TWI713410B - Electromagnetic induction heating device - Google Patents

Abstract

An electromagnetic induction heating device including a detection mode and a heating mode is provided. The device includes a power generating unit, a pulse generating unit, a resonant unit, a current detecting unit, a phase detecting unit, and a control unit. In the detection mode, the control unit controls a first pulse width modulation signal having a pre-determined detection frequency. The control unit determines whether to control the pulse generating unit to generate a second pulse width modulation signal having a pre-determined working frequency according to a time period from a negative edge of the first pulse width modulation signal to a negative edge of a first current signal from the current detecting unit. When the pulse generating unit generates the second pulse width modulation signal, the electromagnetic induction heating device switches to the heating mode from the detection mode.

Description

Electromagnetic induction heating device

This case is about an electromagnetic induction heating device, and especially an electromagnetic induction heating device with a pot detection function.

In some traditional induction cookers, the way to detect the pot is to send an excitation pulse to the resonance circuit first, and then calculate the number of induction pulses in the resonance circuit to determine whether the pot has been placed on it. However, the aforementioned detection methods are susceptible to interference from noise and cause misjudgment, which affects the user experience.

Furthermore, the traditional induction cooker cannot determine the material of the cookware. The same set of heating control parameters are used for cookware of different materials. If the user uses a cookware that does not contain iron or contains less iron, it will cause an electromagnetic induction heating device The pot cannot be heated, or the maximum heating power of the induction cooker cannot be reached. If the maximum heating power of the induction cooker cannot be reached, it will cause serious heating problems in the internal circuit of the induction cooker, resulting in unstable operation of the entire system and shortening the useful life of the electromagnetic induction heating device.

Furthermore, when the traditional induction cooker judges whether the pot has been removed during the heating process, it takes at least one mains cycle to determine whether the pot has been removed, which takes a long time to determine, and the traditional judging method of removing the pot is easily affected by the induction cooker. The influence of work is prone to misjudgment. If a misjudgment occurs, that is, after the cookware is removed, the induction cooker does not turn off its power output, which will cause the internal circuit to become warm. The degree rose rapidly. If the user suddenly puts back the pot, its internal circuit will generate a strong instantaneous current, which will cause serious heating of the internal circuit and even damage the induction cooker.

In one embodiment, the electromagnetic induction heating device includes a power generation unit, a pulse generation unit, a resonance unit, a current detection unit, a phase detection unit, and a control unit. The power input terminal receives AC power. The power generation unit generates DC power according to the AC power. The pulse generating unit generates a first pulse width modulation signal with a preset detection frequency in the pot detection mode after the electromagnetic induction heating device is powered on. The resonant unit is coupled between the power generating unit and the pulse generating unit, and the resonant unit generates a resonant current in the pot detection mode according to the DC power source. The current detection unit is coupled to the resonance unit, and the current detection unit generates a first current signal according to the resonance current. The phase detection unit is coupled to the pulse generation unit and the current detection unit. The phase detection unit 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, and calculates the first The first time width between the negative edge of the pulse width modulation signal and the negative edge of the first current signal. The control unit is coupled to the phase detection unit and the pulse generation unit. In the pot detection mode, the control unit controls the pulse generation unit to generate a first pulse width modulation signal, and determines whether to control the pulse generation unit to generate a pulse width modulation signal according to the first time width. A second pulse width modulation signal of one of the operating frequencies is set to switch the electromagnetic induction heating device from the pot detection mode to the heating mode.

100: power input

1001: positive extreme

1002: negative terminal

101: power generation unit

1011: rectifier unit

1012: filter unit

102: Pulse generating unit

103: switch unit

1031: First switch

1032: second switch

104: Resonant unit

1041: first capacitor

1042: second capacitor

1043: coil

105: current detection unit

1051: Sensing circuit

1052: conversion circuit

106: Phase detection unit

107: Control Unit

110: Zero detection unit

C01: The first current signal

C02: second current signal

C03: The third current signal

C04: The fourth current signal

S1: Control signal

S2: Zero-crossing detection signal

T1: first time width

T2: second time width

N1: the first connection point

N2: second connection point

S01-S05: Step

S031-S033: Step

S041-S042: steps

S07-S12: steps

GATA1: The first pulse width modulation signal

GATA2: second pulse width modulation signal

GATA3: third pulse width modulation signal

GATA4: The fourth pulse width modulation signal

[Figure 1] is a schematic circuit diagram of an embodiment of the electromagnetic induction heating device operating in the pot detection mode according to the present application.

