Input protection circuit and secondary battery deterioration determination device using the same

Abstract

To provide an input protection circuit and a deterioration determination device for a secondary battery using the same capable of preventing measurement errors of an operational amplifier independent of a voltage state of an input signal.SOLUTION: A first or second bipolar transistor, and one or more first or second diodes connected with the first or second bipolar transistor so as to have a polarity reverse to a base-emitter conduction direction of the first or second bipolar transistor and connected in series with each other so as to have the polarity, are provided between an input terminal and a positive or negative power supply or the ground. For a power supply voltage of the positive or negative power supply or the ground, an increased or decreased amount of a base-emitter voltage of the first or second bipolar transistor is provided with a decreased or increased amount of a forward voltage depending on the number of the first or second diodes to adjust an input voltage so as not to exceed the power supply voltage.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an input protection circuit for an input section of a device that measures voltages such as various sensors, and to an external device that is connected to the input section with a wide or indefinite voltage range, and to a secondary battery deterioration determination device using the same. [Background technology]

[0002] Conventionally, input protection circuits consisting of a protective diode and a resistive element have been known, and the resistive element is used to limit the input current when an overvoltage is input. Even when an overvoltage is input, the PN junction diode limits the voltage to the power supply voltage plus the forward voltage of the diode (for example, Non-Patent Document 1).

[0003] Furthermore, in a conventional input protection circuit, an integrator circuit is equivalently configured based on a combination of the capacitances of a resistor element and a diode element, and in order to solve the problem that high-speed operation cannot be achieved due to transient phenomena occurring in the input protection circuit, it is known to place a capacitive element between the integrator circuit and the internal circuit (for example, Patent Document 1).

[0004] Furthermore, it is known that a protection circuit can be easily formed without adding unnecessary steps to the high frequency semiconductor manufacturing process by using not only a combination of PN junction diodes but also Schottky barrier diodes as a configuration that effectively removes external static electricity while maintaining the performance of the high frequency semiconductor device (for example, Patent Document 2).

[0005] When a PN junction diode or Schottky barrier diode is used in an input protection circuit, the input signal to the circuit is clamped to a voltage obtained by adding the forward voltage of the diode to the power supply voltage for positive overvoltages, and similarly to a voltage obtained by subtracting the forward voltage of the diode from the power supply voltage on the lower voltage side for negative overvoltages. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 8-32025 [Patent Document 2] Japanese Patent Application Laid-Open No. 2001-110993 [Non-patent literature]

[0007] [Non-Patent Document 1] Analog Dialogue OCT2015VOL49 "Voltage Clamps with ESD Diodes" (http: / / www.analog.com / jp / analog-dialogue / articles / esd-diodes-as-voltage-clamps.html) Summary of the Invention [Problem to be solved by the invention]

[0008] However, in sensor circuits and other devices that require highly accurate detection, analog input is input to an operational amplifier (op-amp) consisting of a transistor differential amplifier circuit, where it is amplified and subjected to differential calculations. In a protection circuit using a PN junction diode, the forward voltage VF of the PN junction diode is large, at 0.6 to 0.7 V, and if the DC or low-frequency components of the input signal exceed the common-mode input voltage range of the operational amplifier, the operational amplifier may malfunction.

[0009] A conventional protection circuit is shown in Fig. 10. If the upper limit voltage of the input signal is Vlimit+, the lower limit voltage is Vlimit-, the positive power supply voltage is Vcc, the negative power supply voltage or ground voltage is Vee, and the forward voltage of the first and second diodes is VF, the upper and lower voltage limits are obtained by increasing or decreasing (offsetting) the power supply voltage by the amount of the forward voltage VF of the first and second PN junction diodes 4, 4 (Equations 1 and 2). Vlimit+=Vcc+VF Equation 1 Vlimit-=Vee-VF Equation 2

[0010] By using a Schottky barrier diode instead of a PN junction diode, the forward voltage VF can be suppressed to approximately 0.2 V, but the input voltage still exceeds the common-mode input voltage range of the operational amplifier, and there is the possibility of operational amplifier malfunction, just as with protection circuits using PN junction diodes. Also, because Schottky barrier diodes have a larger leakage current than PN junction diodes, there is the issue that even if the input signal is within the normal range, the leakage current can reduce the accuracy of the operation.

