CN113038639B - Electric heating switch control circuit and air conditioner with same - Google Patents
Electric heating switch control circuit and air conditioner with same Download PDFInfo
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- CN113038639B CN113038639B CN202110199772.2A CN202110199772A CN113038639B CN 113038639 B CN113038639 B CN 113038639B CN 202110199772 A CN202110199772 A CN 202110199772A CN 113038639 B CN113038639 B CN 113038639B
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- 238000005485 electric heating Methods 0.000 title claims abstract description 123
- 238000001514 detection method Methods 0.000 claims abstract description 38
- 238000010438 heat treatment Methods 0.000 claims abstract description 19
- 238000004804 winding Methods 0.000 claims description 8
- 238000001914 filtration Methods 0.000 claims description 2
- 239000003990 capacitor Substances 0.000 description 13
- 238000010586 diagram Methods 0.000 description 12
- 239000003507 refrigerant Substances 0.000 description 9
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 9
- 230000008859 change Effects 0.000 description 5
- 230000002159 abnormal effect Effects 0.000 description 4
- 238000004378 air conditioning Methods 0.000 description 4
- 238000001816 cooling Methods 0.000 description 4
- 238000000034 method Methods 0.000 description 3
- 230000008569 process Effects 0.000 description 3
- 238000004891 communication Methods 0.000 description 2
- 230000001276 controlling effect Effects 0.000 description 2
- 230000005611 electricity Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012216 screening Methods 0.000 description 2
- 238000006467 substitution reaction Methods 0.000 description 2
- 230000009471 action Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 238000005057 refrigeration Methods 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 238000011144 upstream manufacturing Methods 0.000 description 1
Classifications
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B1/00—Details of electric heating devices
- H05B1/02—Automatic switching arrangements specially adapted to apparatus ; Control of heating devices
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
- F24F11/00—Control or safety arrangements
- F24F11/88—Electrical aspects, e.g. circuits
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B1/00—Details of electric heating devices
- H05B1/02—Automatic switching arrangements specially adapted to apparatus ; Control of heating devices
- H05B1/0202—Switches
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B1/00—Details of electric heating devices
- H05B1/02—Automatic switching arrangements specially adapted to apparatus ; Control of heating devices
- H05B1/0227—Applications
- H05B1/0252—Domestic applications
- H05B1/0275—Heating of spaces, e.g. rooms, wardrobes
- H05B1/028—Airconditioning
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
- F24F2221/00—Details or features not otherwise provided for
- F24F2221/34—Heater, e.g. gas burner, electric air heater
Abstract
The invention relates to the technical field of electric heating control, and particularly provides an electric heating starting control circuit and an air conditioner comprising the same, wherein the electric heating starting control circuit comprises: the switching circuit comprises a first electric control switch capable of switching the working state and the non-working state of the electric heating and a second electric control switch capable of switching the electric connection between an external power supply and the electric heating; an enabling circuit for switching to an enabling state in case the first electronically controlled switch is opened; a detection circuit for detecting an electrically heated current signal and converting the current signal into a voltage signal; and the judging circuit is used for comparing the voltage signal input by the detecting circuit with the reference voltage in the enabling state, and switching off the second electric control switch under the condition that the voltage signal is higher than the reference voltage. By such arrangement, when the electrical heating relay is in contact adhesion, the phenomenon of excessively high electrical heating temperature can be avoided.
Description
Technical Field
The invention relates to the technical field of electric heating control, in particular to an electric heating switch control circuit and an air conditioner with the same.
Background
The air conditioner mainly comprises a compressor forming a main loop of a refrigerant, an indoor heat exchanger, a throttling part and an outdoor heat exchanger, wherein the temperature of an indoor space where the indoor heat exchanger is located can be regulated along with the phase change of the refrigerant through the circulation flow of the refrigerant in the loop formed by the compressor, the condenser, the throttling part, the evaporator and the compressor. As in the case of the air conditioner in the heating mode, the indoor heat exchanger is a condenser that emits heat so as to raise the temperature of the indoor space. According to whether the frequency of the compressor is adjustable, the air conditioner can be divided into a variable frequency air conditioner and a fixed frequency air conditioner, wherein the variable frequency air conditioner can adjust the rotating speed by adjusting the motor frequency of the compressor, and the fixed frequency air conditioner is that the compressor is operated in a mode that the rotating speed is basically unchanged under the fixed motor frequency, so that the compressor only comprises an on state and an off state.
