KR100876009B1 - Power compensation apparatus for induction heating apparatus - Google Patents

Abstract

The electric power compensation apparatus is provided to perform a constant input in the resonant cavity although a change is in the inputted AC source. The electric power compensation apparatus comprises the resonant cavity, the inverter element applying and cutting off the driving voltage to the resonant cavity, the operation unit producing the supply voltage having the size which is in inverse proportion to the size of the input power source, the digital/analog converter part applying the analog signal corresponding to the supply voltage and pulse-width modulating signal(PWM), the inverter element controller producing the control signal controlling on time of the inverter element according to the analog signal.

Description

Power compensator of induction heating equipment {POWER COMPENSATION APPARATUS FOR INDUCTION HEATING APPARATUS}

1 is a configuration diagram of an initial driving circuit of an induction heating apparatus according to the prior art.

2 is an operation graph of FIG. 1.

3 is a block diagram of an induction heating apparatus equipped with a power compensation device according to the present invention.

4 is an operation graph of FIG. 3.

The present invention relates to a power compensating device of an induction heating device, and more particularly, to a power compensating device of an induction heating device in which a predetermined value or more is output as a whole of a cooking process.

Induction heating cooker performs the cooking function by the way in which the eddy current flows when the magnetic wire generated from the working coil passes through the pot. Looking at the basic heating principle of the induction cooker, when a current is applied to the working coil, the oven is a magnetic material is heated by induction heating (heating), cooking inside the oven is made.

Therefore, in the case of an induction heating cooker, a high frequency voltage of a predetermined magnitude must be applied to the working coil in order to generate magnetic lines. At this time, the working coil has a strong thermal power of about 1300W by the applied high frequency voltage. A circuit for applying a high frequency voltage to the working coil is an inverter circuit. Conventional pulse width modulation circuit is used as a circuit for controlling the switching time for turning on or off the inverter circuit of the induction cooking cooker.

1 is a configuration diagram of an initial driving circuit of an induction heating apparatus according to the prior art.

The initial driving circuit is a non-inverting terminal is supplied with an operating signal from the microcomputer (not shown) (analog signal obtained by converting the PWM signal from the microcomputer by a digital-to-analog converter), and the commercial terminal is applied to the induction heating device as an inverting terminal. The first operational amplifier OP1 'receiving the output voltage of the input current sensing unit (not shown) sensing the input current of the power supply, and the first voltage divider R1 distributing the output of the first operational amplifier OP1'. ', R2'), a capacitor C1 'connected in parallel to the resistor R2', a second operational amplifier receiving an output voltage of an input current sensing unit as an inverting terminal and a reference potential as a non-inverting terminal ( OP2 '), and the output voltage of the second operational amplifier OP2' is applied to the base terminal, and the collector terminal is connected to the outputs of the first voltage dividers R1 'and R2', and the emitter terminal is grounded. (Q1 ') and the second field that distributes the output of the second operational amplifier OP2' The output of the first voltage divider R1 'and R2' to the voltage divider R3 'and R4' and the non-inverting terminal are output to the diode D1 'and the output of the second voltage divider R3' and R4 '. A third operational amplifier OP3 'which is applied through D2' and whose inverting terminal is fed back from the output terminal, and an IGBT driver 2 driven in accordance with the output of the third operational amplifier OP3 '.

In addition, the second operational amplifier OP2 ′ and the second voltage divider R3 ′ and R4 ′ are internal pot detection circuits 1 and output voltage V1 ′ of the second voltage divider R3 ′ and R4 ′. Corresponds to inner pot detection output.

The input current sensing unit is an element that senses an input current of a commercial AC power applied to an induction heating device and outputs a voltage corresponding thereto, and thus is not described in detail because it is only an obvious technique to those skilled in the art.

The operation of FIG. 1 is described below.

First, the operation signal is a signal obtained by converting a control signal (for example, a PWM signal) from the microcomputer by D / A conversion. In the initial state, since the input current is 0A, the output voltage of the input current sensing unit is 0V, and since the reference potential is applied to the inverting terminal of the second operational amplifier OP2 ', the output of the second operational amplifier OP2' is HIGH. It becomes a signal.

