JP5726579B2 - Secondary battery protection IC inspection method - Google Patents

Description

  The present invention provides an overcharge or overcharge of a secondary battery such as a lithium (Li) ion / lithium (Li) polymer secondary battery of a battery pack used in various electronic devices such as a mobile phone, a notebook computer, and a PDA (Personal Digital Assistance). The present invention relates to an inspection method for a secondary battery protection IC (Integrated Circuit) for protecting against discharge, charge overcurrent, and discharge overcurrent.

  Secondary battery protection IC is a technology for protecting secondary batteries in battery packs used in various electronic devices such as mobile phones, notebook computers and PDAs from overcharge, overdischarge, charge overcurrent, and discharge overcurrent. There is a battery pack including a mounted secondary battery protection module (see, for example, Patent Document 1).

FIG. 7 is a block diagram for explaining a battery pack including a secondary battery protection module on which a secondary battery protection IC is mounted. FIG. 8 is a schematic external view of a secondary battery protection IC.
The battery pack 1 includes a secondary battery 3 such as a lithium ion secondary battery or a lithium polymer secondary battery, and a secondary battery protection module 5. The secondary battery protection module 5 includes four terminals BATT +, BATT−, OUT +, and OUT−. Terminals BATT + and BATT− are connected to the secondary battery 3. The terminals OUT + and OUT− are connected to the charger 7 or a load such as a mobile phone, a notebook computer, or a PDA.

The secondary battery protection module 5 includes a secondary battery protection IC 9, a charge control FET (field effect transistor) Q1, a discharge control FET Q2, resistance elements R1 and R2, a capacitance element C1, and the like.
The secondary battery protection IC 9 constituting the main part of the secondary battery protection module 5 is roughly composed of an overcharge detection circuit 11, an overdischarge detection circuit 13, a discharge overcurrent detection circuit 15, a charge overcurrent detection circuit 17, and a short circuit. The delay circuit 25 includes a detection circuit 19, an oscillation circuit 21 and a counter 23, logic circuits 27 and 29, a level shift circuit 31, and a delay circuit 33. The secondary battery protection IC 9 includes a power supply voltage terminal VDD, a ground terminal VSS, an overcharge detection output terminal COUT, an overdischarge detection output terminal DOUT, and a charger minus potential input terminal V− as external connection terminals.

The basic operation of the secondary battery protection IC 9 will be described.
The overcharge detection circuit 11, overdischarge detection circuit 13, discharge overcurrent detection circuit 15, charge overcurrent detection circuit 17 or short circuit detection circuit 19 detects overcharge, overdischarge, discharge overcurrent, charge overcurrent or short circuit. Then, the oscillation circuit 21 starts operation, and the counter 23 starts counting.
When the counter 23 counts a preset delay time at each detection, the output of the overcharge detection output terminal COUT is low level through the logic circuit 27 and the level shift circuit 31 in the case of overcharge or charge overcurrent. The charge control FET Q1 is turned off, and in the case of overdischarge, discharge overcurrent, or short circuit, the output of the overdischarge detection output terminal DOUT goes low through the logic circuit 29, and the discharge control FET Q2 is turned off. .

  Thus, in general, in the secondary battery protection IC 9, a delay time is set for the operation when overcharge, overdischarge, discharge overcurrent, charge overcurrent, or short circuit is detected.

The secondary battery protection IC is tested for overcharge detection voltage, overdischarge detection voltage, charge overcurrent detection voltage, and discharge overcurrent detection voltage on a semiconductor wafer or in the state of a packaged semiconductor chip. It is.
When measuring each detection voltage, the measurement must be performed while waiting for the set delay time, and there is a problem that it takes a long time to test the secondary battery protection IC.

  FIG. 9 is a diagram for explaining a measurement time during a conventional overcharge detection voltage test. The vertical axis represents the voltage at the power supply voltage terminal VDD (VDD voltage) and the voltage at the overcharge detection output terminal COUT (COUT voltage), and the horizontal axis represents time.

  Referring also to FIG. 8, in the overcharge detection voltage test, the ground terminal VSS is connected to the ground potential, and a predetermined voltage is supplied to the charger minus potential input terminal V−. The voltage of the overdischarge detection output terminal DOUT is the same voltage as the power supply voltage terminal VDD. While monitoring the voltage of the overcharge detection output terminal COUT, the voltage of the power supply voltage terminal VDD is raised stepwise from a voltage (test start voltage) lower than the design value of the overcharge detection voltage. The time interval (time of one step) when the voltage of the power supply voltage terminal VDD is raised stepwise is the overcharge detection delay time tVDET1 set in the secondary battery protection IC. The voltage at the power supply voltage terminal VDD when the voltage at the overcharge detection output terminal COUT changes from the voltage at the power supply voltage terminal VDD to the voltage at the charger minus potential input terminal V− is the overcharge detection voltage.

