KR100445104B1 - A resonance type inductive heating cooker using a self-excited half-bridge driver IC component - Google Patents

Abstract

In general, the termination power of the induction cooker mainly uses one-stage resonant type or two-stage half-bridge type. Especially, in the two-stage half-bridge type, the half-bridge driver integrated device is developed to simplify the circuit configuration. The abbreviation 'half-bridge element') is used. Prior to this invention, a method of constructing an induction heating cooker using a half-bridge element has been devised and already implemented by the present inventors, and the configuration is simple and has a great effect. However, since the two-seat half-bridge type induction heating cooker requires two terminal power elements, the economic efficiency is somewhat lower than that of the single-stage resonant type, especially when a large output is not required.

Although the 1-seat resonant induction heating cooker is more economical than the 2-seat half-bridge method, since the oscillation and driver parts for driving the terminal power unit are composed of discrete parts (DISCRETE), the circuit is complicated and the productivity and reliability are low. There is this. Therefore, in the present invention, by devising a configuration and a control method so that the half-bridge element can be used in a single-stage resonant induction heating cooker, a simple and economical induction heating cooker can be configured.

Description

Resonant type inductive heating cooker using a self-excited half-bridge driver IC component

The present invention relates to a resonant induction cooker using a self-developed half-bridge driver integrated device in an internal configuration of a resonant induction cooker, which is a kind of induction cooker, which is a kind of home cooking appliance.

In general, the termination power unit of the induction heating cooker generally uses one-stage resonant type or two-stage half-bridge type, and particularly in the two-stage half-bridge type, the half-bridge driver integrated device is cut out to simplify the circuit configuration. (Abbreviated 'half-bridge element') is used. Prior to the present invention, a method of constructing an induction heating cooker using a half-bridge element has been devised and already implemented by the present inventors, and the configuration is very simple, and has a great effect.

3 is a conventional configuration diagram of a half-bridge device, in which the resistor 7 and the capacitor 8 are elements for determining the oscillation frequency, and the oscillation frequency Fo is

Fo = 1 / [1.4 * resistance (7) * capacitor (8)]

Becomes Therefore, when the value of the resistor (7) is large or the value of the capacitor (8) is large, it can be seen that the oscillation frequency is lowered.In an induction heating cooker, if the oscillation frequency is decreased, the output is increased. This output is then used to control the output.

Figure 4 is a waveform obtained from the configuration of Figure 3, the output (Q) and the output (/ Q) is complementary to each other, these two waveforms are each applied to the gate of the two termination power device (IGBT), The output Q drives the lower power element IGBT, and the output / Q drives the upper power element IGBT. Such a method is referred to as a two-seat half-bridge method as described above.

In the two-stage half-bridge method, it is essential that the periods D1 and D2 of the drive waveforms (Q, / Q) are the same, but the half-bridge device has the same internal period of the output (Q, / Q) waveform. Designed to be the same, it can be said to be very suitable for driving two-seat half-bridge power devices.

However, the two-seat half-bridge type induction heating cooker has a feature that the configuration becomes very simple by applying the half-bridge element, but, as described above, it requires two termination power elements (IGBTs). Unless high power output (generally 1,500W or more) is required, it is somewhat less economical than the one-seat resonant type.

On the other hand, the one-stage resonant induction heating cooker is certainly more economical than the two-seat half-bridge system, but because the oscillation and driver parts for driving the termination power part are composed of discrete parts (DISCRETE), the circuit is complicated and the productivity and There is a problem of low reliability.

If the half-bridge element is applied to a one-stage resonant induction heating cooker, the above problems will naturally be solved, but the one-stage resonant induction heating device cannot be operated according to the conventional half-bridge device construction method. The (driver) drive waveforms required by the dinner resonant induction heating cooker should not have the same period (D1, D2), and duty off (in accordance with the primary resonance period of the induction heating coil 20 and the resonant capacitor 21). This is because the DUTY OFF period D2 must be able to flexibly change (interlock).

An object of the present invention is to provide a simpler, more economical and more reliable induction heating cooker by providing a configuration and a control method so that the half-bridge element can operate in a single-stage resonant induction heating cooker.