[0011] A conventional protection circuit using Schottky barrier diodes is shown in Figure 3. Figure 11 shows a configuration in which the PN junction diodes 4, 4 shown in equations 1 and 2 in the conventional protection circuit (Figure 10) have been replaced with Schottky barrier diodes 5, 5 in order to reduce the effect of the forward voltage of these diodes. Schottky barrier diodes are characterized by their small forward voltage VF of approximately 0.2V.

[0012] On the other hand, it has the diode characteristics shown in Figure 12 and has a larger leakage current (IR) than a PN junction diode. The effect of this leakage current causes a voltage drop in the stage before the operational amplifier input, resulting in measurement errors. When precise measurements are required, a protection circuit using a Schottky barrier diode is not suitable.

[0013] In view of the problems with the conventional technology described above, the present invention aims to provide an input protection circuit that prevents measurement errors in an operational amplifier regardless of the voltage state of the input signal, and a secondary battery deterioration determination device using the same. [Means for solving the problem]

[0014] The input protection circuit of the present invention comprises a first bipolar transistor connected between an input terminal and a negative power supply or ground, and one or more first diodes connected in series with a polarity opposite to the conduction direction between the first bipolar transistor and its base-emitter, a second bipolar transistor and a second diode connected in series with a polarity opposite to the conduction direction between the second bipolar transistor and its base-emitter, the second diode being one or more diodes connected in series with the polarity opposite to the conduction direction between the second bipolar transistor and its base-emitter, This prevents operational amplifiers from malfunctioning due to input voltage. The input voltage is adjusted so that it does not exceed the power supply voltage by adding a decrease or increase in the forward voltage of the first or second diode to the increase or decrease in the base-emitter voltage of the first or second bipolar transistor relative to the power supply voltage of the positive power supply, negative power supply, or ground, depending on the number of the first or second diodes.

[0015] According to this configuration, the operational amplifier includes a first or second bipolar transistor and one or more first or second diodes connected in series with the first or second bipolar transistor and connected with a polarity opposite to the base-emitter conduction direction of the first or second bipolar transistor, so that an increase or decrease in the forward voltage corresponding to the number of third or fourth diodes is added to an increase or decrease in the base-emitter voltage of the first or second bipolar transistor relative to the power supply voltage, thereby adjusting the input voltage so that it does not exceed the power supply voltage. As a result, even if high-frequency components such as noise or AC components of the input signal exceed the common-mode input voltage range of the operational amplifier, they are limited so as not to exceed the power supply voltage and are kept within the common-mode input voltage range, thereby reliably preventing malfunction of the operational amplifier regardless of the voltage state of the input signal.

[0016] For example, if there is one PN junction diode in a series-connected diode group, the AC component of the input signal is limited to a voltage roughly equivalent to the power supply voltage, and if there are two diodes in a series-connected diode group, the input signal is clamped to a voltage approximately 0.7V lower than the power supply voltage. The limiting voltage of the input signal can be controlled by the number of PN junction diodes connected in series.

[0017] In other words, in the case of a rail-to-rail operational amplifier with a wide input common-mode input voltage range of power supply voltage +0.2 to 0.3 V, one or two PN junction diodes in the diode group can be used, and in the case of a general operational amplifier where the common-mode input voltage range is 1 to 2 V narrower than the upper and lower limits of the power supply voltage, two or more PN junction diodes in the diode group can be used to suppress the voltage of the input signal within the common-mode input voltage range of the operational amplifier.

[0018] In this invention, bipolar transistors 3a and 3b are used as emitter followers, and the emitter voltage, which is the output voltage of the protection circuit, is controlled based on the base voltage. When the input signal to the protection circuit exceeds the upper or lower voltage limit, base and collector currents flow, causing the protection circuit to function. However, because the base current is much smaller than the collector current, the forward current I of the PN junction diode group 4a is determined by the second resistor element 1b, and the forward current I of the PN junction diode group 4b is determined by the third resistor element 1c. Therefore, regardless of the voltage magnitude or DC or AC component of the input signal, the voltage is always limited to the set upper and lower voltage limits.

