KR101240461B1 - Inverter Circuit of The Microwave Oven - Google Patents

Abstract

The present invention is a rectifier for converting a commercial AC power supply, a commercial AC power to a direct current, a reactor and a smoothing capacitor, the upper and lower IGBTs to absorb power noise generated from an inverter and smooth the rectified voltage close to DC. A resonant capacitor having a resonant capacitor in the form of a half bridge, an inverter controller for alternately outputting complementary symmetric pulses for driving the upper IGBT and the lower IGBT, and driving the IGBT to amplify the square wave voltage by amplifying the output pulses. The IGBT driver, the primary coil and the resonant capacitor are composed of a series resonant circuit to generate a resonance voltage when the square wave voltage is applied to the primary coil, and the generated electrical energy is generated through the ferrite core. High pressure transformer inducing to secondary coil, filament power coil used for heating filament of magnetron, and triple pressure The above is a multi-stage voltage rectified microwave inverter including a high voltage generator which obtains a high voltage for driving magnetron by using the multi-stage voltage rectification method. There is a benefit of being saved.

Description

Multi-stage Double-Voltage Rectified Microwave Inverter {Inverter Circuit of The Microwave Oven}

The present invention relates to a multi-stage double-voltage rectifier type microwave inverter, and more particularly, in the high voltage generator for driving the magnetron of the microwave oven inverter, the conventional electronic components that require a high cost of the product because the components are for a special high pressure The present invention relates to a multi-stage voltage rectifier type microwave inverter that seeks to significantly reduce the product cost by solving the shortcomings of the range inverter and by using the general medium and low voltage general purpose parts.

In general, the role of a microwave oven inverter (hereinafter, abbreviated as 'inverter') using a commercial AC power source is to create a high voltage (nominal voltage -4,500V) and a magnetron filament voltage (nominal voltage 3V) required to drive the magnetron. It's work. The operation principle of the magnetron is relatively simple. When the power is supplied to the filament and the high voltage is applied to the anode, the magnetron automatically oscillates and emits electromagnetic waves (nominal frequency 2.4GH). When the electromagnetic wave is irradiated to a water-containing object (cooked food), the water molecules in the food are vibrated by the electromagnetic wave, and heat is generated. A tool that allows cooking using this principle is a microwave oven.

The inverter of the conventional microwave oven, as shown in Figure 1, takes a double voltage rectification method, in which case the output Va of the high-voltage coil 43 of the high-voltage transformer 40 should be 2,250V, which is half of the anode voltage. The voltage is rectified twice to obtain a voltage of 4,500 V required to drive the magnetron 50. A detailed description of the operation is as follows.

① primarily, when the phase of Va is a side is + and b side is-;

The high voltage capacitor 21 is charged with a voltage of 2,250V while the current starting at the point a returns to the point b through the high voltage capacitor 21 via the high voltage diode 31. At this time, the voltage polarity of the high voltage capacitor 21 becomes + at the ground side.

(2) Then, when the phase of Va becomes a on the a side and the b side on the + side;

The high voltage capacitor 20 is charged with a voltage of 2,250V while the current starting at point b returns to the point a via the high voltage diode 30 through the high voltage capacitor 20. At this time, the voltage polarity of the high voltage capacitor 20 becomes b point side.

Here, since the high voltage capacitor 21 and the high voltage capacitor 20 are connected in series, the voltage between these two ends is 2,250V + 2,250V, which is a total of 4,500V, and the anode 52 and the cathode 51 of the magnetron 50 are Since the terminals of the high voltage capacitors 20 and 21 are connected to each other, the voltage charged in the high voltage capacitors 20 and 21 becomes the driving power of the magnetron.

The filament power supply coil 42 obtains a voltage of about 3 V, which is used for heating the filament 51 of the magnetron 50. For reference, the magnetron 50 corresponds to a two-pole vacuum tube, and the filament 51 also serves as the cathode 51. In the present description, reference numeral 51 is used as a filament or a cathode as necessary.

