CN112770429A - Electromagnetic induction heating device - Google Patents
Electromagnetic induction heating device Download PDFInfo
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- CN112770429A CN112770429A CN201911111699.8A CN201911111699A CN112770429A CN 112770429 A CN112770429 A CN 112770429A CN 201911111699 A CN201911111699 A CN 201911111699A CN 112770429 A CN112770429 A CN 112770429A
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- 238000010438 heat treatment Methods 0.000 title claims abstract description 155
- 230000005674 electromagnetic induction Effects 0.000 title claims abstract description 104
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- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 14
- 229910052742 iron Inorganic materials 0.000 claims description 7
- 239000010963 304 stainless steel Substances 0.000 claims description 6
- 229910000589 SAE 304 stainless steel Inorganic materials 0.000 claims description 6
- 239000010965 430 stainless steel Substances 0.000 claims description 5
- 102100031785 Endothelial transcription factor GATA-2 Human genes 0.000 description 24
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B6/00—Heating by electric, magnetic or electromagnetic fields
- H05B6/02—Induction heating
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B6/00—Heating by electric, magnetic or electromagnetic fields
- H05B6/02—Induction heating
- H05B6/10—Induction heating apparatus, other than furnaces, for specific applications
- H05B6/12—Cooking devices
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Abstract
The invention provides an electromagnetic induction heating device comprising a pot detection mode and a heating mode. The electromagnetic induction heating device comprises a power supply generating unit, a pulse generating unit, a resonance unit, a current detecting unit, a phase detecting unit and a control unit. The control unit controls the pulse generating unit to generate a first pulse width modulation signal with a preset detection frequency in the pot detection mode, and the control unit determines whether to control the pulse generating unit to generate a second pulse width modulation signal with a preset working frequency according to a first time width between a negative edge of the first pulse width modulation signal and a first current signal generated by the current detection unit, so that the electromagnetic induction heating device is switched from the pot detection mode to the heating mode.
Description
Technical Field
The present invention relates to an electromagnetic induction heating device, and more particularly, to an electromagnetic induction heating device with a pot detection function.
Background
In some conventional electromagnetic ovens, the pot is detected by sending an excitation pulse to the resonant circuit and then counting the number of inductive pulses of the resonant circuit to determine whether the pot is placed thereon. However, the aforementioned detection method is easily interfered by noise (noise) to cause erroneous determination, which affects the user experience.
Furthermore, traditional electromagnetism stove can not judge the material of pan, all uses same set of heating control parameter to the pan of different materials, if the user uses the pan that does not contain iron or iron content is few, can lead to electromagnetic induction heating device can't heat the pan, or can't reach the maximum heating power of electromagnetism stove. If the maximum heating power of the induction cooker cannot be reached, the problem that the internal circuit of the induction cooker generates heat seriously is caused, so that the whole system is unstable in operation, and the service life of the electromagnetic induction heating device is shortened.
Furthermore, when the conventional induction cooker judges whether the cookware is moved away in the heating process, at least one mains supply period is needed to judge whether the cookware is moved away, the time required for judgment is longer, and the conventional pot moving judgment mode is easily influenced by the work of the induction cooker, so that misjudgment is easy to occur. If misjudgment occurs, namely after the cooker is moved away, the power output of the induction cooker is not closed, and the temperature of the internal circuit is rapidly increased. If the user puts the pot back suddenly, the internal circuit will generate strong instantaneous current, which will cause the internal circuit to generate heat seriously and even damage the induction cooker.
Disclosure of Invention
The invention aims to provide an electromagnetic induction heating device, in particular to an electromagnetic induction heating device with a cooker detection function.
In one embodiment, the electromagnetic induction heating apparatus includes a power input terminal, a power generating unit, a pulse generating unit, a resonating unit, a current detecting unit, a phase detecting unit, and a control unit. The power input end receives an alternating current power supply. The power generation unit generates a DC power according to the AC power. The pulse generating unit generates a first pulse width modulation signal with a preset detection frequency in a pot detection mode after the electromagnetic induction heating device is electrified and started. The resonant unit is coupled between the power generation unit and the pulse generation unit, and generates a resonant current in the pot detection mode according to the direct-current power supply. The current detection unit is coupled to the resonance unit and generates a first current signal according to the resonance current. The phase detection unit is coupled with the pulse generation unit and the current detection unit, and detects the negative edge of the first pulse width modulation signal and the negative edge of the first current signal in the pot detection mode. The control unit is coupled with the phase detection unit and the pulse generation unit, controls the pulse generation unit to generate a first pulse width modulation signal in the pot detection mode, calculates a first time width between a negative edge of the first pulse width modulation signal and a negative edge of the first current signal, and determines whether to control the pulse generation unit to generate a second pulse width modulation signal with a preset working frequency or not according to the first time width so that the electromagnetic induction heating device is switched from the pot detection mode to the heating mode.
