JPH09149559A - Charger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform the charge of a secondary battery and the power supply to a specified electronic circuit in parallel, regardless of the terminal voltage of the secondary battery of portable electronic equipment. SOLUTION: A secondary battery 2 is connected, through a charge control switch SW2, to the charge terminals 10a and 10b of a charger 10P, and also the electronic circuit 3 of the portable electronic equipment 1P is connected through a rectifying diode 21 and a smoothing capacitor 22. If a voltage detecting circuit 15 detects the terminal voltage of the secondary battery being short of the minimum operation voltage of an electronic circuit 3, the switch SW2 is opened and closed periodically to charge the secondary battery intermittently, by the pulse P17 of a pulse train generating circuit 17 which operates from the detection output, and also the electronic circuit 3 is supplied with currents through a rectifying and smoothing circuit. When the terminal voltage of the secondary voltage reaches the minimum operation voltage of the electronic circuit 3, the switch is turned on to charge the secondary battery continuously and supply the electronic circuit 3 with power through a diode.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging device suitable for charging a secondary battery used as a power source for portable electronic equipment.

[0002]

2. Description of the Related Art In recent years, mobile phones, which have become very popular, are provided with a receiver and a transmitter, dial keys and various function control keys, a liquid crystal display element and the like on the front of the main body of the phone. In addition, a secondary battery as a power source of this mobile phone is coupled to the back of the main body to be configured as a battery drive type.

Conventionally, a nickel-cadmium storage battery has been generally used as a secondary battery as a power source for such portable small electronic devices, but a nickel-hydrogen storage battery having a higher capacity and a higher energy density, or Lithium ion storage batteries, which have higher energy density, have come into use.

[0004] This lithium ion storage battery has a nominal voltage of 3.6 V, and has a nickel-cadmium storage battery or a nickel-cadmium storage battery.
The nominal voltage of the hydrogen storage battery is 1.2 times higher than 1.2V, and the charge / discharge cycle life is 1200 times, more than twice as long as 500 times of the nickel-cadmium storage battery or the nickel-metal hydride storage battery.

Further, when a nickel-cadmium storage battery or a nickel-hydrogen storage battery is repeatedly charged and used before 100% discharge, an inactive part is generated in the electrode and the voltage drops in the middle of discharge. There is a phenomenon, the so-called memory effect, which reduces the effective capacity. However, by completely discharging and then recharging the nickel-cadmium storage battery or the nickel-hydrogen storage battery, the memory effect can be canceled and the regular capacity can be restored.

For this reason, some chargers for nickel-cadmium storage batteries and nickel-hydrogen storage batteries are designed to be completely discharged before being charged, and accordingly, the time required for charging is long. It will change again.

Since the lithium-ion storage battery does not have the above memory effect, the charger can be simplified. Also,
The lithium ion storage battery can be easily charged by the constant current circuit and the constant voltage circuit. Moreover, the lithium-ion storage battery can calculate the charge amount of the battery almost accurately based on the battery voltage or the charging current by utilizing the characteristics of the battery.

For example, as shown in FIG. 5, a general-purpose charger 10 for a lithium ion storage battery BLi is one of the charging terminals 10
a and one of output terminals 11a of a DC power supply circuit (so-called AC adapter) 11 for obtaining a required DC output from commercial AC
And the constant current circuit 12 and the constant voltage circuit 13 are connected in series, and a resistor 14r for current detection is provided between the other charging terminal 10b and the other output terminal 11b of the DC power supply circuit 11. Is inserted. The voltage generated across the resistor 14r is supplied to the current detection circuit 14, the voltage between the charging terminals 10a and 10b is supplied to the voltage detection circuit 15, and the outputs of the current detection circuit 14 and the voltage detection circuit 15 are supplied. Is supplied to the charge amount display circuit 16.

The constant current circuit 12 is set so that the maximum charging current of the single cell is 2 C (1/2 hour rate) or less, and the constant voltage circuit 13 sets the charging voltage of the single cell to 4. It is set within a relatively narrow range of 2 ± 0.05V. This is because the charging capacity largely depends on the charging voltage value.

