Liquid level detection circuit and electric appliance

Abstract

The application discloses a liquid level detection circuit and an electric appliance, and relates to the technical field of liquid level detection, in particular to a liquid level detection circuit and an electric appliance. The liquid level detection circuit comprises a power supply module, a reference module, and a differential amplification module. The power supply module is provided with a power supply output end. The reference module is connected with the differential amplification module. The differential amplification module is connected with the first probe. The differential amplification module is connected with the reference module. The output end of the differential amplification module is used for outputting a voltage signal. In practical application, the reference voltage of the reference module is pre-set, so that the actual capacitance value of the equivalent capacitor can be calculated according to the voltage value output by the differential amplification module. Moreover, the actual capacitance value of the equivalent capacitor is one-to-one corresponding to the liquid volume of the liquid to be detected, so that the liquid volume of the liquid to be detected can be obtained.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of liquid level detection, and in particular to a liquid level detection circuit and an electric appliance. BACKGROUND

[0002] With the improvement of people's living standards, people have higher requirements for the comfort of the kitchen, and the demand for air conditioner hoods is becoming stronger. The air conditioner hood will produce condensate water during operation, which needs to be detected and discharged.

[0003] The present application provides a new type of liquid level detection circuit for liquid level detection. SUMMARY

[0004] Therefore, the present application provides a new type of liquid level detection circuit and an electric appliance.

[0005] To achieve the above-mentioned purpose, the present application provides a liquid level detection circuit, which comprises: a power supply module provided with a power supply output end;

[0006] An equivalent capacitor comprises a first probe and a second probe arranged at intervals, the first probe extends into the water tank from the top of the water tank, and the second probe extends into the water tank from the bottom of the water tank; the capacitance value of the equivalent capacitor corresponds to the liquid volume of the liquid to be detected; the first probe is connected with the power supply output end, and the second probe is grounded through a first switch module;

[0007] A reference module;

[0008] A differential amplification module, a first input end of the differential amplification module is connected with the first probe, a second input end of the differential amplification module is connected with the reference module, and an output end of the differential amplification module is used for outputting a voltage signal.

[0009] Optionally, the reference module comprises:

[0010] A reference capacitor, a first end of the reference capacitor is connected with the power supply output end, and a second end of the reference capacitor is grounded through a second switch module; the second input end of the differential amplification module is connected with the first end of the reference capacitor.

[0011] Optionally, the liquid level detection circuit further comprises:

[0012] A first discharge resistor is connected in parallel across the equivalent capacitor;

[0013] A second discharge resistor is connected in parallel across the reference capacitor.

[0014] Optionally, the first switch module comprises:

[0015] A first switch tube, a control end of the first switch tube is used for receiving a control signal, a first end of the first switch tube is connected with the second probe, and a second end of the first switch tube is grounded.

[0016] Optionally, the second switch module comprises:

[0017] A second switch tube, a control end of the second switch tube is used for receiving the control signal, a first end of the second switch tube is connected with a second end of the reference capacitor, and a second end of the second switch tube is grounded.

[0018] Optionally, the liquid level detection circuit further comprises:

[0019] A first constant current module connected between the power supply module and the equivalent capacitor;

[0020] A second constant current module connected between the power supply module and the reference capacitor.

[0021] Optionally, the first constant current module and the second constant current module each comprise:

[0022] A third switch tube, a control end of the third switch tube is connected with the power supply output end through a first current limiting resistor, and a first end of the third switch tube is connected with the power supply output end through a second current limiting resistor;

[0023] A fourth switch tube, a control end of the fourth switch tube is connected with a second end of the third switch tube, a first end of the fourth switch tube is connected with the control end of the third switch tube, and a second end of the fourth switch tube is connected with the first probe or a first end of the reference capacitor through a first resistor.