In order to ensure the service performance of the fixed-frequency air conditioner, the air conditioner is usually provided with electric heating, for example, an electric control switch such as a relay can be adopted to control the operation of the electric heating. Referring to fig. 1, fig. 1 is a schematic diagram showing the configuration of an electrically heated switch control circuit according to the prior art. As shown in fig. 1, the control logic of the control circuit is open loop control without feedback signal, specifically: the controller realizes the opening/closing control of the contacts of the relay K through the relay driver, so that the electric heating is in a non-working/working state when the contacts are opened/closed. Specifically: after the air conditioner is started, the control board controls the contact of the relay to be closed, and the electric heating is started to run; when the temperature of the indoor space reaches the target temperature set by a user, the control board controls the contacts of the relay to be opened, and the electric heating is stopped immediately.
However, there are problems in that: because the electric heating power is larger and is influenced by the service life of the relay, at the moment when the relay stops running, the phenomenon of contact adhesion can occur due to the abrupt change of the current of the switch contact of the relay. The contact adhesion directly leads to the disconnection failure of the electric heating relay, which is specifically shown as follows: when the temperature of the indoor space has reached the target temperature and the control board has issued a command to open the relay according to the result, the load will remain in operation since the relay is not open according to the command. Such a state, if not suspended in time, causes a problem such as an excessively high temperature of the electric heating.
Specifically, in a general case, during the electric heating operation, the indoor fan of the air conditioner is also started to operate so as to promote the heat exchange. If the electric heating is started, the indoor fan starts to operate, after the electric heating is turned off for a certain time, the self temperature of the electric heating (the temperature of the heating wire) can be reduced to a certain low value, and then the indoor fan can be stopped immediately. In the case where the electrical heating relay is stuck at the contact point, after the temperature of the indoor space has reached the target temperature, since the self temperature of the electrical heating is not lowered, but since the indoor fan has been stopped according to the instruction after the electrical heating is turned off for a certain time, this will cause a problem that the temperature of the electrical heating is excessively high.
Accordingly, there is a need in the art for a new solution to the above-mentioned problems.
Disclosure of Invention
In view of the fact that the phenomenon of contact adhesion may occur due to abrupt change of current of a switch contact of the electric heating relay at the moment when the electric heating relay stops running, the technical problem to be solved by the invention is as follows: how to avoid the problem of overhigh electric heating temperature when the electric heating relay has abnormal contact disconnection, such as contact adhesion and the like.
To achieve the above object, a first aspect of the present invention provides an electric heating start control circuit, comprising: 1) The switching circuit comprises a first electric control switch and a second electric control switch, the working state and the non-working state of the electric heating can be switched by switching the first electric control switch, and the electric connection between an external power supply and the electric heating can be switched by switching the second electric control switch; 2) An enabling circuit for switching to an enabling state in case the first electronically controlled switch is opened; 3) A detection circuit for detecting an electrically heated current signal and converting the current signal into a voltage signal; and 4) a judging circuit for comparing the voltage signal input by the detecting circuit with the reference voltage in the enabling state, and turning off the second electric control switch in the case that the voltage signal is higher than the reference voltage.
For the above electric heating start control circuit, in one possible implementation manner, the electric heating start control circuit includes a controller and a driving circuit, where the controller sends a signal capable of switching an operating state and a non-operating state of electric heating to the first electric control switch through the driving circuit.
For the above electric heating start control circuit, in one possible implementation manner, the first end of the first electric control switch is connected with the electric heating, the second end of the first electric control switch is connected with the first end of the second electric control switch, and the second end of the second electric control switch is connected with an external power source, so that the working state of the electric heating is switched by the first electric control switch and the first electric control switch, and the external power source can supply power to the electric heating under the condition that both the first electric control switch and the second electric control switch are closed.
For the above electric heating start control circuit, in one possible implementation manner, the judging circuit includes a first resistor, a second resistor and a signal comparator, where a first end of the first resistor is connected to a positive electrode of a power supply, a second end of the first resistor is connected to a first end of the second resistor, a first end of the second resistor is further connected to a non-inverting input end of the signal comparator, a negative-phase input end of the signal comparator is connected to an output end of the detection circuit, and a second end of the second resistor is connected to analog ground, so that a voltage dividing circuit formed by the first resistor and the second resistor provides a reference voltage for the detection circuit; the output end of the signal comparator is connected with the control end of the second electric control switch so as to send a signal for disconnecting the second electric control switch to the control end of the second electric control switch when the voltage signal of the detection circuit is higher than the reference voltage, and the signal comparator is also connected with the output end of the enabling circuit so as to obtain electricity under the condition that the enabling circuit is conducted.
For the above electric heating start control circuit, in one possible implementation manner, the enabling circuit includes a first diode, a first triode and a second triode, an anode of the first diode is connected with a base of the first triode, a cathode of the first diode is connected with the controller and a control end of the first relay respectively, an emitter of the first triode is grounded, a collector of the first triode is connected with a base of the second triode, an emitter of the second triode is connected with an anode of the power supply, so that when the controller sends a signal for closing the first electric control switch to the first electric control switch, the enabling circuit is turned on, a collector of the second triode is connected with the signal comparator, and in case that the enabling circuit is turned on, the signal comparator is powered on.
