KR101273530B1 - Induction heating apparatus equipped with function of protecting switching device - Google Patents

Abstract

The present invention provides a heating object (eg, a heating object mounted on a working coil due to an electromagnetic induction effect due to a magnetic field caused by a resonance voltage generated in the working coil (ie, a voltage caused by an induced current) due to the resonance between the working coil and the resonance capacitor connected in parallel. It relates to a voltage resonant induction heating device for heating the cooking vessel by inducing eddy currents to the cooking vessel, more specifically, due to the characteristics of the voltage resonant type method of the input voltage to the switching element of about 3 to 4 times In order to prevent the switching element from being damaged due to high voltage, the switching coil is sensed to protect the switching element by stopping the driver (i.e., turning it off) in the case of an overvoltage, and the overvoltage section is extremely short in the resonance voltage waveform. Prevents this from being detected normally, and even if it detects it normally, Switching device protection function that protects the switching device more reliably by stopping the switching and judging (detecting) the normal voltage after an extremely short overvoltage period to prevent the switching element from immediately generating a larger resonance voltage by continuing the switching operation. The present invention relates to a voltage resonant induction heating device provided.
Voltage resonant induction heating device with a switching element protection function according to the present invention comprises a working coil; A resonance capacitor connected in parallel with the working coil; A direct current unit supplying a direct current power source to the resonant capacitor; A switching element for turning on and off to generate a resonance action between the working coil and the resonance capacitor; A driver for turning on and off the switching device; A controller for controlling the driver; A detector configured to detect an output resonance voltage of the working coil; And a protection unit protecting the switching element by stopping the driving of the driver for a predetermined time when the overvoltage is detected by the detection unit.

Description

Induction heating apparatus equipped with function of protecting switching device

The present invention provides a heating object (eg, a heating object mounted on a working coil due to an electromagnetic induction effect due to a magnetic field caused by a resonance voltage (ie, a voltage caused by an induced current) generated in the working coil by a resonance between the working coil and the resonance capacitor connected in parallel. It relates to a voltage resonant induction heating device for heating the cooking vessel by inducing eddy current to the cooking vessel,

More specifically, due to the characteristics of the voltage resonant type method, the resonant voltage generated in the working coil is detected so that the switching element is not damaged because a high voltage of 3-4 times the input commercial voltage is applied to the switching element. Stop the driver (ie off) to protect the switching device,

The overvoltage section of the resonant voltage waveform is extremely short, preventing the controller from detecting it normally, and stopping the switching of the switching element for a certain time even if it detects normally, thus determining (detecting) the normal voltage after the extremely short overvoltage section. A voltage resonant induction heating apparatus having a switching element protection function which more reliably protects the switching element by preventing the switching element from immediately generating a larger resonance voltage by continuing the switching operation.

Induction heating apparatus is a device for heating the heating object by using the skin effect of the induction current flowing in the working coil, it is a device that maximizes energy efficiency.

The induction heating apparatus is typically a one-stage voltage resonance type and a two-seat half-bridge system.

One-stage voltage resonant induction heating device is composed of one switching element to generate a resonance action on the working coil, two-stage half-bridge system is composed of two switching elements of the upper side and the lower side and alternately switching.

The single-stage voltage resonant induction heating apparatus is widely used because of its simple circuit and easy control, but the switching element is easily damaged because the switching element is subjected to a high voltage of about 3 to 4 times the input commercial voltage.

As the voltage resonant induction heating device has a problem in that a high voltage is applied to the switching element, the switching element generally uses an IGBT that is resistant to high voltage and high frequency, but the IGBT also has a limit in the breakdown voltage, which is a limit value that can withstand overvoltage. .

Therefore, there is an urgent need for a means for protecting the switching element from overvoltage.

In the prior art, however, no means for protecting the switching element from overvoltage is provided.

1 shows a voltage resonant induction heating apparatus according to the prior art shown in Patent No. 0904236. As shown in the drawing, a voltage resonant induction heating apparatus according to the prior art is shown in FIG.

