JP2012090472A - Portable device, power supply circuit, and charge control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the generation of overcharge and overdischarge with a smaller number of components.SOLUTION: A portable device of this invention includes an operation part to be supplied with power and operated and a power supply part for supplying power to the operation part. The power supply part includes: a secondary battery for charging the power supplied from an external charger and supplying it to the operation part; a resistor whose one end is connected to the secondary battery and other end is connected to the charger and the operation part; a current detection part for detecting the current value of a current flowing to the resistor and outputting current value data indicating the detected current value; a charge control part for controlling the current value of the current inputted from the charger when the power is supplied from the charger corresponding to the current value indicated by the current value data; and an overcurrent protection part for determining whether or not the current value indicated by the current value data is a prescribed threshold or larger and stopping power supply to the operation part from the secondary battery through the resistor when it is equal to or larger than the threshold.

Description

  The present invention relates to a portable device using a secondary battery as a power source, a power supply circuit, and a charge control method.

  Japanese Patent Application Laid-Open No. 2008-104351 discloses a portable device that uses a secondary battery such as a lithium ion battery as a power source. The secondary battery can charge the power supplied from the outside and supply it to the portable device. Therefore, according to the portable device disclosed in Patent Document 1, even when the battery voltage of the secondary battery is reduced, it can be repeatedly used as a power source by charging.

  FIG. 12 shows a general configuration of a portable device using a secondary battery as a power source.

  A mobile device 20 illustrated in FIG. 12 includes a power supply unit 200 and an operation unit 300. In FIG. 12, a thick solid line indicates a power supply line for power supply, and a dotted line indicates a signal line for transmission of a control signal.

  The power supply unit 200 supplies power to the operation unit 300 to operate the operation unit 300. Note that the operation unit 300 is, for example, a communication unit that transmits and receives radio waves, a display unit that displays an image, and the like when the mobile device 20 is a mobile phone.

  Next, the configuration of the power supply unit 200 will be described.

  The power supply unit 200 includes a diode 210, field effect transistors (FETs) 220 and 250, resistors 230 and 260, a battery pack 240, a charge control unit 270, and an overcurrent protection unit 280.

  The diode 210 can be connected to a charger 30 that converts electric power supplied from a commercial power source into electric power in a format that matches the portable device 20 and outputs the electric power, and rectifies and outputs current input from the charger 30. .

  The FET 220 is turned on or off under the control of the charge control unit 270, and passes or blocks the current output from the diode 210.

  A battery pack 240 is connected to one end of the resistor 230. The charger 30 is connected to the other end of the resistor 230 via the diode 210 and the FET 220, and the operation unit 300 is further connected to the resistor 230 via the FET 250 and the resistor 260.

  The battery pack 240 is one in which one or a plurality of secondary batteries are housed in a package, and is charged by inputting a current from the charger 30 via the diode 210, the FET 220, and the resistor 230. Further, the battery pack 240 outputs a current to the operating unit 300 via the resistor 230, the FET 250, and the resistor 260.

  The FET 250 is turned on or off in accordance with the control of the overcurrent protection unit 280, and passes or blocks the current input to the operation unit 300.

  The FET 250 is connected to one end of the resistor 260, and the operation unit 300 is connected to the other end of the resistor 260.

  The charging control unit 270 detects the battery voltage of the battery pack 240, the presence / absence of output of current from the diode 210, and the current value of the current flowing through the resistor 230. Note that the charging control unit 270 includes a current detection unit 271 that detects the current value of the current flowing through the resistor 230.

  In addition, when the charger 30 is connected to the diode 210 and a current is output from the diode 210, the charge control unit 270 turns on the FET 220 and controls the FET 220 according to the current value detected by the current detection unit 271. Thus, the current value of the current output from the FET 220 is controlled.

  Note that when the battery pack 240 is charged so that the battery voltage exceeds a predetermined upper limit voltage (hereinafter referred to as overcharge), the characteristics of the secondary battery deteriorate. Therefore, the charge control unit 270 can prevent overcharging by controlling the current value of the current output from the FET 220 so that the battery voltage does not exceed the upper limit voltage.