[0019] Preferably, the first resistor element having one end connected to the input terminal and the other end connected to the emitters of the first and second bipolar transistors and the input stage of the operational amplifier; one or more first diodes connected in series, each having an anode connected to the positive power supply and a cathode connected to the base of the first bipolar transistor and one end of the second resistor element; the first bipolar transistor having a collector connected to a negative power supply or ground, a base connected to the cathode of the first diode and one side of the second resistor element, and an emitter connected to the input stage of the operational amplifier and the other side of the first resistor element; the second resistive element having one end connected to the cathode of the first diode and the base of the first bipolar transistor and the other end connected to the negative power supply or ground; one or more second diodes connected in series, each having an anode connected to the base of the second bipolar transistor and one of the third resistor elements and a cathode connected to the negative power supply or ground; the second bipolar transistor having a collector connected to the positive power supply, a base connected to the anode of the second diode group and one end of the third resistor element, and an emitter connected to the input stage of the operational amplifier and the other end of the first resistor element; One end is connected to the anode of the second diode group and the base of the second bipolar transistor, and the other end is connected to the third resistance element connected to the positive power supply. In this case, the input voltage is adjusted so as not to exceed the power supply voltage depending on the configuration of each element, so that malfunction of the operational amplifier can be prevented more reliably.

[0020] Preferably, the first resistor element has one end connected to the input terminal and the other end connected to the emitters of the first and second bipolar transistors and the input stage of the operational amplifier; one or more first diodes connected in series, each having an anode connected to the positive power supply and a cathode connected to the base of the first bipolar transistor and one end of the second resistor element; the first bipolar transistor having a collector connected to the negative power supply or ground, a base connected to the cathode of the first diode and one side of the second resistor element, and an emitter connected to the input stage of the operational amplifier and the other side of the first resistor element; one or more second diodes connected in series, each having an anode connected to the base of the second bipolar transistor and the other end of the second resistor element and a cathode connected to the negative power supply or ground; a second bipolar transistor having a collector connected to the positive power supply, a base connected to the anode of the second diode and the other end of the second resistor element, and an emitter connected to the input stage of the operational amplifier and the other end of the first resistor element; The second resistor element has one end connected to the cathode of the first diode and the base of the first bipolar transistor, and the other end connected to the anode of the second diode and the base of the second bipolar transistor. In this case, the input voltage is adjusted so as not to exceed the power supply voltage depending on the configuration of each element, so that malfunction of the operational amplifier can be prevented more reliably.

[0021] Preferably, the input protection circuit adjusts the input signal to be limited by the following formula, where Vlimit+ is the upper limit voltage of the input signal, Vlimit- is the lower limit voltage, Vcc is the positive power supply voltage, Vee is the negative power supply voltage or ground voltage, VBE is the base-emitter voltage of the first and second bipolar transistors, and n×VF is the forward voltage of the first or second diode. Vlimit+=Vcc+VBE-n×VF...Formula 3 Vlimit-=Vee-VBE+n×VF...Formula 4 In this case, the upper and lower limit voltages are limited by the formulas 3 and 4, so that malfunction of the operational amplifier can be prevented more reliably.

[0022] The secondary battery deterioration determination device of the present invention has the above-mentioned input protection circuit, so it can reliably prevent malfunction of the operational amplifier in the input section, and can therefore stably and reliably determine the deterioration of the secondary battery regardless of the voltage state of the input signal. [Effects of the Invention]

[0023] The input protection circuit of the present invention includes a first or second bipolar transistor and one or more first or second diodes connected in series with the first or second bipolar transistor and connected with a polarity opposite to the base-emitter conduction direction of the first or second bipolar transistor, so that an increase or decrease in the forward voltage corresponding to the number of third or fourth diodes is added to an increase or decrease in the base-emitter voltage of the first or second bipolar transistor relative to the power supply voltage, thereby adjusting the input voltage so that it does not exceed the power supply voltage.As a result, even if high-frequency components such as noise or AC components of the input signal exceed the common-mode input voltage range of the operational amplifier, they are limited so as not to exceed the power supply voltage and remain within the common-mode input voltage range, thereby reliably preventing malfunction of the operational amplifier regardless of the voltage state of the input signal. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a configuration diagram showing an input protection circuit according to an embodiment of the present invention; [Figure 2] FIG. 2 is a configuration diagram showing an input protection circuit according to a modified example of FIG. [Figure 3] 1 is a circuit diagram showing an emergency power supply and a secondary battery deterioration determination device including a sensor unit equipped with an input protection circuit of the present invention. [Figure 4] FIG. 2 is a block diagram showing an example of the configuration of a sensor unit. [Figure 5] FIG. 2 is a block diagram showing an example of the configuration of a sensor unit. [Figure 6] FIG. 10 is a block diagram showing another example of the configuration of the sensor unit. [Figure 7] FIG. 2 is a block diagram showing an example of the configuration of a sensor unit. [Figure 8] FIG. 10 is a block diagram showing a modified example of the configuration of the sensor unit. [Figure 9] FIG. 10 is a block diagram showing a modified example of the configuration of the sensor unit. [Figure 10] FIG. 1 is a configuration diagram showing a conventional input protection circuit. [Figure 11]FIG. 1 is a configuration diagram showing a conventional input protection circuit. [Figure 12] FIG. 10 is a diagram showing diode characteristics. DETAILED DESCRIPTION OF THE INVENTION

