KR19990058219A - Microwave malfunction prevention circuit - Google Patents

Abstract

The present invention relates to a malfunction prevention circuit of a microwave oven. In the related art, when a short occurs in a transistor stage for operating a relay for driving a high voltage transformer, the relay is operated without supplying an operation signal through a microcomputer port, thereby driving the high voltage transformer. Fire occurred or there was a problem that shorten the life of the microwave oven.

Therefore, the present invention adds the transistor TR3, the relay RY3 and the zener diode to the high voltage transformer control circuit which connects the microcomputer port PORT1 and the high voltage transformer HVT through the transistor TR1 and the relay RY1. Use two ports (PORT2, PORT3), but use the input port as the A / D port to change the voltage between the relay (RY1) and transistor (TR1) input to the A / D port2 (A / D PORT2). If the relay 1 (RY1) is not controlled and judged immediately, the relay 3 (RY3) may be turned off to prevent a malfunction that may occur due to a short at the transistor TR1 stage or a short circuit of the relay contact. .

Description

Microwave malfunction prevention circuit

The present invention relates to a malfunction prevention circuit of a microwave oven, and more specifically, to a high voltage transformer control circuit of a PCB assembly, a transistor, a relay, and a zener diode are added, and two microcomputer ports are used as A input ports. Using the / D port, the voltage change due to the short circuit of the transistor is directly judged, so that the high voltage transformer is controlled more quickly and accurately, so that a short circuit occurs in the transistor connected to the high voltage transformer control relay to prevent the risk of malfunction. It relates to a malfunction prevention circuit of.

In general, a microwave oven is a device that heats food by high frequency, and a magnetron is installed in one electric field chamber, and the high frequency generated from the magnetron is configured to be irradiated into the cooking chamber through a waveguide, and a cooking vessel is provided at the bottom of the cooking chamber. Is provided with a tray on which a tray motor capable of rotating the tray is installed at the lower part of the tray, and the cooking vessel placed thereon is rotated along the tray, so that the high frequency radiated to the cooking chamber is evenly transmitted to the food in the container. And uniformly heated.

In addition, the microwave oven is a single function microwave that defrosts or cooks food using only the high frequency oscillated from the magnetron, and a grill or oven dish in addition to the cooking due to the high frequency by installing a heater or a convection pan at the top of the cooking chamber. It is divided into multifunctional microwave oven.

On the other hand, in the microwave driving circuit, one end of the input power input through the line filter is connected to one end of the high voltage transformer through the magnetron thermostat and the primary safety switch, and the other end of the input power is the contact point of the start relay and the secondary. After the safety switch is connected to the other end of the high-voltage transformer through the contact of the output control relay.

A primary side of the low voltage transformer is connected to a rear end of the magnetron thermostat, and an output terminal of the other end of the secondary side of the low voltage transformer is connected to a power supply terminal of each part such as a controller of a control circuit board (PCB).

Cavity lamp is connected between the rear end of the magnetron thermostat and the rear end of the contact of the start relay, the tray motor and the monitor switch are connected to the rear end of the first safety switch and the second safety switch, and the fan motor is connected in parallel. One end of the heater is connected to the rear end of the primary safety switch, the other end of the heater is connected to the other end of the input power through the contact of the cavity thermostat and the heater relay, the rear end of the magnetron thermostat is one end of the convection motor The other end of the convection motor is connected to the primary side tap of the low voltage transformer through the contact of the convection motor relay.

Put the ingredients to be cooked in the cooking chamber of the microwave oven for automatic cooking using the microwave oven configured as described above, close the door, the first and second safety switches are turned on and the monitor switch is turned off, and then cooked by the normal high frequency. If you press the start button to start cooking, the start relay is turned on by the control of the controller on the control circuit board (PCB), and the output control relay is controlled on / off at the interval according to the output intensity selection by the control of the controller. The high voltage transformer is driven to drive the magnetron to perform cooking by high frequency. As the start relay is turned on, the cavity lamp, the tray motor, and the fan motor are simultaneously driven.

In the case of convection cooking, the start relay, the convection motor relay, and the heater relay are turned on to control the convection cooking. In the case of the convection cooking, the cavity lamp is turned on as the start relay and the heater relay are turned on, and the turntable motor and the fan motor are driven. In addition to this, the heater is turned on to start heating.

