TW201935998A - Electromagnetic induction heating device and protection control circuit thereof - Google Patents

Abstract

An electromagnetic induction heating device and a protection control circuit thereof are provided. The device includes a power input terminal, a power transferring unit, a pulse generating unit, a switch unit, a resonant unit, a coil current detecting unit, a phase detecting unit, and a control unit. The resonant unit includes a coil. The switch unit includes a first switch and a second switch. The coil current detecting unit generates a current signal according to a current flowing through the coil. The phase detecting unit detects a pulse width between a negative edge of a control signal for conducting any one of the first switch and the second switch and a negative edge of the current signal. The control unit controls the pulse generating unit according to the pulse width.

Description

Electromagnetic induction heating device and its protection control circuit

This case relates to a heating device, and in particular to an electromagnetic induction heating device.

The main circuit of a conventional induction cooker includes a resonant circuit and a switch. By turning on the pulse width modulation signal to control the switch, the resonance coil included in the resonance circuit can generate a magnetic field during PWM operation, and then generate eddy current to generate heat, so as to achieve the purpose of heating food.

However, the traditional induction cooker has a discontinuous working state when the set power is small, that is, the working state of the induction cooker is divided into working period and non-working period. The control unit of the induction cooker will adjust the on-time of the switch according to the power set by the user to Set the length of the aforementioned working cycle and non-working cycle. This working method can not really achieve a low-power working state, and the food is heated by a discontinuous induction cooker. The time required to boil the food is longer. Power consumption.

In addition, when the power of the induction cooker is set to a large power, the on-time of the switch will reach the maximum. Because the AC input voltage is unstable, it has a certain fluctuation range. If the input voltage reaches a high voltage, such as 264V, the resonant circuit will resonate. It is close to 1200V, and sometimes even reaches the withstand voltage value of the switch, resulting in the risk of overvoltage damage to the switch. In severe cases, it may even cause the induction cooker to burn. Therefore, how to make the induction cooker more power-saving and safer is one of the most important topics at present.

In view of this, this case proposes an electromagnetic induction heating device and its protection control circuit.

In one embodiment, the electromagnetic induction heating device includes a power input terminal, a power conversion unit, a pulse generation unit, a switch unit, a resonance unit, a coil current detection unit, a phase detection unit, and a control unit. The power input receives AC power. The power conversion unit generates DC power according to the AC power. The pulse generating unit generates a first switch control signal and a second switch control signal. The first switch control signal and the second switch control signal are pulse width modulation signals. The switching unit is coupled to the pulse generating unit. The switching unit includes a first switch and a second switch. The first switch is turned on according to the first switch control signal, the second switch is coupled to the first switch, and the second switch is turned on alternately with the first switch according to the second switch control signal. The resonance unit is coupled between the power conversion unit and the switching unit. The resonance unit includes a first capacitor, a second capacitor coupled to the first capacitor, and a coil. The coil is coupled between the first connection point between the first switch and the second switch and the second connection point between the first capacitor and the second capacitor. The coil drives the electromagnetic induction heating device according to the DC power generation during the PWM operation. heating. The coil current detection unit is coupled to the aforementioned coil to detect the current flowing through the coil to generate a current signal during the PWM operation; the phase detection unit is coupled to the pulse generation unit and the coil current detection unit to detect the first switch control The time width between the negative edge of any one of the signal and the second switch control signal and the negative edge of the current signal. The control unit controls the pulse generating unit to perform a protection control according to whether the foregoing time width is equal to zero or whether the time width is less than a preset time width.

In one embodiment, the protection control circuit suitable for the electromagnetic induction heating device includes a pulse generating unit, a switching unit, a resonance unit, a coil current detection unit, a phase detection unit, and a control unit. The pulse generating unit generates a first switch control signal and a second switch control signal. The first switch control signal and the second switch control signal are pulse width modulation signals. The switching unit is coupled to the pulse generating unit. The switching unit includes a first switch and a second switch. The first switch is turned on according to the first switch control signal, the second switch is coupled to the first switch, and the second switch is turned on alternately with the first switch according to the second switch control signal. The resonance unit is coupled between the power conversion unit and the switching unit. The resonance unit includes a first capacitor, a second capacitor coupled to the first capacitor, and a coil. The coil is coupled between the first connection point between the first switch and the second switch and the second connection point between the first capacitor and the second capacitor. The coil drives the electromagnetic induction heating device according to the DC power generation during the PWM operation. heating. The coil current detection unit is coupled to the aforementioned coil to detect the current flowing through the coil to generate a current signal during the PWM operation; the phase detection unit is coupled to the pulse generation unit and the coil current detection unit to detect the first switch control The time width between the negative edge of any one of the signal and the second switch control signal and the negative edge of the current signal. The control unit controls the pulse generating unit to perform a protection control according to whether the foregoing time width is equal to zero or whether the time width is less than a preset time width.

1 and 2 are schematic circuit diagrams of an embodiment of an electromagnetic induction heating device according to the present case. Please refer to FIG. 1 and FIG. 2 together. The electromagnetic induction heating device includes a power input terminal 100, a power conversion unit 101, a pulse generating unit 102, a switching unit 103, a resonance unit 104, a coil current detection unit 105, a phase detection unit 106, and Control unit 107. The power input terminal 100 is coupled to the power conversion unit 101, the resonance unit 104 is coupled between the power conversion unit 101 and the switching unit 103, the switching unit 103 is coupled to the pulse generating unit 102, and the pulse generating unit 102 is coupled to the control unit 107. The coil current detection unit 105 is coupled between 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 connected between the coil current detection unit 105 and the control unit 107.