[0025] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Figure 1 shows the basic configuration of a protection circuit according to one embodiment of the present invention. A first resistor element 1a is arranged in series with the input signal, and the input current is limited by the first resistor element 1a. The other end of the first resistor element 1a is connected to the input terminal of an operational amplifier 2.

[0026] <When the input voltage is high> The emitter of a first bipolar transistor (PNP transistor) 3a is connected between the first resistor element 1a and the input terminal of the operational amplifier 2. The collector of the first bipolar transistor 3a is connected to Vee (negative power supply or GND), and its base is connected to the cathode of a first diode (PN junction diode) 4a and one end of the second resistor element 1b. The other end of the second resistor element 1b is connected to Vee, and the anode of the first PN junction diode 4a is connected to Vcc (positive power supply). The base-emitter voltage (VBE) of the first bipolar transistor 3a has PN junction characteristics and is controlled to maintain a voltage between 0.6 and 0.7V. Therefore, the input voltage of the operational amplifier 2 is limited to an upper limit voltage Vlimit, which is calculated by adding the VBE of the first bipolar transistor 3a to Vcc and subtracting the forward voltage VF of the number n of first PN junction diodes 4a connected in series (n × VF) (Equation 3). Vlimit+=Vcc+VBE-n×VF...Formula 3

[0027] <When the input voltage is low> The emitter of a second bipolar transistor (NPN transistor) 3b is connected between the first resistor element 1a and the input terminal of the operational amplifier 2. The collector of the second bipolar transistor 3b is connected to Vcc (positive power supply), and its base is connected to the anode of a second diode (PN junction diode) 4b and one end of a third resistor element 1c. The other end of the third resistor element 1c is connected to Vcc, and the cathode of the second PN junction diode 4b is connected to Vee. The base-emitter voltage (VBE) of the second transistor 3b has PN junction characteristics and attempts to maintain a voltage between 0.6 and 0.7V. Therefore, the input voltage of the operational amplifier 2 is limited to a lower limit voltage Vlimit-, which is calculated by subtracting the VBE of the second transistor 3b from Vee and adding the forward voltage VF of the number n of series-connected second PN junction diodes 4b (n × VF) (Equation 4). Vlimit-=Vee-VBE+n×VF...Formula 4

[0028] Figure 2 shows another embodiment of the input protection circuit of Figure 1. While three resistor elements 1a are used in Figure 1, the second and third resistor elements 1b and 1c in Figure 1 are replaced by a single resistor element 1d. The rest of the configuration is the same as in the embodiment of Figure 1. The number of elements used is reduced, making it possible to save space in the circuit's mounting area.

[0029] Fig. 3 shows an emergency power supply and a secondary battery deterioration determination device according to another embodiment of the present invention. Fig. 4 shows an example of the configuration of a sensor unit having the above-mentioned input protection circuit. A secondary battery deterioration determination device using the above-mentioned input protection circuit will now be described.

[0030] In Figure 3, the secondary battery whose deterioration is to be determined is an emergency power supply in a data center, a mobile phone base station, or any other power supply device that requires a stable power supply. There are multiple battery groups, each of which is a secondary battery, with multiple batteries connected in series, and these battery groups are connected in parallel to a load. Each battery may be a single cell or multiple cells connected in series.

[0031] Of the positive and negative terminals of the main power supply which are connected to the positive and negative terminals of the load, this emergency battery is connected to the positive terminal via a charging circuit and diode 8, and directly to the negative terminal. Diode 8 is connected in parallel with charging circuit 7 in the direction that causes current to flow from the emergency battery to load 10. Main power supply 6 is, for example, connected to an AC commercial power supply and is made up of a DC power supply or the like that supplies DC power via a rectifier circuit and a smoothing circuit (neither of which are shown).

