
a zener diode ZD1 for generating z, a constant current source CI4 connected between the cathode of the zener diode ZD1 and the VCC terminal, and a zener voltage Vz are supplied;
And a regulator circuit for generating the above-described regulator voltage Vch. The regulator circuit is a constant current source CI5
, A regulator amplifier A4, and resistors R5 and R6 connected in series. Regulator amplifier A4
Is connected to the cathode of the Zener diode ZD1, and the inverting input terminal is connected to the connection point of the series-connected resistors R5 and R6. The output of the regulator amplifier A4 is connected to resistors R5 and R5 connected in series.
6 to generate the regulator voltage Vch.

The precharge detection circuit 13 includes a Zener diode ZD2 for generating a Zener voltage Vz, a constant current source CI6 connected between the cathode of the Zener diode ZD2 and the VCC terminal, and a BAT terminal and a GND terminal. A resistor R connected in series via a buffer BUF2
7, R8, a constant current source CI7, and an amplifier A5 for comparing the Zener voltage Vz with the voltage at the connection point of the resistors R7 and R8.
And the constant current charging reference voltage generation circuit.

The constant current charging reference voltage generating circuit includes a first bleeder resistor R3, R4 and a second bleeder resistor R3 ', which are connected in series to divide the Zener voltage Vz.
R4 ', the first bleeder resistor (R3, R4) and the second
And a switching circuit for switching between the bleeder resistors (R3 ′, R4 ′). The switching circuit is a pair of PNP
Current mirror circuit comprising bipolar transistors Q3 and Q4, constant current source CI8, and constant current source CI8
And PNP-type bipolar transistors Q5 and Q6 connected in parallel between the power supply and the GND terminal. The base of PNP bipolar transistor Q5 is connected to the connection point of first bleeder resistors R3 and R4, and the base of PNP bipolar transistor Q6 is connected to second bleeder resistor R5.
It is connected to the connection point of 3 'and R4'. The base of PNP bipolar transistor Q6 is connected to the collector of PNP bipolar transistor Q3. PNP
The collector of the bipolar transistor Q4 is grounded via the NPN bipolar transistor Q7, and the base of the NPN bipolar transistor Q7 is connected to the output terminal of the amplifier A5 via the resistor R9.

Referring to FIG. 3 in addition to FIG. 1, a conventional charge control method using a conventional charge control circuit 10 for a secondary battery will be described. In FIG. 3, (A) shows the charging current I
The characteristics of _BATT, (B) is the battery voltage (battery voltage) V
_{The BATT} characteristic is shown, and the horizontal axis shows time t.

In the conventional charge control method, a charge current _IBATT is supplied to the secondary battery 30 from the adapter 20 through the charge control sense resistor R1 via the power transistor TR1. At this time, the charging control circuit 10 for the secondary battery performs charging in one of two modes, namely, a constant current (CC (constant current)) charging mode and a constant voltage (CV (constant voltage)) charging mode. .

In FIG. 3, a region A is a region where CC charging is performed, and a region B is a region where CV charging is performed. Here, description will be made assuming that the full charge voltage of the secondary battery 30 is 4.2V. The area A where CC charging is performed is divided into an area A1 where preliminary charging is performed and an area A2 where full charging is performed. The charging current at the time of preliminary charging is about 1/10 of the charging current at the time of full charging. When the battery voltage V _BATT is lower than 2.9 V, pre-charging is performed, and when the battery voltage V _BATT is higher than 2.9 V, full charging is performed. After CC charging, the battery voltage V _{BA TT} approaches full charge voltage (4.2 V), switching from CC charging (region of A) to CV charging (region of B). This CV
In charging, the charging current I _BATT is caused by the impedance of the secondary battery 30.

Then, as the voltage further approaches the full charge voltage (4.2 V), the charge current I _BATT decreases. When the voltage ΔV between both ends of the charging current sense resistor R1 reaches a full charge set value, charging is stopped inside the secondary battery charge control circuit 10.

Next, the operation of switching the charging current in the conventional charging control circuit 10 for a secondary battery will be described with reference to FIG.