The invention is described in detail below with reference to the drawings and specific examples, but the invention is not limited thereto.
Drawings
FIG. 1 is a schematic circuit diagram illustrating an embodiment of an electromagnetic induction heating apparatus according to the present invention operating in a pot detection mode;
FIG. 2 is a schematic circuit diagram of another embodiment of an electromagnetic induction heating apparatus according to the present invention operating in a heating mode;
FIG. 3 is a waveform diagram of the PWM signal and the current signal generated by the electromagnetic induction heating apparatus of FIGS. 1 and 2;
FIG. 4 is a flowchart illustrating a pot detection method of an electromagnetic induction heating apparatus according to an embodiment of the present invention;
FIG. 5 is a flow chart of an embodiment of the pot detection method of FIG. 4;
fig. 6 is a flowchart illustrating a pot detection method in a heating mode of an electromagnetic induction heating apparatus according to an embodiment of the present invention.
Wherein the reference numerals
100 power input terminal
1001 positive terminal
1002 negative terminal
101 power supply generating unit
1011 rectifying unit
1012 filtering unit
102 pulse generating unit
103 switch unit
1031 first switch
1032 second switch
104 resonant unit
1041 first capacitor
1042 second capacitance
1043 coil
105 current detection unit
1051 sensing circuit
1052 switching circuit
106 phase detection unit
107 control unit
110 commercial power zero point detection unit
C01 first Current Signal
C02 second Current Signal
C03 third Current Signal
C04 fourth Current Signal
GATA1 first pulse width modulation signal
GATA2 second pulse width modulation signal
GATA3 third PWM signal
GATA4 fourth PWM signal
S1 control signal
S2 zero crossing detection signal
First time width of T1
T2 second time Width
N1 first connection point
N2 second connection Point
S01-S05 steps
S031-S033 steps
S041-S042 step
S07-S12 steps
Detailed Description
The invention will be described in detail with reference to the following drawings, which are provided for illustration purposes and the like:
fig. 1 and 2 are schematic circuit diagrams illustrating an electromagnetic induction heating apparatus according to an embodiment of the present invention operating in a pot detection mode and a heating mode, respectively. After the electromagnetic induction heating device is powered on and started, the electromagnetic induction heating device firstly enters a pot detection mode, and the electromagnetic induction heating device detects whether a pot is placed on the electromagnetic induction heating device. After a pot is arranged on the electromagnetic induction heating device, the electromagnetic induction heating device is switched from a pot detection mode to a heating mode so as to heat the pot and food materials in the pot.
Referring to fig. 1 and 2, the electromagnetic induction heating apparatus includes a power generating unit 101, a resonant unit 104, a pulse generating unit 102, a current detecting unit 105, a phase detecting unit 106, and a control unit 107. The resonant unit 104 is coupled between the power generating unit 101 and the pulse generating unit 102, and the pulse generating unit 102 is coupled to the control unit 107. The current detection unit 105 is coupled to the resonance unit 104 and the phase detection unit 106. The phase detection unit 106 is coupled between the pulse generation unit 102 and the control unit 107, and is coupled between the current detection unit 105 and the control unit 107.
The power generating unit 101 generates a direct current power according to which the resonance unit 104 resonates to generate a resonance current. The current detection unit 105 generates a current signal C01 (hereinafter referred to as a first current signal C01) according to a resonance current generated by the resonance unit 104 in the pot detection mode.
The pulse generating unit 102 is controlled by a control unit 107. In the pot detection mode, as shown in fig. 1, the Pulse generating unit 102 can generate a Pulse Width Modulation (PWM) signal GATA1 (hereinafter referred to as a first Pulse Width Modulation signal GATA1) with a predetermined detection frequency under the control of a control signal S1 sent by the control unit 107; as shown in fig. 2, in the heating mode, the pulse generating unit 102 may generate a pulse width modulation signal GATA2 (hereinafter, referred to as a second pulse width modulation signal GATA2) with a preset operating frequency under the control of the control signal S1 sent by the control unit 107.