At this time, the transistor Q1 'is turned on, the output of the first operational amplifier OP1' is inhibited, and the voltage V1 'distributed by the second voltage divider R3 and R4 is the diode D2. ') Is input to the non-inverting terminal of the third operational amplifier OP3' and the inverting terminal is composed of a voltage follow circuit at the output terminal, so that the voltage V1 'is transmitted through the diode D2' to the initial operation signal Vs. ) Is applied to the IGBT driver 2. Normally, the initial operation signal Vs is set low to allow soft start.

After the initial start, when the inner pot is mounted, the output voltage of the input current sensing unit is higher than the reference potential, so that the output of the second operational amplifier OP2 'is continuously output as a HIGH signal and a LOW signal. Thus, the transistor Q1 'is turned off, and the output of the second operational amplifier OP2' is normalized. In addition, the first operational amplifier OP1 ′ outputs an operation signal and an output signal according to the output voltage of the input current sensing unit, and the output voltages V2 ′ of the first voltage dividers R1 ′ and R2 ′ are resistors R2. Has a time constant consisting of ') and a capacitor C1' and rises, and is connected to the non-inverting terminal of the third operational amplifier OP3 'through the diode D1' and reaches the normal operating voltage Vn. In this case, it operates at the control level for the IGBT driver 2.

2 is an operation graph of FIG. 1. As shown in FIG. 2, the initial starting operation is performed at the voltage V1 ', and when there is a normal load, the voltage V1' becomes 0V and operates according to the magnitude of the voltage V2 '. At this time, as shown in FIG. 2, the transient period t1 ′ is present during the period in which the voltage applied to the IGBT driver 2 is transferred from the voltage Vs to the voltage Vn. In this transient region, the operation of the IGBT drive unit 2 is unstable and there is an area where noise or power consumption is unstable, and thus there is a problem in the reliability, and stability in low power output such as fluctuations in power consumption and thermal insulation, etc. are considered. There is a problem.

It is an object of the present invention to provide a power compensation device of an induction heating apparatus such that a constant output is made in a resonator even if there is a change in an input AC power.

In the present invention, when the power consumption is high in the cooking process, the output compensation is made so that a constant power consumption is caused by the compensation according to the variation of the commercial AC power, and when the power consumption is low, the constant regardless of the variation of the commercial AC power supply. It is an object of the present invention to provide a power compensation device of an induction heating device such that power consumption is caused.

It is also an object of the present invention to provide a power compensation device of an induction heating apparatus such that a gradual increase of the control signal is achieved without an excessive section during the initial driving of the induction heating apparatus.

The power compensation device of the induction heating apparatus of the present invention is applied to a resonator, an inverter element for applying and blocking a driving voltage to the resonator, and a supply voltage which is inversely proportional to a commercial input power, to a pulse width modulated signal (PWM). A digital / analog converter unit for generating a corresponding analog signal but applying an analog signal of a predetermined output or more, and an inverter element controller for generating a control signal for controlling an on time of the inverter element according to the analog signal.

In addition, the digital / analog converter unit preferably has a voltage divider connected to an applied power source Vcc at an output terminal of the analog signal, and an analog signal of at least the divided voltage of the applied power source Vcc is applied to the inverter element controller.

In addition, the inverter element controller preferably includes a control signal processing path for increasing a control signal applied to the inverter element without a reduction period in response to an increase in an input current applied to the induction heating device.

In addition, the inverter element control unit according to the output of the inner pot detection path for detecting the presence of the inner pot in response to the increase in the input current applied to the induction heating device, and the inner pot detection path and the control signal processing path, the control signal A control unit configured to adjust the size of the control unit or change the open state, and the control signal processing path receives an analog signal through a non-inverting terminal and receives an input current through an inverting terminal and an output of a second operation amplifier. A voltage divider consisting of a first resistor and a second resistor for distributing the capacitor, a capacitor connected in parallel to the second resistor, a non-inverting terminal connected to the second resistor, and an inverting terminal connected to the output terminal so as to output a control signal. It consists of a second operational amplifier for applying a control unit, the third resistor connected to the non-inverting terminal, the anode terminal is connected to the third resistor and the cathode terminal It is preferred to consist of a diode connected to the pot sensing path.

