CN117440551A - Door detection circuit of microwave oven, detection judging method and microwave oven - Google Patents
Door detection circuit of microwave oven, detection judging method and microwave oven Download PDFInfo
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- CN117440551A CN117440551A CN202210817542.2A CN202210817542A CN117440551A CN 117440551 A CN117440551 A CN 117440551A CN 202210817542 A CN202210817542 A CN 202210817542A CN 117440551 A CN117440551 A CN 117440551A
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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
- H05B6/00—Heating by electric, magnetic or electromagnetic fields
- H05B6/64—Heating using microwaves
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- H05B6/68—Circuits for monitoring or control
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Abstract
The invention provides a door detection circuit of a microwave oven, a detection judging method and the microwave oven, wherein the door detection circuit comprises an alternating current circuit, a voltage doubling rectifying circuit and a control circuit, the alternating current circuit forms on-off control with the voltage doubling rectifying circuit through an interlocking switch group and a microwave heating relay which are arranged in the alternating current circuit, and the control circuit comprises: the first input node group is used for accessing a contact feedback signal of the interlocking switch group; the second input node is used for accessing a contact feedback signal of the microwave heating relay; and the third output node is used for being connected with the detection output module so as to correspondingly output an output signal which is uniquely matched with the set access signal under the normal working condition. The door detection circuit, the detection judging method and the microwave oven solve the defects and the shortcomings of the traditional detection scheme, and realize that the electronic control board can detect the state of the oven door and can detect the working state of the microwave heating relay.
Description
Technical Field
The invention relates to the technical field of cooking appliances, in particular to a door detection circuit of a microwave oven, a detection and judgment method and the microwave oven.
Background
Since the microwave oven can generate high-power microwaves in the working process, the personal safety is endangered by microwave leakage, the microwave oven needs to be strictly ensured to be started in a door closing state, and the microwave oven can be immediately protected or disabled once the magnetron is started under the condition that the oven door is not closed by some measures. It is common practice to meet relevant regulations in product safety standards by providing a number of interlock switches in conjunction with specific conductor set circuits. For the electronic control board, it is required to obtain the opening and closing state of the oven door to control and protect related functions, and it is common practice to separately set a door switch in a designated position of the microwave oven, and introduce a door switch signal into a control circuit of the electronic control board for the door state detection and door opening protection.
The microwave oven needs to control the fire power in the working process, and the common practice is to control the working/non-working time ratio of the magnetron by controlling the on-off time of the microwave heating relay. The microwave heating relay has extremely high working current and extremely high absorption times, and the service life of the contact of the microwave heating relay is limited, so that the failure of the microwave heating relay is one of important factors for limiting the service life of the microwave oven. If the microwave heating relay is in short circuit failure, the microwave oven can lose the fire control function and can only output 100% of full fire; if the microwave heating relay fails to open, the microwave oven will not be able to start the magnetron, i.e. will not be able to heat the food. Aiming at the problem of failure of the microwave heating relay, due to the lack of a feedback mechanism, the control circuit cannot judge whether the microwave heating relay has failed, so that a control panel or a display screen of a product cannot provide any information for early warning, prompting or protection, and a user cannot know that the control panel or the display screen is possibly in the use risk of the product caused by the failure of the microwave heating relay.
Disclosure of Invention
In view of this, the technical problems to be solved by the present invention are: the first aspect is to provide a door detection circuit of a microwave oven, which solves the defects and shortcomings of the traditional detection scheme, and realizes that an electronic control board can detect the state of an oven door and can detect the working state of a microwave heating relay.
In order to solve the technical problem of the first aspect, the present invention provides a door detection circuit of a microwave oven, including an ac circuit, a voltage-multiplying rectifying circuit, and a control circuit, wherein the ac circuit forms on-off control with the voltage-multiplying rectifying circuit through an interlocking switch set and a microwave heating relay disposed therein, and the control circuit includes:
the first input node group is used for accessing a contact feedback signal of the interlocking switch group;
the second input node is used for accessing a contact feedback signal of the microwave heating relay;
and the third output node is used for being connected with the detection output module so as to correspondingly output an output signal which is uniquely matched with the set access signal under the normal working condition.
Preferably, the interlocking switch group includes:
the main interlocking switch is single-pole double-throw and comprises a C1 movable contact, an NC1 stationary contact and an NO1 stationary contact;
a monitoring interlock switch which is single-pole double-throw and comprises a C2 movable contact, an NC2 static contact and an NO2 static contact;
the two-cascade lock switch is single-pole single-throw and comprises a C3 movable contact and a NO3 stationary contact;
the C1 movable contact is connected to the live wire end of the alternating current power supply, the C2 movable contact and the front contact of the microwave heating relay are connected to the NO1 stationary contact through a first parallel wire set, and the NC2 stationary contact and the C3 movable contact are connected to the zero line end of the alternating current power supply through a second parallel wire set.
