JPH10271702A - Charger interface circuit and portable equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a charger interface circuit such that the number of charging terminals are two in a portable equipment of telephone or the like. SOLUTION: During a charge, positive voltage is applied to a monitor and charge terminal 9, a digital transistor 5 is switched to an on-condition, In this way, from the digital transistor 5 to a charger connected/or detection circuit 21, a signal of 'Lb level is transmitted, connection of a charger is detected. In a control signal generating circuit 20, when a detection signal of charger connection is received from the charger connected/or not detection circuit 210, a control signal 13 periodically switching the potential to 'H'/'L' is output to a digital transistor 11. In this way, a P channel FET 10 repeats an on/off condition, a secondary battery 7 is charged. Also during the charge, the P channel FET 10 is swiftly held in an off-condition when the charger is removed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is particularly applicable to a charger interface circuit, and more particularly to an interface circuit configured to charge a secondary battery while controlling a charging current by detecting a voltage of the secondary battery. Regarding effective technology, for example, personal handy phone system (PHS: pe
rsonal handy phone system
m) and other useful circuits.

[0002]

2. Description of the Related Art Some portable devices such as portable telephones have a built-in secondary battery and charge the secondary battery using an external charger. In general,
2. Description of the Related Art In a mobile phone or a phone using a weak radio wave called a so-called cordless phone, a charging terminal electrically connected to a secondary battery in the phone is exposed and provided on an outer surface of the phone. . When the power supply terminal provided on the charger is pressed against the charging terminal, the secondary battery in the telephone and the charger are electrically connected, and the charging of the secondary battery is started. Is being done. In order to press the power supply terminal of the charger against the charging terminal of the telephone, the power supply terminal of the charger is generally biased by a spring so as to be able to press against the charging terminal of the telephone.

FIG. 9 shows a conventional charger interface circuit provided in a portable telephone or the like. In this charger interface circuit 100, as a charging terminal,
A charging terminal 1, a monitor terminal 2 for detecting the voltage of the secondary battery 7,
And a ground terminal 3 are provided.

[0004] A diode 4 is connected between the charging terminal 1 and a positive electrode of a secondary battery 7 built in a telephone or the like to prevent a current from flowing backward. The anode and cathode of the diode 4 are connected to the charging terminal 1 and the positive electrode of the secondary battery 7, respectively. A battery voltage monitoring resistance element 8 is connected between the monitor terminal 2 and the positive electrode of the secondary battery 7. The resistance value of the monitor resistance element 8 is selected so that no abnormality occurs even if the monitor terminal 2 and the charging terminal 1 are short-circuited.

The ground terminal 3 is commonly connected to a ground point together with the negative electrode of the secondary battery 7.

Further, a digital transistor 5 for detecting that an external charger (not shown) is connected to the charging terminal is connected to the charging terminal 1. The output terminal of the digital transistor 5 is pulled up to a predetermined potential via a pull-up resistor element 6 and connected to a charger provided as an external circuit of the charger interface circuit 100 in a main body such as a telephone. It is connected to the detection circuit 110.

[0007] The charger connection presence / absence detection circuit 110 and the positive and negative electrodes of the secondary battery 7 are connected to various parts in a main body such as a telephone.

[0008] The charger interface circuit 10 having the above configuration.
The effect of 0 is as follows. That is, the charging terminal 1
, A positive voltage is applied from an external charger (not shown) during charging. During charging, the voltage of the secondary battery 7 is detected by an external charger (not shown) via the monitor terminal 2. Then, an external charger (not shown) is controlled according to the detected voltage. Thereby, the charging current supplied from an external charger (not shown) to the charging terminal 1 is controlled, and the secondary battery 7 is fully charged without being overcharged.

The charger interface circuit 10
0, the diode 4 is provided between the charging terminal 1 and the positive electrode of the secondary battery 7 so that when the charging terminal 1 and the ground terminal 3 are short-circuited via a metal or the like, the secondary battery 7 Backflow of current from the positive electrode toward the charging terminal 1 is prevented.

[0010] Some cordless phones and the like go off-hook when the cordless phone or the like is removed from the charger, and go on-hook when returned to the charger. In the case of a telephone having such a function, when an external charger (not shown) is connected to the charging terminal of the charger interface circuit 100, the telephone goes on-hook and
The digital transistor 5 switches from the OFF state to the ON state, and outputs a detection signal to the charger connection presence / absence detection circuit 110.

In the circuit shown in FIG. 9, when detecting the connection of the charger, the digital transistor 5 outputs a signal of an L (low) level having a relatively low potential. When the charger is not connected, the potential of the output terminal of the digital transistor 5 is kept at a relatively high “H (high)” level potential.

The detection signal output from the charger connection presence / absence detection circuit 110 is sent to a control circuit (not shown) in the telephone body that controls on-hook and off-hook when the charger is attached and detached. Therefore, when the charger (not shown) is disconnected from the telephone to which the charger (not shown) is connected, the telephone automatically goes to an off-hook state, while the charger (not shown) is in an off-hook state. When a charger (not shown) is connected to the telephone, the telephone automatically goes on-hook.

[0013]

However, in the above-described conventional charger interface circuit, a charging terminal to which a positive voltage is applied from an external charger at the time of charging and a charging state of the secondary battery being charged are monitored. Monitor terminal for
With the need for at least three charging terminals, a ground terminal, as mobile devices have become increasingly smaller, these days,
There is a problem that it is difficult to secure a mounting space for a charging terminal in a portable device such as a telephone.

Further, since the conventional charger interface circuit requires at least three charging terminals, a spring is used to press-contact the charging terminal of a portable device such as a telephone with the terminal of an external charger. In this case, the pressing force of the spring is dispersed to three or more terminals, and there is a problem that the contact between the terminals may not be sufficient.

The present invention has been made in view of the above problems, and provides a charger interface circuit and a portable device in which the number of charging terminals in a portable device such as a telephone is two. It is intended to be.

