Detection circuits and integrated circuits

Abstract

The present invention relates to a detection circuit and an integrated circuit for detecting the drift or open circuit of a first capacitor on a filtered second power supply terminal, the second power supply terminal being suitable for obtaining a power supply voltage from an unfiltered first power supply terminal via a first resistor, and being suitable for coupling to a reference potential terminal via the first capacitor to filter the power supply voltage. The detection circuit comprises a second resistor and a second capacitor connected in series, coupled between the first power supply terminal and the reference potential terminal, the second resistor and the second capacitor having the same time constant as the first resistor and the first capacitor; an emulated power supply terminal, connected between the second resistor and the second capacitor; and a comparator, coupled between the second power supply terminal and the emulated power supply terminal, suitable for detecting the voltage difference between the filtered power supply voltage of the second power supply terminal and the emulated power supply voltage of the emulated power supply terminal, the voltage difference indicating the drift degree or open circuit of the first capacitor. The present invention can detect the drift degree or open circuit of an external capacitor of an integrated circuit, and has the advantages of easy integration and low cost.

Description

Technical Field

[0001] The present invention relates to the field of integrated circuits, and in particular to a detection circuit for detecting the state of an external capacitor of an integrated circuit. Background Art

[0002] Figure 1 It is a schematic diagram of the structure of an integrated circuit. Figure 1 As shown, three pins of an integrated circuit (IC) chip 110 are shown, namely a ground pin 111, an unfiltered power pin 113 and a filtered power pin 112. A resistor R is connected between the unfiltered power pin 113 and the filtered power pin 112, and the resistor R belongs to the internal circuit of the integrated circuit chip 110. A capacitor C is connected between the filtered power pin 112 and the ground pin 111, and the capacitor C is an external capacitor and does not belong to the integrated circuit chip 110. On the one hand, the resistor R and the capacitor C can form a filter circuit to filter the signal of the unfiltered power pin 113 to obtain the signal of the filtered power pin 112; on the other hand, since the capacitor voltage drops slower than the power supply voltage, the capacitor C can play a role of undervoltage (Brownout) protection when the voltage of the power pin decreases, that is, a certain voltage reduction space (Brownout Margin) is provided for the power supply voltage.

[0003] In some cases, the connection between the capacitor C and the pin of the integrated circuit chip 110 may be disconnected, or the parameters of the capacitor C may drift when the ambient temperature, humidity, electric field, etc. change. In these cases, the ripple on the filtered power pin 112 may increase, thereby affecting the performance of the integrated circuit chip 110.

[0004] In the ISO 26262 "Road Vehicle Functional Safety" international standard, automotive integrated circuits are usually required to have the function of diagnosing short circuits or open circuits of their pins. In order to measure the open circuit state between the power pin and the external capacitor of the automotive integrated circuit chip, an AC (Alternating Current) current load can be added to the power pin and its AC ripple can be measured, but this method requires a fairly high current, and the generated AC ripple will have an adverse effect on the performance of the chip. Therefore, a more reliable and convenient method is needed to measure the open circuit state between the chip pin and the external capacitor and the parameter drift state of the external capacitor. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a detection circuit and an integrated circuit which can conveniently detect the state of an external capacitor of an integrated circuit.

[0006] The technical solution adopted by the present invention to solve the above-mentioned technical problems is a detection circuit for detecting the drift or open circuit of a first capacitor on a filtered second power supply terminal, wherein the second power supply terminal is suitable for obtaining a power supply voltage from an unfiltered first power supply terminal via a first resistor, and is suitable for coupling to a reference potential terminal via the first capacitor to filter the power supply voltage. The detection circuit comprises: a second resistor and a second capacitor connected in series, coupled between the first power supply terminal and the reference potential terminal, the second resistor and the second capacitor having the same time constant as the first resistor and the first capacitor; an imitation power supply terminal, connected between the second resistor and the second capacitor; and a comparator, coupled between the second power supply terminal and the imitation power supply terminal, suitable for detecting a voltage difference between the filtered power supply voltage of the second power supply terminal and the imitation power supply voltage of the imitation power supply terminal, wherein the voltage difference indicates the degree of drift or open circuit of the first capacitor.

[0007] In one embodiment of the present invention, the detection circuit also includes: a voltage divider circuit, coupled between the comparator and the second power supply terminal to provide the comparator with a divided voltage of the filtered power supply voltage; and a voltage divider resistor, coupled between the simulated power supply terminal and the reference potential terminal so that the simulated power supply voltage is the divided voltage of the unfiltered power supply voltage of the first power supply terminal.

[0008] In one embodiment of the present invention, the second resistor is a variable resistor.

[0009] In one embodiment of the present invention, the second resistor is pre-adjusted so that the second resistor and the second capacitor have the same time constant as the first resistor and the first capacitor.

[0010] In one embodiment of the present invention, the capacitance value of the second capacitor is an order of magnitude lower than the capacitance value of the first capacitor.

[0011] In one embodiment of the present invention, the detection circuit is integrated into an integrated circuit, and the first power supply terminal, the second power supply terminal and the reference potential terminal are terminals of the integrated circuit.

[0012] In an embodiment of the present invention, the detection circuit further includes a first switch for disconnecting the voltage divider circuit and a second switch for disconnecting the voltage divider resistor.

[0013] In order to solve the above technical problems, the present invention also proposes an integrated circuit, comprising: an unfiltered first power supply terminal; a filtered second power supply terminal, suitable for being coupled to the first power supply terminal via a first resistor, and being coupled to a reference potential terminal via a first capacitor; a second resistor and a second capacitor connected in series, coupled between the first power supply terminal and the reference potential terminal, the second resistor and the second capacitor having the same time constant as the first resistor and the first capacitor; an imitation power supply terminal, connected between the second resistor and the second capacitor; and a comparator, coupled to the second power supply terminal and the imitation power supply terminal, suitable for detecting the voltage difference between the filtered power supply voltage of the second power supply terminal and the imitation power supply voltage of the imitation power supply terminal.