Preferably, the voltage doubling rectifying circuit comprises a high-voltage transformer, a high-voltage capacitor, a high-voltage diode and a magnetron, wherein a first terminal of the high-voltage transformer is connected with a rear contact of the microwave heating relay, and a second terminal of the high-voltage transformer is connected with a NO3 stationary contact.
Preferably, a magnetron thermal cut-off is provided between the second terminal and the NO3 stationary contact and/or a cavity thermal cut-off is provided between the second parallel conductor set and the neutral terminal of the ac power supply.
Preferably, the first input node group includes a DOOR node, an N node, and an NFS node, where the DOOR node is directly connected to the NC1 stationary contact through a wire, the N node is connected in parallel to the second parallel wire group through a wire to be connected to a zero line end of an ac power supply, and the NFS node is connected to the second terminal to be connected to the NO3 stationary contact through a third parallel wire group.
Preferably, the first terminal and the second input node are connected to the rear contact through a fourth parallel conductor set.
Preferably, the control circuit comprises a photocoupler formed by packaging a light emitting diode and a phototriode, wherein an N node and the second input node are connected in parallel with the anode of the light emitting diode, an NFS node and a DOOR node are connected in parallel with the cathode of the light emitting diode, and the third output node is arranged at the VCC end of the power supply inlet of the phototriode; the first resistor R1, the second resistor R2, the third resistor R3, and the fourth resistor R4 are disposed in one-to-one correspondence: the second input node, the N node, the NFS node, the VCC end power supply inlet and the third output node.
Preferably, the detection output module is further provided with a zero-crossing detection circuit.
The technical problems to be solved by the invention are as follows: the second aspect provides a detection and judgment method of a microwave oven door detection circuit, and/or the third aspect provides a microwave oven, which solves the defects and shortcomings of the traditional detection scheme, and realizes that an electronic control board can detect the state of an oven door and the working state of a microwave heating relay.
In order to solve the above second technical problem, the present invention provides a detection and determination method for a microwave oven door detection circuit, using the door detection circuit according to any one of the embodiments of the first aspect, the detection and determination method includes the following steps: .
S1: judging whether a rectangular wave signal which is opposite to the zero crossing signal can be captured at the third output node;
s2: if yes, judging whether the microwave heating relay is in a non-closed state at the current moment; if not, turning to the step S4;
s3: if yes, judging that the microwave heating relay has failed, wherein the failure mode is contact adhesion;
s4: judging whether the microwave heating relay is in a closed state at the current moment;
s5: if yes, judging that the microwave heating relay and/or the main interlocking switch are/is failed.
In order to solve the technical problem of the third aspect, the invention provides a microwave oven, which is provided with a gate detection circuit according to any embodiment of the first aspect.
Compared with the prior art, the door detection circuit and the detection judgment method of the microwave oven, and the microwave oven have the following beneficial effects:
1) The defects and the shortcomings of the traditional detection scheme are overcome, and the electronic control board can detect the state of the oven door and the working state of the microwave heating relay;
2) The contact signals of the microwave heating relay are fed back to the door switch detection circuit, so that the door detection circuit is also related to the working state of the microwave heating relay, whether the microwave heating relay is invalid or not is sensed, and once the display terminal is invalid, protection and prompt can be immediately made, and the safety and the use convenience of a product are further improved;
3) The output Signal of the gate detection circuit is not a single high-level Signal or low-level Signal, but a rectangular wave Signal, a clear matching relation is arranged between the node N, NFS, DOOR of the Signal input end and the node R1, alternating current is required to be introduced in a specified mode to enable a Signal node in the gate detection circuit to output a preset waveform, after the relevant connecting wire is pulled out, the microwave oven cannot normally work by simply shorting any two or three points of the terminal seat of the terminal, and any failure of key components such as a wire group, an interlocking switch and the like can cause the prompt fault of the microwave oven to be protected, so that the reliability of the gate detection circuit and the overall safety of the microwave oven are further improved.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention. In the drawings:
fig. 1 is a schematic diagram of a wire set and an electric circuit of a microwave oven door detection circuit according to embodiment 1 of the present invention;
FIG. 2 is a schematic diagram of the electrical circuit of FIG. 1 in a normally open oven door condition;
FIG. 3 is a schematic diagram of the circuit configuration of FIG. 1 in a normally closed oven door condition;
FIG. 4 is an equivalent circuit schematic diagram of the control circuit of the electronic control board under FIG. 2;
fig. 5 is a first equivalent circuit diagram of the control circuit of the electronic control board with the microwave heating relay of fig. 3 in an off state;
fig. 6 is a second equivalent circuit diagram of the control circuit of the electronic control board in the on state of the microwave heating relay of fig. 3;
FIG. 7 is a schematic diagram of rectangular wave output of the Signal node of FIG. 4 under its ACL-ACN voltage Signal;
FIG. 8 is a rectangular wave output schematic of the Signal node of FIG. 5 under its ACL-ACN voltage Signal;
fig. 9 is a rectangular wave output schematic diagram of the Signal node of fig. 6 under the ACL-ACN voltage Signal.