[Figure 2] is a schematic circuit diagram of another embodiment of the electromagnetic induction heating device operating in the heating mode according to the present application.

[Figure 3] is the waveform diagram of the pulse width modulation signal and current signal generated by the electromagnetic induction heating device of Figures 1 and 2.

[Figure 4] is a flow chart of an embodiment of the pot detection method of the electromagnetic induction heating device according to the present application.

[Figure 5] is a flow chart of one implementation aspect of the pot detection method of Figure 4.

[Figure 6] is a flow chart of an embodiment of the pot detection method of the electromagnetic induction heating device in the heating mode according to the present application.

Fig. 1 and Fig. 2 are circuit diagrams of an embodiment of the electromagnetic induction heating device operating in the pot detection mode and the heating mode according to the present invention. After the electromagnetic induction heating device is powered on, the electromagnetic induction heating device first enters the pot detection mode, and the electromagnetic induction heating device detects whether a pot is placed on it. After the pot is placed in the electromagnetic induction heating device, the electromagnetic induction heating device is switched from the pot detection mode to the heating mode to heat the pot and the ingredients in the pot.

1 and 2 together, the electromagnetic induction heating device includes a power generation unit 101, a resonance unit 104, a pulse generation unit 102, a current detection unit 105, a phase detection unit 106, and a control unit 107. The resonance unit 104 is coupled between the power generation unit 101 and the pulse generation unit 102, and the pulse generation 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 generation unit 101 generates a DC power, and the resonance unit 104 resonates according to the DC power to generate a resonance current. The current detection unit 105 generates a current signal C01 (hereinafter referred to as the first current signal C01) according to the resonance current generated by the resonance unit 104 in the cookware detection mode.

The pulse generating unit 102 is controlled by the control unit 107. In the pot detection mode, as shown in FIG. 1, the pulse generating unit 102 can be controlled by the control signal S1 sent by the control unit 107 to generate a pulse width modulation (Pulse Width Modulation; PWM) signal GATA1 ( Hereinafter referred to as the first pulse width modulation signal GATA1); as shown in Figure 2, in the heating mode, the pulse generating unit 102 can be controlled by the control signal S1 sent by the control unit 107 to generate a pulse width modulation with a preset operating frequency The variable signal GATA2 (hereinafter referred to as the second pulse width modulation signal GATA2).

The phase detection unit 106 receives the first current signal C01 generated by the current detection unit 105 in the pot detection mode, and receives the first pulse width modulation signal GATA1 generated by the pulse generation unit 102. The phase detection unit 106 detects the negative edge of the first pulse width modulation signal GATA1. When the phase detection unit 106 detects the negative edge of the first pulse width modulation signal GATA1, the phase detection unit 106 detects the negative edge of the first current signal C01 to generate the negative edge of the first pulse width modulation signal GATA1 The time width T1 between the edge and the negative edge of the first current signal C01 (hereinafter referred to as the first time width T1) is shown in FIG. 3.

In operation, please refer to FIGS. 1 to 4 together. FIG. 4 is a flow chart of an embodiment of the pot detection method of the electromagnetic induction heating device according to the present application. In the pot detection mode, the control unit 107 controls the pulse generation unit 102 to generate the aforementioned first pulse width modulation signal GATA1 with a preset detection frequency (step S01), and the phase detection unit 106 calculates the first pulse width The first time width T1 between the negative edge of the modulation signal GATA1 and the negative edge of the first current signal C01 (step S02), the control unit 107 determines whether a pot is placed on it according to the first time width T1 (step S02) S03) to determine whether to control the pulse generating unit 102 to generate the aforementioned second pulse width modulation signal GATA2 with a preset operating frequency (step S04), that is, when the control unit 107 determines that a pot is placed on it (determine The result is "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 device is switched from the pot detection mode to the heating mode. Based on this, this case can prevent the electromagnetic induction heating device from turning on power because the pot is not placed, causing the electromagnetic induction heating device to work in an unstable state.

In one embodiment, the electromagnetic induction heating device further includes 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 generation unit 101, and the power generation unit 101 is coupled between the power input terminal 100 and the resonance unit 104. The power input terminal 100 can receive an AC power source from an external power source, and the power generation 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 resonance unit 104 generates a resonance current.

