CN107436577B - Power control circuit and method based on zero-crossing detection - Google Patents
Power control circuit and method based on zero-crossing detection Download PDFInfo
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- CN107436577B CN107436577B CN201710671513.9A CN201710671513A CN107436577B CN 107436577 B CN107436577 B CN 107436577B CN 201710671513 A CN201710671513 A CN 201710671513A CN 107436577 B CN107436577 B CN 107436577B
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Abstract
The invention relates to a power control circuit and a method based on zero crossing detection, wherein the circuit comprises a power-off reset temperature limiter, a temperature sensor and a temperature sensor, wherein the power-off reset temperature limiter consists of a temperature switch and a PTC resistor which are connected in parallel, and the temperature limiter is connected with a fire wire and a heating device; the power switch is respectively connected with the zero line, the heating device and the micro control unit; the input end of the zero-crossing detection circuit is respectively connected with the heating device and the temperature limiter, the output end of the zero-crossing detection circuit is connected with the micro-control unit, and the zero-crossing detection circuit is used for detecting zero-crossing signals and providing the zero-crossing signals for the micro-control unit; and the micro control unit judges whether the duration time T1 of the zero crossing signal is greater than or equal to a preset threshold value T1, and if not, sends a switch closing signal to control the power switch to be continuously closed. The invention can realize multiplexing of the power switch and improve the safety of the heating appliance.
Description
Technical Field
The invention relates to the technical field of electronics, in particular to a power control circuit and method based on zero crossing detection.
Background
In the prior art, there are many methods for controlling the abnormal state of the heating appliance, for example, the temperature of the heating appliance is simply detected by the NTC sensor, and it is desired to effectively protect the heating circuit in time when the temperature is abnormal, but this method cannot achieve the effect of effectively protecting the heating appliance in time due to the slow self-reaction speed of the NTC sensor.
In the prior art, the function control and protection of the heating appliance are realized by combining a zero-crossing detection mode, a temperature control switch mode and a micro control unit (MicrocontrollerUnit, MCU), but the mode does not consider the problem of how to power off and reset when the temperature controller is abnormal, does not meet the IEC safety certification requirement, and does not consider the multiplexing of components, thereby saving the cost.
Therefore, the power control circuit based on zero crossing detection in the prior art has the problems of at least how to power off and reset when the temperature controller is abnormal, how to reuse components, and the like, so that the cost is saved.
Disclosure of Invention
Aiming at the problems, the invention provides a power control circuit based on zero-crossing detection, which dynamically controls a power switch through a detected zero-crossing signal, so that the power switch can control a heating appliance to work normally when the heating appliance is normal, and can also protect the heating appliance when the circuit is abnormal, thereby realizing multiplexing of the power switch and saving the cost. The invention introduces the power-off reset temperature limiter to solve the problem that the power-off reset is not involved in the prior art, and further improves the safety of the circuit.
The invention provides a power control circuit based on zero crossing detection, which comprises a micro control unit and a heating device, and is characterized in that the circuit further comprises:
the power-off reset temperature limiter is characterized in that two ends of the power-off reset temperature limiter are respectively connected with a live wire and a heating device, and the power-off reset temperature limiter consists of a temperature switch and a PTC resistor which are connected in parallel;
the power switch is respectively connected with the zero line, the heating device and the micro control unit;
the input end of the zero-crossing detection circuit is respectively connected with the heating device and the power-off reset temperature limiter, the output end of the zero-crossing detection circuit is connected with the micro-control unit, and the zero-crossing detection circuit is used for detecting a zero-crossing signal CHECK and providing the zero-crossing signal CHECK for the micro-control unit;
and the micro control unit is used for judging whether the duration time T1 of the zero crossing signal is larger than or equal to a preset threshold value T1, and if not, sending a switch closing signal to control the power switch to be continuously closed.
Further, the micro control unit is configured to determine whether the zero crossing signal is detected within a predetermined period of time and whether the zero crossing signal duration T2 is greater than or equal to a preset threshold T2 after the power switch is controlled to be continuously turned on by the switch on signal, and if the zero crossing signal exists within the predetermined period of time and the zero crossing signal duration T2 is greater than or equal to T2, then the power switch is controlled to be intermittently turned on by the switch off driving signal.