  FIG. 10 is a diagram for explaining the measurement time during the conventional discharge overcurrent detection voltage test. The vertical axis represents the voltage at the charger minus potential input terminal V− (V−voltage) and the voltage at the overdischarge detection output terminal DOUT (DOUT voltage), and the horizontal axis represents time.

  Referring also to FIG. 8, in the discharge overcurrent detection voltage test, the ground terminal VSS is connected to the ground potential, and a predetermined voltage is supplied to the power supply voltage terminal VDD. The voltage of the overcharge detection output terminal COUT is the same voltage as the power supply voltage terminal VDD. While monitoring the voltage at the overdischarge detection output terminal DOUT, the voltage at the charger minus potential input terminal V− is increased stepwise from a voltage (test start voltage) lower than the design value of the discharge overcurrent detection voltage. The time interval (one step time) when the voltage of the charger minus potential input terminal V− is increased stepwise is the discharge overcurrent detection delay time tVDET3 set in the secondary battery protection IC. The voltage at the charger minus potential input terminal V− when the voltage at the overdischarge detection output terminal DOUT changes from the voltage at the power supply voltage terminal VDD to the voltage at the ground terminal VSS or oscillates is the discharge overcurrent detection voltage.

  FIG. 11 is a diagram for explaining a measurement time during a conventional charge overcurrent detection voltage test. The vertical axis represents the voltage at the charger negative potential input terminal V− (V−voltage) and the voltage at the overcharge detection output terminal COUT (COUT voltage), and the horizontal axis represents time.

  Referring also to FIG. 8, in the discharge overcurrent detection voltage test, the ground terminal VSS is connected to the ground potential, and a predetermined voltage is supplied to the power supply voltage terminal VDD. The voltage of the overdischarge detection output terminal DOUT is the same voltage as the power supply voltage terminal VDD. While monitoring the voltage of the overcharge detection output terminal COUT, the voltage of the charger minus potential input terminal V− is lowered stepwise from a voltage (test start voltage) higher than the design value of the charge overcurrent detection voltage. The time interval (one step time) when the voltage at the charger minus potential input terminal V− is lowered stepwise is the charge overcurrent detection delay time tVDET4 set in the secondary battery protection IC. The voltage at the charger minus potential input terminal V− when the voltage at the overcharge detection output terminal COUT changes from the voltage at the power supply voltage terminal VDD to the voltage at the ground terminal VSS or oscillates is the charge overcurrent detection voltage.

  In the case of the conventional overcharge detection voltage test, it is necessary to wait for at least the overcharge detection delay time tVDET1 every time the voltage of the power supply voltage terminal VDD is increased by one step. Similarly, in the case of the discharge overcurrent detection voltage test and the charge overcurrent detection voltage test, at least the discharge overcurrent detection delay time tVDET3 or the charge overcurrent detection delay time tVDET4 when changing the voltage of the charger minus potential input terminal V−. You just have to wait.

The measurement time of the overcharge detection voltage is determined by the overcharge detection delay time tVDET1 and the number of steps. For example, when the overcharge detection delay time tVDET1 is 50 milliseconds and the number of steps is 20, a time of “50 milliseconds × 20 times = 1000 milliseconds = 1 second” is required for measuring the overcharge detection voltage.
Similarly, the measurement time of the discharge overcurrent detection voltage and the measurement time of the charge overcurrent detection voltage are determined by the discharge overcurrent detection delay time tVDET3 or the charge overcurrent detection delay time tVDET4 and the number of steps. For example, when the discharge overcurrent detection delay time tVDET3 and the charge overcurrent detection delay time tVDET4 are 10 milliseconds and the number of steps is 20, the time of “10 milliseconds × 20 times = 200 milliseconds” is the discharge overcurrent detection voltage. Necessary for measurement and charge overcurrent detection voltage measurement.

In the prior art, there is also a secondary battery protection IC in which an internal circuit of the secondary battery protection IC includes a circuit called a test mode circuit capable of shortening the detection delay time in order to shorten the detection delay time.
However, there is a limit to shortening the detection delay time by the test mode circuit. Further, when the test mode circuit is used, there is a problem that the yield is lowered because there is a slight deviation from the true measurement value.

