JPH04111189U - High frequency heating device - Google Patents

Abstract

(57) [Summary] [Purpose] To realize an inverter circuit with excellent safety and reliability. [Structure] A current detection circuit 16 detects the current value input to the rectifying and smoothing circuit 2, converts it into a digital value, and transmits it to the control circuit 9; and a microcomputer 13 that converts the digital value converted by the current detection circuit. A communication circuit 15 that transmits information to
is provided, and if the difference between the input value input to the microcomputer via this communication circuit and the output value instructed by the microcomputer to the control circuit is greater than a specified value,
The microcomputer determines that there is an abnormality and stops the operation of the inverter circuit.

Description

[Detailed explanation of the idea]

0001

[Industrial application field]

This invention is a high-frequency heating device that drives a magnetron using an inverter circuit. It is related to

0002

[Conventional technology]

It rectifies the commercial AC power supply and sets it by the customer by turning the switching element on and off. An inverter circuit that converts the high frequency output into AC power at a frequency (several tens of kHz) This inverter circuit is equipped with a high-frequency generator that supplies power to the magnetron. Conventionally, abnormalities in thermal equipment are detected using the circuit configuration shown in Figure 3. Ta.

0003 In other words, to explain Fig. 3, the commercial AC power supply 1 has a diode bridge 2, a choke A rectification and smoothing circuit consisting of a coil 3 and a smoothing capacitor 4 performs rectification and smoothing. stomach The inverter circuit is connected in parallel to the primary winding 5a of the magnetron drive transformer 5. a resonant capacitor 6, and a semiconductor switch connected in series with the primary winding 5a. It is composed of a control circuit element 7 and a diode 8, and the semiconductor Turns on/off switching element 7 to generate high frequency output on the secondary side of transformer 5 let The high frequency voltage generated in the secondary winding 5b of the transformer 5 is connected to the capacitor 10 and The voltage is rectified and boosted by a voltage doubler rectifier circuit composed of diodes 11. is applied to pin 12. This causes the magnetron 12 to oscillate microwaves. The microcomputer 13 receives a start signal P that instructs the control circuit 9 to operate/stop. and a high frequency output as a data signal D, and the control circuit 9 uses them to perform an inverter. Controls the data circuit.

0004 In the abnormality detection circuit 18, a circuit inserted into the secondary circuit is used to detect overcurrent on the secondary side. The voltage generated across resistor 19 and the reference voltage Vs are compared by comparator C. When an abnormality occurs and an overcurrent flows to the secondary side, the voltage generated across the resistor 19 exceeds the reference voltage Vs. As a result, the output Vo of the comparator C is transmitted to the control circuit 9, and the switch This is to stop the operation of the control element 7.

[0005]

[Problem that the idea aims to solve]

However, this conventional example is for detecting excessive current exceeding a certain value; Variable output high frequency that allows customers to freely select the frequency output according to their cooking needs. In heating equipment, the high frequency output does not change to the low output side due to an abnormality in the control circuit. If it is fixed, it cannot be detected and the food cannot be cooked normally. I can't. Not only that, but in the worst case, the output may be fixed at a level that far exceeds the set value. If this occurs, overheating may lead to a dangerous mode such as causing the food to smoke and catch fire. There is a fear.

[0006]

[Means to solve the problem]

Detects the current value input to the rectifier and smoothing circuit from the commercial AC power supply and converts it digitally. A current detection circuit converts the current value into a value, and a microcomputer uses this digital current value as an input value. A communication circuit is provided to transmit data to the computer. The microcomputer provides instructions to the control circuit. Compare the indicated output value and this fed-back input value, and determine if the difference exceeds the specified value. If it exceeds the limit, it is determined that the output difference is due to a circuit abnormality, and the inverter circuit operation is stopped. make it stop

[0007]

[Effect]

To determine whether the inverter circuit is operating at the set high frequency output. To do this, the current flowing through the inverter circuit is detected, converted to a digital value, and this value is The value is fed back to the microcomputer, and the value and setting are made by the microcomputer. Compare with the fixed value. At this time, if the input value exceeds the specified value when compared with the set value, If there is a large difference, it is determined that an abnormality has occurred.

[0008]

【Example】

An embodiment of the present invention will be described below.