[0014] In one embodiment of the present invention, the integrated circuit also includes: a voltage divider circuit, coupled between the comparator and the second power supply terminal to provide the comparator with a divided voltage of the filtered power supply voltage; and a voltage divider resistor, coupled between the simulated power supply terminal and the reference potential terminal to make the simulated power supply voltage the divided voltage of the unfiltered power supply voltage of the first power supply terminal.

[0015] In one embodiment of the present invention, the second resistor is a variable resistor.

[0016] In one embodiment of the present invention, the second resistor is pre-adjusted so that the second resistor and the second capacitor have the same time constant as the first resistor and the first capacitor.

[0017] In one embodiment of the present invention, the capacitance value of the second capacitor is an order of magnitude lower than the capacitance value of the first capacitor.

[0018] In one embodiment of the present invention, the device further comprises a first switch for disconnecting the voltage-dividing circuit and a second switch for disconnecting the voltage-dividing resistor.

[0019] In one embodiment of the present invention, the integrated circuit is an integrated circuit chip for an automobile.

[0020] In one embodiment of the present invention, the integrated circuit is a battery controller.

[0021] The present invention sets the internal RC circuit of the integrated circuit so that the time constant of the internal RC circuit is equal to the time constant of the external RC circuit including the external first capacitor C1, and by comparing the voltage of the internal capacitor and the external capacitor, the drift degree or open circuit state of the first capacitor C1 can be detected. The detection circuit and the integrated circuit of the present invention can detect the drift degree or open circuit of the external first capacitor C1 of the integrated circuit without adding additional external components, and have the beneficial effects of easy integration and low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to make the above-mentioned objects, features and advantages of the present invention more clearly understood, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, wherein:

[0023] Figure 1 It is a schematic diagram of the structure of an integrated circuit;

[0024] Figure 2 is corresponding to Figure 1 A schematic diagram of a circuit structure of a specific embodiment of the integrated circuit shown;

[0025] Figure 3A is a circuit diagram of a detection circuit according to Embodiment 1 of the present invention;

[0026] Figure 3B is a circuit diagram of a detection circuit according to a second embodiment of the present invention;

[0027] Figure 4 is a circuit diagram of a detection circuit according to a third embodiment of the present invention;

[0028] Figure 5 is a circuit diagram of a detection circuit according to a fourth embodiment of the present invention;

[0029] Figure 6 It is a schematic diagram of the change of the battery voltage and the change of the voltage and current of the internal RC circuit and the external RC circuit of the detection circuit of one embodiment of the present invention when the first capacitor is open-circuited;

[0030] Figure 7 It is a schematic diagram of changes in battery voltage ripple and voltage difference when a 70% drift occurs in the first capacitor C1 of a detection circuit according to an embodiment of the present invention;

[0031] Fig. 8A is a schematic diagram of the structure of an integrated circuit according to the first embodiment of the present invention;

[0032] Figure 8B is a schematic diagram of the structure of an integrated circuit according to a second embodiment of the present invention;

[0033] Figure 8C is a schematic diagram of the structure of an integrated circuit according to a third embodiment of the present invention;

[0034] Fig.8D It is a schematic diagram of the structure of an integrated circuit according to a fourth embodiment of the present invention. DETAILED DESCRIPTION

[0035] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for the description of the embodiments. Obviously, the drawings described below are only some examples or embodiments of the present application. For ordinary technicians in this field, the present application can also be applied to other similar scenarios based on these drawings without creative work. Unless it is obvious from the language environment or otherwise explained, the same reference numerals in the figures represent the same structure or operation.

[0036] As shown in this application and claims, unless the context clearly indicates an exception, the words "a", "an", "an" and / or "the" do not refer to the singular and may also include the plural. Generally speaking, the terms "include" and "comprise" only indicate the inclusion of the steps and elements that have been clearly identified, and these steps and elements do not constitute an exclusive list. The method or device may also include other steps or elements.

[0037] Unless otherwise specifically stated, the relative arrangement, numerical expressions and numerical values ​​of the parts and steps set forth in these embodiments do not limit the scope of the present application. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to the actual proportional relationship. The technology, method and equipment known to those of ordinary skill in the relevant field may not be discussed in detail, but in appropriate cases, the technology, method and equipment should be considered as a part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so that once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0038] It should be understood that when a component is referred to as being "on another component," "connected to another component," "coupled to another component," or "contacting another component," it may be directly on, connected to, coupled to, or contacting the other component, or there may be intervening components. In contrast, when a component is referred to as being "directly on another component," "directly connected to," "directly coupled to," or "directly contacting" another component, there are no intervening components. Similarly, when a first component is referred to as being "electrically in contact with" or "electrically coupled to" a second component, there is an electrical path between the first component and the second component that allows current to flow. The electrical path may include capacitors, coupled inductors, and / or other components that allow current to flow, even without direct contact between conductive components.

[0039] In addition, it should be noted that the use of words such as "first" and "second" to define components is only for the convenience of distinguishing the corresponding components. If not otherwise stated, the above words have no special meaning and cannot be understood as limiting the scope of protection of this application. In addition, although the terms used in this application are selected from well-known and commonly used terms, some terms mentioned in the specification of this application may be selected by the applicant at his or her discretion, and their detailed meanings are explained in the relevant parts of the description of this article. In addition, it is required to understand this application not only by the actual terms used, but also by the meaning implied by each term.

[0040] Figure 2 is corresponding to Figure 1 A schematic diagram of a circuit structure of a specific embodiment of an integrated circuit is shown. Figure 2 As shown, the circuit includes a first power supply terminal 210, a second power supply terminal 220, a first capacitor C1 and a first resistor R1, and also includes a reference potential terminal 230. The two ends of the first resistor R1 are connected to the first power supply terminal 210 and the second power supply terminal 220 respectively. The two ends of the first capacitor C1 are connected to the second power supply terminal 220 and the reference potential terminal 230 respectively. Figure 1 and Figure 2 As shown, Figure 2 The first power supply terminal 210, the second power supply terminal 220 and the first resistor R1 shown in FIG. 1 can all be included in Figure 1 The inside of the integrated circuit chip 110 is shown, wherein the first power supply terminal 210 is connected to the unfiltered power supply pin 113, the second power supply terminal 220 is connected to the filtered power supply pin 112, and the reference potential terminal 230 is connected to the ground pin 111.