Hereinafter, the present invention has been described in detail based on the embodiments of the present invention and the accompanying drawings. However, the scope of the present invention is not limited by the following embodiments and drawings, and the scope of the present invention will be limited only by the contents described in the claims below.

3 is a block diagram of an induction heating apparatus equipped with a power compensation device according to the present invention.

The induction heating apparatus includes a bridge rectifier comprising diodes D1 to D4 connected to a commercial AC power supply, a voltage divider consisting of resistors R1 and R2 for dividing a voltage from the bridge rectifier, and smoothing the divided voltage. It is provided with the rectifying part which consists of capacitor C1. This rectifier receives a commercial AC power supply and converts it to a DC voltage V1. Capacitor C1 is connected to applied power supply Vcc via diode D5, the cathode terminal of diode D5 is connected to applied power supply Vcc, and the anode terminal of diode D5 is connected to capacitor C1. Connected, so that voltage V1 is not affected by the output of operational amplifier OP1. The voltage V1 changes in proportion to the variation of the commercial AC power supply.

In addition, the induction heating device receives the voltage V1 as the inverting terminal through the resistor R3, receives the first reference potential as the non-inverting terminal, and the operational amplifier connected to the inverting terminal through the output R4. A sub-amplification part consisting of OP1) is provided. The resistors R3 and R4 determine the amplification rate between the operational amplifier OP1 and the inverting terminal and the output.

The first reference potential is set equal to the voltage V1 when the total commercial AC power supply is rated. If the first reference potential is set to be equal to the voltage V1 when the commercial input voltage is the rated voltage as described above, the input of the operational amplifier OP1 becomes the same, so it is necessary to feedback the output of the operational amplifier OP1 to the input. There will be no. When the commercial AC power supply is lowered, the voltage V1 becomes lower than the first reference potential, so the output of the operational amplifier OP1 outputs a HIGH signal so that a current flows through the resistors R4, R5, R3, and R2. The same as the first reference potential. On the contrary, when the commercial AC power becomes higher than the rating, the voltage V1 becomes higher than the first reference potential, so that the output of the operational amplifier OP1 is in a LOW state, so the voltage V1 is calculated through the resistors R3 and R4. As the current flows to the output of the amplifier OP1, a current of a level such that the voltage V2 becomes equal to the voltage V1 flows.

In this case, since the same voltage is applied to the input terminal of the operational amplifier OP1, the output and the input of the operational amplifier OP1 are the same without amplification. That is, since the input of the operational amplifier OP1 is in the virtual ground state, the output voltage is changed so that the two inputs are always at the same level. That is, when the voltage V1 rises, the output voltage V3 of the operational amplifier OP1 is lowered. On the contrary, when the voltage V1 falls, the voltage V3 becomes high, and the input voltage of the operational amplifier OP1 is increased. Is constant at the first reference potential. The voltage V3 is inversely proportional to the voltage V1 proportional to the magnitude of the commercial AC power supply.

The induction heating device receives a PWM signal from a microcomputer (not shown) to the base terminal, the emitter terminal is connected to the grounded transistor Q1, and the base terminal is connected to the collector terminal of the transistor Q1, and to the emitter terminal. Transistor Q2 receiving voltage V3 as the driving voltage, resistor R5 connected to the collector terminal of transistor Q2, resistor R6 connected between resistor R5 and ground, and resistor R6 ) And a digital-to-analog converter section including a capacitor C2 connected in parallel to the C) and a resistor R7 connected between the applied power source Vcc and the capacitor C2. The resistors R6 and R7 form a voltage divider for distributing the applied power source Vcc.

Here, the PWM signal is a digital signal for controlling the output of the induction heating apparatus by the microcomputer to change the output of the digital / analog converter by changing the pulse width. The voltage V3 is a supply voltage of the digital / analog converter portion. This PWM signal is digital-to-analog converted via transistors Q1 and Q2 through resistors R5 and R6 and capacitor C2.

Since the PWM signal operates at high active, that is, when the pulse width is high, the voltage V4, which is the output of the digital / analog converter, becomes high. That is, when the commercial input voltage is low, the voltage V3 is high. When the output of the PWM signal is high, the voltage V4 which is the output of the digital / analog converter is the highest.