For the above electric heating start control circuit, in one possible implementation manner, the first triode is an NPN triode, and the second triode is a PNP triode.
For the above electric heating start control circuit, in one possible implementation manner, the enabling circuit further includes a second diode and a third diode, an anode of the second diode is connected with an anode of the first diode, a cathode of the second diode is connected with an anode of the third diode, and a cathode of the third diode is connected with a base of the first triode, so as to prevent a phenomenon that the base of the first triode is conducted when the controller conducts the first electric control switch.
For the above-mentioned electric heating start-up control circuit, in one possible implementation, the detection circuit includes a current transformer for converting the first current detected at the first winding side into the second current at the second winding side, a dc filter for filtering the voltage signal corresponding to the dc before outputting to the judgment circuit, and a rectifier for rectifying the second current from ac to dc.
For the above electric heating start control circuit, in one possible implementation manner, the detection circuit further includes a third resistor and a fourth resistor, a first end of the fourth resistor is connected to a positive electrode of the dc side of the rectifier, a second end of the fourth resistor is connected to the first end of the third resistor, a second end of the third resistor is grounded, dc is converted into a voltage signal through the third resistor and the fourth resistor, the third resistor is an adjustable resistor, and the voltage signal transmitted to the judgment circuit is adjusted by adjusting a resistance value of the third resistor, so as to adjust detection accuracy of the detection circuit.
Through the arrangement, when the electric heating is started normally, the judging circuit cannot work electrically through the intervention of the enabling circuit, so that the external power supply and the electric heating can be kept in electric connection, and the electric heating is started normally. When the electric heating stops working, the judging circuit is enabled to work electrically through the intervention of the enabling circuit, and when the electric heating stops working normally, an external power supply is connected with the electric heating in an electric power connection mode when the electric heating stops working normally. And when the electric heating is continued to work under the condition that the electric heating should stop working due to the contact adhesion of the first electric control switch, the problem of overhigh temperature of the electric heating is prevented by disconnecting the electric power between the external power supply and the electric heating.
A second aspect of the present invention provides an air conditioner including an electric heater configured with the electric heating start control circuit of any one of the foregoing.
It can be appreciated that the air conditioner has all the technical effects of the aforementioned electric heating start control circuit, and will not be described herein.
Drawings
Embodiments of the invention are described below with reference to the accompanying drawings, in which:
fig. 1 is a schematic diagram showing the structure of an electric heating switch control circuit of the prior art;
fig. 2 is a block diagram showing a configuration of an electric heating switch control circuit of a fixed-frequency air conditioner according to an embodiment of the present invention;
fig. 3 is a schematic diagram showing the structure of an electric heating switch control circuit of a constant frequency air conditioner according to an embodiment of the present invention;
fig. 4 is a schematic diagram showing a structure of a judging circuit in an electric heating switch control circuit of a fixed-frequency air conditioner according to an embodiment of the present invention;
fig. 5 is a schematic diagram showing the structure of an enabling circuit in an electric heating switch control circuit of a fixed-frequency air conditioner according to an embodiment of the present invention; and
fig. 6 is a schematic diagram showing a structure of a detection circuit in an electric heating switch control circuit of a fixed-frequency air conditioner according to an embodiment of the present invention.
Detailed Description
Some embodiments of the invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are merely for explaining the technical principles of the present invention, and are not intended to limit the scope of the present invention. Such as an electronically controlled switch, is understood to be a switch that is capable of being opened or closed under control of an electrical signal. For example, an electronically controlled switch should include a switch body capable of being opened or closed and a control terminal capable of receiving and controlling the opening or closing of the switch body according to an electrical signal. Such as an electronically controlled switch, may include, but is not limited to, a relay of the present embodiment, such as a transistor, etc.
It should be noted that in the description of the present invention, the terms "first," "second," and "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance. Furthermore, unless explicitly stated and limited otherwise, the terms "connected," "connected," and "connected" are to be construed broadly, and may be, for example, directly connected or indirectly connected through intervening media, or may be in communication between two elements. The specific meaning of the above terms in the present invention can be understood by those skilled in the art according to the specific circumstances.
The air conditioner mainly comprises a compressor forming a main loop of a refrigerant, an indoor heat exchanger, an outdoor heat exchanger, a throttling component (such as a capillary tube, an electronic expansion valve and the like) and a four-way valve, wherein the communication mode of the four-way valve is switched, so that the air conditioner has a conventional refrigerating mode and a heating mode, and cold/heat can be emitted to the surface of the indoor heat exchanger along with the phase change of the refrigerant through the circulation flow of the refrigerant in the loop formed by the compressor, the condenser, the throttling component, the evaporator and the compressor. Specifically: when the refrigerant circularly flows along the loop of the compressor, the indoor heat exchanger, the outdoor heat exchanger and the compressor, the air conditioning system is in heating circulation. Namely: in the case of an air conditioning system in a heating mode, the indoor heat exchanger serves as a condenser for emitting heat; and when the refrigerant circularly flows along the loop of the compressor, the outdoor heat exchanger, the indoor heat exchanger and the compressor, the air conditioning system is in refrigeration cycle. Namely: in the case where the air conditioning system is in a cooling mode, the indoor heat exchanger serves as an evaporator that emits cooling energy.