  An object of the present invention is to shorten the inspection time for overcharge detection voltage inspection, discharge overcurrent detection voltage inspection, and charge overcurrent detection voltage inspection of a secondary battery protection IC.

  One aspect of the inspection method of the secondary battery protection IC according to the present invention relates to the measurement of the overcharge detection voltage. Specifically, the first aspect of the present invention includes an overcharge detection circuit for detecting overcharge of the secondary battery, and a delay circuit for delaying the overcharge detection time by a predetermined delay time. A secondary battery protection IC inspection method for measuring an overcharge detection voltage for a secondary battery protection IC, and continuously monitoring a current value at a power supply voltage terminal of the secondary battery protection IC. Or stepwise at a time interval shorter than the delay time, the voltage of the power supply voltage terminal is increased from a voltage lower than the design value of the overcharge detection voltage, and based on the change in the current value of the power supply voltage terminal Measure the overcharge detection voltage.

  Another aspect of the inspection method of the secondary battery protection IC according to the present invention relates to the measurement of the discharge overcurrent detection voltage. Specifically, the second aspect of the present invention includes a discharge overcurrent detection circuit for detecting a discharge overcurrent of a secondary battery, and a delay circuit for delaying a discharge overcurrent detection time by a predetermined delay time. A secondary battery protection IC inspection method for measuring a discharge overcurrent detection voltage for a secondary battery protection IC comprising: monitoring a current value at a power supply voltage terminal of the secondary battery protection IC However, the voltage of the charger minus potential input terminal of the secondary battery protection IC is increased from a voltage higher than the design value of the discharge overcurrent detection voltage continuously or stepwise at a time interval shorter than the delay time. The discharge overcurrent detection voltage is measured based on the change in the current value of the power supply voltage terminal.

  Still another aspect of the inspection method for the secondary battery protection IC according to the present invention relates to the measurement of the charge overcurrent detection voltage. Specifically, the second aspect of the present invention includes a charge overcurrent detection circuit for detecting a charge overcurrent of a secondary battery, and a delay circuit for delaying a detection time of the charge overcurrent by a predetermined delay time. A secondary battery protection IC inspection method for measuring a charge overcurrent detection voltage for a secondary battery protection IC comprising: a current value at a power supply voltage terminal of the secondary battery protection IC However, the voltage of the charger minus potential input terminal of the secondary battery protection IC is changed from a voltage lower than the design value of the charge overcurrent detection voltage continuously or stepwise at a time interval shorter than the delay time. The charge overcurrent detection voltage is measured based on the change in the current value of the power supply voltage terminal.

  The inventor of the present application has found that when the overcharge detection function, the discharge overcurrent detection function, and the discharge overcharge detection function work in the secondary battery protection IC, the power supply voltage terminal changes in a direction in which a large amount of current flows. When the secondary battery protection IC detects overcharge, discharge overcurrent, or discharge overcurrent, the delay time is set as described above until the detection signal is output. There is no delay time in the current value change of the power supply voltage terminal when the discharge overcurrent detection function and the discharge overcurrent detection function are activated. Therefore, the present invention monitors the current value change of the power supply voltage terminal without changing the voltage of the power supply voltage terminal or the voltage of the charger minus potential input terminal with a time interval equal to or longer than the delay time for each detection voltage, Measure the overcharge detection voltage, discharge overcurrent detection voltage or charge overcurrent detection voltage by changing the voltage of the power supply voltage terminal or the charger minus potential input terminal continuously or stepwise at time intervals less than the delay time it can.

  In each aspect of the present invention, when the voltage of the power supply voltage terminal or the voltage of the charger minus potential input terminal is increased or decreased step by step at a time interval shorter than the delay time, the voltage is increased or decreased by a predetermined amount. The power supply voltage terminal using the current value in the previous voltage rise step or voltage drop step as a reference value for detecting a change in the current value of the power supply voltage terminal as a voltage rise step or a voltage drop step. An example in which the current value one step before is used as a reference value for detecting a change in the current value. However, the reference value for detecting the change in the current value of the power supply voltage terminal is not limited to this, and may be, for example, the current value of the power supply voltage terminal at the start of measurement, or set in advance. It may be a predetermined current value.

  The change in the current value of the power supply voltage terminal is, for example, by setting a threshold value for the rate of change or difference of the current value with respect to the reference value, or by setting a detection threshold value for the current value in advance. Can be detected. Note that the detection method of the change in the current value of the power supply voltage terminal caused by the overcharge detection function, the discharge overcurrent detection function, and the discharge overcurrent detection function is not limited to these.

