CN107027201B - Electromagnetic heating device and noise reduction control method thereof - Google Patents
Electromagnetic heating device and noise reduction control method thereof Download PDFInfo
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- CN107027201B CN107027201B CN201610072354.6A CN201610072354A CN107027201B CN 107027201 B CN107027201 B CN 107027201B CN 201610072354 A CN201610072354 A CN 201610072354A CN 107027201 B CN107027201 B CN 107027201B
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- 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
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Abstract
The invention discloses an electromagnetic heating device and a noise reduction control method thereof, wherein the method comprises the following steps: sampling the working current of the electromagnetic heating device to obtain a current sampling signal; when the PPG is controlled to output a control signal to control a power switch tube in the electromagnetic heating device to be switched on, comparing the current sampling signal with a preset sine wave signal; when the voltage value of the current sampling signal is greater than the same-time voltage instantaneous value corresponding to the preset sine wave signal, the PPG is controlled to be switched off and output so as to adjust the on-time of the power switch tube at each time, so that the waveform envelope of the working current is consistent with the current waveform envelope corresponding to the preset sine wave signal, the frequency characteristic of the working current of the electromagnetic heating device is changed, the frequency characteristic of noise transmitted to a cooker is changed, the heating noise of the cooker is reduced, and the experience of a user is improved.
Description
Technical Field
The invention relates to the technical field of electromagnetic heating, in particular to a noise reduction control method of an electromagnetic heating device and the electromagnetic heating device.
Background
The related electromagnetic heating device such as an induction cooker uses commercial power for power supply, the commercial power is converted into pulsating direct current after being rectified, wherein the pulsating direct current comprises frequency components of fundamental frequency 100Hz and frequency multiplication of each order, the pulsating direct current is further converted into current containing the same frequency components, and the current is finally transmitted to cookware noise through the magnetic field coupling of a wire plate, so that a user feels noisy, and the experience effect is obviously reduced. However, the related art cannot eliminate rectified direct current fundamental wave and harmonic component, and further cannot reduce the noise of the cookware.
Therefore, improvements are needed in the related art.
Disclosure of Invention
The present invention is directed to solving at least one of the problems in the art to some extent. Therefore, an object of the present invention is to provide a noise reduction control method for an electromagnetic heating device, which can achieve the purpose of reducing the heating noise of a pot by changing the waveform of the working current of the electromagnetic heating device.
Another object of the present invention is to provide an electromagnetic heating device.
In order to achieve the above object, an embodiment of the present invention provides a noise reduction control method for an electromagnetic heating device, including the following steps: sampling the working current of the electromagnetic heating device to obtain a current sampling signal; when the PPG is controlled to output a control signal to control a power switch tube in the electromagnetic heating device to be switched on, comparing the current sampling signal with a preset sine wave signal; and when the voltage value of the current sampling signal is greater than the voltage instantaneous value corresponding to the preset sine wave signal at the same moment, controlling the PPG to turn off and output so as to adjust the on-time of the power switch tube each time, so that the waveform envelope of the working current is consistent with the waveform envelope of the current corresponding to the preset sine wave signal.
According to the noise reduction control method of the electromagnetic heating device, the working current of the electromagnetic heating device is sampled to obtain a current sampling signal, the current sampling signal is compared with a preset sine wave signal when the PPG is controlled to output a control signal to control the power switch tube to be switched on, when the voltage value of the current sampling signal is larger than the voltage instantaneous value at the same moment corresponding to the preset sine wave signal, the PPG is controlled to be switched off to output to adjust the switching time of the power switch tube, so that the waveform envelope of the working current is consistent with the waveform envelope of the current corresponding to the preset sine wave signal, the frequency characteristic of the working current of the electromagnetic heating device is changed, the frequency characteristic of noise transmitted to a cooker is changed, the heating noise of the cooker is reduced, and the experience of a user is improved.
According to an embodiment of the present invention, the current sampling signal is compared with a preset sine wave signal by a comparator, wherein when the comparator outputs an inversion signal, the PPG off output may be directly controlled, or the PPG off output may be controlled after delaying a preset time.
According to an embodiment of the present invention, the preset sine wave signal is a sine wave of 2 times of the ac mains frequency.
Further, the pulse width of the control signal output by the PPG in each period of the 2 times alternating current mains frequency sine wave is first increased and then decreased.
The peak value of the sine wave of the 2 times of the alternating current commercial power frequency corresponds to the maximum pulse width, and the valley value of the sine wave of the 2 times of the alternating current commercial power frequency corresponds to the minimum pulse width.
