KR20030096999A - A inverter circuit of inverter microwave oven - Google Patents

Abstract

PURPOSE: An inverter circuit is provided to simplify the configuration of circuit and reduce manufacturing costs by reducing the count of parts constituting the driver circuit. CONSTITUTION: An inverter circuit comprises a main switching element which operates to drive a magnetron; a resonant circuit for generating a resonant voltage in accordance with the switching operation of the main switching element; a comparing unit for outputting a high signal when the resonant voltage of the resonant circuit is higher than a predetermined level; and a clamp switching element for protecting the main switching element in accordance with the output of the high signal of the comparing unit. The main switching element has an emitter potential same as the emitter potential of the clamp switching element.

Description

A inverter circuit of inverter microwave oven

The present invention relates to an inverter microwave oven, and more particularly, to an inverter circuit of an inverter microwave oven which matches the emitter potential of the main switching element and the emitter potential of the clamp switching element and controls the clamp switch to operate stably. .

Looking at the inverter circuit of the inverter microwave oven according to the prior art as follows.

When power is supplied to the inverter microwave oven and cooking is selected, the magnetron is driven. At this time, the operation of the inverter circuit for supplying high voltage power is required to drive the magnetron.

1 is an inverter circuit of an inverter microwave oven according to the prior art.

Looking at the connection relationship of the control configuration configured in Figure 1 applied power (Vdc) is connected to the coil (L1), the coil (L1) is connected to the collector terminal of the second IGBT driving element (Q2). The base terminal of the second IGBT driving element Q2 is connected to the IGBT driving circuit A 10.

The emitter terminal of the second IGBT driving element Q2 is connected to the second capacitor C2. A second diode D2 is connected between the collector terminal and the emitter terminal of the second IGBT driving element Q2. At this time, the anode terminal of the second diode D2 and the emitter terminal of the second IGBT driving element Q2 are connected, and the cathode terminal of the second diode D2 and the collector of the second IGBT driving element Q2. It is connected to the terminal.

Meanwhile, the coil L1 and the first capacitor C1 are connected, and the first capacitor C1 is connected to the collector terminal of the first IGBT driving element Q1. The base terminal of the first IGBT driving element Q1 is connected to the IGBT driving circuit B 20. In addition, the emitter terminal of the first IGBT driving element Q1 is grounded. A first diode D1 is connected between the collector terminal and the emitter terminal of the first IGBT driving element Q1. In this case, the collector terminal of the first IGBT driving element Q1 is connected to the cathode terminal of the first diode D1, and the emitter terminal of the first IGBT driving element Q1 is the anode of the first diode D1. It is connected to the terminal. In addition, the cathode terminal of the first diode D1 is connected to the second capacitor C2 mentioned above.

Looking at the operation control process of the drive circuit of the inverter microwave oven configured as described above are as follows.

When power is supplied and the first IGBT driving element Q1 performs the on switching operation under the control of the IGBT driving circuit B 20, energy is accumulated in the first capacitor C1 by the applied power. When the first IGBT driving element Q1 is turned off, the first capacitor C1 resonates, and a voltage is supplied to the magnetron (not shown) in this operation to drive the magnetron.

On the other hand, the resonance voltage is applied to the IGBT driving circuit A (10). Therefore, when the resonance voltage becomes higher than the prescribed value in the driving state, the IGBT driving circuit A 10 turns on the second IGBT driving element Q2. At this time, the second capacitor (C2) and the first capacitor (C1) is in a parallel state, thereby reducing the resonance voltage it is possible to protect the first IGBT driving element (Q1) that plays a switching role. Such a method is called an active clamp.

However, in order to maintain the active clamp state as described above in the inverter circuit of the inverter microwave oven according to the prior art, it was necessary to separately configure an IGBT driving circuit with a separate power source. This is because the emitter terminals of the first IGBT driving element Q1 and the second IGBT driving element Q2 are configured differently.

