KR100273027B1 - Utensil Distinction and Overcurrent Protection Circuits of Induction Heating Cooker - Google Patents

Abstract

PURPOSE: A circuit in an induction heating cooker is provided to reduce the time in judging a vessel, raise correctness of judging the vessel and protect a circuit device from destruction by detecting currents of an input power and a working coil. CONSTITUTION: A rectifier(10) rectifies an input AC power into a pulsative DC power. An input filter(20) uniformly smooths or passes the pulsative power from the rectifier(10). A high-frequency inverter(30) is resonated in response to the output of the input filter(20), and supplies a high frequency current to a working coil(31) to heat a loaded vessel due to the electric induction by magnetic field. An input transformer circuit(40) detects a current of the AC power through an input transformer(41). A high-frequency transformer circuit(160) detects a current of the working coil(31) through a high-frequency transformer(161). A control circuit(150) receives a current detection value from the input transformer circuit(40) and the high-frequency transformer circuit(160) to protect a circuit from an overcurrent and judge the loaded vessel, and measures a consumed power to control the high-frequency inverter(30).

Description

Utensil Distinction and Overcurrent Protection Circuits of Induction Heating Cooker

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction heating cooker, and more particularly, to a container determination and an overcurrent protection circuit of an induction heating cooker which detects an input power supply current and a current of a working coil to determine the presence of a container, and also serves as an overcurrent protection operation. .

As shown in FIG. 1, the circuit configuration of the conventional induction heating cooker includes a rectifying unit 10 rectifying the input AC power AC to a pulsating DC power DC, and a pulsating power rectified through the rectifying unit 10. The filter to pass through in order to smoothly smooth or improve the power factor, and resonates according to the output of the input filter unit 20 to supply a high frequency current to the working coil 31 to generate electricity by a magnetic field. A high frequency inverter 30 for heating the load vessel with an induction effect, an input current transformer circuit 40 for detecting a current of the AC power source through an input transformer 41, and the input current transformer circuit 40. It is composed of a control circuit 50 for controlling the high frequency inverter 30 so that the power factor of the entire circuit is improved by receiving a current detection value of the power supply.

Referring to Figure 1 attached to the operation of the conventional induction heating cooker configured as described above are as follows.

First, the input AC power AC is rectified to the pulsating DC power DC through the rectifying unit 10 and then filtered through the input filter unit 20 formed of an inductor and a capacitor to smoothly smooth or improve the power factor. To become a pulsating voltage.

In addition, a plurality of switching elements in the high frequency inverter 30 are alternately switched according to a switching control signal output from the drive drive of the control circuit 50 so that the resonant capacitor and the working coil 31 in the high frequency inverter 30 are resonant circuits. To achieve.

Then, the high frequency current is applied to the working coil 31 according to the resonant operation of the resonant circuit, and the alternating magnetic flux is generated by the electric induction effect by the magnetic field, so that the eddy current is induced, so that the load vessel is heated.

On the other hand, the input current transformer circuit 40 detects the current of the AC power source (AC) input to the rectifier 10 through the input current transformer 41 and outputs it to the control circuit 50, the control circuit 50 is this The high frequency inverter 30 is controlled so that the power factor of the entire circuit is improved by measuring the power consumption of the load container based on the current detection value.

In addition, the control circuit 50 determines a predetermined container determination frequency in advance and determines the presence or absence of the load container based on the current detection value of the input power input from the input current transformer circuit 40 at this frequency. Multiple judging frequencies are selected and combined to determine the presence and capacity of the load vessel.

However, conventionally, as the load vessel is discriminated based on the measured value of the input current transformer 41, that is, only the input power current, several vessel determination frequencies (typically 25 kHz in the case of steel vessels, aluminum vessels) according to the material of the vessel. In case of, the time required for judging the container is excessively consumed because it usually needs to go through about 50㎑), and in case of going through the more accurate determination process considering the variation of input voltage and the deviation between each part, Since measurement data is required, there is a problem that the time required for judging the vessel is doubled.

Therefore, the present invention has been proposed to solve the above problems, by providing a container judgment and overcurrent protection circuit of the induction heating cooker to detect the input power current and the current of the working coil to determine the container and also to function as an overcurrent protection operation. The aim is to reduce the time spent in judging, improve the accuracy of judging, and protect the circuit from being destroyed by overcurrent.

Technical means of the present invention for achieving the above object, rectifying and smoothing the input AC power, the filter unit, a high frequency inverter for heating the working coil by switching in accordance with the output of the filter unit, detecting the input AC power supply vessel An induction heating cooker having an input current transformer for controlling determination and output: A high frequency current transformer for detecting a high frequency current applied to the working coil, a bridge diode for rectifying a secondary current of the high frequency current transformer, and a rectifying through the bridge diode. RC filter unit to smoothly smooth the pulsating power supply, a comparator for comparing and outputting the output voltage of the bridge diode and a predetermined reference voltage, a protection circuit unit for outputting an overcurrent detection signal in accordance with the output signal of the comparator to protect the circuit And switching according to the load vessel discrimination control signal of the control circuit. A high frequency current transformer circuit including a switching element for initializing an overcurrent determination by adjusting a level of a reference voltage input to the comparator; And controlling the switching of the high frequency inverter to protect the overall circuit when the current inputted to the working coil is overcurrent by receiving the signals output from the input current transformer and the high frequency current circuit unit and determining the magnetic and nonmagnetic loads. It is characterized by including a circuit.