In order to achieve the above object, another embodiment of the present invention provides an electromagnetic heating apparatus, including: the current sampling unit is used for sampling the working current of the electromagnetic heating device to obtain a current sampling signal; a resonant heating unit; the rectification filtering unit is used for carrying out rectification filtering processing on alternating current commercial power and then supplying the alternating current commercial power to the resonance heating unit; the power switch tube is used for controlling the resonance heating unit to perform resonance work; the driving unit is used for driving the power switch tube to be switched on and switched off; the comparison unit is used for comparing the current sampling signal with a preset sine wave signal; and the master control unit is used for controlling the PPG to output a control signal to the drive unit so as to control the power switch tube, and controlling the PPG to switch off and output so as to adjust the on-time of the power switch tube when the voltage value of the current sampling signal is greater than the same instant voltage instantaneous value corresponding to the preset sine wave signal, so that the waveform envelope of the working current is consistent with the waveform envelope of the current corresponding to the preset sine wave signal.
According to the electromagnetic heating device provided by the embodiment of the invention, the current sampling unit is used for sampling the working current of the electromagnetic heating device to obtain a current sampling signal, the main control unit is used for controlling the PPG to output a control signal to control the power switch tube to be switched on and comparing the current sampling signal with a preset sine wave signal, and when the voltage value of the current sampling signal is greater than the voltage instantaneous value at the same moment corresponding to the preset sine wave signal, the PPG is controlled to be switched off and output to adjust the switching-on time of the power switch tube, so that the waveform envelope of the working current is consistent with the current waveform envelope corresponding to the preset sine wave signal, the frequency characteristic of the working current of the electromagnetic heating device is changed, the frequency characteristic of noise transmitted to a cooker is changed, the heating noise of the cooker is reduced, and the experience of a user is improved.
According to an embodiment of the present invention, the comparison unit includes a comparator, wherein when the comparator outputs an inversion signal, the main control unit may directly control the PPG off output, or control the PPG off output after delaying a preset time.
According to an embodiment of the present invention, the preset sine wave signal is a sine wave of 2 times of the ac mains frequency.
Further, the pulse width of the control signal output by the PPG in each period of the 2 times alternating current mains frequency sine wave is first increased and then decreased.
The peak value of the sine wave of the 2 times of the alternating current commercial power frequency corresponds to the maximum pulse width, and the valley value of the sine wave of the 2 times of the alternating current commercial power frequency corresponds to the minimum pulse width.
Drawings
Fig. 1 is a flowchart of a noise reduction control method of an electromagnetic heating apparatus according to an embodiment of the present invention;
fig. 2 is a flowchart of a noise reduction control method of an electromagnetic heating apparatus according to an embodiment of the present invention;
FIG. 3 is a block schematic diagram of an electromagnetic heating apparatus according to an embodiment of the present invention;
fig. 4 is a schematic diagram of an electromagnetic heating device according to an embodiment of the present invention, in which the ac mains power corresponds to the rectified voltage and the waveform and frequency spectrum of the preset sine wave signal;
fig. 5 is a schematic diagram of an electromagnetic heating apparatus ac mains corresponding to the operating current envelope and the waveform of the PPG, according to an embodiment of the present invention; and
fig. 6 is a schematic circuit diagram of an electromagnetic heating apparatus according to an embodiment of the present invention.
Reference numerals:
the device comprises a current sampling unit 10, a rectifying and filtering unit 20, a resonance heating unit 30, a power switch tube Q1, a driving unit 40, a comparing unit 60 and a main control unit 50;
the rectifier bridge stack 201, a filter inductor L1 and a filter capacitor C1;
a resonant inductor L2 and a resonant capacitor C2;
the switching power supply unit 70, the synchronous sampling unit 80 and the human-computer interaction unit 90;
the circuit comprises a comparator U1, a signal providing unit 11, a signal source circuit 101, a gain control circuit 102, a sampling resistor R1 and a current limiting resistor R2.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.
First, a brief description will be given of noise of the electromagnetic heating apparatus in the related art.
In the related art, the electromagnetic heating device is powered by commercial power, and the commercial power is provided to a subsequent circuit after passing through an EMC circuit and a bridge rectifier circuit in the electromagnetic heating device. The inventor finds that: the commercial power passes through bridge rectifier circuit and can become the pulsation direct current that contains hundreds of hertz's alternating current composition by original 50Hz single-frequency alternating current, and wherein, pulsation direct current mainly includes 100 ~ 500Hz low order harmonic, and after the follow-up circuit that the pulsation direct current provided electromagnetic heating device, electromagnetic heating device's operating current also had the low order harmonic of the same frequency simultaneously to finally transmit the pan noise on, make the pan noise have the low order harmonic of the same frequency. The distribution can make the user feel noisy at the low-order harmonic noise of 100-500 Hz, so that noise is generated in the heating process of the cookware, and the user experience effect is obviously reduced.
Based on this, the embodiment of the invention provides a noise reduction control method for an electromagnetic heating device and an electromagnetic heating device for implementing the method.