The working coil 800 and the resonance condenser 810 are connected in parallel to each other to perform a resonance action.

Switching element 710 for switching on and off so that the resonance action,

Driver 700 for turning on and off the switching element,

Control unit 600 for controlling the driver by inputting the oscillation signal to the driver,

Bridge diode and coil for rectifying and smoothing the input commercial power supply (100) into DC power to supply resonant power to the resonant capacitor,

A voltage compensator 200, a current compensator 300, and a voltage current comparator 400 for detecting and comparing a voltage and a current of an input commercial power supply and transmitting them to the controller.

The controller 600 determines the on-time length of the oscillation signal according to the magnitude of the compensation signal input from the voltage current comparator 400, and detects a phase difference in the output voltage of the working coil 800 to turn on the oscillation signal. Determine.

As can be seen in FIG. 1 and the description of the prior art, the voltage resonant induction heating apparatus according to the prior art senses the voltage applied to the switching element (that is, the output resonance voltage of the working coil), and detects the switching element from the overvoltage. There is no means for protection.

In the prior art, the overvoltage applied to the switching element is not detected because it is difficult to detect an initial time point at which the overvoltage occurs at the resonance voltage.

Figure 3 illustrates the input and output waveforms of the main components in the voltage resonant induction heating apparatus according to the present invention. Referring to the above waveforms in Figure 3, the reason for not detecting the overvoltage in the prior art Is the same as

The switching element IGBT is switched on and off so that the on-time is gradually longer due to the resonant action to generate a square wave. Accordingly, the working coil outputs the resonance voltage CP2 (−) of the triangular wave whose amplitude is gradually increased. This output resonance voltage CP2 (-) is applied to the switching element.

At some point, the output resonance voltage of which amplitude increases gradually exceeds its protection voltage CP2 (+) for protecting the switching element.

However, the time over the protection voltage in the output resonance voltage waveform is extremely short, and in general, the portion where the peak value exceeds the protection voltage for the first time is less than 1us.

Therefore, it is practically impossible to detect the point of time beyond the resonance voltage beyond the protection voltage for the first time in the resonance voltage waveform.

The resonance voltage generated after the first resonant voltage exceeding the protection voltage is gradually longer than the protection voltage, so that it can be detected. The peak value exceeds the breakdown voltage at which the switching element breaks.

Therefore, the overvoltage (i.e., the peak value exceeds the protection voltage) must be detected from the resonance voltage waveform at the time of the first or at least second occurrence of the protection voltage.

However, in the prior art, it is not possible to detect the overvoltage generated in such an extremely short time, and despite the necessity, it has not been provided with a means for detecting and controlling the switching element as a result of the detection of the overvoltage.

And even if the peak value detects the resonant voltage at the initial time exceeding the protection voltage (overvoltage), the problem is that the overvoltage section is extremely short in the resonant voltage waveform, so even if it is detected as overvoltage, it is immediately detected as the normal voltage below the protection voltage. The action lasts.

In other words, although the peak value of the resonant voltage waveform may be slightly smaller than the predetermined size, the resonance action continues to increase as the peak value continues, so it is not meaningful to merely detect the overvoltage occurring at an extremely short moment, and the point of time when the overvoltage is first detected. After that, the switching element stops switching for a certain period of time to stop the resonant action for a certain time to reduce the peak value of the resonant voltage waveform and to cause the resonant action to occur again.

The present invention has been made in order to solve the problem of the voltage resonant induction heating apparatus according to the prior art as described above, when the output coil voltage of the working coil, that is, the voltage applied to the switching element is detected, and the detection result is an overvoltage The switching operation of the switching element is stopped for a predetermined time to prevent the switching element from being damaged from overvoltage.

After the first occurrence of the overvoltage, the state of the output signal for this period is maintained for a certain time to more accurately detect the fact that the overvoltage has occurred, and the stop state of the switching element is also maintained for a predetermined time for more protection of the switching element by the overvoltage. It is an object of the present invention to provide a voltage resonant induction heating apparatus having a switching element protection function.