1 is a block diagram showing a conventional induction cooker,

Figure 2 is a block diagram showing an induction heating cooker according to an embodiment of the present invention,

3 is a circuit diagram showing a high frequency current circuit of FIG.

Figure 4 is a block diagram showing an induction heating cooker according to another embodiment of the present invention,

FIG. 5 is a circuit diagram illustrating the high frequency current transformer of FIG. 4.

Explanation of symbols on the main parts of the drawings

10: rectifier 20: input filter

30: high frequency inverter 31: working coil

40: input current transformer circuit 41: input current transformer

150: control circuit 160: high frequency current transformer circuit

161: high frequency current transformer 165: bridge diode

165: RC filter unit 167: comparator

169: hardware protection unit 171: single-phase rectifier

172: voltage distribution means

Hereinafter, the present invention will be described with reference to the accompanying drawings.

2 is a block diagram of the induction heating cooker according to an embodiment of the present invention, the rectifier 10 for rectifying the AC power input AC to the pulsating DC power (DC), and the rectifier 10 The input filter unit 20 which smoothes or passes the pulsating power rectified through the constant and resonates according to the output of the input filter unit 20 to supply a high frequency current to the working coil 31 to generate electricity by a magnetic field. A high frequency inverter 30 for heating the load vessel with an induction effect, an input current transformer circuit 40 for detecting a current of the AC power source AC through the input current transformer 41, and the high frequency current transformer 161. The high frequency current transformer circuit 160 for detecting the current of the coil 31 and the current detection values of the input current circuit 40 and the high frequency current circuit 160 are input to protect the circuit from overcurrent and simultaneously determine the load vessel. In addition, by measuring the power consumption The control circuit 150 is configured to control the high frequency inverter 30 so that the power factor of the entire circuit is improved.

3 is a detailed circuit diagram illustrating the high frequency current circuit of FIG. 2, wherein the bridge diode 163 rectifies the secondary current of the high frequency current transformer 161 and the pulsating power rectified through the bridge diode 163. Outputting an overcurrent detection signal according to the RC filter unit 165 smoothing smoothly, a comparator 167 for comparing and outputting a preset reference voltage and the output voltage of the bridge diode 163, and an output signal of the comparator 167. And a hardware protection unit 169 for protecting the circuit by stopping the entire system, and a switching for controlling a reference voltage inputted to the inverting terminal (-) of the comparator 167, which is switched according to a predetermined load container discrimination control signal. The transistor Q is an element, and the control circuit 150 outputs a load container discrimination control signal and is input from the RC filter unit 165, the hardware protection unit 169, and the input current transformer circuit 40. On the basis of the signal to determine the load container and controls the high-frequency inverter 30.

The operation and effect of the induction heating cooker according to an embodiment of the present invention configured as described above will be described with reference to FIGS. 2 and 3, and the basic heating operation described above in the prior art description is omitted and overcurrent protection is performed. The operation and the operation of judging the container are as follows.

First, the input current transformer circuit 40 detects a current of the AC power source AC input to the rectifier 10 through the input current transformer 41, outputs the current to the control circuit 150, and performs a resonance operation of the high frequency inverter 30. Accordingly, the high frequency current applied to the working coil 31 is detected through the high frequency current transformer 161 and output to the comparator 167 and the RC filter unit 165 in the high frequency current circuit unit 160.

The output / input process between the high frequency current circuit unit 160 and the control circuit 150 is in a state in which the transistor Q is turned off and at the same time, the reference voltage V preset in the inverting terminal (-) of the comparator 167. _dd ) is described under an initial condition in which the inputs are distributed through the resistors R4 and R5, and when the secondary current of the high frequency current transformer 161 is rectified through the bridge diode 163, the pulsating power applied to the resistor R1 is divided into the resistors R2 and R2. It is distributed to R3 and is input to the non-inverting terminal (+) of the RC filter unit 165 and the comparator 167.

Then, the RC filter unit 165 filters the pulsating DC voltage inputted and smoothes it out, and outputs it to the control circuit 150. The comparator 167 outputs the reference voltage V _dd and the bridge diode 163. The voltage is compared and output to the hardware protection unit 169.

At this time, when the voltage of the non-inverting terminal (+) of the comparator 167 is greater than the voltage of the inverting terminal (-), the comparator 167 outputs a "high" signal, and the hardware protection unit 169 receives the signal. Outputs an overcurrent detection signal to initialize the control circuit 150 and stops the entire system to protect the circuit from overcurrent.