[0041] Figure 1 The resistance R in the Figure 2 The first resistor R1 is connected between the unfiltered power pin 113 and the filtered power pin 112 inside the integrated circuit chip 110 . Figure 2 The first capacitor C1 shown in FIG. Figure 1 The capacitor C shown in FIG. 1 is outside the integrated circuit chip 110 . The first capacitor C1 is outside the integrated circuit chip 110 and connected between the filtered power pin 112 and the ground pin 111 .

[0042] Usually, in order to reduce costs and circuit size, the number of external electronic components of the integrated circuit is minimized. Figure 1 and Figure 2In the circuit structure shown, the first resistor R1 is disposed inside the integrated circuit chip 110. In some embodiments, the first resistor R1 may also be disposed outside the integrated circuit chip 110, connected between the unfiltered power pin 113 and the filtered power pin 112, and together with the first capacitor C1, form an RC circuit, which may function as a low-pass filter.

[0043] refer to Figure 2 As shown, the first power supply terminal 210 is usually connected to a power supply, which can be, for example, a battery. Therefore, the voltage detected at the first power supply terminal 210 is the power supply voltage, and is the unfiltered power supply voltage Vbat1. The filter circuit composed of the first resistor R1 located inside the integrated circuit chip 110 and the first capacitor C1 located outside the integrated circuit chip 110 filters the unfiltered power supply voltage Vbat1 of the first power supply terminal 210, and obtains the filtered power supply voltage Vbat2 at the second power supply terminal 220.

[0044] refer to Figure 2 As shown, the reference potential Vss can be detected at the reference potential terminal 230. In the detection circuit, the reference potential terminal 230 can further include an analog reference potential terminal 231 and a digital reference potential terminal 232. Accordingly, the analog reference potential Vssa can be detected at the analog reference potential terminal 231, and the digital reference potential Vssd can be detected at the digital reference potential terminal 232.

[0045] In some embodiments, an electrostatic discharge (ESD) protection circuit 201 formed by two mutually reversed diodes connected in parallel is also connected between the first power supply terminal 210 and the second power supply terminal 220. The diodes here are called ESD diodes. When electrostatic discharge occurs, the electrostatic peak voltage in the circuit can be clamped within a specified range by the ESD diodes in the ESD protection circuit 201, thereby protecting the stable operation of the chip. In some embodiments, an ESD protection circuit 201 is also connected between the analog reference potential terminal 231 and the digital reference potential terminal 232, which also plays a role in electrostatic discharge protection.

[0046] exist Figure 2 The circuit shown may also include an internal sensitive circuit. The internal sensitive circuit (not shown) may be connected between the filtered second power supply terminal 220 and the reference potential terminal 230. The function of the internal sensitive circuit is to reduce the ripple interference on the second power supply terminal 220 and provide a longer undervoltage protection time. Specifically, when the circuit is undervoltage, the internal sensitive circuit can make the voltage on the second power supply terminal 220 drop slower than the voltage on the first power supply terminal 210.

[0047] Generally, in order to measure the connection between the first capacitor C1 and the integrated circuit chip 110, that is, to detect whether the first capacitor C1 is open or the parameters are drifting, it is necessary to measure the current flowing through the first capacitor C1. However, according to the existing measurement technology, the current sensor used for current measurement needs to be connected to the power supply terminal, that is, the current sensor needs to be able to withstand a sufficiently high voltage. In addition, it is difficult to obtain an accurate current value without affecting other circuit elements.

[0048] Figure 3A Schematic diagram of a detection circuit according to Embodiment 1 of the present invention. Figure 3A As shown, the detection circuit includes Figure 2 The integrated circuit structure shown in FIG. 1 further includes a second resistor R2, a second capacitor C2, a simulated power supply terminal 310 and a comparator 320. Figure 2 The ESD diodes in the Figure 3A The embodiment shown does not include Figure 2 The electrostatic discharge protection circuit 201 in FIG. Figure 3A In the illustrated embodiment, the reference potential terminal 230 is shown as a single terminal, indicating that the reference potential terminal 230 is not divided into an analog reference potential terminal and a digital reference potential terminal.

[0049] exist Figure 3A In the embodiment shown, the second resistor R2 and the second capacitor C2 are connected in series and coupled between the first power supply terminal 210 and the reference potential terminal 230. Figure 3A As shown, one end of the second capacitor C2 is connected to one end of the second resistor R2, and the other end of the second capacitor C2 is connected to the reference potential terminal 230. The other end of the second resistor R2 is connected to the first resistor R1 and also connected to the first power supply terminal 210.

[0050] Figure 3B is a circuit diagram of a detection circuit according to Embodiment 2 of the present invention. Figure 3A Compared to the embodiment shown, Figure 3B In the embodiment shown, the Figure 2 The electrostatic discharge protection circuit 201 is composed of an ESD diode, and the reference potential terminal 230 is further divided into an analog reference potential terminal 231 and a digital reference potential terminal 232. One end of the second capacitor C2 is connected to one end of the second resistor R2, and the other end of the second capacitor C2 is connected to the analog reference potential terminal 231.

[0051] In some embodiments, the detection circuit is integrated into an integrated circuit, and the first power supply terminal 210, the second power supply terminal 220 and the reference potential terminal 230 are terminals of the integrated circuit. Figures 1 to 3BAs shown, the detection circuit can be integrated into the integrated circuit chip 110, and the first power terminal 210 is equivalent to the unfiltered power pin 113, the second power terminal 220 is equivalent to the filtered power pin 112, and the reference potential terminal 230 is equivalent to the ground pin 111.

[0052] The first resistor R1 and the first capacitor C1 form a first RC circuit, and the second resistor R2 and the second capacitor C2 form a second RC circuit. In an embodiment of the present invention, the first time constant τ1 of the first RC circuit and the second time constant τ2 of the second RC circuit are equal. For example, in a specific embodiment, R1 = 10Ohm, C1 = 10μF, R2 = 1MOhm, C2 = 100pF, then

[0053] τ1=R1*C1=100μs;

[0054] τ2=R2*C2=100μs;

[0055] τ1=τ2.