In one embodiment, the pulse generating unit 102, the switching unit 103, the resonance unit 104, the coil current detection unit 105, the phase detection unit 106, and the control unit 107 are protection control circuits of an electromagnetic induction heating device, that is, electromagnetic induction The heating device includes a protection control circuit, and the aforementioned protection control circuit includes at least a pulse generating unit 102, a switching unit 103, a resonance unit 104, a coil current detection unit 105, a phase detection unit 106, and a control unit 107. The protection control circuit can Avoid burning the electromagnetic induction heating device and damage it.

The power input terminal 100 receives AC power from one of external power sources. The power input terminal 100 may have a positive terminal 1001 and a negative terminal 1002. The power conversion unit 101 receives AC power from the power input terminal 100 and generates DC power according to the AC power.

The pulse generating unit 102 is controlled by the control unit 107. The pulse generating unit 102 generates a first switch control signal GATA1 and a second switch control signal GATA2 with corresponding frequencies according to the control of the control unit 107. The first switch control signal GATA1 and the second switch control signal GATA2 are both Pulse Width Modulation (PWM) signals.

The switching unit 103 includes a first switch 1031 and a second switch 1032. The first switch 1031 is turned on according to the first switch control signal GATA1 generated by the pulse generating unit 102. The second switch 1032 is turned on according to the second switch control signal GATA2 generated by the pulse generating unit 102. The second switch 1032 and the first switch 1031 are selectively turned on. That is, when the first switch 1031 is turned on, the second switch 1032 is not turned on. When the second switch 1032 is turned on, the first switch 1031 is turned off. In an embodiment, the first switch 1031 and the second switch 1032 can be turned on according to a high potential, and the potentials of the first switch control signal GATA1 and the second switch control signal GATA2 at the same time point are opposite to each other. Here, when the first switch control signal GATA1 has a high potential, the second switch control signal GATA2 has a low potential, at this time the first switch 1031 is turned on and the second switch 1032 is not turned on; when the first switch control signal GATA1 has a low potential At this time, the second switch control signal GATA2 has a high potential. At this time, the first switch 1031 is not turned on and the second switch 1032 is turned on.

The resonance unit 104 includes a first capacitor 1041, a second capacitor 1042, and a coil 1043. 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, during the PWM operation, the coil 1043 resonates, and the coil 1043 interacts with the first capacitor 1041 and the second capacitor 1042 according to the DC power generated by the power conversion unit 101 when the first switch 1031 and the second switch 1032 alternately conduct. .

Further, the coil current detecting unit 105 can detect a current flowing through the coil 1043. During the PWM operation, as shown in FIG. 1, the coil current detection unit 105 detects a current flowing through the coil 1043 and generates a current signal, such as the first current signal C01 illustrated in FIG. 1.

The phase detection unit 106 receives the first current signal C01 generated by the coil current detection unit 105 during the PWM operation, and the phase detection unit 106 receives the first switch control signal C01 and the second switch control signal generated by the pulse generation unit 102. Any of C02. The following and FIG. 1 are described by taking the phase detection unit 106 receiving the first switch control signal GATA1 from the pulse generating unit 102 as an example. During the PWM operation, the phase detection unit 106 detects the negative edge of the first switch control signal GATA1. When the phase detection unit 106 detects the negative edge of the first switch control signal GATA1, the phase detection unit 106 detects the negative edge of the first current signal C01 to detect the negative edge and the first edge of the first switch control signal GATA1. The time width between the negative edges of a current signal C01 (for convenience of description, hereinafter referred to as the first time width).

As shown in FIG. 1, the phase detection unit 106 can output a protection signal PROTECT1 indicating whether the first time width is zero or smaller than the first preset time width to the control unit 107. Therefore, by the protection signal PROTECT1, the control unit 107 further determines whether the first time width is equal to zero or whether the first time width is smaller than the first preset time width. When the first time width is equal to zero or the first time width is less than the first preset time width, the control unit 107 controls the pulse generation unit 102 to perform a protection control. For example, the control unit 107 may control the pulse generation unit 102 to stop generating the switch control signal. GATA1, GATA2, or the control pulse generating unit 102 generates a third switch control signal and a fourth switch control signal to the first switch 1031 and the second switch 1032, respectively, and the frequency of the third switch control signal is greater than the first switch control signal GATA1 The frequency of the fourth switch control signal is greater than the second switch control signal GATA2. In this way, the current flowing through the coil 1043 is reduced, thereby avoiding that the current flowing through the coil 1043 is too large and the switch circuit 103 is burned out, or even the electromagnetic induction heating device is burned.

FIG. 3 is a schematic diagram of an embodiment of an operating section of an electromagnetic induction heating device, wherein a horizontal axis represents a frequency of a switch control signal generated by the pulse generating unit 102, and a vertical axis represents a current flowing through the coil 1043. Referring to FIG. 3, the electromagnetic induction heating device is operated in an inductive operation section II. As can be seen from FIG. 3, in the operation interval II, if the frequency of the switch control signal is larger, the current flowing through the coil 1043 is smaller. Therefore, when the control unit 107 determines that the first time width is equal to zero or the first time width is less than the first preset time width, it indicates that the operation interval of the electromagnetic induction heating device is close to the resonance frequency, that is, close to the capacitive operation interval I, and The control unit 107 further controls the pulse generating unit 102 to cause the electromagnetic induction heating device to operate in the inductive operation interval II without falling into the capacitive operation interval I, thereby improving the safety of the electromagnetic induction heating device.