[0024] Optionally, the first constant current module and the second constant current module each comprise:

[0025] A second resistor, one end of the second resistor is connected with the second probe or a second end of the reference capacitor, and the other end of the second resistor is grounded;

[0026] A capacitor, one end of the capacitor is connected with the power supply output end, and the other end of the capacitor is connected with the control end of the fourth switch tube and the first probe or the first end of the reference capacitor.

[0027] Optionally, the first constant current module and the second constant current module further comprise:

[0028] An error amplifier, a first input end of the error amplifier is connected with the second end of the fourth switch tube, and a second input end of the error amplifier is connected with a reference voltage;

[0029] A fifth switch tube, a control end of the fifth switch tube is connected with an output end of the error amplifier, a first end of the fifth switch tube is connected with a control end of the fourth switch tube, and a second end of the fifth switch tube is connected with a first end of the first probe or the reference capacitor.

[0030] Optionally, the first constant current module and the second constant current module further comprise:

[0031] A voltage follower module is configured to generate the reference voltage.

[0032] The embodiment of the present application also provides an electric appliance comprising the liquid level detection circuit.

[0033] Optionally, the electric appliance is an air conditioner or a range hood.

[0034] Compared with the prior art, the technical scheme of the present application has the following advantages:

[0035] 1. The embodiment of the present application provides a liquid level detection circuit, which comprises: a power supply module, provided with a power supply output end; an equivalent capacitor, comprising a first probe and a second probe arranged at intervals, the first probe extending into a water tank from the top of the water tank, and the second probe extending into the water tank from the bottom of the water tank; the equivalent capacitor has a capacitance value corresponding to the liquid volume of a liquid to be detected; the first probe is connected with the power supply output end, and the second probe is grounded through a first switch module; a reference module; a differential amplification module, a first input end of the differential amplification module being connected with the first probe, a second input end of the differential amplification module being connected with the reference module, and an output end of the differential amplification module being configured to output a voltage signal.

[0036] In actual application, since the reference voltage of the reference module is pre-set, the actual capacitance value of the equivalent capacitor can be calculated according to the voltage value output by the differential amplification module. Moreover, the actual capacitance value of the equivalent capacitor corresponds to the liquid volume of the liquid to be detected, so that the liquid volume of the liquid to be detected can be obtained. Specifically, the relationship between the liquid volume and the capacitance value can be obtained according to a calculation formula of the capacitance, or a fixed table or a change curve can be formed by testing the relationship between multiple groups of capacitance values and liquid levels, and then the relationship between the capacitance value and the liquid volume can be obtained by looking up the table or the change curve.

[0037] 2. The embodiment of the present application can achieve better temperature characteristics by arranging the constant current module and arranging the third switch tube and the fourth switch tube in the constant current module, avoid a certain amount of detection error caused by temperature change of the electric appliance during operation, and realize accurate detection of the liquid level by equalizing the current passing through the third switch tube and the fourth switch tube, thereby having high reliability. BRIEF DESCRIPTION OF DRAWINGS

[0038] In order to more clearly illustrate the technical solutions in the specific embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the description of the specific embodiments or the prior art. Obviously, the drawings described below are only some of the embodiments of the present application, and all other drawings obtained by those of ordinary skill in the art without creative work based on these drawings also belong to the protection scope of the present application.

[0039] Figure 1 The structural diagram of the liquid level detection circuit of the embodiment of the present application;

[0040] Figure 2 The schematic diagram of the liquid level detection of the embodiment of the present application;

[0041] Figure 3 The structural diagram of another embodiment of the liquid level detection circuit of the present application;

[0042] Figure 4 The flow chart of the liquid level detection of the embodiment of the present application.