[0016]

In order to achieve the above object, in the charger interface circuit according to the present invention, a charging terminal to which a positive voltage is applied at the time of charging and a negative electrode of the secondary battery are connected. A ground terminal connected to a point, connected between the charging terminal and the positive electrode of the secondary battery, and electrically connected with a low resistance to the charging terminal and the positive electrode of the secondary battery when in a closed state. Switch means capable of disconnecting an electrical connection between the charging terminal and the positive electrode of the secondary battery when the charging terminal is in an open state, wherein the charging terminal controls a voltage of the secondary battery during charging. The monitor terminal is also used as a monitor terminal for detection.

According to the present invention, since the charging terminal also serves as the monitor terminal, only the two terminals of the monitor / charging terminal and the ground terminal are required, and three terminals of the charging terminal, the ground terminal and the monitor terminal are required. As in the related art, the secondary battery can be charged while monitoring the voltage of the secondary battery during charging.

In the charger interface circuit according to the next invention, when an external charger is connected to the charging terminal and the ground terminal, a signal capable of holding the switch means in a closed state is generated. And signal generating means for controlling the opening and closing of the switch means by the generated signal.

According to the present invention, when an external charger is connected to the monitor / charging terminal and the ground terminal, the signal generating means generates a signal capable of holding the switch means in a closed state, thereby generating a switch. The means is kept closed.

In the charger interface circuit according to the next invention, when an external charger is connected to the charging terminal and the ground terminal, the switch means is alternately switched between a closed state and an open state. A signal generating means for generating a signal to be obtained and controlling the opening and closing of the switch means by the generated signal.

According to the present invention, when an external charger is connected to the monitor / charging terminal and the ground terminal, the signal generating means generates a signal capable of alternately switching the switch means between the closed state and the open state. As a result, the switch means is alternately switched between a closed state and an open state.

In the charger interface circuit according to the next invention, the switch means is a P-channel field-effect transistor having a low on-state resistance value, and the transistor is connected between a drain and a source of the transistor. A parasitic diode is connected so as to be in a forward direction from the charging terminal toward the positive electrode of the secondary battery.

According to the present invention, by switching on / off of the P-channel field-effect transistor, the electric connection between the monitor / charging terminal and the secondary battery and the interruption of the electric connection are performed, and the switching of the transistor is performed. The parasitic diode prevents a current from flowing to the outside via the monitor / charging terminal when the transistor is off.

In the charger interface circuit according to the next invention, when an external charger is connected to the charging terminal and the ground terminal, a signal having a relatively low potential level is generated. And a signal generating means for outputting the generated signal to the gate of the P-channel field effect transistor.

According to the present invention, when an external charger is connected to the monitor / charging terminal and the ground terminal, a signal of a relatively low level is generated by the signal generating means, and thereby the P-channel The field effect transistor is kept on.

In the charger interface circuit according to the next invention, when an external charger is connected to the charging terminal and the ground terminal, a signal having a relatively low potential and a signal having a relatively low potential are connected. The signal generating means alternately generates a high level signal and outputs the generated signal to the gate of the P-channel field effect transistor.

According to the present invention, when an external charger is connected to the monitor / charging terminal and the ground terminal, the signal generating means causes the signal having a relatively low potential and the signal having a relatively high potential to be at a high level. Are alternately generated, whereby the P-channel field effect transistor alternately switches between an on state and an off state.

[0028] In the charger interface circuit according to the next invention, the signal generating means is always kept on independently of a main power supply of a device including the charger interface circuit as one of the constituent elements. It is driven by a second power supply.

According to the present invention, the signal generating means is driven even when the main power supply of the device including the charger interface circuit as one of the constituent elements is off.

The charger interface circuit according to the next invention is provided with a reed switch that switches between a closed state and an open state in accordance with a change in magnetism accompanying attachment / detachment of the charger. The connection of the charger is detected based on the open / closed state.

According to the present invention, when an external charger is connected to the monitor / charge terminal and the ground terminal, the reed switch is closed, and the external charger is connected to the monitor / charge terminal and the ground terminal. When it is not, the connection of the charger is detected by opening the reed switch.

[0032] The charger interface circuit according to the next invention is provided with detection means for detecting that an external charger is connected to the charging terminal based on the potential of the charging terminal. It is.

According to the present invention, the detection means charges the battery based on the change in the potential of the monitor / charge terminal when the external charger is connected to the monitor / charge terminal and the ground terminal and when the external charger is not connected. The connection of the device is detected.

In the charger interface circuit according to the next invention, the potential of the drain and the source of the P-channel field-effect transistor are compared, and the potential of the charging terminal is higher than the potential of the positive electrode of the secondary battery. Also generates a signal having a relatively high level when the voltage is lower than the predetermined voltage value.On the other hand, when the difference between the potential on the charging terminal side and the potential on the positive electrode side of the secondary battery is within a predetermined range, the relative level is high. A voltage comparator for generating a signal having a low potential and outputting the generated signal to the gate of the transistor.

According to the present invention, the voltage comparator allows P
The potentials of the drain and the source of the channel field effect transistor are compared, and when the potential on the charging terminal side is lower than the potential on the positive side of the secondary battery by a predetermined voltage value or more, a signal having a relatively higher potential level is generated. As a result, the P-channel field-effect transistor is turned off. On the other hand, when the difference between the potential of the charging terminal and the potential of the positive electrode of the secondary battery is within a predetermined range, a signal having a relatively low potential level is output. Generated, thereby turning on the P-channel field effect transistor.

In the charger interface circuit according to the next invention, the signal generation means closes and opens the switch means in a state where an external charger is connected to the charging terminal and the ground terminal. The duty ratio of a signal that can be alternately switched to a state or the duty ratio of a signal having a relatively low potential level and a signal having a relatively high potential level can be arbitrarily changed during and after charging. It is something that has become.

According to the present invention, when the external charger is connected to the charging terminal and the ground terminal, the signal generating means can switch the switching means between the closed state and the open state alternately. Alternatively, the duty ratio between a signal having a relatively low potential level and a signal having a relatively high potential level can be arbitrarily changed during and after charging.

