JPS63221583A - Radio frequency heater - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for capturing door opening/closing signals of an inverter-type high-frequency heating device.

Prior art high frequency heating devices must be configured to stop supplying power to the magnetron when the door is open. Therefore, as shown in FIG. 6, the conventional heating device has a door switch 27 and a door signal switch 28 as means for controlling the supply of electric power to the high voltage conventional transformer 26. , is directly connected to the power line, and the power line is mechanically turned on and off by the opening/closing operation of the door 1. Moreover, the door signal switch 28 is
It is arranged in a drive circuit of a relay 29 that controls power supply to the high voltage transformer 26 and is connected in series to an operating coil 30 of the relay 29 . Therefore, when the door is open, no current flows through the operating coil 3o, the contacts of the relay 29 are separated, and the power line is cut off together with the door switch 2a. On the other hand, the door opening/closing information to the control unit 31 is transmitted to the door signal switch 28 and the resistor 32 and Zener diode 33 connected to the operating coil 30 of the relay 29.
The signal is transmitted by a door signal circuit consisting of or,
A short switch 34 is provided as a protection circuit for shorting the power line when the door 1 is opened.

Next, FIG. 7 shows a configuration in which a semiconductor element such as a triac 36 is used as means for controlling power supply to the high voltage transformer 2θ. Semiconductor elements have less safety against failure than relays, and it is not sufficient to simply include a door signal switch in the drive circuit as in the case of relays; It is inserted into the power line on the opposite side from the door switch 31L of No. 1, and a double door monitor configuration is adopted.

On the other hand, the door signal switch 28 is independently connected to the control section 31 in addition to the semiconductor drive circuit, and inputs the open/closed state of the door to the control section 31. Therefore, in the case of semiconductor control means, switch means for monitoring the movement of the door!
, the second door switch 3a, 3b, the short switch 34, and the door signal switch 28.
pieces are required.

In the conventional example described above, 17 is a relay for controlling the lamp 16 and fan motor 16, 20 is a low voltage transformer for the control section, 21 is a low voltage power supply circuit, and 31 is a control section composed of a microcomputer or the like. 36 is a relay for providing a triac trigger signal.

FIG. 8 shows the state in which the switch is attached to the main body 37.

Problems to be Solved by the Invention Also in an inverter-type high-voltage power supply circuit, semiconductor elements are used as switching elements, so four switches for monitoring the door status are required as described above. As a result, the cost of the extra door switch increases, and the increase in the number of switches from three to four increases the frictional resistance between the door lever and part of the door switch actuator when opening and closing the door. The door force becomes heavy and operability is significantly reduced.

The present invention solves these conventional problems, reduces the number of parts without compromising safety, and also improves the operability of the door.

Means for Solving the Problems The inverter-type high-frequency heating device of the present invention attempts to monitor the opening/closing state of a door using a current transformer that detects a primary current.

The inverter-type high-voltage power supply converts the commercial power source into DC voltage, and then chops this DC voltage using a semiconductor switching element at a chopping frequency of several tens of hertz and applies it to the magnetron drive transformer. 1
This converts power from the primary side to the secondary side. At this time, the current flowing to the primary side is detected and the increase/decrease is fed back to the chopping frequency or on/off duty to keep the converted power constant. To maintain this, a current transformer is installed. By the way, the primary current flows for about 10 people when the magnetron is oscillating, while it flows for about 0.03 people when the magnetron is stopped, and of course it does not flow when the door is open. Therefore, the door opening/closing signal means of the present invention uses a current transformer to big-amplify this difference in current, and compares the resulting voltage with a separately set reference voltage using a comparing means, thereby indicating whether the door is open. The output of the comparison means is configured to be an H level signal at times, and an L level signal when the door is closed, and this signal level is input to the overall cooking control unit to be used as door opening/closing information. .

Therefore, according to the signal input means to the door of the present invention,
This eliminates the need for a dedicated door switch, reduces costs by reducing parts, and dramatically improves smooth performance when opening and closing the door.

Example Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 2 is an external view of a high frequency heating device according to an embodiment of the present invention. Opening/closing information of the door 1 is transmitted by an actuator 2 attached to a part of the door 1 to door switches 32L and 3b installed on the power supply line.