[0032] The positive potential of the emergency battery is lower than the positive potential of the main power supply, and normally no current flows from the battery to the load. However, if the main power supply stops or its function deteriorates, the potential on the main power supply side drops, and the charge stored in the emergency battery is used to supply power to the load via diode 8.

[0033] The secondary battery degradation determination device of the present invention is a device for determining the degradation of each battery in such a power supply. This secondary battery degradation determination device includes a plurality of sensor units 15 (FIG. 4) individually connected to each battery, a plurality of current sensors 9 connected to each battery group, a current control means 11d for discharging a measurement current containing an AC component from the battery group, a wireless unit 16 provided for each sensor unit 15 and for wirelessly transmitting the measured voltage value of the AC component, and a controller 11 (FIG. 4) for receiving the measurement value transmitted by the wireless unit 16 for each sensor unit, calculating the internal resistance of each battery using the received measurement value, and determining the degradation of the battery from the internal resistance.

[0034] The current control means 11d is composed of a series circuit of a switching element 11da and a current limiting resistor 11db, and is connected in parallel to the battery group. The switching element 11da is a semiconductor element such as a thyristor or transistor. A bypass diode is connected in parallel to the switching element 11da. The switching element 11da is driven to open and close by the current control means 11d of the controller so that the discharge current becomes a pulsed or sinusoidal current. The current control means 11d may be composed of hardware only, or may be configured to include a CPU or microcomputer.

[0035] The sensor unit 15 includes a voltage sensor that detects AC and DC components of voltage, and as shown in FIG. 5, has a radio section 16, a voltage sensor 17, and a temperature sensor 18. The voltage sensor 17 is made up of a sensor function section 17a and an arithmetic control section 17b (FIG. 4), each of which is made up of a protection circuit 17aa, a detection section 17ab, an arithmetic section 17bd, etc. The protection circuit 17aa is the input protection circuit according to the present invention described above. This protection circuit 17aa prevents malfunction of the operational amplifier in the input section, so that deterioration of the secondary battery can be determined stably and reliably regardless of the voltage of the input signal.

[0036] The voltage sensor 17 includes a control unit 17ba that executes a given command, a delay unit 17bb that delays the start of measurement by the detection unit 17ab by a predetermined time in response to the command, a conversion unit 17bc that converts the analog signal of the AC voltage value detected by the voltage sensor 17 into a digital signal, and a calculation unit 17bd that calculates the effective value, average value, or peak value from the digital signal. The voltage sensor 17 also includes a DC detection unit that detects DC voltage, and the detected value of the DC component detected by the DC detection unit is also transmitted from the wireless unit 16 of each sensor unit. The transmission order of each sensor unit 15 is preset by the delay unit 17bb or by other means, and the measurement values are transmitted sequentially in the set order after the transmission delay time. In this embodiment, a temperature sensor 18 is also provided to measure the ambient temperature of the battery and the temperature of the battery. The wireless unit 16, voltage sensor 17, and temperature sensor 18 constitute the sensor unit 15. The temperature detected by the temperature sensor 18 is transmitted to the controller 11 via the wireless unit 16 of each sensor unit, together with the voltage measurement value of the voltage sensor 17, which is the effective value or average value.

[0037] In this embodiment, the controller 11 comprises a main controller 11A connected to a data server 14 and a monitor 13 via a communication network 12. In this embodiment, the communication network 12 comprises a LAN and has a hub 12a. The communication network 12 may also be a wide area communication network. The data server 14 can communicate with a personal computer (not shown) or the like in a remote location via the communication network 12 or another communication network, allowing data monitoring from anywhere.

[0038] FIG. 6 shows another configuration of the sensor unit. Figure 6 shows a configuration in which multiple voltage sensors 17 are arranged in the sensor unit of Figure 4. In this case, the wireless unit 16 can be shared, which reduces costs and the number of wireless connections, thereby shortening communication time. Also, even if there is a limit to the number of wireless connections, it becomes possible to monitor many batteries.

[0039] Although not shown, a conversion unit 17bc converts the analog signal of the detected value into a digital signal, and the calculation unit 17bd calculates the effective value, average value, or peak value. The conversion units 17bc may be provided in numbers equal to the number of voltage sensors, or one may be used by switching between them. The calculation unit 17bd is comprised of a CPU or microcomputer, and may be shared by all sensor units.