A noise reduction control method of an electromagnetic heating apparatus and an electromagnetic heating apparatus proposed according to an embodiment of the present invention are described below with reference to the accompanying drawings.
Wherein, electromagnetic heating device for example electromagnetism stove is used for carrying out resonance heating to the pan. As shown in fig. 3, the electromagnetic heating apparatus may include a current sampling unit 10, a rectifying and filtering unit 20, a resonant heating unit 30, a power switching tube (e.g., IGBT) Q1, a driving unit 40, a comparing unit 60, and a main control unit 50. Wherein, the alternating current provided by the alternating current power supply is converted into pulsating direct current after passing through an EMC (Electro Magnetic Compatibility) circuit and a rectifying and filtering unit 20; the rectifying and smoothing unit 20 supplies the pulsating direct current to the resonance heating unit 30; the main control unit 50 is used for controlling the driving unit 40 to drive the power switch tube Q1 to be switched on and off through the driving unit 40; the resonant heating unit 30 generates resonance in the process of switching on and off the power switch tube Q1, and generates a periodically changing magnetic field, which acts on the bottom of the pot to generate eddy current and heat at the same time. Therefore, the heating of the pot is realized.
Fig. 1 is a flowchart of a noise reduction control method of an electromagnetic heating apparatus according to an embodiment of the present invention. As shown in fig. 1, the noise reduction control method of the electromagnetic heating apparatus includes the steps of:
s1: the working current of the electromagnetic heating device is sampled to obtain a current sampling signal.
That is to say, during the heating process of the electromagnetic heating device, the current sampling unit may sample the operating current of the electromagnetic heating device to obtain the current sampling signal. The current sampling signal may be a current peak value or a current average value, which is specifically determined by the frequency characteristic of the current sampling unit.
It should be noted that, according to different current sampling requirements, the sampling mode and the sampling position may be different, for example, for the sampling position, the current may be collected at the emitter of each power switch tube, or may be collected between the rectifier circuit and the filter circuit in the rectifier and filter unit 20; for example, for the sampling mode, resistance sampling, current transformer sampling, or hall element sampling may be, but is not limited to.
S2: when a PPG (Programmable Pulse Generator) is controlled to output a control signal to control a power switch tube in the electromagnetic heating device to be switched on, the current sampling signal is compared with a preset sine wave signal.
According to an embodiment of the present invention, as shown in fig. 4 and 5, the preset sine wave signal may be a sine wave of 2 times of the ac mains frequency, and the ac mains is subjected to zero-crossing detection to obtain a zero-crossing point, and the preset sine wave signal and the ac mains may have the following phase relationship: the wave trough of the preset sine wave signal corresponds to the zero crossing point of the alternating current commercial power. More specifically, the preset sine wave signal may be 1/2 sine wave signal with positive offset amplitude, and the frequency of the preset sine wave signal is 2 times of the mains frequency, for example, 100Hz, and the phase of the preset sine wave signal is the same as the phase of the ac mains; the amplitude of the preset sine wave signal can be adjusted according to the heating power requirement, and it should be noted that the current signal types are different, and the corresponding amplitudes of the preset sine wave signal are different when the heating power is the same.
Specifically, the pulse width of the control signal output by the PPG in each period of the sine wave of 2 times the ac mains frequency is first increased and then decreased. In other words, the pulse width of the control signal output by the PPG in each half-wave period of the ac mains is first increased and then decreased, that is, the value of the pulse width of the control signal output by the PPG in each half-wave period of the ac mains is not a constant value. The pulse width refers to a time length for which the power switch tube, for example, an IGBT, is turned on under the control of the control signal output by the PPG.
More specifically, the peak value of the sine wave of 2 times the ac mains frequency corresponds to the maximum pulse width, and the valley value of the sine wave of 2 times the ac mains frequency corresponds to the minimum pulse width.
In an example of the present invention, the signal source of the preset sine wave signal may be an independent signal synchronized with the ac mains, or a fundamental frequency signal extracted from the rectified pulsating dc, or an analog sine wave signal obtained by the D/a conversion function of the main control unit. It should be understood that, due to the nonlinearity of the actual circuit, the predetermined sine wave signal is still allowed to contain a certain harmonic component, and the harmonic amount of the predetermined sine wave signal varies greatly according to different circuits, and the embodiment of the present invention is not limited in particular.
In addition, the amplitude of the preset sine wave signal is determined by the output amplitude of the signal source and the gain control circuit, the gain of the gain control circuit is determined by the main control unit according to the heating power requirement, or the amplitude of the preset sine wave signal is directly determined by the D/A conversion function of the main control unit.
S3: when the voltage value of the current sampling signal is larger than the voltage instantaneous value corresponding to the preset sine wave signal at the same moment, the PPG turn-off output is controlled to adjust the on-time of the power switch tube each time, so that the waveform envelope of the working current is consistent with the waveform envelope of the current corresponding to the preset sine wave signal.