Next, referring to FIG. 1, the configuration for capturing door signal information will be described. The current entering from the power plug 4 passes through the first door switch 3& and enters the rectifier diode 5. Then, via a smoothing capacitor 6, a choke coil 7, etc., a magnetron drive transformer 8 and a switching transistor 9 are connected.
Once again, it passes through one rectifier diode 6 and is now connected to a current transformer 10. Then, it returns to the power supply via the second door switch 3b. By the way, magnetron drive transformer 8
When the switching transistor 9 is turned on, the
While the rectified voltage 142v of 1Qov voltage is applied and turned on, current flows through the magnetron drive transformer 8, and power is converted from the primary side to the secondary side via the transformer 8. ON10 of switching transistor 9
A custom IC is used as the switching control section 11 that performs F F control, and from its No. 1 terminal, the ON10 F F of the switching transistor 9 is output.
A signal is output and applied to the base of the switching transistor 9 via the driver 12. In addition, the voltage across the coil of the magnetron drive transformer 8 is input to the 2nd and 3rd terminals through resistors 13 and 14, and the operation inside the custom IC determines the optimum ON10 F depending on the voltage across the coil.
Creating F timing. A DC voltage signal after rectifying and smoothing the output of the current transformer 1o is input to the No. 4 terminal of the custom IC, and a signal voltage corresponding to the value of the primary current is input to the No. 4 terminal of the custom IC 11. Inside the custom controller C11, the ON10FF duty of the switching transistor 9 is corrected based on the signal voltage from the current transformer 10 so that a predetermined primary current flows, and feedback is applied to maintain a constant value.

On the other hand, the microcomputer 38 controls the cooking device. Predetermined heating cooking is executed in accordance with key input from the keyboard 14. R1 terminal of microcomputer 38 is oven lamp 1
5. The R2 terminal is a control terminal for a relay 17 that turns the cooling fan motor 16 ON10FF, and the R2 terminal is a terminal that outputs a start signal to the switching control section 11. The transistor side becomes conductive, stopping the switching operation described above and interrupting the power supply to the magnetron 19.

Here, a low voltage transformer 20 serves as a power source for the microcomputer 38 and a power source for the switching control unit 11, 21 is a power supply circuit for the microcomputer 38, and 22 is a power supply unit for switching control.

By the way, although the switching control circuit is at the same potential as the ACl 20V line, the entire control circuit of the cooker, such as the microcomputer 38, is electrically connected to the ACl 20V line.
must be insulated.

Therefore, the interface for mutual signal exchange is
Electrical isolation is achieved using a phototransistor.

Next, we will discuss how to input door opening/closing information. 1
The current flowing through the current transformer 10 that detects the next current is current when the door 1 is closed and the magnetron 19
When power is not supplied to the switching transistor 9, that is, the switching transistor 9 is set to 0N10 F F l, and when it is not, the leakage current of the rectifying capacitor 6 and the voltage across the coil of the magnetron drive transformer 8 are detected by the resistor 13.1.
4, approximately 0.03 people. However, when door 1 is opened, the first and second door switches aa, 3
Since b breaks the circuit, the above current becomes zero. (When the magnetron 19 is in operation, about 10 people are saved.) In this way, the comparator 24 compares the output voltage of the current transformer 1o before and after opening and closing the door 1 with the reference voltage separately determined by the reference voltage circuit section 23. Compare the output of this comparator 24 and open the door.
H,! according to the closing operation. : The configuration is such that it is inverted to L.

Therefore, when the door 1 is opened, the output of the comparator 24 becomes ``H'', and current flows through the diode of the phototransistor 26. As a result, 1 becomes ``L'' at the input terminal of the microcomputer 38, and the microcomputer 38 detects that the door 1 is opened. I recognize that.

FIG. 3 shows changes in the current flowing through the current transformer 10 depending on the power supply voltage for each state.

The graph ■ indicates that the magnetron is oscillating, and the graph ■ indicates that the magnetron is not oscillating and the door 1 is closed.

