JP2011083093A - Charge control method and charge control circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a charge control circuit which charges a secondary battery to full even if the battery is charged by a charger different in specification. <P>SOLUTION: When the charger is connected to a charge terminal of a device to be charged, and when the charger applies a voltage, at least one of extending a charge time and restricting the operation of the device to be charged, according to the level of a constant current charged by the charger. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to control of charging a secondary battery used in a charging target device such as a mobile phone, and more particularly to control of charging performed by connecting chargers having different specifications.

  2. Description of the Related Art Today, mobile communication devices such as mobile phones and mobile information processing apparatuses have been improved in performance and multifunction, and power consumption has increased accordingly. In general, many of such devices use a secondary battery as a power source. In order to ensure sufficient battery driving time even with high power consumption, an increase in battery pack capacity has been taken.

  On the other hand, as another approach for securing the battery driving time, it is conceivable to increase charging opportunities. In mobile phones, various types of chargers are commercially available in addition to regular chargers provided by the manufacturer of the mobile phone or the carrier of the mobile phone. The charger is selected. For example, charging using multiple types of mobile devices such as mobile phones, portable information devices, portable game consoles, etc., charging for multiple types of mobile devices, dry batteries and other charged secondary batteries as power sources Or a charger that connects a USB (Universal Serial Bus) port of a computer and a charging port of a portable device with a cable. Although the last example is not strictly a charger, in this specification, an apparatus that performs charging in such a form is also treated as a charger.

  These various types of chargers do not have a uniform charging capability, and there is a fact that the charging capability varies depending on the charger. For this reason, the following problems may occur when charging with a charger having a low output current.

-The system load during charging exceeds the output current of the charger and charging is not performed.
-Even if charging is performed, the current flowing into the battery is insufficient, so the time required for full charging is extended compared to a regular charger.
In order to prevent overcharge, etc., if the device to be charged has a charge timer and the charge is limited to a certain time, a timeout occurs before full charge is reached.

  Patent Document 1 is given as a prior art document describing an invention related to the present invention.

JP 2001-228939 A

  The present invention has been made in view of such a situation, and the problem to be solved by the present invention is that a secondary battery can be fully charged even if charging is performed using a charger having different specifications. Is to provide a simple charge control circuit.

  In order to solve the above-described problems, the present invention has, as one aspect thereof, a stage in which a charger is connected to a charging terminal of a device to be charged, the charger applies a voltage, and a charging current for constant current charging performed by the charger. The charging control circuit includes a step in which the charging control circuit performs at least one of extending the charging time and restricting the operation of the charging target device according to the size of the charging. The charging current includes both the load current of the charging target device and the current flowing into the secondary battery.

  In addition, as another aspect of the present invention, when a charger is connected to the charging terminal of the charging target device and the charger applies a voltage, depending on the magnitude of the charging current of constant current charging performed by the charger, Provided is a charge control circuit that performs at least one of extension of charge time and restriction of operation of a device to be charged.

  According to the present invention, according to the magnitude of the charging current when the charger performs constant current charging, the charging time and the operation of the charging target device are appropriately controlled to extend the charging time or to notify the user, By restricting the operation of the charging target device such as limiting the luminance of the display device, the light emitting device, etc., the time for performing constant current charging is extended, or the power consumption of the charging target device during charging is reduced. Thereby, even if it charges a charging object apparatus using the charger whose output current is smaller than the regular charger of a charging object apparatus, a secondary battery can be fully charged.