Reference numerals illustrate:
1-protective tube, 2-cavity thermal cut-off, 3-magnetron thermal cut-off, 4-high voltage transformer, 41-first terminal, 42-second terminal, 5-high voltage capacitor, 6-high voltage diode, 7-magnetron, 8-microwave heating relay, 81-front contact, 82-back contact, 9-main interlocking switch, 10-monitoring interlocking switch, 11-two cascade locking switch, 12-control circuit.
Detailed Description
In order to make the above objects, technical solutions and advantages of the present invention more comprehensible, the present invention is further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments of the present invention described herein are only some of the embodiments constituting the present invention, which are intended to be illustrative of the present invention and not limiting of the present invention, and the embodiments of the present invention and features of the embodiments may be combined with each other without conflict.
Referring to fig. 1, a wire set and a schematic circuit diagram of a microwave oven door detection circuit according to the present invention are shown. To focus on the key points, some of the common components in the microwave oven (such as turntable motor, oven lamp, barbecue tube, fan, evaporation pan, etc. and related control circuits) are not shown in fig. 1, but do not affect the implementation and description of the present function. In fig. 1:
the voltage doubling rectifying circuit composed of the high-voltage transformer 4, the high-voltage capacitor 5, the high-voltage diode 6 and the magnetron 7 can realize that an AC power supply (usually 120V or 220V) generates high-voltage direct current of about 4000V after high-voltage transformation and voltage doubling rectification so as to drive the magnetron 7 to work. The microwave heating relay 8 is used for controlling the on/off time of the magnetron 7 through a certain on/off ratio during the operation process, so as to realize the fire control, wherein the microwave heating relay 8 can be a VPC relay, for example. The microwave oven must be started up under the condition that the oven door is closed, and the constraint condition is realized by an interlocking switch group consisting of a main interlocking switch 9, a monitoring interlocking switch 10 and a two-cascade locking switch 11, so that the safety of the microwave oven meets the relevant regulations in the product standard. Wherein, cavity thermal cut-off 2 and magnetron thermal cut-off 3 are used for realizing overheat protection, and protective tube 1 is used for short-circuit protection under extreme operating mode.
The central idea of the invention is that: so that the control circuit 12 on the electronic control board will introduce feedback from the microwave heating relay 8 for detecting the operating state of the microwave heating relay 8 in addition to normally introducing a door switch signal for door state detection and door opening protection.
Specifically, under the common cooperation of the wire set, the interlocking switch set and the microwave oven structural design, not only the opening and closing state of the oven door can directly influence the working condition of the control circuit 12, but also the contact signal of the microwave heating relay 8 is fed back to the control circuit 12, so that the detection output result of the control circuit 12 is related to the state information of the oven door and the microwave heating relay 8, and the oven door and the microwave heating relay 8 have a definite unique cooperation relationship under the normal working condition. And when the unique matching relation cannot be corresponded, the corresponding product use risk can be judged, and the microwave oven can give corresponding early warning, prompting or protection on a control panel or a display screen.
Example 1
Referring to fig. 1-9, the invention provides a door detection circuit of a microwave oven, which comprises an alternating current circuit, a voltage doubling rectifying circuit and a control circuit 12, wherein the alternating current circuit forms on-off control with the voltage doubling rectifying circuit through an interlocking switch group and a microwave heating relay 8 which are arranged in the alternating current circuit, and the control circuit 12 comprises:
the first input node group is used for accessing a contact feedback signal of the interlocking switch group;
the second input node is used for accessing a contact feedback signal of the microwave heating relay 8;
and the third output node is used for being connected with the detection output module so as to correspondingly output an output signal which is uniquely matched with the set access signal under the normal working condition.
Specifically, the magnetron 7 is arranged in the voltage doubling rectifying circuit, the oven door is in a closed state in the working process of the microwave oven, the fire power of the microwave oven can be controlled only by controlling the on-off time ratio of the microwave heating relay 8, and the microwave heating relay 8 can have two contact feedback signals under the normal on-off working condition correspondingly. The interlocking switch group is usually composed of a plurality of interlocking switches, and can make interlocking response according to the opening and closing state of the oven door, so as to realize door opening protection through the constraint condition that the microwave oven can start the magnetron 7 under the condition that the oven door is closed, and the interlocking switch group also has two contact feedback signals under the normal constraint condition correspondingly.