The phase detection unit 106 receives the first current signal C01 generated by the current detection unit 105 and receives the first pwm signal GATA1 generated by the pulse generation unit 102 in the pot detection mode. The phase detection unit 106 detects the negative edge of the first pwm signal GATA 1. When the phase detecting unit 106 detects the negative edge of the first pulse-width modulation signal GATA1, the phase detecting unit 106 detects the negative edge of the first current signal C01 to generate a time width T1 (hereinafter referred to as a first time width T1) between the negative edge of the first pulse-width modulation signal GATA1 and the negative edge of the first current signal C01, as shown in fig. 3.
In operation, referring to fig. 1 to 4, fig. 4 is a flowchart of a pot detection method of an electromagnetic induction heating apparatus according to an embodiment of the present invention. In the pot detection mode, the control unit 107 controls the pulse generating unit 102 to generate the first pulse width modulation signal GATA1 with the preset detection frequency (step S01), the control unit 107 calculates a first time width T1 between a negative edge of the first pulse width modulation signal GATA1 and a negative edge of the first current signal C01 (step S02), the control unit 107 determines whether a pot is placed thereon according to the first time width T1 (step S03), to determine whether to control the pulse generating unit 102 to generate the second pulse width modulation signal GATA2 with the predetermined operating frequency (step S04), that is, when the control unit 107 determines that the existing pot is placed thereon (yes), the control unit 107 controls the pulse generating unit 102 to generate the second pulse width modulation signal GATA2, so that the electromagnetic induction heating apparatus is switched from the pot detection mode to the heating mode. Therefore, the invention can prevent the electromagnetic induction heating device from working in an unstable state because the electromagnetic induction heating device is powered on when no pan is placed.
In one embodiment, the electromagnetic induction heating apparatus further comprises a power input terminal 100, and the power input terminal 100 may have a positive terminal 1001 and a negative terminal 1002. The power input terminal 100 is coupled to the power generating unit 101, and the power generating unit 101 is coupled between the power input terminal 100 and the resonant unit 104. The power input terminal 100 can receive an ac power from an external power source, and the power generating unit 101 can receive the aforementioned ac power from the power input terminal 100 and convert the ac power to generate a dc power, so that the resonant unit 104 generates a resonant current.
Furthermore, the electromagnetic induction heating apparatus further includes a zero point detection unit 110, the zero point detection unit 110 is coupled to the positive terminal 1001 and the negative terminal 1002 of the power input terminal 100, and the zero point detection unit 110 is coupled between the power input terminal 100 and the control unit 107. The zero point detecting unit 110 may detect a zero-crossing point (zero-crossing) of an ac power source (i.e., commercial power) and generate a zero-crossing detection signal S2, the zero point detecting unit 110 may transmit the zero-crossing detection signal S2 to the control unit 107, and the control unit 107 counts a preset time length from the zero-crossing point according to the zero-crossing detection signal S2, so that the commercial power reaches a peak value. The predetermined time period may be 5ms for an AC power source with a frequency of 50Hz, or 4.17ms for an AC power source with a frequency of 60 Hz. In the pot detection mode, the control unit 107 performs step S02 to calculate the first time width T1 at a predetermined time point when the mains power reaches the peak value.
Furthermore, in step S03, the control unit 107 converts the first time width T1 into a phase angle (hereinafter referred to as a first phase angle), the control unit 107 compares the first phase angle with a predetermined angle (hereinafter referred to as a first predetermined angle), and the control unit 107 determines whether to perform step S04 according to the comparison result. In detail, the control unit 107 calculates a ratio between the first time width T1 and the cycle time of the first pwm signal GATA1 (the cycle time of the first pwm signal GATA1 and the predetermined detection frequency are reciprocal), the control unit 107 multiplies 360 degrees by the ratio to calculate a first phase angle (step S031), the control unit 107 then determines whether the first phase angle is smaller than a first predetermined angle (step S032), when the first phase angle is smaller than the first predetermined angle (yes), indicating that the existing pot is placed in the electromagnetic induction heating device, the control unit 107 controls the pulse generating unit 102 to generate the second pulse width modulation signal GATA2 (step S04), so that the electromagnetic induction heating device operates according to the second pulse width modulation signal GATA2 to heat the pot and the food material in the pot.