FIG. 2 is a schematic circuit diagram of another embodiment of the electromagnetic induction heating device. As shown in FIG. 2, in addition to the coil current detection unit 105 generating a first current signal C01, the coil current detection unit 105 may also generate a second Current signal C02. Here, in addition to receiving the first switch control signal GATA1 and the first current signal C01, the phase detection unit 106 also receives the second switch control signal GATA2 and the second current signal C02, and during the PWM operation period Detects the negative edge of the second switch control signal GATA2. When the phase detection unit 106 detects the negative edge of the second switch control signal GATA2, the phase detection unit 106 detects the negative edge of the second current control signal C02 to detect the negative edge and the first edge of the second switch control signal GATA2. The time width between the negative edges of the two current signals C02 (for convenience of description, hereinafter referred to as the second time width). Then, the phase detection unit 106 may output a protection signal PROTECT2 indicating whether the second time width is zero or smaller than the second preset time width to the control unit 107, so that the control unit 107 further determines whether the second time width is equal to zero or second. Whether the time width is smaller than the second preset time width to control the pulse generating unit 102. When the second time width is equal to zero or the second time width is less than the second preset time width, the control unit 107 controls the pulse generation unit 102 to perform protection control, for example, the aforementioned control pulse generation unit 102 stops generating switch control signals GATA1, GATA2, Or the control pulse generating unit 102 generates a third switch control signal and a fourth switch control signal to the first switch 1031 and the second switch 1032, respectively, and the frequency of the third switch control signal is greater than the first switch control signal GATA1, the fourth switch The frequency of the control signal is greater than the second switch control signal GATA2. In this way, according to the two current signals C01 and C02, the phase detection unit 106 can detect the time width between the switch control signal and the negative edge of the current signal twice in a cycle, so that the control unit 107 can control the pulse in real time. The generating unit 102 performs protection control.

In an embodiment, the aforementioned first preset time width and the second preset time width may be any non-zero time length and the second preset time width may be the same or different from the first preset time width, for example, The first preset time width and the second preset time width are both 5 μs, or the first preset time width and the second preset time width are 5 μs and 10 μs, respectively. The control unit 107 may The pulse generating unit 102 is controlled whether it is less than a non-zero first preset time width or whether the second time width is less than a non-zero second preset time width.

In an embodiment, the coil 1043 may be an inductor; the first switch 1031 and the second switch 1032 may be implemented by an insulated gate bipolar transistor (IGBT); the control unit 107 may be a microcontroller, an embedded type Controller or central processing unit.

In an embodiment, please refer to FIG. 1 and FIG. 2 again. The power conversion unit 101 includes a rectification unit 1011 and a filtering unit 1012. The rectifying unit 1011 is coupled to the power input terminal 100. The filtering unit 1012 is coupled between the rectifying unit 1011 and the resonance unit 104. 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 resonance unit 104 then generates a heating signal according to the filtered DC power supply. In one embodiment, the rectifier unit 1011 may be implemented as a full-bridge rectifier, and the filter unit 1012 may include an inductor and a capacitor coupled to the inductor.

In one embodiment, as described above, the pulse generating unit 102 generates complementary first switch control signals GATA1 and second switch control signals GATA2, that is, at the same time point, the first switch control signals GATA1 and the first The potentials of the two switch control signals GATA2 are opposite to each other. Please refer to FIG. 1, FIG. 2, FIG. 4, and FIG. 5 together. FIG. 4 is a schematic circuit diagram of an embodiment of the pulse generating unit 102. FIG. 5 is a schematic diagram of signals generated by the circuits of the pulse generating unit 102 illustrated in FIG. 4. Wave chart. As shown in FIG. 4, the pulse generating unit 102 includes a PWM generating circuit 1021, a complementary PWM generating circuit 1022, a delay control circuit 1023, and a polarity control circuit 1024. The PWM generating circuit 1021, the complementary PWM generating circuit 1022, the delay control circuit 1023, and the polarity control circuit 1024 are sequentially connected in series. The PWM generating circuit 1021 is coupled between the control unit 107 and the complementary PWM generating circuit 1022. The PWM generating circuit 1021 receives the pulse wave generation control signal S1 generated by the control unit 107. The pulse wave generation control signal S1 may include a uniform energy signal and a For the frequency control signal, the PWM generating circuit 1021 generates a PWM signal S2 with a frequency specified by the frequency control signal according to the pulse wave generating control signal S1. Then, the complementary PWM generating circuit 1022 receives the PWM signal S2 and generates complementary PWM signals AT0 and PWM signals AB0 according to the PWM signal S2. The delay control circuit 1023 receives the PWM signal AT0 and the PWM signal AB0 from the complementary PWM generating circuit 1022 and inserts a delay time DT0 and a delay time DT1 into the PWM signal AT0 and the PWM signal AB0 to generate the PWM signal AT1 and the PWM signal AB1, respectively. . Finally, the polarity control circuit 1024 determines whether the PWM signal AT1 and the PWM signal AB1 need to be inverted to generate the switch control signal GATA1 and the switch control signal GATA2. Here, the switch control signal GATA1 and the PWM signal AT1 shown in FIG. 5 are in phase with each other, and the switch control signal GATA2 and the PWM signal AB1 are also in the same direction with each other. It can be seen from FIG. 5 that there is a delay time DT0 between a negative edge of the second switch control signal GATA2 and a positive edge of the first switch control signal GATA1, and a negative edge of the first switch control signal GATA1 and the second switch. The difference between the positive edges of the control signals GATA2 is a delay time DT1. In this way, the first switch 1031 and the second switch 1032 are selectively conducted, thereby preventing the first switch 1031 and the second switch 1032 from being simultaneously conducted.