As described above, since the charging voltage applied to the high voltage capacitors 20 and 21 is 2250 V, the breakdown voltage required for these devices should be at least about 3,000 V considering the constant margin, and the reverse voltage applied to the high voltage diodes 30 and 31. Although it can be seen as 4,500V based on qualitative operation, in order to be able to withstand the reverse surge voltage generated when the magnetron starts to operate, 8KV withstand voltage is usually required. Due to the use, conventional inverters are expensive to configure.

In addition, the high voltage transformer 50 also has a high output Va of the high pressure coil 43, and thus a high cost for maintaining insulation between the primary and secondary parts is required.

In this way, the high voltage transformer, the high voltage rectifier diode, and the high voltage capacitor are the three major components constituting the inverter. Since the voltage to be handled is high voltage, the rating of these components used in the conventional inverter is treated as a special class. Special-grade parts mean that they are replaced with general-purpose parts, and the price varies from several times to several tens of times higher than general-purpose parts, which is a great obstacle to the spread of inverter-type microwave ovens.

The present invention was developed to solve the above problems, and solves the disadvantages of the conventional microwave inverter, which takes a lot of product cost because the components are for a special high-pressure high-pressure, even using a general low-pressure general-purpose parts The purpose of the present invention is to provide a multi-stage double-voltage rectified microwave inverter that is intended to significantly reduce the product cost.

Multi-stage double-voltage rectifier type microwave inverter according to the present invention for achieving the above object,

Commercial AC power supply, rectifier converting commercial AC power to DC, reactor and smoothing capacitor which absorbs power noise generated from inverter and smoothes rectified voltage close to DC, upper and lower IGBT and resonant capacitor A resonator configured in the form of a half bridge, an INVERTER control unit for alternately outputting complementary symmetric pulses for driving the upper IGBT and the lower IGBT, and driving the IGBT after amplifying the output pulse to obtain a square wave voltage IGBT DRIVER, the primary coil and the resonant capacitor is composed of a series resonant circuit to generate a resonant voltage when the square wave voltage is applied to the primary coil, the electrical energy generated according to the secondary coil through the ferrite core High-pressure transformer induction to the filament, filament power coil used for heating the filament of the magnetron, and multi-stage over 3 times It characterized in that it comprises a high voltage generating unit for obtaining a high voltage for magnetron driving using a double voltage rectification formula.

Preferably, the high voltage generator is a multi-stage connection between the charge and discharge capacitor and the diode, characterized in that the magnetron driving high voltage is obtained from an even-numbered capacitor.

The effect obtained by this invention is as follows.

Conventional inverter is composed of a double voltage rectification method, the high voltage resistance of the high voltage transformer, high voltage rectifier diode, high voltage capacitor, which are the three major components constituting the inverter is very high, the multi-stage double voltage according to the present invention Rectifier inverters can be configured with relatively low withstand voltage components, which has the advantage of greatly reducing the cost of construction.

In the multi-stage double-voltage rectifier inverter according to the present invention, since the number of components is increased so that the voltage across each element is dispersed to a low value, it is necessary to increase the number of elements, but these elements are special. It is very inexpensive compared to the high voltage components, so even if the number of components increases, the overall component cost is still greatly reduced.

1 is a circuit diagram of a conventional microwave inverter
2 is a circuit diagram of a multi-stage double-voltage voltage rectified microwave inverter according to the present invention.

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

It is to be understood, however, that the embodiments described below are only for explanation of the embodiments of the present invention so that those skilled in the art can easily carry out the invention, It does not mean anything.

In order to clearly illustrate the present invention, portions which are not related to the description have been omitted, and like reference numerals have been assigned to similar portions throughout the specification.

Throughout the specification and claims, when a section includes a constituent, it is intended that the inclusion of the other constituent (s) does not exclude other elements unless specifically stated otherwise.

Prior to the description, the numerical values (particularly voltage values) presented below will be referred to as nominal values for objectivity of understanding, and the device and the loss between the device and the device are regarded as zero. In the case of the magnetron, the driving anode voltage varies greatly depending on the body temperature of the magnetron.For example, even if the nominal driving voltage is -4,500V, the driving voltage decreases to around -4,000V even when the magnetron is very hot. It is intended to be expressed as a nominal value.