For example, taking the first time width T1 and the cycle time of the first pwm signal GATA1 as 6 μ S and 33 μ S, respectively, the control unit 107 calculates the first phase angle of 65 degrees by multiplying 360 degrees by the ratio of 0.18 between 6 μ S and 33 μ S in step S031, and if the first preset angle is 82 degrees, the control unit 107 determines in step S032 that the first phase angle of 65 degrees is smaller than the first preset angle of 82 degrees (yes), and the control unit 107 controls the pulse generating unit 102 to generate the second pwm signal GATA2 (step S04).
In one embodiment, in step S032, when the control unit 107 determines that the first phase angle is greater than the first predetermined angle (no), for example, the first phase angle is 90 degrees, which indicates that no pot is placed in the electromagnetic induction heating apparatus, the control unit 107 may control the electromagnetic induction heating apparatus to be turned off (step S05). Alternatively, in another embodiment, the control unit 107 may wait for a predetermined time period, for example, one minute, the control unit 107 controls the pulse generating unit 102 to continue generating the first pwm signal GATA1 within one minute (step S01), the control unit 107 calculates the first time width T1 between the negative edge of the first pwm signal GATA1 and the negative edge of the first current signal C01 when the utility power reaches the peak value within one minute (step S02), and calculates the first phase angle (step S031), and the control unit 107 determines whether the first phase angle is smaller than the first predetermined angle (step S032). If the control unit 107 does not determine that the first phase angle is smaller than the first preset angle within one minute, the control unit 107 starts to control the electromagnetic induction heating device to be turned off (step S05).
Therefore, the invention detects whether the cookware is arranged on the phase angle detection device or not by the phase angle detection device, compared with the prior art, the detection method is less susceptible to noise interference and less prone to occurrence of misjudgment, and the detection method has higher detection accuracy and improves the use experience of users.
In an embodiment, as shown in fig. 1 and fig. 2, the resonant unit 104 includes a first capacitor 1041, a second capacitor 1042, and a coil 1043, and the coil 1043 may be implemented by an inductor. The first capacitor 1041 is coupled to the second capacitor 1042. One end of the coil 1043 is coupled to a first connection point N1 between the first switch 1031 and the second switch 1032, and the other end of the coil 1043 is coupled to a second connection point N2 between the first capacitor 1041 and the second capacitor 1042, that is, the coil 1043 is coupled between the first connection point N1 and the second connection point N2. Accordingly, during the operation of the pwm signals GATA1, GATA2 and other pwm signals, the coil 1043 resonates, and when the first switch 1031 and the second switch 1032 are alternately turned on, the coil 1043 oscillates alternately with the first capacitor 1041 and the second capacitor 1042 according to the dc power generated by the power generating unit 101, so that the resonant unit 104 generates a resonant current.
Furthermore, the electromagnetic induction heating apparatus may further include a switch unit 103, wherein the switch unit 103 is coupled between the resonance unit 104 and the pulse generating unit 102. The switch unit 103 receives the pwm signal generated by the pulse generating unit 102, and the pwm signal is used as a switch control signal for turning on or off the switch unit 103. For example, in the pot detection mode, the switch unit 103 is turned on according to the high level of the first pwm signal GATA1, and in the heating mode, the switch unit 103 is turned on according to the high level of the second pwm signal GATA 2. The resonance unit 104 may generate a resonance current according to the dc power when the switching unit 103 is turned on.
In one embodiment, in step S05, the control unit 107 may control the pulse generating unit 102 to generate a pulse width modulation signal (i.e., a zero level signal) with a duty cycle (duty cycle) of zero, so as to control the switch unit 103 to be turned off to turn off the electromagnetic induction heating device.
In an embodiment, when the pot is placed in the electromagnetic induction heating device, in step S03, the control unit 107 further determines the material of the pot according to the first phase angle, and controls the lower limit of the preset operating frequency of the pwm signal generated by the pulse generating unit 102 in the heating mode according to the material of the pot, since the preset operating frequency of the pwm signal is inversely proportional to the heating power of the electromagnetic induction heating device. In detail, referring to fig. 1 to 5 together, when the control unit 107 determines that the first phase angle is smaller than the first predetermined angle in step S032 (yes), the control unit 107 further determines whether the first phase angle is smaller than another predetermined angle (hereinafter referred to as a second predetermined angle) (step S033).