As a result, the circuit configuration is complicated, which reduces the reliability of the circuit operation. In addition, in the configuration of the drive circuit, by separately configuring the drive circuit of the IGBT drive element, the manufacturing cost for manufacturing the product is increased.

In addition, as the resonance voltage decreases, as the first IGBT driving element serving as the switching is turned off, the product driving is not stable.

Accordingly, an object of the present invention is to provide an inverter circuit of an inverter microwave oven in which the emitter potential of the main switching element and the emitter potential of the clamp circuit switching device are matched in the voltage resonance inverter microwave oven.

In addition, another object of the present invention is to provide an inverter circuit of an inverter microwave oven that controls the drive output to be stably increased by temporarily increasing the drive output in the transient section in which the clamp switch is conducted.

1 is an inverter circuit of the inverter microwave oven according to the prior art.

2 is an inverter circuit of the inverter microwave oven according to the present invention.

Figure 3 is an output waveform diagram output in the inverter circuit of the inverter microwave oven according to the present invention.

Explanation of symbols on the main parts of the drawings

30: differential circuit 40: comparator (OP AMP)

50: inverter driving circuit Q1: first IGBT driving element

Q2: 2nd IGBT driving element Vdc: authorized power supply

C1 ~ C4: Capacitors D1 ~ D3: Diode

R1 ~ R7: Resistor L1, L2: Coil

Inverter circuit of the inverter microwave oven according to the present invention for achieving the above object and the main switching element for switching operation for driving the magnetron; A resonance circuit for generating a resonance voltage in accordance with the switching operation of the main switching element; Comparison means for outputting a high signal when the resonant voltage of the resonant circuit is equal to or greater than a prescribed value; According to the high signal output of the comparing means, a clamp switching element is driven to protect the main switching element, and the emitter potentials of the main switching element and the clamp switching element coincide.

Hereinafter, the inverter circuit of the inverter microwave oven according to the present invention will be described.

2 is an inverter circuit of the inverter microwave oven according to the present invention.

Looking at the connection relationship of the control configuration that is configured in Figure 2 as follows.

The applied power is connected to the coil L2, and the coil L2 is connected to the collector terminal of the first IGBT driving element Q1 which is the main switch. The base terminal of the first IGBT driving element Q1 is connected to an IGBT driving circuit A 50 for driving the first IGBT driving element Q1. The emitter terminal of the first IGBT driving element Q1 is grounded. A first diode D1 is connected between the collector terminal and the emitter terminal of the first IGBT driving element Q1. In this case, the cathode terminal of the first diode D1 is connected to the collector terminal of the first IGBT driving element Q1, and the anode terminal of the first diode D1 is the emitter of the first IGBT driving element Q1. It is connected to the terminal. In addition, a first capacitor C1 connected in parallel with the first IGBT driving element Q1 is provided.

In addition, the first capacitor C1 is connected in parallel with the second capacitor C2, and the second capacitor C2 is connected in series with the second IGBT driving element Q2. That is, the second capacitor C2 is connected to the collector terminal of the second IGBT driving element Q2, and the base terminal of the second IGBT driving element Q2 is connected to the seventh resistor R7. The emitter terminal of the second IGBT driving element Q2 is connected to the negative terminal of the applied power supply Vdc. A second diode D2 is provided between the collector terminal and the emitter terminal of the second IGBT driving element Q2. That is, the cathode terminal of the second diode D2 is connected to the collector terminal of the second IGBT driving circuit Q2, and the anode terminal of the second diode D2 is the emitter terminal of the second IGBT driving element Q2. Connected with

Meanwhile, the above-mentioned coil L2 and the zener diode ZD are connected, the zener diode ZD is connected with a first resistor R1, and the first resistor R1 is a second resistor R2. ) Is connected in series. The divided voltage between the first resistor R1 and the second resistor R2 is connected to the non-inverting terminal + of the OP AMP 40.