[0043] Reference signs:

[0044] 1, power module; 2, first constant current module; 3, second constant current module; 4, voltage follower module;

[0045] R1, first current limiting resistor; R2, second current limiting resistor; R3, second discharging resistor; R4, first discharging resistor; R5, first resistor; R6, third resistor; R7, fourth resistor; R8, second resistor; R9, fifth resistor; R10, sixth resistor; R11, seventh resistor;

[0046] Q1, first switch tube; Q2, second switch tube; Q3, third switch tube; Q4, fourth switch tube; Q5, fifth switch tube;

[0047] D1, anti-reverse diode; C1, capacitor; CX, equivalent capacitor; CREF, reference capacitor; U13-A, differential amplification module; U16-A, error amplifier; U17-A, voltage follower. DETAILED DESCRIPTION

[0048] The technical solutions of the present application will be described in detail below with reference to the drawings. Obviously, the described embodiments are only some of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work also belong to the protection scope of the present application.

[0049] In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and the like indicate the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second", "third" are only for the purpose of description, and cannot be understood as indicating or implying relative importance.

[0050] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connecting" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the communication inside two elements, it can be wireless connection, or it can be wired connection. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0051] In addition, the technical features involved in the different embodiments of the application described below can be combined with each other as long as there is no conflict.

[0052] With the improvement of people's living standards, people have higher requirements for the comfort of the kitchen, and the demand for air conditioner hoods is becoming more and more intense. The air conditioner hood will produce condensate water during work, which needs to be detected and discharged.

[0053] The present application provides a new liquid level detection circuit for liquid level detection.

[0054] Embodiment 1

[0055] As Figures 1 to 4 shown, the embodiment of the present application provides a liquid level detection circuit, which comprises a power supply module 1, an equivalent capacitor CX, a reference module and a differential amplification module U13-A.

[0056] Specifically, in the embodiment of the present application, the power supply module 1 is provided with a power supply output end. As Figure 2As shown, the equivalent capacitor CX includes a first probe and a second probe which are arranged in a spaced manner, the first probe extends into the water tank from the top of the water tank, the second probe extends into the water tank from the bottom of the water tank, and the water tank is adapted to contain the liquid to be detected. Since the submerged part of the first probe and the submerged part of the second probe correspond to the electrode plates, the liquid level is different, the position of the submerged first probe is different, so that the surface area of the submerged first probe is different, that is, in the formula of the capacitor C = εs / (4πkd), s is different, so the corresponding equivalent capacitance value can be obtained. Therefore, the first probe, the second probe and the water in the water tank together form the equivalent capacitor CX. And the capacitance value of the equivalent capacitor CX corresponds to the liquid volume of the liquid to be detected one by one, and the capacitance value of the equivalent capacitor CX changes with the change of the liquid volume of the liquid to be detected. The first probe is connected with the output end of the power supply, and the second probe is grounded through the first switch module.

[0057] The first input end of the differential amplification module U13-A is connected with the first probe through the fifth resistor R9, the second input end of the differential amplification module U13-A is connected with the reference module through the sixth resistor R10, and the output end of the differential amplification module U13-A is used to output a voltage signal; and the seventh resistor R11 is connected between the output end of the differential amplification module U13-A and the second input end of the differential amplification module U13-A.

[0058] In this way, in actual application, since the reference voltage of the reference module is pre-set, the actual capacitance value of the equivalent capacitor CX can be calculated according to the voltage value output by the differential amplification module U13-A. Specifically, the equivalent capacitor CX and the voltage of the reference module are differentially amplified by the differential amplification module U13-A, and then a differential signal Uc-check is output. Since the reference voltage of the reference module is a known quantity, the capacitance value of the equivalent capacitor CX can be calculated, and the formula is Cx = K*Uc-check, K is a calculation coefficient.

[0059] Moreover, the actual capacitance value of the equivalent capacitor CX corresponds to the liquid volume of the liquid to be detected one by one, so that the liquid volume of the liquid to be detected can be obtained. Specifically, the relationship between the liquid volume and the capacitance value can be obtained according to the calculation formula of the capacitor, or a fixed table or a change curve can be formed by testing the relationship between multiple groups of capacitance values and liquid levels, and then the relationship between the capacitance value and the liquid volume can be obtained by looking up the table or the change curve.