An air conditioner generally includes an outdoor portion and an indoor portion, which are integrated in the same housing for some models (e.g., window units, etc.). For most models, the outdoor part and the indoor part are of split type, wherein the outdoor part is called an air conditioner outdoor unit, the indoor part is called an air conditioner indoor unit, and the outdoor part and the indoor part are connected through a pipeline.
Split-type air conditioners generally include cabinet type air conditioners, hanging air conditioners, embedded air conditioners, and the like. Taking a wall-mounted machine as an example, the back of a shell of an indoor unit of an air conditioner is usually fixedly arranged on a wall of an indoor space, an air supply opening and an air return opening (such as bottom air supply and bottom air return) are formed in the shell, an indoor heat exchanger, an indoor fan, a water receiving disc, an electric cabinet and the like are mainly arranged in the shell, the air conditioner is in the refrigerating/heating cycle process, under the action of the indoor fan, part of air in the indoor space is pumped into the shell through the air return opening, after heat exchange is carried out with the surface of the indoor heat exchanger, the temperature of the part of air is reduced/increased, and then the part of air with reduced temperature is sent into the indoor space again through the air supply opening, so that the cooling capacity/heat generated by the phase change of a refrigerant and the circulating flow can be gradually released to the indoor space. The surface of the condenser may generate condensed water while radiating heat to the indoor space. In order to ensure the sustainability of the cooling, it is necessary to drain the condensed water to the outdoor side in time. Correspondingly, be provided with the water collector below indoor heat exchanger, the comdenstion water that the water collector mainly used produced on indoor heat exchanger surface is provided with the drainage joint who docks with the water collector on the casing of air conditioner indoor set generally, and the drainage joint disposes the drain pipe, and the upstream side and the drainage joint of drain pipe match and link to each other, and the outdoor side can be stretched out to the downstream side to the comdenstion water that will collect the water collector through the drain pipe in time discharges the outdoor side, thereby has guaranteed the operation sustainability of air conditioner.
In the case that the air conditioner is a fixed-frequency air conditioner, in order to better realize the heating performance of the air conditioner, an electric heating device is generally configured for the indoor air conditioner, for example, the electric heating device can be used for improving the user experience in the initial operation period of the air conditioner and when the heating requirement intensity is high.
The invention provides an electric heating start control circuit which is used for ensuring the service performance of electric heating arranged in a fixed-frequency air conditioner. The electric heating starting control circuit mainly comprises a switch group, an enabling circuit, a detection circuit and a judging circuit, wherein the switch group comprises a first electric control switch and a first electric control switch, the first electric control switch is a relay (respectively recorded as K1 and K2), K1 is arranged between the starting control circuit and electric heating, K2 is arranged between an external power supply and the control circuit, and the working principle of the electric heating starting control circuit is as follows:
the controller (MCU) sends a signal to turn it on or off to K1 through the driving circuit. The judgment circuit can send a signal to turn it on or off to K2. The driving circuit may be implemented by an alternative driving chip or the like, as in the present embodiment, a driving chip (denoted as chip IC 1) of model ULN2003, hereinafter referred to as a relay driver. The enabling state of the judging circuit is controlled by the enabling circuit, specifically, such control logic is executed only in the case where the controller issues a signal to turn off K1: the detection circuit detects a CURRENT signal (HEAT-CURRENT) of the electric Heating (HEAT) and converts the CURRENT signal into a voltage signal, and the judgment circuit compares the voltage signal with a reference voltage and sends a signal for turning off K2 under the condition that the voltage signal is higher than the reference voltage. Namely: the enabling circuit can be turned on only when the electric heating operation state is abnormal closing caused by contact adhesion (the enabling circuit is a switching function, so the enabling circuit can be called as an enabling switch), and at this time, the judging circuit can disconnect K2 based on the detection result of the detecting circuit, so that the external power supply and the electric heating power are disconnected. Specifically:
1) Closed control to put the electric heating in operation:
the controller sends a signal for instructing the relay driver to close to K1 (the relay driver outputs a low level), and based on this, the determination circuit is disabled by sending an enable control to the enable circuit. Since the judgment circuit does not operate, it is not given whether the voltage exceeds the reference voltage according to the electric current of the electric heater detected by the detection circuit and therefore an instruction to open the second relay is issued, in which case the power connection of the power supply to the electric heater start control circuit is maintained, and the first relay can be normally closed based on the low level, and the electric heater is thus normally brought into an operating state.
