JP7765211B2 - Input protection circuit and secondary battery deterioration determination device using the same - Google Patents

Description

The present invention relates to devices that have a wide or indefinite voltage range for external devices connected to the input section of devices that measure voltages, such as various sensors, and relates to an input protection circuit for the input section and a secondary battery deterioration determination device using the same.

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).

In addition, conventional input protection circuits are equivalent to an integrator circuit configured based on a combination of the capacitance of a resistor element and a diode element, and in order to solve the problem of not being able to achieve high-speed operation 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).

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

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.

Japanese Patent Application Publication No. 8-32025 Japanese Patent Application Laid-Open No. 2001-110993

Analog Dialogue OCT2015VOL49 "Voltage Clamps Using ESD Diodes" (http://www.analog.com/jp/analog-dialogue/articles/esd-diodes-as-voltage-clamps.html)

However, in sensor circuits and other devices that require high-precision detection, analog inputs are input to operational amplifiers (op-amps) consisting of transistor differential amplifier circuits, where they are amplified and subjected to differential calculations. In protection circuits that use PN junction diodes, the forward voltage _VF of the PN junction diodes 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.

A conventional protection circuit is shown in Fig. 9. When 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...Formula 1
Vlimit-=Vee-VF...Formula 2

Using a Schottky barrier diode instead of a PN junction diode can suppress the forward voltage VF to approximately 0.2V, but the input voltage will still exceed the common-mode input voltage range of the operational amplifier, and there is the possibility of the operational amplifier malfunctioning, just as with protection circuits using PN junction diodes. Furthermore, 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 calculation.

Figure 10 shows a conventional input protection circuit using Schottky barrier diodes. Figure 10 shows a configuration in which the PN junction diodes 4, 4 shown in equations 1 and 2 in the conventional input protection circuit (Figure 9) have been replaced with Schottky barrier diodes 5, 5 to reduce the effect of the forward voltage. Schottky barrier diodes have the advantage of having a small forward voltage VF of approximately 0.2 V.

On the other hand, Schottky barrier diodes have the diode characteristics shown in Figure 11, and have a larger leakage current (IR) than PN junction diodes. This leakage current causes a voltage drop in the stage before the operational amplifier input, resulting in measurement errors. When precise measurements are required, input protection circuits using Schottky barrier diodes are not suitable.

In light of the problems with the prior art described above, the present invention aims to provide an input protection circuit that prevents measurement errors in operational amplifiers regardless of the voltage state of the input signal, and a secondary battery degradation determination device using the same.

The input protection circuit according to the present invention comprises a first diode and one or more third diodes connected in series in the same direction and having a polarity opposite to that of the first diode, between an input terminal and a positive power supply;
a second diode and a fourth diode connected in a direction opposite to the second diode and one or more fourth diodes connected in series in the same direction between the input terminal and a negative power supply or ground,
An input protection circuit that prevents malfunction of an operational amplifier due to an input voltage,
The input voltage is adjusted so that it does not exceed the power supply voltage by adding an increase or decrease in the forward voltage of the first or second diode to the power supply voltage of the positive power supply, negative power supply, or ground, in accordance with the number of the third or fourth diodes.

With this configuration, the first or second diode and one or more third or fourth diodes connected in series are connected in opposite polarity directions. Therefore, the increase or decrease in the forward voltage of the first or second diode is multiplied by the increase or decrease in the forward voltage depending on the number of third or fourth diodes, 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 to stay within the common-mode input voltage range and do not exceed the power supply voltage, thereby reliably preventing operational amplifier malfunction regardless of the voltage state of the input signal.

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

In other words, in the case of a rail-to-rail operational amplifier with a wide common-mode input voltage range of the power supply voltage + 0.2 to 0.3 V, one or two PN junction diodes of the third or fourth diode can be used. 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 of the diode group can be used to suppress the input signal voltage within the common-mode input voltage range of the operational amplifier.