A portable device according to the next invention includes the above-mentioned charger interface circuit.

According to the present invention, since the portable device includes any one of the charger interface circuits described above, only two charging terminals are required.

In the portable device according to the next invention, the portable device is a portable telephone.

According to the present invention, since the mobile phone includes any one of the charger interface circuits described above, only two charging terminals are required.

[0042]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) FIG. 1 shows Embodiment 1 of a charger interface circuit according to the present invention. The charger interface circuit 200 is built in a mobile device, for example, a mobile phone, and has two charging terminals, a monitor / charging terminal 9 and a ground terminal 3.
The monitor / charging terminal 9 and the ground terminal 3 are both exposed on the outer surface of the mobile phone and are electrically connected to the secondary battery 7 in the mobile phone.

Between the monitor / charging terminal 9 and the positive electrode of the secondary battery 7, a P-channel FET (Field-Effect Transistor) having a low ON-state resistance (ON resistance) is provided.
sto: field effect transistor) 10 is connected. The drain and source of the P-channel FET 10 are
Each is connected to the monitor / charging terminal 9 and the positive electrode of the secondary battery 7. A resistance element 12 is connected between the source of the P-channel FET 10, that is, the positive electrode of the secondary battery 7 and the gate of the FET 10, so that the gate potential of the FET 10 is maintained at a predetermined potential when the FET 10 is off. It has become.

The P-channel FET 10 is connected such that the parasitic diode between the drain and the source is directed forward from the monitor / charge terminal 9 to the positive electrode of the secondary battery 7. This prevents current from flowing to the outside via the monitor / charging terminal 9 when the FET 10 is off.

The gate of the P-channel FET 10 has FE
A second digital transistor 11 for turning on / off T10 (switching between an on state and an off state) is connected. That is, the FET 10 is turned on / off based on the output signal of the second digital transistor 11. The second digital transistor 11 is turned on and off by the first digital transistor 5, the charger connection presence / absence detection circuit 210, and the control signal generation circuit 220, as described later.

Therefore, the P-channel FET 10 has a function as a switch means for electrically connecting the monitor / charging terminal 9 and the positive electrode of the secondary battery 7 and cutting off the electrical connection.

Also, the second digital transistor 11,
The first digital transistor 5, the charger connection presence / absence detection circuit 210, and the control signal generation circuit 220 have a function as a signal generation unit that controls opening and closing of the switch unit.

The input terminal of the first digital transistor 5 is connected to the monitor / charging terminal 9 and outputs a signal of a predetermined level when an external charger (not shown) is connected to the charging terminal. It has become. The output terminal of the digital transistor 5 is connected to a pull-up resistor 6
, And a charger connection presence / absence detection circuit 21 provided as an external circuit of the charger interface circuit 200 in a main body of a telephone or the like.
Connected to 0.

The charger connection presence / absence detection circuit 210 is connected to a control signal generation circuit 220 provided as an external circuit of the charger interface circuit 200 in a main body such as a portable telephone. This charger connection presence / absence detection circuit 210
Based on the output signal of the first digital transistor 5,
It detects connection of a charger (not shown) and outputs a detection signal. The charger connection presence / absence detection circuit 210 is also connected to other circuit blocks in a main body such as a mobile phone.

Therefore, the first digital transistor 5 and the charger connection presence / absence detection circuit 210 have a function as a detecting means for detecting that the charger is connected to the monitor / charging terminal 9.

The control signal generation circuit 220 is connected to the input terminal of the second digital transistor 11.
Then, based on the detection signal sent from the charger connection presence / absence detection circuit 210, the clock signal of the mobile phone is frequency-divided to generate a predetermined control signal 13, which is sent to the second digital transistor 11. Output. The control signal 13 is a signal whose potential is periodically switched between a “H (high)” level and a relatively low “L (low)” level. Based on this control signal 13, the second
Digital transistor 11 repeatedly turns on and off,
Thus, the FET 10 is also repeatedly turned on and off.

The control signal generation circuit 220 is driven by, for example, a clock power supply that operates independently of a power supply of a mobile phone or the like. The control signal 13 can be generated by dividing the frequency of the clock signal of the mobile phone. This is because charging may be performed in a state where the power of the mobile phone or the like is turned off.

The positive electrode and the negative electrode of the secondary battery 7 are connected to various parts in the main body of the telephone or the like, and the negative electrode of the secondary battery 7 is connected to the ground terminal 3 and the ground point.

FIG. 2 shows an example of the operation timing of the charger interface circuit 200 having the above configuration.
When an external charger (not shown) is connected to the charging terminal, an external charger (not shown) is connected to the monitor / charging terminal 9.
A positive voltage is applied. When a positive voltage is applied to the monitor / charging terminal 9, the first digital transistor 5, which has been in the off state, switches to the on state. As a result, the potential of the signal sent from the first digital transistor 5 to the charger connection presence / absence detection circuit 210 is relatively high “H”.
(High) level to a relatively low “L (Low)” level.

The charger connection presence / absence detecting circuit 210 has the potential “L” whose potential is relatively low from the first digital transistor 5.
When the (low) level signal is received, it is detected that an external charger (not shown) is connected to the charging terminal of the charger interface circuit 200, and the control signal generation circuit 22
A detection signal is output to 0.

When the control signal generation circuit 220 receives the detection signal from the charger connection presence / absence detection circuit 210, the control signal generation circuit 220 starts generating the control signal 13, and transmits the generated control signal 13 to the second
To the digital transistor 11.

The control signal 13 causes the second digital transistor 11 to periodically switch between a relatively high “H (high)” level potential and a relatively low “L (low)” level potential. Applied. As a result, the second digital transistor 11 periodically turns on and off.

In the circuit shown in FIG. 1, the second digital transistor 11 has a relatively low potential "L (low)" when a relatively high potential "H (high)" level signal is input. ) "Level signal is output and the P-channel FE
T10 is switched to the ON state to electrically connect the monitor / charging terminal 9 and the positive electrode of the secondary battery 7. On the other hand, the second digital transistor 11 has a relatively low potential “L”.
When a (low) level signal is input, an "H (high)" level signal having a relatively high potential is output, and the P-channel FET 10 is turned off to switch the monitor / charging terminal 9.
And the positive connection of the secondary battery 7 is cut off. Therefore, when the potential of the control signal 13 input to the second digital transistor 11 is at a relatively high “H (high)” level, the secondary battery 7 is charged.