When the first phase angle is greater than the second predetermined angle (i.e. the first phase angle is located between the first predetermined angle and the second predetermined angle) (no), it indicates that the pot is made of iron or 430 stainless steel, at this time, the control unit 107 controls the pulse generating unit 102 to generate the second pulse width modulation signal GATA2 with a preset working frequency in the heating mode to reach a lower limit frequency value corresponding to the maximum heating power of the electromagnetic induction heating device (step S042), i.e. the preset working frequency is greater than or equal to the lower limit frequency value, i.e. the electromagnetic induction heating device can heat the pot made of iron or 430 stainless steel with the maximum heating power; on the other hand, when the first phase angle is smaller than the second predetermined angle (i.e. the first phase angle is smaller than the first predetermined angle and smaller than the second predetermined angle) (yes), it indicates that the material of the pot is 304 stainless steel, at this time, the control unit 107 controls the pulse generating unit 102 to generate the second pulse width modulation signal GATA2 with the preset operating frequency being greater than the lower limit frequency value in the heating mode (step S041), that is, the electromagnetic induction heating device heats the pot made of 304 stainless steel with a smaller heating power.
Therefore, the problem that the electromagnetic induction heating device cannot reach the maximum heating power due to the pot made of 304 stainless steel can be avoided, and the problem that the switch unit 103 and the coil 1043 seriously generate heat due to the fact that the electromagnetic induction heating device cannot reach the maximum heating power can be avoided, so that the service life of the electromagnetic induction heating device is shortened due to unstable operation of the system.
In one embodiment, a designer of the electromagnetic induction heating apparatus may design the control unit 107 to control the pulse generating unit 102 to generate a predetermined detection frequency of 30KHz, and respectively place pots made of 430 stainless steel, iron, or 304 stainless steel on the electromagnetic induction heating apparatus, and the designer may calculate the corresponding first phase angle by the control unit 107 according to the pots made of different materials, and accordingly set the first predetermined angle and the second predetermined angle. For example, the first phase angle calculated by the control unit 107 according to the pot made of 430 stainless steel or iron is in the range of 70 degrees to 80 degrees, and the first phase angle calculated by the control unit 107 according to the pot made of 304 stainless steel is in the range of 60 degrees to 70 degrees. Here, the first predetermined angle may be 82 degrees, the second predetermined angle may be 70 degrees, and the control unit 107 may determine the material of the pot according to the first predetermined angle of 82 degrees and the second predetermined angle of 70 degrees to generate the corresponding control signal S1 to control the pulse generating unit 102.
In one embodiment, in the heating mode, the electromagnetic induction heating apparatus has a pan movement detection function, and the control unit 107 can determine whether the pan is moved away from the electromagnetic induction heating apparatus, so as to determine whether to control the electromagnetic induction heating apparatus to switch from the heating mode to the pan detection mode or to control the electromagnetic induction heating apparatus to be turned off. In detail, as shown in fig. 2, the current detecting unit 105 can further generate a current signal C02 (hereinafter referred to as a second current signal C02) according to the resonant current generated by the resonant unit 104 in the heating mode, and in the heating mode, when the operating frequency of the second pwm signal GATA2 is greater than the predetermined detection frequency (for example, the operating frequency and the predetermined detection frequency are 40KHz and 30KHz, respectively, and the operating frequency of 40KHz is greater than the predetermined detection frequency of 30 KHz), the control unit 107 determines whether to control the electromagnetic induction heating apparatus to leave the heating mode according to the current value of the second current signal C02.
Referring to fig. 1 to fig. 3 and fig. 6, in the heating mode, when the operating frequency of the second pwm signal GATA2 is greater than the predetermined detection frequency, the control unit 107 determines whether the current difference between the second current signals C02 generated by the current detection unit 105 at two previous time points is greater than a predetermined difference (step S11), and when the current difference is greater than the predetermined difference (yes), it indicates that the pot is removed from the electromagnetic induction heating apparatus, and at this time, the control unit 107 controls the electromagnetic induction heating apparatus to switch from the heating mode to the pot detection mode or to turn off the electromagnetic induction heating apparatus (step S12); when the current difference is smaller than the predetermined difference (no), it indicates that the pot is not removed from the electromagnetic induction heating apparatus, and at this time, the control unit 107 controls the electromagnetic induction heating apparatus to continue operating in the heating mode (step S10) without controlling the electromagnetic induction heating apparatus to change its operating mode.