Preferably, a first resistor element connected at one end to the input terminal and at the other end to the anode of the first diode, the cathode of the second diode, and the input stage of the operational amplifier;
one or more third diodes connected in series, each having an anode connected to the positive power supply and a cathode connected to the cathode of the first diode, one of the first capacitance elements, and one of the second resistance elements;
the first capacitance element having the other end connected to the positive power supply; and a fourth diode having an anode connected to the anode of the second diode, one end of the second capacitance element, and the other end of the second resistance element, the fourth diode being one or more diodes connected in series;
the second capacitance element having the other end connected to the negative power supply or ground;
One end of the second resistor is connected to the cathode of the first diode, the cathode of the third diode, and one end of the first capacitance element, and the other end of the second resistor is connected to the anode of the second diode, the anode of the fourth diode, and one end of the second capacitance element.
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.

Preferably, when 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, the forward voltage of the first and second diodes is VF, and the forward voltage of the third or fourth diode is n×VF (n is a number equal to or greater than 1), the adjustment is performed as shown in the following equations (Equations 3 and 4):
Vlimit+=Vcc+VF-n×VF...Formula 3
Vlimit-=Vee-VF+n×VF...Formula 4
In this case, the upper and lower limit voltages are limited as shown in Equations 3 and 4, so that malfunction of the operational amplifier can be prevented more reliably.

The secondary battery degradation determination device of the present invention has the input protection circuit described above, which reliably prevents malfunction of the operational amplifier in the input section, allowing for stable and reliable determination of secondary battery degradation regardless of the voltage state of the input signal.

In the input protection circuit of the present invention, the first or second diode and one or more third or fourth diodes connected in series are connected in opposite polarity directions. Therefore, the input voltage is adjusted so that it does not exceed the power supply voltage by adding an increase or decrease in the forward voltage of the first or second diode to an increase or decrease in the forward voltage depending on the number of third or fourth diodes. This limits high-frequency components such as noise or AC components of the input signal to within the common-mode input voltage range of the operational amplifier, preventing them from exceeding the power supply voltage and constraining them within that common-mode input voltage range. Therefore, operational amplifier malfunction can be reliably prevented regardless of the voltage state of the input signal.

1 is a configuration diagram showing an input protection circuit according to an embodiment of the present invention; 2 is a circuit diagram showing an emergency power supply and a secondary battery deterioration determination device including a sensor unit equipped with the input protection circuit of FIG. 1. FIG. 2 is a block diagram showing an example of the configuration of a sensor unit. FIG. 2 is a block diagram showing an example of the configuration of a sensor unit. FIG. 10 is a block diagram showing another example of the configuration of the sensor unit. FIG. 2 is a block diagram showing an example of the configuration of a sensor unit. FIG. 10 is a block diagram showing a modified example of the configuration of the sensor unit. FIG. 10 is a block diagram showing a modified example of the configuration of the sensor unit. FIG. 1 is a configuration diagram showing a conventional input protection circuit. FIG. 1 is a configuration diagram showing a conventional input protection circuit. FIG. 10 is a diagram showing diode characteristics.

Embodiments of the present invention will now be described with reference to the drawings. Figure 1 shows the basic configuration of an input 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 the operational amplifier 2.

<When the input voltage is high>
The anode of a first diode (PN junction diode) 4c is connected between the first resistance element 1a and the input stage of the operational amplifier 2. The cathode of the first PN junction diode 4c is connected to one side of the first capacitance element 3a, the cathode of the third diode (PN junction diode) 4a, and one side of the second resistance element 1b, and the other side of the first capacitance element 3a and the anode of the third PN junction diode 4a are connected to Vcc (positive power supply).