It should be noted that, in conjunction with the schematic diagram of the variation curve of the operating current in fig. 5, the solid line in fig. 5 represents the waveform of the current flowing through the current sampling unit in the forward direction in the resonance period, i.e., the actual waveform of the operating current, and the dotted line in fig. 5 represents the curve of the current peak value varying with time, i.e., the waveform envelope of the operating current.
That is, the current sampling signal is compared with a preset sine wave signal to generate a comparison result, and the time length of the control signal output by the PPG at each time is determined according to the comparison structure.
In the related art, with a fixed PPG pulse width, the on-time of the power switch tube is fixed, and the voltage frequency characteristic of the pulsating direct current converted from the alternating current can be transmitted to the frequency characteristic of the operating current of the electromagnetic heating device, for example, the pulsating direct current includes harmonics of 100Hz, 200Hz, 300Hz, …, which will cause the frequency characteristic of the operating current to also include harmonics of 100Hz, 200Hz, 300Hz, …, and finally transmitted to the cooker noise, so that the cooker noise has low harmonics of the same frequency.
In the embodiment of the present invention, as shown in fig. 4 and 5, in the process of controlling the electromagnetic heating device to heat, the working current of the electromagnetic heating device is sampled to obtain a current sampling signal, the current sampling signal is compared with a preset sine wave signal when the power switch tube is turned on, and then when the voltage value of the current sampling signal reaches the voltage instantaneous value at the same time corresponding to the preset sine wave signal, the PPG is controlled to turn off and output to control the power switch tube to turn off, so as to adjust each turn-on time of the power switch tube in the electromagnetic heating device, so as to change the frequency characteristic of the working current of the electromagnetic heating device, for example, to make the waveform envelope of the working current approach to a sine wave of 2 times of the ac mains frequency, thereby preventing each harmonic energy from being transmitted to the noise of the cookware, and thus reducing the heating noise of the cookware.
Specifically, as shown in fig. 2, the noise reduction control method according to the embodiment of the present invention specifically includes the following steps:
s101: and after the synchronous signal is acquired, the PPG is controlled to output a control signal so as to control the power switch tube to be switched on.
S102: the working current of the electromagnetic heating device is sampled to obtain a current sampling signal.
S103: and judging whether the voltage value of the current sampling signal is greater than the voltage instantaneous value Vref corresponding to the preset sine wave signal at the same moment.
If yes, step S104 is executed: if not, the process continues to step S103.
S104: and controlling the PPG turn-off output to control the power switch tube to be turned off, and returning to the step S101.
According to an embodiment of the present invention, the current sampling signal is compared with a preset sine wave signal by a comparator, wherein when the comparator outputs an inversion signal, the PPG off output may be directly controlled, or the PPG off output may be controlled after a preset time delay.
Specifically, the current sampling signal may be input to a first input terminal of the comparator, and a preset sine wave signal may be provided to a second input terminal of the comparator, when a voltage value Vi of the current sampling signal reaches a voltage instantaneous value Vref of the preset sine wave signal, an output signal Isense of the comparator is inverted, and at this time, it may be determined that the working current reaches a shutdown control value, and PPG is controlled to be shut down and output.
When the output signal Isense of the comparator is turned over, the PPG can be immediately controlled to be turned off and output, and the PPG can also be controlled to be turned off and output after the preset time is delayed, so that the PPG can be controlled in a software mode after the preset time is delayed, the applicability is improved, and the design of a gain control circuit of a preset sine wave signal is simplified.
According to a specific example of the present invention, the power switch may be an IGBT, and the operating current of the electromagnetic heating device may be an emitter current of the IGBT. Therefore, after the PPG is controlled to output a control signal, the current of the emitting electrode of the IGBT is gradually increased, the voltage value of the current sampling signal is correspondingly increased and is input to the first input end of the comparator, when the voltage value of the current sampling signal is larger than the voltage instantaneous value Vref corresponding to the preset sine wave signal at the same moment, the comparator is turned over, and the PPG can be directly controlled to be turned off and output through a hardware circuit or the PPG can be indirectly controlled to be turned off and output through a program. The above process realizes primary current control.
When 1/2 alternating current commercial power cycle is completed, 1 complete waveform control is completed, the waveform envelope of the working current is equivalent to the current waveform envelope corresponding to the preset sine wave signal, therefore, when the preset sine wave signal is a sine wave with 2 times of alternating current commercial power frequency and smaller harmonic amount, the noise transmitted to the cooker is only 2 times of alternating current commercial power frequency and smaller other harmonic components, compared with the noise generated by a fixed PPG output mode in the related technology, the harmonic amount is obviously reduced, the noise is correspondingly reduced, and the preset sine wave signal can be an envelope formed by a group of corresponding current waveform data which is most suitable for actual use conditions and is obtained through experimental data.