In an embodiment, as shown in FIGS. 1 and 2, the coil current detection unit 105 includes a sensing circuit 1051 and a conversion circuit 1052. The sensing circuit 1051 is coupled between the second connection point N2 and the coil 1043, and the conversion circuit 1052 is coupled between the sensing circuit 1051 and the phase detection unit 106. As shown in FIG. 1, the sensing circuit 1051 can sense the current flowing through the coil 1043 and generate a sensing signal VCS1 which is an analog signal during the PWM operation. As shown in FIG. 2, during the PWM operation, the sensing circuit 1051 can sense the current flowing through the coil 1043 and further generate a sensing signal VCS2 which is also an analog signal. The conversion circuit 1052 receives the sensing signal VCS1 and the sensing signal VCS2. The conversion circuit 1052 converts the sensing signal VCS1 and the sensing signal VCS2 into a first current signal C01 and a second current signal C02, and a first current signal, respectively, according to a predetermined voltage. C01 and the second current signal C02 are digital signals.

Please refer to FIG. 6 together, which is a schematic circuit diagram of an embodiment of the sensing circuit 1051. The sensing circuit 1051 includes a current detector CT71, a resistor R71, a resistor R72, and a resistor R73. The current flowing through the coil 1043 passes through the current sensor CT71, and another current proportional to the current flowing through the coil 1043 is induced at both ends of the current sensor CT71. The two ends of the current sensor CT71 are connected in parallel with the resistor R71 and in parallel with a series circuit composed of the resistor R72 and the resistor R73, and a node connected to the resistor R72 and R73 is connected to a specific voltage. One end of the current sensor CT71 can generate a sensing signal VCS1 to the conversion circuit 1052 during the PWM operation, so that the conversion circuit 1052 generates a first current signal C01 accordingly. Moreover, in the embodiment shown in FIG. 2, the other end of the current sensor CT71 can generate a sensing signal VCS2 to the conversion circuit 1052 during the PWM operation, so that the conversion circuit 1052 generates a second current signal C02 accordingly.

Further, please refer to FIG. 7A and FIG. 7B in combination. FIG. 7A and FIG. 7B are schematic circuit diagrams of the first embodiment and the second embodiment of the conversion circuit 1052, respectively. As shown in FIG. 7A, the conversion circuit 1052 includes a comparator. The two input terminals of the comparator respectively receive the sensing signal VCS1 and the predetermined voltage V1, and the conversion circuit 1052 converts the sensing signal VCS1 into a first current signal C01 according to the predetermined voltage V1. As shown in FIG. 7B, the conversion circuit 1052 may include another comparator. The two input terminals respectively receive the sensing signal VCS2 and the predetermined voltage V1. The conversion circuit 1052 converts the sensing signal VCS2 into the second current signal C02 according to the predetermined voltage V1. . In other embodiments, please refer to FIG. 7C. FIG. 7C is a schematic circuit diagram of the third embodiment of the conversion circuit. The two input terminals of another comparator included in the conversion circuit 1052 can also receive the sensing signals VCS1, VCS2, respectively. To generate a second current signal C02 by comparing the sensing signals VCS1 and VCS2.

Please refer to FIG. 8A and FIG. 8B together. FIG. 8A and FIG. 8B are waveform diagrams of one embodiment of the sensing signal VCS1 and the first current signal C01, and one embodiment of the sensing signal VCS2 and the second current signal C02, respectively. In the waveform diagram, as shown in FIG. 8A, when the sensing signal VCS1 is greater than the predetermined voltage V1, it indicates that the current flowing through the coil 1043 exceeds the current corresponding to the predetermined voltage V1, and the first current signal C01 will transition. As shown in FIG. 8B, when the sensing signal VCS2 is greater than the predetermined voltage V1, it indicates that the magnitude of the current flowing through the coil 1043 exceeds the magnitude of the current corresponding to the predetermined voltage V1, and the second current signal C02 will transition.

9A and 9B are schematic circuit diagrams of one embodiment of the phase detection unit 106, and FIG. 10 is an implementation of one of the switch control signals GATA1, GATA2, current signals C01, C02, phase signals PHASE1, PHASE2, and protection signals PROTECT1, PROTECT2 Example waveform diagram. Please refer to FIG. 1, FIG. 2, FIG. 9A, FIG. 9B, and FIG. 10 together. The phase detection unit 106 includes a detection circuit 1061 and a protection circuit 1062. The detection circuit 1061 is coupled to the coil current detection unit 105 and the protection circuit 1062. And is coupled between the pulse generating unit 102 and the protection circuit 1062. As shown in FIG. 9A, in order to generate the protection signal PROTECT1, the detection circuit 1061 receives the first current signal C01 generated by the coil current detection unit 105 and the switch control signal GATA1 generated by the pulse generation unit 102.

During the PWM operation, the detection circuit 1061 detects the negative edge of the switch control signal GATA1. When the detection circuit 1061 detects the negative edge of the switch control signal GATA1, the detection cycle starts, and the detection circuit 1061 is in the detection cycle. The negative edge of the internal switch control signal GATA1 generates a phase signal PHASE1 with a high potential according to the first current signal C01 with a high potential, until the detection circuit 1061 detects the negative edge of the first current signal C01 within a detection period. The detection circuit 1061 initially generates a phase signal PHASE1 with a low potential.

Similarly, as shown in FIG. 9B, in order to generate the protection signal PROTECT2, the detection circuit 1061 receives the second current signal C02 generated by the coil current detection unit 105 and the switch control signal GATA2 generated by the pulse generation unit 102. During the PWM operation, the detection circuit 1061 detects the negative edge of the switch control signal GATA2, and the detection cycle begins. When the detection circuit 1061 detects the negative edge of the switch control signal GATA2 within the detection cycle, the detection circuit 1061 The negative edge of the switch control signal GATA2 generates a phase signal PHASE2 with a high potential according to the second current signal C02 with a high potential, until the detection circuit 1061 detects the negative edge of the second current signal C02, and the detection circuit 1061 starts Generates a phase signal PHASE2 with a low potential.