Further, the micro control unit judges whether the duration time T1 of the zero crossing signal is larger than or equal to a preset threshold value T1, and if so, a switch driving signal is sent to control the power switch to be intermittently closed.
Further, the micro control unit sends a drive signal of intermittent closure to the power switch at the zero crossing of the alternating current.
Further, the micro-control unit is further used for judging whether the zero crossing signal is detected within a preset time period and whether the zero crossing signal duration time T2 is greater than or equal to a preset threshold T2 or not after the power switch is controlled to be continuously closed by the switch closing signal, and sending an alarm signal to the alarm unit if the zero crossing signal is not present within the preset time period or the zero crossing signal is present within the preset time period and the zero crossing signal duration time T2 is smaller than the preset threshold T2.
Further, the micro control unit judges whether the duration time T1 of the zero crossing signal is larger than or equal to a preset threshold value T1 after sending the alarm signal, and if so, sends a switch off signal to the power switch.
Further, the micro control unit performs a power-off reset after the power switch is turned off.
Further, the micro control unit judges whether the duration time T1 of the zero crossing signal is larger than or equal to a preset threshold value T1 after sending the alarm signal, and if not, sends a switch continuous closing signal to the power switch.
Further, the control circuit further comprises a thermal fuse link connected between the zero line and the power switch.
Further, the power-off reset temperature limiter, the thermal fuse link and the heating device are arranged on the same heating device bracket.
The invention also provides a power control method applied to the power control circuit based on zero crossing detection, comprising the following steps:
judging whether the duration time T1 of the zero crossing signal is larger than or equal to a preset threshold value T1, and if not, sending a switch closing signal to control the power switch to be continuously closed.
Further, after the switch closing signal is sent to control the power switch to be continuously closed, judging whether the zero crossing signal is detected within a preset time length and whether the zero crossing signal duration time T2 is greater than or equal to a preset threshold T2, and if the zero crossing signal is stored within the preset time length and the zero crossing signal duration time T2 is greater than or equal to T2, sending a switch driving signal to control the power switch to be intermittently closed.
Further, judging whether the duration time T1 of the zero crossing signal is larger than or equal to a preset threshold value T1, and if so, sending a switch driving signal to control the power switch to be intermittently closed.
Further, the micro control unit sends a drive signal of intermittent closure to the power switch at the zero crossing of the alternating current.
Further, after the switch closing signal is sent to control the power switch to be continuously closed, whether the zero crossing signal is detected within a preset time length and whether the zero crossing signal duration time T2 is larger than or equal to a preset threshold T2 is judged, and if the zero crossing signal is not present within the preset time length or the zero crossing signal is present within the preset time length and the zero crossing signal duration time T2 is smaller than the preset threshold T2, an alarm signal is sent to an alarm unit.
Further, after the alarm signal is sent, whether the duration time T1 of the zero crossing signal is larger than or equal to a preset threshold value T1 is judged, and if so, a switch off signal is sent to the power switch.
Further, after the power switch is turned off, a power-off reset is performed.
Further, after the alarm signal is sent, whether the duration time T1 of the zero crossing signal is larger than or equal to a preset threshold value T1 is judged, and if not, a switch continuous closing signal is sent to the power switch.
The technical scheme provided by the embodiment of the invention has the beneficial effects that:
according to the technical scheme, the micro control unit is triggered to send different driving signals to control the power switch to intermittently work or continuously work through judgment of the zero crossing signals, so that multiplexing of the power switch is realized, and the cost of products is saved to a certain extent; the invention also checks the abnormality caused by the fault of the temperature limiter by judging the zero crossing signal for a plurality of times, and can control the complete machine to be powered off and reset through software under the condition that the temperature limiter has abnormal faults, thereby improving the safety of the heating appliance.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly described below, and it is apparent that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of a power control circuit based on zero crossing detection;
FIG. 2 is a circuit diagram of a power-off reset thermostat;
FIG. 3 is a circuit diagram of a first embodiment of a power control circuit based on zero crossing detection;
fig. 4 is a schematic structural diagram of a second embodiment of a power control circuit based on zero crossing detection;
FIG. 5 is a circuit diagram of a second embodiment of a power control circuit based on zero crossing detection;
FIG. 6 is a schematic diagram of a temperature limiter and thermal fuse mounting;
FIG. 7 is a schematic diagram of a zero crossing signal waveform;
FIG. 8 is a schematic diagram of a voltage waveform across a power switch;
fig. 9 is a flow chart of a power control method.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.