In addition, it reduces the manufacturing cost by simplifying the circuit configuration, and the electronic devices that are adversely affected by high frequency, noise, and high temperature due to the resonance action are mounted on the control board away from the inverter board, so that the voltage resonance type can prevent more precise control and damage. Another object is to provide an induction heating apparatus.

Voltage resonance type induction heating apparatus with a switching element protection function according to the present invention for achieving the above object

Working coil;

A resonance capacitor connected in parallel with the working coil;

A direct current unit supplying a direct current power source to the resonant capacitor;

A switching element for turning on and off to generate a resonance action between the working coil and the resonance capacitor;

A driver for turning on and off the switching device;

A controller for controlling the driver;

A detector configured to detect an output resonance voltage of the working coil;

And a protection unit protecting the switching element by stopping the driving of the driver for a predetermined time when the overvoltage is detected by the detection unit.

And the sensing unit

A distribution resistor configured to divide the output resonance voltage of the working coil by voltage division;

And a second comparator configured to receive and compare an output resonance voltage and a reference voltage sensed by the distribution resistor,

The protection part

A third comparator for receiving and comparing an output signal of the sensing unit with a reference voltage, and transmitting an output signal to the driver;

The output signal of the second comparator is connected to an input line, and after the output signal corresponding to the overvoltage is input from the sensing unit, the charging voltage of the second comparator is increased (or decreased) to the third comparator. And an output holding capacitor for holding the output signal of the third comparator for a predetermined time.

And a trigger unit configured to receive an input voltage and an output voltage across the working coil, detect a phase difference, and transmit the phase difference to the controller to determine a turn-on time of the switching device.

The protection unit further includes a discharge resistor connected in parallel to the output holding capacitor to discharge a charging voltage, and a charging resistor connected in series to the output holding capacitor to supply a charging voltage.

The controller may receive an output signal of the third comparator of the protection unit, and maintain the driving stop state for a predetermined time after the driver releases the driving stop state by the protection unit.

The voltage resonant induction heating device with the switching element protection function according to the present invention having the configuration as described above can be driven for a long time and stable because the switching element is reliably protected from high voltage, and the replacement cost due to the damage of the switching element Is reduced and economical.

1 is a circuit diagram of a voltage resonance type induction heating apparatus according to the prior art.
2 is a circuit diagram of a voltage resonance type induction heating apparatus according to the present invention.
3 is an operation waveform diagram of main components in the voltage resonant induction heating apparatus according to the present invention.
4 is a circuit arrangement diagram of a control board and an inverter board according to the present invention for minimizing noise introduced into a trigger unit by a high frequency in a voltage resonant induction heating apparatus according to the present invention to ensure stable and reliable operation.
Figure 5 is a circuit layout of the control board and inverter board according to the prior art.

Hereinafter, a voltage resonant induction heating device with a switching element protection function according to the present invention will be described in more detail with reference to FIGS. 2 to 4.

As shown in FIG. 2, the voltage resonant induction heating apparatus with the switching element protection function according to the present invention includes a working coil WC, a resonant capacitor C3, a DC unit 10, a switching element Q1, a driver ( 60), a control unit 50, a sensing unit 30, and a protection unit 40 are included.

Here, the configuration of the working coil WC, the resonant capacitor C3, the DC unit 10, and the switching element Q1 is generally referred to as a voltage resonant inverter 90. That is, the working coil WC, the resonant capacitor C3, the DC unit 10, and the switching element Q1 constituting the voltage resonant inverter 90 are well known technologies. Therefore, these are briefly described.

First, the DC unit 10 supplies a resonance power to the resonance capacitor C3 by converting an input commercial power, that is, AC power into DC power.

The DC unit 10 is a bridge diode (BD1) for full-wave rectification of the input commercial power, smoothing capacitor (C1, C2) and inductor (L1) for smoothing and directing the rectified power through the bridge diode (BD1) It is composed of

Although not shown in the drawing, a front line of the DC unit 10 may include a line filter for removing noise from an input commercial power supply, a varistor and arrester for blocking and absorbing surges, and a fuse for blocking an overcurrent.