1 is a half-bridge device control circuit diagram according to the present invention,

2 is a graph illustrating an operating state of FIG. 1;

3 is a conventional half-bridge device control circuit diagram;

4 is a graph showing the operating state of FIG.

FIG. 5 is a diagram illustrating an internal configuration of a HALF-BRIDGE driver integrated device of an induction heating cooker applied to the present invention.

(Explanation of symbols for the main parts of the drawing)

3: field effect transistor (FET) 30: self-oscillating half-bridge driver

11: power element (IGBT) 15: phase comparator

20: induction heating coil 22: cooking vessel

21: resonant capacitor

1 is a half-bridge element and its circuit diagram constructed in accordance with the present invention, the operating state of which is as follows. In the field effect transistor 3, the resistance value Rds between the drain D and the source S changes as the gate G voltage is increased or decreased, and the role of the field effect transistor 3 is changed through the change of Rds. The oscillation frequency of the bridge element 30 is changed. Output control of the induction heating cooker is achieved by varying the oscillation frequency, the output is increased when the oscillation frequency is lowered, the output is decreased when the oscillation frequency is increased, which is already known in the art, detailed description thereof will be omitted.

The power supply 1 equivalently shows the gate voltage source of the field effect transistor 3, and the Rds value of the field effect transistor 3 is increased / decreased by the change of this voltage.

The resistor 2 is for limiting the gate current of the field effect transistor 3 so that the device is operated by a voltage, and the diode 4 is a field effect transistor 3 only when the RT voltage is high. By allowing the oscillation capacitor 8 to charge, the duty on cycle D1 can be determined by the value of Rds. This is to control the output of the induction heating cooker by influencing the turn-on time of the power device 11 after all.

The diode 5 is for discharging the oscillation capacitor 8 only when the RT voltage is low (LO), and the CT terminal is connected by connecting a zener diode 6 having a breakdown voltage greater than VCC / 3 in series. By preventing the voltage from dropping below VCC / 3, the output Q of the half-bridge element 30 is kept tied to the low LO state. Further understanding of this can be seen in FIG. 5. When the inverting input terminal of the comparator B, that is, the CT terminal voltage is VCC / 3 or more, the output of the comparator B is naturally low (LO), and the output ( Q) It must also be low. In this way, the state in which the output Q of the half-bridge element 30 is turned low (LO) and the power element 11 is turned off is referred to as duty off.

In order to bring the output of the half-bridge element 30 high again, the CT terminal voltage must be lowered to VCC / 3 or lower, but the total zener voltage Vth is higher than VCC / 3, so unless special measures are taken. The output will remain low, and operation will soon stop. Therefore, in order to continue the continuous operation, it is necessary to trigger the CT stage so that the CT stage voltage becomes VCC / 3 or less at every instant.

In the present invention, the phase detection waveform PH is differentially applied to the trigger capacitor 10 as a means for triggering the CT stage. That is, when the phase detection waveform PH falls low, the differential terminal pulls down the CT terminal momentarily through the trigger capacitor 10, and the RT terminal becomes high again and outputs Q. It becomes high (H), too. After that, the RT terminal voltage, which is high, becomes charged to the oscillation capacitor 8 through the Rds of the diode 4 and the field effect transistor 3, and the CT stage voltage becomes 2VCC / 3 or more again. Output Q is inverted low. This operation continues every 20-40 Khz cycles and the induction cooker is activated. 2 is a waveform diagram of the above operation, in particular, it can be seen that the differential signal is mixed in the CT stage waveform.

The resistance 9 is used to ensure that the differential signal of the trigger capacitor 10 is well transmitted to the CT terminal without being disturbed by the oscillation capacitor 8. The reason why the resistance 9 is necessary is generally an oscillation capacitor 8 This is because the capacitance of the oscillation capacitor 8 is very low as a result of the capacitance of the trigger capacitor 10 is much larger than that of the trigger capacitor 10, so as to prevent the differential signal of the trigger capacitor 10 from being ignored.

The resistor 7 is for determining the discharge time of the oscillation capacitor 8, so that the value is Rds >> resistance 7. The reason is that once the RT stage is low, the oscillation capacitor 8 is discharged as soon as possible to wait for the next trigger.