Fig. 1 is a schematic structural diagram of a power control circuit based on zero crossing detection according to an embodiment of the present invention. As shown in fig. 1, the circuit comprises a micro control unit, a heating device and the like; also included is a method of manufacturing a semiconductor device,
the power-off reset temperature limiter is respectively connected with a live wire (ACL) and a heating device;
the power switch is respectively connected with a zero line (ACN), a heating device and a micro control unit (namely an MCU unit);
the input end of the zero crossing detection circuit is respectively connected with the heating device and the power-off reset temperature limiter, and the output end of the zero crossing detection circuit is connected with the micro control unit;
the micro control unit is respectively connected with the zero-crossing detection circuit, the power switch and the alarm circuit, and is used for judging whether the duration time T1 of the zero-crossing signal is larger than or equal to a preset threshold value T1 or not, and if not, sending a switch closing signal to control the power switch to be continuously closed.
The circuit structure of the power-off reset temperature limiter is shown in fig. 2, and the power-off reset temperature limiter comprises a temperature switch K1 and a PTC resistor R1 which are connected in parallel. The working principle of the power-off reset temperature limiter is as follows: when the temperature limiter works normally, the temperature switch K1 is closed, and the PTC resistor is short-circuited and does not work; when the temperature limiter works abnormally, the temperature switch K1 is disconnected due to temperature rise, the PTC resistor is connected, and current forms a loop through the PTC resistor, so that the circuit is always kept in an open state. When the total power supply is turned off and the temperature drops to a predetermined recovery temperature, the temperature switch is quickly recovered to be closed. The temperature controller conforming to the safety law is used in the circuit, when the temperature is overheated or dry heating is caused, the reset work can be realized after the power is cut off, namely the power-off reset temperature limiter is applied to small household appliances, the situation that the whole machine cannot be started again after the temperature is overheated can be realized, and the power-off reset is required. For basic parameters of the temperature limiter, such as rated operation temperature, recovery temperature, rated voltage, rated current and the like, the temperature limiter is usually selected in the normal application range in the field, for example, the rated operation temperature is higher, generally more than 100 ℃, the recovery temperature is lower, generally only tens of degrees, and the range is larger, for example, the recovery temperature is 40-60 ℃.
According to the embodiment of the invention, the micro control unit generates different driving signals by judging whether the zero crossing signal output by the zero crossing detection circuit is normal or not. And the power switch correspondingly executes intermittent closing, continuous closing or opening according to the driving signal sent by the MCU unit, so that multiplexing of the power switch is realized.
In the above embodiment of the present invention, the working principle of the specific circuit is shown in fig. 3, where ACL and CAN are input by an ac L line and an ac N line, respectively. The temperature limiter (namely the power-off reset temperature limiter) is respectively connected with the ACL, the heating device HEATER and the zero-crossing detection circuit, wherein CHECK is the input of the zero-crossing detection circuit. The zero-crossing detection circuit requires a large input resistance, and the resistance of the zero-crossing detection circuit connected in parallel with the heating device is required to be approximately equal to the resistance of the heating device. Specific parameters in the circuit can be adjusted according to actual conditions. The power switch TR1 is respectively connected with the ACN and the MCU unit, and the MCU unit controls the power switch TR1 by sending a HEAT signal (i.e. a driving signal).
In the above embodiment of the present invention, when the CHECK signal (i.e., the zero crossing signal) is determined to be normal, the MCU unit sends a HEAT signal to the power switch TR1 (the HEAT signal at this time is defined as a switch driving signal), and the switch driving signal controls the power switch to be intermittently turned on, so that the heating device HEAT in this embodiment works normally.
Wherein, the MCU unit controlling the power switch TR1 to be intermittently closed means that the MCU unit controls the power switch to be turned on or off according to the switch driving signal, thereby precisely controlling the heating power.
In one or more alternative embodiments, chopping, controlling the on period, controlling the on-off of the power switch at zero crossings, and the like may be employed. Preferably, on-off control of the power switch is performed at the zero crossing, so that the influence of switching power loss and electromagnetic interference can be reduced, and the heating power can be accurately controlled.