Here, the protection circuit 1062 can receive the phase signal PHASE1 or both the phase signal PHASE1 and the phase signal PHASE2. During the PWM operation, the protection circuit 1062 generates a protection signal PROTECT1 with a high potential according to whether the time width of the phase signal PHASE1 at the high potential is equal to zero or whether the first time width T1 is smaller than the first preset time width TTH1. Similarly, during the PWM operation, the protection circuit 1062 generates a protection signal PROTECT2 with a high potential according to whether the time width of the phase signal PHASE2 at the high potential is equal to zero or whether the second time width T2 is smaller than the second preset time width TTH2. In detail, if the time width of the phase signal PHASE1 is equal to zero or the first time width T1 is smaller than the first preset time width TTH1, the protection circuit 1062 generates a protection signal PROTECT1 with a high potential; if the phase signal PHASE2 is at a high potential The time width is equal to zero or the second time width T2 is smaller than the second preset time width TTH2, and the protection circuit 1062 generates a protection signal PROTECT2 with a high potential.

The control unit 107 receives the protection signal PROTECT1 generated by the protection circuit 1062 or the protection signal PROTECT1 and the protection signal PROTECT2 generated by the protection circuit 1062. The control unit 107 determines whether the potential of the protection signal PROTECT1 has a high potential, that is, determines whether the time width of the phase signal PHASE1 at the high potential is equal to zero or the first time width T1 is less than the first preset time by the potential of the protection signal PROTECT1 Width TTH1. When the control unit 107 determines that the potential of the protection signal PROTECT1 has a high potential, the control unit 107 further controls the pulse generating unit 102 so that the current flowing through the coil 1043 is reduced and the electromagnetic induction heating device is operated in the inductive operation interval II. Similarly, the control unit 107 determines whether the potential of the protection signal PROTECT2 has a high potential, that is, the potential of the protection signal PROTECT2 is used to determine whether the time width of the phase signal PHASE2 at the high potential is equal to zero or whether the second time width T2 is less than the second The preset time width is TTH2. When the control unit 107 determines that the potential of the protection signal PROTECT2 has a high potential, the control unit 107 can control the pulse generating unit 102 to cause the current flowing through the coil 1043 to decrease or cause the current to stop flowing through the coil 1043, so that the electromagnetic induction heating device operates at Inductive operating range II.

In an embodiment, the protection circuit 1062 may further perform timing to calculate a first time width T1 of the phase signal PHASE1 at a high potential and a second time width T2 of the phase signal PHASE2 at a high potential. In detail, the protection circuit 1062 includes a timer. During the PWM operation, the protection circuit 1062 starts counting from the positive edge of the phase signal PHASE1 until the negative edge of the phase signal PHASE1 stops timing and generates the phase signal PHASE1 at a high potential for the first time. Width T1. Similarly, during the PWM operation, the protection circuit 106 starts timing from the positive edge of the phase signal PHASE2 until the negative edge of the phase signal PHASE2 stops timing and generates the second time width T2 of the phase signal PHASE2 at a high potential. Based on this, the protection circuit 1062 can output the first time width T1 and the second time width T2 to the control unit 107, so that the control unit 107 calculates the time difference between the first time width T1 and the first preset time width TTH1 and calculates the second The time difference between the time width T2 and the second preset time width TTH2 is used to control the pulse generating unit 102 to generate a switch control signal with a corresponding frequency according to the aforementioned two time differences.

Based on the above embodiments, those with ordinary knowledge in the technical field should be able to understand that the high and low potentials mentioned in this case are merely examples, and the high and low potentials are interchangeable, and are not limited to the above embodiments.

In an embodiment, as shown in FIGS. 1 and 2, the electromagnetic induction heating device further includes a coil overcurrent detection unit 109. The coil overcurrent detection unit 109 is coupled between the sensing circuit 1051 of the coil current detection unit 105 and the control unit 107. The coil overcurrent detection unit 109 can determine whether the magnitude of the current flowing through the coil 1043 is greater than a preset value. FIG. 11 is a schematic circuit diagram of an embodiment of the coil overcurrent detection unit 109, and FIG. 11 uses the coil overcurrent detection unit 109 to receive a sensing signal VCS1 as an example. As shown in FIG. 11, the coil overcurrent detection unit 109 may include a comparator. One input terminal of the comparator receives the predetermined voltage V2, and the other input terminal of the comparator receives the sensing signal VCS1 generated by the sensing circuit 1051. The coil The overcurrent detection unit 109 compares the sensing signal VCS1 with a predetermined voltage V2 to convert the sensing signal VCS1 which is an analog signal into an overcurrent signal OCP1 which is a digital signal. Among them, FIG. 12 is a waveform diagram of an embodiment of the coil overcurrent detection unit 109. As shown in FIG. 12, when the sensing signal VCS1 is greater than a predetermined voltage V2, the overcurrent signal OCP1 has a high potential, indicating that it flows through the coil 1043 The magnitude of the current exceeds the magnitude of the current corresponding to the predetermined voltage V2 (ie, the aforementioned preset value). Here, the control unit 107 can control the pulse generating unit 102 to stop generating the switch control signal GATA1 and the switch control signal GATA2 according to whether the overcurrent signal OCP1 has a high potential, or control the pulse generating unit 102 to generate other switch controls with a higher frequency. Signal. On the other hand, during the PWM operation, the coil overcurrent detection unit 109 can also receive the sensing signal VCS2, and convert the sensing signal VCS2 into an overcurrent signal OCP2 according to a predetermined voltage V2, so that the control unit 107 further detects the The OCP2 control pulse generating unit 102 is not repeated here.

