阅读说明：本技术 用于烹饪器具的控制方法和烹饪器具 (Control method for cooking appliance and cooking appliance ) 是由 姚斌 樊杜平 于 2020-03-25 设计创作，主要内容包括：本发明公开了一种烹饪器具的控制方法以及烹饪器具。烹饪器具包括市电供电模块、谐振电路、控制模块以及功率管,控制方法包括：根据烹饪器具当前所需的加热功率确定功率管在市电供电模块的输出电压处于峰值时的基准导通时长T-(基准)；并基于基准导通时长T-(基准)对功率管的导通时长进行补偿,使得功率管在市电供电模块的输出电压从最小值增加到峰值的过程中导通时长逐渐减小,在输出电压从峰值减小到最小值的过程中导通时长逐渐增加。根据本发明的烹饪器具以及控制方法,能够实现在功率不变的情况下降低功率管工作时的峰值电流及峰值反压的目的,从而有效地延长了功率管的寿命,并保护了谐振电路。(The invention discloses a cooking appliance and a control method thereof. The cooking utensil comprises a mains supply module, a resonance circuit, a control module and a power tube, and the control method comprises the following steps: determining the reference conduction time length T of the power tube when the output voltage of the mains supply module is at the peak value according to the currently required heating power of the cooking appliance Datum (ii) a And based on the reference on-time T Datum The conduction duration of the power tube is compensated, so that the conduction duration of the power tube is gradually reduced in the process that the output voltage of the mains supply module is increased from the minimum value to the peak value, and the conduction duration is gradually increased in the process that the output voltage is decreased from the peak value to the minimum value. According to the cooking utensil and the control method, the aim of reducing the peak current and the peak back pressure of the power tube during working under the condition of unchanged power can be fulfilled, so that the service life of the power tube is effectively prolonged, and a resonant circuit is protected.)

1. A control method for a cooking appliance, characterized in that the cooking appliance comprises:

a mains supply module;

the resonance circuit is electrically connected with the mains supply power supply module;

the control module is electrically connected with the commercial power supply module;

the power tube is connected between a ground end and the resonant circuit, is connected with the output end of the control module, and is used for executing on-off operation according to the pulse width modulation signal sent by the control module so as to control the working state of the resonant circuit;

the control method comprises the following steps:

determining the reference conduction time length T of the power tube when the output voltage of the mains supply module is at the peak value according to the currently required heating power of the cooking appliance_Datum；

Dividing the process of increasing the output voltage of the mains supply module from the minimum value to the peak value into N stages based on the reference conduction time length T_DatumCompensating the conduction duration of the power tube in each stage, so that the conduction durations of the power tube in the N stages are as follows in sequence: t is_Datum+t₁、T_Datum+t₂、T_Datum+t₃…T_Datum+t_n；

Dividing the process of reducing the output voltage of the mains supply module from the peak value to the minimum value into N stages based on the reference conduction time length T_DatumCompensating the conduction duration of the power tube in each stage to ensure thatThe conduction duration of the power tube at the N stages is as follows in sequence: t is_Datum+t_n、T_Datum+t_n-1、T_Datum+t_n-2…、T_Datum+t₂、T_Datum+t₁；

Wherein, t₁、t₂、t_n-1、t_nFor the compensation of the power transistor, and t₁＞t₂＞…＞t_n-1＞t_n；2≤N≤30。

2. The control method for the cooking appliance according to claim 1, wherein the mains supply module includes a mains zero-crossing detection circuit, and the determination that the output voltage of the mains supply module reaches a peak value includes:

determining the commercial power frequency f according to the time difference of two continuous zero-crossing signals detected by the commercial power zero-crossing detection circuit;

determining a mains voltage period T according to the mains frequency f;

and determining that the output voltage reaches a peak value after the time length T of 1/4T begins to pass when the zero-crossing detection circuit detects the zero-crossing signal according to the mains voltage period T.

3. Control method for a cooking appliance according to claim 1, characterized in that the compensation conduction time period t of the power tube₁Satisfies the following conditions: t is less than or equal to 5 mu s₁≤25μs。

4. Control method for a cooking appliance according to claim 1, characterized in that the compensation conduction time period t of the power tube_n＝0。

5. Control method for a cooking appliance according to claim 1, characterized in that said compensation conduction time t₁、t₂、t_n-1、t_nForming an arithmetic progression.

6. The control method for a cooking appliance according to claim 1, wherein the on-time of the power tube is controlled by adjusting a duty ratio of a pulse width modulation signal transmitted to the power tube.