In the above embodiment of the present invention, in the case where the CHECK signal (i.e., the zero crossing signal) is determined to be abnormal, the MCU unit sends a HEAT signal to the power switch TR1 (at this time, the HEAT signal is defined as a switch-on signal), and the switch-on signal controls the power switch to be continuously turned on. After the MCU unit judges that the CHECK signal is abnormal, the MCU unit controls the power switch TR1 to be continuously closed, so that the heating device HEATER in the circuit is continuously heated. When the heating device HEATER is continuously heated to the temperature of the circuit and rises to the rated action temperature of the temperature limiter, the temperature switch K1 of the temperature limiter is forced to be in an off state, and the PTC resistor is connected to the circuit. At this time, the PTC resistor and the heating device jointly maintain the disconnection state of the temperature limiter, and the heating device is protected through the PTC resistor of the temperature limiter, so that the safety of the circuit is improved.
In the above embodiment of the present invention, the determination of whether the CHECK signal (i.e., the zero-crossing signal) is normal is performed by determining whether the zero-crossing signal duration T1 is equal to or greater than the preset threshold T1. If yes, the method is normal; otherwise, the zero crossing signal is judged to be abnormal.
The setting of the preset threshold t1 is preferable for avoiding erroneous judgment of the MCU unit. Can be set according to the frequency and the period of the alternating current. For example, the alternating current frequency is 50/60HZ, and each period is 20ms/16.7ms, the preset threshold t1 only needs to be larger than the period of the zero crossing signal. As shown in fig. 7, the zero crossing signal acquired by the MCU unit generally coincides with the complete ac input period, start time, inversion time, and end time.
In an alternative embodiment, taking 50HZ as an example, 50 complete zero-crossing square wave signals within 0.1s are defined. For the time limit setting of 0.1s, the erroneous judgment of the MCU unit can be avoided by detecting the zero crossing signal for multiple times.
In an alternative embodiment, the power switch TR1 may be a thyristor, or may be another switching element such as an IGBT, a MOS transistor, or a power transistor.
In the above embodiment of the present invention, in the case where the CHECK signal (i.e., the zero-crossing signal) is judged to be abnormal, a predetermined period of time is further set, and the CHECK signal is detected and judged again within the predetermined period of time. The predetermined time period may be, for example, 5s. Specifically, whether the CHECK signal is detected within a preset time period and whether the duration time T2 of the CHECK signal is larger than or equal to a preset threshold T2 is judged. And if the CHECK signal exists in a preset time length and the duration time T2 of the CHECK signal is greater than or equal to a preset threshold T2, sending the switch driving signal to control the power switch TR1 to be closed intermittently. For the selection of the preset threshold t2, the preset threshold t1 is referred to, for example, t2 is set to 0.5s. . The MCU unit triggers the power switch TR1 to be closed intermittently according to the switch driving signal, so that the heating device HEATER works normally. And the fault cause is detected through the secondary detection zero-crossing signal, so that the working efficiency of the circuit is improved.
In the above embodiment of the present invention, if the CHECK signal does not exist for a predetermined period of time, or the CHECK signal exists for a predetermined period of time and the duration T2 of the CHECK signal is less than the preset threshold T2, an alarm signal is sent to the alarm unit, and the power switch TR1 is still in a continuously closed state. Because the zero-crossing detection circuit has a large input resistance, the heat generating device HEATER is approximately equal to the heat generating device HEATER resistance after being connected in parallel. The heating device HEATER and the PTC resistor R1 are divided, and because the PTC resistor R1 is far larger than the heating device HEATER resistor, the voltage divided by the heating device HEATER is lower, and the zero crossing detection circuit can detect an abnormal zero crossing signal. The PTC resistor R1 continuously generates heat to maintain the temperature switch to be in an off state, and the heating device HEATER also generates heat simultaneously so that the temperature can not reach the upper limit value of the recovery temperature of the temperature limiter. Thereby realizing the protection of the heating device HEATER.