The charging of the lithium ion storage battery is performed, for example, by
As shown in FIG. 6, during the initial 30 minutes of charging, the battery was charged to almost 50% of the battery capacity by rapid charging with a charging current of 1 C (1 hour rate), and then 100% by constant voltage charging for 2 hours. Be charged. The charging current during the constant voltage charging period is automatically gradually reduced depending on the characteristics of the battery.

The above-mentioned charging stand for a mobile phone is constructed so that the secondary battery can be charged while being connected to the back of the mobile phone body. For example, an input terminal for charging is provided at the bottom of the secondary battery, and by placing the mobile phone at a predetermined position on the charging stand, an output terminal on the charging stand side and an input terminal on the secondary battery side are provided. And are connected.
A so-called AC adapter is built in this charging stand. Further, an output terminal for charging a spare secondary battery by itself is also provided.

By the way, it is desirable that the portable telephone be in an operable state even when it is placed on the charging stand.

However, as described above, even if an attempt is made to operate the mobile phone while charging the secondary battery while being connected to the mobile phone body, the secondary battery is completely discharged and the remaining capacity is 0%. In the so-called "battery dead" state, the terminal voltage V2 (0) of the secondary battery falls below the minimum operating voltage Vwmin of the mobile phone, and the mobile phone cannot be operated.

When the above-mentioned lithium ion storage battery is used, the minimum operating voltage Vwmin of the mobile phone is set to 3.0V, for example. On the other hand, the terminal voltage V2 (0) at the time of complete discharge of the lithium ion storage battery has dropped to about 2.5 V as shown in FIG.

Even if the terminal voltage of the secondary battery becomes higher than the minimum operating voltage Vwmin of the mobile phone due to the progress of charging, the power supply from the secondary battery to the mobile phone causes the secondary battery to be charged and discharged. Will increase and accelerate deterioration.

Therefore, the conventional mobile phone and its charging stand can separately supply power to the secondary battery and the circuit system of the mobile phone, which is a load of the secondary battery. Is configured.

In the simplest case, it is conceivable to provide separate DC power supplies for the secondary battery and the circuit system of the mobile phone. However, with such a configuration, the shape becomes large and the cost is significantly increased.

Therefore, conventionally, for example, as shown in FIG. 7, the output of a single DC power source is supplied to the circuit system of the secondary battery and the mobile phone through two switches respectively corresponding thereto. .

Referring to FIG. 7, a charging stand 10D for a mobile phone.
In the same manner as the general-purpose charger 10 shown in FIG. 5, between one of the charging terminals 10a and one of the output terminals 11a of the DC power supply circuit 11 that obtains a required DC output from the commercial AC,
The constant current circuit 12 and the constant voltage circuit 13 are connected in cascade, and a resistor 14r for current detection is provided between the other charging terminal 10b and the other output terminal 11b of the DC power supply circuit 11.
Is inserted. The voltage generated across the resistor 14r is supplied to the current detection circuit 14, and the charging terminals 10a, 1
The voltage between 0b is supplied to the voltage detection circuit 15.

Further, the mobile phone 1 comprises a secondary battery (lithium ion storage battery) 2, a light load circuit 3L, a heavy load circuit 3W, and a common operation control switch SW3.

The light load circuit 3L operates intermittently in order to form a control circuit between the receiving system circuit and the control system circuit that continuously operate when in the "standby" state for incoming calls, and the public base station during standby. The heavy load circuit 3W represents each circuit that continuously operates during a call. Further, the switch SW3 is a switch corresponding to off-hook.

One end of each of the secondary battery 2, the light load circuit 3L and the heavy load circuit 3W is one of the charging terminals 10 of the charging stand 10D.
commonly connected to a. The other end of the secondary battery 2 is connected to the other charging terminal 10b through the charging control switch SW2, and the other ends of the light load circuit 3L and the heavy load circuit 3W are connected through the operation control switch SW3 to the charging terminal. Is connected to the other 10b. Then, the outputs of the current detection circuit 14 and the voltage detection circuit 15 of the charging stand 10D are supplied to the charging control switch SW2 as control signals, respectively.