7. The control method for a cooking appliance according to claim 6, wherein a difference between duty ratios of the pulse width modulation signals of adjacent stages is constant.

8. A cooking appliance, characterized in that it comprises:

a mains supply module;

the resonance circuit is connected with the mains supply module;

the control module is connected with the commercial power supply module; and

the power tube is connected between a ground end and the resonant circuit, is connected with the output end of the control module, and is used for executing on-off operation according to the pulse width modulation signal sent by the control module so as to control the working state of the resonant circuit;

the control module is configured to control the cooking appliance to perform the steps of the control method of any one of claims 1-7.

Technical Field

The invention relates to the technical field of cooking appliances, in particular to a control method of a cooking appliance and the cooking appliance.

Background

The existing electromagnetic heating method generally adopts a fixed-frequency fixed-pulse-width method to drive an Insulated Gate Bipolar Transistor (IGBT) to control the charging and discharging process of a resonant circuit under constant power. However, since the rectified voltage of the utility power still changes with time, when the ac peak value is high, and further the voltage input to the resonant circuit is high, and the peak voltage and the peak current at the time of resonance are large, the IGBT is still turned on in a fixed pulse width manner, so that a large peak current flows when the IGBT is turned on, and a high reverse voltage is also applied after the IGBT is turned off, thereby easily damaging the IGBT. Meanwhile, the temperature rise of the coil panel is obvious, and the aging and the failure of the enameled wire are accelerated.

Therefore, it is desirable to provide a control method of a cooking appliance and a cooking appliance to at least partially solve the above problems.

Disclosure of Invention

In this summary, concepts in a simplified form are introduced that are further described in the detailed description. This summary of the invention is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. Reduction of peak current

An aspect of the present invention provides a method of controlling a cooking appliance, the cooking appliance including:

a mains supply module; the resonance circuit is electrically connected with the mains supply power supply module; the control module is electrically connected with the commercial power supply module; the power tube is connected between a ground end and the resonant circuit, is connected with the output end of the control module, and is used for executing on-off operation according to the pulse width modulation signal sent by the control module so as to control the working state of the resonant circuit;

the control method comprises the following steps:

determining the reference conduction time length T of the power tube when the output voltage of the mains supply module is at the peak value according to the currently required heating power of the cooking appliance_Datum；

Dividing the process of increasing the output voltage of the mains supply module from the minimum value to the peak value into N stages based on the reference conduction time length T_DatumCompensating the conduction duration of the power tube in each stage, so that the conduction durations of the power tube in the N stages are as follows in sequence: t is_Datum+t₁、T_Datum+t₂、T_Datum+t₃…T_Datum+t_n；

Dividing the process of reducing the output voltage of the mains supply module from the peak value to the minimum value into N stages based on the reference conduction time length T_DatumCompensating the conduction duration of the power tube in each stage, so that the conduction durations of the power tube in the N stages are as follows in sequence: t is_Datum+t_n、T_Datum+t_n-1、T_Datum+t_n-2…、T_Datum+t₂、T_Datum+t₁；

Wherein, t₁、t₂、t_n-1、t_nFor the compensation of the power transistor, and t₁＞t₂＞…＞t_n-1＞t_n；2≤N≤30。

According to the control method, the reference conduction time length T can be based on_DatumThe power tube is controlled to have longer conduction time in a low-voltage area, and the power tube is controlled to have shorter conduction time in a high-voltage area, so that the aim of reducing peak current and peak back voltage when the power tube works under the condition of unchanged power is fulfilled, the service life of the power tube is effectively prolonged, and a resonant circuit is protected.

Preferably, the utility power supply module includes a utility zero-crossing detection circuit, and the determination that the output voltage of the utility power supply module reaches the peak value includes:

determining the commercial power frequency f according to the time difference of two continuous zero-crossing signals detected by the commercial power zero-crossing detection circuit;

determining a mains voltage period T according to the mains frequency f;

and determining that the output voltage reaches a peak value after the time length T of 1/4T begins to pass when the zero-crossing detection circuit detects the zero-crossing signal according to the mains voltage period T.

Thereby, it can be accurately derived when the mains voltage reaches a peak value.

Preferably, the power tubeCompensated on-time t₁Satisfies the following conditions: t is less than or equal to 5 mu s₁≤25μs。

Therefore, the conduction time of the power tube can be better adjusted.

Preferably, the compensation conduction time length t of the power tube_n＝0。

Therefore, the peak current and the peak back pressure when the power tube works can be effectively reduced.

Preferably, the compensation conduction time t₁、t₂、t_n-1、t_nForming an arithmetic progression.