Since the AC component is absorbed by charging and discharging the first capacitance element 3a, the input voltage of the operational amplifier 2 is limited to an upper limit voltage _Vlimit+ obtained by adding approximately 0.7 V, which is the forward voltage VF of the first PN junction diode 4c, to Vcc and subtracting the forward voltage VF (n × VF) of the number n of third PN junction diodes 4a connected in series (Equation 3).
Vlimit+=Vcc+VF-n×VF...Formula 3

<When the input voltage is low>
The cathode of a second diode (PN junction diode) 4d is connected between the first resistance element 1a and the input stage of the operational amplifier 2. The anode of the second PN junction diode 4d is connected to one side of the second capacitance element 3b, the anode of the fourth diode (PN junction diode) 4b, and the other side of the second resistance element 1b, and the other side of the second capacitance element 3b and the anode of the fourth PN junction diode 4b are connected to Vee (negative power supply or GND).

Since the AC component is absorbed by charging and discharging the second capacitance element 3b, the input voltage of the operational amplifier 2 is limited to a lower limit voltage Vlimit- obtained by subtracting approximately 0.7 V, which is the forward voltage VF of the second PN junction diode 4d, from Vee and adding the forward voltage VF (n×VF) of the number n of second PN junction diodes 4b connected in series (Equation 4).
Vlimit-=Vee-VF+n×VF...Formula 4

Figure 2 shows an emergency power supply and secondary battery degradation determination device according to another embodiment of the present invention. Figure 3 shows an example configuration of a sensor unit having the above-mentioned input protection circuit. Below, we will explain a secondary battery degradation determination device using the above-mentioned input protection circuit.

In Figure 2, the secondary battery being assessed for deterioration is an emergency power source in a data center, a mobile phone base station, or any other power supply device that requires a stable power supply. It has multiple battery groups, each of which is a secondary battery, 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.

This emergency battery is connected to the positive and negative terminals of the main power supply, which is connected to the positive and negative terminals of the load, 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 current flows from the emergency battery to load 10. Main power supply 6 is, for example, connected to a commercial AC power source and consists of a DC power supply that supplies DC power via a rectifier circuit and a smoothing circuit (neither of which are shown).

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 functionality 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.

The secondary battery degradation determination device of the present invention is a device that determines the degradation of each battery in such a power supply. This secondary battery degradation determination device includes multiple sensor units 15 (Figure 3) individually connected to each battery, multiple current sensors 9 connected to each battery group, current control means 11d that discharges a measurement current containing an AC component from the battery group, a wireless unit 16 provided for each sensor unit 15 that wirelessly transmits the measured voltage value of the AC component, and a controller 11 (Figure 3) that receives the measurement value transmitted by the wireless unit 16 for each sensor unit, calculates the internal resistance of each battery using the received measurement value, and determines the degradation of the battery from the internal resistance.

The current control means 11d consists 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 include a CPU or microcomputer.

The sensor unit 15 includes a voltage sensor that detects the AC and DC components of the voltage, and as shown in Figure 4, has a radio section 16, a voltage sensor 17, and a temperature sensor 18. The voltage sensor 17 consists of a sensor function section 17a and an arithmetic control section 17b (Figure 3), each of which consists of a protection circuit 17aa, a detection section 17ab, and an arithmetic section 17bd. 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 deterioration of the secondary battery can be determined stably and reliably regardless of the voltage of the input signal.

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. Furthermore, the transmission order of each sensor unit 15 is preset by the delay unit 17bb or other means using a transmission delay time, 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, along with the voltage measurement value (effective value or average value) from the voltage sensor 17, is transmitted to the controller 11 via the wireless unit 16 of each sensor unit.

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 includes a hub 12a. The communication network 12 may also be a wide-area communication network. The data server 14 can communicate with a remote personal computer (not shown) or the like via the communication network 12 or other communication networks, allowing data monitoring from anywhere.

FIG. 5 shows another configuration of the sensor unit.
Figure 5 shows a configuration in which multiple voltage sensors 17 are installed in the sensor unit of Figure 3. In this case, the wireless unit 16 can be shared, which reduces costs and the number of wireless connections, thereby shortening communication time. Furthermore, even if the number of wireless connections is limited, it becomes possible to monitor many batteries.