The potential of the control signal 13 is relatively high "H".
(High) "level, that is, the P-channel FET 10
When the charger is removed while the power supply is in the ON state, as shown in FIG. 2, the P-channel FET 10 switches to the OFF state in synchronization with the falling of the control signal 13 immediately thereafter. This is F
Even if the charger is removed while ET10 is on, FET
Since 10 is in the ON state, the positive electrode of the secondary battery 7 and the monitor / charging terminal 9 remain electrically connected, and therefore, the potential of the input terminal of the first digital transistor 5 is relatively high at “H”. (High) "level.

When the first control signal 13 falls after the charger is removed, the gate potential of the P-channel FET 10 is switched to a relatively high "H (high)" level, and the P-channel FET 10 is turned on. Switch to off state. As a result, the electrical connection between the positive electrode of the secondary battery 7 and the monitor / charging terminal 9 is cut off, and the input and output potentials of the first digital transistor 5 become relatively low “L (low)” level, respectively. And a relatively high "H" level.

In the charger connection presence / absence detection circuit 210, the first
Of the input signal from the digital transistor 5 is relatively low from "L (low) level" to "H".
By switching to the “(high)” level, it is detected that the charger is not connected. Then, a detection signal indicating that the charger is not connected from the charger connection presence / absence detection circuit 210 to the control signal generation circuit 220. Is output, and based on the signal, the control signal 13 sent from the control signal generation circuit 220 to the second digital transistor 11 is
The “L (low)” level state where the potential is relatively low is maintained. The control signal 13 is held at a relatively low “L (low)” level until it is detected that the charger is connected again. In other words, until the connection of the charger is detected again, the P-channel FET 10
Hold the off state.

As described above, the control signal 13 is alternately switched between a relatively high “H (high)” level potential and a relatively low “L (low)” level potential. , The second digital transistor 11 repeats on / off, and the second digital transistor 1
1 alternately switches between a relatively low “L (low)” level potential and a relatively high “H (high)” level potential. Accordingly, the P-channel FET 10 is also repeatedly turned on and off. When the charger is removed while the FET 10 is in the on state, the FET 10 returns to the off state promptly, and the electrical connection between the positive electrode of the secondary battery 7 and the monitor / charging terminal 9 Connection can be interrupted.

On the other hand, when the potential of the control signal 13 is at a relatively low “L (low)” level,
When the charger is removed when the battery 10 is off, the secondary battery 7
Since the electrical connection between the positive electrode and the monitor / charge terminal 9 is immediately cut off, no voltage is applied to the monitor / charge terminal 9. Therefore, the potential of the input terminal of the first digital transistor 5 connected to the monitor / charging terminal 9 is switched from a relatively high “H (high)” level to a relatively low “L (low)” level. Accordingly, the output potential of the first digital transistor 5 switches from a relatively low “L (low)” level to a relatively high “H (high)” level.

In the charger connection presence / absence detection circuit 210, the potential of the input signal (output signal of the first digital transistor 5) is changed from a relatively low “L (low)” level to a relatively high “H (high)”. "By switching to the level,
It detects that the charger is not connected, and outputs a detection signal to control signal generation circuit 220. Thereby,
The control signal 13 sent from the control signal generation circuit 220 to the second digital transistor 11 has a relatively low potential “L (low)” level until it is later detected that the charger is connected again. And the P channel FE
T10 is kept off.

As described above, when the charger is disconnected, the FET 10 is kept connected until it is detected that the charger is connected again.
Is maintained in an off state, and the state in which the electrical connection between the positive electrode of the secondary battery 7 and the monitor / charging terminal 9 is cut off is maintained. Is designed to prevent the P-channel FET 10 from being overloaded when erroneously short-circuited by a metal or the like.

Here, the ratio of the time that the P-channel FET 10 is on and the time that it is off, that is, the duty ratio of the control signal 13 is appropriately set so that the time required for the full charge of the secondary battery 7 does not become long. Is selected. The cycle of the control signal 13 is determined when the charger is disconnected during charging.
It is appropriately selected so that it can be promptly detected and the electrical connection between the monitor / charging terminal 9 and the positive electrode of the secondary battery 7 can be switched to the cutoff state.

The charger connection presence / absence detection circuit 210
A charger connection detection signal is also sent to a control circuit (not shown) in the telephone body that controls on-hook and off-hook when the charger is attached and detached. Therefore, when the charger (not shown) is removed from the telephone connected to the charger (not shown), the P-channel FET 10 is turned off and the telephone automatically goes off-hook. When a charger (not shown) is connected to the off-hook telephone from which the (omitted) has been removed, the P-channel FET 10 switches to the on-state again, and the telephone automatically enters the on-hook state.

During charging, the voltage of the secondary battery 7 is detected by an external charger (not shown) via the monitor / charging terminal 9. Then, an external charger (not shown) is controlled according to the detected voltage. Thereby, the charging current supplied from an external charger (not shown) to the monitor / charging terminal 9 is controlled, and the secondary battery 7
Is fully charged without being overcharged.

Here, although not particularly shown, the external charger is a monitor / charging terminal 9 and a ground terminal 3 of the portable telephone.
Are provided respectively corresponding to.

As described in detail above, according to the first embodiment, since the monitor / charging terminal 9 also serves as a charging terminal and a monitor terminal, only two terminals, the monitor / charging terminal 9 and the ground terminal, are used. , A charging terminal, a ground terminal, and a monitor terminal, as in the prior art, which requires three terminals.
The secondary battery 7 can be charged while monitoring the voltage of the battery. Therefore, only two charging terminals, the monitor / charging terminal 9 and the ground terminal 3, are required, and the number of terminals of the charger interface circuit 200 is two. Can be reduced. Accordingly, the mounting space for the charging terminal is reduced, so that the size of the mobile phone can be further reduced, and the degree of freedom in design increases. In addition, the pressure load due to the terminals of the charger urged by the spring increases, and reliable contact between the terminals 3 and 9 of the mobile phone and the terminals of the charger is ensured.

