CN204810577U - Electromagnetic heating system and current detection and protection controlling means thereof - Google Patents

Abstract

The utility model discloses a current detection and protection control device of an electromagnetic heating system, comprising: a second rectification circuit for converting AC mains power into a second direct current; a zero-crossing detection circuit which detects the alternating current according to the second direct current The zero-crossing point of the mains power; the current detection circuit is used to detect the current of the IGBT; the controller, the controller starts to obtain the maximum current in each conduction cycle of the IGBT at the zero-crossing point of the AC mains, and the current conduction of the IGBT When the maximum current in the period is greater than the current protection threshold, the IGBT is controlled to be turned off by controlling the driving circuit. The current detection and protection control device can minimize the damage to the IGBT due to the cumulative effect. The utility model also discloses an electromagnetic heating system.

Description

Electromagnetic heating system and its current detection and protection control device

technical field

The utility model relates to an electromagnetic heating system, in particular to a current detection and protection control device of the electromagnetic heating system and an electromagnetic heating system.

Background technique

Generally, there are three current detection schemes for electromagnetic heating systems: (1) detection of AC mains through current transformers; (2) current detection of rectifier bridge stack ground wire; (3) IGBT (Insulated Gate Bipolar Transistor, insulated gate bipolar transistor) E pole current detection.

Among the above three detection schemes, if a current transformer is used to detect the AC mains, the cost is relatively high, and the pulse current of the E pole of the IGBT cannot be obtained in real time, so that real-time protection cannot be provided. If the rectifier bridge stack ground wire current detection scheme is adopted, the current of the IGBT cannot be obtained in real time, and real-time protection cannot be provided. The IGBT E-pole current detection scheme in the related art, as shown in Figure 1, although it can obtain the current of the IGBT in real time, needs a built-in operational amplifier circuit to amplify the current signal, and sends it to the main control after RC filtering. Units require many devices and complex circuits.

Therefore, it is necessary to improve the current detection scheme of the electromagnetic heating system.

Utility model content

The utility model aims to solve one of the technical problems in the related art at least to a certain extent. Therefore, an object of the present invention is to propose a current detection and protection control device for an electromagnetic heating system that can minimize the damage to the IGBT due to the cumulative effect.

Another purpose of the utility model is to provide an electromagnetic heating system.

In order to achieve the above purpose, the utility model proposes a current detection and protection control device for an electromagnetic heating system, the electromagnetic heating system includes a resonant circuit composed of IGBTs, and converts AC mains power into first DC power for supplying The first rectifier circuit of the resonant circuit, the drive circuit for driving the IGBT, the current detection and protection control device includes: a second rectifier circuit for converting the AC mains power into a second direct current; a zero-crossing detection circuit, the The zero-crossing detection circuit is connected with the second rectifier circuit, and the zero-crossing detection circuit detects the zero-crossing point of the AC mains according to the second direct current; the current detection circuit, the current detection circuit and the IGBT The E pole is connected, and the current detection circuit is used to detect the current of the IGBT; the controller is connected to the zero-crossing detection circuit, the current detection circuit and the drive circuit respectively, and the controller At the zero-crossing point of the AC mains, the maximum current in each conduction period of the IGBT is obtained, and when the maximum current in the current conduction period of the IGBT is greater than the current protection threshold, the controller passes The drive circuit is controlled to control the IGBT to turn off.

According to the current detection and protection control device of the electromagnetic heating system of the embodiment of the present invention, the AC mains power is converted into the second direct current through the second rectification circuit, and the zero-crossing detection circuit detects the zero-crossing point of the alternating current mains according to the second direct current, and controls The device obtains the maximum current in each conduction period of the IGBT through the current detection circuit at the zero crossing point of the AC mains, and when the maximum current in the current conduction period of the IGBT is greater than the current protection threshold, it controls the drive circuit to control The IGBT is turned off, thereby minimizing the IGBT damage caused by the cumulative effect, and has the advantages of simple structure, high reliability, and low cost.

Specifically, the above-mentioned current detection and protection control device of the electromagnetic heating system further includes an alarm connected to the controller, wherein the maximum current in the current conduction period of the IGBT is greater than the current protection When the threshold is reached, the controller also controls the alarm to send a warning message, and controls the electromagnetic heating system to shut down.