In the embodiment of the invention, the MCU unit sends an alarm signal to the alarm unit to prompt a user to remove faults, for example, the alarm comprises a voice alarm unit for sending out prompt tones or playing pre-stored voice contents to alarm; for example, the alarm comprises an LED unit for emitting light for alarm, such as emitting light with preset color for alarm; for example, the alarm comprises a wireless communication unit for establishing a wireless connection with the user equipment, and sending alarm information to the user equipment via the wireless connection. The wireless communication unit comprises at least one of a WiFi unit, a Bluetooth unit, an NFC unit or a ZigBee unit.
In the above embodiment of the present invention, after sending the alarm signal, it is determined whether the duration T1 of the CHECK signal is greater than or equal to the preset threshold T1. And if yes, sending a switch disconnection signal to the power switch.
At this time, the function of judging the zero crossing signal is to check whether the temperature limiter has abnormal reset, if so, the MCU unit sends a HEAT signal to the power switch TR1 (the HEAT signal is defined as a switch off signal at this time), and the power switch TR1 is turned off according to the switch off signal. Because the temperature limiter is abnormally reset, the heating device HEATER is still in a continuous heating working state, and the circuit is further protected, the whole machine can be controlled to be powered off through software logic, so that the heating device is protected, and the safety of the circuit is improved.
If the judgment is negative, the circuit is not abnormal in resetting of the temperature limiter, and the whole machine is reset through power off.
In an alternative embodiment, as shown in fig. 4, the circuit further comprises a thermal fuse connected between the neutral line and the power switch. The specific working principle is as shown in the circuit structure of fig. 5, when the heating device HEATER works abnormally, and the temperature reaches the fusing temperature of the thermal fuse link, the thermal fuse link is disconnected to cut off the power supply, so that the whole circuit is disconnected with the zero line, and the heating device HEATER is forced to stop heating, thereby realizing the protection of the control circuit.
In an alternative embodiment, as shown in fig. 6, the temperature limiter 2, the thermal link 3 and the heating device 4 are arranged on the same heating device bracket 1, so that the tight installation of the temperature limiter 2, the thermal link 3 and the heating device 4 is realized, and the temperature of the heating device can be effectively and timely reacted, thereby improving the reaction speed of the temperature.
Through the embodiment, the micro control unit is triggered to send different driving signals to control the power switch to work intermittently or continuously by judging the zero crossing signal, so that multiplexing of the power switch is realized. The abnormality caused by the fault of the temperature limiter is detected through multiple judgment of the zero crossing signal, and under the condition that the temperature limiter has abnormal faults, the complete machine can be controlled to be powered off and reset through software, so that the safety of the heating appliance is further improved.
Fig. 9 is a flowchart of a power control method according to an embodiment of the present invention, where the method may be implemented by the power control circuit based on zero crossing detection in the above embodiment. The circuit connection relation of each component in the circuit is shown in fig. 2 and 5.
As shown in fig. 9, the power control method includes:
at the beginning, the zero-crossing detection circuit detects whether the zero-crossing signal is normal or not and sends the judging result to the MCU unit.
Step S901, determining whether the zero crossing signal is normal. The judgment of whether the zero crossing signal is normal is realized by judging whether the duration time T1 of the zero crossing signal is larger than or equal to a preset threshold value T1.
In step S901, if yes, it is normal, and step S902 is continued; otherwise, the zero-crossing signal is judged to be abnormal, and step S906 is continued. The processing mode for judging the abnormality is as follows: judging whether the duration time T1 of the zero crossing signal is larger than or equal to a preset threshold value T1, if not, the MCU sends a switch closing signal to control the power switch to be continuously closed. The zero-crossing signal is used for controlling the power switch to continuously or intermittently work, so that the power switch is not only a switch when a heating appliance works normally, but also a device participating in appliance protection when the operation is abnormal, the multiplexing of the devices is realized, and the product cost is saved.
The setting of the preset threshold t1 is preferable for avoiding erroneous judgment of the MCU unit. For example, according to the frequency and period of the alternating current. If the alternating current frequency is 50/60HZ, and each period is 20ms/16.7ms, the preset threshold t1 only needs to be larger than the period of the zero crossing signal. As shown in fig. 7, the zero crossing signal acquired by the MCU unit generally coincides with the complete ac input period, start time, inversion time, and end time.