In addition, the second resistor R2 is connected to the third diode D3 and the third capacitor C3 connected in series. The third resistor R3 and the fourth resistor R4 are connected in series. In this case, the second diode D2 and the third capacitor C3 are connected in parallel with the third resistor R3 and the fourth resistor R4. 18V is applied to the anode terminal third resistor R3 of the third diode D3. The divided voltage between the third resistor R3 and the fourth resistor R4 is connected to the inverting terminal (−) of the OP AMP 40.

In addition, between the output terminal of the OP AMP 40 and the non-inverting terminal (+), the fourth capacitor C4 and the fifth resistor R5 connected in series form a differential circuit 30. In addition, an output terminal of the OP AMP 40 is connected to a sixth resistor R6, and the sixth resistor R6 is input to the base terminal of the second IGBT driving element Q2.

Looking at the operation control of the inverter circuit of the inverter microwave oven according to the invention connected as described above are as follows.

As shown in the figure, the first capacitor C1 and the main switch for generating the magnetron driving voltage in the voltage resonant inverter, that is, the first IGBT driving element Q1, are configured in parallel. In addition, the second capacitor C2 and the second IGBT driving element Q2 are configured in series to form a clamp circuit that protects the switching element (first IGBT driving element) by lowering the rise of the resonance voltage.

In addition, the second IGBT driving device Q2 is configured to further drive the differential circuit 30, which is composed of the OP AMP 40, the fourth capacitor (C4) and the fifth resistor (R5). .

In the above configuration, after the power supply Vdc is applied into the circuit, when the first IGBT driving element Q1 is turned on under the control of the IGBT driving circuit A 50, energy is accumulated in the capacitor C1. . When the first IGBT driving element Q1 is turned off, the voltage is charged in the first capacitor C1.

When the magnetron (not shown) is driven by the resonance voltage generated when the above operation is repeated, and this operation is performed for a predetermined time, and the resonance voltage applied to the first capacitor C1 is not more than the prescribed value, the OP AMP ( The resonance voltage is transmitted to the positive terminal of 40). The reference voltage input to the negative terminal of the OP AMP 40 and the power input to the non-inverting terminal (+) are compared. If the value is larger than the reference voltage, the high voltage is output through the output terminal of the OP AMP 40. Output at high voltage. The high output voltage is input to the base terminal of the second IGBT driving element Q2. As a result, the second IGBT driving element Q2 is turned on.

As the second IGBT driving element Q2 is turned on, the second capacitor C2 starts to be charged. In this case, the current charged in the second capacitor has a larger value than the amount of current charged in the first capacitor. As a result, when the resonance voltage drops, the voltage input to the non-inverting terminal (+) of the OP AMP 40 drops significantly. Therefore, it is compared with the reference voltage input to the inverting terminal (-) of the OP AMP 40. At this time, the voltage value input to the non-inverting terminal (+) is smaller than the comparison voltage value of the inverting terminal (−), and as a result, a low signal is output to the output terminal of the OP AMP 40.

The low signal output from the output terminal of the OP AMP 40 is input to the second IGBT driving element Q2. As a result, the second IGBT driving element Q2 may be turned off and the driving may be stopped. To prevent this, the differential circuit 30 is connected by connecting the fourth capacitor C4 and the fifth resistor R5 in series between the non-inverting terminal (+) of the OP AMP 40 and the output terminal of the OP AMP 40. Configure

As shown in the drawing, the voltage at the point A is controlled to be temporarily increased through the differential circuit 30 configured as described above. Accordingly, the voltage supplied to the non-inverting terminal (+) of the OP AMP 40 is compared with the comparison voltage supplied to the inverting terminal (-) to control the output of the high signal to the output terminal of the OP AMP 40. . In addition, the HIGH signal output through the output terminal is input to the base terminal of the second IGBT driving element Q2, so that the second IGBT driving element Q2 is continuously turned on. Do it. Accordingly, a transient phenomenon that may occur in the turn-on state of the second IGBT driving device Q2 may be prevented.