Subsequently, the temperature sensor detects the temperature in the cooking chamber, compares the detected temperature to a predetermined temperature or more, and then maintains the convection motor relay turned off until a constant temperature is reached.

Then, when the temperature in the cooking chamber is above a certain temperature, by turning on the convection motor relay to start the convection motor, the convection motor is turned off so as to rapidly increase the temperature in the cooking chamber at the beginning of heating. The mort is turned on to allow hot air to circulate in the cooking chamber.

In addition, the conventional convection cooking control according to the temperature sensing until the end of the cooking time, even when the convection motor is intermittently on / off to control to increase the thermal efficiency.

Thereafter, when the cooking time is over, the start relay and the heater relay are turned off, and the convection motor relay is continuously turned on.

Conventional high voltage transformers and heaters operate according to the signals of the microcomputer. When a signal is given from the microcomputer, the relay operates through the transistor. When the relay operates, the high voltage transformer and the heater connected to the relay operate.

In the driving circuit of the microwave oven controlled as described above, when a short is generated in the transistor stage for operating the relay, the relay is operated without giving an operation signal, and the high voltage transformer and the heater are operated. This may cause malfunctions.

In this case, operating in a situation where there is no signal operation causes a fire, which may shorten the life span of the microwave oven and may greatly increase consumer complaints.

Accordingly, an object of the present invention is to solve the problems described above, and add a transistor, a relay, and a resistor to a circuit component of a transistor using two microcomports, but an input port uses a A / D port to operate a relay. However, the present invention provides a malfunction prevention circuit of a microwave oven that can immediately determine when a short occurs and prevent a high voltage transformer from malfunctioning.

The object of the present invention is to connect the point A between the transistor 1 and the relay 1 connected to the microcomputer port 1 to the A / D port through the zener diode, and the port 3 to the high voltage transformer through the relay 3 and the transistor 3. After that, if a change in the voltage input to the A / D port due to the short circuit generated in the transistor 1 is determined by immediately judging the relay 3 by turning off the high-voltage transformer can be achieved.

In the present invention, when a short occurs in the transistor stage that operates the relay controlling the high voltage transformer, the A / D port immediately determines the change in the input voltage and turns off the relay 3 more quickly, thereby causing the malfunction of the high voltage transformer. By preventing a fire or shortening the life of the microwave oven can achieve the above object.

1 is a high voltage transformer control circuit diagram of a PCB assembly according to the prior art.

Figure 2 is a high voltage transformer control circuit diagram of the PCB assembly according to the present invention.

3 is a driving circuit diagram of a microwave oven according to the present invention;

4 is a flowchart showing the operation procedure of the malfunction prevention circuit of the microwave oven according to the present invention;

Explanation of symbols for main parts of the drawings

PORT: Port TR: Transistor

RY: Relay H.V.T: High voltage transformer

R: resistance

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2 is a circuit diagram illustrating a high voltage transformer driving unit of a microwave assembly of a microwave oven according to the present invention. As shown in the drawing, the transistor TR1 connected to the port 1 of the microcomputer and the operation of the high voltage transformer are controlled. Connect the point A between the relay RY1 to the A / D port 2 through the Zener diode ZD, and between the transistor TR3 and the high voltage transformer between the microcom port 3 and the high voltage transformer. And RY3).

According to the present invention configured as described above, the port 1 PORT1 is connected to the transistor 1 TR1 and the relay 1 RY1 as an output port and transmits a signal to turn on / off the relay 1 RY1 as an existing high voltage transformer. HVT), and port 2 (PORT2) is used as an input port as an A / D port. A voltage between transistor 1 (TR1) and relay 1 (RY1) is 12V if relay 1 (RY1) does not operate. When the relay 1 RY1 is operated, the voltage at the point A becomes '0'V, and the voltage input to the port 2 PORT2 becomes' 0'V.

In addition, port 3 (PORT3) is connected to transistor 3 (TR3) and relay 3 (RY3) as an output port and transmits a signal to turn on / off relay 3 (RY3) and is connected to a high voltage transformer (H.V.T).

3 is a circuit diagram of a microwave oven to which the present invention is applied, and as shown in the drawing, one end of an input power source AC has a fuse, a cavity thermostat SW _TH , a primary interlock switch SW1, and a relay. The first switch SW _RY1 and the relay 3 switch SW _RY3 are connected to one end of the high voltage transformer HVT, and the other end of the input power source AC is connected to the other end of the high voltage transformer HVT.