The method for inspecting a secondary battery protection IC according to the present invention allows the voltage of the power supply voltage terminal or the voltage of the charger minus potential input terminal to be changed without changing the voltage of the power supply voltage terminal with a time interval greater than the delay time for each detection voltage. While monitoring the current value change, overcharge detection voltage, discharge overcurrent detection voltage by changing the voltage of the power supply voltage terminal or the charger minus potential input terminal continuously or stepwise at time intervals less than the delay time. Alternatively, since the charge overcurrent detection voltage can be measured, the inspection time can be shortened for the overcharge detection voltage inspection, the discharge overcurrent detection voltage inspection, and the charge overcurrent detection voltage inspection of the secondary battery protection IC.
Since the change in the current value of the power supply voltage terminal can be monitored by using an ammeter, the present invention can be realized by an inexpensive and low-functional semiconductor inspection apparatus without using a special measurement function.
Furthermore, since it is not necessary to use a test mode circuit, the present invention can prevent the circuit configuration of the secondary battery protection IC from being complicated and the yield from being lowered.

  In each aspect of the present invention, when the voltage of the power supply voltage terminal or the voltage of the charger minus potential input terminal is increased or decreased step by step at a time interval shorter than the delay time, the step of increasing or decreasing the voltage by a predetermined amount May be used as a voltage rise step or a voltage drop step, and the current value in the previous voltage rise step or voltage drop step may be used as a reference value for detecting a change in the current value of the power supply voltage terminal. The current value gradually decreases while the voltage is gradually changed. When comparing the current value at the start of the test with the current value at the time of detection, the current value at the start of the test and the current value at the time of detection are measured. Although it may be assumed that the values will be the same, this situation can avoid such erroneous measurement, so that more accurate measurement is possible.

It is a flowchart for demonstrating one Example for measuring an overcharge detection voltage. It is a figure for demonstrating the measurement time at the time of the overcharge detection voltage test | inspection in the Example. It is a flowchart for demonstrating one Example for measuring a discharge overcurrent detection voltage. It is a figure for demonstrating the measurement time at the time of the discharge overcurrent detection voltage test | inspection in the Example. It is a flowchart for demonstrating one Example for measuring a charge overcurrent detection voltage. It is a figure for demonstrating the measurement time at the time of the charge overcurrent detection voltage test | inspection in the Example. It is a block diagram for demonstrating the battery pack provided with the secondary battery protection module by which IC for secondary battery protection is mounted. It is a schematic external view of IC for secondary battery protection. It is a figure for demonstrating the measurement time at the time of the conventional overcharge detection voltage test | inspection. It is a figure for demonstrating the measurement time at the time of the conventional discharge overcurrent detection voltage test | inspection. It is a figure for demonstrating the measurement time at the time of the conventional charge overcurrent detection voltage test | inspection.

  FIG. 1 is a flowchart for explaining an embodiment for measuring an overcharge detection voltage. FIG. 2 is a diagram for explaining the measurement time during the overcharge detection voltage inspection in this embodiment. In FIG. 2, the vertical axis indicates the voltage (VDD voltage) and current (VDD current) of the power supply voltage terminal VDD, and the horizontal axis indicates time. This embodiment will be described with reference to FIGS.

Step S1: Supply a voltage (test start voltage) lower than the design value of the overcharge detection voltage to the power supply voltage terminal VDD. The ground terminal VSS of the secondary battery protection IC 9 is connected to the ground potential. A predetermined voltage is supplied to the charger minus potential input terminal V−. The voltages of the overcharge detection output terminal COUT and the overdischarge detection output terminal DOUT are the same voltage as the power supply voltage terminal VDD. Changes in the current value of the power supply voltage terminal VDD are monitored.
For example, the design value of the overcharge detection voltage is 4.2V, the test start voltage supplied to the power supply voltage terminal VDD is 4.193V, and the voltage supplied to the charger minus potential input terminal V− is −3V. The current value of the power supply voltage terminal VDD (current at the start of the test) is about 4.0 μA (microamperes).