Furthermore, as shown in FIGS. 1 and 2, the electromagnetic induction heating device further includes a power supply overvoltage detection unit 110. Please refer to FIG. 1 and FIG. 13 together. FIG. 13 is a schematic circuit diagram of an embodiment of the power supply over-voltage detection unit 110. The power overvoltage detection unit 110 is coupled to the positive terminal 1001 and the negative terminal 1002 of the power input terminal 100, and the power overvoltage detection unit 110 is coupled between the power input terminal 100 and the control unit 107. The power overvoltage detection unit 110 can determine whether the terminal voltage between the two ends of the power input terminal 100 is greater than a preset value. In detail, the power supply overvoltage detection unit 110 receives a voltage signal VAC0 from the positive terminal 1001, and receives a voltage signal VAC1 from the negative terminal 1002. The power supply overvoltage detection unit 110 includes a comparator. The power supply overvoltage detection unit 110 generates a corresponding voltage signal VAC according to the voltage of the voltage signal VAC0 and the voltage signal VAC1. The voltage signal VAC is then input to the positive end of the comparator. The comparator The voltage signal VAC is compared with a predetermined voltage V3 (ie, the aforementioned preset value) and an over-voltage signal OVP which is a digital signal is generated to indicate whether the voltage signal VAC is greater than the predetermined voltage V3. Here, the control unit 107 receives the voltage signal VAC and the overvoltage signal OVP from the power overvoltage detection unit 110, and determines whether to control the pulse generation unit 102 to stop generating the switch control signal GATA1 according to the potential levels of the voltage signal VAC and the overvoltage signal OVP. , GATA2, or other switch control signals with corresponding frequency.

Further, the electromagnetic induction heating device further includes a power supply current detection unit 111, and the power supply current detection unit 111 is coupled between one end of the power input terminal 100 (for example, the negative terminal 1002) and the control unit 107. The current detection unit 111 can determine whether the current flowing through one end of the power input terminal 100 is greater than a preset value. The current detection unit 111 includes a sensing circuit 1111 and a conversion circuit 1112. The sensing circuit 1111 and the sensing circuit 1052 may have the same circuit structure, and the conversion circuit 1112 and the conversion circuit 1052 may have the same circuit structure, and details are not described herein again. Taking the aforementioned negative terminal 1002 as an example, the sensing circuit 1111 senses the current flowing through the negative terminal 1002 and generates a sensing signal VCS3 which is an analog signal. The conversion circuit 1112 converts the sensing signal VCS3 into a system based on a predetermined voltage. The overcurrent signal OCP3 of the digital signal is used to indicate whether the current of the sensing signal VCS3 exceeds the current corresponding to the predetermined voltage (that is, the aforementioned default value). Based on this, the control unit 107 receives the overcurrent signal OCP3 and the sensing signal VCS3 and determines whether to control the pulse generating unit 102 to stop generating the switch control signal GATA1 and the switch control signal GATA2 according to the potential levels of the overcurrent signal OCP3 and the sensing signal VCS3, or Generate other switching control signals with corresponding frequencies.

Further, as shown in FIGS. 1 and 2, the electromagnetic induction heating device further includes a load detection unit 112. The load detection unit 112 is coupled between the coil current detection unit 105 and the control unit 107. The load detection unit 112 may perform counting within a preset fixed time to count the number of pulse wave generation times of the first current signal C01 and / or the number of pulse wave generation times of the second current signal C02. The load detection unit 112 outputs the aforementioned pulse wave generation times to the control unit 107, so that the control unit 107 can determine whether or not a load is placed on the electromagnetic induction based on the pulse current generation times of the first current signal C01 and / or the second current signal C02. Heating device, or determine what kind of load is placed in the electromagnetic induction heating device to control the pulse generating unit 102 to generate a switch control signal GATA1, GATA2 with the corresponding frequency, or to maintain the standby state without controlling the pulse generating unit 102 to switch Control signal.

In an embodiment, as shown in FIGS. 1 and 2, the electromagnetic induction heating device further includes a driving unit 108, and the driving unit 108 is coupled between the pulse generating unit 102 and the switching unit 103. The driving unit 108 includes a first driving circuit 1081 and a second driving circuit 1082. The first driving circuit 1081 is coupled to the first switch 1031, and the second driving circuit 1082 is coupled to the second switch 1032. The first driving circuit 1081 receives the switch control signal GATA1 generated by the pulse generating unit 102 and boosts it to drive the first switch 1031 to be turned on. The second driving circuit 1082 receives the switch control signal GATA2 generated by the pulse generating unit 102 and boosts it to drive the second switch 1032 to be turned on.

In one embodiment, the power conversion unit 101 may further include a fuse coupled between the positive terminal 1001 and the negative terminal 1002 of the power input terminal 100.

In one embodiment, the electromagnetic induction heating device may be an electromagnetic rice cooker, an electromagnetic water heater, an electromagnetic mixer, an electromagnetic teapot, or an electromagnetic fire boiler.

To sum up, according to an embodiment of the electromagnetic induction heating device and the protection control circuit of the present case, the electromagnetic induction heating device can immediately detect whether the electromagnetic induction heating device is operating in an inductive operating area to automatically adjust the switch control The signal cycle, and the electromagnetic induction heating device has multiple circuit protection mechanisms, so it can prevent the electromagnetic induction heating device from burning out and improve its safety. Furthermore, the working state of the electromagnetic induction heating device is continuous. The electromagnetic induction heating device can adjust the problem of power imbalance and is relatively power-saving. Further, the magnetic induction heating device can also be implemented with a lower cost circuit, reducing its production cost.