In the present invention, the signal input end of the control circuit 12 not only includes the first input node group, but also includes the second input node (corresponding to the R1 node in fig. 1), so that the access signal of the control circuit 12 will be the sum of the oven door opening and closing signal corresponding to the interlocking switch group and the on-off signal of the microwave heating relay 8. Under normal conditions, the predetermined access signal of the control circuit 12 corresponds to the following three situations in total: 1) The oven door is opened, and the microwave heating relay 8 is normally opened; 2) The oven door is closed, and the microwave heating relay 8 is disconnected; 3) The oven door is closed, and the microwave heating relay 8 is closed and conducted. In view of the fact that the contact feedback signals of any one of the interlock switch set and the microwave heating relay 8 directly affect the working condition of the control circuit 12, and further, the detection output module connected with the third output node (corresponding to the node sign in fig. 1) has a detection output result related to the state information of the interlock switch set and the microwave heating relay 8, and only output signals uniquely matched with the predetermined access signals are correspondingly output under normal working conditions, if not, the corresponding product use risk can be determined, for example, the microwave heating relay 8 may be a short-circuit failure under contact adhesion.
Therefore, the door detection circuit of the microwave oven solves the defects and the shortcomings of the traditional detection scheme, and realizes that the electronic control board can detect the state of the oven door and the working state of the microwave heating relay. Furthermore, when the corresponding product use risk is judged, the microwave oven can give corresponding early warning, prompt or protection on a control panel or a display screen of the microwave oven.
Preferably, the interlocking switch group includes:
a main interlock switch 9 which is single-pole double-throw and comprises a C1 movable contact, an NC1 stationary contact and an NO1 stationary contact;
a monitoring interlock switch 10 which is a single pole double throw and includes a C2 movable contact, an NC2 stationary contact, an NO2 stationary contact;
the two-cascade lock switch 11 is single-pole single-throw and comprises a C3 movable contact and a NO3 stationary contact;
wherein, the C1 movable contact is connected with the live wire end of the AC power supply, the C2 movable contact is connected with the front contact 81 of the microwave heating relay 8 through a first parallel wire set to be connected with the NO1 stationary contact, and the NC2 stationary contact is connected with the C3 movable contact through a second parallel wire set to be connected with the zero line end of the AC power supply.
Specifically, the interlocking switch group needs to make an interlocking response according to the opening and closing state of the furnace door so as to realize door opening protection. Specifically, when the oven door is in an open state, the microwave heating relay 8 is normally open, but even if the microwave heating relay 8 is closed due to failure, the voltage doubling rectifying circuit and the alternating current circuit are still in an isolated and disconnected state under the action of the interlocking switch group. And when the oven door is in a closed state, the closing of the microwave heating relay 8 enables the voltage doubling rectifying circuit to be conducted with the alternating current circuit. That is, when the oven door is in different open/close states, even if the microwave heating relay 8 is also closed, the on/off control between the voltage doubler rectifying circuit and the ac circuit will form two distinct operation results.
In the present invention, the interlock switch group is formed by combining two single pole double throw switches and one single pole single throw switch according to a specific structure, wherein the NO2 stationary contact of the monitoring interlock switch 10 may be in a suspended arrangement.
Further:
in the normal open state of the oven door (i.e. NO malfunction or failure of critical components occurs), the three interlock switches and their inner conductor sets will shunt in the manner expressed in fig. 2, at this time, the C1 moving contact of the main interlock switch 9 is closed with the NC1 moving contact and is disconnected with the NO1 moving contact, the C2 moving contact of the monitoring interlock switch 10 is closed with the NC2 moving contact and is disconnected with the NO2 moving contact, and the C3 moving contact of the two-stage lock switch 11 is disconnected with the NO3 moving contact.
In the normal closing state of the oven door (i.e. NO fault or failure of critical components occurs), the three interlock switches and the internal conductor sets thereof are shunted in the manner expressed in fig. 3, at this time, the C1 movable contact of the main interlock switch 9 is disconnected from the NC1 stationary contact and closed with the NO1 stationary contact, the C2 movable contact of the monitoring interlock switch 10 is disconnected from the NC2 stationary contact and closed with the NO2 stationary contact, and the C3 movable contact of the two-stage lock switch 11 is closed with the NO3 stationary contact.