[0056] The pseudo power supply terminal 310 is located between the second resistor R2 and the second capacitor C2 and is connected to an input terminal 321 of the comparator 320 . The voltage signal of the pseudo power supply terminal 310 , ie, the pseudo power supply voltage V0 , is used as an input of the comparator 320 .

[0057] The two input terminals 321 and 322 of the comparator 320 are coupled to the imitation power terminal 310 and the second power terminal 220 respectively, and are suitable for detecting the voltage difference V_diff between the filtered power voltage Vbat2 of the second power terminal 220 and the imitation power voltage V0 of the imitation power terminal 310. The voltage difference V_diff can be used to indicate the drift degree or open circuit of the first capacitor C1. That is,

[0058] V_diff=|Vbat2-V0|

[0059] Among them, ||| means taking the absolute value.

[0060] Usually, the two inputs of the comparator 320 are analog voltage signals, and its output can be an analog voltage signal or a digital signal. The comparator 320 can compare the input voltages on the two input terminals 321 and 322, and perform a subtraction operation on the two input voltages to obtain a voltage difference V_diff. The output terminal 323 of the comparator 320 can directly output the voltage difference V_diff, or a detection threshold V_th can be set for the comparator 320 as needed. The comparator 320 determines the result to be outputted by its output terminal 323 according to the magnitude relationship between the voltage difference V_diff and the detection threshold V_th. For example, when the voltage difference V_diff is greater than the detection threshold V_th, the output terminal 323 of the comparator 320 outputs 1, and when the voltage difference V_diff is less than the detection threshold V_th, the output terminal 323 of the comparator 320 outputs 0. Therefore, the magnitude and difference of the two input voltages on its input terminals 321 and 322 can be determined according to the output of the comparator 323.

[0061] In some embodiments, in combination Figures 1 to 3B As shown, in Figure 3A and 3B The second resistor R2, the second capacitor C2 and the comparator 320 shown in FIG. 1 are all located inside the integrated circuit chip 110. Figure 3A and 3B In the circuit structure shown, except for the first capacitor C1, all other electronic components belong to the internal circuit of the integrated circuit chip 110. The output terminal 323 of the comparator 320 can be connected to an external component through a pin of the integrated circuit chip 110, or can be inside the integrated circuit chip 110.

[0062] In some places in this specification, the first RC circuit composed of the first resistor R1 and the first capacitor C1 is referred to as an external RC circuit, and the second RC circuit composed of the second resistor R2 and the second capacitor C2 is referred to as an internal RC circuit. The internal or external here refers to being inside or outside the integrated circuit chip 110. It should be noted that the first resistor R1 in the external RC circuit can belong to the internal circuit of the integrated circuit chip 110.

[0063] In some embodiments, the capacitance value of the second capacitor C2 in the internal RC circuit is an order of magnitude lower than the capacitance value of the first capacitor C1 in the external RC circuit. This is because, on the one hand, the internal RC circuit does not need to transfer power, so a large capacitance value is not required; on the other hand, a capacitor with a small capacitance value also has a smaller volume, which can reduce the size of the integrated circuit chip 110.

[0064] exist Figure 3A and 3BIn the illustrated embodiment, each electronic component including capacitors, resistors, diodes and comparators can be electronic components commonly used in the art, and these electronic components are suitable for integration in an integrated circuit chip.

[0065] according to Figure 3A and 3B In the embodiment shown, when the first capacitor C1 is normally connected between the second power supply terminal 220 and the reference potential terminal 230, since the time constant of the internal RC circuit formed inside the integrated circuit chip 110 is equal to the time constant of the external RC circuit, when the input voltages of the internal RC circuit and the external RC circuit are equal, the voltages on the second capacitor C2 and the first capacitor C1 should also be equal, and accordingly, Vbat2=V0, so that the input voltages on the two input terminals 321 and 322 of the comparator 320 are equal. Accordingly, the voltage difference V_diff is zero, which further affects the output result of the output terminal 323 of the comparator 323. For example, for the comparator 320 whose output terminal 323 directly outputs the voltage difference V_diff, the output result of the output terminal 323 is also zero.

[0066] When the parameters of the first capacitor C1 drift or open circuit occurs, the voltage on the first capacitor C1 is not equal to the voltage on the second capacitor C2, and accordingly, Vbat2≠V0, then V_diff≠0. For the comparator 320 that can set the detection threshold V_th, a detection threshold V_th can be set as needed, and the voltage difference V_diff and the detection threshold V_th are compared to determine the degree of drift or open circuit of the first capacitor C1. For example, a first detection threshold V_th1 is set, and if V_diff>V_th1, it is determined that the first capacitor C1 has drifted, and the greater the difference between V_diff and V_th1, the more serious the drift degree. For example, a second detection threshold V_th2 is set, and if V_diff>V_th2, it is determined that the first capacitor C1 has an open circuit.

[0067] Therefore, it is possible to determine whether the first capacitor C1 is open circuited or drifting, and the degree of drift, etc. according to the output result of the comparator 320 .

[0068] Figure 3A and 3B The technical effect of the first and second embodiments shown is that there is no need to directly measure the current of the first capacitor C1. Instead, an internal RC circuit is formed inside the integrated circuit chip 110 so that the internal RC circuit and the external RC circuit including the first capacitor C1 have the same time constant. By comparing the voltage of the second capacitor C2 of the internal RC circuit with the voltage of the first capacitor C1 of the external RC circuit, the drift degree or open circuit of the first capacitor C1 can be determined.

[0069] In practical applications, the first power supply terminal 210 and the second power supply terminal 220 are connected to a power supply, and accordingly, the voltage applied to the first capacitor C1 is equal to the power supply voltage, which means that the voltage on the second capacitor C2 inside the integrated circuit chip 110 is also equal to the power supply voltage. Figure 3A and 3B For the first and second embodiments shown in the figure, on the one hand, if the power supply voltage is greater than the maximum operating voltage of the total integrated capacitor in the integrated circuit, the second capacitor C2 needs to have a high rated voltage; on the other hand, the capacitor with a high rated voltage is larger in volume, which will increase the volume of the integrated circuit chip 110. In view of this problem, the present invention further proposes Figure 4 The embodiment shown.

