KR970002787Y1 - Inverter circuit of microwave oven - Google Patents

Abstract

None.

Description

Microwave Inverter Circuit

1 is an inverter circuit diagram of the present invention.

2a, b is a circuit diagram for explaining the operating state of the inverter circuit of the present invention.

3 is an inverter circuit diagram of a conventional microwave oven.

* Explanation of symbols for main parts of the drawings

1: rectification and smoothing part 2: driving part

T1: High voltage transformer T2: Driving transformer

Q1: main switching transistor Q2: transistor

R1 to R4: Resistor ZD1, ZD2: Zener Diode

C1: condenser

The present invention relates to an inverter circuit of a microwave oven. In particular, a zener diode and a resistor are installed at one end of a driving transformer, and only the positive potential of the voltage induced on the secondary side of the driving transformer is used as a gate signal during the on time of the main switching transistor. In the off time, it relates to an inverter circuit of a microwave oven which reduces the switching loss by rapidly removing the charge accumulated in the internal capacitance between the base and the collector of the main switching transistor during the on time. The inverter circuit installed in a conventional microwave oven is composed of a bridge diode (BD), a resistor (R1), a capacitor (C1, C2) and a coil (L) as shown in FIG. 3 to rectify a predetermined AC voltage into a DC voltage. And rectifying and smoothing portion 31 for smoothing; A high voltage transformer T1 for boosting a low voltage AC voltage to a predetermined high voltage and applying the same to the magnetron; A driving transformer T2 for lowering a predetermined AC voltage to a low voltage and applying the same to each part; Large-capacity electrolytic capacitors C3 and C4 for supplying sufficient current to the base of the main switching transistor Q1, and large current transistors Q2 and Q1 for supplying current during the on time of the transistor Q1. It consisted of a field effect transistor Q3 for removing the charge accumulated in the base of the transistor Q1 during the time, and a driver 32 for driving each part by a plurality of other elements.

That is, since the input current of the microwave oven is very large, the expensive large current transistors Q2 and Q3 for driving the base of the transistor Q1 are used as the transistor Q1, which is a current driving element, as a switch for controlling the current. And because the capacitor is used, the inverter circuit of the microwave oven is complicated, there is a problem that the production cost of the product increases.

An object of the present invention is to provide an inverter circuit of a microwave oven that can reduce the number of components constituting the inverter circuit to reduce the production cost of the product and at the same time increase the reliability of the product as well as reduce the size of the circuit.

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

As shown in FIG. 1, the inverter circuit of the present invention is a drive circuit for a microwave oven including a rectifying and smoothing unit 1, a high voltage transformer T1, a driving transformer T2, a main switching transistor Q1, and a driving unit 2. In the furnace, the driving unit 2 provided between the one end of the secondary side of the driving transformer T2 and the gate of the main switching transistor Q1 is provided with a plurality of resistors R1 to R4, a capacitor C1, a Zener diode ZD1, ZD2) and transistor Q2, and apply only the power of both voltages induced on the secondary side of the drive transformer T2 as the gate bias signal during the on time of the main switching transistor Q1, and the off time of the transistor Q1. During the on-time, the charge accumulated in the internal capacitance formed between the gate and the collector of the transistor Q1 can be discharged through the transistor Q2.

Referring to the effect of the present invention configured as described with reference to (a) (b) of FIG. 2 as follows.

First, when the high signal is induced on the secondary side of the drive transformer T2 that insulates each part circuit and the main switching circuit of the microwave oven, the high signal is applied to the base of the transistor Q2 in the driver 2, so that the transistor Q2 It turns off.

Therefore, the high signal induced on the secondary side of the driving transformer T2 does not flow through the transistor Q2 as shown in FIG. 2A, but the main switching transistor Q1 through the zener diode ZD1 and the resistor R1. Since the main switching transistor Q1 is turned on because the high voltage of the predetermined voltage is induced on the secondary side of the omitted high voltage transformer T1, the magnetron is driven.

However, when the low signal induced on the secondary side of the driving transformer T2 is induced, the zener diode ZD is turned off, so that all positions corresponding to the voltage value of the zener diode ZD1 are the base and emitter of the transistor Q2. In other words, since a low signal is applied to the base of the transistor Q2, the transistor Q2 is turned on and the main switching transistor Q1 is turned off.

As described above, when the transistor Q2 is turned on, the charge accumulated in the internal capacitance between the gate and the collector of the main switching transistor Q1 (that is, the charge accumulated when the transistor Q1 is turned on) becomes zero. As shown in (b) of FIG. 2, since it is rapidly discharged through the transistor Q2, the loss when the main switching transistor Q1 is turned off can be minimized.

At this time, the zener diode ZD2 prevents the gate voltage applied to the gate of the main switching transistor Q1 from exceeding a predetermined voltage.

As described above, according to the present invention, although the inverter circuit of the microwave oven is composed of fewer parts than the conventional circuit, it is possible to reduce the loss caused when the main switching transistor is turned off, thereby reducing the production cost of the product. It is a very useful design that can improve reliability even more at the same time.

Claims (1)

In the microwave driving circuit including the rectifying and smoothing unit 1, the high voltage transformer T1, the driving transformer T2, the main switching transistor Q1, and the driving unit 2, the gate and driving of the main switching transistor Q1 are performed. The driving unit 2 provided between the secondary sides of the transformer T2 constitutes several resistors R1 to R4, a capacitor C1, zener diodes ZD1 and ZD2, and a transistor Q2 to form the driving transformer T2. Only the positive potential of the voltage induced on the secondary side of the circuit is applied as the gate signal during the on time of the main switching transistor Q1, and during the off time of the transistor Q1, the charge accumulated in the internal capacitance between the gate and the collector during the on time Inverter circuit of the microwave oven, characterized in that by-pass through the transistor (Q2).