The operation of the charging stand 10D shown in FIG. 7 is generally as follows.

In the initial state, the secondary battery 2 is completely discharged, and its terminal voltage V2 (0) is lower than the minimum operating voltage Vwmin (= 3.0V) of the mobile phone 1. Further, as shown in FIG. 7, it is assumed that the switch SW2 is “on” and the switch SW3 is “off”.

(A) When the terminal voltage V2 (0) of the secondary battery 2 is detected by the voltage detection circuit 15, the terminal voltage is Vwmin.
Since it is lower, the charge control switch SW2 remains "on" due to the detected output. Then, the secondary battery 2 is charged, its terminal voltage rises, and at an appropriate time ta
Then, the minimum operating voltage Vwmin of the mobile phone 1 is reached.

(B) The terminal voltage of the secondary battery 2 during charging,
The detection of the output current of the charging stand 10D is continued. When the operation control switch SW3 is turned “on” before or after the time point ta, both load circuits 3L and 3W are in the operating state, the current consumption of the mobile phone 1 rapidly increases, and the secondary battery 2 The terminal voltage drops.

(C) The current detection circuit 14 detects an increase in current consumption of the mobile phone 1, and switches the charging control switch SW2 to "OFF" according to the detection output.
In the mobile phone 1, power is supplied from the charging stand 10D and a call is made with the other party. In the secondary battery 2, the discharge path is blocked, an increase in the number of times of charging and discharging is suppressed, and deterioration is prevented.

(D) The current consumption of the mobile phone 1 is continuously detected during the call processing. When the call ends, mobile phone 1
The current consumption of the battery decreases rapidly, and the terminal voltage of the secondary battery 2 increases.

(E) The charge control switch SW2 is turned back on by the detection output of the current detection circuit 14. At this time, charging of the secondary battery 2 is continued, and at an appropriate time tf.
Then, the secondary battery 2 is fully charged.

(F) The current detection circuit 14 and the voltage detection circuit 15 detect the full charge of the secondary battery 2, and the charge control switch SW2 is turned "off" based on both detection outputs. As a result, overcharge of the secondary battery 2 is prevented.
After the time point tf, even if the operation control switch SW3 is turned on, the charging control switch SW2 remains “off”, and the mobile phone 1 can communicate with the other party by the power supply from the charging stand 10D. Be seen.

[0031]

However, in the conventional charging stand 10D as described above, depending on the charging period of the secondary battery 2 and the operation (by the user) on the mobile phone 1 side, the charging stand 10D can be used. Since the power is supplied from the mobile phone 1, the light load circuit 3L cannot be operated to realize the "standby" state over the entire charging period, and there is a problem that the basic function of the mobile phone 1 is limited.

In view of the above points, an object of the present invention is to relatively charge a secondary battery which is a power source of a portable electronic device with a relatively simple structure, regardless of the terminal voltage of the secondary battery. An object of the present invention is to provide a charging device capable of charging a secondary battery and supplying power to a predetermined electronic circuit in parallel.

[0033]

In order to solve the above-mentioned problems, a charging device according to the present invention comprises a DC power supply circuit for charging a secondary battery as a power source of a portable electronic device and an output terminal. In the device, a switch means, a rectifying / smoothing means, a voltage detecting means for detecting a terminal voltage of the secondary battery, and a detection output of the voltage detecting means,
Control means for periodically opening and closing the switch means is provided, the output terminal and the secondary battery are connected via the switch means, and the output terminal is connected to the output terminal via the rectifying / smoothing means. The electronic circuit is connected, and when the terminal voltage below the predetermined value of the secondary battery is detected by the voltage detecting means, the switching means is periodically opened and closed by the control means. It is a thing.

[0034]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, referring to FIGS. 1 and 2, a charging device according to the present invention will be described for a portable electronic device, for example, a pager, which consumes substantially constant current and has a relatively small current consumption. A first embodiment applied to a charging stand will be described.

FIG. 1 shows the configuration of the first embodiment of the present invention.
Shown in In FIG. 1, parts corresponding to those in FIG.