Of course, it should be noted that fig. 2 and fig. 3 are circuit directions of the interlocking switch group when the door of the microwave oven is opened and closed under normal working conditions, respectively, and fig. 2 and fig. 3 do not express details of the voltage doubling rectifying circuit for focusing on the key points. It should be emphasized that the interlocking switch group will normally be switched to a certain designated direction in a coordinated manner according to the opening or closing action of the oven door, and this constraint will usually be guaranteed in the structural design of the microwave oven, and in case of a certain structural damage of the microwave oven, the wire group will still have a certain protection measure. For example, if the main interlock switch 9 and the monitoring interlock switch 10 are not simultaneously switched to the specified uniform direction, a conduction short of C1-NO1-C2-NC2 will be formed in the event of one of them failure, at which time protection can be achieved by blowing the protective tube 1, wherein the protective tube 1 is disposed between the C1 movable contact and the live end of the ac power supply.
Preferably, the voltage doubling rectifying circuit comprises a high-voltage transformer 4, a high-voltage capacitor 5, a high-voltage diode 6 and a magnetron 7, wherein a first terminal 41 of the high-voltage transformer 4 is connected with a rear contact 82 of the microwave heating relay 8, and a second terminal 42 is connected with a NO3 static contact.
Specifically, referring to fig. 1 and 3, when the oven door is normally closed and the microwave heating relay 8 is in a conducting state, the voltage doubling rectifying circuit composed of the high voltage transformer 4, the high voltage capacitor 5, the high voltage diode 6 and the magnetron 7 can realize that an ac power supply (usually 120V or 220V) generates high voltage direct current of about 4000V after high voltage transformation and voltage doubling rectification so as to drive the magnetron 7 to work. More specifically:
in fig. 2, since the two cascade lock switch 11 is turned off, the second terminal 42 of the high voltage transformer 4 is suspended (only connected to the NFS node, as will be further described below); and in fact, under such a wire set and circuit design, the magnetron 7 is not turned on when the oven door is opened unless the main interlock switch 9, the monitoring interlock switch 10, the two cascade lock switch 11, and the microwave heating relay 8 are all simultaneously deactivated (corresponding to fig. 3). Any three failure combinations cannot make the magnetron 7 work, so the safety factor is very high, and after all, the probability that all four key components fail at the same time is very little.
In fig. 3, the first terminal 41 of the high-voltage transformer 4 may be sequentially connected to the live wire end of the ac power supply through the microwave heating relay 8 and the main interlocking switch 9, while the second terminal 42 of the high-voltage transformer 4 may be connected to the zero wire end of the ac power supply through the two cascade lock switches 11, so that the thermal output of the magnetron 7 may be adjusted by controlling the on/off of the microwave heating relay 8. In fact, with this wire set and circuit design, any one of the main interlock switch 9, the monitor interlock switch 10, the two-stage lock switch 11, and the microwave heating relay 8 fails, which may cause the magnetron 7 to be turned on normally.
As a preferred embodiment of the invention, a magnetron thermal breaker 3 is arranged between the second terminal 42 and the NO3 stationary contact and/or a cavity thermal breaker 2 is arranged between the second parallel conductor set and the neutral terminal of the ac power supply.
Preferably, the first input node group includes a DOOR node, an N node, and an NFS node, where the DOOR node is directly connected to the NC1 stationary contact through a wire, the N node is connected in parallel to the second parallel wire group through a wire to be connected to a zero line end of an ac power supply, and the NFS node is connected to the second terminal 42 through a third parallel wire group to be connected to the NO3 stationary contact.
Specifically, the interlocking switch set only has two contact feedback signals of "the oven door is normally opened" and "the oven door is normally closed" under the normal constraint working condition, but when any one interlocking switch in the interlocking switch set fails, the first input node set should also timely feed back the failure change to the control circuit 12, so that the working condition of the control circuit 12 changes, and finally, the failure change of the interlocking switch set and even the failure change information of any one interlocking switch are detected and determined through the consistency comparison of detection output results. In the invention, DOOR nodes, N nodes and NFS nodes are in one-to-one correspondence with the contact feedback of the main interlocking switch 9, the monitoring interlocking switch 10 and the two-cascade locking switch 11.
Preferably, the first terminal 41 and the second input node are connected to the rear contact 82 by a fourth parallel conductor set.
Specifically, under normal conditions, the predetermined access signal of the control circuit 12 corresponds to the following three situations in total: 1) The oven door is opened, and the microwave heating relay 8 is normally opened; 2) The oven door is closed, and the microwave heating relay 8 is disconnected; 3) The oven door is closed, and the microwave heating relay 8 is closed and conducted. Therefore, based on the on-off control of the microwave heating relay 8, the failure condition can also correspond to the following three conditions: 1) The oven door is opened, and the microwave heating relay 8 is normally opened but closed; 2) The oven door is closed, and the microwave heating relay 8 is opened but closed; 3) The oven door is closed, and the microwave heating relay 8 is closed and conducted, but is opened. In the present invention, the second input node should also timely feed back the above three failure situations to the control circuit 12, so that the working condition of the control circuit 12 is changed, and finally, the failure change information of the microwave heating relay 8 is detected and determined by comparing the consistency of the detection output results.