On the other hand, the determination of the load container is performed by the control circuit 150 receives the current detection signal from the RC filter unit 165 and the input current circuit unit 40 at a predetermined vessel determination frequency, no load and small The load determines the presence or absence of a load based on the detection information of the input current transformer 41, and the nonmagnetic container determines the presence or absence of a load based on the detection information of the high frequency current transformer 161.

In other words, if the current detection value of the input current transformer 41 is less than or equal to a predetermined set value, it is regarded as no-load and small load, and is ignored.

In addition, the control circuit 150 determines the nonmagnetic container by the current detection value of the high frequency current transformer 161 received through the RC filter unit 165. In detail, the control circuit 150 first determines the load container determining control signal. The control signal is applied as an open / close control voltage to the base terminal of the transistor Q through a resistor.

Then, the transistor Q is turned on and the reference voltage V _dd input to the inverting terminal (−) of the comparator 167 is discharged through the resistor R6 to fall to a predetermined level.

Thereafter, the high frequency current transformer 161, the bridge diode 163, the RC filter unit 165, the comparator 167, and the hardware protection unit 169 operate in the same process as the overcurrent protection operation. The circuit operates normally because the voltage of the non-inverting terminal (+) of) is smaller than that of the inverting terminal (-). However, in the case of a nonmagnetic container, the voltage of the non-inverting terminal (+) of the comparator 167 is the inverting terminal (-). Since the control circuit 150 is initialized to be greater than the voltage of, the entire system is stopped and protected.

On the other hand, the induction heating cooker according to an embodiment of the present invention is greatly reduced the time required to determine the container, but the reference voltage (V _dd ) applied to the inverting terminal (-) of the comparator 167 due to the variation of the input voltage Since high precision is required at the time of setting), the problem to be solved remains.

In order to solve such an open problem, another embodiment as shown in FIG. 4 is presented, and FIG. 5 is a detailed circuit diagram showing a high frequency current transformer circuit of FIG. 4, in contrast to the induction heating cookers shown in FIGS. 2 and 3. The output voltage of the single-phase rectifier 171 rectifying the output voltage of the filter unit 20 and the output voltage of the single-phase rectifier 171 are lowered and applied to the inverting terminal (-) of the comparator 167 as a variable reference voltage V _var . The voltage distribution means 172 is further included. Therefore, the reference voltage V _dd of the comparator shown in FIG. 3 is changed to the variable reference voltage V _var in FIG. 5.

Thus, in the induction heating cooker according to another embodiment of the present invention configured as described above, the voltage applied to the inverting terminal (-) of the comparator 167 flows in accordance with the variation of the input voltage.

That is, when the input voltage is changed, the output voltage of the input filter unit 20 is also changed, so that the output voltage of the input filter unit 20 is rectified through the single-phase rectifying unit 171 and then the voltage is lowered through the voltage distribution unit 172. This is because it is applied to the variable reference voltage V _var of the inverting terminal (-) of the comparator 167.

Therefore, high precision is not required when setting the resistors R4, R5, and R6, and even if the input voltage is changed, it does not affect the determination process of the load container through the control circuit 150.

As described above, the present invention detects the input power current and the current of the working coil to determine the existence and type of the container, and also serves as an overcurrent protection operation, thereby reducing the time required for the container determination and improving the accuracy of the container determination. Of course, there is an effect that can protect the circuit element from being destroyed from overcurrent.

Claims (2)

Induction heating with rectification and filter unit for rectifying and smoothing the input AC power, a high frequency inverter for heating the working coil by switching according to the output of the filter unit, and an input current transformer for detecting the input AC power and controlling the container determination and output. In the cooker: A high frequency current transformer for detecting a high frequency current applied to the working coil, a bridge diode for rectifying the secondary current of the high frequency current transformer, an RC filter unit for smoothing the pulsating power rectified through the bridge diode, and the output of the bridge diode. A comparator for comparing and outputting a voltage and a predetermined reference voltage, a protection circuit unit for outputting an overcurrent detection signal according to the output signal of the comparator, and protecting the circuit, and switching according to the load vessel discrimination control signal of the control circuit. A high frequency current converting circuit unit including a switching element for initializing an overcurrent determination by adjusting a level of a reference voltage input to the input; And A control circuit that determines the magnetic and nonmagnetic loads by receiving the signals output from the input current transformer and the high frequency current transformer, and controls the switching of the high frequency inverter to protect the overall circuit when the current input to the working coil is in the overcurrent state. Container determination and overcurrent protection circuit of the induction heating cooker comprising a. The method of claim 1, The high frequency current circuit unit, A single phase rectifier for rectifying the output voltage of the input filter unit; And And a voltage distribution means for lowering the output voltage of the single-phase rectifier to vary the reference voltage of the comparator.