Specifically, when the times of obtaining the maximum current are greater than the preset times or the time of obtaining the maximum current reaches the preset time, if the maximum current in each conduction cycle of the IGBT is less than or equal to the current protection Threshold value, the controller accumulates the obtained maximum current in each conduction period and averages it to obtain the average current, and calculates the power of the electromagnetic heating system according to the average current, and converts the electromagnetic heating system The power is compared with the target power to adjust the conduction time of the IGBT in the next conduction period.

Specifically, if the power of the electromagnetic heating system is greater than the target power, the controller controls the driving circuit to reduce the conduction time of the IGBT in the next conduction period; if the electromagnetic heating system If the power is less than the target power, the controller controls the drive circuit to increase the conduction time of the IGBT in the next conduction period.

Preferably, the preset time is a half-wave cycle of the AC mains.

Specifically, the current detection circuit specifically includes: a sampling resistor, one end of the sampling resistor is connected to the E pole of the IGBT, and the other end of the sampling resistor is grounded; a filter resistor, one end of the filter resistor is respectively connected to the The E pole of the IGBT is connected to one end of the sampling resistor; a filter capacitor, one end of the filter capacitor is connected to the other end of the filter resistor, the other end of the filter capacitor is grounded, and one end of the filter capacitor is connected to the filter capacitor. There is a first node between the other ends of the filtering resistor, and the first node is connected to the controller.

In order to achieve the above purpose, another aspect of the utility model proposes an electromagnetic heating system, which includes the above-mentioned current detection and protection control device of the electromagnetic heating system.

The electromagnetic heating system can minimize the IGBT damage caused by the cumulative effect through the current detection and protection control device of the electromagnetic heating system, and has the advantages of simple structure, high reliability, and low cost.

Description of drawings

Fig. 1 is a current detection circuit diagram of an IGBT in a traditional electromagnetic heating system.

Fig. 2 is a schematic block diagram of a current detection and protection control device of an electromagnetic heating system according to an embodiment of the present invention.

Fig. 3 is a circuit diagram of a current detection and protection control device of an electromagnetic heating system according to an embodiment of the present invention.

Fig. 4 is a working flow chart of the current detection and protection control device of the electromagnetic heating system according to an embodiment of the present invention.

5a-5f are current waveform diagrams of an IGBT according to an embodiment of the present invention.

Fig. 6 is a flow chart of the current detection and protection control method of the electromagnetic heating system according to the embodiment of the present invention.

Detailed ways

Embodiments of the present invention are described in detail below, examples of which are shown in the drawings, wherein the same or similar reference numerals represent the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the figures are exemplary and are intended to explain the present invention, but should not be construed as limiting the present invention.

The current detection and protection control device and the electromagnetic heating system of the electromagnetic heating system proposed by the embodiment of the utility model are described below with reference to the accompanying drawings.

Fig. 2 is a schematic block diagram of a current detection and protection control device of an electromagnetic heating system according to an embodiment of the present invention, wherein the electromagnetic heating system includes a resonant circuit 10 composed of IGBTs, which converts AC mains power into first DC power for supply The first rectification circuit 20 of the resonant circuit 10 and the drive circuit 30 for driving the IGBT. As shown in FIG. 2 , the current detection and protection control device of the electromagnetic heating system includes a second rectification circuit 40 , a zero-crossing detection circuit 50 , a current detection circuit 60 and a controller 70 .

Wherein, the second rectification circuit 40 converts the AC mains power into a second direct current, and the zero-crossing detection circuit 50 is connected with the second rectification circuit 40, and the zero-crossing detection circuit 50 detects the zero-crossing point of the AC mains power according to the second direct current, and the current detection circuit 60 is connected to the E pole of the IGBT, and the current detection circuit 60 is used to detect the current of the IGBT. The controller 70 is connected to the zero-crossing detection circuit 50, the current detection circuit 60 and the driving circuit 30 respectively. Start to obtain the maximum current in each conduction period of the IGBT, and when the maximum current in the current conduction period of the IGBT is greater than the current protection threshold, the controller 70 controls the driving circuit 30 to control the IGBT to turn off.