The amplifier A5 of the precharge detection circuit 13 is
This is for monitoring the battery voltage V _BATT at the BAT terminal. More specifically, the BAT terminal is connected to the resistors R7 and R8 via the buffer BUF2. Therefore, the battery voltage V _BATT is _divided by the resistors R7 and R8, and the divided voltage is supplied to the non-inverting input terminal of the amplifier A5. On the other hand, the Zener voltage Vz is supplied to the inverting input terminal of the amplifier A5. The amplifier A5 compares the Zener voltage Vz with the voltage divided by the resistors R7 and R8.

The output of the amplifier A5 turns on / off a current mirror circuit composed of a pair of PNP-type bipolar transistors Q3 and Q4. Thus, the threshold voltage (constant current charging reference voltage) Vcl supplied to the inverting input terminal of the CC amplifier A2 of the constant current control circuit unit 11 is switched. By switching this threshold voltage Vcl, the constant current control circuit 1
1 controls two current values.

Further description will be made with reference to specific numerical examples. For example, assume that the Zener voltage Vz is 1.2 V (Vz = 1.2 V). Since the voltage for switching from the pre-charging (A1 in FIG. 3) to the full charging (A2 in FIG. 3) is 2.9V, the ratio of the resistance values of the resistors R7 and R8 is R7: R8 =
1.42: 1. That is, when the battery voltage VBATT at the BAT terminal is 2.9 V or more, the voltage at the connection point a of the resistors R7 and R8 becomes 1.2 V or more. For this reason, the output of the amplifier A5 becomes the logic “H” level.

Therefore, the second bleeder resistor R
A current flows through a connection point b between 3 'and R4' (assuming that the resistance ratio is 10: 1), and the potential of the comparator including the pair of PNP-type bipolar transistors Q5 and Q6 is changed to the first bleeder resistors R3 and R4. (Assuming that the resistance ratio is 1: 3)
Of the PNP type bipolar transistor Q
5 is fixed to the potential obtained by adding the forward voltage VF. This potential becomes the threshold voltage Vcl of the constant current control circuit unit 11. CC
The amplifier A2 compares the threshold voltage Vcl with the CS-BAT terminal voltage input via the charging current sense resistor R1, and compares the comparison result with the CNT control circuit unit 1.
Feed to 2 '. In response to the comparison result, the CNT control circuit unit 12 'controls the CNT terminal.

At the time of pre-charging (that is, when the PNP bipolar transistor Q8 is off), the threshold voltage Vcl is such that the voltage at the point b is 0.11V (Vz = 1.2V, R3 ', R4').
Is 10: 1), and the forward voltage VF of the PNP bipolar transistor Q5 is 0.6V, so that the voltage at the point d is (0.11 + 0.6) = 0.71V. Therefore, the voltage drop between CS and BAT is kept at 0.11V. When the charging current sense resistor R1 has a resistance value of 1Ω, the output Q8 of the quadruple amplifier A1 is level-shifted by the forward voltage VF, so that the charging current I _BATT becomes (0.11 /
4) = 0.0275A.

On the other hand, when the point b is at the logic "H" level, c
Since the voltage at the point is 0.9 V (Vz = 1.2 V, the ratio of R3 and R4 is 1: 3), the charging current I _BATT is (0.9
/4)/1=0.225A.

The charge control circuit 10 for a secondary battery shown in FIG. 1 is a circuit for charging a single battery. The charge control circuit for a secondary battery is incorporated in an electronic device such as a mobile phone. In some cases.

[0025]

Generally, the charging control circuit 10 for a secondary battery is designed to charge a single battery (secondary battery) 30 or a group of batteries used at the same time. For this reason, one secondary battery charging control circuit 10 is connected to the adapter 20. However, with the spread of portable devices, there is an increasing demand for simultaneously charging a battery that is still attached to the portable device and its spare battery.

In the conventional charge control method, no problem occurs when charging a single battery 30. However, as will be described in detail later, if two batteries are charged simultaneously by the conventional charging control method, various problems occur due to differences in the capability of the adapter 20, the charging control method, and the like.