In summary, according to the noise reduction control method of the electromagnetic heating apparatus of the embodiment of the present invention, the working current of the electromagnetic heating apparatus is sampled to obtain the current sampling signal, the current sampling signal is compared with the preset sine wave signal when the PPG is controlled to output the control signal to control the power switch tube to be turned on, and when the voltage value of the current sampling signal is greater than the voltage instantaneous value at the same time corresponding to the preset sine wave signal, the PPG is controlled to turn off the output to adjust the turn-on time of the power switch tube, so that the waveform envelope of the working current is consistent with the waveform envelope of the current corresponding to the preset sine wave signal, thereby changing the frequency characteristic of the working current of the electromagnetic heating apparatus, further changing the frequency characteristic of the noise transmitted to the pot, reducing the heating noise of the pot, and improving the experience of the user.
The embodiment of the invention also provides an electromagnetic heating device adopting the method.
Fig. 3 is a block schematic diagram of an electromagnetic heating apparatus according to an embodiment of the present invention. As shown in fig. 3, the electromagnetic heating apparatus includes: the device comprises a current sampling unit 10, a rectifying and filtering unit 20, a resonant heating unit 30, a power switch tube Q1, a driving unit 40, a comparison unit 60 and a main control unit 50.
The current sampling unit 10 is configured to sample an operating current of the electromagnetic heating apparatus to obtain a current sampling signal. The current sampling signal may be a current peak value or a current average value, which is specifically determined by the frequency characteristic of the current sampling unit. It should be noted that, according to different current sampling requirements, the sampling mode and the sampling position of the current sampling unit 10 may be different, for example, for the sampling position, the current sampling unit 10 may collect current at the emitter of each power switching tube, or may collect current between the rectifying circuit and the filter circuit in the rectifying and filtering unit 20; for example, for the sampling mode, the current sampling unit 10 may be, but is not limited to, a resistance sampling, a current transformer sampling, or a hall element sampling.
The rectification filtering unit 20 is used for performing rectification filtering processing on the alternating current mains supply and supplying the rectified alternating current mains supply to the resonance heating unit 30; the power switch tube Q1 is used for controlling the resonant heating unit 30 to perform resonant operation; the driving unit 40 is used for driving the power switch Q1 to be turned on and off. In an embodiment of the present invention, as shown in fig. 3, the power switch Q1 may be an IGBT, the rectifier and filter unit 20 includes a rectifier bridge stack 201, a filter inductor L1 and a filter capacitor C1, and the resonant heating unit 30 includes a resonant inductor L2 and a resonant capacitor C2 connected in parallel.
The comparing unit 60 is configured to compare the current sampling signal with a preset sine wave signal; the main control unit 50 is configured to control the PPG to output a control signal to the driving unit 40 to control the power switch tube Q1, and control the PPG to turn off and output to adjust each on time of the power switch tube Q1 when the voltage value of the current sampling signal is greater than the voltage instantaneous value at the same time corresponding to the preset sine wave signal, so that the waveform envelope of the working current is consistent with the current waveform envelope corresponding to the preset sine wave signal. That is, the comparison unit 60 compares the current sampling signal with a preset sine wave signal to generate a comparison result, and the main control unit 50 determines the time length of the control signal output by the PPG each time according to the comparison structure.
It should be noted that, in conjunction with the schematic diagram of the variation curve of the operating current in fig. 5, the solid line in fig. 5 represents the waveform of the current flowing through the current sampling unit in the forward direction in the resonance period, i.e., the actual waveform of the operating current, and the dotted line in fig. 5 represents the curve of the current peak value varying with time, i.e., the waveform envelope of the operating current.
As shown in fig. 3, the electromagnetic heating apparatus further includes a switching power supply unit 70, a synchronous sampling unit 80, a human-computer interaction unit 90, and the like, wherein the switching power supply unit 70 is configured to convert an ac power supply into a dc power supply with a first voltage, for example, 5V, and a dc power supply with a second voltage, for example, 18V, where the dc power supply with the first voltage is provided to the main control unit 50, the dc power supply with the second voltage is provided to the driving unit 40, and the first voltage is smaller than the second voltage; the synchronous sampling unit 80 is configured to detect voltages at two ends of the resonant inductor L2, compare the voltages at two ends of the resonant inductor L2 to generate a synchronous signal, and after obtaining the synchronous signal, the main control unit 50 controls the PPG to output a control signal to the power switch tube Q1; the human-computer interaction unit 90 is used for receiving instructions input by a user and displaying the instructions to the user.