The working coil WC and the resonant capacitor C3 connected in parallel to each other resonate according to the switching of the switching element Q1.

In other words, the resonant capacitor C3 is charged by the resonant power input from the DC unit 10 and repeats discharging and charging according to the switching operation of the switching element Q1.

In addition, the working coil WC generates a strong magnetic field by generating counter electromotive force due to charging and discharging of the resonant capacitor C3, and an induced current (ie, a resonance voltage) is generated by the magnetic field.

The induced current generated from the working coil WC (ie, the resonance voltage) causes an eddy current to be induced in the heating object placed thereon, and the heating object, which is a resistor, is heated by the eddy current.

The switching element Q1 is switched on and off so that a resonance action occurs between the working coil WC and the resonance capacitor C3.

As described above, the switching element Q1 is preferably an IGBT resistant to high voltage and high frequency.

The switching element Q1 is driven by the driver 60 under the control of the controller 50. The switching element Q1 is switched on and off so that the on time is gradually increased while the resonance operation is continued.

At this time, in the on-off operation of the switching element Q1 controlled by the controller 50 through the driver 50, the on-time length is determined according to the magnitude of the compensation signal comparing the voltage and current of the commercial power source on the input side, The turn-on time is determined according to the phase difference of the resonance voltage generated across the working coil WC.

This will be described in more detail as follows.

First, the current transformer CT connected to the input terminal detects the current of the commercial power source input, and the input current detection circuit 80 detects the strength and phase of the current from the current input from the current transformer CT to the controller 50. send.

The input voltage detector 70 connected to the input side senses the input voltage and transmits the detected input voltage to the controller 50. The input voltage detector 70 includes rectified diodes D1 and D2 for onion rectifying the input commercial voltage, resistors R11 and R12 for voltage division of the input voltage rectified at the rectified diodes D1 and D2, and a resistor ( And a capacitor C1 that smoothes the voltage divided by R11 and R12, removes noise, and transmits the noise to the controller.

The controller 50 compares the current and voltage of the received input commercial power with each other, detects the magnitude of the compensation signal, and adjusts the on-time of switching according to the magnitude of the detected compensation signal. In other words, the larger the magnitude of the compensation signal, the longer the on-time to increase the amplitude of the resonance voltage.

Next, the trigger unit 20 receives the resonant voltages from both ends of the working coil WC, that is, the input side and the output side, and compares them to detect the phase difference between the two ends of the working coil WC and transmits them to the controller.

The controller 50 calculates and determines the turn-on time synchronized with the resonance time constant from the received phase difference signals across the working coil WC.

The control unit 50 receives temperature signals detected by two temperature sensors TH1 and TH2 that are disposed on the center side and the side of the working coil WC, respectively, to sense the generated heat, and according to the transmitted temperature. The driver 60 is controlled to control on / off switching of the switching element Q1 so as not to overheat. The switching element Q1 is damaged not only when the rated voltage between the collector and the emitter exceeds the rated current of the collector, but also when the operating temperature exceeds the rated temperature. Therefore, temperature sensors TH1 and TH2 are provided to protect against temperature.

In addition, the control unit 50 is connected to a plurality of input keys for receiving a user's operation signal, and a display unit for indicating the operation state.

As described above, the trigger unit 20 receives a resonance voltage at both ends of the working coil WC, detects a phase difference therefrom, and determines a turn-on time of the switching element Q1.

The trigger unit 20 includes resistors R1, R2, R3, and R4 for voltage-dividing voltages across the working coils WC, and capacitors C4 and C5 for smoothing voltages across the voltage-divided ends, respectively. And a first comparator CP1 for detecting the phase difference by comparing the voltages of both ends of the smoothed terminal with the inverting (-) terminal and the non-inverting (+) terminal, and transmitting them to the controller 50.

For reference, the output forms of the first comparator CP1 and the second comparator CP2 and the third comparator CP3 to be described below will be described with reference to the open collector. That is, it is an open form at the main output Hi. Of course, an open-drain comparator with a main output low in the open form is also available.

