KR100259818B1 - Switching drive circuit of induction heating cooker - Google Patents

Abstract

PURPOSE: A switching drive circuit of an induction heating cooker is provided to be capable of removing the interference noise due to the difference of operational frequency between adjacent working coils and of driving several loads using one inverter, thereby implementing a resonance type induction heating cooker having a great output. CONSTITUTION: A timer(20) generates pulses having constant width. A T flipflop(21) receives the pulse signals from the timer(20) to output one cycle for two cycles of the pulse signal. A switching period selector(22) receives the pulse signal of the T flipflop(21) and the pulse signal of the timer(20) to select a switching period. A switching driver(23) receives the switching period from the switching period selector(22) to output the switching period as a switching control signal of a switching element.

Description

Switching drive circuit of induction cooker {SWITCHING DRIVE CIRCUIT OF INDUCTION HEATING COOKER}

The present invention relates to a switching drive circuit of a resonant induction heating cooker for eliminating interference sound between burners through time-sharing control of two or more loads with one inverter, and in particular, two or more loads can be loaded with one control circuit. The present invention relates to a switching drive circuit of an induction heating cooker for controlling each switching element of a large output resonant induction cooker which can be controlled to reduce the cost and size of the entire system.

1 is a circuit diagram showing a configuration of a conventional electromagnetic induction heating cooker, and as shown therein, a power supply unit 1 for supplying AC power AC to a circuit; Rectifier (2), (3) for receiving the AC power from the power supply (1) and rectifies it; Smoothing unit (4), (5) for receiving the rectified power of the rectifier (2), (3) and smoothing it; Inverters 6 and 7 are configured to receive the smoothed power from the smoothing parts 4 and 5 and switch them to heat the container.

The inverter unit 6 includes first and second switching elements S1 and S2 for receiving a switching signal to the gate and switching the switching signal; A diode (D1), (D2) and a capacitor (C2) for protecting the first and second switching elements (S1) and (S2); It consists of a working coil Lr1 for heating a container, the inverter part 7 is also comprised like the said inverter part 6, The operation | movement of the conventional apparatus comprised in this way is as follows.

First, AC power supplied from the power supply unit 1 is rectified to DC power by passing through the rectifying unit 2. The smoothing unit 4 smoothes the rectified DC power of the rectifying unit 2 through the choke coil L1 and the condenser C1 to apply the smoothed power to the inverter unit 6.

Here, looking at the heating operation of the first working coil (Lr1) by the switching operation of the switching elements (S1, S2) First, the switching driver (not shown) is the initial high potential at the gate of the second switching element (S2) Apply a switching voltage.

Accordingly, the second switching device S2 is turned on and the rectified power applied through the rectifying unit 2 forms a loop through the first working coil Lr1 since the first switching device S1 is in an off state. The first working coil Lr1 is resonated by the loop formed as described above.

At this time, when the switching driver (not shown) applies a switching voltage to the gate of the first switching device S1, the first switching device S1 is turned on, and when the second switching device S2 is turned off, the first switching device is switched on. As the element S1 is turned on, a loop is formed through the switching element S1 in the reverse direction by the current accumulated in the first working coil Lr1 so that the current flows in the first working coil Lr1.

By repeating the switching operation as described above, the first working coil Lr1 is heated, and the first working coil is changed according to the turn-on time of the first and second switching elements S1 and S2, that is, the duty ratio. The current flowing in Lr1 is controlled.

That is, the inverters 6 and 7 heat the container by applying an eddy current to the container by repeating the above process, and each of the output power control is performed by changing the duty ratio through frequency control.

However, as described above, interference sound is generated due to a difference in operating frequency between adjacent working coils, so that accurate output control is not achieved, and the voltage is smoothed from the rectifying means and the rectifying means of the input stage as much as each configured inverter. And it is necessary to configure the filter to be filtered, which causes a complicated switching drive circuit, there is a problem that the economical lack of device configuration.

Therefore, the present invention devised in view of the above problems can eliminate the interference sound due to the difference in operating frequency between adjacent working coils, and can also drive a large output resonance with a single inverter. The purpose of the present invention is to provide a switching driving circuit of an induction heating cooker that can realize a resonant induction heating cooker having a large output by presenting a switching driving circuit capable of generating a switching pulse for each switching element of the induction heating cooker. have.

1 is a circuit diagram showing the configuration of a conventional induction heating cooker.

Figure 2 is a circuit diagram showing the configuration of the induction heating cooker switching drive circuit of the present invention.

Figure 3 is a circuit diagram showing the configuration of the induction heating cooker to which the present invention is applied.

FIG. 4 is a switching waveform diagram in FIG. 3. FIG.

Fig. 5 is a waveform diagram of each part in Fig. 2.