Preferably, the control circuit 12 includes a photo coupler formed by encapsulating a light emitting diode and a phototransistor, an N node and the second input node are connected in parallel to an anode of the light emitting diode, an NFS node and a DOOR node are connected in parallel to a cathode of the light emitting diode, and the third output node is provided at a VCC end of a power supply inlet of the phototransistor; the first resistor R1, the second resistor R2, the third resistor R3, and the fourth resistor R4 are disposed in one-to-one correspondence: the second input node, the N node, the NFS node, the VCC end power supply inlet and the third output node.
Specifically, referring to fig. 4-6, the equivalent circuit diagrams of the control circuit 12 corresponding to three predetermined access signals in a one-to-one manner under normal operation are shown. In the figure, the float mark indicates that the port or connection is in a floating state, ACN and ACL respectively indicate zero and live wires of alternating current, OPT1 indicates a photoelectric coupler, and a Signal node in the block diagram is a third output node which is the output of the oven door detection Signal after isolation and is provided for a later-stage circuit or MCU to use. Specifically, the present invention relates to a method for manufacturing a semiconductor device.
In fig. 2, since the microwave heating relay 8 is normally open when the oven DOOR is opened and the equivalent impedance of the primary winding of the high voltage transformer 4 is relatively very low, one end of the R1 and the other end of the R3 inside the control circuit 12 can be equivalently regarded as being connected together (via the high voltage transformer 4, the magnetron thermal cut-off 3, the NFS node), and the control circuit 12 is connected to the zero line of the alternating current through the N node and the DOOR node, respectively, to obtain power supply. With continued reference to fig. 4, ACL forms a current path with ACN via an optocoupler (OPT 1) inside control circuit 12, a second resistor R2. When the power grid is in the negative half cycle of alternating current, the light emitting diode in the OPT1 is driven to work, so that the phototriode in the OPT1 is conducted, and the Signal isolated from the alternating current power grid is changed into a low level; when the power grid is in the positive half cycle of alternating current, the current direction is inconsistent with the light emitting diode in the OPT1, the OPT1 does not work, the phototriode in the OPT1 is cut off, and the Signal isolated from the alternating current power grid is high level, and the specific reference can be seen in fig. 7. Wherein R3 can equivalently be seen as shorted to R1 and corresponds to a small load placed on OPT1 within control circuit 12 without materially affecting the operating conditions of OPT 1.
In fig. 3, when the oven DOOR is closed, the microwave heating relay 8 may be closed (corresponding to the microwave oven being started and the magnetron 7 being in an operating stage) or opened (corresponding to the microwave oven being either not started or started but just in a fire control stage, and the magnetron 7 being inactive), but the node N should be always connected to ACL and the node DOOR should be always suspended. More specifically:
when the microwave heating relay 8 is turned off, as shown in fig. 5, the NFS node is connected to the ACN and corresponds to the connection to R1, and at this time, the N node, the NFS node, and the second input node are all connected to the ACN, and in this state, the control circuit 12 cannot form a current path, the OPT1 does not operate, and the Signal is pulled up to VCC through R4 and is in a high level state, which can be seen in fig. 8.
When the microwave heating relay 8 is closed, as shown in fig. 6, the second input node is connected to ACL via the microwave heating relay 8 and the main interlock switch 9, and the impedance between the power grid ACL and ACN is lower than that of the primary winding of the high-voltage transformer 4, so that the high-voltage transformer 4 is a load hanging on the ac power grid in this state, and the operation of the control circuit 12 is not affected. For the control circuit 12, ACL will flow back to ACN via the first resistor R1, OPT1, and the third resistor R3 to form a current path. Furthermore, OPT1 will operate in the positive half cycle of the ac grid, where the Signal will be in a low state; otherwise, the OPT1 will not operate in the negative half cycle or zero crossing of the ac power grid, and the Signal will be in a high state, as shown in fig. 9.
In summary, in the three predetermined states of the door opening, the door closing, but the door closing, and the door closing, the microwave heating relay 8 closing, the corresponding relationship diagrams of the ACL-ACN voltage Signal received by the control circuit 12 and the Signal isolated and outputted by the OPT1 are shown in fig. 7-9, respectively, one-to-one.
As a preferred embodiment of the present invention, a diode D1 for protecting the light emitting diode is also installed between the N node and the DOOR node of the control circuit 12.