  Step S2: It is determined whether or not a predetermined current value change has occurred in the current value of the power supply voltage terminal VDD with respect to the current value at the start of the test. For example, the predetermined current value change is set when the current value at the start of the test (about 4.0 μA) increases by 0.3 μA or more. In the state where the test start voltage is supplied to the power supply voltage terminal VDD, the current value of the power supply voltage terminal VDD does not change (No), so the process proceeds to Step 3. The current value at the start of the test and the reference value for detecting a predetermined current value change are examples, and these values are the type of secondary battery protection IC to be inspected, parameters in the manufacturing process, etc. It goes without saying that it varies depending on the situation.

  Step S3: Increase the voltage of the power supply voltage terminal VDD by a predetermined amount (voltage increase step). For example, the voltage of the power supply voltage terminal VDD is increased by 1.0 mV (millivolt). At this time, the current value of the power supply voltage terminal VDD decreases by about 10 nA (nanoampere). Returning to step S2, it is determined whether or not a predetermined current value change has occurred in the current value of the power supply voltage terminal VDD with respect to the current value at the start of the test. A delay circuit composed of an overcharge detection function (for example, the overcharge detection circuit 11, the oscillation circuit 21 and the counter 23 in FIG. 7) when the voltage of the power supply voltage terminal VDD of the secondary battery protection IC 9 exceeds the overcharge detection voltage. When 25) operates, the current value of the power supply voltage terminal VDD rises to, for example, about 4.4 μA. Steps S3 and S2 are repeated until a predetermined current value change occurs at the power supply voltage terminal VDD in step S2. The time interval for increasing the voltage of the power supply voltage terminal VDD is, for example, 1 millisecond or less, here 500 microseconds (μS). However, this time interval is not limited to these times. This time interval may be shorter than the overcharge detection delay time set in the secondary battery protection IC 9 and may be several hundred microseconds, for example. Further, the voltage of the power supply voltage terminal VDD may be continuously increased. When the secondary battery protection IC 9 detects overcharge, an overcharge detection delay time is required until the detection signal is output to the overcharge detection output terminal COUT, but the power supply when the overcharge detection function is activated Since there is no delay time for the current value change of the voltage terminal VDD, the time interval for increasing the voltage of the power supply voltage terminal VDD can be made shorter than the overcharge detection delay time.

  Step S4: When a predetermined current value change is detected at the power supply voltage terminal VDD in Step S2 (Yes), the voltage supplied to the power supply voltage terminal VDD is set as the overcharge detection voltage. Thus, in this embodiment, while monitoring the change in the current value of the power supply voltage terminal VDD, the voltage of the power supply voltage terminal VDD is increased stepwise at a time interval (500 microsecond intervals) less than the overcharge detection delay time. Thus, the overcharge detection voltage can be measured.

  For example, when the time interval for raising the voltage of the power supply voltage terminal VDD is 500 microseconds and the number of steps is 20, the time required for the overcharge detection voltage measurement is “500 microseconds × 20 times = 10000 microseconds = 10 milliseconds. Seconds ". In the prior art, when measuring the overcharge detection voltage, the time interval for increasing the voltage of the power supply voltage terminal VDD requires a time longer than the overcharge detection delay time (for example, 50 milliseconds), and when the number of steps is 20, At least “50 milliseconds × 20 times = 1000 milliseconds = 1 second” was required. Therefore, this embodiment can shorten the overcharge detection voltage measurement time to about 1/100 compared with the prior art. The overcharge detection voltage measurement includes time information and time information reading time in the program statement, so the measurement time does not actually become 1/100. Per measurement, the time required for 1 second in the prior art can be reduced to 10 milliseconds, that is, the measurement time can be reduced to 990 milliseconds.

  FIG. 3 is a flowchart for explaining an embodiment for measuring the discharge overcurrent detection voltage. FIG. 4 is a diagram for explaining the measurement time at the time of the discharge overcurrent detection voltage inspection in this embodiment. In FIG. 4, the vertical axis represents the voltage at the charger minus potential input terminal V− (V−voltage) and the current at the power supply voltage terminal VDD (VDD current), and the horizontal axis represents time. This embodiment will be described with reference to FIGS.

Step S11: Supply a voltage (test start voltage) lower than the design value of the discharge overcurrent detection voltage to the charger minus potential input terminal V−. The ground terminal VSS of the secondary battery protection IC 9 is connected to the ground potential. A predetermined voltage is supplied to the power supply voltage terminal VDD. The voltages of the overcharge detection output terminal COUT and the overdischarge detection output terminal DOUT are the same voltage as the power supply voltage terminal VDD. Changes in the current value of the power supply voltage terminal VDD are monitored.
For example, the design value of the discharge overcurrent detection voltage is 0.2 V, the test start voltage supplied to the charger minus potential input terminal V− is 0.193 V, and the voltage supplied to the power supply voltage terminal is 3 V. The current value of the power supply voltage terminal VDD (current at the start of the test) is about 4.0 μA.