As described above, a zener diode ZD, a first resistor R1, and a second resistor R2 are provided to detect the resonance voltage. In addition, a differential circuit 40 including the fourth capacitor C4 and the fifth resistor R5 is configured to prevent the transient phenomenon of the second IGBT driving element Q2 and to drive the battery stably.

In addition, the third diode D3 included in the IGBT driving circuit B 60 configured to control the operation of the second switching element Q2 is a protection element, and when the applied power is 18V or more, the power supply to protect the circuit. To block. The third capacitor connected in series with the third diode D3 functions as a noise filter for removing noise input to the non-inverting terminal (+) of the OP AMP 40.

Looking at the output waveform that appears as the operation is controlled as described above are as follows.

3 is an output waveform diagram output from the inverter circuit of the inverter microwave oven according to the present invention.

Power is supplied into the circuit, and as shown in FIG. 3, the first IGBT driving element Q1, which is a main switch, is turned on and driven. And the magnetron (not shown) is driven by the operation as described above.

On the other hand, when the resonant voltages applied to the first capacitor C1 and the second capacitor C2 become more than prescribed, the voltage is input to the non-inverting terminal of the OP AMP 40 as described above. When the resonant voltage is increased by more than the specified voltage compared to the comparison voltage input to the inverting terminal (−), a high signal is output. Accordingly, after the predetermined time (a) has elapsed, the second IGBT driving element Q2 serving as the clamp switch is turned on as shown in FIG. 3.

However, at this time, after the second IGBT driving device is turned on, the first capacitor C1 and the second capacitor C2 are in a parallel resonance state, and the resonance voltage is lowered. The capacitance of the first capacitor C1 and the second capacitor C2 may be represented by C1 <C2. Accordingly, a low signal is output to the output terminal of the OP AMP 40. The low signal is input to the base terminal of the second IGBT driving element Q2, and thus a differential circuit 30 is provided to prevent the second IGBT driving element Q2 from turning off. . Accordingly, as shown in FIG. 2, the output voltage is controlled such that the voltage output from the point A increases temporarily (T). Therefore, as shown in FIG. 3, the voltage input to the non-inverting terminal (+) of the OP AMP is temporarily increased for a T time to control the second IGBT driving device Q2 to be stably driven.

As described above, the inverter circuit of the inverter microwave oven according to the present invention includes a first IGBT driving device, which is a main switch, and a second IGBT driving device, which is a clamp switch, which integrates the potentials of the two switches, and the second IGBT. When the resonance voltage according to the driving of the driving device is lowered, it is a basic technical idea to prevent the turning off and to control to drive stably.

The rights of the present invention are not limited to the embodiments described above, but are defined by the claims, and those skilled in the art can make various modifications and adaptations within the scope of the claims. It is self-evident.

Therefore, the following effects can be expected due to the present invention.

According to the present invention, the potentials of the emitter terminal of the first IGBT driving element for the main switching and the second IGBT driving element for the clamp switching are configured in the inverter circuit. As a result, the power supplied to the driving circuit is integrated without being separated.

Therefore, it is possible to simplify the configuration of the circuit by reducing the number of components constituting the drive circuit, thereby reducing the manufacturing cost of producing a product can be expected.

In addition, while the power is supplied to the inverter circuit and driven, the operation of the second IGBT driving device is stable, thereby protecting the first IGBT driving device safely. And the reliability of the product can be improved according to the stable control operation of the circuit, it is possible to maximize the satisfaction to the user using the product according to the present invention.

Claims (2)

A main switching element for switching to drive the magnetron; A resonance circuit for generating a resonance voltage in accordance with the switching operation of the main switching element; Comparison means for outputting a high signal when the resonant voltage of the resonant circuit is equal to or greater than a prescribed value; A clamp switching element driven to protect the main switching element according to the high signal output of the comparing means, And an inverter circuit for matching the emitter potentials of the main switching element and the clamp switching element. The method of claim 1, And a differential circuit for controlling a high signal to be outputted by comparing a high voltage to the comparison means when the resonant voltage drops as the clamp switching element is driven.