Therefore, the conduction time of the power tube can be uniformly adjusted.

Preferably, the conduction time of the power tube is controlled by adjusting the duty ratio of the pulse width modulation signal sent to the power tube.

Therefore, the conduction time of the power tube can be conveniently adjusted.

Preferably, the difference between the duty cycles of the pulse width modulation signals of adjacent stages is constant.

Thereby, the duty ratio of the pulse width modulation signal can be uniformly adjusted.

Another aspect of the present invention provides a cooking appliance, including:

a mains supply module;

the resonance circuit is connected with the mains supply module;

the control module is connected with the commercial power supply module; and

the power tube is connected between a ground end and the resonant circuit, is connected with the output end of the control module, and is used for executing on-off operation according to the pulse width modulation signal sent by the control module so as to control the working state of the resonant circuit;

the control module is configured to control the cooking appliance to perform the steps of the control method of any of the above embodiments.

According to the cooking utensil of the invention, the conduction can be based on the referenceDuration T_DatumThe power tube is controlled to have longer conduction time in a low-voltage area, and the power tube is controlled to have shorter conduction time in a high-voltage area, so that the aim of reducing peak current and peak back voltage when the power tube works under the condition of unchanged power is fulfilled, the service life of the power tube is effectively prolonged, and a resonant circuit is protected.

Drawings

The following drawings of the invention are included to provide a further understanding of the invention. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

In the drawings:

fig. 1 is a schematic control circuit diagram of a cooking appliance according to a preferred embodiment of the present invention; and

fig. 2 is a current curve of a power tube compared with a conventional method after a control method of a cooking appliance according to a preferred embodiment of the present invention is used.

Detailed Description

In the following description, numerous specific details are set forth in order to provide a more thorough understanding of the present invention. It will be apparent, however, to one skilled in the art, that embodiments of the invention may be practiced without one or more of these specific details. In other instances, well-known features have not been described in detail so as not to obscure the embodiments of the invention.

It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the invention. As used herein, the singular is intended to include the plural unless the context clearly dictates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

Exemplary embodiments according to the present invention will now be described in more detail with reference to the accompanying drawings. These exemplary embodiments may, however, be embodied in many different forms and should not be construed as limited to only the embodiments set forth herein. It is to be understood that these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of these exemplary embodiments to those skilled in the art. In the drawings, the thicknesses of layers and regions are exaggerated for clarity, and the same elements are denoted by the same reference numerals, and thus the description thereof will be omitted.

The invention provides a control method for a cooking appliance and the cooking appliance. The cooking appliance of the invention can be an electric cooker, an electric pressure cooker and the like.

The cooking appliance may include a pot body and a lid. The cooker body can be provided with an inner pot containing part in a cylindrical shape (or other shapes), and the inner pot can be freely put into or taken out of the inner pot containing part so as to be convenient for cleaning the inner pot. The inner pot is generally made of a metal material and has a circular opening on an upper surface for containing a material to be heated, such as rice, soup, etc.

It can be understood that the inner pot and the inner pot receiving part of the pot body have corresponding shapes. For example, the inner pan comprises a body of revolution formed by a pan wall with an upper opening and an inner cavity, the body of revolution having a shape comprising the pan wall and a pan rim attached to the upper part of the pan body (disposed along the entire circumference of the pan body). The capacity of the inner pot is usually below 6 liters (L), for example, the capacity of the inner pot can be 2L or 4L.

The cover body is connected to the cooker body in an openable and closable manner and is used for covering the cooker body. When the cover body is covered on the cooker body, a cooking space is formed between the cover body and the inner pot. Optionally, the lid body may include an upper cover and a removable cover disposed between the upper cover and the pot body and detachably connected to the upper cover to facilitate cleaning of the removable cover at any time.

The pot body may further include a heating means for heating the inner pot. IH is an electromagnetic heating technology, for example, a household cooking appliance may use IH with an electromagnetic heating element at the bottom and around the cooking appliance to uniformly heat the food in the cooking appliance, and therefore, IH may also be called three-dimensional electromagnetic heating. The heating device in this embodiment may be configured to heat the inner pot in a manner that the coil panel L1 and the resonant capacitor C2 generate an alternating magnetic field.

As shown in fig. 1, the cooking appliance of the present invention specifically includes: commercial power supply module, resonant circuit, control module and power tube. These modules may be integrated on a main control circuit board of the cooking appliance.

In particular, the mains supply module may comprise a mains zero crossing detection circuit and a rectifier. The mains supply is connected to a mains supply zero-crossing detection circuit, rectified by a rectifier and filtered by a safety capacitor C1 to supply power to the resonant circuit.