On the other hand, in the heating mode, when the operating frequency of the second pwm signal GATA2 generated by the pulse generating unit 102 is less than or equal to the predetermined detecting frequency (for example, the operating frequency and the predetermined detecting frequency are 25KHz and 30KHz, respectively, and the operating frequency of 25KHz is less than the predetermined detecting frequency of 30 KHz), the control unit 107 determines whether the pot is removed from the electromagnetic induction heating apparatus according to the time width T2 (hereinafter, referred to as the second time width T2) between the negative edge of the second pwm signal GATA2 and the negative edge of the second current signal C02 in the heating mode, so as to determine whether to control the electromagnetic induction heating apparatus to change its operating mode.
In detail, in the heating mode, as shown in fig. 3 and 6, the phase detecting unit 106 further detects a negative edge of the second pwm signal GATA2 and a negative edge of the second current signal C02, the control unit 107 calculates a second time width T2 between the negative edge of the second pwm signal GATA2 and the negative edge of the second current signal C02 when the commercial power reaches the peak value in the heating mode (step S07), calculates a phase angle (hereinafter referred to as a second phase angle) according to a ratio between the second time width T2 and a cycle time of the second pwm signal GATA2 (for example, the cycle time of the second pwm signal GATA2 having an operating frequency of 25KHz is 40 μ S) (step S08), the control unit 107 determines whether the second phase angle is smaller than a first preset angle (step S09), when the second phase angle is smaller than the first preset angle (the determination result is yes), indicating that the pot is not removed from the electromagnetic induction heating device, at this time, the control unit 107 controls the electromagnetic induction heating device to continue to operate in the heating mode (step S10) without controlling the electromagnetic induction heating device to change its operation mode; when the second phase angle is greater than or equal to the first predetermined angle (no), indicating that the pot is removed from the electromagnetic induction heating apparatus, the control unit 107 controls the electromagnetic induction heating apparatus to switch from the heating mode to the pot detection mode or controls the electromagnetic induction heating apparatus to turn off (step S12). The computations of steps S07 and S08 are described in detail before, and are not described herein again.
Therefore, the pot moving detection function can avoid the problem that the coil 1043 and the switch unit 103 are likely to generate heat seriously because the user frequently moves the pot away from the electromagnetic induction heating device and then places the pot in the electromagnetic induction heating device, and even the serious person may damage the switch tube to cause the electromagnetic induction heating device not to operate normally.
In one embodiment, in step S12, if the control unit 107 controls the electromagnetic induction heating apparatus to operate in the pot detection mode, the control unit 107 may wait for a predetermined time period, such as the aforementioned one minute, and if the second current signal C02 generated by the current detection unit 105 is smaller than the predetermined current value within one minute, indicating that no pot is placed in the electromagnetic induction heating apparatus within one minute, the control unit 107 starts to control the electromagnetic induction heating apparatus to turn off.
In one embodiment, as shown in fig. 1 and 2, the current detecting unit 105 may include a sensing circuit 1051 and a converting circuit 1052, and the first current signal C01 and the second current signal C02 generated by the current detecting unit 105 are digital signals. The power generating unit 101 includes a rectifying unit 1011 and a filtering unit 1012. The rectifying unit 1011 is coupled to the power input terminal 100, and the rectifying unit 1011 can be implemented as a full bridge rectifier. The filtering unit 1012 is coupled between the rectifying unit 1011 and the resonant unit 104, and the filtering unit 1012 may include an inductor and a capacitor coupled to the inductor. The rectifying unit 1011 can rectify the ac power input from the power input terminal 100 to generate a dc power. The filtering unit 1012 can filter the dc power generated by the rectifying unit 1011. The coil 1043 of the resonant unit 104 then generates a heating signal based on the filtered dc power.
In one embodiment, the pulse generating unit 102 generates two pulse width modulation signals that are in opposite phases with each other. As shown in fig. 1, in the pot detection mode, the pulse generating unit 102 further generates the third pwm signal GATA3, the third pwm signal GATA3 and the first pwm signal GATA1 are opposite in phase, that is, at the same time point, when the first pwm signal GATA1 is at a high level, the third pwm signal GATA3 is at a low level, and when the first pwm signal GATA1 is at a low level, the third pwm signal GATA3 is at a high level. As shown in fig. 2, in the heating mode, the pulse generating unit 102 further generates the fourth pwm signal GATA4, and the fourth pwm signal GATA4 and the second pwm signal GATA2 are in opposite phases.