[0040] As shown in FIG. 6, the sensor unit 15 includes a protection circuit 17aa that limits the input voltage to the calculation unit 17bd, multiple detection units 17ab that individually detect the voltage between the battery's terminals, and multiple calculation units 17bd that individually calculate the AC component from the signals detected by each of the detection units 17ab. The protection circuit 17aa of the sensor unit 15 limits the input voltage so that the voltage does not exceed a specified value. The detection unit 17ab of the sensor unit 15 outputs the detected AC voltage as an analog signal. Although not shown, a conversion unit 17bc converts the analog signal of the detected value into a digital signal, and the calculation unit 17bd calculates the effective value, average value, or peak value. The detection unit 17ab also has a function of detecting DC voltage, and the detected DC component is transmitted by the wireless unit 16 via the calculation unit 17bd or directly. The multiple detection units 17ab and the multiple calculation units 17bd constitute a detection / calculation unit. The appropriate number of protection circuits 17aa and detection units 17ab varies depending on whether the battery voltage is 2 V, 6 V, 12 V, etc., but is preferably 2 or more and less than 10, and may be 2 to 8, or 4 to 6. A feature of this configuration is that by arranging multiple voltage sensors 17 in sensor unit 15, wireless unit 16 can be shared, which reduces costs and the number of wireless connections, thereby shortening communication time.

[0041] Figure 7 shows a modified example of the configuration of the sensor unit. Figure 8 shows a modified example of the configuration of the sensor unit. In the embodiment shown in FIG. 6, sensor unit 15 includes protection circuit 17aa, detection unit 17ab, and calculation unit 17bd for each battery whose deterioration is to be detected. However, as shown in the modified examples shown in FIGS. 7 and 8, sensor unit 15 may include protection circuit 17aa that limits the input voltage of the inter-terminal voltage to calculation unit 17bd, one detection unit 17ab that performs individual detection, a switching unit 17bf that switches between the multiple batteries connected to detection unit 17ab, and one calculation unit 17bd that individually calculates the AC component from the signal detected by detection unit 17ab. The AC component calculated by calculation unit 17bd and the DC component obtained by detection unit 17ab are temporarily stored in memory unit 17be, and the stored calculation results are transmitted from wireless unit 16. Note that memory unit 17be is not necessarily provided. In that case, the calculation results are transmitted from wireless unit 16 each time calculation unit 17bd performs a calculation. In the configurations shown in FIGS. 7 and 8, the detection unit 17ab only needs to be connected to the switching unit 17bf on its input side, simplifying the wiring. In the example shown in FIG. 7, the switching unit 17bf is configured to share the lowest potential terminal among the series-connected batteries to be detected by one sensor unit 15. This configuration simplifies the configuration of the switching unit 17bf. In the example shown in FIG. 8, the switching unit 17bf is configured to sequentially switch the low-potential and high-potential terminals connected to the protection circuit 17aa for each battery. While this configuration requires the switching unit 17bf, only one protection circuit 17aa, detection unit 17ab, and calculation unit 17bd are required, thereby reducing the number of circuit elements, such as the protection circuit 17aa, detection unit 17ab, calculation unit 17bd, and switching unit 17bf.

[0042] FIG. 9 shows a modified example of the configuration of the sensor unit. A modified example of the sensor unit 15 is shown. In this example, the sensor unit 15 includes multiple detectors 17ab that individually detect the voltage between the battery terminals, a protection circuit 17aa that limits the voltage of the signals detected by the detectors 17ab, a data selector 17bg that switchably selects and outputs the signals detected by the detectors 17ab, and a single calculator 17bd that individually calculates the AC components from the signals selected by the data selector. The sensor unit 15 also includes a memory 17be that stores the results of calculations performed by the calculator 17bd. The measured voltage values of each battery, detected by each detector 17ab, selected by the data selector 17bg, and converted to effective values or the like by the calculator, are temporarily stored in the memory 17be and sequentially output from the wireless unit 16. The detectors 17ab are each composed of a differential calculation circuit, and the multiple detectors 17ab, each composed of a differential calculation circuit, constitute a differential calculation unit 17ac, which may be a sensor array or a sensor module. When a data selection unit 17bg is provided as in this example, only one calculation unit 1bd is required.

[0043] In this way, the input protection circuit of the present invention can control the upper and lower limit voltages of the protection circuit's output voltage by adjusting the number of PN junction diodes connected in series. This ensures that even if the input signal exceeds the common-mode input voltage range of the operational amplifier, it remains within the common-mode input voltage range at the input stage of the operational amplifier. Therefore, operational amplifier malfunction can be reliably prevented regardless of the voltage state of the input signal. Furthermore, this input protection circuit allows for reliable and consistent determination of secondary battery degradation regardless of the voltage state of the input signal.