[0070] Figure 4 It is a circuit diagram of a detection circuit according to Embodiment 3 of the present invention. Figure 4 The third embodiment shown in Figure 3B A voltage divider circuit and a voltage divider resistor are added to the structure of the detection circuit shown. The voltage divider circuit is coupled between the comparator 320 and the second power supply terminal 220 to provide the comparator 320 with a voltage divider of the filtered power supply voltage Vbat2; the voltage divider resistor is coupled between the dummy power supply terminal 310 and the reference potential terminal 230 to make the dummy power supply voltage V0 the voltage divider of the unfiltered power supply voltage Vbat1 of the first power supply terminal 210. Specifically, the reference potential terminal 230 is connected to the dummy power supply voltage V0. Figure 4 As shown, the voltage divider circuit includes a third resistor R3 and a fourth resistor R4. The third resistor R3 and the fourth resistor R4 are connected in series and connected between the second power supply terminal 220 and the reference potential terminal 230. One end of the third resistor R3 is connected to the second power supply terminal 220, and the other end is connected to one end of the fourth resistor R4 and an input terminal 322 of the comparator 320; one end of the fourth resistor R4 is connected to one end of the third resistor R3 and an input terminal 322 of the comparator 320, and the other end is connected to the reference potential terminal 230. Figure 4 As shown, the voltage divider resistor includes a fifth resistor R5, one end of which is connected to one end of the second resistor R2 and the pseudo power supply terminal 310, and the other end is connected to the reference potential terminal 230. Further, one end of the fifth resistor R5 is connected to an input terminal 321 of the comparator 320 through the pseudo power supply terminal 310.

[0071] Understandably, according to Figure 4In the embodiment shown, the voltages input to the two input terminals 321 and 322 of the comparator are respectively divided by the voltage divider circuit and the voltage divider resistor. Among them, the voltage divider circuit (the third resistor R3 and the fourth resistor R4) divides the voltage on the first capacitor C1, which can reduce the voltage on the first capacitor C1; the voltage divider resistor (the fifth resistor R5) divides the voltage on the second capacitor C2, which can reduce the voltage on the second capacitor C2. The present invention does not limit the degree of voltage division to be performed by the voltage divider circuit and the voltage divider resistor, and the desired voltage division result can be controlled by setting specific resistance values ​​and capacitance values.

[0072] In these embodiments, the first RC circuit (external RC circuit) includes a first capacitor C1, a first resistor R1, a third resistor R3 and a fourth resistor R4; the second RC circuit (internal RC circuit) includes a second capacitor C2, a second resistor R2 and a fifth resistor R5. By setting the specific values ​​of the electronic components in the first RC circuit and the second RC circuit according to the results of theoretical calculation, the time constant of the second RC circuit can be equal to the time constant of the first RC circuit.

[0073] For example, in a specific embodiment, when the voltage divider circuit and the voltage divider resistor are not added, R1=10Ohm, C1=10μF, R2=1MOhm, C2=100pF. After the voltage divider circuit and the voltage divider resistor are added, R3=1MOhm, R4=1MOhm, R5=1MOhm, and C2=200pF are adjusted. According to these settings, the time constant of the first RC circuit can be equal to the time constant of the second RC circuit, and the voltages of the two input terminals 321 and 322 input to the comparator 320 are reduced to half of the original voltages.

[0074] according to Figure 4 The embodiment shown can not only reduce the voltage to be borne by the first capacitor C1 and the second capacitor C2, but the voltage divider circuit and the voltage divider resistor also provide a second level of ESD protection for the circuit, so that a low input voltage transistor can be used at the input end of the comparator 320. In order to avoid leakage current caused by the voltage divider circuit and the voltage divider resistor, the resistance values ​​are set relatively high, for example, MOhm-level resistors are used.

[0075] In some embodiments, the detection circuit of the present invention further includes a first switch S1 for disconnecting the voltage divider circuit and a second switch S2 for disconnecting the voltage divider resistor. The first switch S1 can be connected in series with the voltage divider circuit, and the second switch S2 can be connected in series with the voltage divider resistor. In these embodiments, when the detection circuit of the present invention needs to be connected, the first switch S1 and the second switch S2 can be kept closed, and when the voltage divider circuit and the voltage divider resistor are not needed, the first switch S1 and the second switch S2 are opened, thereby cutting off the connection between the voltage divider circuit and the voltage divider resistor and other circuits, thereby avoiding the generation of leakage current.

[0076] Resistors and capacitors inside an integrated circuit typically have an error or tolerance of about ±30%, while capacitors outside the integrated circuit have an error or tolerance of about ±50%. In other words, there is a certain error between the actual resistance and capacitance values of the resistors and capacitors and their nominal resistance and capacitance values. Therefore, in order to make the time constant of the internal RC circuit actually equal to the time constant of the external RC circuit, it is necessary to adjust the resistors and / or capacitors therein. In some embodiments, variable capacitors and / or variable resistors may be employed in the internal RC circuit. However, since the volume of the variable capacitor is relatively large, in the embodiments of the present invention, variable resistors are used.

[0077] For Figure 3A 、 3B and Figure 4 the embodiments of the detection circuit shown, the second resistor R2 therein may be a variable resistor. In these embodiments, the second resistor R2 may be pre-adjusted so that the second resistor R2 and the second capacitor C2 have the same time constant as the first resistor R1 and the first capacitor C1. Specifically, the time T1 and T2 taken for the voltage Vc1 on the first capacitor C1 and the voltage Vc2 on the second capacitor C2 to reach a certain preset voltage may be measured respectively. If the voltage Vc2 of the second capacitor C2 reaches the preset voltage earlier than the voltage Vc1 of the first capacitor C1, that is, T2 < T1, it indicates that the time constant of the internal RC circuit is less than the time constant of the external RC circuit. And the size of the second resistor R2 may be adjusted according to the relationship between T1 and T2 so that the time constant of the internal RC circuit is equal to the time constant of the external RC circuit. It can be understood that the method for adjusting the time constant here is only for illustration, and other methods may also be adopted to adjust the size of the second resistor R2 so that the time constant of the internal RC circuit is equal to the time constant of the external RC circuit.