2) Off control to put the electric heating in the non-operation state:
the controller sends a signal for instructing the switching off thereof (relay driver outputs a high level) to K1 through the relay driver, and at the same time, based on this, causes the determination circuit to operate by sending an enable control to the enable circuit. At this time:
21 If the electric heating continues to operate, the voltage derived from the current detected by the detection circuit exceeds the reference voltage. The judgment circuit can disconnect K2 according to the result, namely, the electric connection between the external power supply and the electric heating start control circuit is disconnected. Such control logic is designed because: in this case, the electrical heating is in an operating state due to contact adhesion, and this abnormal operating state can be stopped by disconnecting the power supply from the electrical heating start control circuit.
22 If the electric heating is not operated, the voltage derived from the current detected by the detection circuit does not exceed the reference voltage. The judging circuit can enable K2 to be continuously closed and conducted according to the result, namely, electric power connection between an external power supply and electric heating is kept. Such control logic is designed because: in this case, the electric heating has been reliably switched to the non-operating state in accordance with the off instruction of the controller, and therefore, there is no need to disconnect the electric power connection between the power source and the electric heating.
Referring to fig. 2 to 6, fig. 2 is a block diagram showing a structure of an electric heating switch control circuit of a fixed frequency air conditioner according to an embodiment of the present invention, fig. 3 is a schematic diagram showing a structure of an electric heating switch control circuit of a fixed frequency air conditioner according to an embodiment of the present invention, fig. 4 is a schematic diagram showing a structure of a judgment circuit in an electric heating switch control circuit of a fixed frequency air conditioner according to an embodiment of the present invention, fig. 5 is a schematic diagram showing a structure of an enable circuit in an electric heating switch control circuit of a fixed frequency air conditioner according to an embodiment of the present invention, and fig. 6 is a schematic diagram showing a detection circuit in an electric heating switch control circuit of a fixed frequency air conditioner according to an embodiment of the present invention. Next, the electric heating start control device of the present invention will be described with reference to fig. 2 to 6. The electric heating start control device mainly comprises:
1. switching circuit (see fig. 2 and 3):
the switching circuit comprises K1 (electric heating relay) serving as a first electric control switch and K2 (power relay) serving as a second electric control switch, wherein a first end of the K1 is connected with electric heating, a second end of the K1 is connected with a first end of the K2, and a second end of the K2 is connected with an external power supply.
The controller sends a signal to the control terminal of K1 through the relay driver, thereby switching the on/off state of K1.
2) In the case where the enable circuit is turned on, a signal is sent to the control terminal of K2 by the judgment circuit, thereby switching the on/off state of K2. Specifically: k2 is switched to a closed state when the movable contact 5 is switched to, and under the condition that both K1 and K2 are closed, the power supply is connected with electric heating power; k2 is switched to the movable contact 4 in an open state, and at this time, the power supply is disconnected from the electric power for electric heating, regardless of whether K1 is closed.
2. Judgment circuit (refer to fig. 2 to 4):
the judging circuit is mainly used for comparing the voltage signal input by the detecting circuit with the reference voltage and controlling the switching state of K2 according to the comparison result.
The judging circuit mainly comprises a resistor R7 serving as a first resistor, a resistor R10 serving as a second resistor and a signal comparator, and the specific circuit is connected with the following components: the first end of the resistor R7 is connected with the positive electrode of the power supply, the second end of the resistor R7 is connected with the first end of the resistor R10, the first end of the resistor R10 is also connected with the positive input end of the signal comparator, the second end of the resistor R10 is connected with the analog ground, the first end and the second end of the resistor R9 are respectively connected with the negative input end of the signal comparator and the output end (the first pole of the capacitor C2), the first pole of the capacitor C3 is respectively connected with the negative input end of the signal comparator and the first end of the resistor R9, the second pole of the capacitor C3 is connected with the analog ground, the first end and the second end of the resistor R5 are respectively connected with the positive electrode of the power supply and the output end of the signal comparator, the output end of the signal comparator is directly connected with the control end of the K2, and the signal comparator is also connected with the output end (the collector of the triode P1) of the judging circuit so that under the condition that the enabling circuit is conducted, the signal comparator is electrified.
In this embodiment, as shown in fig. 4, the signal comparator is a chip (denoted as chip IC 2) with model LM293DR, and further referring to fig. 4, the chip IC2 includes two signal comparators, wherein one of the signal comparators (signal comparator on the left) has its positive input terminal grounded and its negative input terminal connected to the output terminal so as to be a standby signal comparator, and the other signal comparator (signal comparator on the right) is a signal comparator in the judging circuit in the electric heating signal control circuit of the present invention.