In the embodiment of the present invention, the current protection threshold can be calibrated according to the actual situation.

According to an embodiment of the present utility model, the current detection and protection control device of the above-mentioned electromagnetic heating system also includes an alarm (not specifically shown in the figure), and the alarm is connected to the controller 70, wherein the current conduction of the IGBT When the maximum current in the cycle is greater than the current protection threshold, the controller 70 also controls the alarm to send out a warning message, and controls the electromagnetic heating system to shut down.

To put it simply, the zero-crossing detection circuit 50 detects in real time whether the AC mains power is zero-crossing, and when the zero-crossing detection circuit 50 detects the zero-crossing of the AC mains power, the current detection circuit 60 starts to obtain the maximum current in each conduction period of the IGBT . If the acquired maximum current in the current conduction period of the IGBT is greater than the current protection threshold, the controller 70 controls the driving circuit 30 to turn off the IGBT, thereby minimizing the damage to the IGBT due to the cumulative effect. At the same time, the controller 70 Control the alarm to send warning information, and control the shutdown of the electromagnetic heating system to stop heating, so as to protect the electromagnetic heating system from overcurrent.

According to an embodiment of the present invention, when the number of times of obtaining the maximum current is greater than the preset number of times or the time of obtaining the maximum current reaches the preset time, if the maximum current in each conduction cycle of the IGBT is less than or equal to the current protection threshold, The controller 70 accumulates and averages the obtained maximum current in each conduction period to obtain an average current, calculates the power of the electromagnetic heating system according to the average current, and compares the power of the electromagnetic heating system with the target power to adjust The conduction time of the IGBT in the next conduction cycle.

Wherein, the preset number of times and the preset time can be calibrated according to the actual situation. Preferably, the preset time can be a half-wave cycle of the AC mains.

According to an embodiment of the present invention, if the power of the electromagnetic heating system is greater than the target power, the controller 70 controls the drive circuit 30 to reduce the conduction time of the IGBT in the next conduction period; if the power of the electromagnetic heating system is less than the target power, the controller 70 controls the drive circuit 30 to increase the conduction time of the IGBT in the next conduction period.

Wherein, the target power can be calibrated according to the actual situation.

Specifically, when the zero-crossing detection circuit 50 detects the zero-crossing point of the AC mains, the current detection circuit 60 starts to obtain the maximum current in each conduction period of the IGBT. If the current detection circuit 60 obtains the maximum current in the current conduction period of the IGBT is less than or equal to the current protection threshold, the controller 70 records the maximum current, and the current detection circuit 60 continues to obtain the maximum current in the next conduction period of the IGBT. When the time for the current detection circuit 60 to obtain the maximum current is greater than the preset time, such as a half-wave cycle of AC mains power or the number of times to obtain the maximum current is greater than the preset number of times, the controller 70 calculates the maximum current within the preset time or the preset number of times The average value of the current is the average current, and the effective value of the current is calculated according to the following formula (1):

Y=A+BX(1)

Among them, Y is the effective value of current, A and B are coefficients, and X is the average current.

Then the controller 70 multiplies the calculated current effective value by the voltage effective value to obtain the power of the electromagnetic heating system, and compares the power of the electromagnetic heating system with the target power. If the calculated power of the electromagnetic heating system is greater than the target power, the controller 70 controls the drive circuit 30 to reduce the conduction time of the IGBT in the next conduction period; if the calculated power of the electromagnetic heating system is less than the target power, then the control The switch 70 controls the driving circuit 30 to increase the conduction time of the IGBT in the next conduction cycle, thereby realizing the power regulation of the electromagnetic heating system and ensuring the stable operation of the electromagnetic heating system according to the target power.

