JP3109173B2 - Inverter control circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter control circuit for an electromagnetic cooker or the like mainly used at home.

[0002]

2. Description of the Related Art In recent years, a method of directly controlling an inverter by a microcomputer has become mainstream.

Conventionally, this kind of inverter control circuit is shown in FIG.
The configuration is as shown in FIG. Hereinafter, the configuration and operation will be described with reference to FIG.

As shown in FIG. 5, an output of a rectifier circuit 1 for rectifying an AC power is input to an inverter circuit 2. The inverter circuit 2 converts the output of the rectifier circuit 1 into an AC power having a predetermined frequency. Reference numeral 3 denotes an overvoltage detection circuit, and a rectifier circuit 1
Alternatively, it detects whether the voltage applied to the inverter circuit 2 is higher or lower than the value at which the inverter circuit 2 operates normally, and outputs signals corresponding to these two states.
Reference numeral 4 denotes a control circuit which supplies a drive signal to the inverter circuit 2 to control the operation of the inverter circuit 2 and receives an output signal of the overvoltage detection circuit 3 so that a voltage applied to the rectifier circuit 1 or the inverter circuit 2 When the value is larger than the value at which the inverter circuit 2 operates normally, control is performed so that the operation of the inverter circuit 2 is stopped for a certain time.

Here, the main circuit of the control circuit 4 is a microcomputer, and the output of the overvoltage detection circuit 3 is generally input to an interrupt terminal of the microcomputer. When the voltage applied to the rectifier circuit 1 or the inverter circuit 2 is higher than the value at which the inverter circuit 2 operates normally, the output signal of the overvoltage detection circuit 3 is input, and then the operation to stop the operation of the inverter circuit 2 is instructed. About 10 steps are required for each step.

[0006]

In such a conventional inverter control circuit, an interrupt terminal of a microcomputer to be used is necessary for other purposes, and the number of interrupt terminals may be insufficient. There was a problem that using many microcomputers generally increased the cost. When the instruction processing speed of the microcomputer used is low, the rectifier circuit 1
Alternatively, the time from when the voltage applied to the inverter circuit 2 becomes larger than the value at which the inverter circuit 2 operates normally to when the control circuit 4 stops the operation of the inverter circuit 2 becomes longer, and the inverter circuit 2 is broken. There was a problem that would. Further, if a microcomputer having a high instruction processing speed is used for this measure, there is a problem that the cost generally increases.

The present invention solves the above-mentioned problem. Even if the microcomputer does not have an interrupt terminal and the instruction processing speed is low, the voltage applied to the rectifier circuit or the inverter circuit allows the inverter circuit to operate normally. When the value becomes larger than the value, the operation of the inverter circuit can be stopped instantaneously, and when the voltage applied to the rectifier circuit or the inverter circuit reaches a value that allows the inverter circuit to operate normally, restart the inverter circuit. It is an object of the present invention to provide an inverter control circuit with high safety and low cost.

[0008]

According to the present invention, there is provided a rectifier circuit for rectifying an AC power supply, and an inverter circuit for receiving an output of the rectifier circuit and converting the output of the rectifier circuit into an AC power supply having a predetermined frequency. An overvoltage detection circuit that detects whether the voltage applied to the rectifier circuit or the inverter circuit is larger or smaller than a value at which the inverter circuit operates normally, and outputs a signal corresponding to the two states; When the output of the overvoltage detection circuit is input and the voltage applied to the rectifier circuit or the inverter circuit is larger than a value at which the inverter circuit operates normally, the output corresponding to this state is maintained for a certain period of time, A signal maintaining circuit for outputting the signal maintained for a certain period of time to the inverter circuit as an output signal to stop the operation of the inverter circuit; A drive signal is supplied to the inverter circuit to control the operation of the inverter circuit, and an output signal of the signal maintaining circuit is inputted for a certain period of time, and the voltage applied to the rectifier circuit or the inverter circuit causes the inverter circuit to operate normally. when it becomes larger than the value of work, the
A signal to stop the operation of the inverter circuit within a certain time
Signal and the inverter circuit operates normally.
Time each part of the voltage to allow work is to stabilize, and a you stop control circuit The operation of the inverter circuit.