  Step S12: It is determined whether or not a predetermined current value change has occurred in the current value at the power supply voltage terminal VDD with respect to the current value at the start of the test. For example, the predetermined current value change is set when the current value at the start of the test (about 4.0 μA) increases by 0.3 μA or more. In the state where the voltage at the start of the test is supplied to the charger minus potential input terminal V−, the current value of the power supply voltage terminal VDD has not changed (No). The current value at the start of the test and the reference value for detecting a predetermined current value change are examples, and these values are the type of secondary battery protection IC to be inspected, parameters in the manufacturing process, etc. It goes without saying that it varies depending on the situation.

  Step S13: The voltage at the charger minus potential input terminal V- is increased by a predetermined amount (voltage increase step). For example, the voltage of the power supply voltage terminal VDD is increased by 1.0 mV. Returning to step S12, it is determined whether or not a predetermined current value change has occurred in the current value of the power supply voltage terminal VDD with respect to the current value at the start of the test. The voltage of the charger minus potential input terminal V− of the secondary battery protection IC 9 becomes equal to or higher than the discharge overcurrent detection voltage, so that a discharge overcurrent detection function (for example, the discharge overcurrent detection circuit 15 of FIG. When the delay circuit 25) composed of 23 operates, the current value of the power supply voltage terminal VDD rises to about 4.4 μA, for example. Steps S13 and S12 are repeated until a predetermined current value change occurs at the power supply voltage terminal VDD in step S12. The time interval for increasing the voltage at the charger minus potential input terminal V− is, for example, 1 millisecond or less, and here, 500 microseconds (μS). However, this time interval is not limited to these times. This time interval may be shorter than the discharge overcurrent detection delay time set in the secondary battery protection IC 9 and may be several hundred microseconds, for example. Further, the voltage of the charger minus potential input terminal V− may be continuously increased. When the secondary battery protection IC 9 detects a discharge overcurrent, it takes a discharge overcurrent detection delay time until the detection signal is output to the overdischarge detection output terminal DOUT, but the discharge overcurrent detection function has worked. Since there is no delay time in changing the current value of the power supply voltage terminal VDD at this time, the time interval for increasing the voltage at the charger minus potential input terminal V− can be made shorter than the discharge overcurrent detection delay time.

  Step S14: When a predetermined current value change is detected at the power supply voltage terminal VDD in Step S12 (Yes), the voltage supplied to the charger minus potential input terminal V− is set as the discharge overcurrent detection voltage. As described above, in this embodiment, while monitoring the change in the current value of the power supply voltage terminal VDD, the charger minus potential input terminal V− is stepwise at time intervals (500 microsecond intervals) less than the discharge overcurrent detection delay time. The discharge overcurrent detection voltage can be measured by increasing the voltage.

  For example, when the time interval for increasing the voltage of the charger minus potential input terminal V− is 500 microseconds and the number of steps is 20, the time required for the discharge overcurrent detection voltage measurement is “500 microseconds × 20 times = 10000”. Microseconds = 10 milliseconds ”. In the prior art, when measuring the discharge overcurrent detection voltage, the time interval for increasing the voltage at the charger minus potential input terminal V- requires a time longer than the discharge overcurrent detection delay time (for example, 10 milliseconds), and the number of steps Is 20 times, at least “10 milliseconds × 20 times = 200 milliseconds” is required. Therefore, in this embodiment, it is possible to reduce the time which has been 200 milliseconds in the prior art to 10 milliseconds per measurement, that is, to shorten the measurement time by 190 milliseconds.

  FIG. 5 is a flowchart for explaining an embodiment for measuring the charge overcurrent detection voltage. FIG. 6 is a diagram for explaining the measurement time at the time of the charge overcurrent detection voltage inspection in this embodiment. In FIG. 6, the vertical axis represents the voltage at the charger minus potential input terminal V− (V−voltage) and the current at the power supply voltage terminal VDD (VDD current), and the horizontal axis represents time. This embodiment will be described with reference to FIGS.