Specifically, since the reverse withstand voltage of the light emitting diode in the OPT1 is generally low, the diode D1 needs to be added to clamp, and further in fig. 1 or fig. 4, when the alternating current is in the positive half cycle, the reverse bias voltage born by the light emitting diode in the OPT1 is within the safe range.
Preferably, the detection output module is further provided with a zero-crossing detection circuit.
Specifically, by analyzing the voltage waveforms of fig. 7-9, the phase of the Signal node voltage Signal in fig. 7 and 9 is opposite with respect to the phase of the ac grid, although the Signal will have a rectangular wave Signal in both the oven door open, oven door closed, and microwave heating relay 8 closed. By combining the zero-crossing detection circuit and the Signal of the Signal node, it can be determined whether the phase of the Signal is in phase with the zero-crossing Signal, so as to further identify whether the Signal is generated due to the door being opened or whether the Signal is generated due to the door being closed and the microwave heating relay 8 being closed.
The following assumes that the Signal of fig. 7 is in phase with the Zero Signal (Zero-crossing Signal of the Zero-crossing detection circuit), and that the Signal of fig. 9 is in phase with the Zero Signal, and further:
1) If the program end captures the in-phase signal of the rectangular wave of the third output node, the program end can judge that the furnace door is opened, and the control and display terminal of each part can perform function jump and display according to the state that the furnace door is opened;
2) If the program end captures a high-level signal of the third output node, the program end can judge that the oven door is closed and the microwave heating relay 8 is opened;
3) If the program end captures the inverted signal of the rectangular wave of the third output node, the oven door can be judged to be closed and the microwave heating relay 8 is in a closed state;
4) If the program end definitely captures a rectangular wave inverted signal from the third output node when the microwave heating relay 8 is in a non-closed state, judging that the microwave heating relay 8 has failed and the failure mode is contact adhesion;
5) If the program end is clear that microwave heating relay 8 should have been closed but no inverted signal of a rectangular wave is captured from the third output node, it is indicated that microwave heating relay 8 and/or main interlock switch 9 has failed.
Specifically, the microwave heating relay 8 is a necessary condition when the Signal waveform is output in fig. 9, and since the microwave heating relay 8 is controlled by a program, the program itself is very clear what operation state the microwave heating relay 8 should be in.
The contact adhesion is a failure condition which is easy to occur on the microwave heating relay 8, and the front contact 81 and the rear contact 82 of the microwave heating relay 8 are stuck and cannot be separated after the contact adhesion, so that the low-voltage coil loses control capability. Once the microwave heating relay 8 is in contact adhesion, the magnetron 7 outputs 100% of full fire after the microwave oven is closed and started, and the microwave heating relay 8 has a certain danger for a user, but the technical scheme of the application can identify the failure condition of the microwave heating relay 8, so that fault prompt and protection are realized.
Corresponding to the above case 5), the microwave oven may be damaged or destroyed, and the magnetron 7 may not be started all the time, because it may be in an unknown use risk and should not be continuously kept powered on, so that the display terminal may pop up the fault prompt and perform corresponding protection.
Example 2
Referring to fig. 1-9, the present invention further provides a detection determination method for a microwave oven door detection circuit, using the door detection circuit according to any one of the embodiments of the first aspect, where the detection determination method includes the following steps:
s1: judging whether a rectangular wave signal which is opposite to the zero crossing signal can be captured at the third output node;
s2: if yes, judging whether the microwave heating relay 8 is in a non-closed state at the current moment; if not, turning to the step S4;
s3: if yes, judging that the microwave heating relay 8 has failed, wherein the failure mode is contact adhesion;
s4: judging whether the microwave heating relay 8 is in a closed state at the current moment;
s5: if so, it is determined that the microwave heating relay 8 and/or the main interlock switch 9 has failed.
Referring to fig. 1-9, the present invention further provides a microwave oven having a door detection circuit according to any one of the embodiments of the first aspect.
Specifically, it will be understood by those skilled in the art that the detection determination method of the gate detection circuit set forth in embodiment 2 and/or the microwave oven when the gate detection circuit set forth in embodiment 1 is used or has been provided, the solution of the corresponding technical problem and the achievement of the technical effect thereof can be referred to the description of the gate detection circuit set forth in embodiment 1, and will not be described herein again.
Although the present invention is disclosed above, the present invention is not limited thereto. Various changes and modifications may be made by one skilled in the art without departing from the spirit and scope of the invention, and the scope of the invention should be assessed accordingly to that of the appended claims.