According to the first embodiment, the electrical connection between monitor / charging terminal 9 and secondary battery 7 and the interruption of the electrical connection are made by switching on / off of P-channel field effect transistor 10. In addition, since the parasitic diode of the transistor 10 prevents the current from flowing to the outside via the monitor / charge terminal 9 when the transistor 10 is in the off state, the monitor / charge terminal 9 and the secondary battery 7 The switching operation for electrical connection and disconnection with the IC becomes faster, and current consumption is reduced.

According to the first embodiment, when an external charger is connected to monitor / charging terminal 9 and ground terminal 3, a signal having a relatively low potential and a signal having a relatively high potential are used. Since the level signal is alternately input to the gate of the P-channel field effect transistor 10 and the transistor 10 is alternately switched between the ON state and the OFF state, the level of the potential of the transistor 10 is relatively low. When a signal is input, the secondary battery 7 can be charged by an external charger, and the P-channel field-effect transistor 10 is immediately held in an off state when the charger is removed during charging. And a short circuit between terminals can be prevented.

According to the first embodiment, even if the main power supply of the portable telephone is in the off state, control signal generation circuit 22
0 is driven by a clock power supply or the like that operates independently of the main power supply of the mobile phone, so that the control signal 13 can be generated even when the power supply is off. It can be performed.

According to the first embodiment, control signal 1
3 is a signal whose potential is periodically switched between a relatively high “H (high)” level and a relatively low “L (low)” level, so that when the charger is disconnected during charging, ,
The control signal 13 causes the P-channel FET 10 to be quickly switched to the off state, thereby detecting that the charger is not connected by the charger connection presence / absence detection circuit 210. Until the detection, the P-channel FET 10 is kept in the off state, the electrical connection between the positive electrode of the secondary battery 7 and the monitor / charge terminal 9 is cut off, and the monitor / charge terminal 9 and the ground terminal 3 are connected. It is possible to prevent the P-channel FET 10 from being overloaded when erroneously short-circuited by a metal or the like.

It is needless to say that the present invention is not limited to the above configuration. For example, in the above-described embodiment, the control signal 13 is a signal that is periodically turned on and off. However, the present invention is not limited to this. For example, as shown in FIG. 3, it may be a signal that repeats on / off aperiodically. In that case, the period t from the fall of the control signal 13 to the next fall is preferably 1 second at the maximum.

In the above embodiment, the control signal 13
Is selected so that the time required for full charge of the secondary battery 7 is not prolonged. However, the present invention is not limited to this. Since there is no restriction on the time, for example, as shown in FIG. 4, after the charging is completed, the time of the “L (low)” level where the potential of the control signal 13 is relatively low may be lengthened (FIG. 4A), After completion, the time of the “H (high)” level in which the control signal 13 has a relatively high potential may be shortened (FIG. 4B). By doing so, when the charger is removed, it can be detected more quickly, and the operating performance of the mobile phone or the like is improved.

Further, the charger interface circuit 200
Is not limited to the configuration of the above embodiment, and various design changes can be made. For example, the switch means is a P-channel FET 1
The switching element is not limited to 0, and other switching elements may be used as long as the switching is controlled by the control signal 13 generated by the control signal generation circuit 220.

In the above-described embodiment, the control signal generation circuit 220 generates the control signal 13 by dividing the frequency of the clock signal of the mobile phone. However, the present invention is not limited to this. For example, as shown in FIG. , Inverter 30, resistance element 3
1. a diode 34 for changing the duty ratio of the control signal;
A resistor 32 connected in series to the anode of the diode 34; and a capacitor 33 connected between a common connection point between the input terminal of the inverter 30, one end of the resistor 31 and the cathode of the diode 34, and a ground point. The output terminal of the inverter 30, the other end of the resistance element 31, and the other end of the resistance element 32 are connected to the second digital transistor 1
It may be constituted by a simple oscillation circuit commonly connected to one input terminal. The inverter 30 may be supplied with driving power by a clock power supply or the like that operates independently of a power supply of a mobile phone or the like, or may be supplied with driving power from the monitor / charging terminal 9 side. It may be. Then, the charger interface circuit according to the present invention may incorporate this simple oscillation circuit.

(Second Embodiment) FIG. 6 shows a second embodiment of the charger interface circuit according to the present invention. This charger interface circuit 300 is different from the first embodiment in that, instead of the first digital transistor 5 and the pull-up resistor element 6, for example, the open (off) state and the closed (on) state are mutually changed by magnetism. And the control signal (the signal for turning on / off the second digital transistor 11) generated and output by the control signal generation circuit 320 is externally connected. When the charger (not shown) is connected, the electric potential “H
(High) level signal, which is a signal having a relatively low potential (L (Low) level) when a charger (not shown) is not connected. The same reference numerals are given to the same points as in the first embodiment, and the description thereof will be omitted.

One end of the reed switch 20 is connected to a charger connection presence / absence detection circuit 210 and is pulled up to a predetermined potential via a pull-up resistor element 21. The other end of the reed switch 20 is grounded.

When an external charger (not shown) is not connected to the charging terminal of the charger interface circuit 300, the reed switch 20 is opened (off).
In this state, a relatively high “H (high)” level potential is applied to the input terminal of the charger connection presence / absence detection circuit 210. On the other hand, when an external charger (not shown) is connected to the charging terminal, the reed switch 20 is closed (ON), and the input terminal of the charger connection presence / absence detection circuit 210 has a relatively low “L”. (Low) "level potential is applied. Charger connection presence / absence detection circuit 210 outputs a detection signal to control signal generation circuit 320 according to the potential of the input signal.