Specifically, after acquiring the synchronization signal, the main control unit 50 controls the PPG to output a control signal to control the power switch tube Q1 to be turned on, and during the turn-on period of the power switch tube Q1, the current sampling unit 10 samples the working current of the electromagnetic heating device to obtain a current sampling signal, and then the main control unit 50 determines whether the voltage value I of the current sampling signal is greater than the voltage instantaneous value Vref at the same time corresponding to a preset sine wave signal, and if I is greater than Vref, controls the PPG to turn off and output to control the power switch tube Q1 to turn off, and detects the synchronization signal: if I is less than or equal to Vref, then continue to judge whether I is greater than Vref.
In the related art, under the condition that the PPG pulse width is fixed, the on-time of the power switch Q1 is fixed, and the voltage frequency characteristic of the pulsating direct current converted from the alternating current can be transmitted to the frequency characteristic of the operating current of the electromagnetic heating device, for example, the pulsating direct current includes harmonics of 100Hz, 200Hz, 300Hz, …, which will cause the frequency characteristic of the operating current to also include harmonics of 100Hz, 200Hz, 300Hz, …, and finally transmitted to the noise of the cookware, so that the noise of the cookware has low harmonics of the same frequency.
In the embodiment of the present invention, as shown in fig. 4 and 5, in controlling the electromagnetic heating apparatus to perform heating, the working current of the electromagnetic heating device is sampled by the current sampling unit 10 to obtain a current sampling signal, and the main control unit 50 compares the current sampling signal with a preset sine wave signal when the power switch Q1 is turned on, when the voltage value of the current sampling signal reaches the voltage instantaneous value corresponding to the preset sine wave signal at the same moment, the PPG is controlled to be turned off and output so as to control the power switch tube to be turned off, thereby adjusting each turn-on time of a power switch tube in the electromagnetic heating device, changing the frequency characteristic of the working current of the electromagnetic heating device, for example, enabling the waveform envelope of the working current to be close to a sine wave of 2 times of the alternating current commercial power frequency, thereby avoiding the harmonic energy of each time from all transmitting to the noise of the cookware, and reducing the heating noise of the cookware.
According to an embodiment of the present invention, as shown in fig. 4 and 5, the preset sine wave signal may be a sine wave of 2 times of the ac mains frequency, and the ac mains is subjected to zero-crossing detection to obtain a zero-crossing point, and the preset sine wave signal and the ac mains may have the following phase relationship: the wave trough of the preset sine wave signal corresponds to the zero crossing point of the alternating current commercial power. More specifically, the preset sine wave signal may be 1/2 sine wave signal with positive offset amplitude, and the frequency of the preset sine wave signal is 2 times of the mains frequency, for example, 100Hz, and the phase of the preset sine wave signal is the same as the phase of the ac mains; the amplitude of the preset sine wave signal can be adjusted according to the heating power requirement, and it should be noted that the current signal types are different, and the corresponding amplitudes of the preset sine wave signal are different when the heating power is the same.
Specifically, the pulse width of the control signal output by the PPG in each period of the sine wave of 2 times the ac mains frequency is first increased and then decreased. In other words, the pulse width of the control signal output by the PPG in each half-wave period of the ac mains is first increased and then decreased, that is, the value of the pulse width of the control signal output by the PPG in each half-wave period of the ac mains is not a constant value. The pulse width refers to a time length for which the power switch tube, for example, an IGBT, is turned on under the control of the control signal output by the PPG.
More specifically, the peak value of the sine wave of 2 times the ac mains frequency corresponds to the maximum pulse width, and the valley value of the sine wave of 2 times the ac mains frequency corresponds to the minimum pulse width.
In an example of the present invention, the signal source of the preset sine wave signal may be an independent signal synchronized with the ac mains, or a fundamental frequency signal extracted from the rectified pulsating dc, or an analog sine wave signal obtained by the D/a conversion function of the main control unit. It should be understood that, due to the nonlinearity of the actual circuit, the predetermined sine wave signal is still allowed to contain a certain harmonic component, and the harmonic amount of the predetermined sine wave signal varies greatly according to different circuits, and the embodiment of the present invention is not limited in particular.
According to an embodiment of the present invention, as shown in fig. 4 to 6, the comparing unit 60 includes a comparator U1, wherein when the comparator U1 outputs the flipping signal, the main control unit 50 may directly control the PPG off output, or control the PPG off output after delaying a preset time.
It should be noted that the comparator U1 may be a comparator integrated inside the main control unit 50, or may be a comparator separately provided outside the main control unit 50.
Specifically, a first input terminal of the comparator U1 may be connected to the current sampling unit 10 for receiving the current sampling signal, a second input terminal of the comparator U2 may be connected to the signal providing unit 70 for providing the preset sine wave signal, and an output terminal of the comparator U2 is connected to the main control unit 50. When the voltage value Vi of the current sampling signal reaches the voltage instantaneous value Vref of the preset sine wave signal, the output signal Isense of the comparator U1 is inverted, and at this time, the main control unit 50 can judge that the working current reaches a turn-off control value and control PPG to turn off and output.