Although this case has been disclosed with examples as above, it is not intended to limit this case. Any person with ordinary knowledge in the technical field can make some changes and retouching without departing from the spirit and scope of this case. Therefore, the scope of protection of this case Subject to the scope of the attached patent application.

100‧‧‧Power input terminal

1001‧‧‧Positive Extreme

1002‧‧‧ Negative terminal

101‧‧‧ Power Conversion Unit

1011‧‧‧ Rectifier Unit

1012‧‧‧Filter unit

102‧‧‧Pulse generating unit

1021‧‧‧PWM generation circuit

1022‧‧‧ Complementary PWM generating circuit

1023‧‧‧ Delay Control Circuit

1024‧‧‧Polarity control circuit

103‧‧‧Switch unit

1031‧‧‧First switch

1032‧‧‧Second switch

104‧‧‧Resonant unit

1041‧‧‧First capacitor

1042‧‧‧Second capacitor

1043‧‧‧coil

105‧‧‧coil current detection unit

1051‧‧‧sensing circuit

1052‧‧‧ Conversion circuit

106‧‧‧phase detection unit

1061‧‧‧detection circuit

1062‧‧‧Protection circuit

107‧‧‧Control unit

108‧‧‧Drive unit

1081‧‧‧first drive circuit

1082‧‧‧Second driving circuit

109‧‧‧coil overcurrent detection unit

110‧‧‧Power overvoltage detection unit

111‧‧‧Power current detection unit

1111‧‧‧sensing circuit

1112‧‧‧ Conversion circuit

112‧‧‧Load detection unit

AT0‧‧‧PWM signal

AT1‧‧‧PWM signal

AB0‧‧‧PWM signal

AB1‧‧‧PWM signal

C01‧‧‧First current signal

C02‧‧‧Second current signal

CT71‧‧‧Current Detector

DT0‧‧‧ Delay time

DT1‧‧‧ Delay time

GATA1‧‧‧The first switch control signal

GATA2‧‧‧Second switch control signal

N1‧‧‧First connection point

N2‧‧‧Second connection point

OVP‧‧‧ Over-voltage signal

OCP1‧‧‧ overcurrent signal

OCP2‧‧‧ Overcurrent signal

OCP3‧‧‧ overcurrent signal

PHASE1‧‧‧phase signal

PHASE2‧‧‧phase signal

PROTECT1‧‧‧Protection signal

PROTECT2‧‧‧Protection signal

R71‧‧‧Resistor

R72‧‧‧Resistor

R73‧‧‧Resistor

S1‧‧‧pulse generation control signal

S2‧‧‧PWM signal

T1‧‧‧First time width

T2‧‧‧Second time width

TTH1‧‧‧First preset time width

TTH2‧‧‧Second preset time width

V1‧‧‧ predetermined voltage

V2‧‧‧ predetermined voltage

V3‧‧‧ predetermined voltage

VAC0‧‧‧Voltage signal

VAC1‧‧‧voltage signal

VAC‧‧‧Voltage signal

VCS1‧‧‧ sensing signal

VCS2‧‧‧Sensing signal

VCS3‧‧‧ sensing signal

I, II‧‧‧ Operation interval

[Figure 1] A schematic circuit diagram of an embodiment of an electromagnetic induction heating device according to the present case. [Figure 2] A schematic circuit diagram of another embodiment of the electromagnetic induction heating device according to the present case. [Fig. 3] It is a schematic diagram of an embodiment of an operation interval of an electromagnetic induction heating device. [Figure 4] A schematic circuit diagram of an embodiment of a pulse generating unit. [Fig. 5] It is a waveform diagram of each signal generated by each circuit of the pulse generating unit shown in Fig. 4. [FIG. 6] A schematic circuit diagram of an embodiment of a sensing circuit. [FIG. 7A] A schematic circuit diagram of the first embodiment of the conversion circuit. [FIG. 7B] A schematic circuit diagram of a second embodiment of the conversion circuit. 7C is a circuit diagram of a third embodiment of the conversion circuit. [FIG. 8A] A waveform diagram of an embodiment of the sensing signal and the first current signal. [FIG. 8B] A waveform diagram of an embodiment of the sensing signal and the second current signal. [FIG. 9A] A schematic circuit diagram of an embodiment of a phase detection unit. [FIG. 9B] A schematic circuit diagram of another embodiment of the phase detection unit. [Fig. 10] It is a waveform diagram of an embodiment of a switch control signal, a current signal, a phase signal and a protection signal. [FIG. 11] A schematic circuit diagram of an embodiment of a coil overcurrent detection unit. [Fig. 12] A waveform diagram of an embodiment of the coil overcurrent detection unit. [Figure 13] A schematic circuit diagram of an embodiment of a power supply overvoltage detection unit.

Claims (14)

