Voltage detection circuit

Abstract

The present invention provides a voltage detection circuit, which comprises: a voltage divider circuit, which is composed of a series resistor connected between a voltage input terminal and a constant voltage terminal; a voltage comparison circuit, which compares the voltage divided by the voltage divider circuit with a reference voltage; and an output terminal, which outputs the comparison result of the voltage comparison circuit. The voltage detection circuit detects whether the voltage input to the voltage input terminal exceeds or falls below a predetermined voltage value, and outputs a signal from the output terminal. The voltage detection circuit is provided with a detection voltage adjustment terminal (ADJ) connected to an external resistor, a voltage-current conversion circuit (13) provided between the detection voltage adjustment terminal and the voltage divider circuit, and a constant current source (CS) connected between an internal power supply voltage terminal and the detection voltage adjustment terminal. The detection voltage can be adjusted by extracting a current corresponding to the resistance value of the external resistor from the connection node of the series resistor of the voltage divider circuit by the voltage-current conversion circuit.

Description

Technical Field

[0001] The present invention relates to a voltage detection circuit that monitors the voltage of a battery, etc. and outputs a detection signal when it detects that the voltage exceeds or falls below a predetermined voltage value. In particular, it relates to a technology that is effectively used in a semiconductor integrated circuit for voltage detection, which has a function of adjusting the detection voltage value through an external terminal. Background Art

[0002] If a battery, such as one installed in an automobile, experiences voltage abnormalities due to a malfunction or wear and tear, it can impair battery performance or cause electronic devices powered by it to malfunction. Therefore, a voltage detection circuit is provided that outputs a detection signal when the battery voltage deviates from a predetermined range. Furthermore, a voltage detection semiconductor integrated circuit (voltage detection IC) is provided as an element or component having this function.

[0003] Among existing voltage detection ICs, Figure 3 As shown, there is a series resistor R for dividing the voltage of the voltage input terminal VS. I1 、R I2 ; R I1 、R I2 The voltage after voltage division is equal to the predetermined reference voltage V REF The comparator COMP for comparison and the transistor M1 connected between the output terminal OUT and the ground point and having the output voltage of the comparator COMP applied to the gate terminal are provided. This voltage detection IC is inexpensive due to its simple structure and small number of components. PULL By connecting to the output terminal OUT, a detection signal DS can be generated, and thus it has the advantage of being easy to use.

[0004] In the Figure 3 When the voltage detection IC shown below is used to detect the battery voltage, current flowing through the resistor R I1 、R I2 The current is dark current for the battery, so the resistor R I1 、R I2 The resistance value is usually set to tens of megohms (MΩ). On the other hand, the detection voltage of the voltage detection IC is determined by the resistor R I1 、R I2 The resistance ratio and reference voltage V REF Therefore, when designing and studying a system using a voltage detection IC, if you want to use a voltage value different from the IC's inherent detection voltage, Figure 3 As shown, connect an external resistor R to the voltage input terminal VS E1 、R E2 , R E1 、RE2 The divided voltage is input to the voltage input terminal VS, thereby adjusting the detection voltage value.

[0005] However, if the external resistor R E1 、R E2 The resistance value is greater than the IC's internal resistance R I1 、R I2 If the resistance value is high (e.g. tens of megohms (MΩ)), then due to the internal resistance R I1 、R I2 The deviation of the adjusted detection voltage makes the deviation, so the external resistor R E1 、R E2 The resistance value is set to the same as the internal resistance R I2 、R I2 The resistance value is small enough (hundreds of kilo-ohms (kΩ)). However, if the external resistor R E1 、R E2 The resistance value is small, then the current flowing through these resistors R E1 、R E2 The current increases, which increases the dark current of the battery. Furthermore, in order to set the detection voltage to the desired value without increasing the dark current, multiple voltage detection ICs with different detection voltages must be prepared in advance. This increases the evaluation time and complicates inventory management.

[0006] As inventions related to voltage detection circuits for detecting abnormal voltage of batteries, there are inventions described in Patent Documents 1 and 2. However, in the voltage detection circuits described in Patent Documents 1 and 2, there is no description of connecting an external resistor R E1 、R E2 The detection voltage value can be adjusted.

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2002-357625

[0008] Patent Document 2: Japanese Patent Application Laid-Open No. 2006-275928 Summary of the Invention

[0009] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a voltage detection circuit which, when used to detect battery voltage, can adjust the detection voltage value by an external resistor without increasing the dark current of the battery.