  Further, a large current (hereinafter referred to as overcurrent) that does not flow during normal operation may flow to the operation unit 300 due to an abnormality such as a wiring short in the operation unit 300. When the overcurrent flows, there is a possibility that the circuit in the operation unit 300 may be adversely affected.

  The overcurrent protection unit 280 includes a current detection unit 281 that detects the current value of the current flowing through the resistor 260, and determines whether or not an overcurrent is flowing based on the current value detected by the current detection unit 281. If it is determined that an overcurrent is flowing, the FET 250 is turned off. By turning off the FET 250, the power supply line is cut off, and an overcurrent can be prevented from flowing through the operating unit 300.

JP 2008-104351 A

  By the way, in general, a reduction in the number of parts is required in order to reduce the size and cost of the portable device. However, since the portable device 20 includes two resistors and two current detection units, the number of components is reduced. There is a problem that increases.

  An object of the present invention is to provide a portable device, a power supply circuit, and a charge control method that can solve the above-described problems.

In order to achieve the above object, the portable device of the present invention
A portable device including an operation unit that operates by being supplied with power, and a power supply unit that supplies power to the operation unit,
The power supply unit is
A secondary battery that charges the power supplied from an external charger and supplies the power to the operating unit;
One end is connected to the secondary battery and the other end is connected to the charger and the operating unit,
A current detector that detects a current value of a current flowing through the resistor and outputs current value data indicating the detected current value;
A charge control unit that controls a current value of a current input from the charger when power is supplied from the charger according to a current value indicated by the current value data;
It is determined whether or not the current value indicated by the current value data is equal to or greater than a predetermined threshold value. When the current value is equal to or greater than the threshold value, power supply from the secondary battery to the operation unit via the resistor is stopped. An overcurrent protection unit.

In order to achieve the above object, the power supply circuit of the present invention comprises:
A power supply circuit of a portable device having an operation unit and a secondary battery that charges and supplies the supplied power to the operation unit,
One end is connected to the secondary battery, the other end is connected to a charger and the operating unit, a resistor,
A current detector that detects a current value of a current flowing through the resistor and outputs current value data indicating the detected current value;
A charge control unit that controls a current value of a current input from the charger when power is supplied from the charger according to a current value indicated by the current value data;
It is determined whether or not the current value indicated by the current value data is equal to or greater than a predetermined threshold value. When the current value is equal to or greater than the threshold value, power supply from the secondary battery to the operation unit via the resistor is stopped. An overcurrent protection unit.

In order to achieve the above object, the charge control method of the present invention comprises:
A charge control method applied to a portable device having an operation unit that operates by being supplied with power, and a secondary battery that supplies power supplied from an external charger to the operation unit,
The current detection unit detects a current value of a current flowing through a resistor having one end connected to the secondary battery and the other end connected to the charger and the operation unit,
The charge control unit controls the current value of the current input from the charger when power is supplied from the charger according to the current value indicated by the current value data,
The overcurrent protection unit determines whether or not the current value indicated by the current value data is equal to or greater than a predetermined threshold value, and if the current value is equal to or greater than the threshold value, the operation unit via the resistor from the secondary battery. Stop power supply to.

  According to the present invention, it is possible to prevent the occurrence of overcharge / overcurrent with a smaller number of parts.

It is a block diagram which shows the structure of the portable apparatus of one Embodiment of this invention. It is a block diagram which shows the structure of the electric current detection part and overcurrent protection part which are shown in FIG. It is a figure which shows the monitor voltage at the time of charging / discharging output from the amplifier shown in FIG. It is a figure which shows the overcurrent threshold set by the threshold value setting part shown in FIG. It is a figure which shows operation | movement of the amplifier shown in FIG. 2, a charge control part, and an overcurrent protection part. It is a flowchart which shows operation | movement of the portable apparatus shown in FIG. 3 is a timing chart illustrating an example of the operation of the mobile device illustrated in FIG. 1. 6 is a timing chart showing another example of the operation of the mobile device shown in FIG. 1. 6 is a timing chart showing still another example of the operation of the mobile device shown in FIG. 6 is a timing chart showing still another example of the operation of the mobile device shown in FIG. 1. It is a block diagram which shows the structure of the power supply circuit of one Embodiment of this invention. It is a block diagram which shows the structure of a related portable apparatus.

  EMBODIMENT OF THE INVENTION Below, the form for implementing this invention is demonstrated with reference to drawings.