[0078] In some embodiments, the fifth resistor R5 and / or the second resistor R2 in the internal RC circuit shown in Figure 4 may be variable resistors.

[0079] Figure 5 is a schematic circuit diagram of the detection circuit according to Embodiment 4 of the present invention. Compared with the embodiment shown in Figure 4 , Figure 5The embodiment shown adds a sixth resistor R6 to the internal RC circuit. One end of the sixth resistor R6 is simultaneously connected to one end of the second resistor R2 and one end of the fifth resistor R5, and the other end of the sixth resistor R6 is connected to one end of the second capacitor C2 and the pseudo power supply terminal 310. In this embodiment, the second resistor R2, the fifth resistor R5, the sixth resistor R6 and the second capacitor C2 together form an internal RC circuit. Therefore, the setting of each resistance value and capacitance value should make the time constant of the internal RC circuit equal to the time constant of the external RC circuit.

[0080] In some embodiments, the sixth resistor R6 may be a variable resistor. For example, when R1=10Ohm, C1=10μF, R3=1MOhm, R4=1MOhm, C2=100pF, R2=700kOhm, R5=700kOhm, R6=0-300kOhm are set. The resistance value of the sixth resistor R6 can be adjusted between 0 and 300kOhm. Figure 5 The embodiment shown can also be used in the case where the actual capacitance value of the first capacitor C1 and / or the second capacitor C2 is not equal to the nominal value. According to the adjustment method described above, by adjusting the resistance value of the sixth resistor R6, the time constant of the internal RC circuit is actually equal to the time constant of the external RC circuit.

[0081] Understandably, Figure 3B Similar to the embodiment shown, in other embodiments, Figure 4 , 5 In the illustrated embodiment, an electrostatic discharge protection circuit 201 is added, and the reference potential terminal 230 is divided into an analog reference potential terminal and a digital reference potential terminal, so that one end of the second capacitor C2 connected to the reference potential terminal 230 is connected to the analog reference potential terminal 231 .

[0082] exist Figures 3A to 5 In the embodiment of the detection circuit shown, a detection threshold V_th can be set for the comparator 320, and the comparator 320 compares the voltage difference V_diff input to its two input terminals 321 and 322 with the detection threshold V_th, so as to determine the drift degree or open circuit of the first capacitor C1. Those skilled in the art can set the detection threshold V_th as needed. A method for determining the detection threshold V_th is described below by taking an integrated circuit for automotive battery management as an example.

[0083] For the integrated circuit used for automobile battery management, it includes all the electronic components in the detection circuit mentioned above, and the detection circuit can detect the drift degree or open circuit of the first capacitor externally connected to the integrated circuit. It can be understood that the integrated circuit can also be used in other fields other than automobiles that require battery management.

[0084] Figure 6 This is a schematic diagram of the change of the battery voltage and the voltage and current change of the internal RC circuit and the external RC circuit when the first capacitor is open-circuited in the detection circuit of an embodiment of the present invention. It should be noted that Figure 6 The voltage and current shown are based on Figure 4 The detection circuit of the embodiment shown. Figure 6 As shown, the horizontal axis represents time in ms; the left vertical axis represents voltage in mV or V; and the right vertical axis represents current in nA. Figure 6 It mainly includes two parts, the upper part shows the curves of the voltage difference V_diff on the two input terminals 321 and 322 of the comparator 320 and the current I_C2 on the second capacitor C2 changing with time; the lower part shows the curve of the car battery voltage changing with time.

[0085] For a car battery, the supply voltage provided to the car battery changes with a certain slope as the drive current increases. Assuming that the supply voltage is V, the rate of change of the voltage dV / dt is a constant as the drive current increases. The rate of change dV / dt is 0.4V / ms under normal circumstances and can reach 5V / ms under extreme circumstances. Figure 4 As shown, the supply voltage V is usually provided to the detection circuit through the first power supply terminal 210, that is, Vbat1 = V, then correspondingly, dVbat1 / dt = dV / dt. Figure 6 As shown in the lower part of the figure, by measuring the unfiltered power supply voltage Vbat1 of the first power supply terminal 210, a curve of Vbat1 changing with time is obtained. The unfiltered power supply voltage Vbat1 first decreases at a rate of 0.4V / ms, from about 5.4V at 0ms to about 1.7V, and then increases at a rate of 0.4V / ms. At nearly 20ms, Vbat1 rises to the original voltage of about 5.4V.

[0086] Figure 6 The upper and lower parts of the voltage V_diff share the same horizontal axis. Therefore, during the decrease of the unfiltered power supply voltage Vbat1, the voltage difference V_diff obtained by the comparator 320 is about -20mV, and the absolute value of the voltage difference V_diff is 20mV. Figure 6The result shown is measured when the first capacitor C1 is open circuited. Therefore, in order to measure the drift degree or open circuit of the first capacitor C1, it is necessary to set the detection threshold V_th of the comparator 320 to be less than 20mV. When there is a 30% error in the capacitance value of the first capacitor C1 and / or the second capacitor C2, the measured voltage difference V_diff may differ from the actual voltage difference by about 6mV. In this case, the drift degree or open circuit of the first capacitor C1 can still be detected by setting a suitable detection threshold V_th. In some embodiments, the comparator 320 is a self-zeroing comparator.

[0087] Figure 6 The upper part of FIG. 1 also shows a curve of the current I_C2 on the second capacitor C2 changing with time. When the unfiltered power supply voltage Vbat1 starts to rise at a rate of 0.4 V / ms from about 11 ms, the current I_C2 is basically maintained at about 20 nA.

[0088] In some embodiments, the detection threshold V_th can be determined by analyzing the ripple of the battery voltage. For the integrated circuit of the automotive battery management, the reverse conversion flow will cause high-frequency ripple interference, and the frequency of the ripple interference is related to the driving speed of the car. Most of the harmonics in the ripple are between 1.6kHz and 15kHz. For each battery cell, the peak-to-peak value of the ripple can reach 0.5Vpp.