Accordingly, the switch unit 103 may include a first switch 1031 and a second switch 1032. The second switch 1032 is alternatively turned on with the first switch 1031. In the pot detection mode, the first switch 1031 receives the first pwm signal GATA1 and is turned on according to the high level of the first pwm signal GATA1, and the second switch 1032 receives the third pwm signal GATA3 and is turned on according to the high level of the third pwm signal GATA 3. In the heating mode, the first switch 1031 receives the second pwm signal GATA2 and turns on according to the high level of the second pwm signal GATA2, and the second switch 1032 receives the fourth pwm signal GATA4 and turns on according to the high level of the fourth pwm signal GATA 4.
Thus, in the pot detection mode, the current detection unit 105 may generate the first current signal C01 according to the resonance current when the first switch 1031 is turned on, and generate the third current signal C03 according to the resonance current when the second switch 1032 is turned on. As shown in fig. 1, the phase detection unit 106 receives the pwm signals GATA1, GATA3 and the current signals C01, C03, the control unit 107 can detect the presence or absence of cookware and the material of cookware according to the first time width T1 between the negative edge of the first pwm signal GATA1 and the negative edge of the first current signal C01, and detect the presence or absence of cookware and the material of cookware according to the third time width between the negative edge of the third pwm signal GATA3 and the negative edge of the third current signal C03.
Likewise, in the heating mode, the current detection unit 105 may generate the second current signal C02 according to the resonance current when the first switch 1031 is turned on, and generate the fourth current signal C04 according to the resonance current when the second switch 1032 is turned on. As shown in fig. 2, the phase detecting unit 106 receives the pwm signals GATA2 and GATA4 and the current signals C02 and C04, the control unit 107 performs the pot-shift detection function according to the second time width T2 between the negative edge of the second pwm signal GATA2 and the negative edge of the second current signal C02, and performs the pot-shift detection function according to the fourth time width between the negative edge of the fourth pwm signal GATA4 and the negative edge of the fourth current signal C04.
In one embodiment, the first switch 1031 and the second switch 1032 may be implemented by Insulated Gate Bipolar Transistors (IGBTs); the control unit 107 may be a microcontroller, an embedded controller, or a central processing unit, and the control unit 107 may execute firmware (firmware) to perform the calculating and determining steps, etc.; the electromagnetic induction heating device can be an induction cooker or an induction cooker.
In summary, according to an embodiment of the electromagnetic induction heating apparatus of the present invention, the electromagnetic induction heating apparatus can measure the phase angle regularly to detect whether a pot is placed thereon, and the detection method is less susceptible to noise interference and has higher accuracy; and, the phase angle is highly correlated with the material of the pan, the electromagnetic induction heating device can identify the material of the pan by the phase angle, and correspondingly adjust the heating parameter, make the electromagnetic induction heating device operate in safe and stable state, in order to lengthen its service life, and the phase angle is influenced by factors such as the size, shape of the pan less, the accuracy is higher in judging the material of the pan. Furthermore, the electromagnetic induction heating device also has a pot moving detection function, and the electromagnetic induction heating device can be immediately and automatically closed or switched to a pot detection mode to protect the electromagnetic induction heating device. Therefore, the invention has the advantages of less noise interference, high accuracy, low implementation cost, no need of complex algorithm and high response speed.
The present invention is capable of other embodiments, and various changes and modifications may be made by one skilled in the art without departing from the spirit and scope of the invention.
Claims (11)
1. An electromagnetic induction heating device having a pot detection mode and a heating mode, comprising:
a power generating unit for generating a DC power;
a pulse generating unit for generating a first pulse width modulation signal having a preset detection frequency in the pot detection mode after the electromagnetic induction heating device is electrically started;
the resonant unit is coupled between the power supply generating unit and the pulse generating unit and used for generating a resonant current in the pot detection mode according to the direct-current power supply;
a current detection unit coupled to the resonance unit for generating a first current signal according to the resonance current;
a phase detection unit coupled to the pulse generation unit and the current detection unit for detecting a negative edge of the first PWM signal and a negative edge of the first current signal in the pot detection mode; and
a control unit, coupled to the phase detection unit and the pulse generation unit, for controlling the pulse generation unit to generate the first pulse width modulation signal in the pot detection mode, and calculating a first time width between a negative edge of the first pulse width modulation signal and a negative edge of the first current signal, wherein the control unit determines whether to control the pulse generation unit to generate a second pulse width modulation signal having a preset working frequency according to the first time width, so that the electromagnetic induction heating device is switched from the pot detection mode to the heating mode.