[0009]

According to the present invention, when the voltage applied to the rectifier circuit or the inverter circuit is higher than the value at which the inverter circuit operates normally, the overvoltage detection circuit detects the voltage and outputs the output signal. a certain time kept by the time signal maintained circuit, and input to the inverter circuit a signal maintaining the predetermined time interval the output signal, and at the same time stops the operation of the inverter circuit, the inverter circuit is operating normally
As long as possible, the operation of the inverter circuit can be stopped until the voltage of each section is stabilized .

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. 1, 2, 3 and 4. FIG.

FIG. 1 is a block diagram of the present invention. In FIG. 1, a rectifier circuit 5 rectifies an AC power supply. The inverter circuit 6 receives the output of the rectifier circuit 5 and converts the output into an AC power supply having a predetermined frequency. The overvoltage detection circuit 7 detects that the voltage applied to the rectifier circuit 5 or the inverter circuit 6 is
It detects whether the value is larger or smaller than the value at which the inverter circuit 6 operates normally, and outputs signals corresponding to these two states. The signal maintaining circuit 8 receives the output of the overvoltage detection circuit 7 for a certain period of time, and enters this state when the voltage applied to the rectifier circuit 5 or the inverter circuit 6 is larger than the value at which the inverter circuit 6 operates normally. The corresponding output is maintained for a predetermined time, and the signal maintained for the predetermined time is output to the inverter circuit 6 as an output signal, and the operation of the inverter circuit 6 is stopped. Further, a drive signal is supplied to the inverter circuit 6 to control the operation of the inverter circuit 6, and an output signal of the signal maintaining circuit 8 is inputted for a certain period of time, and the voltage applied to the rectifier circuit 5 or the inverter circuit 6 Is provided with a control circuit 9 for controlling the operation of the inverter circuit 6 to be stopped for a certain period of time when the value becomes larger than the value for normal operation.

FIG. 2 is a circuit diagram of one embodiment of the present invention.
In FIG. 2, a rectifier circuit 5 rectifies an AC power supply 10. The capacitor 11 and the coil 12 are inserted between the rectifier circuit 5 and the inverter circuit 6 to prevent noise generated in the inverter circuit 6 from returning to the AC power supply 10. The inverter circuit 6 receives the output of the rectifier circuit 5 and converts the output from the microcomputer 9 into an AC power supply having a predetermined frequency.

The overvoltage detection circuit 7 divides the output voltage of the rectifier circuit 5 by resistors 7a, 7b and 7d. The capacitor 7c is connected in parallel with the resistor 7b. The anode of the LED 7e is connected to a connection point between the resistor 7b and the resistor 7d.
The cathode of the LED 7e is connected to the capacitor 7f, the resistor 7g, the resistor 7h, and the negative terminal of the comparator 7k.

One side of the capacitor 7f and the resistor 7h is connected to the ground, and one side of the resistor 7g is connected to the output of the DC power supply 13. DC power supply 13 receives AC power supply 10 as input and outputs DC power supply. A resistor 7 is connected to the + terminal of the comparator 7k.
i and the resistor 7j are connected. One side of the resistor 7i is connected to the output of the DC power supply 13, and one side of the resistor 7j is connected to the ground. Reference numeral 8 denotes a signal maintaining circuit for a fixed time,
The output terminal of k is connected to the resistor 8a. One side of the resistor 8a is connected to the resistor 8b, the capacitor 8c, and the + terminal of the comparator 8f. One side of the resistor 8b is connected to the output of the DC power supply 13, and one side of the capacitor 8c is connected to the ground. The resistor 8d and the resistor 8e are connected to the minus terminal of the comparator 8f. One side of the resistor 8d is connected to the output of the DC power supply 13, and one side of the resistor 8e is connected to the ground. Comparator 8f
Is connected to the cathode terminal of the diode 8h. The anode terminal of the diode 8h is a resistor 8g.
And an input terminal and an output terminal of the microcomputer 9. One side of the resistor 8g is connected to the output of the DC power supply 13. The microcomputer 9 is connected to a DC power supply which is an output of the DC power supply circuit 13, and is connected to a switch 14 which can externally set whether the inverter circuit 6 is to be operated or not. The capacitor 15 is connected to prevent noise from the AC power supply.