2 is a block diagram of a charging control circuit 100. FIG. It is a block diagram of the charge control circuit 200 which is one embodiment of the present invention. It is a block diagram for demonstrating the structure of the adapter electric current detection circuit 112a. It is a block diagram for demonstrating the structure of the adapter electric current detection circuit 112b. It is a figure for comparing about the charge characteristic when it charges using two chargers from which charging capability differs in the state in which the load in the charging object apparatus has not generate | occur | produced under control of the charge control circuit. It is a figure for demonstrating the charge operation | movement which complete | finishes in the state which does not result in a full charge which generate | occur | produces when it charges in the state in which the load in the charging object apparatus is generating. It is a figure which shows the sequence of the current capability determination of a charger. It is a timing chart of the current capability determination of a charger. It is an example of the systematic countermeasure performed according to the determined current capability of the charger and the extension factor of the timer time. It is a block diagram of the charge control circuit 300 which is Example 2 of this invention. FIG. 5 is a diagram showing a current capability determination sequence of a charger by a charge control circuit 300.

  Prior to describing the charge control circuit 200 according to the embodiment of the present invention, the charge control circuit 100 will be described. The charging control circuit 100 is a circuit that is connected between the charger (or charging adapter) 1 and the battery pack 5 that is a secondary battery, and controls charging of the battery pack 5. The charge control circuit 100 is a circuit that is built in a charging target device (not shown) that operates by being built in or connected with the battery pack 5 as a power source. Examples of charging target devices include various devices that use a secondary battery as a power source, such as a mobile phone, a portable information terminal, and a mobile computer.

  The charge control circuit 5 includes a detection resistor 2, a field effect transistor (FET) 3, an FET 4, a charge current sense circuit 6, an amplifier 7, an amplifier 8, a buffer 9, an adapter voltage detection circuit 10, a current detection circuit 11, and a constant current reference. The circuit 12 includes a constant voltage reference circuit 13, a battery voltage detection circuit 14, a charge control logic circuit 15, and a timer circuit 16.

  Each part of the charge control circuit 100 will be described. The charger 1 supplies a charging current to the battery pack 5. The detection resistor 2 is a resistor for monitoring the charging current. The FET 3 is for controlling the charging current and the charging voltage. The FET 4 is for controlling on / off of charging. Since the output of the FET 4 is connected to the battery pack 5 and the charging target device, the charger 1 functions not only as a power source for charging the battery pack 5 but also as a system power source for the charging target device. Then, power is supplied to the charging target device while charging the battery pack 5. The charging current sense circuit 6 monitors the current from both ends of the detection resistor 2 and converts it into a voltage. The amplifier 7 controls the charging current for the FET 3. The amplifier 8 controls the charging voltage for the FET 8. The buffer 9 is used to turn on / off the FET 4. The adapter voltage detection circuit 10 monitors the voltage of the charger 1 and determines an abnormal voltage or a chargeable voltage. The current detection circuit 11 detects a limit current and a charge completion current from the charging current sensing circuit 6. The constant current reference circuit 12 determines a charging current. The constant voltage reference circuit 13 determines a charging voltage. The battery voltage detection circuit 14 measures the battery voltage of the battery pack 5 and confirms the state of charge. The timer circuit 16 measures the elapsed time after the start of charging, and notifies the charging control logic circuit 15 when the predetermined time comes, and the charging control logic circuit 15 that has received this notification ends the charging. The charge control logic circuit 15 includes signals from the adapter voltage detection circuit 10, current detection circuit 11, battery voltage detection circuit 14, and timer circuit 16, temperature information provided by a temperature sensor (not shown), and control by a CPU (not shown). The charging operation is controlled based on the above.

  A charge control circuit 200 according to an embodiment of the present invention will be described. The charge control circuit 200 is a circuit built in a charging target device similar to the charge control circuit 100, and includes an adapter current detection circuit 112 and a capability determination permission signal generation circuit 17 in addition to the configuration of the charge control circuit 100 described above. . The adapter current detection circuit 112 is a part of the current detection circuit 11 and is a circuit for determining the maximum current that the charger 1 can flow. Hereinafter, the maximum current that the charger 1 can flow is referred to as a limit current. In order to measure the limit current, it is necessary to refer to the battery voltage, and the capability determination permission signal generation circuit 17 is provided for this purpose. The capability determination permission signal generation circuit 17 is a circuit that generates a permission signal that permits execution of the charging capability determination of the charger 1 based on the monitor signal of the battery voltage detection circuit 14.