[0009] FIG. 1 is a circuit diagram showing an embodiment of the present invention.

0010 The same parts as in the circuit diagram of the conventional example shown in FIG. 3 are denoted by the same reference numerals.

[0011] Now, the microcomputer 13 informs the control circuit 9 of the inverter circuit. Outputs start signal P to instruct operation/stop and also sets high frequency output The output value is output as a data signal SD1.

0012 Data signal SD1 is 6-bit serial data, which is clocked based on transmission start signal S1. It is transmitted in synchronization with the lock signal CLK. This signal is input to the communication circuit 14, Here, it is converted to 6-bit parallel data by shift register 14a etc. and is transmitted to the comparison section 9a of the control circuit 9 as setting data PD1.

[0013] On the other hand, the current input from the commercial AC power supply 1 to the rectifying and smoothing circuit is a current transformer. 17, and this is input to the current detection circuit 16. Here, the rectified flat The smoothed voltage Vin is converted into 6-bit parallel data PD2 by an A/D converter. This is sent to the comparator 9a of the control circuit 9 as input data via the latch. has been backed up. In the comparison section 9a, this fed-back input data Compare PD2 and the setting data PD1 sent from the microcomputer 13. Then, the result is transmitted to the pulse width control section 9b. This feedback comparison Based on the result, the pulse width controller 9b adjusts the switching element so that PD1=PD2. The output is adjusted by controlling the pulse width of the pulse signal D that drives the output signal D.

[0014] The communication circuit 15 is an input that is fed back from the current detection circuit 16 to the control circuit 9. Take in data PD2 and send it to selector 15a, binary counter 15b, etc. Therefore, as shown in Figure 2, it is converted to 6-bit serial data SD2 and sent to the microcontroller. The fall of the transmission start signal S2 is determined using the clock signal CLK from the computer 13. The data is sent to the microcomputer 13 based on the reference value.

[0015] The microcomputer 13 gave this input data SD2 and instructions to the control circuit 9. Compare the setting data SD1, and if there is a difference of 8 codes or more, it is considered an output difference. Then, the start signal P to the control circuit 9 is turned off, and the operation of the inverter circuit is stopped. let

[0016] Input to the control circuit 9 may be caused by damage to parts of the inverter circuit or failure of the control circuit. The high frequency output may not be performed according to the set data, or the control circuit 9 may not match the set data. The difference between input data and setting data is 8 codes due to data not being received correctly. If any of the above occurs, the microcomputer 13 can recognize this as a malfunction and cause a danger. The operation can be stopped without entering the mode.

[0017]

[Effect of the idea]

As described above, according to the present invention, erroneous output movements that could not be detected conventionally are realized. Realizes an inverter circuit that can detect operation and has excellent safety and reliability. can do.

[0018] In addition, if the control circuit is configured with a digital circuit as in the example, the communication circuit The present invention can be realized at low cost by implementing LSI including It is possible to provide high-frequency heating equipment that is superior in terms of both performance and price.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of an embodiment of the present invention.

FIG. 2 is a signal diagram of the communication section.

FIG. 3 is a circuit diagram of a conventional example.

[Explanation of symbols]

9 Control circuit 13 Microcomputer 14 Communication circuit 15 Communication circuit 16 Current detection circuit

Claims (1)

[Scope of utility model registration request] [Claim 1] A rectifier and smoothing circuit that rectifies and smoothes a commercial power supply to produce a DC power supply, a transformer, a capacitor, a diode,
an inverter circuit composed of switching elements;
A control circuit that controls on/off switching elements of the inverter circuit according to the set high frequency output, a magnetron driven by the high frequency power supply generated by the inverter circuit, and a microcontroller that transmits the set high frequency output to the control circuit. a computer, a first communication circuit that transmits a digital output value from the microcomputer to the control circuit, detects a current value input to the rectifier and smoothing circuit, converts it into a digital value, and transmits the digital output value to the control circuit. A second communication circuit is provided for transmitting the digital value converted by the current detection circuit to the microcomputer, and the digital value is input through the second communication circuit. A high-frequency heating device characterized in that when the difference between an input value and an output value instructed to the control circuit is equal to or greater than a specified value, the microcomputer determines that there is an abnormality and stops the operation of the inverter circuit. .