The resonant circuit can be composed of a coil panel L1 and a resonant capacitor C2, and the inner pot is heated by the mode that the coil panel L1 and the resonant capacitor C2 generate an alternating magnetic field.

A power transistor (such as a transistor Q1) is connected between the ground and the resonant circuit, and the power transistor is connected to the output terminal of the control module for performing an on or off operation according to the pwm signal sent by the control module to control the operating state of the resonant circuit. The Control module may be a Micro Control Unit (MCU).

The cooking appliance may further include a temperature sensor configured to measure a temperature value in the cooking space. For example, the cooking appliance may comprise a bottom temperature sensor for sensing a bottom temperature of the inner pot and/or a top temperature sensor for sensing a top temperature of the inner pot. Wherein the top temperature sensor may be provided in the cover. The bottom temperature sensor and the top temperature sensor may be thermistors. Bottom temperature sensor and top temperature sensor all are connected to cooking utensil's control module, and the temperature signal feedback that will sense after the temperature of pot in the sensing to control module can realize more accurate control to the process of culinary art based on temperature signal.

It should be noted that although a partial structure of the cooking appliance is schematically described at this time, these lists are merely exemplary and cannot be construed as a structural limitation of the cooking appliance of the present invention.

The present invention also provides a control method for a cooking appliance, the method including: determining the reference conduction time length T of the power tube when the output voltage of the mains supply module is at the peak value according to the currently required heating power of the cooking appliance_Datum；

The process of increasing the output voltage of the commercial power supply module from the minimum value to the peak value is divided into N stages based on the reference conduction time length T_DatumCompensating the conduction duration of the power tube at each stage, so that the conduction duration of the power tube at the N stages is as follows in sequence: t is_Datum+t₁、T_Datum+t₂、T_Datum+t₃…T_Datum+t_n；

The process of reducing the output voltage of the mains supply module from the peak value to the minimum value is divided into N stages based on the reference conduction time length T_DatumCompensating the conduction duration of the power tube at each stage, so that the conduction duration of the power tube at the N stages is as follows in sequence: t is_Datum+t_n、T_Datum+t_n-1、T_Datum+t_n-2…、T_Datum+t₂、T_Datum+t₁；

Wherein, t₁、t₂、t_n-1、t_nFor the compensation of the power transistor, and t₁＞t₂＞…＞t_n-1＞t_n；2≤N≤30。

It can be understood that the larger N, the smoother the process of the current of the power tube from the minimum value to the peak current. The control module can store the heating power and the reference conduction time length T of the cooking utensil in advance_DatumIs the reference on-time T_DatumMay be pre-selected according to the desired heating power of the cooking appliance.

T during the process of increasing the output voltage of the mains supply module from a minimum value to a peak value_Datum+t₁＞T_Datum+t₂＞T_Datum+t₃…＞T_Datum+t_nIn the mains supply modeDuring the process of the output voltage of the block decreasing from the peak value to the minimum value, T_Datum+t_n＜T_Datum+t_n-1＜T_Datum+t_n-2…＜T_Datum+t₂＜T_Datum+t₁Thus, the reference on time period T can be based on_DatumThe power tube is controlled to have longer conduction time in a low-voltage area, and the power tube is controlled to have shorter conduction time in a high-voltage area, so that the aim of reducing peak current and peak back voltage when the power tube works under the condition of unchanged power is fulfilled, the service life of the power tube is effectively prolonged, and a resonant circuit is protected.

In particular, it is understood that: the on-time of the power tube is controlled by adjusting the duty ratio of the pulse width modulation signal sent to the power tube. That is, the on-time of each stage corresponds to a different duty ratio, and the larger the duty ratio is, the longer the on-time is.

Therefore, compared with the traditional fixed pulse width control mode, the pulse width modulation control method can gradually reduce the duty ratio of the pulse width modulation signal in the process of increasing the output voltage of the commercial power supply module; in the process of reducing the output voltage of the commercial power supply module, the duty ratio of the pulse width modulation signal is gradually increased, and the aim of reducing the peak current and the peak back pressure of the low-power tube during working under the condition of unchanged power can be achieved. Meanwhile, the duty ratio is gradually reduced and/or increased, and noise generated by devices in the circuit can be effectively avoided.

It is understood that the difference between the duty cycles of the pulse width modulation signals of adjacent stages may be a constant value or a non-constant value.