For example, as shown in FIG. 4, when the adapter 20 has a rated voltage Vo = 5.5 V and a rated current Io =
It is assumed that it has a capability of 0.7 V and its current characteristic has a drooping characteristic.

Then, using this adapter 20, FIG.
Suppose that charging is attempted in parallel as shown in FIG. In FIG. 5, a charging stand 40 comprises a combination of the secondary battery charging control circuit 10 shown in FIG. 1 and its peripheral circuits. In the illustrated example, the charging stand 40 is assumed to have a capacity of 0.5 A when fully charged, and
(Corresponding to the secondary battery 30 in FIG. 1). Further, it is assumed that the battery unit 50 connected to the charging stand 40 has a battery voltage V _{BATT1 of} 3.2 V at present. On the other hand, the adapter 2 is
0, the set body 60 is shown in FIG.
The secondary battery charge control circuit 10, its peripheral circuit, and the secondary battery 30 are incorporated therein. The illustrated set main body 60 is set to charge the battery at 0.5 A.
It is _assumed that the battery has a battery voltage V _BATT2 of V. That is,
V _{BAT T1} > V _BATT2 .

The charge control circuit for the secondary battery contained in the charging stand 40 and the charge control circuit for the secondary battery contained in the set body 60 have the same configuration.

When the battery voltage V _{BATT1 of the} single battery 50 is 3.2 V, the battery voltage V
_BATT2 is 3V, and both are 2.9V or more. Therefore, both are in the full charge mode (A2 area in FIG. 3). Therefore, the adapter voltage Vcc is fixed with reference to the voltage value (3 V) of the set body 60 having a low battery voltage _VBATT . That is, adapter voltage Vcc = battery voltage (3V) + (voltage drop of ΔV-TR1) = about 3.5V.

At this time, the battery of the set main body 60 is charged at 0.5 A, and the remaining output power of the adapter 20 is set to 0.
The battery 50 is charged at 2A.

However, the adapter voltage Vcc = 3.5
V, the battery voltage V _BATT1 of the battery 50 is 3.
_2A (that is, since the difference between the adapter voltage Vcc and the battery voltage V _BATT1 is as small as 0.3 V), the amplifiers A1 and A2 in FIG. Since the power is received from the voltage Vcc, the operation limit voltage is exceeded due to the relationship of the Vcc input voltage, and there is a possibility that the battery unit 50 cannot be normally charged due to the problem of the IC operation.

On the other hand, as shown in FIG. 6, when the battery voltage V _BATT1 of the battery 50 is 3.0 V,
It is _assumed that the battery voltage V _BATT2 of the battery 0 is _3.2V . In this case, the battery voltage V _BATT1 of the battery 50 alone
Is lower than the battery voltage V _BATT2 of the battery of the set body 60 (V _BATT1 <V _BATT2 ), so that the battery unit 50 is charged preferentially.

[0034] This is because, as shown in Figure 7, the battery voltage V _BATT1 of the battery itself 50 is 2.3V, the same when the battery voltage V _BATT2 of the battery of the set main body 60 was 3.2V is there.

Accordingly, an object of the present invention is to provide a charging control method capable of charging one battery preferentially when two batteries are charged using one adapter.

[0036]

According to the present invention, there is provided a charge control method for charging first and second batteries (50, 64) using one adapter (20),
Adapter voltage (Vcc) and first battery voltage (V
_BATT1 ), and while the difference obtained by subtracting the voltage of the first battery from the voltage of the adapter is smaller than a predetermined voltage, the first battery is not charged and the second battery is given priority. And a charging control method characterized by charging the battery.

In the above charge control method, it is preferable that the first battery is charged when the difference is larger than the predetermined voltage. The predetermined voltage is, for example, 0.6V. Further, when the voltage of the first battery is equal to or lower than the reference voltage and the voltage of the second battery is equal to or higher than the reference voltage, it is preferable to precharge the first battery and fully charge the second battery. Here, the charging current at the time of preliminary charging is, for example, 1/10 of the charging current at the time of full charging.
It is. The reference voltage is, for example, 2.9V.