According to an embodiment of the present invention, as shown in Figure 3, the current detection circuit 60 specifically includes a sampling resistor RK1, a filter resistor R1 and a filter capacitor C1, wherein one end of the sampling resistor RK1 is connected to the E pole of the IGBT, and the sampling resistor RK1 The other end of the filter capacitor C1 is grounded to GND, one end of the filter resistor R1 is connected to the E pole of the IGBT and one end of the sampling resistor RK1, one end of the filter capacitor C1 is connected to the other end of the filter resistor RK1, the other end of the filter capacitor C1 is grounded to GND, and the filter capacitor There is a first node J1 between one end of C1 and the other end of the filter resistor R1 , and the first node J1 is connected to the controller 70 . The current detection circuit can obtain the current of the IGBT accurately and in real time, has a simple circuit structure and relatively high reliability, and is beneficial to the integration and cost reduction of the current detection and protection control devices of the electromagnetic heating system.

In addition, other circuit structures shown in FIG. 3 will not be described in detail here. The working process of the current detection and protection control device of the electromagnetic heating system is described below through Figure 4, which specifically includes the following steps:

S101, judging whether the AC mains has crossed zero. If yes, execute step S102; if no, return to step S101 to continue judging.

S102 , initializing the current reading parameter, and enabling the maximum current reading function in the conduction period of the IGBT.

S103, reading the maximum current in the current conduction period of the IGBT. As shown in Fig. 5a, the maximum current in each conduction cycle of the IGBT starts to be obtained at the zero-crossing point of the AC mains. It should be noted that FIG. 5b-FIG. 5f are partially enlarged diagrams of the current waveform diagram of the IGBT shown in FIG. 5a, so as to clearly understand the current waveform in the current conduction period of the IGBT.

S104, judging whether the maximum current in the current conduction period of the IGBT is smaller than the current protection threshold. If yes, execute step S105; if no, execute step S108.

S105, judging whether the preset number of times or a half-wave cycle of the AC mains is reached. If yes, execute step S106; if no, return to step S103 to continue reading.

S106, enter the current conversion function processing, calculate the average current and the power of the electromagnetic heating system, and control the conduction time of the IGBT in the next conduction cycle according to the power of the electromagnetic heating system.

S107, judging whether to shut down. If yes, execute step S108; if no, return to step S101 to continue judging.

S108, power off.

In summary, according to the current detection and protection control device of the electromagnetic heating system of the embodiment of the present invention, the AC mains power is converted into the second direct current through the second rectification circuit, and the zero-crossing detection circuit detects the AC mains power according to the second direct current. At the zero crossing point of the AC mains, the controller starts to obtain the maximum current in each conduction period of the IGBT through the current detection circuit at the zero crossing point of the AC mains, and when the maximum current in the current conduction period of the IGBT is greater than the current protection threshold, through The drive circuit is controlled to control the IGBT to turn off, thereby minimizing the IGBT damage caused by the cumulative effect, and has the advantages of simple structure, high reliability, and low cost.

In addition, the embodiment of the present utility model also proposes an electromagnetic heating system, which includes the above-mentioned current detection and protection control device of the electromagnetic heating system.

The electromagnetic heating system can minimize the IGBT damage caused by the cumulative effect through the current detection and protection control device of the electromagnetic heating system, and has the advantages of simple structure, high reliability, and low cost.

Fig. 6 is a flow chart of the current detection and protection control method of the electromagnetic heating system according to the embodiment of the present invention, wherein the electromagnetic heating system includes a resonant circuit composed of IGBTs, and converts AC mains power into a first direct current to supply the resonant circuit The first rectification circuit and the driving circuit for driving the IGBT. As shown in Figure 6, the current detection and protection control method of the electromagnetic heating system includes the following steps:

S1, detect the current of IGBT.

S2, detecting the zero-crossing point of the AC mains power, and starting to obtain the maximum current in each conduction period of the IGBT at the zero-crossing point of the AC mains power. As shown in Fig. 5a, the maximum current in each conduction cycle of the IGBT starts to be obtained at the zero-crossing point of the AC mains.

S3, when the maximum current in the current conduction period of the IGBT is greater than the current protection threshold, the IGBT is controlled to be turned off by controlling the driving circuit.

According to an embodiment of the present invention, when the maximum current in the current conduction period of the IGBT is greater than the current protection threshold, a warning message is issued, and the electromagnetic heating system is controlled to shut down.