[0089] Figure 7 It is a schematic diagram of changes in battery voltage ripple and voltage difference when a 70% drift occurs in the first capacitor C1 of a detection circuit according to an embodiment of the present invention. Figure 7 The shown is also based on Figure 4 The detection circuit of the embodiment shown. Figure 7 As shown, the horizontal axis represents time in ms; the left vertical axis represents voltage in mV or V. Figure 7 It mainly includes two parts, the upper part shows the curve of the change of the car battery voltage Vbat1 over time; the lower part shows the curve of the change of the voltage difference V_diff on the two input terminals 321 and 322 of the comparator 320 over time when the actual value of the first capacitor C1 is 70% of the nominal value. Figure 7 In the upper part, it can be seen that the battery voltage has obvious ripples due to the reverse conversion flow.

[0090] refer to Figure 7 As shown in FIG. 1 , the maximum voltage difference V_diff can reach about 20 mV. Therefore, the detection threshold V_th can be set to 10 mV. In this way, when the voltage difference V_diff>V_th is detected, it can be indicated that the first capacitor C1 has drifted. When the first capacitor C1 is completely disconnected, Figure 7In the case shown, the voltage difference V_diff can reach up to 160mV.

[0091] according to Figure 7 As shown, by setting a reasonable detection threshold V_th, such as 10mV, the ripple generated by the car inverter can be used to detect the open circuit or drift degree of the first capacitor C1, and no additional current generator is required. Usually, when the car is driving, braking or charging, a more obvious ripple will be generated in the car battery voltage Vbat1. When the car stops running or runs at a low load, the ripple amplitude in the car battery voltage Vbat1 is low, and the voltage difference V_diff is too small to be detected. However, in this case, the drift or open circuit of the first capacitor C1 has little effect on the precise control of the circuit, so it can be ignored.

[0092] The detection circuit of the present invention can detect the drift degree or open circuit of the first capacitor C1 connected to the integrated circuit without adding any additional external components, and has the beneficial effects of easy integration and low cost. Fig. 8A Schematic diagram of the structure of the integrated circuit of the first embodiment of the present invention. Fig. 8A As shown, the integrated circuit 800 includes an unfiltered first power supply terminal 210; a filtered second power supply terminal 220, suitable for being coupled to the first power supply terminal 210 via a first resistor R1, and coupled to the reference potential terminal 230 via a first capacitor C1; a second resistor R2 and a second capacitor C2 connected in series, coupled between the first power supply terminal 210 and the reference potential terminal 230, the second resistor R2 and the second capacitor C2 having the same time constant as the first resistor R1 and the first capacitor C1; an imitation power supply terminal 310, connected between the second resistor R2 and the second capacitor C2; a comparator 320, coupled to the second power supply terminal 320 and the imitation power supply terminal 310, suitable for detecting the voltage difference between the filtered power supply voltage Vbat2 of the second power supply terminal 220 and the imitation power supply voltage V0 of the imitation power supply terminal 310.

[0093] It should be noted that Fig. 8A In the embodiment shown, the first capacitor C1 is externally connected to the integrated circuit 800. The first RC circuit formed by the first resistor R1 and the first capacitor C1 is called an external RC circuit, and the second RC circuit formed by the second resistor R2 and the second capacitor C2 is called an internal RC circuit.

[0094] Combination Figure 3A and Fig. 8A As shown, Fig. 8A The integrated circuit 800 shown includes Figure 3A The detection circuit shown in this manual is Figure 3A The detection circuit description sections shown are applicable to Fig. 8A The integrated circuit shown.

[0095] Figure 8B Schematic diagram of the structure of the integrated circuit of the second embodiment of the present invention. Fig. 8A Compared to the embodiment shown, Figure 8B In the embodiment shown, the Figure 2 The electrostatic discharge protection circuit 201 is composed of an ESD diode, and the reference potential terminal 230 is further divided into an analog reference potential terminal 231 and a digital reference potential terminal 232. One end of the second capacitor C2 is connected to one end of the second resistor R2, and the other end of the second capacitor C2 is connected to the analog reference potential terminal 231.

[0096] Combination Figure 3B and Figure 8B As shown, Figure 8B The integrated circuit 810 shown includes Figure 3B The detection circuit shown in this manual is Figure 3B The detection circuit description sections shown are applicable to Figure 8B The integrated circuit shown.

[0097] Figure 8C Schematic diagram of the structure of the integrated circuit of the third embodiment of the present invention. Figure 8C As shown, the integrated circuit 820 of this embodiment is Fig. 8A On the basis of the embodiment shown, a voltage divider circuit and a voltage divider resistor are added. The voltage divider circuit is coupled between the comparator 230 and the second power supply terminal 220 to provide the comparator 230 with a divided voltage of the filtered power supply voltage Vbat2; and the voltage divider resistor is coupled between the dummy power supply terminal 310 and the reference potential terminal 230 to make the dummy power supply voltage V0 the divided voltage of the unfiltered power supply voltage Vbat1 of the first power supply terminal 210. Figure 4 and Figure 8C As shown, Figure 8C The integrated circuit 820 shown includes Figure 4 The detection circuit shown in this manual is Figure 4 The detection circuit description sections shown are applicable to Figure 8C The integrated circuit shown.

[0098] In some embodiments, Figures 8A-8C The second resistor R2 is a variable resistor. In these embodiments, the second resistor R2 is pre-adjusted to make the second resistor R2 and the second capacitor C2 have the same time constant as the first resistor R1 and the first capacitor C1.

[0099] In some embodiments, the capacitance of the second capacitor C2 is an order of magnitude lower than the capacitance of the first capacitor C1 .

[0100] exist Figure 8CThe illustrated embodiment further includes a first switch S1 for disconnecting the voltage-dividing circuit and a second switch S2 for disconnecting the voltage-dividing resistor.

[0101] Fig.8D Schematic diagram of the structure of the integrated circuit of the fourth embodiment of the present invention. Figure 8C Compared to the embodiment shown, Fig.8D The embodiment shown adds a sixth resistor R6 to the internal RC circuit. Figure 5 and Fig.8D As shown, Fig.8D The integrated circuit 830 shown includes Figure 5 The detection circuit shown in this manual is therefore Figure 5 The detection circuit description sections shown are applicable to Fig.8D The integrated circuit shown.