  FIG. 1 is a block diagram illustrating a configuration of a mobile device 10 according to an embodiment of the present invention. In FIG. 1, a thick solid line indicates a power supply line, a dotted line indicates a signal line, and the same components as those in FIG.

  The portable device 10 of this embodiment is different from the portable device 20 only in that the power supply unit 200 is changed to the power supply unit 100.

  The power supply unit 100 supplies power to the operation unit 300.

  Next, the configuration of the power supply unit 100 will be described.

  The power supply unit 100 includes a diode 110, FETs 120 and 150, a resistor 130, a battery pack 140, a current detection unit 160, a charge control unit 170, and an overcurrent protection unit 180.

  The diode 110 can be connected to the charger 30 and rectifies and outputs the current input from the charger 30.

  The FET 120 is turned on or off under the control of the charge control unit 170, and passes or blocks the current output from the diode 110.

  A battery pack 140 is connected to one end of the resistor 130 (hereinafter referred to as node A). The other end of the resistor 130 (hereinafter referred to as node B) is connected to the charger 30 via the diode 110 and the FET 120, and is further connected to the operating unit 300 via the FET 150.

  The battery pack 140 is one in which one or a plurality of secondary batteries are housed in a package, and is charged by inputting a current from the charger 30 via the diode 110, the FET 120, and the resistor 130. Further, the battery pack 140 outputs a current to the operation unit 300 via the resistor 130 and the FET 150.

  The FET 150 is turned on or off according to the control of the overcurrent protection unit 180, and passes or blocks the current input to the operation unit 300.

  Current detection unit 160 detects a current value of a current flowing through resistor 130 (hereinafter referred to as a resistance current), and outputs current value data indicating the detected current value to charge control unit 170 and overcurrent protection unit 180.

  The charge control unit 170 detects the battery voltage of the battery pack 140 and the presence / absence of power supply from the external charger 30. Note that the charging control unit 170 detects the presence / absence of external power supply based on the presence / absence of a current output from the diode 110. When the external power supply is detected, the charging control unit 170 turns on the FET 120 and controls the FET 120 according to the current value indicated by the current value data output from the current detection unit 160. Specifically, the charge control unit 170 controls the FET 120 to charge the battery pack 140 by inputting a constant current until the battery voltage reaches the upper limit voltage (constant current charging). After reaching the voltage, charging (constant voltage charging) is performed by inputting a current that maintains the upper limit voltage.

  In addition, the charging control unit 170 notifies the overcurrent protection unit 180 of the presence or absence of external power supply.

  Note that the configuration and operation of the charging control unit 170 are well known to those skilled in the art and are not directly related to the present invention, and thus detailed description thereof is omitted.

  The overcurrent protection unit 180 determines whether or not an overcurrent is flowing according to the current value indicated by the current value data output from the current detection unit 160, and determines that the overcurrent is flowing. FET 150 is turned off. By turning off the FET 150, the power supply line is cut off, and an overcurrent can be prevented from flowing through the operating unit 300.

  Next, the configuration of the current detection unit 160 and the overcurrent protection unit 180 will be described.

  FIG. 2 is a block diagram illustrating the configuration of the current detection unit 160 and the overcurrent protection unit 180.

  First, the configuration of the current detection unit 160 will be described.

  The current detection unit 160 illustrated in FIG. 2 includes an amplifier 161, an offset voltage source 162, an A / D converter 163, and an averaging unit 164.

  The amplifier 161 periodically monitors the potential difference between the potential IN_A of the node A and the potential IN_B of the node B, and outputs a voltage corresponding to the monitored potential difference (hereinafter referred to as a monitor voltage) to the A / D converter 163. Note that the power supply voltage of the amplifier 161 is Vcc.

  The offset voltage source 162 inputs an offset voltage to the amplifier 161 in order to offset the potential difference between the potential IN_A and the potential IN_B. Note that the voltage value of the offset voltage is half the power supply voltage of the amplifier 161 (Vcc / 2).