The reference numerals in the parentheses are provided for facilitating the understanding of the present invention, and are merely examples, and it is a matter of course that the present invention is not limited to these.

[0039]

Embodiments of the present invention will be described below in detail with reference to the drawings.

Referring to FIG. 8, a circuit to which the charging control method according to one embodiment of the present invention is applied will be described.

The present invention is a control method for charging the first battery 50 and the second battery 64 using one adapter 20. In the illustrated example, the first battery 5
Reference numeral 0 denotes a single battery, and a second battery 64 is a battery built in an electronic device (set) body 60 such as a mobile phone. The set main body 60 includes the secondary battery charge control circuit 10 and its peripheral circuits as shown in FIG.

On the other hand, the battery unit 50 is
Is charged by the charging stand 40A. The charging stand 40A is composed of a combination of a secondary battery charging control circuit 10A and its peripheral circuits.

The charge control circuit 10A for the secondary battery includes a control circuit 14 and an NPN type bipolar transistor Q.
2, a differential amplifier 15, a comparator 16, and a switch 18
And

The NPN type bipolar transistor Q2 is
This corresponds to the NPN type bipolar transistor Q2 shown in FIG. In FIG. 2, the control circuit 14
This corresponds to the portion of the charge control circuit 10 for the secondary battery excluding the PN-type bipolar transistor Q2, but further includes a timer (not shown). The differential amplifier 15 compares the potential difference between the adapter voltage Vcc and the battery voltage V _BATT1 ,
This is a circuit that controls the control circuit 14.

The comparator 16 calculates the voltage of the differential amplifier 15 and
This is a circuit for comparing with a voltage set externally. Comparison
The battery unit 16 has an adapter voltage Vcc and the battery voltage of the battery 50 alone.
Pressure V _BATT1To compare with the external set voltage.
You. (Vcc-V_BATT1) Is lower than the external set voltage
Means that the output of the comparator 16 outputs a signal of logic "L" level
I do. In this embodiment, the predetermined voltage is assumed to be 0.6V.
I do. Note that the threshold voltage is determined by the ratio of the resistors Rc and Rb.
Variable. Therefore, (Vcc-V_BATT1) <0.
When the voltage is 6 V, the comparator 16 does not output a signal of a logic “L” level.
To the control circuit 14 via the sensitive circuit A8 (FIG. 9)
Send out. When a signal of logic “L” level is received,
The roll circuit 14 has a charging current I_BATTLike to cut off
To control. As a result, the
Only the battery 64 is charged by the adapter 20
Will be.

On the other hand, when (Vcc-V _BATT1 )> 0.6 V, the comparator 16 sends a signal of logic "H" level to the control circuit 14 via the insensitive circuit A8. When receiving this logic "H" level signal, the control circuit 1
4 controls so that the charging current I _BATT flows. as a result,
The adapter 20 charges both the battery 50 and the battery 64 contained in the set body 60.

Here, as shown in FIG. 6, the battery voltage V _{BATT1 of the} single battery 50 is 3.0 V, and the battery voltage V _{BATT2 of the} battery 64 incorporated in the set body 60.
Is 3.2V. That is, V _BATT1 >
It is assumed that V _BATT2 . In this case, as described above, Vc
Since c = 3.5 V, and the threshold voltage of the comparator 16 is set to 0.6 V, the battery 50 incorporated in the set body 60 is not charged because the battery 50 is not charged.
4 can be charged preferentially.