[0102] Understandably, Figures 8A-8D The embodiment of the integrated circuit shown corresponds to Figure 3A-Figure 5 The detection circuit shown in FIG. Figure 8C and 8D An electrostatic discharge protection circuit 201 is added, and the reference potential terminal 230 is divided into an analog reference potential terminal and a digital reference potential terminal, so that the end of the second capacitor C2 connected to the reference potential terminal 230 is connected to the analog reference potential terminal 231.

[0103] In some embodiments, Figures 8A-8D The integrated circuit shown is a battery controller.

[0104] according to Figures 8A-8D The integrated circuit shown can detect the drift degree or open circuit of the external first capacitor C1. For details on how to set the detection threshold V_th for the comparator 320 and how to use the obtained voltage difference V_diff to determine the state of the first capacitor C1, please refer to the description of the detection circuit in the previous text of the specification and the corresponding drawings.

[0105] It can be understood that the detection circuit and integrated circuit of the present invention can be used in any circuit requiring functional safety assurance, and can detect the drift degree or open circuit of the external capacitor of the integrated circuit, and is not limited to the automotive battery management integrated circuit in the specific embodiment of the present invention.

[0106] Although the present invention has been described with reference to the current specific embodiments, a person skilled in the art should recognize that the above embodiments are only used to illustrate the present invention, and various equivalent changes or substitutions may be made without departing from the spirit of the present invention. Therefore, any changes or modifications to the above embodiments within the spirit of the present invention shall fall within the scope of the claims of this application.

[0107] At the same time, the present application uses specific words to describe the embodiments of the present application. For example, "one embodiment", "an embodiment", and / or "some embodiments" refer to a certain feature, structure or characteristic related to at least one embodiment of the present application. Therefore, it should be emphasized and noted that "one embodiment" or "an embodiment" or "an alternative embodiment" mentioned twice or more in different positions in this specification does not necessarily refer to the same embodiment. In addition, some features, structures or characteristics in one or more embodiments of the present application can be appropriately combined.

Claims

1. A detection circuit for detecting drift or open circuit of a first capacitor on a filtered second power supply terminal, the second power supply terminal being adapted to obtain a power supply voltage from an unfiltered first power supply terminal via a first resistor, and being adapted to be coupled to a reference potential terminal via the first capacitor to filter the power supply voltage, the detection circuit comprising: A second resistor and a second capacitor connected in series, coupled between the first power supply terminal and the reference potential terminal, the second resistor and the second capacitor having the same time constant as the first resistor and the first capacitor; A pseudo power supply terminal connected between the second resistor and the second capacitor; as well as A comparator is coupled to the second power supply terminal and the imitation power supply terminal, and is suitable for detecting a voltage difference between a filtered power supply voltage at the second power supply terminal and an imitation power supply voltage at the imitation power supply terminal, wherein the voltage difference indicates a drift degree or an open circuit of the first capacitor.

2. The detection circuit according to claim 1, characterized in that: Also includes: a voltage divider circuit coupled between the comparator and the second power supply terminal to provide a divided voltage of the filtered power supply voltage to the comparator; as well as The voltage dividing resistor is coupled between the pseudo power supply terminal and the reference potential terminal so that the pseudo power supply voltage is a divided voltage of the unfiltered power supply voltage of the first power supply terminal.

3. The detection circuit according to claim 1 or 2, characterized in that: The second resistor is a variable resistor.

4. The detection circuit according to claim 3, characterized in that: The second resistor is pre-adjusted so that the second resistor and the second capacitor have the same time constant as the first resistor and the first capacitor.

5. The detection circuit according to claim 1, characterized in that: The capacitance value of the second capacitor is an order of magnitude lower than the capacitance value of the first capacitor.

6. The detection circuit according to claim 1, characterized in that: The detection circuit is integrated in an integrated circuit, and the first power supply terminal, the second power supply terminal and the reference potential terminal are terminals of the integrated circuit.

7. The detection circuit according to claim 2, characterized in that: It also includes a first switch for disconnecting the voltage-dividing circuit and a second switch for disconnecting the voltage-dividing resistor.

8. An integrated circuit comprising: an unfiltered first power supply terminal; The filtered second power supply terminal is adapted to be coupled to the first power supply terminal via a first resistor and coupled to a reference potential terminal via a first capacitor; A second resistor and a second capacitor connected in series, coupled between the first power supply terminal and the reference potential terminal, the second resistor and the second capacitor having the same time constant as the first resistor and the first capacitor; A pseudo power supply terminal connected between the second resistor and the second capacitor; as well as The comparator is coupled to the second power terminal and the imitation power terminal, and is adapted to detect a voltage difference between a filtered power voltage at the second power terminal and an imitation power voltage at the imitation power terminal.

9. The integrated circuit according to claim 8, characterized in that Also includes: a voltage divider circuit coupled between the comparator and the second power supply terminal to provide a divided voltage of the filtered power supply voltage to the comparator; as well as The voltage dividing resistor is coupled between the pseudo power supply terminal and the reference potential terminal so that the pseudo power supply voltage is a divided voltage of the unfiltered power supply voltage of the first power supply terminal.

10. The integrated circuit according to claim 8 or 9, characterized in that The second resistor is a variable resistor.

11. The integrated circuit according to claim 10, wherein: The second resistor is pre-adjusted so that the second resistor and the second capacitor have the same time constant as the first resistor and the first capacitor.

12. The integrated circuit of claim 8, wherein: The capacitance value of the second capacitor is an order of magnitude lower than the capacitance value of the first capacitor.

13. The integrated circuit of claim 9, wherein: It also includes a first switch for disconnecting the voltage-dividing circuit and a second switch for disconnecting the voltage-dividing resistor.

14. The integrated circuit of claim 8, wherein: The integrated circuit is an integrated circuit chip for an automobile.

15. The integrated circuit of claim 8, wherein: The integrated circuit is a battery controller.

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