When the output signal Isense of the comparator is inverted, the main control unit 50 can immediately control the PPG to be turned off and output, and the main control unit 50 can also delay the preset time and then control the PPG to be turned off and output, so that the PPG is turned off after the preset time is delayed, and the PPG can be controlled in a software manner, thereby improving the applicability and simplifying the design of the gain control circuit of the preset sine wave signal.
According to an embodiment of the present invention, as shown in fig. 6, the signal providing unit 11 for providing a preset sine wave signal includes: a signal source circuit 101 and a gain control circuit 102.
The signal source circuit 101 is configured to obtain rectified pulsating direct current at an output end of the rectifier bridge stack 201, and filter the pulsating direct current to obtain a fundamental frequency signal from the rectified pulsating direct current, so as to obtain a sine wave with a small harmonic amount; the gain control circuit 102 is configured to adjust the amplitude of the extracted fundamental frequency signal to obtain a preset sine wave signal. Specifically, the specific circuit structure and connection relationship between the signal source circuit 101 and the gain control circuit 102 are shown in fig. 6, and are not described here again.
It should be noted that the amplitude of the preset sine wave signal is determined by the output amplitude of the signal source circuit 101 and the gain control circuit 102, and the gain of the gain control circuit 102 can be determined by the main control unit 50 according to the heating power requirement, or the amplitude of the preset sine wave signal is directly determined by the D/a conversion function of the main control unit 50.
According to an embodiment of the present invention, as shown in fig. 4-6, the power switch may be an IGBT, and the current sampling circuit 10 includes a sampling resistor R1 and a current limiting resistor R2, wherein one end of the sampling resistor R1 is connected to an emitter of the IGBT, and the other end of the sampling resistor R1 is grounded; one end of the current limiting resistor R2 is connected with one end of the sampling resistor R1, and the other end of the current limiting resistor R2 is connected with the first input end of the comparator U1.
In connection with the example of fig. 6, the control process of the main control unit 50 is as follows: after the PPG is controlled to output a control signal, the emitter current of the IGBT is gradually increased, the divided voltage obtained by the sampling resistor R1 is correspondingly increased, the divided voltage value of the sampling resistor R1 is input to the first input end of the comparator U1 through the current limiting resistor R2, when the divided voltage value of the sampling resistor R1 is greater than the voltage instantaneous value Vref at the same moment corresponding to the preset sine wave signal, the output signal of the comparator U1 is inverted, and after the main control unit 50 receives the inverted signal, the PPG can be directly controlled to be turned off and output through a hardware circuit, or the PPG can be indirectly controlled to be turned off and output through a program. The above process realizes primary current control.
When 1/2 alternating current commercial power cycle is completed, 1 complete waveform control is completed, the waveform envelope of the working current is equivalent to the current waveform envelope corresponding to the preset sine wave signal, therefore, when the preset sine wave signal is a sine wave with 2 times of alternating current commercial power frequency with smaller harmonic quantity, the noise transmitted to the cooker is only 2 times of alternating current commercial power frequency and other small harmonic components, compared with the noise generated by a fixed PPG output mode in the related technology, the harmonic quantity is obviously reduced, and the noise is correspondingly reduced.
In some embodiments of the present invention, the electromagnetic heating device may be an induction cooker, an electromagnetic rice cooker or an electromagnetic pressure cooker.
In summary, according to the electromagnetic heating apparatus of the embodiment of the present invention, the current sampling unit samples the working current of the electromagnetic heating apparatus to obtain the current sampling signal, the main control unit compares the current sampling signal with the preset sine wave signal when controlling the PPG to output the control signal to control the power switch tube to be turned on, and when the voltage value of the current sampling signal is greater than the voltage instantaneous value at the same time corresponding to the preset sine wave signal, the main control unit controls the PPG to turn off and output to adjust the on time of the power switch tube, so that the waveform envelope of the working current is consistent with the waveform envelope of the current corresponding to the preset sine wave signal, thereby changing the frequency characteristic of the working current of the electromagnetic heating apparatus, further changing the frequency characteristic of the noise transmitted to the pot, reducing the heating noise of the pot, and improving the experience of the user.
In the description of the present invention, it is to be understood that the terms "central," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," "circumferential," and the like are used in the orientations and positional relationships indicated in the drawings for convenience in describing the invention and to simplify the description, and are not intended to indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and are therefore not to be considered limiting of the invention.
Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.