[0010] Furthermore, another object of the present invention is to provide a voltage detection circuit that can detect a voltage value with high accuracy.

[0011] In order to achieve the above object, the present invention is a voltage detection circuit having:

[0012] A voltage input terminal for inputting a voltage of a monitored object;

[0013] a voltage divider circuit consisting of a series resistor connected between the voltage input terminal and the constant voltage terminal;

[0014] a voltage comparison circuit for comparing the voltage divided by the voltage divider circuit with a predetermined voltage; and

[0015] an output terminal for outputting a comparison result of the voltage comparison circuit,

[0016] The voltage detection circuit is formed as a semiconductor integrated circuit on a semiconductor substrate, detects whether the voltage input to the voltage input terminal exceeds or falls below a predetermined voltage value, and outputs a signal from the output terminal.

[0017] The voltage detection circuit has:

[0018] Detection voltage adjustment terminal, which is connected to an external resistor;

[0019] a voltage-current conversion circuit, which is provided between the detection voltage adjustment terminal and the voltage dividing circuit; and

[0020] a constant current source connected between the internal power supply voltage terminal and the detection voltage adjustment terminal,

[0021] The detection voltage of the voltage input terminal can be adjusted by the voltage-current conversion circuit extracting a current corresponding to the resistance value of the external resistor connected to the detection voltage adjustment terminal from the connection node of the series resistors of the voltage divider circuit.

[0022] With this configuration, since large currents do not flow through the external resistor used to adjust the detection voltage, when used for battery voltage detection, the detection voltage value can be adjusted using the external resistor without increasing the battery's dark current. Furthermore, since dark current can be reduced, the battery can be stored for extended periods of time. Furthermore, since the effect of internal resistance variations on the detection voltage is suppressed, highly accurate voltage detection is possible.

[0023] Furthermore, it is desirable that the voltage-current conversion circuit be configured to include: a transistor and a resistor connected in series between a connection node of the series resistors of the voltage divider circuit and a ground point; and a differential amplifier circuit that inputs the voltage of the detection voltage adjustment terminal to a first input terminal and inputs the potential of the connection node between the transistor and the resistor to a second input terminal.

[0024] The output of the differential amplifier circuit is applied to the control terminal of the transistor.

[0025] The above structure allows the voltage-current conversion circuit to be constructed using a relatively simple circuit, thereby suppressing the increase in current consumption associated with the addition of circuitry. Furthermore, the voltage adjustment function can be easily disabled simply by wiring the voltage adjustment terminal to a ground potential, thus improving ease of use.

[0026] Here, it is assumed that the voltage to be monitored is the voltage of a battery.

[0027] Furthermore, it is considered that the battery is a battery mounted on a vehicle.

[0028] The voltage detection circuit of the present invention, when used for battery voltage detection, can adjust the detection voltage value using an external resistor without increasing the battery's dark current. Furthermore, this eliminates the need for preparing multiple voltage detection ICs with different detection voltage values. Furthermore, the present invention provides a voltage detection circuit with high detection voltage accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a circuit configuration diagram showing one embodiment of a voltage detection circuit according to the present invention.

[0030] Figure 2 It is a circuit configuration diagram showing a modified example of the voltage detection circuit according to the embodiment.

[0031] Figure 3 1 is a circuit configuration diagram showing an example of a conventional voltage detection circuit. DETAILED DESCRIPTION

[0032] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0033] Figure 1 1 is a circuit diagram showing a voltage detection circuit according to an embodiment of the present invention. Figure 1 In the voltage detection circuit 10 , although not particularly limited, circuit elements in a range surrounded by a solid-line frame denoted by reference numeral 10 are formed as a semiconductor integrated circuit (battery voltage detection IC) on one semiconductor substrate (semiconductor chip).

[0034] The voltage detection circuit 10 of the present embodiment includes a voltage input terminal VS to which a power supply voltage V is applied from a battery 20 as a voltage detection target. BATThe circuit 10 includes an output terminal OUT for outputting a detection signal Vd to an external control device (CPU); a detection voltage adjustment terminal ADJ for externally adjusting the detection voltage; and a ground terminal GND serving as a constant voltage terminal to which a ground potential is applied. The battery 20 to be detected as a voltage target is, for example, an on-board battery. In this case, the voltage detection circuit 10 is mounted on a circuit board or the like mounted on the vehicle.

[0035] In addition, the voltage detection circuit 10 includes a voltage divider circuit 11 composed of a resistor R connected in series between the voltage input terminal VS and the ground point. I1 、R I2 and a voltage comparator circuit (comparator: COMP) 12, which divides the voltage of the voltage divider circuit 11 and a predetermined reference voltage V REF Make a comparison.