In an alternative embodiment, taking 50HZ as an example, 50 complete zero-crossing square wave signals within 0.1s are defined as normal. For the time limit setting of 0.1s, the error judgment of the MCU unit can be avoided by detecting the zero crossing signal for multiple times.
In step S902, the MCU unit sends out a switch driving signal. The switch driving signal is used for controlling the power switch to be intermittently closed, so that the heating device HEATER in the embodiment works normally, and the heating power of the circuit can be accurately controlled.
In one or more alternative embodiments, the switch drive signal may be in the form of chopping, controlling the on period, and command signals extracted at zero crossings, among others. The power switch is controlled to be on-off by the switch driving signal, so that the working efficiency of the heating power lifting circuit can be accurately controlled, and energy sources are effectively saved. The switching control of the power switch is preferably performed at the zero crossing in such a way that switching power losses and the effects of electromagnetic interference are reduced.
In step S903, the power switch performs opening/closing. The power switch performs on-off operation according to a certain rule according to a switch driving signal sent by the MCU unit, so that heating power of the power regulation accurate control circuit is realized, and energy is effectively saved.
Step S904, the heat generating device operates normally. The heating device heats when the power switch is on, and stops heating when the power switch is off.
In step S906, the MCU unit sends a switch-on signal to drive the power switch to be continuously turned on. When the MCU unit judges that the zero crossing signal is abnormal, the MCU unit controls the power switch TR1 to be continuously closed, so that the heating device HEATER in the circuit is continuously heated. When the heating device HEATER is continuously heated to enable the temperature of the circuit to rise to the rated action temperature of the temperature limiter, the temperature switch K1 of the temperature limiter is forced to be in an off state, and the PTC resistor is connected to the circuit. At this time, the PTC electric group and the heating device jointly maintain the disconnection state of the temperature limiter, so that the heating device is protected through the PTC resistor of the temperature limiter, and the safety of the circuit is improved.
In an alternative embodiment, the power switch TR1 may be a thyristor, or may be another switching element such as an IGBT, a MOS transistor, or a power transistor.
Step S907, judging that a normal zero crossing signal is detected within a preset time length, and the duration time T2 of the zero crossing signal is more than or equal to a preset threshold T2, if the judgment result is yes, entering step S902; otherwise, go to S908;
in the above embodiment of the present invention, when the zero-crossing signal is determined to be abnormal, a predetermined period of time is further set, and the CHECK signal is detected for the predetermined period of time to determine whether the zero-crossing signal exists. First, for the setting of the predetermined time period, the selection may be considered according to the time period required for the automatic recovery of the temperature limiter. For example, 5S is selected. Detecting the CHECK signal within a preset time length, and judging whether the CHECK signal duration time T2 is larger than or equal to a preset threshold T2 or not by judging whether the CHECK signal is detected within the preset time length. For the selection of the preset threshold t2, the preset threshold t1 is referred to, for example, t2 is set to 0.5s.
And if the CHECK signal exists in a preset time length and the duration time T2 of the CHECK signal is greater than or equal to a preset threshold T2, sending the switch driving signal to control the power switch TR1 to be closed intermittently. The MCU unit triggers the power switch TR1 to be closed intermittently according to the switch driving signal, so that the heating device HEATER works normally. And the fault cause is detected through the secondary detection zero-crossing signal, so that the working efficiency of the circuit is improved.
Step S908, alarming;
in the above embodiment of the present invention, if the CHECK signal does not exist for a predetermined period of time, or the CHECK signal exists for a predetermined period of time and the duration T2 of the CHECK signal is less than the preset threshold T2, an alarm signal is sent while the power switch TR1 is controlled to be in a continuously closed state.
In the embodiment of the invention, the MCU unit sends an alarm signal to the alarm unit to prompt a user to remove faults, for example, the alarm comprises a voice alarm unit for sending out prompt tones or playing pre-stored voice contents to alarm; for example, the alarm comprises an LED unit for emitting light for alarm, such as emitting light with preset color for alarm; for example, the alarm comprises a wireless communication unit for establishing a wireless connection with the user equipment, and sending alarm information to the user equipment via the wireless connection. The wireless communication unit comprises at least one of a WiFi unit, a Bluetooth unit, an NFC unit or a ZigBee unit.
Step S909, determining whether the zero crossing signal is normal.