  There are two possible configurations for the adapter current detection circuit 112. 3 and 4 are shown as adapter current detection circuits 112a and 112b, respectively.

  Referring to FIG. 3, the adapter current detection circuit 112a compares the voltages converted by the charging current sensing circuit 6 with the comparators 1121, 1122, and 1123 having different threshold values, and based on these results. Then, the charge control logic circuit 15 determines in which range the magnitude of the charging current of the charger 1 is. Here, it is assumed that the threshold values of the comparators 1121, 1122, and 1123 are voltages corresponding to currents of 600 mA, 400 mA, and 200 mA, respectively.

  On the other hand, referring to FIG. 4, the adapter current detection circuit 112b converts the voltage converted by the charging current sensing circuit 6 into digital data by the A / D converter 1128 and charges based on the digital data. The control logic circuit 15 determines the magnitude of the charging current of the charger 1.

  In any configuration, the adapter current detection circuit 112 determines the limit current range or measures the limit current according to the permission signal generated by the capability determination permission signal generation circuit 17. The capability permission signal generation circuit 17 generates a permission signal based on the detection state of the battery voltage detection circuit 14.

  Next, regarding the outline of the operation of the charge control circuit 200, referring to FIG. 5 while comparing the respective charging characteristics when two types of chargers having different limit currents are connected as the charger 1, respectively. explain. For convenience of explanation, the charger with the smaller adapter current is called charger A and the charger with the larger adapter current is called charger B here. Both describe the charge characteristics from trickle charge with low battery voltage. For each of the chargers A and B, a graph showing the relationship between the charger voltage and time, a graph showing the relationship between the battery voltage and time, are shown in FIG. 5, and a graph showing the relationship between the charging current and time is shown in FIG. Show. In FIG. 5, it is assumed that the charger acts only as a power source for charging the battery pack, and does not act as a system power source for the device to be charged.

  When charger 1 is connected at time t0, trickle charging is performed with a small charging current until the battery voltage reaches a certain voltage. In FIG. 5, both the chargers A and B perform trickle charging until time t1 when the battery voltage reaches 3.0V.

  When the voltage exceeds a certain voltage, constant current charging starts, and charging is performed with a limit current, that is, the maximum current that can be passed through the charger 1 until the battery voltage reaches the full charge voltage. As shown in the charging current graph, the time required to reach the full charge voltage (4.2 V) varies depending on the difference between the limit currents of the chargers A and B. As shown in the graph of the battery voltage, the charger A having a small limit current reaches the full charge voltage at the time t4, but the charger B having a large limit current is at the time t2 until the full charge voltage is reached. The time required for charger B is shorter.

  When the battery voltage reaches the full charge voltage, it switches to constant voltage charge, and the FET 4 performs charging while controlling the gate voltage so as not to exceed the voltage. Referring to the battery voltage graph, the charger A performs constant voltage charging from time t4 to time t5, while the charger B performs constant voltage charging from time t2 to time t3.

  When it is detected that the charging current to the battery side is reduced by constant voltage charging and falls below a certain charging current, the charging is completed by turning off the FETs 3 and 4 respectively. The smaller the limit current of the charger, the longer the constant current charging time, resulting in longer charging time.

  In FIG. 5, it is assumed that the charger acts only as a power source for charging the battery pack and does not act as a system power source for the device to be charged. That is, all the electric power supplied by the charger is used for charging the battery pack 5. However, it is an ideal condition that the current from the charger is completely charged to charge the battery pack 5, and in fact, when charging starts and the battery voltage rises, the system of the charging target device starts up. Some current is consumed on the system side.