***** Description of the symbols for the main parts of the drawings *****

20: timer 21: tip flip flop

22: Switching cycle selector 23: Switching drive

The above object is a timer for generating a pulse having a constant width; A flip-flop unit which receives the pulse signal of the timer and outputs one cycle for two cycles of the pulse signal; A switching period selecting unit which receives a pulse signal of the flip-flop unit and a pulse signal of a timer, processes the predetermined pulse signal, and selects a switching period accordingly; This is achieved by configuring a switching driver that receives the switching period of the switching period selecting unit and outputs the switching period as a switching control signal of the switching device. The present invention will be described with reference to the accompanying drawings.

Fig. 2 is a circuit diagram showing an embodiment of the induction cooker switching drive circuit of the present invention, which includes a timer 20 for generating a pulse having a constant width as shown in the drawing; A flip-flop unit 21 which receives the pulse signal of the timer 20 and outputs one cycle for two cycles of the pulse signal; A switching period selecting unit 22 which receives the pulse signal of the tip flip-flop unit 21 and the pulse signal of the timer 20 and processes the predetermined signal to select a switching period accordingly; A switching driver 23 receives the switching period of the switching period selecting unit 22 and outputs the switching period as a switching control signal of the switching device.

The tip flip-flop unit 21 receives the pulse signal of the timer 20 and toggles when the pulse signal transitions from the low potential to the high potential and outputs the first tip flip-flop (Q) to the positive output terminal Q. TF1); The second tip flip-flop TF2 receives the signal of the first flip-flop TF1 and toggles when the pulse signal transitions from the low potential to the high potential and outputs the signal to the positive output terminal Q.

The switching period selecting unit 22 includes an oragate OR for receiving a pulse signal of the timer 20 and a pulse signal of the first tip-flop flop TF1 and calculating the same; A first AND gate AN1 receiving and performing a pulse signal of the first tip-flop TF1 and a pulse signal of a second tip-flop TF2; A first NOR gate NOR1 that receives a pulse signal of the second flip-flop TF2 and an operation signal of the OR gate OR and performs a NO operation on the pulse signal of the second flip-flop TF2; A second AND gate (AN2) for receiving and calculating the pulse signal of the second flip-flop (TF2) and the operation signal of the oragate (OR); The second AND gate AN2 receives the operation signal of the first NOR gate NOR1 and the second NOR gate NOR2.

3 is an improved inverter circuit diagram for multi-output control of an induction heating cooker to which the present invention is applied, and a filter capacitor Cf for filtering an applied DC power supply to improve an input power factor as shown in the drawing; A first switching element S11 for controlling the output of the DC power source switched and applied by the switching control signal of the switching drive circuit; A diode D11 which is anti-parallel to the first switching element S11 and protects the first switching element S11; A second switching element (S12) connected in series with said first switching element (S11) and switching operation by a switching control signal of a switching driving circuit; A diode D12 connected in anti-parallel to the second switching element S12 to protect the second switching element S12; An auxiliary resonance capacitor Ca connected in parallel with the second switching element S12; A third and fourth switching elements S13 and S14 which receive a switching control signal of the switching driving circuit and perform a switching operation according to the heating control operation of the first and second working coils Lr11 and Lr12; Protective diodes D13 and D14 connected in anti-parallel to the third and fourth switching elements S13 and S14, respectively; The first and second working coils (Lr11), (Lr12) and the resonant capacitors (Cr11), (Cr12) and the auxiliary diodes (D5), (D6), respectively, and the improved induction heating cooker The operation of the inverter circuit will be described with reference to the waveform diagram of FIG.

First, as shown in FIG. 4, in the initial state t0, the fourth switching element S14 is off, the voltage of the auxiliary resonant capacitor Ca is equal to the input voltage, and all initial values of the other resonant elements are zero.

Here, a case in which only the first working coil Lr11 is operated will be described. When the first and third switching devices S11 and S13 are turned on in the initial state t0, the first and third terminals may be input by the DC power input. The current increases linearly through the switching elements S11 and S13.

Thereafter, when the predetermined switching value is reached, when the first switching element S11 is turned off under the zero voltage condition, the loop by the input DC power is cut off, and at this time, the auxiliary resonance capacitor is caused by the current accumulated in the first working coil Lr11. Ca and the first working coil Lr11 are resonated for a very short time.

When the resonance continues as described above and the voltage of the auxiliary resonant capacitor Ca drops to zero, the current of the first working coil Lr11 is equal to the first working coil Lr11, the third switching element S13, and the auxiliary diode ( The diodes D12 may be omitted since the circuits D6) and D5 are sequentially cycled or the first working coil Lr11, the third switching element S13, and the diode D12 are sequentially cycled.

At this time, when the third switching device S13 is turned off at the time t2 and the second switching device S12 is turned on, the first working coil Lr11 and the capacitor Cr11 resonate.