Graph ■ is when door 1 is open. Above, comparator 2
4 detects the door opening/closing state by setting the reference voltage between the voltage values shown in the graphs ■ and ■, which differs from the graphs ■, ■, and ■.

Next, a description will be given of how the above-mentioned door opening/closing signal is taken in and judged inside the microcomputer 38.

In FIG. 4, when the door status changes from ``closed'' to ``open'', the comparator output B changes from tlK'' to 11L,
Changes to +j. As mentioned above, this signal is input to the microcomputer through two terminals, but this signal is once latched programmatically, and the power supply clock D generated from the waveform of the human C7H source C is input to the microcomputer 38.
It is only when the clock input terminal of the microcomputer 38 detects the rising edge of the clock that the microcomputer 38 recognizes that the door status E has changed from "closed" to "open". are exactly the same, and all processes are performed at the timing when the rising waveform of the power supply clock is detected.Therefore, as shown in FIG. The state becomes "o" even though the door is not open, and as a result, the output C of the comparator 24 erroneously outputs a signal that the door 1 is open, but as explained in the above processing procedure. Then, the power supply clock D is connected to the clock input terminal of the microcomputer 38.
Since Eo does not enter, the erroneous output signal from the comparator 24 is ignored. In this way, the output signal from the comparator 24 is latched once and processed at the timing of receiving the power supply clock. This eliminates malfunctions during instantaneous power outages.

In addition, in the above signal processing, an embodiment in which processing is performed programmatically using the microcomputer 38 has been described, but the microcomputer 38
By adding a sample and hold circuit or the like instead of 8, it is also possible to configure it like a node.

Effects of the Invention As described above, according to the present invention, the following effects can be obtained regarding the door signal capture structure of a high-frequency heating device equipped with an inverter-type high-voltage power supply.

(1) By focusing on the fact that the output of the pickup coil of the current transformer is 0'' only when the door is open and a constant output when the door is closed, the current transformer can be used in place of the door signal switch. As a result, fewer parts can be used in the door signal switch.
Significant cost reductions can be achieved.

(2) By eliminating the door signal switch having a mechanical contact mechanism, the operability during the door opening/closing operation becomes easier and the product value is improved.

(3) By adopting a method in which the comparator output signal is processed in synchronization with the power supply clock waveform, the reliability of operation during momentary power outages can be improved.

[Brief explanation of the drawing]

Fig. 1 is an electric circuit configuration diagram of a high frequency heating device showing one embodiment of the present invention, Fig. 2 is an external view of the heating device, Fig. 3 is a graph of current transformer current of one embodiment, Figs. Fig. 5 is an explanatory diagram of door signal capture processing judgment according to an embodiment of the present invention, Figs. 6 and 7 are electrical circuit configuration diagrams of a conventional heating device, and Fig. 8 is an illustration of the installation of a conventional door switch, etc. FIG. sa, 3b...door switch, 6...
... Rectifier diode, e... Smoothing capacitor, 8... Magnetron military transformer, 9...
... Switching transistor, 10 ... Karen l-)-ynce, 11 ... Switching control section, 12 ... Drive section, 24 ... Comparator, 38...Cooking control section. Fig. 2 Fig. 3 4 moss 7 Shike practice, 4 mo = Ji93 (V) maji e-x
: O0 old school cc1υQLLl Figure 8

Claims (1)

[Claims] A magnetron drive transformer and a semiconductor switching element are connected in series to a direct current power source composed of a diode and a capacitor, a drive means for driving the semiconductor switching element, and a detection means for detecting a voltage across the magnetron drive transformer. the current transformer for detecting the current value flowing into the DC power supply; and switching control means for controlling the semiconductor switching element on and off based on the output signal from the current transformer and information on the voltage across the magnetron drive transformer. , a cooking control section for controlling cooking of the heating device, a plurality of door switches inserted into a power supply line for monitoring door opening/closing, and a door signal input means for inputting door opening/closing information to the cooking control section. , as the door signal input means,
The output of the current transformer and a predetermined reference potential,
A high-frequency heating device comprising a comparison means for comparison, and configured such that the output of the comparison means is reversed depending on whether the door switch is open or closed.