  FIG. 6 considers this. FIG. 6 shows charging characteristics when the system is simply consumed. In this case, in the section where the current flows in the system, the current charged in the battery is reduced accordingly, so that the battery voltage rises slowly. Therefore, the charging time becomes long.

  When the timer circuit 16 limits the charging time, it is conceivable that charging is terminated without reaching full charging due to timeout as shown in FIG. In particular, when the limit current of the charger is low and the current consumed by the system is large, it is considered that the end of charging before full charging frequently occurs due to timeout.

  In order to prevent such incomplete charging due to timeout, in the present invention, information on the limit current of the charger connected to the device to be charged is acquired during or prior to charging, The handling on the charging target device side or the charging control circuit side is changed according to the size.

  With reference to FIG. 7, the operation of the charging control circuit 200 when determining the current supply capability of the charger will be described.

  When the charger 1 is connected (step A1), the adapter voltage detection circuit 10 first checks the voltage of the charger 1 (step A2).

  If it is equal to or higher than the assumed charger voltage (step A2 Yes), the charging circuit is turned off to protect the system, that is, the control FET3 and FET4 are turned off (step A5). If the system seems to be on, the charging control logic circuit 15 displays a message on a screen display device such as an LCD of the charging target device via a CPU of the charging target device (not shown), and displays a predetermined LED. The user is notified (step A6) that a charger that outputs a charger voltage higher than the assumed voltage is connected due to lighting, blinking, etc., and charging is stopped as it is.

  If the charger voltage is not abnormal (step A2-No), the charging control logic circuit 15 confirms the battery voltage via the battery voltage detection circuit 14, and if the voltage is below a certain voltage (3V in this case), the battery protection circuit 15 Therefore, trickle charge is performed (step A4).

  When the battery voltage rises in trickle charging and becomes equal to or higher than a constant voltage (3 V), the charging control logic circuit 15 starts constant current charging performed through the constant current reference circuit 12, the amplifier 7, and the FET 3 (step A7).

  Thereafter, the charge control logic circuit 15 confirms the battery voltage again via the battery voltage detection circuit 14 (step A8). If the voltage reaches 4V close to the full charge voltage, the charge control logic circuit 15 determines the constant voltage reference circuit. 13. Continue charging through the amplifier 8 and the FET 3, and continue charging control until the charging current becomes a certain value or less, as in the normal charging operation, or that a predetermined time has elapsed since the start of charging. When the measurement is performed by the timer circuit 16, the charging is finished. Here, no extension of the set time for charging or handling at the charging target device is performed. Since this has already reached near the full charge voltage, even if the system load increases in the device to be charged in the future, there is a high possibility that it will reach full charge within the set time range of the timer. This is because it is considered unnecessary to deal with this.

  On the contrary, in the battery voltage confirmation in step A8, when the battery voltage does not reach 4V, it is a constant current charging region as shown in FIG. 5, and a current that can be passed through the charger adapter flows. By monitoring the current value at this point (step A9), it is determined whether or not a countermeasure is taken on the system side (step A10).

  Here, with reference to FIG. 8, the charging current measurement in step A9 will be further described. When the state of charge changes from trickle charge to constant current charge, that is, when the measurement result of the battery voltage by the battery voltage detection circuit 14 is 3.0 V or more and the full charge voltage or less, the capability determination permission signal generation circuit 17 outputs a permission signal. Generate. In FIG. 8, the capability determination permission signal generation circuit 17 outputs a permission signal in a range where the battery voltage is 3.1 to 4V. Upon receiving the permission signal, the charging control logic circuit 15 outputs a measurement request to the adapter current detection circuit 112. In response to the measurement request, the adapter current detection circuit 112 receives the charger 1 via the charging current sense circuit 6. Measure the current value. The current capability is determined with the measured current value region or value, and control by the system is performed.

  As for the current monitoring method, detection is performed by a comparator so as to monitor that the charging current is in a certain range as shown in FIG. 3, or the charging current is IV converted as shown in FIG. The current value can be monitored digitally by A / D conversion with voltage.