Although not shown, the 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. There may be as many conversion units 17bc as there are voltage sensors, or one may be used by switching between them. The calculation unit 17bd is made up of a CPU or microcomputer, and may be shared by all sensor units.

As shown in FIG. 5, 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 these 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 the function of detecting DC voltage, and the detected value of the 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 2V, 6V, 12V, etc., but is preferably 2 or more and less than 10, or may be 2 to 8, or 4 to 6. A feature of this configuration is that by placing multiple voltage sensors 17 in the sensor unit 15, the wireless unit 16 can be shared, which reduces costs and the number of wireless connections, thereby shortening communication time.

6 and 7 show modified examples of the configuration of the sensor unit.
In the embodiment shown in FIG. 5, 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. 6 and 7, 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 such a case, the calculation results are transmitted via wireless unit 16 each time calculation unit 17bd performs a calculation. In the configurations shown in Figures 6 and 7, 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 Figure 6, the switching unit 17bf is configured to share the lowest potential terminal among the series-connected batteries that are the detection targets of one sensor unit 15. This configuration simplifies the configuration of the switching unit 17bf. In the example shown in Figure 7, 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.

FIG. 8 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 the data selection unit 17bg is provided as in this example, only one calculation unit 1bd is required.

In this way, the input protection circuit of the present invention can control the upper and lower limit voltages of the output voltage of the input protection circuit 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 is limited to within the common-mode input voltage range of the operational amplifier 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 enables reliable and stable determination of secondary battery deterioration regardless of the voltage state of the input signal.

The above describes the mode for carrying out the present invention based on examples, but the embodiments disclosed herein are illustrative in all respects and are not limiting. The scope of the present invention is indicated by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims.

1a: first resistive element 1b: second resistive element 2: operational amplifier 3a: first capacitive element 3b: second capacitive element 4a: third diode 4b: fourth diode 4c: first diode 4d: second diode 15: sensor unit 17aa: input protection circuit

Claims (3)

a first diode and a third diode connected in a direction opposite to the first diode and one or more third diodes connected in series in the same direction between the input terminal and a positive power supply;
a second diode and a fourth diode connected in a direction opposite to the second diode and one or more fourth diodes connected in series in the same direction between the input terminal and a 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 that it does not exceed a power supply voltage by adding an increase or decrease in a forward voltage of the first or second diode corresponding to the number of the third or fourth diodes to an increase or decrease in a forward voltage of the first or second diode relative to a power supply voltage of the positive power supply, the negative power supply, or ground;
This input protection circuit is
a first resistor element connected at one end to the input terminal and at the other end to the anode of the first diode, the cathode of the second diode, and the input stage of the operational amplifier;
an anode of one or more diode elements in the third diode is connected to the positive power supply, a cathode of the one or more diode elements is connected to the cathode of the first diode, one of the first capacitance elements, and one of the second resistance elements, and the other of the first capacitance elements is connected to the positive power supply;
a cathode of one or more diode elements in the fourth diode is connected to the negative power supply or ground, an anode is connected to the anode of the second diode, one of the second capacitance elements, and the other of the second resistance element, and the other of the second capacitance element is connected to the negative power supply or ground,
an input protection circuit, wherein one end of the second resistance element is connected to the cathode of the first diode, the cathode of the third diode, and one end of the first capacitance element, and the other end of the second resistance element is connected to the anode of the second diode, the anode of the fourth diode, and one end of the second capacitance element . In claim 1 ,
An input protection circuit that adjusts the input voltage as shown in the following formula, where an upper limit voltage of the input voltage is Vlimit+, a lower limit voltage is Vlimit-, the positive power supply voltage is Vcc, the negative power supply voltage or ground voltage is Vee, the forward voltage of the first and second diodes is VF, and the forward voltage of the third or fourth diode is n×VF (n is a number equal to or greater than 1).
Vlimit+=Vcc+VF-n×VF
Vlimit-=Vee-VF+n×VF 3. A secondary battery deterioration determination device using the input protection circuit according to claim 1 .