2. The electromagnetic induction heating apparatus according to claim 1, wherein the control unit calculates a first phase angle by multiplying a ratio between the first time width and a period time of the first pwm signal by 360 degrees, the control unit determines whether the first phase angle is smaller than a first predetermined angle, and when the phase angle is smaller than the first predetermined angle, the control unit controls the pulse generating unit to generate the second pwm signal, so that the electromagnetic induction heating apparatus is switched to the heating mode.
3. The electromagnetic induction heating apparatus according to claim 2, wherein the control unit controls the electromagnetic induction heating apparatus to be turned off when the phase angle is larger than the first predetermined angle.
4. The electromagnetic induction heating apparatus according to claim 3, wherein the control unit controls the electromagnetic induction heating apparatus to be turned off after waiting for a predetermined time period.
5. The electromagnetic induction heating apparatus according to claim 2, wherein when the phase angle is smaller than the first predetermined angle, the control unit further determines whether the phase angle is smaller than a second predetermined angle, the second predetermined angle is smaller than the first predetermined angle, when the phase angle is smaller than the second predetermined angle, the control unit controls the predetermined operating frequency of the second pwm signal generated by the pulse generating unit to be greater than a lower limit frequency value in the heating mode, and when the phase angle is greater than the second predetermined angle, the control unit controls the predetermined operating frequency of the second pwm signal generated by the pulse generating unit to be greater than or equal to the lower limit frequency value in the heating mode, wherein the lower limit frequency value corresponds to a maximum heating power of the electromagnetic induction heating apparatus.
6. The electromagnetic induction heating apparatus according to claim 5, wherein the control unit determines that a material of a pot disposed in the electromagnetic induction heating apparatus is 304 stainless steel when the phase angle is smaller than the first predetermined angle and smaller than the second predetermined angle, and wherein the control unit determines that a material of a pot disposed in the electromagnetic induction heating apparatus is iron or 430 stainless steel when the phase angle is smaller than the first predetermined angle and larger than the second predetermined angle.
7. The electromagnetic induction heating apparatus according to claim 6, wherein the predetermined detection frequency is 30KHz, the first predetermined angle is 82 degrees, and the second predetermined angle is 70 degrees.
8. The electromagnetic induction heating apparatus of claim 1, wherein the control unit calculates the first time width at a predetermined time point when the ac power reaches a peak value.
9. The electromagnetic induction heating apparatus according to claim 1, wherein the current detecting unit further generates a second current signal according to another resonant current generated by the resonant unit in the heating mode, and when the preset operating frequency of the second pwm signal generated by the pulse generating unit in the heating mode is greater than the preset detecting frequency, the control unit determines whether to control the electromagnetic induction heating apparatus to be turned off or control the pulse generating unit to generate the first pwm signal according to a current value of the second current signal.
10. The electromagnetic induction heating apparatus according to claim 9, wherein in the heating mode, when the preset operating frequency of the second pwm signal generated by the pulse generating unit is less than or equal to the preset detection frequency, the control unit calculates a second time width between a negative edge of the second pwm signal and a negative edge of the second current signal when the ac power reaches a peak value, and determines whether to control the electromagnetic induction heating apparatus to turn off or control the pulse generating unit to generate the first pwm signal according to the second time width.
11. The electromagnetic induction heating apparatus according to any one of claims 1 to 10, further comprising a power input terminal for receiving an alternating current power, wherein the power generating unit is coupled between the power input terminal and the resonance unit, and the power generating unit generates the direct current power according to the alternating current power.
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| TW108140157A TWI713410B (en) | 2019-11-05 | 2019-11-05 | Electromagnetic induction heating device |
| TW108140157 | 2019-11-05 |
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| KR101999511B1 (en) * | 2017-08-04 | 2019-07-11 | 엘지전자 주식회사 | Induction heat cooking apparatus and operating method thereof |
| TWI655880B (en) * | 2018-01-31 | 2019-04-01 | 盛群半導體股份有限公司 | Electromagnetic induction heating device and protection control circuit thereof |
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