  Here, the direction in which the resistance current flows is opposite between when the battery pack 140 is charged and when it is discharged. That is, when the direction from node A to node B is a positive direction, the resistance current flows in the negative direction during charging and flows in the positive direction during discharging. Therefore, at the time of charging, the potential IN_A <the potential IN_B, so the monitor voltage becomes a negative voltage. When the monitor voltage becomes negative, AD conversion by the A / D converter 163 becomes difficult. Therefore, the offset voltage source 162 inputs the offset voltage to the amplifier 161 to prevent the monitor voltage from becoming negative.

  FIG. 3 shows the monitor voltage output from the amplifier 161 when the battery pack 140 is charged / discharged.

  When charging / discharging is not performed, a resistance current does not flow, and potential IN_A = potential IN_B. In this case, the voltage value of the monitor voltage is Vcc / 2.

  During charging, a resistance current in the negative direction flows, and potential IN_A <potential IN_B. In this case, the voltage value of the monitor voltage is not less than 0 and less than Vcc / 2. Further, the larger the resistance current value, the closer to 0, and the smaller the resistance current value, the closer to Vcc / 2.

  At the time of discharge, a resistance current in the positive direction flows, and potential IN_A> potential IN_B. In this case, the voltage value of the monitor voltage is greater than Vcc / 2 and less than or equal to Vcc. Further, the larger the resistance current value, the closer to Vcc, and the smaller the resistance current value, the closer to Vcc / 2.

  Therefore, the voltage value of the monitor voltage has a one-to-one correspondence with the current value of the resistance current.

  Referring to FIG. 2 again, the A / D converter 163 performs AD conversion of the voltage value of the monitor voltage and outputs it to the averaging unit 164.

  The averaging unit 164 averages the voltage value of the monitor voltage after AD conversion output from the A / D converter 163 within a predetermined period, and outputs it to the charge control unit 170 and the overcurrent protection unit 180. Here, as described above, the voltage value of the monitor voltage and the current value of the resistance current have a one-to-one correspondence. Therefore, the voltage value of the monitor voltage output from the averaging unit 164 indicates the current value of the resistance current. This corresponds to the current value data described above. Note that by performing averaging, it is possible to prevent malfunctions by sampling the voltage value of the instantaneous monitor voltage.

  Next, the configuration of the overcurrent protection unit 180 will be described.

  The overcurrent protection unit 180 illustrated in FIG. 2 includes a threshold setting unit 181, a comparator 182, and a determination unit 183.

  The threshold setting unit 181 sets a threshold (hereinafter referred to as an overcurrent threshold) for determining whether or not an overcurrent is flowing in the comparator 182.

  The comparator 182 compares the voltage value of the monitor voltage output from the averaging unit 164 with the overcurrent threshold set by the threshold setting unit 181 and notifies the determination unit 183 of the result.

  When the comparator 182 notifies that the voltage value of the monitor voltage is larger than the overcurrent threshold, the determination unit 183 determines that an overcurrent is flowing, and turns off the FET 150.

  Here, the threshold setting unit 181 sets different overcurrent thresholds in the comparator 182 depending on whether or not external power is supplied.

  FIG. 4 is a diagram illustrating the overcurrent threshold set by the threshold setting unit 181.

  As illustrated in FIG. 4, the threshold setting unit 181 sets an overcurrent threshold 1 when there is no external power supply, and is output from the FET 120 rather than the overcurrent threshold 1 when there is an external power supply. The overcurrent threshold 2 is set lower by the current value (hereinafter referred to as the limiter value) of the maximum current (hereinafter referred to as the limiter current). The limiter value is the smaller current value of the maximum current values that can be output by the charger 30 or the FET 120.

  When the charger 30 is connected, power is supplied from the charger 30 to the operation unit 300 with priority. Here, for example, it is assumed that the load current of the operation unit 300 increases due to a wiring short in the operation unit 300 and an overcurrent flows. In this case, if the load current is larger than the limiter current, a current is also output from the battery pack 140.

  In the portable device 20 shown in FIG. 12, whether or not an overcurrent flows according to the current value of the current flowing through the resistor 260, that is, the current value of the current output from the charger 30 and the battery pack 240. For the determination, only the same overcurrent flows regardless of the presence or absence of external power supply.

  On the other hand, according to the present embodiment, the voltage value of the monitor voltage that the determination unit 183 compares with the overcurrent threshold corresponds to the current value of the current output from the battery pack 140 and is output from the charger 30. Current is not reflected. Therefore, if the same overcurrent threshold is set in the comparator 182 regardless of the presence or absence of external power supply, when there is external power supply, an overcurrent larger by the limiter value flows than when there is no external power supply. End up.