Conventional inverter adopts double voltage rectification method. In this case, the secondary voltage of high voltage transformer is 2250V which is half of the anode voltage, the reverse voltage applied to the high voltage rectifier diode is 4,500V, and the voltage applied to the high voltage rectifier capacitor is 2,250V. to be. As the voltage applied to the three major components of the inverter exceeds 2,000V and reaches 4,500V, the high voltage transformer should pay close attention to the insulation of the secondary coil, and the high voltage rectifier diode and the high voltage rectifier capacitor are specially rated devices. It should consist of

On the other hand, the present invention introduces a multi-stage voltage rectification formula into the high voltage generation unit so as to disperse the voltage applied to each element so that a general general purpose component can be used, thereby achieving the same effect at a low cost. In the present invention, a 6 times voltage rectification method is used. Compared with the conventional inverter, the secondary voltage of the high voltage transformer is 750 V, which is 1/6 of the anode voltage, and the voltage applied to the high voltage rectifying diode and the high voltage rectifying capacitor is secondary. It's only 1,500V, twice the voltage.

As described above, it can be seen that the reverse voltage applied to the critical element according to the configuration of the present invention is significantly lower than that of the conventional inverter, so that a general purpose general component may be used.

2 is a circuit diagram of a multi-stage double-voltage voltage rectified microwave inverter according to the present invention.

As shown in FIG. 2, the inverter includes a commercial AC power supply 10, a rectifier 11, a reactor 12, a smoothing capacitor 13, an IGBT 16, 17, and a resonant capacitor 14, 15. The structure includes a resonator, an inverter controller 19, an IGBT driver 18, a high voltage transformer 40, a filament power supply coil 42, and a high voltage generator configured in the form of a bridge.

That is, the reactor AC having a role of absorbing power noise generated in the inverter, the rectifier 11 converting the commercial AC power source 10, the commercial AC power source 10 into DC, and smoothing the rectified voltage close to DC ( 12) and the smoothing capacitor 13, the IGBT (16, 17) and the resonant capacitor (14, 15) is formed in the half bridge (HALF BRIDGE) resonator, driving the upper IGBT 16 and the lower IGBT (17) Inverter control unit 19 for alternately outputting complementary symmetrical pulses for driving, IGBT driver 18 for driving square wave voltage Vb by driving IGBTs 16 and 17 after current amplifying the output pulses, primary coil 41 ) And the resonant capacitor (14, 15) is composed of a series resonant circuit, when the square wave voltage Vb is applied to the primary coil 41 generates a resonance voltage Vp and the generated electrical energy is the ferrite core 44 To heat the filament 51 of the high-voltage transformer 40, the magnetron 50 to be induced in the secondary coil 45 through the The filament power supply coil 42 used for one purpose, and a high voltage generating unit for obtaining a high voltage for magnetron driving by using a multi-stage double voltage rectification formula of three times or more.

Here, the commercial AC power source 10 is used as a home power source according to the country of 100V ~ 240V, respectively. The rectifier 11 converts the commercial AC power supply 10 into a direct current, and the reactor 12 and the smoothing capacitor 13 absorb the power noise generated in the inverter and smooth the rectified voltage close to the direct current. . The IGBTs 16 and 17 and the resonant capacitors 14 and 15 are configured in the form of a typical half bridge.

The inverter control unit 19 alternately outputs the complementary symmetric pulses for driving the upper IGBT 16 and the lower IGBT 17, and the IGBT driver 18 drives the IGBTs 16 and 17 after amplifying the currents. The square wave output Vb is obtained. Vb becomes HIGH (+) when the upper IGBT 16 is conductive, and Vb becomes LOW (0) when the lower IGBT 17 is conductive.

The primary coil 41 and the resonant capacitors 14 and 15 of the high voltage transformer 40 constitute a series resonant circuit. When the square wave voltage Vb is applied to the primary coil 41, a resonance voltage Vp is generated. The generated electrical energy is induced in the secondary coil 45 through the ferrite core 44. The secondary coil 45 has a larger number of turns than the primary coil 41 to obtain a high voltage, and the filament power coil 42 generally winds only 1 or 2 turns to obtain a voltage of approximately 3V.