Furthermore, the electromagnetic induction heating device 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 to the power input terminal 100 and Between the control unit 107. The zero-point detection unit 110 can detect the zero-crossing of the AC power source (ie, the mains) and generate a zero-crossing detection signal S2. The zero-point detection unit 110 sends the zero-crossing detection signal S2 to the control unit 107 , The control unit 107 counts from the zero-crossing point for a predetermined length of time according to the zero-crossing detection signal S2, so that the commercial power reaches the peak value. Take the AC power supply with a frequency of 50Hz as an example, the preset time length can be 5ms, with 60Hz Take the AC power supply with frequency as an example, the preset time length can be 4.17ms. In the pot detection mode, the phase detection unit 106 executes step S02 to calculate the first time width T1 at a preset 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 the first phase angle), and the control unit 107 compares the first phase angle with a preset angle (hereinafter referred to as the first phase angle). A preset angle), the control unit 107 then decides whether to perform step S04 according to the comparison result. In detail, the control unit 107 is based on the first time width T1 and the cycle time of the first pulse width modulation signal GATA1 (the cycle time of the first pulse width modulation signal GATA1 and the preset detection frequency are mutually reciprocal) A ratio is calculated between, and the control unit 107 multiplies the aforementioned ratio by 360 degrees to calculate the first phase angle (step S031). The control unit 107 then determines whether the first phase angle is smaller than the first preset angle (step S032), When the first phase angle is smaller than the first preset angle (the judgment result is "Yes"), it means that the pot has been placed in the electromagnetic induction heating device, and the control unit 107 controls the pulse generation unit 102 to generate the second pulse width modulation signal GATA2 (Step S04) The electromagnetic induction heating device is operated according to the second pulse width modulation signal GATA2 to heat the pot and the ingredients in the pot.

For example, taking the first time width T1 and the cycle time of the first pulse width modulation signal GATA1 as 6 μs and 33 μs, respectively, in step S031, the control unit 107 multiplies by the ratio of 0.18 between 6 μs and 33 μs. 360 degrees is calculated as the first phase angle of 65 degrees. 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 less than the first preset angle of 82 degrees Angle (the judgment result is "Yes"), the control unit 107, that is, the control pulse generating unit 102, generates the second pulse width modulation 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 preset angle (the determination result is "No"), for example, the first phase angle is 90 degrees, which means that there is no pot. It is placed in the electromagnetic induction heating device. At this time, the control unit 107 can control the electromagnetic induction heating device to turn off (step S05). Alternatively, in other embodiments, the control unit 107 may also wait for a predetermined length of time, for example, one minute, and the control unit 107 controls the pulse generating unit 102 to continue to generate the first pulse width modulation signal GATA1 within one minute (step S01), the control unit 107 calculates the 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 within one minute when the mains reaches the peak value (step S02), and The first phase angle is calculated (step S031), and the control unit 107 determines whether the first phase angle is smaller than the first preset angle (step S032). If the control unit 107 does not determine that the first phase angle is less than the first preset angle within one minute, the control unit 107 starts to control the electromagnetic induction heating device to turn off (step S05).

Based on this, this case uses a phase angle to detect the presence or absence of a pot on it. Compared with the previous technology, its detection method is less susceptible to noise interference, less prone to misjudgment, and has a higher detection accuracy. And to enhance the user experience.

In an embodiment, as shown in FIGS. 1 and 2, the resonance unit 104 includes a first capacitor 1041, a second capacitor 1042 and a coil 1043, and the coil 1043 can be realized by an inductance. The first capacitor 1041 is coupled to the second capacitor 1042. One end of the coil 1043 is coupled to the 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 the 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. Based on this, in the pulse width modulation signal GATA1, GATA2 and During the operation of other pulse width modulation signals, the coil 1043 resonates. The coil 1043 interacts with the first capacitor 1041 and the second capacitor 1042 according to the DC power generated by the power generation unit 101 when the first switch 1031 and the second switch 1032 are alternately turned on Oscillation occurs, and the resonance unit 104 generates a resonance current.