Claims (10)
1. The utility model provides a door detection circuit of microwave oven, its characterized in that includes alternating current circuit, doubly voltage rectifying circuit, control circuit (12), alternating current circuit through interlock switch group and microwave heating relay (8) that set up in it with form on-off control between doubly voltage rectifying circuit, control circuit (12) include:
the first input node group is used for accessing a contact feedback signal of the interlocking switch group;
the second input node is used for accessing a contact feedback signal of the microwave heating relay (8);
and the third output node is used for being connected with the detection output module so as to correspondingly output an output signal which is uniquely matched with the set access signal under the normal working condition.
2. The door sensing circuit of a microwave oven as claimed in claim 1, wherein the interlock switch group comprises:
a main interlock switch (9) which is single-pole double-throw and comprises a C1 movable contact, an NC1 stationary contact and an NO1 stationary contact;
a monitoring interlock switch (10) which is a single pole double throw and includes a C2 movable contact, an NC2 stationary contact, and an NO2 stationary contact;
a two-cascade lock switch (11) which is single-pole single-throw and comprises a C3 movable contact and a NO3 stationary contact;
the C1 movable contact is connected to the live wire end of the alternating current power supply, the C2 movable contact is connected to the NO1 fixed contact through a first parallel wire set, and the NC2 fixed contact and the C3 movable contact are connected to the zero line end of the alternating current power supply through a second parallel wire set.
3. The door detection circuit of the microwave oven according to claim 2, wherein the voltage doubling rectifying circuit comprises a high-voltage transformer (4), a high-voltage capacitor (5), a high-voltage diode (6) and a magnetron (7), a first wiring terminal (41) of the high-voltage transformer (4) is connected with a rear contact (82) of the microwave heating relay (8), and a second wiring terminal (42) is connected with a NO3 static contact.
4. A door detection circuit of a microwave oven according to claim 3, characterized in that a magnetron thermal cut-off (3) is arranged between the second terminal (42) and the NO3 stationary contact and/or a cavity thermal cut-off (2) is arranged between the second parallel conductor set and the neutral terminal of the ac power supply.
5. A DOOR sensing circuit of a microwave oven according to claim 3, wherein the first input node group comprises a DOOR node, an N node, and an NFS node, wherein the DOOR node is directly connected to the NC1 stationary contact by wires, the N node is connected in parallel to the second parallel wire group by wires to connect to a zero line terminal of an ac power source, and the NFS node is connected to the NO3 stationary contact by a third parallel wire group with the second terminal (42).
6. A door sensing circuit of a microwave oven according to claim 5, characterized in, that the first terminal (41) and the second input node are connected to the rear contact (82) by a fourth set of parallel conductors.
7. The DOOR detection circuit of a microwave oven according to claim 6, wherein the control circuit (12) comprises a photo coupler formed by packaging a light emitting diode and a phototransistor, an N node and the second input node are connected in parallel to an anode of the light emitting diode, an NFS node and a DOOR node are connected in parallel to a cathode of the light emitting diode, and the third output node is provided at a VCC terminal of a power supply inlet of the phototransistor; the first resistor R1, the second resistor R2, the third resistor R3, and the fourth resistor R4 are disposed in one-to-one correspondence: the second input node, the N node, the NFS node, the VCC end power supply inlet and the third output node.
8. The door sensing circuit of a microwave oven as claimed in any one of claims 1 to 7, wherein the sensing output module is further provided with a zero crossing sensing circuit.
9. A detection decision method of a microwave oven door detection circuit, characterized in that the door detection circuit according to any one of claims 1-8 is used, the detection decision method comprising the steps of:
s1: judging whether a rectangular wave signal which is opposite to the zero crossing signal can be captured at the third output node;
s2: if yes, judging whether the microwave heating relay (8) is in a non-closed state at the current moment; if not, turning to the step S4;
s3: if yes, judging that the microwave heating relay (8) is failed, wherein the failure mode is contact adhesion;
s4: judging whether the microwave heating relay (8) is in a closed state at the current moment;
s5: if yes, the microwave heating relay (8) and/or the main interlocking switch (9) are/is judged to be invalid.
10. A microwave oven comprising a door sensing circuit as claimed in any one of claims 1 to 8.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210817542.2A CN117440551A (en) | 2022-07-12 | 2022-07-12 | Door detection circuit of microwave oven, detection judging method and microwave oven |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210817542.2A CN117440551A (en) | 2022-07-12 | 2022-07-12 | Door detection circuit of microwave oven, detection judging method and microwave oven |
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| CN117440551A true CN117440551A (en) | 2024-01-23 |
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| Application Number | Title | Priority Date | Filing Date |
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| CN202210817542.2A Pending CN117440551A (en) | 2022-07-12 | 2022-07-12 | Door detection circuit of microwave oven, detection judging method and microwave oven |
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| Country | Link |
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| CN (1) | CN117440551A (en) |
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- 2022-07-12 CN CN202210817542.2A patent/CN117440551A/en active Pending
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