Step S21: Supply a voltage (test start voltage) higher than the design value of the charge overcurrent detection voltage to the charger minus potential input terminal V−. The ground terminal VSS of the secondary battery protection IC 9 is connected to the ground potential. A predetermined voltage is supplied to the power supply voltage terminal VDD. The voltages of the overcharge detection output terminal COUT and the overdischarge detection output terminal DOUT are the same voltage as the power supply voltage terminal VDD. Changes in the current value of the power supply voltage terminal VDD are monitored.
For example, the design value of the charge overcurrent detection voltage is -0.2V, the test start voltage supplied to the charger minus potential input terminal V- is -0.193V, and the voltage supplied to the power supply voltage terminal is 3V. The current value of the power supply voltage terminal VDD (current at the start of the test) is about 4.0 μA.

  Step S22: It is determined whether or not a predetermined current value change has occurred in the current value at the power supply voltage terminal VDD with respect to the current value at the start of the test. For example, the predetermined current value change is set when the current value at the start of the test (about 4.0 μA) increases by 0.3 μA or more. In the state where the voltage at the start of the test is supplied to the charger minus potential input terminal V−, the current value of the power supply voltage terminal VDD has not changed (No). The current value at the start of the test and the reference value for detecting a predetermined current value change are examples, and these values are the type of secondary battery protection IC to be inspected, parameters in the manufacturing process, etc. It goes without saying that it varies depending on the situation.

  Step S23: The voltage of the charger minus potential input terminal V- is lowered by a predetermined amount (voltage drop step). For example, the voltage of the power supply voltage terminal VDD is lowered by 1.0 mV. Returning to step S22, it is determined whether or not a predetermined current value change has occurred in the current value of the power supply voltage terminal VDD with respect to the current value at the start of the test. The voltage of the charger minus potential input terminal V− of the secondary battery protection IC 9 becomes equal to or lower than the charge overcurrent detection voltage, so that a charge overcurrent detection function (for example, the charge overcurrent detection circuit 17 of FIG. When the delay circuit 25) composed of 23 operates, the current value of the power supply voltage terminal VDD rises to about 4.4 μA, for example. Steps S23 and S22 are repeated until a predetermined current value change occurs at the power supply voltage terminal VDD in step S22. The time interval for dropping the voltage at the charger minus potential input terminal V− is, for example, 1 millisecond or less, and here, 500 microseconds (μS). However, this time interval is not limited to these times. This time interval may be shorter than the charge overcurrent detection delay time set in the secondary battery protection IC 9, and may be several hundred microseconds, for example. Further, the voltage at the charger minus potential input terminal V− may be continuously applied. When the secondary battery protection IC 9 detects a charge overcurrent, it takes a charge overcurrent detection delay time until the detection signal is output to the overcharge detection output terminal COUT, but the charge overcurrent detection function has worked. Since there is no delay time for the current value change of the power supply voltage terminal VDD at this time, the time interval for dropping the voltage of the charger minus potential input terminal V− can be made shorter than the charge overcurrent detection delay time.

  Step S24: The voltage supplied to the charger minus potential input terminal V− when the predetermined current value change is detected at the power supply voltage terminal VDD in step S22 is set as the charge overcurrent detection voltage. As described above, in this embodiment, while monitoring the change in the current value of the power supply voltage terminal VDD, the charger minus potential input terminal V− is stepwise at time intervals (500 microsecond intervals) less than the charge overcurrent detection delay time. The charging overcurrent detection voltage can be measured by lowering the voltage.

  For example, when the time interval for dropping the voltage of the charger minus potential input terminal V− is 500 microseconds and the number of steps is 20, the time required for the charge overcurrent detection voltage measurement is “500 microseconds × 20 times = 10000”. Microseconds = 10 milliseconds ”. In the prior art, when measuring the charge overcurrent detection voltage, the time interval for dropping the voltage of the charger minus potential input terminal V- requires a time longer than the charge overcurrent detection delay time (for example, 10 milliseconds), and the number of steps Is 20 times, at least “10 milliseconds × 20 times = 200 milliseconds” is required. Therefore, in this embodiment, it is possible to reduce the time which has been 200 milliseconds in the prior art to 10 milliseconds per measurement, that is, to shorten the measurement time by 190 milliseconds.

Although the embodiments of the present invention have been described above, the voltage values, current values, time settings, circuit configurations, etc. in the above embodiments are merely examples, and the present invention is not limited to these, and is within the scope of the claims. Various modifications are possible within the scope of the described invention.
For example, in the above embodiment, the current value at the power supply voltage terminal at the start of measurement is used as the reference value for detecting the change in the current value at the power supply voltage terminal. However, the reference value is not limited to this. For example, the reference value may be a current value in the previous voltage rise step or voltage drop step, or may be a predetermined current value set in advance.