An electromagnetic induction heating device includes: a power input terminal for receiving an AC power source; a power conversion unit for generating a DC power source according to the AC power source; a pulse generating unit for generating a first switch control signal And a second switch control signal, the first switch control signal and the second switch control signal are pulse width modulation signals; a switch unit, coupled to the pulse generation unit, includes: a first switch for The first switch controls the signal to be turned on; and a second switch is coupled to the first switch for selectively conducting to the first switch according to the second switch control signal to be turned on; a resonance unit is coupled Between the power conversion unit and the switch unit, a first capacitor is included; a second capacitor is coupled to the first capacitor; and a coil is coupled between the first switch and the second switch. Between a first connection point and a second connection point between the first capacitor and the second capacitor, the coil is used to drive the electromagnetic induction heating device to perform heating according to the DC power source. Heat; a coil current detection unit coupled to the coil to generate a current signal according to the current flowing through the coil; a phase detection unit coupled to the pulse generation unit and the coil current detection unit to detect Measuring a time width between the negative edge of any of the first switch control signal and the second switch control signal and the negative edge of the current signal; and a control unit for determining whether the time width is equal to zero or Whether the time width is less than a preset time width controls the pulse generating unit to perform a protection control. The electromagnetic induction heating device according to claim 1, wherein the current signal includes a first current signal and a second current signal, and the time width includes a first time width and a second time width; wherein the phase detection The detecting unit detects the first time width between the negative edge of the first switch control signal and the negative edge of the first current signal, and detects the negative edge of the second switch control signal and the second current signal The second time width between the negative edges, the control unit according to whether the first time width is equal to zero or whether the first time width is less than a first preset time width, and whether the second time width is equal to zero or the first time width Whether the two time widths are smaller than a second preset time width controls the pulse generating unit to execute the protection control. The electromagnetic induction heating device according to claim 1 or 2, wherein in the protection control, the control unit controls the pulse generating unit to stop generating the first switch control signal and the second switch control signal, or controls the pulse The generating unit generates a third switch control signal to the first switch and generates a fourth switch control signal to the second switch, wherein the frequency of the third switch signal is greater than the frequency of the first switch control signal, and the fourth The frequency of the switch control signal is greater than the frequency of the second switch control signal. The electromagnetic induction heating device according to claim 1 or 2, further comprising a coil overcurrent detection unit coupled between the coil current detection unit and the control unit, and the coil overcurrent detection unit is used to determine Whether the magnitude of the current flowing through the coil is greater than a preset value. The electromagnetic induction heating device according to claim 1 or 2, further comprising a power supply overvoltage detection unit coupled between the power input terminal and the control unit. The power supply overvoltage detection unit is used to determine the power supply. Whether the terminal voltage between the two ends of the input terminal is greater than a preset value. The electromagnetic induction heating device according to claim 1 or 2, further comprising a power current detection unit coupled between one end of the power input terminal and the control unit. The power current detection unit is used to determine the current. Whether the current passing through one of the power input terminals is greater than a preset value. The electromagnetic induction heating device as described in claim 1 or 2, further comprising a load detection unit coupled between the coil current detection unit and the control unit, and the load detection unit is used to The number of pulse wave generations determines whether a load is placed on the electromagnetic induction heating device or what kind of load is placed on the electromagnetic induction heating device. The electromagnetic induction heating device according to claim 1 or 2, further comprising a driving unit coupled between the switching unit and the pulse generating unit, the driving unit is configured to drive the first according to the first switch control signal The switch is turned on and the second switch is driven to be turned on according to the second switch control signal. The electromagnetic induction heating device according to claim 2, wherein the phase detection unit detects the negative edge of the first current signal within a detection period after detecting the negative edge of the first switch control signal, The negative edge of the second current signal is detected in another detection period after the negative edge of the second switch control signal is detected to detect the first time width and the second time width. The electromagnetic induction heating device according to claim 1 or 2, wherein a delay time is different between a signal change edge of the first switch control signal and another signal change edge of the second switch control signal. The electromagnetic induction heating device according to claim 2, wherein in the protection control, the control unit controls the pulse generating unit to generate a corresponding frequency according to a time difference between the first time width and the first preset time width. One of the third switching control signals, and controlling the pulse generating unit to generate a fourth switching control signal having a corresponding frequency according to another time difference between the second time width and the second preset time width, wherein the third The frequency of the switch signal is greater than the frequency of the first switch control signal, and the frequency of the fourth switch control signal is greater than the frequency of the second switch control signal. A protection control circuit suitable for an electromagnetic induction heating device includes: a pulse generating unit for generating a first switch control signal and a second switch control signal; the first switch control signal and the second switch control signal are Is a pulse width modulation signal; a switching unit coupled to the pulse generating unit includes: a first switch for controlling signal conduction according to the first switch; and a second switch coupled to the first switch for To selectively conduct conduction with the first switch according to the control signal of the second switch; a resonance unit coupled to the switch unit including: a first capacitor; a second capacitor coupled to the first switch A capacitor; and a coil coupled between a first connection point between the first switch and the second switch and a second connection point between the first capacitor and the second capacitor. The electromagnetic induction heating device is driven to be heated according to a DC power supply; a coil current detection unit is coupled to the coil to generate a current signal according to the current flowing through the coil; a phase detection unit Coupled to the pulse generating unit and the coil current detection unit to detect a negative edge between any of the first switch control signal and the second switch control signal and the negative edge of the current signal A time width; and a control unit for controlling the pulse generating unit to perform a protection control according to whether the time width is equal to zero or whether the time width is less than a preset time width. The protection control circuit according to claim 12, wherein the current signal includes a first current signal and a second current signal, the time width includes a first time width and a second time width; wherein the phase detection The unit detects the first time width between the negative edge of the first switch control signal and the negative edge of the first current signal, and detects the negative edge of the second switch control signal and the second current signal. The second time width between negative edges, the control unit is based on whether the first time width is equal to zero or whether the first time width is less than a first preset time width, and whether the second time width is equal to zero or the second Whether the time width is smaller than a second preset time width controls the pulse generating unit to execute the protection control. The protection control circuit according to claim 12 or 13, wherein in the protection control, the control unit controls the pulse generation unit to stop generating the first switch control signal and the second switch control signal, or controls the pulse generation The unit generates a third switch control signal to the first switch and a fourth switch control signal to the second switch, wherein the frequency of the third switch signal is greater than the frequency of the first switch control signal, and the fourth switch The frequency of the control signal is greater than the frequency of the second switch control signal.