The voltage (V4), which is the output of the digital / analog converter, is inversely proportional to the fluctuation of the commercial AC power supply.If the output voltage (V4) of the digital / analog converter is high, the input current is controlled to be high. Output (power consumption) can be produced.

As described above, the digital / analog converter unit compensates for the fluctuations of the commercial AC power in a process requiring high output, such as a heating process or a boiling process, etc., so that the fluctuations are made constant. .

In the following, the digital / analog converter unit looks at the operation process in a process that requires a low output, such as a thermal insulation process of the cooking process.

In an induction heating apparatus, since a large amount of thermal energy is not required in the thermal insulation process, a resonator (not shown) (consisting of a coil and a resonant capacitor) is used to cause a minimum output. For the warming process, the induction heating device is provided with a heat insulation heater (not shown) for the lid portion and the side portion, the heat insulation heater is not able to compensate the output of the voltage fluctuation. If only the resonator of the induction heating device (usually the bottom of the pot) compensates for the fluctuations of the commercial AC power, the overall energy distribution is lost and the thermal insulation performance is degraded. For this reason, in the low output induction heating operation, the voltage V4 of the digital / analog converter portion needs to be constant according to the fluctuation of the commercial AC power supply.

To this end, one terminal of the resistor R7 is connected to the applied voltage Vcc (typically 12 Vdc), and the voltage is divided with the resistor R6, so that the constant divided voltage of the applied voltage Vcc to the resistors R6 and R7 is provided. By outputting (V4), the digital / analog converter section is operated without compensation in the fluctuation of the commercial AC power supply. If the high output of the microcomputer's PWM signal is long, such as in the heating or boiling process of the cooking process, it appears at the output voltage (V4) by the digital / analog converter to maintain a constant output according to the fluctuation of the commercial AC power supply. Controlled. On the other hand, when the high output time of the PWM signal is short, such as the thermal insulation process, the applied power supply Vcc, which is a constant voltage, is divided by the resistors R7 and R6 rather than the output voltage V4 of the digital / analog converter unit. The divided voltage is applied to the operational amplifier OP2.

That is, when the output is controlled by the microcomputer, when the high signal of the PWM signal controlled by the microcomputer is controlled by shortening, the divided voltage of the resistors R7 and R6 from the applied power supply Vcc is output to the digital / analog converter unit. The voltage V4 is greatly affected. Since the applied power supply (Vcc) is constant at a constant voltage, there is no big change in accordance with the change in the commercial AC power supply.

In addition, when the power consumption is high when the output is controlled by the microcomputer, the converted voltage of the digital / analog converter unit is large and the voltages of the resistors R7 and R6 distributed from the applied power source Vcc are relatively small. The voltage compensation of the digital-to-analog converter section is large due to the variation of the commercial AC power supply.

The induction heating device receives the output voltage V4 of the digital / analog converter unit as a non-inverting terminal, and outputs an input current sensing unit (not shown) that senses the input current of a commercial AC power applied to the induction heating unit as the inverting terminal. The operational amplifier OP2 receiving the voltage, the resistor R8 connected to the output voltage V5 of the operational amplifier OP2, the resistor R9 connected between the resistor R8 and ground, and the resistor R9. The capacitor C3 connected in parallel and the non-inverting terminal are connected between the resistors R8 and R9, and the inverting terminal is composed of the operational amplifier OP4 connected to the output terminal, so that the output of the operational amplifier OP4 is the IGBT. Inner pot detection path for generating inner pot detection output by consisting of a control signal processing path applied to the driver and an operational amplifier (OP3) receiving the output voltage of the input current sensing unit as a non-inverting terminal and receiving a second reference potential as the inverting terminal; Inner pot with control signal processing path In order to connect the ground path, a resistor R10 having one end connected to the non-inverting terminal of the operational amplifier OP4, an anode terminal connected to the other end of the resistor R10, and a cathode terminal being the output terminal of the operational amplifier OP3. Is connected to, according to the output of the inner pot detection path, the control unit is made of a control unit that adjusts the size or changes to the open state.