  Moreover, although the said Example detects the current value change of a power supply voltage terminal by setting a threshold value to the difference with respect to the reference value of a current value, the detection method of the current value change of a power supply voltage terminal is It is not limited to this. For example, the change in the current value of the power supply voltage terminal may be detected by obtaining a rate of change of the current value with respect to the reference value, or by setting a detection threshold value for the current value in advance.

  Moreover, although the said Example uses secondary battery protection IC9 demonstrated with reference to FIG.7 and FIG.8, secondary battery protection IC to which this invention is applied is not limited to this. The present invention can be applied to a secondary battery protection IC including an overcharge detection circuit, a discharge overcurrent detection circuit, a charge overcurrent detection circuit, and a delay circuit for setting the detection delay time thereof. The circuit configuration of the overcharge detection circuit, the discharge overcurrent detection circuit, the charge overcurrent detection circuit, and the delay circuit that sets the detection delay time thereof is not limited.

  The present invention relates to a secondary battery protection IC for protecting a secondary battery in a battery pack used in various electronic devices such as a mobile phone, a notebook computer, and a PDA from overcharge, overdischarge, charge overcurrent, and discharge overcurrent. It is applied to inspection.

3 Secondary battery 9 Secondary battery protection IC
11 Overcharge detection circuit 15 Discharge overcurrent detection circuit 17 Charge overcurrent detection circuit 25 Delay circuit VDD Power supply voltage terminal V− Charger minus potential input terminal

JP 2002-176730 A

Claims (3)

An overcharge detection voltage is provided for a secondary battery protection IC having an overcharge detection circuit for detecting overcharge of the secondary battery and a delay circuit for delaying the overcharge detection time by a predetermined delay time. In the inspection method of the secondary battery protection IC for measurement,
While monitoring the current value of the power supply voltage terminal of the rechargeable battery protection IC, stepwise at a time interval shorter than the previous SL delay time, less than the design value of the voltage of the power supply voltage terminal overcharge detection voltage When measuring the overcharge detection voltage based on the change in the current value of the power supply voltage terminal, rising from the voltage ,
A step of increasing the voltage by a predetermined amount when increasing the voltage of the power supply voltage terminal stepwise at a time interval shorter than the delay time is defined as a voltage increase step, and a change in the current value of the power supply voltage terminal is detected. A method for inspecting a secondary battery protection IC, wherein the current value in the previous voltage rise step is used as a reference value for the purpose . A secondary battery protection IC having a discharge overcurrent detection circuit for detecting a discharge overcurrent of a secondary battery and a delay circuit for delaying a discharge overcurrent detection time by a predetermined delay time In the inspection method of the secondary battery protection IC for measuring the current detection voltage,
While monitoring the current value of the power supply voltage terminal of the rechargeable battery protection IC, stepwise at a time interval shorter than the previous SL delay time, a voltage of the charger negative potential input terminal of the rechargeable battery protection IC When measuring the discharge overcurrent detection voltage based on the change in the current value of the power supply voltage terminal by dropping from a voltage higher than the design value of the discharge overcurrent detection voltage ,
The step of dropping the voltage by a predetermined amount when dropping the voltage of the charger minus potential input terminal stepwise at a time interval shorter than the delay time is defined as a voltage drop step, and the change in the current value of the power supply voltage terminal A method for inspecting a secondary battery protection IC, wherein a current value at a voltage drop step one time before is used as a reference value for detecting battery. A secondary battery protection IC comprising a charge overcurrent detection circuit for detecting a charge overcurrent of a secondary battery and a delay circuit for delaying a charge overcurrent detection time by a predetermined delay time In the inspection method of the secondary battery protection IC for measuring the current detection voltage,
While monitoring the current value of the power supply voltage terminal of the rechargeable battery protection IC, stepwise at a time interval shorter than the previous SL delay time, a voltage of the charger negative potential input terminal of the rechargeable battery protection IC When the charge overcurrent detection voltage is raised from a voltage lower than the design value of the charge overcurrent detection voltage and the charge overcurrent detection voltage is measured based on the change in the current value of the power supply voltage terminal ,
A step of increasing the voltage by a predetermined amount when the voltage of the charger minus potential input terminal is increased stepwise in a time interval shorter than the delay time is defined as a voltage increase step, and a change in the current value of the power supply voltage terminal A method for inspecting a secondary battery protection IC, wherein a current value in a voltage increase step one time before is used as a reference value for detecting a battery voltage .

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