On the other hand, as shown in FIG. 7, when the battery voltage V _BATT1 of the battery 50 is 2.3 V,
Let's assume that the battery voltage V _{BATT2 of the} battery 64 built in 0 is _3.2V . In this case, as shown in FIG. 3, the battery voltage V _BATT1 of the single battery 50 is in the area A1 where the precharge is performed. As described above, the charging current at the time of preliminary charging is about 1/10 of that at the time of full charging.
Therefore, even if both the battery 50 and the battery 64 incorporated in the set body are charged, the capacity of the adapter 20 is not affected. Therefore, in the present invention, CS-BAT
During the _precharge , the battery 50 at the battery voltage V _BATT1 has an AND configuration so as not to control the CNT terminal. The AND configuration is, as described in FIG. 9, an NPN type bipolar transistor Q2.
0 and Q21. The base potential of NPN bipolar transistor Q20 is connected to the output of insensitive circuit A8. As described above, the operation of the insensitive circuit A8 is such that when the potential difference of (Vcc-VBATT1) is lower than the set voltage, the output of the comparator 16 becomes a logic "L" level. As a result, the output of the insensitive circuit A8 becomes a logic " This is a configuration that becomes the L level. The base of the NPN bipolar transistor Q21 is connected to the output of the amplifier A5, and becomes "L" during precharge and "H" during quick charge. That is, NPN
The AND circuit of the bipolar transistors Q20 and Q21 is capable of quick charging and (Vcc-V _{BA TT1} ) <0.6 V
, The control of NPN type bipolar transistor Q2 (C
(NT terminal) is set to work (turn off charging).

As a result, the battery voltage V of the battery 50 alone
_{When BATT1} is in the precharge area A1 (FIG. 3),
It becomes possible to charge both the battery unit 50 and the battery 64 built in the set body 60. In other words, in the present embodiment, when the battery voltage V _BATT1 of the battery unit 50 is equal to or less than the reference voltage of 2.9 V, and the set body 60
When the battery voltage V _BATT2 of the battery 64 incorporated in the set body is equal to or higher than the reference voltage, the battery 50 is precharged and the battery 64 incorporated in the set body 60 is fully charged. As described above, the charging current at the time of preliminary charging is
For example, it is 1/10 of the charging current at the time of full charging.

In the present embodiment, the charge control circuit for secondary battery 10 A has a select terminal 101. The select terminal 101 is a terminal for switching between charging only one battery or charging two batteries. That is, when only one battery is charged, the select terminal 101 is set to the logic “L” level,
The operation is stopped by cutting the bias current of the amplifiers A6, A7, and A8 in FIG. 9 (turning off the switch 18). When charging two batteries, the select terminal 101 is set to "H", and the bias current of the amplifiers A6, A7, and A8 in FIG. 9 is supplied (the switch 18 is turned on) to enable the operation.

In the present embodiment, the comparator 16 is not
A sensitive circuit A8 is provided. This insensitive circuit
A8 is the adapter voltage Vcc and the battery voltage of the battery 50 alone.
Pressure V _BATT1The output of the comparator 16 for comparing
Even if it switches, its output does not turn over for a certain period of time
This is the circuit to make it work.

As shown in FIG. 9, the select terminal 10
1 is grounded via resistors R11 and R12 connected in series. The connection point of the resistors R11 and R12 is NP
It is connected to the base of N-type bipolar transistor Q11. The emitter of NPN bipolar transistor Q11 is grounded, and the collector is connected to the collector and base of PNP bipolar transistor Q12. P
The emitter of the NP type bipolar transistor Q12 is VC
Connected to terminal C. The base of PNP-type bipolar transistor Q12 is connected to the base of PNP-type bipolar transistor Q13. The emitter of the PNP bipolar transistor Q13 is connected to the VCC terminal, and the collector is grounded via the Zener diode ZD3. That is, the pair of PNP bipolar transistors Q12 and Q13 form a current mirror circuit.

The collector of PNP bipolar transistor Q13 is connected to the base of NPN bipolar transistor Q14. The emitter of the NPN bipolar transistor Q14 is grounded via a resistor R13. The collector of NPN bipolar transistor Q14 is connected to the base and collector of PNP bipolar transistor Q15. The emitter of the PNP bipolar transistor Q15 is connected to the VCC terminal. The base of the PNP bipolar transistor Q15 is composed of PNP bipolar transistors Q16, Q17,
It is connected to the bases of Q18 and Q19. The emitters of the PNP type bipolar transistors Q16 to Q19 are VC
Connected to terminal C. Therefore, a pair of PNP-type bipolar transistors Q15 and Q16, Q15 and Q1
7, Q15 and Q18, and Q15 and Q19 each constitute a current mirror circuit.