In the present invention, unless otherwise expressly stated or limited, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can, for example, be fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; they may be directly connected or indirectly connected through intervening media, or they may be connected internally or in any other suitable relationship, unless expressly stated otherwise. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
In the present invention, unless otherwise expressly stated or limited, the first feature "on" or "under" the second feature may be directly contacting the first and second features or indirectly contacting the first and second features through an intermediate. Also, a first feature "on," "over," and "above" a second feature may be directly or diagonally above the second feature, or may simply indicate that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature may be directly under or obliquely under the first feature, or may simply mean that the first feature is at a lesser elevation than the second feature.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.
Claims (10)
1. A noise reduction control method of an electromagnetic heating device is characterized by comprising the following steps:
sampling the working current of the electromagnetic heating device to obtain a current sampling signal;
when the PPG is controlled to output a control signal to control a power switch tube in the electromagnetic heating device to be switched on, comparing the current sampling signal with a preset sine wave signal;
and when the voltage value of the current sampling signal is greater than the voltage instantaneous value corresponding to the preset sine wave signal at the same moment, controlling the PPG to turn off and output so as to adjust the on-time of the power switch tube each time, so that the waveform envelope of the working current is consistent with the waveform envelope of the current corresponding to the preset sine wave signal.
2. The noise reduction control method of an electromagnetic heating apparatus according to claim 1, wherein the current sampling signal is compared with a preset sine wave signal by a comparator, wherein,
when the comparator outputs an overturning signal, the PPG is directly controlled to be output in a turn-off mode, or the PPG is controlled to be output in a turn-off mode after a preset time is delayed.
3. The noise reduction control method of an electromagnetic heating apparatus according to claim 1, wherein the preset sine wave signal is a sine wave of 2 times of an ac commercial power frequency.
4. The noise reduction control method of the electromagnetic heating apparatus according to claim 3, wherein a pulse width of the control signal output by the PPG in each period of the sine wave of the 2 times alternating current mains frequency is first increased and then decreased.
5. The noise reduction control method of the electromagnetic heating apparatus according to claim 4, wherein a peak value of the sine wave of the 2 times alternating current mains frequency corresponds to a maximum pulse width, and a valley value of the sine wave of the 2 times alternating current mains frequency corresponds to a minimum pulse width.
6. An electromagnetic heating device, comprising:
the current sampling unit is used for sampling the working current of the electromagnetic heating device to obtain a current sampling signal;
a resonant heating unit;
the rectification filtering unit is used for carrying out rectification filtering processing on alternating current commercial power and then supplying the alternating current commercial power to the resonance heating unit;
the power switch tube is used for controlling the resonance heating unit to perform resonance work;
the driving unit is used for driving the power switch tube to be switched on and switched off;
the comparison unit is used for comparing the current sampling signal with a preset sine wave signal;
and the master control unit is used for controlling the PPG to output a control signal to the drive unit so as to control the power switch tube, and controlling the PPG to switch off and output so as to adjust the on-time of the power switch tube when the voltage value of the current sampling signal is greater than the same instant voltage instantaneous value corresponding to the preset sine wave signal, so that the waveform envelope of the working current is consistent with the waveform envelope of the current corresponding to the preset sine wave signal.
7. The electromagnetic heating device according to claim 6, wherein the comparison unit comprises a comparator, and wherein when the comparator outputs an inversion signal, the master control unit directly controls the PPG off output or controls the PPG off output after delaying for a preset time.
8. Electromagnetic heating device according to claim 6, characterized in that said predetermined sine wave signal is a sine wave of 2 times the AC mains frequency.
9. The electromagnetic heating apparatus according to claim 8, wherein the pulse width of the control signal output by the PPG becomes larger and smaller in each period of the sine wave of the 2 times ac mains frequency.
10. An electromagnetic heating device according to claim 9, wherein the peak value of the sine wave of the 2 times ac mains frequency corresponds to a maximum pulse width and the valley value of the sine wave of the 2 times ac mains frequency corresponds to a minimum pulse width.
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| CN109561531B (en) * | 2017-09-25 | 2021-04-20 | 佛山市顺德区美的电热电器制造有限公司 | Electromagnetic heating equipment and driving control device and method of power switch tube of electromagnetic heating equipment |
| CN110944420B (en) * | 2018-09-21 | 2021-12-14 | 深圳市鑫汇科股份有限公司 | Electromagnetic heating device and heating control method thereof |
| CN109358537A (en) * | 2018-09-30 | 2019-02-19 | 珠海格力电器股份有限公司 | Reduce control system, the control method, cooking apparatus of electromagnetic cooking appliance noise |
| CN114698166B (en) * | 2020-12-29 | 2023-06-16 | 佛山市顺德区美的电热电器制造有限公司 | Electromagnetic heating apparatus, noise suppressing method, heating control system, and storage medium |
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| TWI581668B (en) * | 2011-12-20 | 2017-05-01 | Panasonic Corp | Microwave heating device |
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