Furthermore, the electromagnetic induction heating device may further include a switch unit 103, which is coupled between the resonance unit 104 and the pulse generation unit 102. The switch unit 103 receives the pulse width modulation signal generated by the pulse generation unit 102, and the pulse width modulation signal is used as a switch control signal for the switch unit 103 to turn on or off. For example, in the cookware detection mode, the switch unit 103 is turned on according to the high level of the first pulse width modulation signal GATA1, and in the heating mode, the switch unit 103 is based on the high level of the second pulse width modulation signal GATA2. Conduction. The resonant unit 104 can generate a resonant current according to the DC power supply when the switch unit 103 is turned on.

In one embodiment, in step S05, the control unit 107 can control the pulse generating unit 102 to generate a pulse width modulation signal (ie, a zero level signal) with a duty cycle of zero to control the switch unit 103 Turn off the electromagnetic induction heating device.

In one embodiment, when the pot is placed in the electromagnetic induction heating device, in step S03, the control unit 107 can further determine the material of the pot according to the aforementioned first phase angle, and control the pulse according to the material of the pot The lower limit of the preset operating frequency of the pulse width modulation signal generated by the generating unit 102 in the heating mode is because the preset operating frequency of the pulse width modulation signal is inversely proportional to the heating power of the electromagnetic induction heating device. In detail, please refer to FIGS. 1 to 5 together. When the control unit 107 determines in step S032 that the first phase angle is smaller than the first preset angle (the determination result is "Yes"), the control unit 107 further determines the first Whether the phase angle is smaller than another preset angle (hereinafter referred to as a second preset angle) (step S033).

When the first phase angle is greater than the second preset angle (that is, the first phase angle is between the first preset angle and the second preset angle) (the judgment result is "No"), it means that the cookware is made of iron Or 430 stainless steel. At this time, the control unit 107 controls the second pulse width modulation signal GATA2 generated by the pulse generating unit 102 in the heating mode. The preset operating frequency can reach a lower limit frequency corresponding to the maximum heating power of the electromagnetic induction heating device Value (step S042), that is, the preset operating frequency is greater than or equal to the lower limit frequency value, that is, 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 When the angle is less than the second preset angle (that is, the first phase angle is less than the first preset angle and less than the second preset angle) (the judgment result is "Yes"), it means that the material of the pot is 304 stainless steel. At this time, The control unit 107 controls the second pulse width modulation signal GATA2 generated by the pulse generating unit 102 in the heating mode to have a preset operating frequency greater than the lower limit frequency (step S041), that is, the electromagnetic induction heating device uses a smaller heating power Heat the pot made of 304 stainless steel.

In this way, the problem that the electromagnetic induction heating device cannot reach the maximum heating power due to the pots made of 304 stainless steel can be avoided, and the problem that the switch unit 103 and the coil 1043 cannot reach the maximum heating power of the electromagnetic induction heating device can cause serious heat generation. , Thereby avoiding the unstable operation of the system and shortening the useful life of the electromagnetic induction heating device.

In one embodiment, the designer of the electromagnetic induction heating device can design the control unit 107 to control the pulse generating unit 102 to generate a preset detection frequency of 30KHz, and place pots made of 430 stainless steel, iron or 304 stainless steel in the electromagnetic For the induction heating device, the designer can design the control unit 107 to calculate the corresponding first phase angle according to the pots of different materials, and set the first preset angle and the second preset angle accordingly. For example, the control unit 107 The first phase angle calculated by 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 based on the pot made of 304 stainless steel is 60 Between degrees and 70 degrees. Here, the first preset angle may be 82 degrees, and the second preset angle may be 70 degrees. The control unit 107 can determine from the first preset angle of 82 degrees and the second preset angle of 70 degrees. The material of the cookware generates the corresponding control signal S1 to control the pulse generating unit 102.

In one embodiment, in the heating mode, the electromagnetic induction heating device has a pan-moving detection function, and the control unit 107 can determine whether the pan is removed from the electromagnetic induction heating device to determine whether it is necessary to control the electromagnetic induction heating device to be heated. Switch the mode to the pot detection mode, or control the electromagnetic induction heating device to turn off. In detail, as shown in FIG. 2, in the heating mode, the current detection unit 105 can further generate a current signal C02 (hereinafter referred to as the second current signal C02) according to the resonant current generated by the resonance unit 104. In the heating mode, when When the working frequency of the second pulse width modulation signal GATA2 is greater than the aforementioned preset detection frequency (for example, the working frequency and the preset detection frequency are 40KHz and 30KHz respectively, and the working frequency of 40KHz is greater than the preset detection frequency of 30KHz) The control unit 107 judges whether it is necessary to control the electromagnetic induction heating device to leave the heating mode according to the current value of the second current signal C02.