Based on such a circuit structure, the principle that the judging circuit realizes the judging control function is as follows: after the controller sends out the instruction (K1 is disconnected) for turning off the electric heating, the enabling circuit is turned on, and the power supply can be output to the signal comparator under the condition that the enabling circuit is turned on. That is, after the K1 is turned off, the signal comparator is powered on, the judging circuit starts to work, and the judging circuit can control the on-off of the K2 according to the detection result of the detecting circuit. Specifically, the resistor R7 and the resistor R10 of the judgment circuit are used to provide a reference voltage for determining whether to turn off K2, specifically: r7 and R10 form a voltage dividing circuit, and a reference voltage Vref is determined, specifically: vref=r10/(r7+r10) ×vcc. The signal comparator compares the voltage signal input by the detection circuit with the reference voltage, and determines whether to send a signal for disconnecting K2 to the control terminal of K2 according to the comparison result, specifically:
when the voltage signal input by the detection circuit is higher than the reference voltage, the output end of the signal comparator sends a signal for disconnecting K2 to the control end of K2, so that the power connection between the power supply and the electric heating signal control circuit is cut off, and the electric heating caused by contact adhesion is prevented from continuously working;
when the voltage signal input by the detection circuit is not higher than the reference voltage, the output end of the signal comparator sends a signal for enabling the K2 to be continuously attracted to the control end of the K2, so that under the condition of no contact adhesion, the electric connection between the power supply and the electric heating signal control circuit is maintained after the electric heating stops working.
Note that, the ABLE (enable signal) output in fig. 3 and 4 is not a separate signal, but should be understood as: after K1 is disconnected, the enabling circuit is conducted, and the signal comparator can obtain electricity.
3. Enable circuit (see fig. 2, 3 and 5):
the enabling circuit is used for enabling the enabling circuit to be conducted or not conducted according to the switching state of K1. In the case that the enabling circuit is turned on, the judging circuit is powered on to be in an operating state. The enabling circuit mainly includes a diode D1 as a first diode, a first triode (in this embodiment, the first triode is an NPN triode N1) and a second triode (in this embodiment, the second triode is a PNP triode P1), and the specific circuit structure is: the positive pole of diode D1 is connected with triode N1's base, diode D1's positive pole still is connected with the positive pole of power through resistance R2, resistance R11's first end is connected with triode N1's base, resistance R11's second end ground connection, diode D1's negative pole is connected respectively with controller and K1's control end, triode N1's projecting pole ground connection, triode N1's collecting electrode is connected with triode P1's base through resistance R8, triode P1's projecting pole is connected with the positive pole of power, resistance R1's first end is connected with the positive pole of power, resistance R1's second end is connected with triode P1's base, triode P1's collecting electrode is connected with ABLE, ABLE is used for initiatively supplying power to the signal comparator of judgement module under the condition that enables the circuit switch on, thereby make judgement circuit can judge whether break off K2 according to detection result of detection circuit.
Based on such a circuit structure, the principle of enabling the circuit to realize the enabling control function is as follows:
when the controller sends a signal for enabling the electric heating operation (enabling K1 to be closed), a low-voltage signal is output by the pin 3 of the relay driver, the anode of the diode D1 is connected with the positive electrode of the power supply, the cathode of the diode D1 is connected to the pin 3 and grounded, and therefore the diode D1 is conducted. In this way, the diode D1 pulls down the base voltage of the transistor N1, thereby turning off the transistor N1. On the premise that the triode N1 is in an off state, the triode P1 is also necessarily in an off state, the enabling circuit cannot be turned on, and the enabling signal cannot be output. That is, the judging circuit is in a non-working state, the signal comparator does not work, and a signal for disconnecting K2 is output at the output end of the signal comparator in the normal working process of electric heating.
When the controller sends out a signal for stopping the electric heating (switching K1 on/off), the pin 3 of the relay driver outputs a high-resistance signal, and the control end of the first relay is connected to the positive electrode of the power supply, so that the pin 3 of the relay driver presents a high-level signal, the cathode of the diode D1 is connected with the positive electrode of the power supply, the cathode of the diode D1 is connected to the pin 3 and grounded, and the anode of the diode D1 is connected with the positive electrode of the power supply through the resistor R2, so that the diode D1 is reversely cut off, and the conduction of the first triode is ensured through the reverse cut-off of the diode D1. Specifically, since the base electrode of the triode N1 is connected with the positive electrode of the power supply and the base voltage of the triode N1 is not pulled down, the triode N1 is in a conducting state, and on the premise that the triode N1 is in a conducting state, since the emitter electrode of the triode P1 is connected with the positive electrode of the power supply and the base electrode is connected with the collector electrode of the triode N1, the triode P1 is conducted, the enabling circuit is conducted, and an enabling signal is output to the judging circuit. That is, the judgment circuit is put into an operation state at this time, and the signal comparator is operated, so that a signal indicating whether or not K2 is to be turned off can be output from the output terminal of the signal comparator based on the detection result of the detection circuit.