[0036] Here, the resistor R I1 、R I2 The resistance value is set to tens of megohms (MΩ), so that a small current of about several microamperes (μA) flows. REF For example, set it to a value such as 1V.

[0037] Furthermore, the voltage detection circuit 10 of this embodiment includes: a MOS transistor M1 connected between the output terminal OUT and the ground point (GND); a voltage-current conversion circuit 13 connected to the detection voltage adjustment terminal ADJ and converting the voltage at the detection voltage adjustment terminal ADJ into a current; and a detection voltage setting constant current source CS connected between the internal power supply voltage terminal Vcci of the IC and the detection voltage adjustment terminal ADJ. The constant current source CS is designed to flow a current I1 of, for example, 1 μA. A resistor R connected between the detection voltage adjustment terminal ADJ and the ground point is connected to the detection voltage adjustment terminal ADJ. E1 This is an external adjustment resistor.

[0038] The voltage-current conversion circuit 13 includes a differential amplifier (differential amplifier circuit) AMP having a non-inverting input terminal connected to the detection voltage adjustment terminal ADJ, a MOS transistor M2, and a resistor R I3 , which is connected in series with the resistor R constituting the voltage divider circuit 11 I1 With R I2 The connection node N1 of the MOS transistor M2 is connected to the ground point so that the MOS transistor M2 and the resistor R I3 The potential of the connection node N2 is fed back to the inverting input terminal of the differential amplifier AMP. E1 This constitutes the detection voltage adjustment circuit 14 .

[0039] In addition, in the voltage detection circuit 10 of the present embodiment, the output terminal OUT is connected to the power supply voltage terminal V PULL A pull-up resistor R is connected between the PULL .

[0040] The output voltage of the voltage comparison circuit 12 is applied to the gate terminal of the MOS transistor M1. When the voltage divided by the voltage divider circuit 11 is higher than the reference voltage V REF When the output voltage of the voltage comparator circuit 12 changes to a low level, the MOS transistor M1 is turned off. PULL The current is cut off, and the voltage of the output terminal OUT changes from low level to high level (V PULL ) and provides the voltage as a detection signal Vd to a control device (CPU) not shown.

[0041] Thus, the control device (CPU) receiving the detection signal Vd can recognize the battery voltage Vd during the charging process of the battery 20. BAT The predetermined voltage value is reached.

[0042] In addition, when the battery 20 is discharged so that the battery voltage V BAT When the voltage becomes lower than the predetermined voltage value, the output voltage of the voltage comparator circuit 12 changes to a low level, and the MOS transistor M1 is turned off. Then, current flows through the pull-up resistor R PULL , the voltage of the output terminal OUT changes from a high level to a low level. As a result, the control device (CPU) outside the figure can recognize the voltage V BAT drops below a predetermined voltage.

[0043] Next, the function and operation of the detection voltage adjustment circuit 14 will be described.

[0044] The detection voltage adjustment circuit 14 is connected to the resistor R I1 and R I2 By drawing current from the connection node N1 and adjusting the potential of the connection node N1, the detection voltage of the voltage comparison circuit 12 can be changed. Specifically, by changing the external adjustment resistor R connected to the detection voltage adjustment terminal ADJ, the detection voltage of the voltage comparison circuit 12 can be changed. E1 By adjusting the resistance value of the connection node N1, the current drawn from the connection node N1 can be adjusted to change the potential of the connection node N1, thereby changing the detection voltage of the voltage comparator circuit 12.

[0045] Furthermore, in the detection voltage adjustment circuit 14 of this embodiment, by lowering the potential of the detection voltage adjustment terminal ADJ to the ground potential (0V), the detection voltage adjustment circuit 14 can be hidden from the voltage comparison circuit 12. Specifically, when the potential of the detection voltage adjustment terminal ADJ is set to the ground potential, the output of the differential amplifier AMP is set to the ground potential, and the MOS transistor M2 is turned off. As a result, the resistor R I1 With R I2 The current drawn from the connection node N1 is zero, thereby being able to be compared with a circuit (for example, Figure 3 ) operates at the same detection voltage.

[0046] That is, at this time, the detection voltage V DET The potential becomes the potential represented by the following formula (1).

[0047] V DET =V REF ×(R I1 +R I2 ) / R I2 ……(1)

[0048] On the other hand, when the adjustment resistor R E1 When connected to the detection voltage adjustment terminal ADJ, the MOS transistor M2 is driven by the virtual short circuit of the differential amplifier AMP so that the MOS transistor M2 and the resistor R I3 The potential of the connection node N2 and the potential of the detection voltage adjustment terminal ADJ (R E1 ×I1) consistent.