The collector of the PNP bipolar transistor Q16 is grounded via the insensitive circuit A8. P
The collector of the NP type bipolar transistor Q17 is connected to switches SW1 and SW2 connected in series and a constant current source CI1.
1 is grounded. The collector of the PNP bipolar transistor Q18 is grounded via the comparator 16. The collector of the PNP bipolar transistor Q19 is grounded via the amplifier 15.

The switch SW1 is turned on when the output of the comparator 16 is at the logic "H" level. The switch SW2 is turned on when the output of the comparator 16 is at the logic "L" level. The connection point of these switches SW1 and SW2 is insensitive circuit A
8 and a capacitor C
Grounded. Resistors R14 and R15 are connected in series between the VCC terminal and the GND terminal, and the connection point of these resistors R14 and R15 is connected to the inverting input terminal of the insensitive circuit A8.

The output of the insensitive circuit A8 is connected to the base of an NPN bipolar transistor Q20. NP
The collector of the N-type bipolar transistor Q20 is NPN
It is connected to the base of a bipolar transistor Q2. The emitter of NPN-type bipolar transistor Q20 is connected to the collector of NPN-type bipolar transistor Q21. NPN type bipolar transistor Q2
One emitter is grounded, and the base is connected to the output terminal of the amplifier A5 via the resistor R16.

The switch 18 shown in FIG. 8 corresponds to the starting circuit (R11, R12, Q11, Q12, Q13, Q13) shown in FIG.
14, Q15, ZD3, R13).

Further, in the present embodiment, as described above, the control circuit 14 has a built-in timer (not shown). This timer is a total timer for protection (protection timer) counted inside the control circuit 14. When charging is stopped in the secondary battery charge control circuit 10A, the timer is reset or stopped. The reason is as follows. This timer provides a predetermined charging time for protection when charging the battery using the secondary battery charging control circuit 10A, and determines that the battery is abnormal if charging is not completed within the predetermined time. belongs to. When two batteries are charged as in the present invention, the charging current is naturally smaller than during normal charging (when one battery is charged). For example, charging was normally completed with a charging current of 500 mA in 5 hours, but when charging current reaches 250 mA, charging requires 10 hours. At this time, if the fixed time set in the timer is 7 hours, the timer times out even though the battery is not abnormal, and an abnormal display is displayed. The timer is reset (initialized) to prevent such malfunctions.

Next, referring to FIG.
The reason why insensitivity is necessary in order to cope with the transient response of the power supply when pulse charging is used will be described. FIG.
Shows a representative waveform of pulse charging.

Here, pulse charging refers to a method in which a voltage higher than the maximum charging voltage of the battery cell and a current higher than the maximum charging current are applied in a pulsed manner, and the battery voltage during the idle time is detected to perform charging.

When charging the set main body 60 in this manner, the comparator 16 in FIG. 9 monitors the voltage between Vcc and BAT. If the comparison amplifier does not have the insensitive circuit A8, the amplifier will be inverted as soon as the voltage exceeds the set voltage (threshold voltage). In actual operation, when Vcc fluctuates due to ripple or the like, the amplifier is inverted each time. (As a result, since the CNT terminal is turned on / off, charging is repeatedly turned on and off.) To prevent such an operation, the insensitive circuit A8 is used.
Is provided. Thus, the output of the insensitive circuit A8 can be provided with insensitivity for a fixed time. This gives N
AND of PN type bipolar transistors Q20 and Q21
The circuit is fast charging and for a certain time (Vcc-VBATT
1) When <0.6V, NPN transistor Q2
(CNT terminal control) works (turns off charging).

Next, with reference to FIG. 9, a description will be given of a configuration for controlling the output control (as a result, the CNT terminal (charging ON / OFF)) by the OR configuration (Q20, Q21) with the output of the comparator 16.