  For a charger having a high current capability, that is, a charger whose current value is higher than a current value estimated by monitoring, such as a regular charger of the device to be charged, the charging operation does not need to be particularly addressed.

  On the other hand, with regard to a low current capability such as an auxiliary charging adapter, countermeasures such as extension of the charging timer and limitation of a function having a high load are performed by control (step A11).

  An example of the countermeasure in step A11 is shown in FIG. In this example, if the limit current is 600 mA or more, no particular countermeasure is taken in terms of the system. If the limit current is 400 to 600 mA, the user is notified via the LED or LCD that the adapter current is low and it takes time to complete charging, and the timer setting time is increased by 1.5 times to increase the charging time. This prevents shortage of charging due to timeout. If the limit current is 200 to 400 mA, the set time of the timer is doubled and the user is notified accordingly. If the limit current is 200 mA or less, the timer setting time will be tripled and the LED and LCD brightness will be reduced, etc., so that the function limit for the charging target device will be provided, and the extended charging time and the function limitation of the charging target device will be notified Take measures such as notifying the user of the message.

  As described above, the notification to the user (step A12) is performed by informing the user that the charging time is long because the charging current of the adapter is low, or that the use of the function is restricted, via the LED or LCD. Recognize the situation and continue charging.

  In Example 1, the limit current of the charger was measured after charging of the secondary battery was started. On the other hand, in Example 2, the limit current of the charger is measured prior to charging the secondary battery. That is, in the second embodiment, before starting charging, the charging path (FET 4) to the battery pack 5 is shut off, and the maximum current that the charger 1 can flow is allowed to flow, thereby increasing the current capability of the charger. judge.

  Referring to FIG. 10, the charge control circuit 300 has a configuration in which the current drawing circuit 18 is added to the charge control circuit 200 and the capability determination permission signal generation circuit 17 is deleted.

  The current drawing circuit 18 includes a drawing line switch 181, a voltage feedback switching switch 182, a limiting resistor 183, and a constant current circuit 184.

  In the first embodiment, the determination of the current capability of the charger is for confirmation in the constant current charging region. However, in this embodiment, the determination is not necessary because the determination of the current capability is performed regardless of the battery voltage. The ability determination permission signal generation 17 is not provided.

  With reference to FIG. 11, the current capability determination operation of the charger by the charge control circuit 300 will be described. When the charger 1 is connected (step B1), the charge control logic circuit 15 checks the voltage of the charger 1 via the adapter voltage detection circuit 10 and determines whether the charger is abnormal (step B2).

  If the voltage of the charger 1 is abnormal, a user notification or the like is performed via the display device of the charging target device (step B3), and charging is stopped.

  If the voltage of the charger 1 is not abnormal, the SW 181 is turned on and the SW 182 is connected to the current drawing circuit side. At this time, the FET 3 is turned on, and the FET 4 is turned off so that no current flows to the battery side (step B4).

  Next, the constant current output from the constant current circuit 184 is supplied from the current drawing circuit 18 to the charger 1 (step B5). The magnitude of the constant current output by the constant current circuit 184 is a predetermined current that is larger than the limit current of the regular charger of the device to be charged. At this time, when current limitation is applied on the charger side, a current lower than the limited current cannot be flown, and a voltage drop occurs. On the other hand, a voltage drop does not occur in a charger that is not current limited.

  When a voltage drop occurs (step B6-Yes), the current capability of the charger 1 is determined (step B9). If the current that can be passed through the charger is in the range of the current value of a predetermined regular charger, no systematic countermeasure or user notification is performed. If the current that can be passed through the charger is below the normal range, the systematic countermeasure shown in FIG. 9 (step B10) and the notification to the user are performed (step B11). After these are completed, the setting of SW 181 and SW 182 is changed, current drawing is turned off (step B12), and normal charging is performed (step B13).