Please refer to Figures 1 to 3 and Figure 6 together. In the heating mode, when the operating frequency of the second pulse width modulation signal GATA2 is greater than the preset detection frequency, the control unit 107 determines that the current detection unit 105 has two consecutive times Whether the current difference between the second current signals C02 generated by the points is greater than a preset difference (step S11), when the aforementioned current difference is greater than the preset difference (the judgment result is "Yes"), it means the pot Has moved away from the electromagnetic induction heating device, at this time, the control unit 107 controls the electromagnetic induction heating device to switch from heating mode to pot detection mode, or Control the electromagnetic induction heating device to turn off (step S12); when the aforementioned current difference is less than the preset difference (the judgment result is "No"), it means that the pot has not been removed from the electromagnetic induction heating device. At this time, the control unit 107 The electromagnetic induction heating device is controlled to continue to operate in the heating mode (step S10) without controlling the electromagnetic induction heating device to change its operation mode.

On the other hand, in the heating mode, when the working frequency of the second pulse width modulation signal GATA2 generated by the pulse generating unit 102 is less than or equal to the preset detection frequency (for example, the working frequency and the preset detection frequency are 25KHz and 30KHz, respectively) , When the operating frequency of 25KHz is less than the preset detection frequency of 30KHz), the control unit 107 in the heating mode adjusts the difference between the negative edge of the second pulse width modulation signal GATA2 and the negative edge of the second current signal C02 The time width T2 (hereinafter referred to as the second time width T2) determines whether the pot is removed from the electromagnetic induction heating device, and determines whether the electromagnetic induction heating device needs to be controlled to change its operation mode.

In detail, in the heating mode, as shown in FIGS. 3 and 6, the phase detection unit 106 further detects the negative edge of the second pulse width modulation signal GATA2 and the negative edge of the second current signal C02, and the phase detection In the heating mode, the unit 106 calculates the second time width T2 between the negative edge of the second pulse width modulation signal GATA2 and the negative edge of the second current signal C02 when the commercial power reaches the peak value (step S07), and the control unit 107 according to The ratio between the second time width T2 and the cycle time of the second pulse width modulation signal GATA2 (for example, the cycle time of the second pulse width modulation signal GATA2 with a working frequency of 25KHz is 40μs) calculates the phase angle (below Called the second phase angle) (step S08), the control unit 107 determines whether the second phase angle is less than the first preset angle (step S09), when the second phase angle is less than the first preset angle (the judgment result is "Yes "), indicating that the pot has not been 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). The electromagnetic induction heating device needs to be controlled to change its operating mode; when the second phase angle is greater than or equal to the first preset angle (the judgment result is "No"), it means that the pot has been moved away from the electromagnetic induction heating device. The unit 107 controls the electromagnetic induction heating device to switch from the heating mode to the pot detection mode, or controls the electromagnetic induction heating device to turn off (step S12). Among them, the calculation of steps S07 and S08 has been described in detail above, and will not be repeated here.

In this way, the aforementioned pan-moving detection function can prevent the coil 1043 and the switch unit 103 from heating seriously due to the user frequently removing the pan from the electromagnetic induction heating device and then placing the pan in the electromagnetic induction heating device. In severe cases, the switch tube may be damaged and the electromagnetic induction heating device cannot operate normally.

In one embodiment, in step S12, if the control unit 107 controls the electromagnetic induction heating device to operate in the pot detection mode, the control unit 107 may wait for a predetermined length of time, such as the aforementioned one minute, if the current is detected within one minute The second current signal C02 generated by the measuring unit 105 is less than the preset current value, which means that no pot is placed in the electromagnetic induction heating device within one minute, and the control unit 107 starts to control the electromagnetic induction heating device to turn off.

In one embodiment, as shown in FIGS. 1 and 2, the current detection unit 105 may include a sensing circuit 1051 and a conversion circuit 1052. The first current signal C01 and the second current signal C02 generated by the current detection unit 105 are It is a digital signal. The power generation 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 by a full-bridge rectifier. The filter unit 1012 is coupled between the rectifier unit 1011 and the resonance unit 104. The filter unit 1012 may include an inductor and a capacitor coupled to the inductor. The rectifier unit 1011 can rectify the AC power input from the power input terminal 100 to generate DC power. The filtering unit 1012 can filter the DC power generated by the rectifying unit 1011. Coil of resonance unit 104 1043 then generates a heating signal based on the filtered DC power supply.