The control signal generation circuit 320 has a relatively high potential “H” when an external charger (not shown) is connected, based on the detection signal sent from the charger connection presence / absence detection circuit 210. (High) level signal, and when a charger (not shown) is not connected, a relatively low potential (L (low)) level signal is generated to the second digital transistor 11. Output. When an external charger (not shown) is connected, the second digital transistor 11 outputs a signal having a relatively low potential “L (low)” level to the P-channel FET 10.
When a charger (not shown) is not connected, a high (H) level signal having a relatively high potential is output to the FET 10. Therefore, P-channel FET1
0 is maintained in an on state when an external charger (not shown) is connected, and quickly returns to an off state when the charger (not shown) is removed, and the charger is connected again. Held off until

According to the second embodiment, the first embodiment
In the same manner as described above, only two charging terminals, the monitor / charging terminal 9 and the ground terminal 3, are required, and the number of terminals of the charger interface circuit 300 can be reduced to two. Since the size of the mobile phone is reduced, the size of the mobile phone can be further reduced, and the degree of freedom in design increases. In addition, the pressure load due to the terminals of the charger urged by the spring increases, and reliable contact between the terminals 3 and 9 of the mobile phone and the terminals of the charger is ensured.

According to the second embodiment, similarly to the first embodiment, P-channel field-effect transistor 10
Is used to electrically connect the monitor / charging terminal 9 to the secondary battery 7 and cut off the electrical connection. Therefore, the switching operation of the electrical connection and the cutoff between the monitor / charging terminal 9 and the secondary battery 7 is performed. And the current consumption is reduced.

According to the second embodiment, when an external charger is connected to monitor / charge terminal 9 and ground terminal 3, a signal having a relatively low potential level is supplied to P-channel field-effect transistor 10 And the transistor 10 is kept in the ON state, so that when a signal having a relatively low potential is input to the gate of the transistor 10, a secondary battery is used by an external charger. 7, the P-channel field-effect transistor 10 is kept in the off state immediately when the charger is disconnected during charging to detect that the charger is not connected by the reed switch 20. And a short circuit between terminals can be prevented.

(Third Embodiment) FIG. 7 shows a third embodiment of the charger interface circuit according to the present invention. This charger interface circuit 400 differs from the first embodiment in that a voltage comparator 40 for comparing the drain potential and the source potential of the P-channel FET 10 is provided, and the second digital transistor 11 is turned on and off. The point is that a control signal for switching between the states is generated by the voltage comparator 40. Therefore, in the third embodiment, a circuit for generating a signal for controlling the second digital transistor 11 (the control signal generation circuit 220 in FIG. 1) is unnecessary. The output signal of the first digital transistor 5 is sent to a charger connection presence / absence detection circuit in a main body of a mobile phone or the like, and is used for a purpose other than generation of a control signal for the second digital transistor 11. The same points as in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

The voltage comparator 40 compares the drain potential and the source potential of the P-channel FET 10 constantly or at predetermined intervals. When the potential on the monitor / charging terminal 9 side becomes lower than the potential on the positive electrode side of the secondary battery 7 by a predetermined voltage or more (that is, when the charger is removed), the voltage comparator 40 is set to the relative position. A low (L) level signal having a low potential is generated and output to the second digital transistor 11. Thereby, the second digital transistor 11
, The gate potential of the P-channel FET 10 becomes a relatively high “H (high)” level potential,
The FET 10 is turned off.

On the other hand, when the difference between the potential on the monitor / charging terminal 9 side and the potential on the positive electrode side of the secondary battery 7 is within a predetermined range (ie, when the charger is connected), the voltage comparison is performed. The device 40 generates a signal of “H (high)” level having a relatively high potential and outputs the signal to the second digital transistor 11. Thus, the output of the second digital transistor 11 becomes a relatively low “L (low)” level potential, and the FET 10 is turned on.

According to the third embodiment, the first embodiment
In the same manner as described above, only two charging terminals, the monitor / charging terminal 9 and the ground terminal 3, are required, and the number of terminals of the charger interface circuit 400 can be reduced to two. Since the size of the mobile phone is reduced, the size of the mobile phone can be further reduced, and the degree of freedom in design increases. In addition, the pressure load due to the terminals of the charger urged by the spring increases, and reliable contact between the terminals 3 and 9 of the mobile phone and the terminals of the charger is ensured.

According to the third embodiment, similarly to the first embodiment, P-channel field-effect transistor 10
Is used to electrically connect the monitor / charging terminal 9 to the secondary battery 7 and cut off the electrical connection. Therefore, the switching operation of the electrical connection and the cutoff between the monitor / charging terminal 9 and the secondary battery 7 is performed. And the current consumption is reduced.

According to the third embodiment, the potential of the monitor / charging terminal 9 and the potential of the secondary battery 7 are controlled by the voltage comparator 40.
Is within a predetermined range, a signal having a relatively low level is input to the gate of P-channel field-effect transistor 10, whereby transistor 10 is kept on. Therefore, when a signal having a relatively low potential is input to the gate of the transistor 10, the secondary battery 7 can be charged by the external charger and the potential of the monitor / charge terminal 9 side Is lower than the potential on the positive electrode side of the secondary battery 7 by a predetermined voltage value or more, a signal having a relatively high potential level is input to the gate of the P-channel field effect transistor 10, thereby turning off the transistor 10 Therefore, the P-channel field-effect transistor 10 can be held in the off state promptly when the charger is disconnected during charging. , It is possible to prevent short circuit between the terminals.

Further, according to the third embodiment, the presence or absence of the connection of the charger is detected by the voltage comparator 40, and the signal for turning on / off the P-channel field-effect transistor 10 is generated. Therefore, a signal for controlling the P-channel field-effect transistor 10 can be generated with a simple circuit configuration.

(Fourth Embodiment) FIG. 8 shows a fourth embodiment of the charger interface circuit according to the present invention. This charger interface circuit 500 is different from the first embodiment in that a control signal generation circuit 520 generates a control signal 13A obtained by inverting the logic of the control signal 13 in the first embodiment. Also, the point is that the gate of the P-channel FET 10 is connected only to the control signal generation circuit 520. The same points as in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

The P-channel FET 10 is turned off when the control signal 13A sent from the control signal generation circuit 520 has a relatively high “H (high)” level potential,
When the control signal 13A is at a relatively low “L (low)” level, the transistor is turned on.