The operation of the above configuration will be described with reference to the flowchart of FIG. In step 20, the microcomputer 9 detects whether the switch 14 has been pressed. Until the switch 14 is pressed, the microcomputer 9 operates so that the inverter circuit 6 is stopped.
Outputs a low-level output signal. When the switch 14 is pressed, the process proceeds to step 21. In step 21, the overvoltage detection circuit 7 detects whether the voltage applied to the rectifier circuit 5 or the inverter circuit 6 is higher than a value at which the inverter circuit 6 operates normally. Here, in order to detect whether or not an overvoltage is applied, the microcomputer 9 drives the inverter circuit 6 with the output terminal open. At this time, the microcomputer 9
If the input terminal is at a high level, no overvoltage is detected, and the process proceeds to step S22. In step 22,
Since no overvoltage is applied, the comparator 7k
A value obtained by dividing the DC power supply by the resistors 7g and 7h is input to the terminal. A resistor 7 is connected to the + terminal of the comparator 7k.
The value obtained by dividing the DC power supply by i and the resistor 7j is input, and the value is set to be larger than the value obtained by dividing the DC power supply by the resistors 7g and 7h. As a result, the output terminal of the comparator 7k becomes open.

Therefore, the output signal of the signal maintaining circuit 8 is at a high level for a fixed time. That is, the capacitor 8c is charged to the output voltage of the DC power supply circuit 13 through the resistor 8b,
The signal is input to the + terminal of the comparator 8f. As a result, the output of the comparator 8f is in an open state, and a high level is input to the input of the microcomputer 9.

Next, the process returns from step 22 to step 21. In step 21, when the voltage applied to the rectifier circuit 5 or the inverter circuit 6 is larger than the value at which the inverter circuit 6 operates normally, the voltage of the anode terminal of the LED 7e increases, and the voltage of the minus terminal of the comparator 7k becomes It becomes higher than the voltage of the + terminal of the comparator 7k. As a result, the output terminal of the comparator 7k becomes low level, the electric charge charged in the capacitor 8c is discharged through the resistor 8a, the + terminal of the comparator 8f becomes low level, and the output voltage of the comparator 8f becomes low level. Thus, the output of the microcomputer 9 is set to the low level through the resistor 8g and the diode 8h, and the operation of the inverter circuit 6 is forcibly stopped. At the same time, a low level is input to the input of the microcomputer 9. Here, the time during which the voltage applied to the rectifier circuit 5 or the inverter circuit 6 is higher than the value at which the inverter circuit 6 normally operates is short, and once the voltage at the anode terminal of the LED 7e increases, the output of the comparator 7k is increased. After the terminal goes low, the charge charged in the capacitor 8c is discharged through the resistor 8a and the + terminal of the comparator 8f goes low, and the voltage applied to the rectifier circuit 5 or the inverter circuit 6 causes the inverter circuit 6 to operate normally. Even if the value becomes the value, the capacitor 8c is charged through the resistor 8b, and the output terminal of the comparator 8f becomes low level for a certain period of time until the charged voltage becomes higher than the voltage of the negative terminal of the comparator 8f. Therefore, once the overvoltage is detected, the inverter circuit 6 can be forcibly stopped for a certain time determined by the resistor 8b and the capacitor 8c. Further resistance 8
Since a low-level signal can be input to the microcomputer 9 for a certain time determined by b and the capacitor 8c, it is possible to determine that an overvoltage has been detected even if the input terminal of the microcomputer 9 has no interrupt function. Furthermore, even if the instruction execution speed of the microcomputer 9 is low, it is possible to secure a sufficient processing time. Then step 23
Proceed to. The microcomputer 9 inputs that the output terminal of the comparator 8f is at a low level for a certain period of time, and the voltage applied to the rectifier circuit 5 or the inverter circuit 6 becomes larger than the value at which the inverter circuit 6 operates normally. And outputs a low-level signal so as to stop the operation of the inverter circuit 6 for one second. Here, the operation of the inverter circuit 6 is stopped for one second,
The time for stopping the operation may be a time during which the voltage of each section is stabilized so that the inverter circuit 6 can operate normally.