[0049] Therefore, the detection voltage V DET ' becomes the potential shown in the following formula (2).

[0050] V DET '=V DET +(R I1 / R I3 )×R E1 ×I1……(2)

[0051] According to the above formula (2), by changing the adjustment resistor R E1 The resistance value can adjust the detection voltage V DET '.

[0052] On the other hand, in the above formula (2), it can be seen that if the resistance R I1 、R I3 If there is a deviation in the resistance value, the detection voltage V DET However, when the voltage detection circuit 10 is an IC, the resistor R I1 and RI3 Since it is an on-chip element, even if the resistance value varies due to the manufacturing process, it will also vary in the same way, so R, which is the resistance ratio, can be reduced. I1 / R I3 Therefore, by using a high-precision element as the adjustment resistor R connected to the detection voltage adjustment terminal ADJ E1 , can reduce the detection voltage V DET 'deviation.

[0053] In addition, in this embodiment, since the current flows through the adjustment resistor R E1 The current is based on the small current I1 of 1μA of the constant current source CS, so by connecting the adjustment resistor R E1 ,and Figure 3 Compared with the dark current of the conventional circuit, the dark current flowing out of the battery 20 can be suppressed.

[0054] Specifically, in Figure 3 In the existing circuit, the external resistor R E1 、R E2 When the resistance value is set to hundreds of kilo-ohms (kΩ), the current flowing through the resistor R E1 、R E2 The current is at the level of 100μA. Therefore, in the voltage detection circuit 10 of this embodiment, the current flowing through the external resistor R E1 The current is a small current I1 of 1 μA from the constant current source CS, and thus can be suppressed to about 1 / 100 of that of the conventional circuit.

[0055] On the other hand, in the voltage detection circuit 10 of the above embodiment, since the voltage-current conversion circuit 13 is added, the current consumed in the voltage detection circuit 10 is increased compared with the conventional circuit. However, in the current semiconductor integrated circuit manufacturing technology, the differential amplifier AMP can be designed so that the operating current of the differential amplifier AMP constituting the voltage-current conversion circuit 13 is less than 1μA. Therefore, even if it is combined with the current I1 (1μA) based on the constant current source CS, the increase is only about 2μA. Figure 3 Compared with the dark current of the existing circuit, the dark current flowing out of the battery 20 can be greatly suppressed as a whole.

[0056] As described above, in the voltage detection circuit 10 of the above embodiment, the detection voltage can be adjusted by providing the detection voltage adjustment circuit 14. Furthermore, even with the detection voltage adjustment function, the current flowing through the external detection voltage adjustment resistor is low, thereby suppressing increases in dark current and enabling long-term battery storage. Furthermore, since the effect of internal resistance variations on the detection voltage is suppressed, highly accurate voltage detection is possible. Furthermore, the voltage adjustment function can be simply disabled by simply wiring the detection voltage adjustment terminal ADJ to ground potential, offering the advantage of ease of use.

[0057] And, in Figure 3 In the prior art described above, adjusting the detection voltage without increasing dark current requires modifying the IC design to manufacture the voltage detection IC. This leads to a significant lead time for design changes and trial production. However, the voltage detection IC according to the above embodiment can shorten this lead time. Furthermore, the prior art requires preparing an IC for each detection voltage, which increases evaluation time and complicates inventory management. However, the voltage detection IC according to the above embodiment can reduce these drawbacks.

[0058] (Variation)

[0059] Next, use Figure 2 A modification of the voltage detection circuit 10 of the above embodiment will be described.

[0060] Figure 2 The voltage detection circuit 10' of the modified example shown omits the voltage-current conversion circuit 13 of the above embodiment, and is configured by a detection voltage setting constant current source CS and an adjustment resistor R connected to the detection voltage adjustment terminal ADJ. E1 The detection voltage adjustment circuit 14 is formed by adjusting the resistor R E1 The voltage after current-voltage conversion is used as the comparison voltage V TH It is applied to the inverting input terminal of the comparator (COMP) 12.

[0061] In the voltage detection circuit 10' of this modification, the detection voltage V DET ' becomes the potential expressed by the following formula (3).

[0062] V DET '=V REF =R E1 ×I1×(R I1 +R I2 ) / R I2 ……(3)

[0063] According to the above formula (3), by changing the external adjustment resistor R E1 The resistance value can adjust the detection voltage VDET '.