In FIG. 1, a charging stand 10P for a pager
Is a constant current circuit between one of the charging terminals 10a and one of the output terminals 11a of the DC power supply circuit 11 that obtains a required DC output from commercial AC, as in the charging stand 10D shown in FIG. 12 and the constant voltage circuit 13 are connected in series, the other charging terminal 10b and the other output terminal 1 of the DC power supply circuit 11
A resistor 14r for current detection is inserted between the resistor 1r and 1b. The voltage generated across the resistor 14r is supplied to the current detection circuit 14, and the voltage V10 between the charging terminals 10a and 10b is supplied to the voltage detection circuit 15.

In this embodiment, the pulse train generation circuit 1
7 is provided, and the detection output of the voltage detection circuit 15 is supplied to the pulse generation circuit 17 as a control signal. A rectifying diode 21 and a smoothing capacitor 22 are connected in series between the charging terminals 10a and 10b.

On the pager 1P side, one end of the secondary battery (lithium ion storage battery) 2 is connected to one of the charging terminals 10a of the charging stand 10P, and the other end of the secondary battery 2 is connected through the charge control switch SW2. The other side 10b of the charging terminal
And the load circuit 3 is connected in parallel to the capacitor 22.

Then, the respective detection outputs of the current detection circuit 14 and the voltage detection circuit 15 and the output P17 of the pulse train generation circuit 17 serve as switch control signals, and the switch SW.
2 is supplied.

Although not shown, the DC power supply circuit 11 uses a DC-DC converter including a switching transistor and a high frequency transformer to output the DC output of the main power supply circuit by a so-called switching method. Alternatively, the high frequency current may be converted into a direct current output for charging the secondary battery connected to the output terminal by rectifying the high frequency current.

Next, referring also to FIG. 2, the first part of FIG.
The operation of the embodiment will be described.

In the pager system, when the caller makes a call to the number given to the pager, this is notified to the pager through the base station (operator), and the person carrying the pager (callee) can call the pager. It is called by sound.

As described above, in the initial state, the secondary battery 2 is completely discharged, and its terminal voltage V2 (0) is lower than the minimum operating voltage Vwmin (= 3.0V) of the pager 1P. To do. Further, it is assumed that the switch SW2 is “on”.

Under the above conditions, the charging stand 10P shown in FIG.
Generally operates as follows.

(A) The terminal voltage V2 (0) of the secondary battery 2 is detected by the voltage detection circuit 15, and the pulse train generation circuit 17 is activated by the detection output, as shown in FIG. 2A.
Pulse train P17 with constant pulse rate (duty factor)
To drive the charging control switch SW2. Then, the switch SW2 repeats "on" and "off" according to the "high level" and "low level" of the pulse train P17.

As a result, the secondary battery 2 has the switch SW.
Only during the "ON" period of 2, the constant current is intermittently charged,
The terminal voltage rises.

On the other hand, the voltage V between the charging terminals 10a and 10b
10 is reduced during the "on" period of switch SW2,
The pulse train is as shown in FIG. 2B, and the rectifying diode 2
1 to charge the capacitor 22. Capacitor 2
When the capacitance of 2 is sufficiently large, the terminal voltage V22 thereof is approximately equal to the peak voltage between the charging terminals 10a and 10b (voltage during the period when the switch SW2 is "OFF"), which is sufficient as the minimum operating voltage Vwmin of the pager 1P.

Therefore, during the intermittent charging period, the load circuit 3 is
Via the rectifying diode 21 and the smoothing capacitor 22,
It operates normally by the DC power supplied from the charging stand 10P.

(B) The terminal voltage of the secondary battery 2 is continuously detected during the intermittent charging described above. In this case, the appropriate time ta
Then, the terminal voltage V2a of the secondary battery 2 reaches the minimum operating voltage Vwmin of the pager 1P.

(C) The terminal voltage V2a of the secondary battery 2 is detected by the voltage detection circuit 15, and the pulse output generation circuit 17 is stopped by the detection output, and the charge control switch SW2 is turned on. Then, the secondary battery 2 is continuously charged. During this continuous charging, since the electromotive force of the secondary battery 2 is lower than the charging voltage V10 of the charging stand 10P, the load circuit 3
Is mainly charged through the diode 21 through the charging stand 10P.
Powered by Then, at an appropriate time tf, the secondary battery 2
Will be fully charged.