In one embodiment, the pulse generating unit 102 generates two pulse width modulation signals that are inverse to each other. As shown in FIG. 1, in the cookware detection mode, the pulse generating unit 102 further generates a third pulse width modulation signal GATA3, and the third pulse width modulation signal GATA3 and the first pulse width modulation signal GATA1 are mutually consistent. Reverse phase, that is, at the same time point, when the first pulse width modulation signal GATA1 is at a high level, the third pulse width modulation signal GATA3 is at a low level, and when the first pulse width modulation signal GATA1 is at a low level, the The three-pulse width modulation signal GATA3 is at a high level. As shown in FIG. 2, in the heating mode, the pulse generating unit 102 further generates a fourth pulse width modulation signal GATA4, and the fourth pulse width modulation signal GATA4 and the second pulse width modulation signal GATA2 are mutually inverted. .

Based on this, the switch unit 103 can include a first switch 1031 and a second switch 1032. The second switch 1032 and the first switch 1031 are selectively turned on. In the cookware detection mode, the first switch 1031 receives the first pulse width modulation signal GATA1 and turns on according to the high potential of the first pulse width modulation signal GATA1, and the second switch 1032 receives the third pulse width modulation signal GATA3 And according to the third pulse width modulation signal GATA3, the high potential is turned on. In the heating mode, the first switch 1031 receives the second pulse width modulation signal GATA2 and turns on according to the high potential of the second pulse width modulation signal GATA2, and the second switch 1032 receives the fourth pulse width modulation signal GATA4 and turns on The high potential of the fourth pulse width modulation signal GATA4 is turned on.

Therefore, in the pot detection mode, the current detection unit 105 can 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 Figure 1, the phase detection unit 106 is connected to After receiving the pulse width modulation signals GATA1, GATA3 and the current signals C01, C03, the control unit 107 can adjust the 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 Perform the detection of the presence or absence of the pot and the material of the pot, and perform the detection of the presence or absence of the pot and the material of the pot according to the third time width between the negative edge of the third pulse width modulation signal GATA3 and the negative edge of the third current signal C03 .

Similarly, in the heating mode, the current detection unit 105 can 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 detection unit 106 receives pulse width modulation signals GATA2, GATA4 and current signals C02, C04, and the control unit 107 can adjust the negative edge of the second pulse width modulation signal GATA2 and the second current signal C02 The second time width T2 between the negative edges of the two performs its pan-shifting detection function, and the fourth time width between the negative edge of the fourth pulse width modulation signal GATA4 and the negative edge of the fourth current signal C04 performs its function Pot shift detection function.

In an embodiment, the first switch 1031 and the second switch 1032 can be implemented by insulated gate bipolar transistors (IGBT); the control unit 107 can be a microcontroller, an embedded controller or a central processing unit , The control unit 107 can execute firmware to perform calculation and determination steps; the electromagnetic induction heating device can be an induction cooker or an induction cooker.

To sum up, according to an embodiment of the electromagnetic induction heating device in this case, the electromagnetic induction heating device can periodically measure the phase angle to detect whether a pot is placed on it, and its detection method is less susceptible to noise interference. It has high accuracy; and the phase angle is highly correlated with the material of the pot. The electromagnetic induction heating device can identify the material of the pot by the phase angle, and Adjust the heating parameters accordingly to make the electromagnetic induction heating device run in a safe and stable state to extend its service life, and the phase angle is less affected by factors such as the size and shape of the pot, and has a higher accuracy in judging the pot material . Furthermore, the electromagnetic induction heating device also has a pan-moving detection function, and the electromagnetic induction heating device can instantly and automatically shut down or switch to the pan detection mode to protect the electromagnetic induction heating device. Based on this, this case has the advantages of less noise interference, high accuracy, low implementation cost, no need for complex algorithms, and fast response speed.

Although this case has been disclosed by the examples above, it is not intended to limit the case. Anyone with ordinary knowledge in the technical field can make some changes and modifications without departing from the spirit and scope of the case. Therefore, the scope of protection of this case The scope of the patent application attached hereafter shall prevail.