[0064] In addition, the voltage detection circuit 10' of this modification can be adjusted by the resistor R E1 Adjust the detection voltage V in a wide range DET However, unlike the voltage detection circuit of the above embodiment, it is necessary to connect a resistor R to the detection voltage adjustment terminal ADJ. E1 .

[0065] In the voltage detection circuit 10' of this modified example, Figure 1 Similarly, the voltage detection circuit 10 of the embodiment flows through the adjustment resistor R E1 The current is a small current I1 of 1μA based on the constant current source CS. Figure 3 Compared with the dark current of the conventional circuit, the dark current flowing from the battery 20 can be suppressed. In addition, the structure of the detection voltage adjustment circuit 14 is simple, and only a small number of components need to be added to the circuit, which has the advantage of suppressing an increase in the chip size of the IC.

[0066] The embodiments of the present invention have been described above, but the present invention is not limited to the above embodiments. Figure 1 In the voltage detection circuit 10 of the embodiment, a MOS transistor M2 and a resistor R are provided at the subsequent stage of the differential amplifier AMP of the voltage-current conversion circuit 13. I3 MOS transistor M2 and resistor R I3 Used as the output stage of the differential amplifier AMP.

[0067] In the above embodiment, the power supply voltages of the internal power supply voltage terminal Vcci connected to the constant current source CS, the voltage comparator circuit 12, and the differential amplifier AMP are not specifically mentioned. However, the battery voltage Vcci input to the voltage input terminal VS may be used as the power supply voltage of these circuits. BAT , or a regulator can be set internally and the voltage generated by the regulator can be used as the internal power supply voltage.

[0068] In addition, regarding Figure 1 In the voltage detection circuit 10 of the embodiment, the reference voltage V is input to the voltage comparison circuit 12. REF , can be configured to generate a reference voltage circuit inside the chip, or can be configured to input a reference voltage V to the IC REF External terminal to input externally generated voltage.

[0069] Furthermore, bipolar transistors may be used instead of MOS transistors M1 and M2. E1 Can be built-in, can be Figure 3Replacement is performed without changing the structure of external components.

[0070] Furthermore, in the above-described embodiment, the present invention is described as being applied to a battery voltage detection circuit that detects a battery voltage. However, the present invention can be applied to a voltage detection circuit that detects a voltage other than a battery voltage.

[0071] Description of Reference Signs

[0072] 10 voltage detection circuit, 11 voltage divider circuit, 12 voltage comparison circuit (comparator), 13 voltage-current conversion circuit, 14 detection voltage adjustment circuit, 20 battery, R E1 Adjustment resistor, ADJ detection voltage adjustment terminal, OUT detection signal output terminal.

Claims

1. A voltage detection circuit comprising: A voltage input terminal for inputting a voltage of a monitored object; a voltage divider circuit composed of a series resistor connected between the voltage input terminal and the constant voltage terminal; a voltage comparison circuit for comparing the voltage divided by the voltage divider circuit with a predetermined voltage; and an output terminal for outputting a comparison result of the voltage comparison circuit, The voltage detection circuit is formed as a semiconductor integrated circuit on a semiconductor substrate, detects whether the voltage input to the voltage input terminal exceeds or falls below a predetermined voltage value, and outputs a signal from the output terminal. It is characterized in that The voltage detection circuit has: Detection voltage adjustment terminal, which is connected to an external resistor; a voltage-current conversion circuit, which is provided between the detection voltage adjustment terminal and the voltage dividing circuit; and a constant current source connected between the internal power supply voltage terminal and the detection voltage adjustment terminal, The detection voltage of the voltage input terminal can be adjusted by the voltage-current conversion circuit extracting a current corresponding to the resistance value of the external resistor connected to the detection voltage adjustment terminal from the connection node of the series resistors of the voltage divider circuit.

2. The voltage detection circuit according to claim 1, wherein: The voltage-current conversion circuit comprises: a transistor and a resistor element in series, connected between a connection node of the series resistors of the voltage divider circuit and a ground point; and A differential amplifier circuit receives the voltage of the detection voltage adjustment terminal into a first input terminal, receives the potential of the connection node between the transistor and the resistor into a second input terminal, and applies the output of the differential amplifier circuit to a control terminal of the transistor.

3. The voltage detection circuit according to claim 1 or 2, characterized in that: The voltage to be monitored is the voltage of a battery.

4. The voltage detection circuit according to claim 3, wherein: The battery is a battery mounted on a vehicle.

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