Specifically, in the above method, the determining that the output voltage of the mains supply module reaches the peak value may include:

determining the frequency f of the commercial power according to the time difference of two continuous zero-crossing signals detected by the commercial power zero-crossing detection circuit;

determining a mains voltage period T according to the mains frequency f;

and determining that the mains voltage reaches a peak value after the time length T of 1/4T begins to elapse when the mains zero-crossing detection circuit detects the zero-crossing signal according to the mains voltage period T.

Illustratively, if the rated operating frequency of the utility power detected by the utility power zero-crossing detection circuit is 50Hz, the period of the utility power voltage is 20ms, that is, the utility power voltage reaches the peak value after 5ms from the time when the utility power zero-crossing detection circuit detects the zero-crossing signal. In another real-time mode, if the rated operating frequency of the utility power is 60Hz, the period of the utility power voltage is 8.33ms, and the utility power voltage reaches the peak value after 4.165ms from the detection of the zero-crossing signal by the utility power zero-crossing detection circuit.

As an example, the quarter-cycle (the process of the output voltage of the mains supply module reaching the peak from the minimum value) is equally divided into 8 stages, that is, N is 8; the first, second, third … to eighth stages are carried out in sequence from the minimum value of the output voltage of the commercial power, and the corresponding duty ratios are the first duty ratio, the second duty ratio, the third duty ratio … to the eighth duty ratio. Due to T_Datum+t₁＞T_Datum+t₂＞T_Datum+t₃…＞T_Datum+t₈It is to be understood that the first duty cycle > the second duty cycle > the third duty cycle > … > the eighth duty cycle. The selection of the specific duty cycle value (determination of the on-time of the power tube) may be selected based on the change of the voltage in the resonant circuit to keep the current flowing through the power tube constant. In other embodiments, the compensation conducting time t may be₁、t₂、t_n-1、t_nForming an arithmetic progression.

More specifically, the on-time t is compensated_nMay be 0. It can be understood that when the output voltage of the utility power reaches the peak value, the on-time of the power tube is not compensated, so as to effectively reduce the peak current flowing through the power tube. In addition, after a plurality of experiments of the inventor, in order to keep the current flowing through the power tube constant, the compensation conduction time t of the power tube₁Preferably satisfies: t is less than or equal to 5 mu s₁≤25μs。

For the process of reducing the output voltage of the utility power supply module from the peak value to the minimum value, the process of gradually reducing the duty ratio of the pulse width modulation signal or gradually reducing the conduction time of the power tube is similar to the process of gradually increasing the duty ratio or gradually increasing the conduction time of the power tube, and for the sake of brevity, the detailed description is omitted.

Referring next to fig. 2, a waveform of an ac commercial power, a current curve of a power tube in a conventional constant pulse width control manner, and a current curve of a power tube using the control method of the present invention are shown.

It can be seen that the current peaks are significantly reduced and tend to be constant. It will be further appreciated that the amount of heat generated by the coil plate wire resistance is proportional to the square of the current, and therefore, a low current peak helps to reduce the heat generation of the coil plate.

For example, assuming that the inner pot is heated by using a conventional constant pulse width control method, the voltage of the commercial power is 200V, the rated power of the cooking appliance is 500W, if the instantaneous heating power is 200W, the instantaneous current is 1A (calculated according to the formula P ═ U ═ I), and if the instantaneous heating power is 800W, the corresponding instantaneous current is 4A, so that the calorific value Q ═ I of the coil disc in the period of time can be obtained²R ═ 1A × R +4A × R ═ 17R. When the control method of the invention is adopted to heat the inner pot, if the instant heating power is 500W, the instant current is 2.5A, the next instant heating power is still 500W, and the instant current is still 2.5A, the calorific value Q of the coil disc in the period is I²R ═ 2.5A × R +2.5A × R ═ 12.5R. From this, it can be derived that the heat generation amount of the coil disk is significantly reduced.

According to the control method and the cooking utensil of the invention, the reference conduction time length T can be used_DatumThe power tube is controlled to have longer conduction time in a low-voltage area, and the power tube is controlled to have shorter conduction time in a high-voltage area, so that the aim of reducing peak current and peak back voltage when the power tube works under the condition of unchanged power is fulfilled, the service life of the power tube is effectively prolonged, and a resonant circuit is protected.

The present invention has been illustrated by the above embodiments, but it should be understood that the above embodiments are for illustrative and descriptive purposes only and are not intended to limit the invention to the scope of the described embodiments. Furthermore, it will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, and that many variations and modifications may be made in accordance with the teachings of the present invention, which variations and modifications are within the scope of the present invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.