In the above embodiment of the present invention, after sending the alarm signal, it is determined whether the duration T1 of the CHECK signal is greater than or equal to the preset threshold T1. If yes, a switch disconnection signal is sent to the power switch; if not, the power-off reset is performed. The circuit problem caused by the abnormal resetting condition of the temperature limiter is detected through the third judgment, and the processing mode after the failure of the temperature limiter is increased, so that the circuit works more safely and reliably.
In step S910, the power switch is turned off.
Judging whether the temperature limiter has abnormal reset or not, if so, the MCU unit sends a HEAT signal to the power switch TR1 (the HEAT signal is defined as a switch-off signal at the moment), and the power switch TR1 is switched off according to the switch-off signal. Because the temperature limiter is abnormally reset, the heating device HEATER is still in a continuous heating working state, and the circuit is further protected, the whole machine can be controlled to be powered off through software logic, so that the heating device is protected, and the safety of the circuit is improved.
If the judgment is negative, the circuit is not abnormal in resetting of the temperature limiter, and the whole machine is reset through power off.
Through the embodiment, the micro control unit is triggered to send different driving signals to control the power switch to work intermittently or continuously by judging the zero crossing signal, so that multiplexing of the power switch is realized. The abnormality caused by the fault of the temperature limiter is detected through multiple judgment of the zero crossing signal, and under the condition that the temperature limiter has abnormal faults, the complete machine can be controlled to be powered off and reset through software, so that the safety of the heating appliance is further improved.
It will be readily appreciated by those of ordinary skill in the art that the preferred embodiments described above can be freely combined and stacked without conflict.
It will be understood that the above-described embodiments are merely illustrative and not restrictive, and that all obvious or equivalent modifications and substitutions to the details given above may be made by those skilled in the art without departing from the underlying principles of the invention, are intended to be included within the scope of the appended claims.
Claims (16)
1. The utility model provides a power control circuit based on zero crossing detection, includes micro control unit and heating device, its characterized in that, the circuit still includes:
the power-off reset temperature limiter is characterized in that two ends of the power-off reset temperature limiter are respectively connected with a live wire and a heating device, and the power-off reset temperature limiter consists of a temperature switch and a PTC resistor which are connected in parallel;
the power switch is respectively connected with the zero line, the heating device and the micro control unit;
the input end of the zero-crossing detection circuit is respectively connected with the heating device and the power-off reset temperature limiter, the output end of the zero-crossing detection circuit is connected with the micro-control unit, and the zero-crossing detection circuit is used for detecting a zero-crossing signal CHECK and providing the zero-crossing signal CHECK for the micro-control unit;
the micro control unit is used for judging whether the duration time T1 of the zero crossing signal is larger than or equal to a preset threshold value T1, and if not, sending a switch closing signal to control the power switch to be continuously closed; after a switch closing signal is sent to control the power switch to be continuously closed, judging whether the zero crossing signal is detected within a preset time length and whether the zero crossing signal duration time T2 is larger than or equal to a preset threshold T2 or not; and if the zero crossing signal exists in the preset time length and the duration time T2 of the zero crossing signal is more than or equal to T2, sending a switch driving signal to control the power switch to be closed intermittently.
2. The circuit of claim 1, wherein the micro-control unit determines whether the duration T1 of the zero-crossing signal is greater than or equal to a preset threshold T1, and if so, sends a switch drive signal to control the power switch to be turned on intermittently.
3. The circuit of claim 2, wherein the micro-control unit sends an intermittently closed drive signal to the power switch at a zero crossing of the alternating current.
4. The circuit of claim 1, further comprising an alarm unit, wherein the micro-control unit determines whether the zero crossing signal is detected within a predetermined time period and whether the zero crossing signal duration T2 is equal to or greater than a preset threshold T2 after sending a switch close signal to control the power switch to be continuously closed; and if the zero crossing signal does not exist in the preset time length or exists in the preset time length and the duration time T2 of the zero crossing signal is smaller than the preset threshold T2, sending an alarm signal to an alarm unit.
5. The circuit according to claim 4, wherein the micro control unit, after transmitting the alarm signal, determines whether the duration T1 of the zero crossing signal is equal to or greater than a preset threshold T1, and if so, transmits a switch-off signal to the power switch.
6. The circuit of claim 5, wherein the micro-control unit performs a power-off reset after the power switch is turned off.