In addition, the signals input to the inverting (-) terminal and the non-inverting (+) terminal of the first, second and third comparators CP1, 2 and 3 may be inputted to the opposite terminals, and these (CP1) Hi and Low, the output signals of (2,3), can also be reversed. Of course, at this time, it is necessary to set the relationship between the signal input to the inverted, non-inverted terminal and the output signal output to the output terminal.

The sensing unit 30 senses an output resonance voltage of the working coil WC (that is, a voltage at the point B in the drawing, the collector terminal voltage of the switching element Q1), and determines whether the resonance voltage peak value has exceeded the overvoltage. To judge.

The sensing unit 30 inverts the resistors R5 and R6 for voltage-dividing the voltage (point B) applied to the collector terminal of the IGBT, which is the switching element Q1, and the voltage divided by the resistors R5 and R6. A second comparator CP2 is input to the terminal (-), and the reference voltage, which determines whether or not an overvoltage, is input to the non-inverting terminal (+) and compared.

The second comparator CP2 has a reference voltage of a reference level (reference 1) input to the non-inverting terminal (+) when the collector terminal voltage of the switching element Q1 input to the inverting terminal (−) is normal. If smaller, the output is Open (ie Hi).

However, as shown in FIG. 3, in the resonance voltage at which the peak value first exceeds the reference voltage, the time in the section exceeding the reference voltage (ie, overvoltage) is extremely short.

In other words, as shown in FIG. 3, the time when the second comparator CP2 detects the overvoltage, that is, when the resonance voltage is shorted beyond the overvoltage in the open state, and then the resonance voltage falls below the overvoltage and is opened (that is, , When the second comparator determines that the output signal is low because the second comparator determines that the overvoltage is low. Even if it is transmitted to the control unit as it is, the control unit 50 cannot recognize this normally and appropriate control is impossible.

Therefore, the control unit 50 needs a means for normally recognizing the overvoltage signal sensed and output by the detection unit 30, and this means is the protection unit 40.

In addition, since extremely short overvoltage periods are not normally detected, voltage resonance continues to occur, and thus switching element Q1 may be damaged. Therefore, on / off switching of switching element Q1 is performed for a predetermined time or more at the time of overvoltage occurrence. It is necessary to forcibly stop, and this protection part 40 is also in charge.

When the detector 30 detects that the overvoltage is included in the resonance voltage, the protection unit 40 stops driving of the driver 60 for a predetermined time to protect the switching element Q1 and detects the overvoltage. The control unit 50 is sufficiently aware that there is an overvoltage by continuing the output signal for a predetermined time or more and transmitting the same to the control unit 50.

The protection unit 40 receives the output signal of the second comparator CP2 of the sensing unit 30 as the non-inverting terminal (+), compares the reference voltage with the inverting terminal (-), and compares the result. The third comparator CP3 and the output signal of the second comparator CP2 and the third comparator CP3 for transmitting to the driver 60 and stopping the driving of the driver 60 at the same time as being transmitted to the controller 50. It is connected to the input line input to (CP3), that is, the non-inverting terminal (+) of the third comparator (CP3), and discharges its own charging voltage and inputs to the non-inverting terminal (+) of the third comparator (CP3) An output holding capacitor C7 for maintaining the output signal of the third comparator for a predetermined time, a discharge resistor R8 connected in parallel with the output holding capacitor C7 to discharge the charging voltage of the capacitor C7, and the output. A charge resistor (R7) connected in series with the holding capacitor (C7) to supply and charge the applied power (V +) to the capacitor (C7); The lure is.

The operation of the protection unit 40 will be described with reference to the circuit operation waveform of FIG.

First, the output of the second comparator CP2 is in a normal state until the output resonance voltage of the working coil WC (that is, the voltage between the collector emitters of the switching element Q1) exceeds the overvoltage set as the reference voltage. Thus, the non-inverting terminal (+) of the third comparator CP3 is input, and the reference voltage is input to the inverting terminal (-) of the third comparator CP3. In this case, since the inverting terminal (-) reference voltage is smaller than the input voltage of the non-inverting terminal (+), the output of the third comparator CP3 is in an open state (ie, Hi).