(D) The current detection circuit 14 and the voltage detection circuit 15 detect the full charge of the secondary battery 2, and the charge control switch SW2 is turned "off" based on both detection outputs. As a result, power supply from the secondary battery 2 to the load circuit 3 and overcharge of the secondary battery 2 are reliably prevented.

As described above, in the embodiment shown in FIG.
The terminal voltage of the secondary battery 2 is the minimum operating voltage Vwm of the pager 1P.
Even during a period short of in, by intermittent charging and rectification, charging of the secondary battery 2 and power feeding to the pager 1P can be performed in parallel from the single DC power supply circuit 11, and during the charging period. , The basic function of the pager 1P is not limited.

[Second Embodiment] Next, another embodiment in which the charging device according to the present invention is applied to a charging stand for a portable telephone will be described with reference to FIGS. 3 and 4.

The structure of another embodiment of the present invention is shown in FIG. In FIG. 4, parts corresponding to those in FIGS. 1 and 7 are given the same reference numerals.

In FIG. 4, the charging stand 10M is shown in FIG.
One of the charging terminals 10a, similar to the charging stand 10P shown in FIG.
And a DC power supply circuit 1 that obtains the required DC output from commercial AC
A constant current circuit 12 and a constant voltage circuit 13 are connected in cascade between the output terminal 1 and the one output terminal 11a.

In the charging stand 10M of this embodiment, a resistor 14r for current detection and a resistor having a relatively high resistance value are provided between the other charging terminal 10b and the other output terminal 11b of the DC power supply circuit 11. 18 and is inserted in series,
The switch SW1 is connected in parallel with the resistor 18.

The voltage generated across the resistor 14r is supplied to the current detection circuit 14 and the charging terminals 10a, 1
The voltage V10 between 0b is supplied to the voltage detection circuit 15, and the detection output of the current detection circuit 14 is supplied to the switch SW1 as a control signal.

Further, in this embodiment, the detection output of the voltage detection circuit 15 is supplied as a control signal to the pulse train generation circuit 17M, and at the same time, as a pulse width modulation signal.
The voltage V10 is supplied. And both charging terminals 10a, 1
A rectifying diode 21 and a smoothing capacitor 22 are connected in series between 0b.

On the side of the mobile phone 1A, one end of each of the secondary battery (lithium ion storage battery) 2 and the heavy load circuit 3W is connected to one of the charging terminals 10a of the charging stand 10M, and the other end of the secondary battery 2 is connected. , The heavy load circuit 3W while being connected to the other charging terminal 10b through the charging control switch SW2.
The other end of is connected to the other charging terminal 10b through the operation control switch SW3. The light load circuit 3L is connected in parallel with the capacitor 22.

Then, the respective detection outputs of the current detection circuit 14 and the voltage detection circuit 15 and the output P17 of the pulse train generation circuit 17M are respectively used as the switching control signal and the switch S.
It is supplied to W2.

As described above, the light load circuit 3L forms a receiving system circuit and a control system circuit that continuously operate when in the "standby" state for incoming calls, and a control line with the public base station during standby. Therefore, the transmission system circuit that operates intermittently is represented, and the heavy load circuit 3W represents each circuit that continuously operates during a call.

The switch SW3 is a switch corresponding to an off-hook button, and its opening / closing is also controlled by the control system circuit in the light load circuit 3L according to the operation mode.

Next, referring also to FIG. 3, the second line of FIG.
The operation of the embodiment will be described.

Similar to the above, in the initial state, the secondary battery 2 is completely discharged, and its terminal voltage V2 (0) is lower than the minimum operating voltage Vwmin (= 3.0V) of the mobile phone 1A. And Further, it is assumed that the mobile phone 1A is set to, for example, an answering machine, and when a call comes in, a response message is transmitted and a message of the other party is automatically recorded. Then, as shown in FIG. 4, the switches SW1 and SW2 are both “on”.
And the switch SW3 is “off”.