The IGBT driver receives a control signal and performs an operation of turning on or off an inverter element or a switch element (eg, an IGBT element) for applying and blocking a driving voltage to the resonator (coil and resonant capacitor). . The IGBT driver, the resonator and the switch element are merely recognized by those skilled in the art.

First, look at the operation of the inner pot detection path.

The non-inverting terminal (+) of the operational amplifier OP3 is connected to the output voltage of the input current sensing unit, and a second reference potential for detecting the presence of an inner pot is connected to the inverting terminal. In the initial state (when there is no inner pot), the output voltage of the input current sensing unit is 0V and is lower than the second reference potential, so the output of the operational amplifier OP3 is LOW. This LOW signal is generated to the inner pot sense output.

On the other hand, when there is a normal load (inner pot) and the circuit operation is normal, the output voltage of the input current sensing unit is higher than the second reference potential, so the output of the operational amplifier OP3 is changed from LOW to HIGH. This HIGH signal is generated by the inner pot detection output.

Next, the operation of the control signal processing path will be described.

In the initial state, the output voltage of the input current sensing unit becomes 0V, the output voltage V5 of the operational amplifier OP2 becomes High, and the output voltage V5 is divided by the resistors R8, R9 and R10 to calculate The non-inverting terminal (+) of the amplifier OP4 is connected to operate at the initial IGBT On-time level.

 When there is a normal load (inner pot) and the circuit operation is normal, the output of the operational amplifier OP3 is changed to the high state, and the resistor R10 is opened by the diode D6. Accordingly, the output voltage V5 of the operational amplifier OP2 is distributed only by the resistors R8 and R9 so that the voltage gradually increased by the capacitor C3 without a reduction interval is a non-inverting terminal of the operational amplifier OP4. Is applied to cause the induction heating device to operate in the normal mode from the initial mode of operation.

4 is an operation graph of FIG. 3.

The voltage Vs of the initial operation mode (voltage V5 is distributed from the resistors R8, R9 and R10, and output to the operational amplifier OP4) is a control signal applied to the IGBT driver in the initial state.

In addition, when the normal load (inner pot) and the circuit operation is normal, the voltage of the normal mode (Vn) is naturally connected to the voltage (Vs) of the initial operation mode without a reduction interval, the resistance of the resistor (R8) and capacitor (C3) Gradually increased by the time constant, noise is not generated and power consumption is stabilized. That is, the induction heating device equipped with the power compensating device according to the present invention starts from the magnitude of the voltage Vs of the initial operation mode instead of 0 V in the normal mode, thereby eliminating the overwork caused by the prior art.

The present invention of such a configuration has an effect that a constant output is made in the resonator even if there is a variation in the commercial AC power input.

In the present invention, when the power consumption is high in the cooking process, the output compensation is made so that a constant power consumption is caused by the compensation according to the variation of the commercial AC power, and when the power consumption is low, the constant regardless of the variation of the commercial AC power supply. By causing the power consumption, there is an effect that the power consumption can be used efficiently.

In addition, the present invention has the effect of increasing the gradual control signal in the initial driving of the induction heating apparatus without a transient interval, to prevent the generation of noise, and to ensure a stable power consumption.

Claims (4)

delete delete A resonator; An inverter element for applying and blocking a driving voltage to the resonator; A calculation unit for generating a supply voltage having a size inversely proportional to the size of a commercial input power source; A digital / analog converter configured to receive a supply voltage from the calculator and generate an analog signal corresponding to the supply voltage and the pulse width modulation signal PWM, and apply an analog signal having a predetermined output or more; Inverter element control unit for generating a control signal for controlling the on time of the inverter element in accordance with the analog signal, The inverter element controller includes a control signal processing path for increasing a control signal applied to the inverter element without a reduction section in response to an increase in the input current applied to the induction heating apparatus. The method of claim 3, The inverter element control unit controls the magnitude of the control signal according to the output of the inner pot detection path for detecting the presence of the inner pot in response to the increase of the input current applied to the induction heating device, and between the inner pot detection path and the control signal processing path. Power compensation device of the induction heating device, characterized in that it comprises a control unit for adjusting or changing to an open state.

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