[0060] Further, in an optional embodiment of the present application, the reference module can be a reference capacitor CREF, a first end of the reference capacitor CREF is connected with the power output end, and a second end of the reference capacitor CREF is grounded through a second switch module; and a second input end of the differential amplification module U13-A is connected with the first end of the reference capacitor CREF.

[0061] Of course, as Figure 3 shown by those skilled in the art, the type of the reference module can also be changed according to actual conditions, and the second input end of the differential amplification module U13-A can be directly grounded through the sixth resistor R10. However, the present embodiment is merely illustrative, but is not limited thereto, and any type of reference module capable of achieving the same technical effects can be used.

[0062] Further, in an optional embodiment of the present application, the liquid level detection circuit further comprises a first discharge resistor R4 and a second discharge resistor R3, the first discharge resistor R4 is connected in parallel across the equivalent capacitor CX, and the second discharge resistor R3 is connected in parallel across the reference capacitor CREF.

[0063] In actual application, when the first switch module and the second switch module are turned on, the power module 1 charges the equivalent capacitor CX and the reference capacitor CREF respectively, and if the on time is t, the voltage of the equivalent capacitor CX is Ucx=(I c*t) / Cx, and the voltage of the reference capacitor CREF is Ucref=(I c*t) / Cref, wherein I c is the charging current.

[0064] The voltages of the equivalent capacitor CX and the reference module are then differentially amplified by the differential amplification module U13-A, and then a differential signal Uc-check is output. Since the reference voltage of the reference module is a known quantity, the capacitance value of the equivalent capacitor CX can be calculated. Further, the actual value of the liquid level can be inversely deduced.

[0065] When the first switch module and the second switch module are turned off, the equivalent capacitor CX and the reference capacitor CREF are discharged through the first discharge resistor R4 and the second discharge resistor R3 respectively, and finally the liquid level detection process is completed.

[0066] Further, in an optional embodiment of the present application, the first switch module comprises a first switch tube Q1 and a second switch tube Q2, specifically, a control end of the first switch tube Q1 is used for receiving a control signal SW1, a first end of the first switch tube Q1 is connected with the second probe, and a second end of the first switch tube Q1 is grounded. A control end of the second switch tube Q2 is used for receiving the control signal SW2, a first end of the second switch tube Q2 is connected with the second end of the reference capacitor CREF, and a second end of the second switch tube Q2 is grounded.

[0067] Further, in an optional embodiment of the present application, the liquid level detection circuit further comprises a first constant current module 2 and a second constant current module 3, the first constant current module 2 is connected between the power supply module 1 and the equivalent capacitor CX, and the second constant current module 3 is connected between the power supply module 1 and the reference capacitor CREF.

[0068] Specifically, the first constant current module 2 and the second constant current module 3 each comprise a third switch tube Q3, a fourth switch tube Q4, a second resistor R8 and a capacitor C1.

[0069] The control end of the third switch tube Q3 is connected with the power supply output end through a first current limiting resistor R1, and an anti-reverse diode D1 is arranged between the first current limiting resistor R1 and the control end of the third switch tube Q3, and the first end of the third switch tube Q3 is connected with the power supply output end through a second current limiting resistor R2. The control end of the fourth switch tube Q4 is connected with the second end of the third switch tube Q3, and the first end of the fourth switch tube Q4 is connected with the control end of the third switch tube Q3. The difference between the first constant current module 2 and the second constant current module 3 lies in that the second end of the fourth switch tube Q4 of the first constant current module 2 is connected with the first probe through a first resistor R5, and the second end of the fourth switch tube Q4 of the second constant current module 3 is connected with the first end of the reference capacitor CREF through the first resistor R5.