According to the fourth embodiment, the first embodiment
In the same manner as described above, only two charging terminals, the monitor / charging terminal 9 and the ground terminal 3, are required, and the number of terminals of the charger interface circuit 400 can be reduced to two. Since the size of the mobile phone is reduced, the size of the mobile phone can be further reduced, and the degree of freedom in design increases. In addition, the pressure load due to the terminals of the charger urged by the spring increases, and reliable contact between the terminals 3 and 9 of the mobile phone and the terminals of the charger is ensured.

According to the fourth embodiment, similarly to the first embodiment, P-channel field-effect transistor 10
Is used to electrically connect the monitor / charging terminal 9 to the secondary battery 7 and cut off the electrical connection. Therefore, the switching operation of the electrical connection and the cutoff between the monitor / charging terminal 9 and the secondary battery 7 is performed. And the current consumption is reduced.

According to the fourth embodiment, similarly to the first embodiment, when the charger is removed during charging, P-channel field effect transistor 10 can be held in the off state promptly, Short-circuiting between terminals can be prevented.

According to the fourth embodiment, the number of elements constituting charger interface circuit 500 can be reduced as compared with the first embodiment.

Although the present invention has been described in detail with reference to the embodiments, the present invention is not limited to the above-described embodiments, and can be variously modified without departing from the scope of the invention. Needless to say.

In the above description, the present invention is mainly applied to the case where the present invention is applied to a charger interface circuit of a portable telephone. However, the present invention is not limited to this case. It can be used for portable devices and the like incorporating a secondary battery.

[0101]

According to the charger interface circuit of the present invention, only two terminals, a charging terminal and a ground terminal, which also serve as a monitor terminal, need three terminals of a charging terminal, a ground terminal and a monitor terminal. As in the related art, the secondary battery can be charged while monitoring the voltage of the secondary battery being charged, so that the number of terminals of the charger interface circuit can be reduced to two.

According to the charger interface circuit of the next invention, when an external charger is connected to the monitor / charging terminal and the ground terminal, the signal generation means causes
Since a signal capable of holding the switch means in the closed state is generated and the switch means is held in the closed state, the secondary battery can be charged by the external charger.

According to the charger interface circuit of the next invention, when an external charger is connected to the monitor / charging terminal and the ground terminal, the signal generation means causes
A signal is generated that can alternately switch the switch means between the closed state and the open state, whereby the switch means is alternately switched between the closed state and the open state, so that the external battery can be used to charge the secondary battery. In addition, when the connection of the charger is detected based on, for example, the potential of the monitor / charging terminal, the switch means can be promptly kept open when the charger is removed, and the terminal A short circuit between them can be prevented.

According to the charger interface circuit of the next invention, the ON / OFF state of the P-channel field-effect transistor
By switching off, the electrical connection between the monitor and charging terminal and the secondary battery and the interruption of the electrical connection are performed, and the parasitic diode of this transistor allows
When the transistor is in the off state, current is prevented from flowing to the outside via the monitor / charge terminal, so that the switching operation of electrical connection and disconnection between the monitor / charge terminal and the secondary battery is accelerated, Current consumption can be reduced.

According to the charger interface circuit of the next invention, when an external charger is connected to the monitor / charging terminal and the ground terminal, the signal generation means causes
Since a signal with a relatively low potential is generated and the P-channel field-effect transistor is kept on, a secondary battery can be charged by an external charger.

According to the charger interface circuit of the next invention, when an external charger is connected to the monitor / charging terminal and the ground terminal, the signal generating means causes
A signal having a relatively low potential level and a signal having a relatively high potential level are alternately generated, whereby the P-channel field effect transistor alternately switches between an on state and an off state. When the secondary battery can be charged and the connection of the charger is detected based on, for example, the potential of the monitor / charging terminal, the P-channel electric field effect is promptly obtained when the charger is removed. The transistor can be kept in an off state, so that a short circuit between terminals and the like can be prevented.

According to the charger interface circuit of the next invention, even if the main power supply of the device including the charger interface circuit as one of the constituent elements is in the off state,
Since the signal generation means is driven, the secondary battery can be charged even when the main power supply of the device is off.

According to the charger interface circuit of the next invention, when an external charger is connected to the monitor / charge terminal and the ground terminal, the reed switch is closed, and the monitor / charge terminal and the ground terminal are connected. When the external charger is not connected, the reed switch is opened to detect the connection of the charger, so that when the charger is disconnected, the monitor / charging terminal is immediately connected. Electrical connection to the secondary battery can be cut off, and short-circuiting between terminals can be prevented.

According to the charger interface circuit of the next invention, the change in the potential of the monitor / charge terminal when the external charger is connected to the monitor / charge terminal and the ground terminal and when the external charger is not connected is determined. Based on this, the connection of the charger is detected by the detection means, so when the charger is disconnected, the electrical connection between the monitor / charging terminal and the secondary battery is immediately cut off, and the Short circuits and the like can be prevented.

According to the charger interface circuit according to the next invention, the voltage comparator compares each potential of the drain and the source of the P-channel field-effect transistor,
When the potential on the charging terminal side is lower than the potential on the positive side of the secondary battery by a predetermined voltage value or more, a signal having a relatively high level is generated, thereby turning off the P-channel field-effect transistor, When the difference between the potential on the charging terminal side and the potential on the positive electrode side of the secondary battery is within a predetermined range, a signal of a relatively low potential level is generated, thereby turning on the P-channel field effect transistor. Therefore, when the charger is detached, the electrical connection between the monitor / charging terminal and the secondary battery is immediately cut off, and a short circuit between the terminals can be prevented. A signal is generated to turn the effect transistor on and off.