  Therefore, by making the overcurrent threshold 2 lower than the overcurrent threshold 1 by the limiter value, the overcurrent that flows when there is an external power supply can be made comparable to that when there is no external power supply.

  Next, the operation of the mobile device 10 of the present embodiment will be described.

  Hereinafter, a state where the charger 30 is not connected and power is supplied only from the battery pack 140 is referred to as a state A. A state in which the charger 30 is connected and power is supplied to the operating unit 300 and the battery pack 140 is charged by the charger 30 is referred to as state B. A state in which the charger 30 is connected and power is supplied from the charger 30 and the battery pack 140 to the operation unit 300 is referred to as a state C. In state C, a state in which an overcurrent flows through the operating unit 300 is referred to as state D.

  FIG. 5 is a diagram illustrating operations of the amplifier 161, the charging control unit 170, and the overcurrent protection unit 180 from the state A to the state D.

  In the state A, a resistance current flows from the node A to the node B, and the potential IN_A> the potential IN_B, so that the monitor voltage becomes higher than Vcc / 2. Further, since there is no external power supply, the charging control unit 170 turns off the FET 120 and stops its operation. Further, the overcurrent protection unit 180 turns on the FET 150. When the FET 150 is turned on, power is supplied from the battery pack 140 to the operation unit 300, and the overcurrent protection unit 180 monitors overcurrent according to the current value data output from the current detection unit 160.

  In the state B, a resistance current flows from the node B to the node A, and the potential IN_A <the potential IN_B. Therefore, the monitor voltage is less than Vcc / 2. In addition, when the external power supply is detected, the charging control unit 170 turns on the FET 120 and controls the current value of the current output from the FET 120. The overcurrent protection unit 180 turns on the FET 150 and monitors the overcurrent.

  In the state C, current is also output from the battery pack 140, so that a resistance current flows in the direction from the node A to the node B, the potential IN_A> the potential IN_B, and the monitor voltage becomes larger than Vcc / 2. In addition, the charging control unit 170 turns on the FET 120 and controls the current value of the current output from the FET 120. The overcurrent protection unit 180 turns on the FET 150 and monitors the overcurrent.

  In the state D, since an overcurrent flows, the resistance current flowing from the node A to the node B becomes larger than that in the state C. In this case, the potential difference between the potential IN_A and the potential IN_B is larger than the potential difference in the state C. Therefore, the monitor voltage is close to Vcc (>> Vcc / 2). When the overcurrent protection unit 180 detects that an overcurrent is flowing, the overcurrent protection unit 180 turns off the FET 150 and notifies the charge control unit 170 that the overcurrent is flowing. When notified that the overcurrent is flowing, the charging control unit 170 turns off the FET 120 and stops the operation.

  FIG. 6 is a flowchart showing the operation of the mobile device 10.

  When the battery pack 140 is attached, the overcurrent protection unit 180 turns on the FET 150 (step S1). When the FET 150 is turned on, power is supplied to the operation unit 300.

  The amplifier 161 outputs the monitor voltage to the A / D converter 163. The A / D converter 163 performs AD conversion on the voltage value of the monitor voltage, and outputs it to the averaging unit 164. The averaging unit 164 averages the voltage value of the monitor voltage output from the A / D converter 163 (step S2), and outputs the average value to the charge control unit 170 and the overcurrent protection unit 180.

  The comparator 182 compares the voltage value of the monitor voltage output from the averaging unit 164 with a predetermined overcurrent threshold (step S3), and notifies the determination unit 183 of the result.

  When it is notified that the voltage value of the monitor voltage is larger than the overcurrent threshold (step S3: Yes), the determination unit 183 turns off the FET 150. Moreover, the overcurrent protection unit 180 notifies the charge control unit 170 that an overcurrent is flowing. In response to the notification from the overcurrent protection unit 180, the charge control unit 170 turns off the FET 120 (step S4).

  On the other hand, when it is notified that the voltage value of the monitor voltage is smaller than the overcurrent threshold (step S3: No), the determination unit 183 determines that no overcurrent is flowing, and the charge control unit 170 receives external power. The presence or absence of supply is detected (step S5).