  On the other hand, when the voltage drop does not occur by the current drawing circuit 18 (step B6-No), the charging control circuit side limits the charging current so that the overcurrent does not flow to the battery side (step B7), and the user is abnormal. The adapter is notified (step B8). After these are completed, the setting of SW 181 and SW 182 is changed, current drawing is turned off (step B12), and charging is performed with the charging current limited on the electric control circuit side (step B13). At this time, regarding the limitation of the charging current, it is desirable that the charging current is less than half of the recommended current value in consideration of heat generation during charging.

  According to the first and second embodiments, it is possible to cope with the system such as extending the charge timer by determining that the current capability of the charger is small. In addition, it is possible to determine whether or not the charger is a regular product according to the voltage and current capability of the charger. Furthermore, it is possible to notify the user of information such as charging time depending on the capability of the charger, and to allow the user to recognize the charging status.

1 Charger (or charging adapter)
2 Sense resistor 3, 4 Field effect transistor (FET)
5 Battery pack 6 Charging current sense circuit 7, 8 Amplifier 9 Buffer 10 Adapter voltage detection circuit 11 Current detection circuit 12 Constant current reference circuit 13 Constant voltage reference circuit 14 Battery voltage detection circuit 15 Charge control logic circuit 16 Timer circuit 100, 200, 300 Charge control circuit

Claims (10)

A charger is connected to a charging terminal of the charging target device, and the charger applies a voltage; and
The charging control circuit includes a step of performing at least one of extending the charging time and limiting the operation of the charging target device according to the magnitude of the charging current of the constant current charging performed by the charger. Charge control method.   The determination as to whether or not it is necessary to determine the magnitude of the charging current is made in accordance with detection that the battery voltage has reached a predetermined voltage after starting constant current charging. Charge control method.   The charging control circuit includes a comparator and a logic circuit corresponding to one or more predetermined threshold values, and the logic circuit determines an operation according to a magnitude of a charging current according to a comparison result of the comparator. The charge control method according to claim 1.   The charging control circuit includes an analog-digital converter and a logic circuit that convert an analog value corresponding to the charging current into a digital value, and the logic circuit has a magnitude of a charging current according to the digital value output by the analog-digital converter. The charge control method according to claim 1, wherein an operation according to the operation is determined.   Prior to charging, the secondary battery and the charger are electrically disconnected, and a predetermined current larger than a current output when a predetermined regular charger of the charging target device performs constant current charging is set constant. The charge control method according to claim 1, wherein whether or not it is necessary to determine the magnitude of the charging current is determined according to whether or not a voltage drop occurs when flowing from the current circuit to the charger.   When a charger is connected to the charging terminal of the charging target device and the charger applies a voltage, the charging time is extended according to the magnitude of the charging current of constant current charging performed by the charger, and the charging target device The charge control circuit which performs at least one of the restriction | limiting of operation | movement of.   A charge control circuit that determines whether or not it is necessary to determine the magnitude of a charging current in response to detection that the battery voltage has reached a predetermined voltage after starting constant current charging.   A comparator and a logic circuit corresponding to one or more predetermined threshold values are provided, and the logic circuit determines an operation according to a magnitude of a charging current according to a comparison result of the comparator. 6. The charge control circuit according to 6.   An analog-digital converter that converts an analog value corresponding to the charging current into a digital value and a logic circuit are provided, and the logic circuit determines an operation according to the magnitude of the charging current according to the digital value output from the analog-digital converter. The charge control circuit according to claim 6. Prior to charging, a switch for electrically disconnecting the secondary battery and the charger,
A constant current circuit for flowing a predetermined current larger than a current output when a predetermined regular charger of the charging target device performs a constant current charge to the charger;
A logic circuit that determines whether or not the magnitude of the charging current needs to be determined according to whether or not a voltage drop occurs when the predetermined current flows from the constant current circuit to the charger. The charge control circuit according to claim 6.

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