Hereinafter, the operation of the high voltage generator of the inverter according to the present invention in more detail.

Inverter according to the present invention uses a multi-stage double voltage rectification formula, the rectifier stage to be introduced here is 6 times the pressure. In this case, the output Ve of the secondary coil 45 of the high voltage transformer 40 is sufficient as 750 V, which is 1/6 of the anode voltage, and is rectified 6 times to obtain a voltage of 4,500 V required to drive the magnetron 50. , Operation details are as follows.

When the polarity of the point e of the output voltage Ve becomes + when viewed from the ground m point of the secondary coil 45 as a reference, the diode 32 conducts and the terminal voltage of the capacitor 22 is charged to Ve. Next, when the polarity of Ve is reversed and the point e becomes-, the voltage of the capacitor 22 is added to the Ve voltage, and the capacitor 23 is charged through the diode 33.

At this time, the terminal voltage of the capacitor 23 is 2 · Ve. When the polarity of Ve is reversed again and the point e becomes +, the capacitor 23 voltage 2 Ve is added to the Ve to charge the capacitor 24 via the diode 34. However, at this time, since the terminal voltage of the capacitor 23 is applied to the capacitor 22, the terminal voltage does not become 3 · Ve but becomes 2 · Ve as the capacitor 23. If such operation is continued, all of the capacitors 23, 25, and 27 except the capacitors 22, 24, and 26 are charged with 2 Ve. Therefore, a voltage of 6 · Ve is generated at the point k of the last capacitor 27.

That is, an odd multiple of voltages are obtained in the capacitors 22, 24, and 26, and an even multiple voltages are obtained in the capacitors 23, 25, and 27. The power supplied to the load (magnetron current) is an even multiple of the capacitor. Supplied from (23,25,27). The odd-numbered capacitors 22, 24, and 26 are provided with a large amount of ripple voltage in relation to supplying a charging current to the odd-numbered capacitors in the next stage, so that the use of them as a load current source is excluded.

As described above, in the multi-stage voltage rectification type, the sum of voltages of each stage becomes a final output voltage, so that the breakdown voltage of each diode and capacitor may be 2 times the output voltage Ve of the secondary coil, that is, 1,500 V. Therefore, when the high voltage is obtained by the double voltage method used in the conventional inverter, there is an advantage that is very advantageous in selecting the parts, and thus the configuration cost is low.

Description of the Related Art [0002]
10: commercial AC power source 11: rectifier
12: reactor 13: smoothing capacitor
16, 17: IGBT 14, 15: resonant capacitor
19: INVERTER control unit 18: IGBT driver
40: high voltage transformer 42: filament power coil

Claims (2)

Commercial AC power supply;
A rectifier for converting a commercial alternating current into a direct current;
A reactor and a smoothing capacitor for absorbing power noise generated in an inverter and for smoothing a rectified voltage close to a direct current;
A resonator including upper and lower IGBTs and a resonant capacitor having a half bridge shape;
An INVERTER control unit for alternately outputting complementary symmetric pulses for driving the upper IGBT and the lower IGBT;
An IGBT DRIVER configured to drive an IGBT after the current amplifies the output pulse to obtain a square wave voltage;
The primary coil and the resonant capacitor are composed of a series resonance circuit, and when the square wave voltage is applied to the primary coil, a resonance voltage is generated, and the generated electrical energy is induced by the ferrite core to the secondary coil. Transformer;
Filament power coil used for heating the filament of the magnetron; And
Including a high voltage generating unit for obtaining a high voltage for driving magnetron by using a multi-stage double voltage rectification formula of 3 times or more,
The high voltage generator
A multi-stage double-voltage rectifier-type microwave inverter, wherein the charge-discharge capacitor and the diode are connected in multiple stages, and the magnetron driving high voltage is obtained from an even-numbered capacitor.
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