  When there is no external power supply (step S5: No), the charging control unit 170 notifies the overcurrent protection unit 180 to that effect and turns off the FET 120. The threshold setting unit 181 receives the notification from the charging control unit 170 and sets the overcurrent threshold 1 in the comparator 182 (step S6).

  On the other hand, when there is an external power supply (step S5: Yes), the charging control unit 170 notifies the overcurrent protection unit 180 to that effect and turns on the FET 120. The threshold setting unit 181 receives the notification from the charging control unit 170 and sets the overcurrent threshold 2 in the comparator 182 (step S7).

  After step S6 or step S7, the process returns to step S2.

  Next, operations of the threshold setting unit 181 and the FETs 120 and 150 will be described with reference to FIGS.

  First, an operation when an overcurrent flows in the state A will be described with reference to FIG.

  7A is a load current timing chart, FIG. 7B is a monitor voltage and overcurrent threshold timing chart, and FIG. 7C is an ON / OFF timing chart of the FETs 120 and 150. is there. In FIG. 7B, the alternate long and short dash line indicates the overcurrent threshold set in the comparator 182.

  In the state A, since the current is output only from the battery pack 140, the resistance current and the load current are equal. Further, the temporal change in the current value of the load current and the temporal change in the voltage value of the monitor voltage have a similar relationship.

  The overcurrent protection unit 180 turns on the FET 150 in order to supply power to the operation unit 300.

  Since there is no external power supply, the charging control unit 170 notifies the overcurrent protection unit 180 to that effect and turns off the FET 120. The threshold setting unit 181 receives the notification from the charging control unit 170 and sets the overcurrent threshold 1 in the comparator 182.

  The comparator 182 compares the voltage value of the monitor voltage with the overcurrent threshold value 1.

  Here, when the voltage value of the monitor voltage exceeds the overcurrent threshold 1 at time t11, the determination unit 183 determines that an overcurrent has flowed and turns off the FET 150. When the FET 150 is turned off, the power supply line is cut off. As shown in FIG. 7A, the load current becomes zero, and when the load current becomes zero, the resistance current also becomes zero. As shown, the voltage value of the monitor voltage is Vcc / 2.

  Next, the operation in the state B will be described.

  8A is a load current timing chart, FIG. 8B is a resistance current timing chart, and FIG. 8C is a monitor voltage and overcurrent threshold timing chart. 8 (d) is an on / off timing chart of the FETs 120 and 150. FIG. In FIG. 8C, the alternate long and short dash line indicates the overcurrent threshold set in the comparator 182.

  It is assumed that the charger 30 is not connected from time t0 to t21.

  The overcurrent detection unit 180 turns on the FET 150 in order to supply power to the operation unit 300.

  Since there is no external power supply, the charging control unit 170 notifies the overcurrent protection unit 180 to that effect and turns off the FET 120. The threshold setting unit 181 receives the notification from the charging control unit 170 and sets the overcurrent threshold 1 in the comparator 182.

  Assuming that the charger 30 is connected at time t21, the charging control unit 170 detects external power supply, turns on the FET 120, controls the current value of the current output from the FET 120, and performs constant current / constant voltage charging. I do. That is, the charging control unit 170 inputs a constant current to the battery pack 140 from time t21 until the battery voltage of the battery pack 140 reaches the upper limit voltage. When the upper limit voltage is reached at time t22, the upper limit voltage is maintained. The current is input.

  In addition, the charging control unit 170 notifies the overcurrent protection unit 180 that external power supply has been detected. In response to the notification from the charge control unit 170, the threshold setting unit 181 updates the overcurrent threshold set in the comparator 182 from the overcurrent threshold 1 to the overcurrent threshold 2.

  When a resistance current in the negative direction flows in the state t21 and the battery pack 140 is charged, the monitor voltage becomes 0 or more and less than Vcc / 2 as shown in FIG. 8C.

  When the charging of the battery pack 140 is completed at time t23, the charging control unit 170 turns off the FET 120. When the FET 120 is turned off, there is no external power supply, so the charging control unit 170 notifies the overcurrent protection unit 180 that there is no external power supply. The threshold setting unit 181 receives the notification from the charging control unit 170 and updates the overcurrent threshold set in the comparator 182 from the overcurrent threshold 2 to the overcurrent threshold 1.