[0044] Although the embodiments for carrying out the present invention have been described above based on the examples, the embodiments disclosed herein are illustrative in all respects and are not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0045] 1a: First resistive element 1b: Second resistive element 1c: Third resistive element 2: Operational amplifier 3a: First bipolar transistor 3b: second bipolar transistor 4a: First diode 4b: Second diode 15: Sensor unit 17aa: Input protection circuit

Claims

1. A first bipolar transistor connected between an input terminal and a negative power supply or ground, A first diode connected in a polarity opposite to the conduction direction between the base and emitter of the first bipolar transistor, and one or more first diodes connected in series in the same polarity between the positive power supply and the negative power supply or ground, A second bipolar transistor connected between the input terminal and the positive power supply, A second diode connected in a polarity opposite to the conduction direction between the base and emitter of the second bipolar transistor, and one or more second diodes connected in series in the same polarity between the positive power supply and the negative power supply or ground, An input protection circuit for preventing malfunction of an operational amplifier due to an input voltage input from the input terminal, An input protection circuit that adjusts the input voltage so as not to exceed the power supply voltage by giving a decrease or increase in the forward voltage corresponding to the number of the first or second diodes to an increase or decrease in the base-emitter voltage of the first or second bipolar transistor with respect to the power supply voltage of the positive power supply, the negative power supply, or ground.

2. In claim 1, One is connected to the input terminal, the other is connected to the emitters of the first and second bipolar transistors and a first resistor element connected to the input stage of the operational amplifier, One or more first diodes having an anode connected to the positive power supply and a cathode connected to the base of the first bipolar transistor and one end of a second resistor element, The first bipolar transistor having a collector connected to the negative power supply or ground, a base connected to the cathode of the first diode and one end of the second resistor element, and an emitter connected to the input stage of the operational amplifier and the other end of the first resistor element, The second resistor element having one end connected to the cathode of the first diode and the base of the first bipolar transistor and the other end connected to the negative power supply or ground, One or more second diodes having an anode connected to the base of the second bipolar transistor and one end of a third resistor element and a cathode connected to the negative power supply or ground, Connect the collector to the positive power supply, the base to the anode of the second diode and one of the third resistor elements, and the emitter to the input stage of the operational amplifier and the other of the first resistor elements for the second bipolar transistor, An input protection circuit comprising a third resistor element having one connected to the anode of the second diode and the base of the second bipolar transistor and the other connected to the positive power supply.

3. In claim 1, One is connected to the input terminal, the other is connected to the emitters of the first and second bipolar transistors and the first resistor element connected to the input stage of the operational amplifier, One or more first diodes connected in series with the anode connected to the positive power supply and the cathode connected to the base of the first bipolar transistor and one of the second resistor elements, Connect the collector to the negative power supply or ground, the base to the cathode of the first diode and one of the second resistor elements, and the emitter to the input stage of the operational amplifier and the other of the first resistor elements for the first bipolar transistor, One or more second diodes connected in series with the anode connected to the base of the second bipolar transistor and the other of the second resistor elements and the cathode connected to the negative power supply or ground, Connect the collector to the positive power supply, the base to the anode of the second diode and the other of the second resistor elements, and the emitter to the input stage of the operational amplifier and the other of the first resistor elements for the second bipolar transistor, An input protection circuit comprising a second resistor element having one connected to the cathode of the first diode and the base of the first bipolar transistor and the other connected to the anode of the second diode and the base of the second bipolar transistor.

4. In any one of claims 1 to 3, When the upper limit voltage of the input voltage is Vlimit+, the lower limit voltage is Vlimit-, the positive power supply voltage is Vcc, the negative power supply voltage or the ground voltage is Vee, the base-emitter voltage of the first and second bipolar transistors is VBE, and the forward voltage of the first or second diode is n×VF, an input protection circuit that adjusts to be limited by the following formula. Vlimit+ = Vcc + VBE - n×VF Vlimit- = Vee - VBE + n×VF

5. The input protection circuit according to any one of claims 1 to 3, wherein the first bipolar transistor is a PNP transistor and the second bipolar transistor is an NPN transistor.

6. A secondary battery deterioration determination device using the input protection circuit according to any one of claims 1 to 5.

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