Under the above conditions, the charging stand 10M of FIG.
Generally operates as follows.

(A) The terminal voltage V2 (0) of the secondary battery 2 is detected by the voltage detection circuit 15, and the pulse train generation circuit 17M is activated by the detection output, and the charge control switch S
Drive W2. At this time, the switch SW2 responds to “high level” and “low level” of the pulse train P17.
"On" and "off" are repeated.

As a result, the secondary battery 2 has the switch SW.
Only during the "ON" period of 2, the constant current is intermittently charged,
The terminal voltage rises.

Since the voltage V10 is supplied to the pulse train generation circuit 17M as a pulse width modulation signal,
The pulse rate (duty factor) of the pulse train P17 is
As shown in FIG. 3A, as the voltage V10 rises, the effective charging current during the intermittent charging becomes larger than that at the constant pulse rate, and the intermittent charging period can be shortened.

On the other hand, the voltage V between the charging terminals 10a and 10b
10 is reduced during the "on" period of switch SW2,
The pulse train is as shown in FIG. 3B, and the rectifying diode 2
Through 1, the smoothing capacitor 22 is charged. When the capacity of the capacitor 22 is sufficiently large, its terminal voltage V22 is
Peak voltage between charging terminals 10a and 10b (switch SW
2 is approximately equal to the voltage during the "off" period), which is sufficient for the minimum operating voltage Vwmin of the mobile phone 1A.

Therefore, in this intermittent charging state, the light load circuit 3L receives the DC power supplied from the charging stand 10P via the rectifying diode 21 and the smoothing capacitor 22,
It normally operates "standby".

When a call comes in during the intermittent charging as described above, the operation control switch SW3 is turned on, and the heavy load circuit 3 is sent for transmitting a response message.
W becomes the operating state, the current consumption of the mobile phone 1A increases rapidly, and the voltage V10 between the charging terminals 10a and 10b decreases.

(B) The current detection circuit 14 detects an increase in the current consumption of the mobile phone 1A, and the detection output thereof preferentially turns off the switch SW2. Further, the pulse train generation circuit 17M is suspended according to the detection of the voltage drop of the voltage detection circuit 15.

Then, the charging path to the secondary battery 2 is cut off, and the voltage V10 becomes the minimum operating voltage Vwm of the mobile phone 1A.
It returns to the original voltage of the charging stand 10M, which exceeds in, and is fed to the light load circuit 3L through the diode 21 and the heavy load circuit 3W is fed directly from the charging stand 10M until recording of the other party's message. Answering machine processing is executed.

(C) The detection of the current consumption of the mobile phone 1A is continued even during the answering machine processing. When the answering machine is finished, the current consumption of the mobile phone 1A sharply decreases and the charging terminal 1
The voltage V10 between 0a and 10b rises.

(D) The pulse train generation circuit 17M is restarted by the voltage rise detection output of the voltage detection circuit 15, the charge control switch SW2 is driven by the output pulse train P17, and the switch SW2 is turned "on" and "off". And repeat. As a result, the intermittent charging of the secondary battery 2 is continued, its terminal voltage rises, and reaches the minimum operating voltage Vwmin of the mobile phone 1A at an appropriate time ta.

(E) Terminal voltage of the secondary battery 2 V2a = Vwmin
Is detected by the voltage detection circuit 15, and the detection output thereof causes the pulse train generation circuit 17 to pause and turns on the charge control switch SW2. Therefore, the secondary battery 2 is continuously charged. During this continuous charging, the secondary battery 2
Is lower than the charging voltage V10 of the charging stand 10P, the light load circuit 3L is mainly fed from the charging stand 10P through the diode 21. Then, the secondary battery 2 is fully charged at an appropriate time tf.

(F) The full charge of the secondary battery 2 is detected by the current detection circuit 14 and the voltage detection circuit 15, and the detection control outputs the charge control switch SW2 to "OFF" and the switch SW1. Switch to "off". Power supply from the secondary battery 2 to both load circuits 3L and 3W,
Overcharge of the secondary battery 2 is reliably prevented.