These circuits (A6 to A8) operate with the bias current being supplied by the select terminal 101 being "H". When the select terminal 101 is at "L", these circuits (A6 to A8) are off. Select terminal 1
01 is used when charging two batteries from one adapter 20.

The purpose of this circuit (A6 to A8) is to
The voltage difference between −BAT is monitored, and when (Vcc−V _BATT1 ) <set voltage (0.6 V) (except during preliminary charging), charging is stopped and charging of the main body is prioritized. is there. The meaning of excluding during pre-charging means that the charging current is smaller during pre-charging than during rapid charging, and that the adapter 20 has the capability.

The circuit operation is as follows: at the time of pre-charging (when the output of the amplifier A5 of the pre-charge detection circuit 13 is at the logic "L" level, the output of the amplifier A8 is ANDed, and the CNT control circuit 12 'is controlled. .

The charging current I _BATT is changed from A1 to A2 in FIG.
Is the amplifier A5 in FIG.

As described above, the present invention has been described with reference to the embodiments. However, it goes without saying that the present invention is not limited to the above embodiments.

[0068]

As is apparent from the above description, according to the present invention, when two batteries are charged using one adapter, the voltage of the adapter is compared with the voltage of one of the batteries, and the voltage of the adapter is compared. While the difference obtained by subtracting the voltage of one battery from is smaller than a predetermined voltage, the other battery is preferentially charged without charging one battery. In addition, when the adapter is considered capable, such as at the time of preliminary charging, both charging can be performed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration for charging using a conventional charge control circuit for a secondary battery.

FIG. 2 is a block diagram showing a configuration of a charge control circuit for a secondary battery shown in FIG.

FIG. 3 is a diagram showing a relationship between a battery voltage and a charging current.

FIG. 4 is a graph showing output characteristics of an adapter.

FIG. 5 shows a conventional configuration in which one adapter is used to charge two batteries (the voltage of one battery is 3.
FIG. 3 is a block diagram illustrating an example in which the voltage of the other battery is 3 V at 2 V).

FIG. 6 shows a state in which the voltage of one battery is 3 V in FIG.
It is a block diagram showing an example in the case where the voltage of the other battery is 3.2V.

FIG. 7 shows that the voltage of one battery is 2.3 V in FIG.
FIG. 9 is a block diagram showing an example in which the voltage of the other battery is 3.2 V.

FIG. 8 is a block diagram showing a configuration for realizing a charging control method according to one embodiment of the present invention.

9 is a block diagram illustrating a configuration of a charge control circuit for a secondary battery illustrated in FIG. 8;

FIG. 10 is a diagram showing a representative waveform of pulse charging.

[Explanation of symbols]

10A Rechargeable battery charge control circuit 14 Control circuit 15 Amplifier 16 Comparator A8 _Insensitive circuit 18 Switch 20 Adapter 50 Battery unit 60 Set body 64 Battery TR1 Power transistor R1 Charge current sense resistor V _BATT1 , V _BATT2 Battery voltage (battery Voltage) Vcc adapter voltage

Claims (6)

[Claims] 1. The first and the second using one adapter.
A charging control method for charging the battery of claim 1, wherein the voltage of the adapter is compared with the voltage of the first battery, and the difference obtained by subtracting the voltage of the first battery from the voltage of the adapter. Charging the second battery preferentially without charging the first battery while is smaller than a predetermined voltage. 2. The charging control method according to claim 1, wherein the charging of the first battery is performed when the difference is larger than the predetermined voltage. 3. The charge control method according to claim 1, wherein the predetermined voltage is 0.6V. 4. When the voltage of the first battery is equal to or lower than a reference voltage and the voltage of the second battery is equal to or higher than the reference voltage, the first battery is precharged and the second battery is fully charged. The charging control method according to claim 2, wherein the charging is performed. 5. The charge control method according to claim 1, wherein the charge current at the time of the preliminary charge is 1/10 of the charge current at the time of the full charge. 6. The charging control method according to claim 4, wherein said reference voltage is 2.9V.