  Next, an operation when an overcurrent flows during constant current charging or constant voltage charging will be described.

  First, the case where constant current charging is performed will be described with reference to FIG.

  9A is a load current timing chart, FIG. 9B is a resistance current timing chart, and FIG. 9C is a monitor voltage and overcurrent threshold timing chart. 9 (d) is an on / off timing chart of the FETs 120 and 150. FIG. In FIG. 9C, the alternate long and short dash line indicates the overcurrent threshold set in the comparator 182.

  It is assumed that the charger 30 is not connected from time t0 to t31. In this case, the operation of each unit is the same as the operation from the time t0 to t21 described above, and a description thereof will be omitted.

  If the charger 30 is connected at time t31, the charging control unit 170 detects the external power supply, turns on the FET 120, and controls the current value of the current output from the FET 120. Here, the charging control unit 170 performs constant current charging by controlling the FET 120 to output a limiter current.

  In addition, the charging control unit 170 notifies the overcurrent protection unit 180 that external power supply has been detected. In response to the notification from the charge control unit 170, the threshold setting unit 181 updates the overcurrent threshold set in the comparator 182 from the overcurrent threshold 1 to the overcurrent threshold 2.

  As shown in FIG. 9B, the resistance current value is a value obtained by subtracting the current value of the load current from the limiter value. Here, when the current value of the load current exceeds the limiter value, a current is output from the battery pack 140 to the operating unit 300, and thus a resistance current in the positive direction flows.

  If the monitor voltage exceeds the overcurrent threshold 2 at time t32, the determination unit 183 determines that an overcurrent has flowed and turns off the FET 150. Moreover, the overcurrent protection unit 180 notifies the charge control unit 170 that an overcurrent is flowing. Upon receiving the notification from the overcurrent protection unit 180, the charging control unit 170 turns off the FET 120 and notifies the overcurrent protection unit 180 that there is no external power supply.

  By turning off the FETs 120 and 150, the load current and the resistance current become zero as shown in FIGS. 9 (a) and 9 (b).

  When the charge control unit 170 notifies that there is no external power supply, the threshold setting unit 181 updates the overcurrent threshold set in the comparator 182 from the overcurrent threshold 2 to the overcurrent threshold 1 at time t33.

  Next, the operation when constant voltage charging is performed will be described with reference to FIG.

  10A is a load current timing chart, FIG. 10B is a resistance current timing chart, and FIG. 10C is a monitor voltage and overcurrent threshold timing chart. 10 (d) is a timing chart showing ON / OFF of the FETs 120 and 150. FIG. In FIG. 10C, the alternate long and short dash line indicates an overcurrent threshold set in the comparator 182.

  It is assumed that the charger 30 is not connected between time t0 and time t41. In this case, the operation of each unit is the same as the operation from the time t0 to t21 described above, and a description thereof will be omitted.

  If the charger 30 is connected at time t41, the charging control unit 170 detects the external power supply, turns on the FET 120, and controls the current value of the current output from the FET 120. Here, the charging control unit 170 performs constant voltage charging by controlling the current value of the current (charging current) output from the FET 120 to be less than the limiter value.

  In this case, even if the load current increases, the resistance current becomes constant as shown in FIG. 10B if the sum of the current values of the load current and the charging current does not exceed the limiter value. When the load current increases and the sum of the load current and the charging current exceeds the limiter value, the charging current decreases. When the load current further increases and the current value of the load current exceeds the limiter value, power is supplied from the battery pack 140 to the operating unit 300, and thus a positive resistance current flows.

  Hereinafter, at time t42, the determination unit 183 detects that an overcurrent is flowing, and at time t43, the threshold setting unit 181 updates the overcurrent threshold of the comparator 182. Since the processes at times t42 and t43 are the same as the processes at times t32 and t33 described above, the description thereof is omitted.

  As described above, according to the present embodiment, the mobile device 10 performs charge control on the battery pack 140 and detection of overcurrent in accordance with the current value of the current flowing through the resistor 130. In order to prevent the occurrence, it is not necessary to provide two resistors and two current detectors, and the number of parts can be reduced.