Subsequently, the current of the first working coil Lr11 continues to resonate in the opposite direction, so that the voltage of the capacitor Cr11 increases again. When the voltage reaches zero again, the current of the first working coil Lr11 becomes the first working coil at time t3. Lr11, the second switching element S12, and the diode D12 are sequentially cycled again.

At this time, when the current is circulated in the path as described above, when the second switching device S12 is turned off, the auxiliary resonant capacitor Ca and the first working coil Lr11 are formed by the accumulated current of the first working coil Lr11. ) Resonates again for a very short time, and by this resonance, the voltage of the capacitor Ca becomes equal to the input DC voltage again.

The remaining current of the first working coil Lr11 flows to the input side through the diode D11 which is connected in parallel with the first switching element S11, so that the current of the first working coil Lr11 is linear. To decrease.

At this time, since the voltages of the first and third switching elements S11 and S13 are zero, the switching elements S11 and S13 are turned on again under the zero voltage condition, and thus the first working coil Lr11 is turned on. When the current drops to zero, one cycle ends, and thus, a switching operation can be implemented in the inverter circuit and the switching operation as described above.

The operation of the switching drive circuit of the present invention applied to the improved induction heating cooker inverter circuit operating as described above will be described with reference to the waveform diagram of FIG.

First, the timer 20 generates a pulse signal having a constant width as shown in FIG. 5 (a). The timer 20 may be replaced with an element that generates a controllable constant pulse, such as a voltage controlled oscillator.

The first tip flip-flop TF1 of the tip flip-flop unit 21 receives the pulse signal of the timer 20 and toggles when the pulse signal transitions from the low potential to the high potential, that is, divided into two parts (b) of FIG. Outputs a signal such as), and the second tip flip-flop TF2 of the tip flip-flop unit 21 receives the pulse signal of the first tip flip-flop TF1, and the pulse signal transitions from low potential to high potential. When toggling, that is, divides again and outputs the pulse signal as shown in Fig. 5C to the constant output terminal Q.

That is, the tip flip-flop unit 21 outputs one cycle at the output terminal with respect to two cycles of the input pulse based on the rising edge operation of the input waveform.

Thereafter, the OR gate of the switching period selecting unit 22 receives the pulse signal of the timer 20 and the pulse signal of the first tip flip-flop TF1 and calculates the same by calculating the same. The first AND gate AN1 receives the pulse signal of the first tip flip-flop TF1 and the pulse signal of the second tip flip-flop TF2, and performs an AND operation on the same. Output the same signal as (f).

In addition, the first NOR gate NOR1 of the switching period selector 22 receives an operation signal of the OR gate and a pulse signal of the second tip flip-flop TF2 and performs a NO operation on the operation signal of FIG. 5. Outputs a signal as shown in (e), and the second AND gate AN2 receives an operation signal of the OR gate and a pulse signal of the second tip flip-flop TF2, and performs an AND operation on the operation signal of FIG. 5. Outputs a signal as shown in (g), and the second NOR gate NOR2 receives the operation signal of the first NOR gate NOR1 and the operation signal of the second AND gate AN2, and performs an AND operation on the same. Output the same signal as (h).

Accordingly, the switching driver 23 outputs the operation signal output from the first AND gate AN1 of the switching period selector 22 as the switching control signal of the first switching element S11, and the second noah gate ( Outputs the operation signal output from the NOR2 as the switching control signal of the second switching element (S12), and outputs the operation signal output from the second and gate (AN2) as the switching control signal of the third switching element (S13) The soft switching operation of the inverter can be implemented according to the waveform diagram of FIG. 4.

As described in detail above, the present invention eliminates interference caused by differences in operating frequencies between adjacent working coils, and each switching element of a high-output resonant induction heating cooker capable of driving several loads with one inverter. By presenting a switching driving circuit capable of generating a switching pulse for a resonant induction heating cooker having a large output has an effect.

Claims (1)

A timer for generating a pulse having a constant width; A flip-flop unit for receiving the pulse signal of the timer and dividing the pulse signal into two and four portions; An orifice for ORing the pulse signal of the timer and the two-divided pulse signal of the flip-flop portion, the first and gate for and-operating the two-divided pulse signal and the four-divided pulse signal of the tip-flop portion, and 4 A first noble gate for performing a quinoa operation on the divided pulse signal and the output signal of the oragate, a second AND gate for performing an AND operation on the four divided pulse signal and the output signal of the oa gate, and an output signal of the second and gate And a switching period selecting unit configured to output an output signal of the first NOR gate to the NOR gate, and outputting the first, second and gate output signals as a switching period signal. And a switching driver configured to receive the switching cycle signal of the switching cycle selector and to output the switching cycle signal as a switching control signal of the switching element of the inverter circuit.

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