Preferably, the enabling circuit further comprises a diode D4 as a second diode and a diode D7 as a third diode, and the specific circuit connection is as follows: the anode of the diode D4 is connected with the anode of the diode D1, the cathode of the diode D4 is connected with the anode of the diode D7, and the cathode of the diode D7 is connected with the base of the triode N1. Based on this circuit configuration, when K1 is normally turned on, since diode D1 is turned on, pin 3 of chip IC1 outputs a low level, the voltage is about 0.7V, and the voltage drop of diode D1 is about 0.7V, so the voltage of the anode of diode D1 is about 1.4V. At this time, if the diode D4 and the diode D7 are not provided, the transistor N1 may have a base turned on, that is, may have a possibility that the enable circuit is disabled (the external power supply is turned off in the state of the electric heating operation). In the case of switching in the diode D4 and the diode D7, since the voltage for turning on both diodes is also about 1.4V, there is no such case: the base conduction of transistor N1 occurs under normal conduction of K1. Thus, the diode D4 and the diode D7 play a role of clamp protection.
4. Detection circuit (see fig. 2, 3, and 6):
the detection circuit is used for detecting the electric heating current and converting the electric heating current into a voltage signal to be transmitted to the judging module. The detection circuit mainly includes a current transformer CT1, a dc filter (in this embodiment, the dc filter is an electrolytic capacitor E1) and a rectifier (in this embodiment, the rectifier is a full bridge rectifier BD 1), and the specific circuit structure is as follows: the primary winding side of the current transformer CT1 is used for detecting the first current (large current) of electric heating and converting the first current into the second current (small current) at the secondary winding side of the current transformer CT1, the secondary winding side of the current transformer CT1 is connected with the ac side of the full-bridge rectifier BD1, the positive pole and the negative pole of the dc side of the rectifier BD1 are respectively connected with the negative pole and the positive pole of a dc filter (in this embodiment, the dc filter is an electrolytic capacitor E1), and the second current is rectified by the full-bridge rectifier BD1 and filtered by the electrolytic capacitor E1 in sequence and then outputs a voltage signal corresponding to the detected first current to the judging module.
In this way, when the electric heating is continued due to contact adhesion, after the current transformer CT1 detects the electric heating current (ac), a voltage signal corresponding to the current is transmitted to the determination circuit.
Preferably, the detection circuit further includes a resistor VR1 (adjustable resistor) as a third resistor and a resistor R6 as a fourth resistor, and the specific circuit is connected as follows: the first end of the resistor R6 is connected with the positive pole of the direct current side of the rectifier BD1, the second end of the resistor R6 is connected with the first end of the resistor VR1, the second end of the resistor VR1 is grounded, the third end of the resistor VR1 is connected with the negative pole of the electrolytic capacitor E1, the first end and the second end of the resistor R4 are respectively connected with the positive pole of the electrolytic capacitor E1 and the negative pole of the direct current side of the rectifier BD1, the negative pole of the electrolytic capacitor E1 is grounded, the anode of the diode D2 is connected with the positive pole of the electrolytic capacitor E1, the cathode of the diode D2 is connected with the positive pole of a power supply, the first end of the resistor R3 is respectively connected with the first end of the capacitor C2 and the second end of the judging circuit R9, the second end of the resistor R3 is respectively connected with the positive pole of the electrolytic capacitor E1, the first end of the resistor R4 and the anode of the diode D2, and the second end of the capacitor C2 is grounded.
The second current output by the secondary winding side of the current transformer is converted into a voltage signal through a resistor VR1 and a resistor R6 and then transmitted to the judging circuit. By adjusting the resistance of the resistor VR1 (the resistance between the first end and the second end of the resistor VR 1), the output voltage signal can be adjusted, thereby adjusting the accuracy of the detected current. Specifically, when the resistance of the resistor VR1 is small, the detection is sensitive and accurate, whereas when the resistance of the resistor VR1 is large, the detection sensitivity is low and the accuracy is low.
It can be seen that the electric heating switch control circuit is in a non-enabling state in the electric heating starting process through the intervention of the enabling circuit, and the judging circuit does not participate in the screening of whether the electric heating switch control circuit is normal or not at the moment, so that the judging circuit does not interfere with the starting mechanism of the electric heating, and the electric heating can be started normally. The enabling circuit is in an enabling state when the electric heating stops working, at the moment, the judging circuit participates in screening whether the K1 is normally opened or not, and under the condition that the opening is abnormal due to the adhesion of a switch contact of the K1, the judging circuit cuts off the power connection between an external power supply and the electric heating in a mode of cutting off the K2, so that the phenomenon that the electric heating temperature is too high when the K1 is abnormally cut off is avoided.