As described above, in the embodiment shown in FIG.
The terminal voltage of the secondary battery 2 is the minimum operating voltage V of the mobile phone 1A.
Even during a period when wmin is insufficient, the charging of the secondary battery 2 and the power supply to the light load circuit 3L can be performed in parallel from the single DC power supply circuit 11 by the intermittent charging and the rectification, and the full charging is performed. The function of the mobile phone 1A is not restricted during the period.

When a call is received during continuous charging of the secondary battery 2 in the above item (e), (b),
The processing of the item (c) is performed, and then the continuous charging is continued.

In the embodiment shown in FIG. 4, overcharge of the secondary battery 2 can be prevented by the following method.

That is, at the end of the continuous charging of the secondary battery 2 in the above item (e), the charge control switch SW2 is turned on and the operation control switch SW3 is turned off. .

In this state, the current detection circuit 14 detects that the secondary battery 2 is almost fully charged, and the switch SW1 is turned "off". Even if the charging current value is suppressed by being inserted in the charging path and the charging control switch SW2 remains “on”, overcharging can be prevented.

When a call comes in while the switch SW1 is "off", the current detection circuit 14 detects an increase in the current consumption of the mobile phone 1A, and the output of the detection detects the switch SW1. Should be "on".

Alternatively, although not shown in FIG. 4, the voltage detection circuit 15 detects a decrease in the voltage V10 between the charging terminals 10a and 10b, and the detection output thereof turns the switch SW1 on. You may

When the switch SW1 is turned "off" by appropriately selecting the resistance value R18 of the resistor 18, the current I3L flowing through the light load circuit 3L of the mobile phone 1A is set.
Then, the output current I10 of the charging stand 10M can be made substantially equal to each other, and almost no charging current can flow into the secondary battery 2 at the end of continuous charging.

[Other Embodiments] In the above-described embodiments, all of the charging control functions including the switch SW2 are arranged on the charging stand side.
It is also possible to appropriately disperse and arrange the charging stand side and the electronic device side, and exchange control signals with each other to execute the same control processing as that in each of the above-described embodiments.

[0087]

As described above, according to the charging device of the present invention, when the secondary battery which is the power source of the portable electronic device is charged, regardless of the terminal voltage of the secondary battery,
It is possible to charge the secondary battery and supply power to a predetermined electronic circuit in parallel.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of a charging device according to the present invention.

FIG. 2 is a time chart for explaining the operation of the embodiment of the present invention.

FIG. 3 is a time chart for explaining the operation of another embodiment of the present invention.

FIG. 4 is a block diagram showing a configuration of another embodiment of the present invention.

FIG. 5 is a block diagram for explaining the present invention.

FIG. 6 is a schematic diagram for explaining the present invention.

FIG. 7 is a block diagram showing a configuration example of a conventional charging device.

[Explanation of symbols]

 1, 1A Mobile phone 1P Pager 2 Secondary battery (lithium ion storage battery) 3 Load circuit 3L Light load circuit 3W Heavy load circuit 10P, 10M Charging stand 14 Current detection circuit 15 Voltage detection circuit 17, 17M Pulse train generation circuit 21 Rectifier diode 22 Smoothing capacitor SW2 Charge control switch SW3 Operation control switch

Claims (3)

[Claims] 1. A charging device comprising a DC power supply circuit for charging a secondary battery as a power source of a portable electronic device and an output terminal, comprising a switch means, a rectifying / smoothing means, and a terminal of the secondary battery. A voltage detection means for detecting a voltage and a control means for periodically opening and closing the switch means based on a detection output of the voltage detection means are provided, and the output terminal and the secondary battery are connected via the switch means. When a predetermined electronic circuit of the portable electronic device is connected to the output terminal via the rectifying / smoothing means, and the terminal voltage less than the predetermined value of the secondary battery is detected by the voltage detecting means. The charging device is characterized in that the control means periodically opens and closes the switch means. 2. The charging device according to claim 1, wherein the control means generates a pulse train having a constant pulse rate. 3. The charging device according to claim 1, wherein the control means generates a pulse train whose pulse rate increases in response to an increase in the terminal voltage of the secondary battery.