  In the present embodiment, the configuration in which the mobile device 10 includes the power supply unit 100 has been described as an example, but the present invention is not limited to this. For example, as shown in FIG. 11, a power supply circuit 40 that prevents overcharge and generation of current may be provided between the portable device 10 having the battery pack 140 and the operation unit 300 and the charger 30. The configuration of the power supply circuit 40 is different only in that the battery pack 140 is deleted from the power supply unit 100 shown in FIG. 1, and the configuration and operation of each unit are the same, and thus the description thereof is omitted.

DESCRIPTION OF SYMBOLS 10 Portable apparatus 30 Charger 40 Power supply circuit 100 Power supply part 110 Diode 120,150 FET
DESCRIPTION OF SYMBOLS 130 Resistance 140 Battery pack 160 Current detection part 161 Amplifier 162 Offset voltage source 163 A / D converter 164 Averaging part 170 Charge control part 180 Overcurrent protection part 181 Threshold setting part 182 Comparator 183 Judgment part 300 Operation part

Claims (9)

A portable device including an operation unit that operates by being supplied with power, and a power supply unit that supplies power to the operation unit,
The power supply unit is
A secondary battery that charges the power supplied from an external charger and supplies the power to the operating unit;
One end is connected to the secondary battery and the other end is connected to the charger and the operating unit,
A current detector that detects a current value of a current flowing through the resistor and outputs current value data indicating the detected current value;
A charge control unit that controls a current value of a current input from the charger when power is supplied from the charger according to a current value indicated by the current value data;
It is determined whether or not the current value indicated by the current value data is equal to or greater than a predetermined threshold value. When the current value is equal to or greater than the threshold value, power supply from the secondary battery to the operation unit via the resistor is stopped. A portable device comprising: an overcurrent protection unit that causes The portable device according to claim 1, wherein
The charge control unit detects the presence or absence of power supply from the charger, and notifies the overcurrent protection unit,
The overcurrent protection unit lowers the threshold value when it is notified that there is power supply from the charger than when it is notified that there is no power supply. . The portable device according to claim 1, wherein the current detection unit outputs an average value of the current values detected within a predetermined period as the current value data. A power supply circuit of a portable device having an operation unit and a secondary battery that charges and supplies the supplied power to the operation unit,
One end is connected to the secondary battery, the other end is connected to a charger and the operating unit, a resistor,
A current detector that detects a current value of a current flowing through the resistor and outputs current value data indicating the detected current value;
A charge control unit that controls a current value of a current input from the charger when power is supplied from the charger according to a current value indicated by the current value data;
It is determined whether or not the current value indicated by the current value data is equal to or greater than a predetermined threshold value. When the current value is equal to or greater than the threshold value, power supply from the secondary battery to the operation unit via the resistor is stopped. And a power supply circuit comprising: an overcurrent protection unit that allows The power supply circuit according to claim 4, wherein
The charge control unit detects the presence or absence of power supply from the charger, and notifies the overcurrent protection unit,
The overcurrent protection unit lowers the threshold value when it is notified that power is supplied from the charger than when it is notified that there is no power supply. . 6. The power supply circuit according to claim 4, wherein the current detection unit outputs an average value of the current values detected within a predetermined period as the current value data. A charge control method applied to a portable device having an operation unit that operates by being supplied with power, and a secondary battery that supplies power supplied from an external charger to the operation unit,
The current detection unit detects a current value of a current flowing through a resistor having one end connected to the secondary battery and the other end connected to the charger and the operation unit,
The charge control unit controls the current value of the current input from the charger when power is supplied from the charger according to the current value indicated by the current value data,
The overcurrent protection unit determines whether or not the current value indicated by the current value data is equal to or greater than a predetermined threshold value, and if the current value is equal to or greater than the threshold value, the operation unit via the resistor from the secondary battery. The charge control method characterized by stopping the power supply to the battery. The charging control method according to claim 7,
The charge control unit detects the presence or absence of power supply from the charger, and notifies the overcurrent protection unit,
The overcurrent protection unit lowers the threshold value when it is notified that there is power supply from the charger than when it is notified that there is no power supply. Method. The charge control method according to claim 7 or 8, wherein the current detection unit outputs an average value of the current values detected within a predetermined period as the current value data.

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