For reference, at this time, the non-inverting terminal (+) of the third comparator CP3 is biased by the resistors R7 and R8, and the output of the second comparator CP2 is in an open state and thus does not affect the third comparator. The non-inverting terminal (+) voltage of CP3) becomes V +.

Next, when the collector voltage (output resonance voltage) of the switching element Q1 rises and the peak value exceeds the overvoltage (that is, the reference voltage), the voltage of the inverting terminal (-) of the second comparator CP2 becomes the reference voltage ( As it becomes higher than the reference 1), the output of the second comparator CP2 is in a low state, whereby the non-inverting terminal + of the third comparator CP3 is in a low state. Then, since the voltage of the non-inverting terminal (+) is lower than the reference voltage (reference 1), the output of the third comparator CP3 is in a low state.

However, as described above, the time when the output of the second comparator CP2 is low is very short, which is less than 1 us, and immediately returns to the open state. Therefore, the third comparator CP3 must maintain the output signal Low for a predetermined time. do.

When the output of the second comparator CP2 is low, the initial condition of the output holding capacitor C7 connected in parallel with the resistor R8 connected to the third comparator CP3 non-inverting terminal (+) is 0V, and the second comparator CP2 After the output of Hi) is applied, C7 is charged through the resistor R7 in the applied power supply V +, thereby increasing the input voltage of the non-inverting terminal (+) of the third comparator (CP3).

The third comparator (until the charge voltage of the output holding capacitor C7 increases to increase the non-inverting terminal (+) potential of the third comparator CP3 to be higher than the reference voltage (reference 1) of the inverting terminal (-). The output of CP3) is kept low.

The driver receiving the output signal of the third comparator CP3 forcibly stops driving while the output is kept low, and the controller that receives the output signal of the third comparator CP3 is low for a sufficient time. Receives an output signal and accurately recognizes overvoltage.

For reference, the time at which the output holding capacitor C7 rises to reach the reference voltage, that is, the time at which the third comparator CP3 maintains the output signal in the low state is determined by the time constants of C7 and R7.

In the present invention, the applied voltage V + to the third comparator (CP3) non-inverting terminal (+) is 15V, the reference voltage is used 1 / 2V +, that is 7.5V, the resistor R8 is about twice as large as R7 , When R8 is 200kohm and R7 is 100kohm, the non-inverting terminal (+) of the third comparator (CP3) was defined as {R8 / (R7 + R8)} * V + = 10V.

In general, the induction heating device driving circuit is separated into a control board (3) for the user's operation, and an inverter board (1) for heating the working coil (WC) by the resonance action, the inverter board (1) is a working coil ( It is disposed adjacent to the WC, and the control board 3 is disposed at a position convenient to the user away from the inverter board 1 so as not to be affected by the user's operation and the working coil WC.

As shown in FIG. 5, in the prior art, most of the electronic devices, that is, the resonant capacitor C3, the trigger circuit 20, the inverter microcomb 50A, and the like are mounted on the inverter board 1, and the control board 3 is mounted. It is equipped with a control microcomputer 50B, a button and a display unit for user operation.

For reference, the inverter microcomputer 50A includes a driver 60, a current detection circuit 80, a voltage detector 70, and a part of the controller 50, and the control microcomputer 50B includes a controller ( And the remaining part of 50).

However, in the case where most electronic devices are mounted on the inverter board and above, the trigger unit 20 and the inverter microcomputer 50A are affected by the high frequency generated by the resonance action between the working coil SW and the resonance capacitor C3. As a result, the control of the induction heating apparatus is not precise, and the switching element Q1 is damaged.

In particular, noise is introduced into the trigger unit 20 due to the influence of the high frequency caused by the resonance action, and an error occurs in the turn-on time determination, and noise is also introduced into the current detection circuit 80 and the voltage detector 70 to determine the on-time. There is a high risk of errors occurring.

In addition, when such an error occurs, precise control of the induction heating apparatus becomes difficult, and the switching element may be damaged by deformation of the on / off switching signal applied to the switching element Q1.