The DC power supply 12 is an equivalent representation of the rectified commercial AC power, and the capacitor 13 absorbs the smoothing of the rectified DC power and the internal switching noise, so that the internal noise is discharged to the outside through the power line. Suppress what happens.

The induction heating coil 22 is also called a work coil, and the induction electromotive force generated when the power device IGBT is turned off is received and charged / discharged by the resonant capacitor 21 connected in parallel. While drawing a trajectory like the top (resonance) waveform of FIG. The resonant side voltage reducing resistor 18 has the same value as the DC power side voltage reducing resistor 16, and the resonant side voltage divider 19 has the same value as the DC power side voltage dividing resistor 17. In the resonance section where the non-inverting input terminal (+) is higher than the inverting input terminal (-) (the sine wave locus period in the 'resonant' waveform of FIG. 2), the output PH of the phase comparator 15 becomes high (HI) and stands by. In the opposite direction (the point at which the sinusoidal waveform disappears in the 'resonant' waveform of FIG. 2), the output of the phase comparator 15 is inverted to low (LO) while being half-bridged through the trigger capacitor 10. The CT stage of the element 30 is triggered.

Then, the output Q of the half-bridge element 30 is inverted to high HI again to conduct the power element IGBT. Then, as soon as the voltage of the oscillation capacitor 8 becomes 2VCC / 3 or more, the output Q becomes LO again, and the induction heating cooker is repeated while the power element IGBT is turned off. Is working.

The invention can be variously modified and can take various forms and only the specific embodiments thereof have been described in the foregoing detailed description. It is to be understood, however, that the present invention is not limited to the specific forms mentioned in the detailed description of the invention, but rather includes all modifications, equivalents, and substitutions within the spirit and scope of the invention as defined by the appended claims. It should be understood to do.

As described in detail above, the effects obtained by the present invention are as follows. According to the conventional classical construction method, the self-excited half-bridge element has been applied only to a two-seat half-bridge induction heating cooker. However, by the novel configuration and control method proposed in the present invention, the self-excited half-bridge element is resonated. By making it possible to use a type induction heating cooker, there is an effect of realizing a simpler, more economical and more reliable resonant induction heating cooker.

Claims (4)

In a resonant induction heating cooker having an oscillation and driver portion having a self-oscillating half-bridge driver integrated element (hereinafter referred to as a "half-bridge element"), Induction heating coil for heating the cooking vessel; An power element (IGBT) connected in series with the induction heating coil to turn on or turn off the induction heating coil current; A resonant capacitor connected to the induction heating coil in parallel to receive / induce electromotive force generated when the power device is turned off; If the resonance voltage attenuation resistance is the same value as the DC power supply voltage reduction resistance and the resonance voltage divider resistance is the same value as the DC power supply voltage dividing resistance, the output is output at the resonance section where the non-inverting input terminal (+) is higher than the inverting input terminal (-). A phase comparator which triggers the CT stage of the half-bridge element through a trigger capacitor connected to the output while the output is inverted to the low LO while the PH is waited to be high (HI); A FET for changing the oscillation frequency of the half-bridge element by changing a resistance Rds value between a drain and a source; The output Q of the half-bridge element is kept low (LO) by being installed in parallel with the FET and having a breakdown voltage greater than VCC / 3 and preventing the CT stage voltage from dropping below VCC / 3. Zener diodes bound with; And In order to control the output of the induction heating cooker, it is charged through the FET only when the RT voltage is high, and the duty on period of the half-bridge element is determined by the Rds characteristic of the FET. And an oscillation capacitor for controlling the turn-on time of the power device. The Zener voltage (Vth) of claim 1, wherein the half-bridge device is configured such that when the oscillation capacitor is discharged when the RT voltage is low (LO) and the CT terminal voltage is lowered, the CT terminal voltage is not lower than VCC / 3. ) Is set larger than VCC / 3, the resonant induction heating cooker. The resonant induction heating cooker of claim 1, wherein the external trigger receives the output of the phase comparator by differentiating it through a capacitor. The resonant induction heating cooker of claim 3, wherein the phase comparator is inverted from high (HI) to low (LO) at the time when the resonant waveform disappears.