[0070] Further, one end of the second resistor R8 in the first constant current module 2 is connected with the second probe, and the other end of the second resistor R8 in the first constant current module 2 is grounded. One end of the second resistor R8 in the second constant current module 3 is connected with the second end of the reference capacitor CREF, and the other end of the second resistor R8 in the second constant current module 3 is grounded.

[0071] One end of the capacitor C1 is connected with the power supply output end, and the other end of the capacitor C1 in the first constant current module 2 is connected with the control end of the fourth switch tube Q4 and the first probe at the same time. The other end of the capacitor C1 in the second constant current module 3 is connected with the control end of the fourth switch tube Q4 and the first end of the reference capacitor CREF at the same time.

[0072] The embodiment of the present application can realize better temperature characteristics by arranging the constant current module and arranging the third switch tube Q3 and the fourth switch tube Q4 in the constant current module, avoid a certain amount of detection error caused by temperature change when the electrical appliance works, and realize accurate detection of the liquid level because the currents passing through the third switch tube Q3 and the fourth switch tube Q4 are equal, and the reliability is high.

[0073] Further, in an optional embodiment of the present application, the first constant current module 2 and the second constant current module 3 each comprises an error amplifier U16-A, a first input end of the error amplifier U16-A is connected with a second end of the fourth switch tube Q4, and a second input end of the error amplifier U16-A is connected with a reference voltage. A control end of the fifth switch tube Q5 is connected with an output end of the error amplifier U16-A, and a first end of the fifth switch tube Q5 is connected with a control end of the fourth switch tube Q4.

[0074] And a second end of the fifth switch tube Q5 in the first constant current module 2 is connected with the first probe. A second end of the fifth switch tube Q5 in the second constant current module 3 is connected with a first end of the reference capacitor CREF.

[0075] Further, in an optional embodiment of the present application, the first constant current module 2 and the second constant current module 3 further comprise a voltage follower module 4, which is used to generate the reference voltage. The voltage follower module 4 is internally provided with a voltage follower U17-A, and a third resistor R6 and a fourth resistor R7 connected in series with each other, as shown in Figure 1 The two ends of the third resistor R6 and the fourth resistor R7 are respectively connected with a positive voltage and a reference ground. A first input end of the voltage follower U17-A is connected between the two resistors, and a second input end of the voltage follower U17-A is connected to an output end of the voltage follower U17-A.

[0076] Therefore, the constant current I C is the current passing through the power module 1 in Figure 1 , the third switch tube Q3, the fourth switch tube Q4 and the fifth switch tube Q5. As shown in the figure, the I 1 and I 2 currents are equal, and the currents flow through the equivalent capacitor CXCX to charge at the same time, and I 1 = I 2 = {5 * R7 / (R6+R7)} / R5.

[0077] Therefore, the total current is I C = 2 * 5 * R7 / (R6+R7)} / R5.

[0078] And the reference voltage U1 = 5 * R7 / (R6+R7) is obtained through the voltage follower U17-A, and the reference voltage is given to the inverting input end of the error amplifier U16-A, and the fifth switch tube Q5 is controlled by comparing the voltage on the first resistor R5, so as to achieve the purpose of constant current.

[0079] The embodiment of the present application also provides an electric appliance, which comprises the liquid level detection circuit in any one of the above-mentioned embodiments. The electric appliance can be an air conditioner and a smoke machine.

[0080] Obviously, the above embodiments are merely exemplary and not intended to limit the embodiments. Based upon the above description, one of ordinary skill in the art can make other variations or changes in the form and details herein. It is not necessary to recite all the embodiments. The obvious variations or changes extending from the present disclosure are still within the scope of the present disclosure.