Thus far, the technical solution of the present invention has been described in connection with one embodiment shown in the drawings, but it is easily understood by those skilled in the art that the scope of protection of the present invention is not limited to these specific embodiments. Equivalent modifications and substitutions for related technical features may be made by those skilled in the art without departing from the principles of the present invention, and such modifications and substitutions will fall within the scope of the present invention.
Claims (5)
1. An electrical heating start-up control circuit, the start-up control circuit comprising:
1) A switch circuit comprising a first electrically controlled switch and a second electrically controlled switch,
the first electric control switch can be switched between an operating state and a non-operating state of the electric heating,
the electric power connection between the external power supply and the electric heating can be switched by switching the second electric control switch;
2) An enabling circuit for switching to an enabling state in case the first electronically controlled switch is opened;
3) A detection circuit for detecting an electrically heated current signal and converting the current signal into a voltage signal; and
4) The judging circuit is used for comparing the voltage signal input by the detecting circuit with the reference voltage in an enabling state, and switching off the second electric control switch under the condition that the voltage signal is higher than the reference voltage;
the electric heating starting control circuit comprises a controller and a driving circuit, wherein the controller sends a signal capable of switching the working state and the non-working state of electric heating to the first electric control switch through the driving circuit;
wherein the judging circuit comprises a first resistor, a second resistor and a signal comparator,
the first end of the first resistor is connected with the positive electrode of the power supply, the second end of the first resistor is connected with the first end of the second resistor, the first end of the second resistor is also connected with the positive phase input end of the signal comparator, the negative phase input end of the signal comparator is connected with the output end of the detection circuit, and the second end of the second resistor is connected with the analog ground so as to provide reference voltage for the detection circuit through a voltage dividing circuit formed by the first resistor and the second resistor;
the output end of the signal comparator is connected with the control end of the second electric control switch so as to send a signal for switching off the second electric control switch to the control end of the second electric control switch when the voltage signal of the detection circuit is higher than the reference voltage,
the signal comparator is also connected with the output end of the enabling circuit so that the signal comparator is electrified under the condition that the enabling circuit is conducted;
wherein the enabling circuit comprises a first diode, a first triode and a second triode,
the anode of the first diode is connected with the base electrode of the first triode, the cathode of the first diode is respectively connected with the controller and the control end of the first relay, the emitter of the first triode is grounded, the collector of the first triode is connected with the base electrode of the second triode, the emitter of the second triode is connected with the anode of the power supply, so that when the controller sends a signal for closing the first electric control switch to the first electric control switch, the enabling circuit is conducted,
the collector electrode of the second triode is connected with a signal comparator so that the signal comparator is electrified under the condition that the enabling circuit is conducted;
the first triode is an NPN triode, and the second triode is a PNP triode;
the enabling circuit further comprises a second diode and a third diode,
the anode of the second diode is connected with the anode of the first diode, the cathode of the second diode is connected with the anode of the third diode, and the cathode of the third diode is connected with the base electrode of the first triode so as to prevent the base electrode of the first triode from being conducted under the condition that the controller conducts the first electric control switch.
2. The electric heating start control circuit of claim 1, wherein a first end of the first electrically controlled switch is connected to the electric heating, a second end of the first electrically controlled switch is connected to a first end of the second electrically controlled switch, and a second end of the second electrically controlled switch is connected to an external power source, such that:
and the working state of electric heating is switched through the first electric control switch and the second electric control switch, so that the external power supply can supply power to the electric heating under the condition that the first electric control switch and the second electric control switch are closed.
3. The electrical heating start-up control circuit of claim 1, wherein the detection circuit comprises a current transformer, a DC filter and a rectifier,
the current transformer is used for converting the first current detected by the first winding side into the second current at the second winding side, the rectifier is used for rectifying the second current from alternating current to direct current, and the direct current filter is used for filtering a voltage signal corresponding to the direct current before outputting the voltage signal to the judging circuit.
4. An electric heating start-up control circuit as set forth in claim 3, wherein the detection circuit further comprises a third resistor and a fourth resistor,
the first end of the fourth resistor is connected with the positive electrode of the direct current side of the rectifier, the second end of the fourth resistor is connected with the first end of the third resistor, the second end of the third resistor is grounded,
the direct current is converted into a voltage signal through a third resistor and a fourth resistor, the third resistor is an adjustable resistor, and the voltage signal transmitted to the judging circuit is adjusted by adjusting the resistance value of the third resistor, so that the detection precision of the detecting circuit is adjusted.
5. An air conditioner characterized by comprising electric heating configured with the electric heating start control circuit according to any one of claims 1 to 4.
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| CN202110199772.2A CN113038639B (en) | 2021-02-22 | 2021-02-22 | Electric heating switch control circuit and air conditioner with same |
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