S01-S05: Step

S031-S032: steps

Claims (9)

An electromagnetic induction heating device has a pot detection mode and a heating mode, including: a power generation unit to generate a DC power; a pulse generation unit to start the electromagnetic induction heating device In the pot detection mode, a first pulse width modulation signal having a predetermined detection frequency is generated; a resonance unit is coupled between the power generation unit and the pulse generation unit, and is configured to operate in accordance with the DC power supply A resonant current is generated in the pot detection mode; a current detection unit is coupled to the resonant unit to generate a first current signal according to the resonant current; a phase detection unit is coupled to the pulse generating unit and the current The detecting unit is used for detecting the negative edge of the first pulse width modulation signal and the negative edge of the first current signal in the pot detection mode, and calculating the negative edge and the first pulse width modulation signal A first time width between the negative edges of the first current signal; and a control unit, coupled to the phase detecting unit and the pulse generating unit, for controlling the pulse generating unit to generate in the pot detection mode The first pulse width modulation signal, the control unit multiplies a ratio of the first time width and a period of the first pulse width modulation signal by 360 degrees to calculate a phase angle, the control unit Determine whether the phase angle is less than a first preset angle, and when the phase angle is less than the first preset angle, the control unit controls the pulse generating unit to generate a second pulse width modulation signal with a preset operating frequency , The electromagnetic induction heating device is switched from the pot detection mode to the heating mode, and when the phase angle is less than the first preset angle, the control unit determines whether the phase angle is small At a second predetermined angle, when the phase angle is smaller than the second predetermined angle, the control unit controls the predetermined operating frequency of the second pulse width modulation signal generated by the pulse generating unit in the heating mode Is greater than the lower limit frequency value; when the phase angle is greater than the second preset angle, the control unit controls the preset operating frequency of the second pulse width modulation signal generated by the pulse generating unit in the heating mode Greater than or equal to the lower limit frequency value; wherein, the second predetermined angle is smaller than the first predetermined angle, and the lower limit frequency value corresponds to the maximum heating power of the electromagnetic induction heating device. The electromagnetic induction heating device according to claim 1, wherein when the phase angle is greater than the first preset angle, the control unit controls the electromagnetic induction heating device to turn off. The electromagnetic induction heating device according to claim 2, wherein the control unit controls the electromagnetic induction heating device to turn off after waiting for a predetermined length of time. The electromagnetic induction heating device according to claim 1, wherein when the phase angle is smaller than the first preset angle and smaller than the second preset angle, the control unit determines that a pot is placed in the electromagnetic induction heating device The material is 304 stainless steel, and when the phase angle is smaller than the first preset angle and greater than the second preset angle, the control unit determines that the material of a pot placed in the electromagnetic induction heating device is iron or 430 stainless steel. The electromagnetic induction heating device according to claim 4, wherein the preset detection frequency is 30 KHz, the first preset angle is 82 degrees, and the second preset angle is 70 degrees. The electromagnetic induction heating device according to claim 1, wherein the power generation unit receives an AC power source and generates the DC power source according to the AC power source, and the phase detection unit is preset when the AC power source reaches a peak value The time point calculates the first time width. The electromagnetic induction heating device according to claim 1, wherein in the heating mode, the current detection unit further generates a second current signal according to another resonance current generated by the resonance unit, when the pulse generating unit is in the heating mode When the preset operating frequency of the second pulse width modulation signal generated in the second pulse width modulation signal is greater than the preset detection frequency, the control unit determines whether to control the electromagnetic induction heating device to turn off or to control the pulse according to the current value of the second current signal The generating unit generates the first pulse width modulation signal. The electromagnetic induction heating device according to claim 7, wherein the power generation unit receives an AC power source and generates the DC power source according to the AC power source, and in the heating mode, when the second pulse width generated by the pulse generation unit When the preset operating frequency of the modulated signal is less than or equal to the preset detection frequency, the phase detection unit calculates the difference between the negative edge of the second pulse width modulated signal and the second current signal when the AC power reaches the peak There is a second time width between the negative edges, and according to the second time width, it is determined whether to control the electromagnetic induction heating device to turn off or control the pulse generating unit to generate the first pulse width modulation signal. The electromagnetic induction heating device according to any one of claims 1 to 5 and claim 7, further comprising a power input terminal for receiving an AC power source, wherein the power generation unit is coupled between the power input terminal and the Between the resonance units, the power generation unit generates the DC power according to the AC power.

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