The input terminal of the primary interlock switch SW1 is connected to one end of the low voltage transformer LVT, and the output terminal of the primary interlock switch SW1 is connected to the other end of the low voltage transformer LVT through the interlock monitor switch SW _M. Is connected to.

The input terminal of the relay 1 switch SW _RY1 is connected to one side of the cavity lamp CL via the relay 2 switch SW _RY2 , and the geared motor GM and the fan motor FM connected to the cavity lamp CL. The other end of the cavity lamp (CL) is connected to the output terminal of the input power connected to one end of the high voltage transformer (HVT), the other end of the geared motor (GM) is the interroll motor switch (SW) _M ), and the other end of the fan motor (FM) is connected to the input terminal of one side of the high voltage transformer (HVT).

PCB assembly consists of low voltage transformer (LVT), relay 1 (RY1), relay 2 (RY2), and relay 3 (RY3). The transformer HVT is controlled, and the relay 2 RY2 controls the cavity lamp CL, the geared motor GM, and the fan motor FM, and the output terminal and the relay of the interlock motor switch SW _M. A secondary interlock switch SW2 is connected between the output terminals of the two switches SW _RY2 .

The present invention configured as described above is a high voltage transformer due to the short of the transistor stage connected to the relay 1 (RY1) by adding the relay 3 (RY3) to the conventional control of the high voltage transformer HVT only by the relay 1 (RY1). Even though the HVT is not controlled, the high voltage transformer HVT can be controlled by the relay 3 RY3, thereby preventing malfunction of the high voltage transformer due to the microwave assembly short of the microwave oven.

4 is a flowchart showing the operation procedure by the malfunction prevention circuit of the microwave oven according to the present invention. As shown in the drawing, it is determined whether the high voltage transformer should be operated when the cooking start key is pressed and the high voltage transformer operation command is input. Step S10, if it is determined to be YES in step S10, turning on port 1 and port 3 to operate relay 1 and relay 3 (S11), and saying no in step S10. If it is determined that the voltage value input to the port 2 is changed (S20), and if the voltage value of the port 2 did not change the step of turning off the port 1 and the port 2 and returning (S21), and the voltage of the port 2 If the value is changed, 1 is added to the count, and if the count reaches 10 or more, the port 3 is turned off, an error indication is displayed on the display, and the process is terminated (S22, S23, and S24).

In the present invention, when the operation command of the high voltage transformer is input, the high voltage transformer (HVT) is driven because the output of the port 1 (PORT1) and the port 3 (PORT3) to operate the relay 1 (RY1) and relay 3 (RY3). When there is no transformer (HVT) operation command, it is judged whether the voltage value input to A / D PORT2 has changed, and if it does not change, it turns off port 1 and port 3 and then high voltage transformer. If the voltage input to A / D PORT2 is changed, HVT stops relay 3 (RY3) by turning off port 3 (PORT3). It will be turned off and an error will be shown on the display.

Therefore, even if a short occurs in transistor 1 (TR1) and the high voltage transformer (HVT) is not controlled by the signal of port 1 (PORT1), A at the point A between transistor 1 (TR1) and relay 1 (RY1). Determine the voltage value input to A / D PORT2 and turn off port 3 if it is not constant voltage to prevent malfunction of high voltage transformer due to short of microwave assembly of microwave and short of relay contact. Done.

In the present invention, when a short occurs in transistor 1 (TR1) and the voltage at point A changes, the present invention is directly input to the A / D port, thereby preventing malfunction.

As described above, the present invention adds a transistor, a relay, and a resistor to a conventional circuit component, and uses two microcomputer ports, but uses an A / D port, so that the voltage change is more quickly determined to control the high voltage transformer. The short circuit is generated in the transistor stage (collector and base stage) to operate the relay to operate the relay without giving an operation signal, so that the high voltage transformer is driven to prevent a fire or shorten the life of the microwave oven. It is useful.

Claims (1)

A / D port 2 (A / D) is connected between the transistor TR1 connected to the port 1 of the microcomputer and the relay RY1 controlling the operation of the high voltage transformer HVT through the zener diode ZD. And a port 3 (PORT3) and a high voltage transformer (HVT) through a transistor 3 (TR3) and a relay 3 (RY3).