Simply put, it detects in real time whether the AC mains crosses zero, and starts to obtain the maximum current in each conduction cycle of the IGBT when the AC mains zero is detected. If the obtained maximum current in the current conduction cycle of the IGBT is greater than the current protection threshold, the IGBT is turned off by controlling the driving circuit, and a warning message is issued at the same time, and the electromagnetic heating system is controlled to shut down to stop heating, so as to overheat the electromagnetic heating system. stream protection.

According to an embodiment of the present invention, when the number of times of obtaining the maximum current is greater than the preset number of times or the time of obtaining the maximum current reaches the preset time, if the maximum current in each conduction cycle of the IGBT is less than or equal to the current protection threshold, Accumulate the maximum current obtained in each conduction cycle and take the average to obtain the average current, and calculate the power of the electromagnetic heating system according to the average current, and compare the power of the electromagnetic heating system with the target power to adjust the IGBT in the next The on-time during the on-cycle.

According to an embodiment of the present utility model, if the power of the electromagnetic heating system is greater than the target power, the on-time of the IGBT in the next conduction period is reduced by controlling the driving circuit; Drive the circuit to increase the conduction time of the IGBT during the next conduction cycle.

Preferably, the preset time is a half-wave cycle of the AC mains.

Specifically, when the zero-crossing point of the AC mains is detected, the maximum current in each conduction period of the IGBT is acquired. If the obtained maximum current in the current conduction period of the IGBT is less than or equal to the current protection threshold, record the maximum current and continue to obtain the maximum current in the next conduction period of the IGBT. When the time to obtain the maximum current is greater than the preset time such as a half-wave cycle of AC mains or the number of times to obtain the maximum current is greater than the preset number of times, calculate the average value of the maximum current within the preset time or the preset number of times, that is, the average current, And calculate the effective value of the current according to the above formula (1), and then multiply the calculated effective value of the current by the effective value of the voltage to obtain the power of the electromagnetic heating system, and compare the power of the electromagnetic heating system with the target power. If the calculated power of the electromagnetic heating system is greater than the target power, control the drive circuit to reduce the conduction time of the IGBT in the next conduction cycle; if the calculated power of the electromagnetic heating system is less than the target power, control the drive circuit to The conduction time of the IGBT in the next conduction cycle is increased, so as to realize the power regulation of the electromagnetic heating system and ensure the stable operation of the electromagnetic heating system according to the target power.

Further, the flow chart of the current detection and protection control method of the electromagnetic heating system according to an embodiment of the present invention is shown in FIG. 4 , which will not be described in detail here.

According to the current detection and protection control method of the electromagnetic heating system of the embodiment of the utility model, the current of the IGBT and the zero-crossing point of the AC mains are detected in real time, and the current in each conduction period of the IGBT is obtained at the zero-crossing of the AC mains. Maximum current, when the maximum current in the current on-cycle of the IGBT is greater than the current protection threshold, the drive circuit is controlled to control the IGBT to turn off, thereby minimizing the IGBT damage caused by the cumulative effect, and it has a simple method and high reliability. advantage.

In describing the present invention, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "Back", "Left", "Right", "Vertical", "Horizontal", "Top", "Bottom", "Inner", "Outer", "Clockwise", "Counterclockwise", "Axial" The orientation or positional relationship indicated by , "radial", "circumferential", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the utility model and simplifying the description, rather than indicating or implying the referred device Or elements must have a specific orientation, be constructed and operate in a specific orientation, and thus should not be construed as limiting the invention.

In addition, the terms "first" and "second" are used for descriptive purposes only, and cannot be interpreted as indicating or implying relative importance or implicitly specifying the quantity of indicated technical features. Thus, the features defined as "first" and "second" may explicitly or implicitly include at least one of these features. In the description of the present utility model, "plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

In this utility model, unless otherwise specified and limited, terms such as "installation", "connection", "connection" and "fixation" should be understood in a broad sense, for example, it can be a fixed connection or a detachable connection. Connected, or integrated; may be mechanically or electrically connected; may be directly connected or indirectly connected through an intermediary, and may be an internal communication between two elements or an interactive relationship between two elements, unless otherwise stated Clearly defined. Those of ordinary skill in the art can understand the specific meanings of the above terms in the present utility model according to specific situations.