In order to solve such a problem according to the related art, the present invention has a working coil (WC) and a resonant capacitor (C3) and a switching device for switching on and off the inverter board (1) as shown in FIG. Q1) and a DC unit 10 for converting a commercial power source into a DC power source, that is, a general voltage resonant inverter 90 is mounted.

The trigger unit 20, the driver 60, the control unit 50, the current detection circuit 80, and the voltage detection unit 70 which are affected by the resonance action of the working coil WC and the resonant capacitor C3 are controlled by a control board ( 3) was mounted.

In addition, the electronic devices mounted by moving from the inverter board 1 to the control board 3 are electrically connected to the inverter board 1 through the connectors J1 and J2 to transmit and receive electrical signals.

In this way, the electronic devices may be adversely affected by the high frequency, noise, and high temperature due to the resonance, and may be adversely affected by the control of the induction heating device. The electronic devices may be mounted on the control board 3 away from the inverter board 1, and the connector J1, By transmitting and receiving the electrical signal through J2) normally, the present invention can significantly reduce the risk of malfunction or damage.

In the above description of the present invention, a voltage resonant induction heating device having a switching device protection function of a specific circuit diagram has been described with reference to the accompanying drawings. However, the present invention can be variously modified and changed by those skilled in the art. And modifications should be construed as falling within the protection scope of the present invention.

1: Inverter Board 3: Control Board
10: DC unit 20: trigger unit
30: detection unit 40: protection unit
50: control unit 60: driver
70: voltage detector 80: current detection circuit
90: inverter
WC: Working Coil C3: Resonant Capacitor
Q1: switching element J1, J2: connector

Claims (4)

Working coil;
A resonance capacitor connected in parallel with the working coil;
A direct current unit supplying a direct current power source to the resonant capacitor;
A switching element for turning on and off to generate a resonance action between the working coil and the resonance capacitor;
A driver for turning on and off the switching device;
A controller for controlling the driver;
A detector configured to detect an output resonance voltage of the working coil;
When the detection unit detects an overvoltage, the driver is stopped for a predetermined time to protect the switching device, and the output signal that the overvoltage is detected is maintained for a predetermined time or more in order to enable the control unit to accurately recognize that there is an overvoltage. A protection unit for transmitting to the control unit;
The sensing unit includes:
A distribution resistor configured to divide the output resonance voltage of the working coil by voltage division;
And a second comparator configured to receive and compare the output resonance voltage and the reference voltage sensed by the distribution resistor,
The protection unit includes:
A third comparator for receiving and comparing an output signal of the sensing unit with a reference voltage, and transmitting an output signal to the driver;
The output signal of the second comparator is connected to an input line, and after the output signal corresponding to the overvoltage is input from the sensing unit, the charging voltage of the second comparator is increased (or decreased) to the third comparator. An output holding capacitor to maintain the output signal of the third comparator for a predetermined time;
A discharge resistor connected to the output holding capacitor in parallel to discharge the charging voltage;
A charge resistor connected in series with the output holding capacitor to supply a charge voltage;
The control unit receives the output signal of the third comparator of the protection unit, the switching element protection function, characterized in that for maintaining the driving stop state for a certain time after the driving stop state is released by the protection unit Induction heating device provided with a voltage resonance.
The method according to claim 1,
And a trigger unit configured to receive an input voltage and an output voltage at both ends of the working coil, detect a phase difference, and transmit the detected phase difference to the control unit.
The method according to claim 2,
The trigger unit includes resistors R1, R2, R3, and R4 for voltage-dividing voltages across the working coils, capacitors C4 and C5 for smoothing voltages across the voltage-divided ends, and voltages of both ends of the smoothed coil. It is configured to include a first comparator for receiving a comparison of the input to the inverting (-) terminal and the non-inverting (+) terminal to detect the phase difference and transmit it to the control unit 50,
The control unit 50 calculates and determines a turn-on time synchronized with a resonance time constant from the phase difference signals at both ends of the working coil received from the first comparator. . delete

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