Claims

1. A liquid level detection circuit, characterized by, The utility model relates to a liquid level detection device, including: Power module (1) is provided with power output end; Equivalent capacitor (CX) including interval first probe and second probe, the first probe from the top of water tank into water tank, the second probe from the bottom of water tank into water tank;The capacitance of equivalent capacitor (CX) corresponds with the liquid volume of liquid to be detected one to one;The first probe is connected with power output end, and the second probe is grounded through first switch module; Reference module; Difference amplification module (U13-A), the first input of difference amplification module (U13-A) is connected with the first probe, and the second input of difference amplification module (U13-A) is connected with reference module, and the output of difference amplification module (U13-A) is used to output voltage signal.

2. The liquid level detection circuit according to claim 1, characterized in that, The reference module includes: Reference capacitor (CREF), the first end of reference capacitor (CREF) is connected with the power output end, and the second end of reference capacitor (CREF) is grounded through second switch module;The second input of difference amplification module (U13-A) is connected with the first end of reference capacitor (CREF).

3. The liquid level detection circuit according to claim 2, characterized in that Also including: First discharge resistance (R4) is connected in parallel across equivalent capacitor (CX); Second discharge resistance (R3) is connected in parallel across reference capacitor (CREF).

4. The liquid level detection circuit of claim 1, wherein The first switch module includes: First switch tube (Q1), the control end of first switch tube (Q1) is used to receive control signal, and the first end of first switch tube (Q1) is connected with the second probe, and the second end of first switch tube (Q1) is grounded.

5. The liquid level detection circuit of claim 2, wherein, The second switch module includes: Second switch tube (Q2), the control end of second switch tube (Q2) is used to receive control signal, and the first end of second switch tube (Q2) is connected with the second end of reference capacitor (CREF), and the second end of second switch tube (Q2) is grounded.

6. The liquid level detection circuit of claim 2, wherein Also including: First constant current module (2) is connected between power module (1) and equivalent capacitor (CX); Second constant current module (3) is connected between power module (1) and reference capacitor (CREF).

7. The liquid level detection circuit according to claim 6, characterized in that The first constant current module (2) and the second constant current module (3) all include: Third switch tube (Q3), the control end of third switch tube (Q3) is connected with the power output end through first current-limiting resistance (R1), and the first end of third switch tube (Q3) is connected with the power output end through second current-limiting resistance (R2); Fourth switch tube (Q4), the control end of fourth switch tube (Q4) is connected with the second end of third switch tube (Q3), and the first end of fourth switch tube (Q4) is connected with the control end of third switch tube (Q3);The second end of fourth switch tube (Q4) is connected with the first probe or the first end of reference capacitor (CREF) through first resistance (R5);The current through third switch tube (Q3) and fourth switch tube (Q4) is equal.

8. The liquid level detection circuit according to claim 7, characterized in that The first constant current module (2) and the second constant current module (3) all include: a second resistor (R8), one end of the second resistor (R8) is connected with the second probe or the second end of the reference capacitor (CREF), the other end of the second resistor (R8) is grounded; a capacitor (C1), one end of the capacitor (C1) is connected with the power output end, the other end of the capacitor (C1) is connected with the control end of the fourth switch tube (Q4) and the first end of the reference capacitor (CREF) at the same time.

9. The liquid level detection circuit according to claim 8, characterized in that Further comprising: an error amplifier (U16-A), the first input end of the error amplifier (U16-A) is connected with the second end of the fourth switch tube (Q4), the second input end of the error amplifier (U16-A) is connected with a reference voltage; a fifth switch tube (Q5), the control end of the fifth switch tube (Q5) is connected with the output end of the error amplifier (U16-A), the first end of the fifth switch tube (Q5) is connected with the control end of the fourth switch tube (Q4), the second end of the fifth switch tube (Q5) is connected with the first end of the reference capacitor (CREF).

10. The liquid level detection circuit of claim 9, wherein, Further comprising: a voltage follower module (4) for generating the reference voltage.

11. An electrical appliance characterised in that Comprise: The liquid level detection circuit of any one of claims 1 to 10.

12. The appliance of claim 11, wherein, The electric appliance is an air conditioner or a smoke machine.

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