In the present invention, unless otherwise clearly specified and limited, the first feature may be in direct contact with the first feature or the first feature and the second feature through an intermediary indirect contact. Moreover, "above", "above" and "above" the first feature on the second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. "Below", "beneath" and "beneath" the first feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is less horizontally than the second feature.

In the description of this specification, descriptions referring to the terms "one embodiment", "some embodiments", "example", "specific examples", or "some examples" mean that specific features described in connection with the embodiment or example , structures, materials or features are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the described specific features, structures, materials or characteristics may be combined in any suitable manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine different embodiments or examples and features of different embodiments or examples described in this specification without conflicting with each other.

Although the embodiments of the present invention have been shown and described above, it can be understood that the above-mentioned embodiments are exemplary, and should not be construed as limitations of the present invention, and those of ordinary skill in the art are within the scope of the present invention. Variations, modifications, substitutions and variations can be made to the above-described embodiments.

Claims (7)

1. A current detection and protection control device for an electromagnetic heating system, characterized in that, the electromagnetic heating system includes a resonant circuit made of IGBTs, a first DC power that converts AC mains power into a first direct current to supply the resonant circuit A rectifier circuit, a drive circuit for driving the IGBT, and the current detection and protection control device includes: a second rectification circuit that converts the AC mains power into a second DC power; A zero-crossing detection circuit, the zero-crossing detection circuit is connected to the second rectifier circuit, and the zero-crossing detection circuit detects the zero-crossing point of the AC mains according to the second direct current; A current detection circuit, the current detection circuit is connected to the E pole of the IGBT, and the current detection circuit is used to detect the current of the IGBT; A controller, the controller is respectively connected with the zero-crossing detection circuit, the current detection circuit and the driving circuit, and the controller starts to acquire The maximum current in the on-cycle, and when the maximum current in the current on-cycle of the IGBT is greater than the current protection threshold, the controller controls the drive circuit to control the IGBT to turn off. 2. The current detection and protection control device of the electromagnetic heating system as claimed in claim 1, further comprising an alarm, the alarm is connected to the controller, wherein the current conduction of the IGBT When the maximum current in a cycle is greater than the current protection threshold, the controller also controls the alarm to send out a warning message, and controls the electromagnetic heating system to shut down. 3. The current detection and protection control device of the electromagnetic heating system according to claim 1, characterized in that, when the number of times of obtaining the maximum current is greater than the preset number of times or the time for obtaining the maximum current reaches the preset time, If the maximum current in each conduction period of the IGBT is less than or equal to the current protection threshold, the controller accumulates the obtained maximum current in each conduction period and takes an average to obtain an average current, and Calculate the power of the electromagnetic heating system according to the average current, and compare the power of the electromagnetic heating system with a target power to adjust the conduction time of the IGBT in the next conduction period. 4. The current detection and protection control device of the electromagnetic heating system according to claim 3, characterized in that, If the power of the electromagnetic heating system is greater than the target power, the controller controls the driving circuit to reduce the conduction time of the IGBT in the next conduction period; If the power of the electromagnetic heating system is less than the target power, the controller controls the drive circuit to increase the conduction time of the IGBT in the next conduction period. 5 . The current detection and protection control device for an electromagnetic heating system according to claim 3 , wherein the preset time is one half-wave cycle of the AC mains. 6 . 6. The current detection and protection control device of the electromagnetic heating system according to claim 1, wherein the current detection circuit specifically comprises: A sampling resistor, one end of the sampling resistor is connected to the E pole of the IGBT, and the other end of the sampling resistor is grounded; A filter resistor, one end of the filter resistor is respectively connected to the E pole of the IGBT and one end of the sampling resistor; A filter capacitor, one end of the filter capacitor is connected to the other end of the filter resistor, the other end of the filter capacitor is grounded, and there is a first node between one end of the filter capacitor and the other end of the filter resistor, so The first node is connected to the controller. 7. An electromagnetic heating system, characterized by comprising the current detection and protection control device of the electromagnetic heating system according to any one of claims 1-6.