7. The circuit of claim 4, wherein the micro control unit, after sending the alarm signal, determines whether the duration T1 of the zero crossing signal is greater than or equal to a preset threshold T1, and if not, sends a switch continuously closed signal to the power switch.
8. The circuit of any of claims 1-7, wherein the control circuit further comprises a thermal fuse connected between the neutral line and the power switch.
9. The circuit of claim 8, wherein the power-off reset temperature limiter, the thermal fuse, and the heat generating device are disposed on a same heat generating device mount.
10. A power control method applied to the zero-crossing detection-based power control circuit as claimed in any one of claims 1 to 9, characterized in that the power control method comprises:
judging whether the duration time T1 of the zero crossing signal is larger than or equal to a preset threshold value T1, if not, sending a switch closing signal to control the power switch to be continuously closed; after the power switch is controlled to be continuously closed by sending a switch closing signal, judging whether the zero crossing signal is detected within a preset time length and whether the zero crossing signal duration time T2 is larger than or equal to a preset threshold T2, and if the zero crossing signal exists within the preset time length and the zero crossing signal duration time T2 is larger than or equal to T2, sending a switch driving signal to control the power switch to be intermittently closed.
11. The method of claim 10, wherein a determination is made as to whether the duration T1 of the zero crossing signal is greater than or equal to a preset threshold T1, and if so, a switch drive signal is sent to control the power switch to be intermittently closed.
12. The method of claim 11, wherein the micro-control unit sends an intermittently closed drive signal to the power switch at a zero crossing of the alternating current.
13. The method of claim 10, wherein after the power switch is controlled to be continuously closed by sending a switch closing signal, determining whether the zero crossing signal is detected within a predetermined time period and whether the zero crossing signal duration T2 is greater than or equal to a preset threshold T2, and if the zero crossing signal is not present within the predetermined time period or the zero crossing signal is present within the predetermined time period and the zero crossing signal duration T2 is less than the preset threshold T2, sending an alarm signal to an alarm unit.
14. The method according to claim 13, characterized in that after the transmission of the alarm signal, it is determined whether the duration T1 of the zero crossing signal is equal to or greater than a preset threshold T1, and if so, a switch-off signal is transmitted to the power switch.
15. The method of claim 14, wherein a power-off reset is performed after the power switch is turned off.
16. The method according to claim 13, characterized in that after the transmission of the alarm signal, it is determined whether the duration T1 of the zero crossing signal is equal to or greater than a preset threshold T1, and if not, a switch continuous closure signal is transmitted to the power switch.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201710671513.9A CN107436577B (en) | 2017-08-08 | 2017-08-08 | Power control circuit and method based on zero-crossing detection |
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| CN201710671513.9A CN107436577B (en) | 2017-08-08 | 2017-08-08 | Power control circuit and method based on zero-crossing detection |
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| CN107436577A CN107436577A (en) | 2017-12-05 |
| CN107436577B true CN107436577B (en) | 2023-05-23 |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| US5802421A (en) * | 1994-08-26 | 1998-09-01 | Canon Kabushiki Kaisha | Heating and fixing device with AC zero-cross detection circuit |
| JPH10117484A (en) * | 1996-10-08 | 1998-05-06 | Oki Electric Ind Co Ltd | Ac uninterruptive power circuit normally supplied with commercial power |
| JP2007178079A (en) * | 2005-12-28 | 2007-07-12 | Matsushita Electric Ind Co Ltd | Control device for refrigerator |
| CN203935051U (en) * | 2014-04-03 | 2014-11-12 | 浙江绍兴苏泊尔生活电器有限公司 | Heating circuit for soybean milk machine |
| CN106444890B (en) * | 2016-09-08 | 2018-12-28 | 珠海格力电器股份有限公司 | Power control circuit, Poewr control method and temperature detect switch (TDS) condition detection method based on zero passage detection |
| CN106681397B (en) * | 2017-02-22 | 2018-10-30 | 广东美的白色家电技术创新中心有限公司 | Electrical equipment and PTC electric heater control circuit for it |
| CN207851544U (en) * | 2017-08-08 | 2018-09-11 | 珠海格力电器股份有限公司 | A kind of power control circuit based on zero passage detection |
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