According to the charger interface circuit of the next invention, when the external charger is connected to the charging terminal and the grounding terminal, the signal generating means alternately switches the switching means between the closed state and the open state. Since the duty ratio of a switchable signal or the duty ratio between a signal having a relatively low potential level and a signal having a relatively high potential level can be arbitrarily changed during and after charging. By appropriately changing the duty ratio after charging is completed, when the charger is removed, it can be detected more quickly, and the operating performance of the mobile phone or the like is improved.

According to the portable device of the next invention, since the charger interface circuit is provided, the number of terminals for electrically connecting to the external charger is only two, and the number of terminals for charging is reduced. Since the mounting space is reduced, the size of the portable device can be further reduced, and the degree of freedom in design increases. In addition, the pressure load due to the terminals of the charger urged by the spring is increased, and reliable contact between the terminal of the portable device and the terminal of the charger is ensured.

According to the portable device according to the next invention, since the portable telephone has the charger interface circuit, the number of terminals for electrically connecting to the external charger is only two, and the charge Since the space for mounting the terminals is reduced, the size of the mobile phone can be further reduced, and the degree of freedom in design increases. In addition, the pressure load due to the terminals of the charger urged by the spring increases, and reliable contact between the terminal of the mobile phone and the terminal of the charger is ensured.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing Embodiment 1 of a charger interface circuit according to the present invention.

FIG. 2 is a timing chart showing an example of operation timing of the charger interface circuit.

FIG. 3 is an example of a waveform diagram of a control signal in the charger interface circuit.

FIG. 4 is an example of a waveform diagram of a control signal in the charger interface circuit.

FIG. 5 is a circuit diagram showing an example of a control signal generation circuit of the charger interface circuit.

FIG. 6 is a circuit diagram showing a charger interface circuit according to a second embodiment of the present invention.

FIG. 7 is a circuit diagram showing a third embodiment of the charger interface circuit according to the present invention.

FIG. 8 is a circuit diagram showing Embodiment 4 of a charger interface circuit according to the present invention.

FIG. 9 is a circuit diagram showing a conventional charger interface circuit.

[Explanation of symbols]

3 ground terminal, 5 first digital transistor (signal generating means, detecting means), 7 secondary battery, 9 monitor / charging terminal, 10 P-channel field effect transistor (switching means), 11 second digital transistor (signal generating means) Means), 20 reed switch, 40 voltage comparator, 200, 300, 400, 500 charger interface circuit, 210 charger connection presence / absence detection circuit (signal generation means, detection means), 220, 320 control signal generation circuit (signal generation means).

Claims (13)

[Claims] A charging terminal to which a positive voltage is applied during charging; a ground terminal connected to a ground point together with a negative electrode of the secondary battery; a charging terminal connected between the charging terminal and a positive electrode of the secondary battery;
When the charging terminal is in the closed state, the charging terminal and the positive electrode of the secondary battery can be electrically connected with a low resistance, and when the charging terminal is in the open state, the electrical connection between the charging terminal and the positive electrode of the secondary battery is cut off. A charger interface circuit, comprising: a switch unit capable of detecting a voltage of the secondary battery during charging. 2. A signal capable of holding the switch means in a closed state when an external charger is connected to the charging terminal and the ground terminal, and the generated signal is used to open and close the switch means. The charger interface circuit according to claim 1, further comprising a signal generating means for controlling. 3. When an external charger is connected to the charging terminal and the ground terminal, a signal that can switch the switch means between a closed state and an open state is generated, and the generated signal is used to generate the signal. 2. A signal generating means for controlling opening and closing of a switch means.
3. The charger interface circuit according to claim 1. 4. The switch means is a P-channel field-effect transistor having a low on-state resistance value, wherein the transistor has a parasitic diode between a drain and a source of the transistor connected to the charging terminal of the secondary battery. The charger interface circuit according to claim 1, wherein the charger interface circuit is connected so as to be in a forward direction toward the positive electrode. 5. When an external charger is connected to the charging terminal and the ground terminal, a signal having a relatively low level is generated, and the generated signal is used as a gate of the P-channel field effect transistor. 5. The charger interface circuit according to claim 4, further comprising a signal generating means for outputting the signal to the charger. 6. When an external charger is connected to the charging terminal and the ground terminal, a signal having a relatively low potential level and a signal having a relatively high potential level are generated alternately. 5. The charger interface circuit according to claim 4, further comprising signal generation means for outputting the generated signal to the gate of the P-channel field effect transistor. 7. The signal generating means is driven by a second power supply that is always kept on independently of a main power supply of a device including the charger interface circuit as one of the constituent elements. Claims 2 and 3,
7. The charger interface circuit according to 5 or 6. 8. A reed switch that switches between a closed state and an open state in accordance with a change in magnetism accompanying attachment / detachment of the charger, and that the charger is connected by the open / closed state of the reed switch. The charger interface circuit according to claim 2 or 5, wherein the charger interface circuit is adapted to detect. 9. A device according to claim 3, further comprising detecting means for detecting that an external charger is connected to the charging terminal based on the potential of the charging terminal.
3. The charger interface circuit according to claim 1. 10. The method according to claim 1, wherein the potential of the drain and the source of the P-channel field effect transistor are compared, and when the potential of the charging terminal is lower than the potential of the positive electrode of the secondary battery by a predetermined voltage value or more, the potential is relatively reduced. Generates a high-level signal, on the other hand, when the difference between the potential of the charging terminal side and the potential of the positive electrode side of the secondary battery is within a predetermined range, generates a signal of a relatively low level potential, The charger interface circuit according to claim 4, further comprising a voltage comparator that outputs the generated signal to a gate of the transistor. 11. The signal generating means includes: a duty ratio of a signal capable of alternately switching the switch means between a closed state and an open state when an external charger is connected to the charging terminal and the ground terminal; 4. The apparatus according to claim 3, wherein a duty ratio between the signal having a relatively low potential level and the signal having a relatively high potential level can be arbitrarily changed during and after charging. Or 6
3. The charger interface circuit according to claim 1. 12. A portable device comprising the charger interface circuit according to any one of claims 1 to 11. 13. The mobile device according to claim 12, wherein the mobile device is a mobile phone.