Next, the routine proceeds to step 24. The microcomputer 9 sets the output to an open state and gives a signal for operating the inverter circuit 6, and proceeds from step 24 to step 21 to repeat the above operation.

The voltage waveforms of the respective parts described in the operation of the flowchart of FIG. 3 will be described with reference to FIGS. (1)
Is the output voltage of the rectifier circuit 5 and is a normal voltage until time t1. An abnormal voltage occurs at time t1,
Returns to normal voltage. (2) is-of the comparator 7k.
The voltage at the terminal, (3), is the voltage at the + terminal of the comparator 7k. The voltage at the negative terminal of the comparator 7k is usually
If the voltage at the negative terminal of the comparator 7k is lower than the voltage at the positive terminal of the comparator 7k and an abnormal voltage occurs at time t1, the voltage at the negative terminal of the comparator 7k becomes higher than the voltage at the positive terminal of the comparator 7k. (4) is the voltage of the output terminal of the comparator 7k, which is at a low level while an abnormal voltage is occurring. (5) is the voltage at the + terminal of the comparator 8f,
(6) is the voltage at the negative terminal of the comparator 8f. The voltage at the + terminal of the comparator 8f becomes low level when an abnormal voltage occurs, and when the abnormal voltage returns to normal, the resistor 8
b, and rises at a time constant determined by the capacitor 8c. At time t2, the voltage at the + terminal of the comparator 8f becomes higher than the voltage at the-terminal of the comparator 8f. (7)
This is the voltage of the output terminal of the comparator 8f. The voltage at the output terminal of the comparator 8f goes low at time t1 and goes high at time t2.

As described above, once an overvoltage is detected,
The inverter circuit 6 can be forcibly stopped for a predetermined time determined by the resistor 8b and the capacitor 8c. Further, since a low-level signal can be input to the microcomputer 9 for a predetermined time determined by the resistor 8b and the capacitor 8c, it can be determined that an overvoltage has been detected even if the input terminal of the microcomputer 9 does not have an interrupt function. Furthermore, even if the instruction execution speed of the microcomputer 9 is low, it is possible to secure a sufficient processing time.

[0021]

As apparent from the above embodiments, according to the present invention, the voltage applied to the rectifier circuit or the inverter circuit can be reduced even if the microcomputer does not have an interrupt terminal and the instruction processing speed is low. When the value of the circuit becomes larger than normal, the operation of the inverter circuit can be stopped instantaneously, and when the voltage applied to the rectifier circuit or the inverter circuit becomes a value that allows the inverter circuit to operate normally, The circuit can be restarted normally, the safety is high, the cost is low, and the inverter circuit can be controlled.

[Brief description of the drawings]

FIG. 1 is a block diagram of an inverter control circuit according to the present invention.

FIG. 2 is a circuit diagram of an inverter control circuit showing one embodiment of the present invention.

FIG. 3 is a flowchart showing an operation of the inverter control circuit according to the embodiment of the present invention;

FIG. 4 is a voltage waveform diagram of each part of the inverter control circuit showing one embodiment of the present invention.

FIG. 5 is a block diagram of a conventional inverter control circuit.

[Explanation of symbols]

 5 Rectifier circuit 6 Inverter circuit 7 Overvoltage detection circuit 8 Signal maintenance circuit for a fixed time 9 Control circuit

──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Shinichi Sato 1006 Kazuma Kadoma, Osaka Pref. Matsushita Electric Industrial Co., Ltd. (72) Inventor Michimasa Sugihara 1006 Kazuma Kadoma Kadoma, Osaka Pref. Matsushita Electric Industrial Co., Ltd. In-company (56) References JP-A-63-231895 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H05B 6/12 H02M 7/48

Claims (1)

(57) [Claims] 1. A rectifier circuit for rectifying an AC power supply, an inverter circuit for receiving an output of the rectifier circuit and converting the output to an AC power supply having a predetermined frequency, and a voltage applied to the rectifier circuit or the inverter circuit, An overvoltage detection circuit that detects whether the inverter circuit is larger or smaller than a value at which the inverter circuit normally operates and outputs signals corresponding to these two states, and an output of the overvoltage detection circuit, and the rectifier circuit or the When the voltage applied to the inverter circuit is larger than the value at which the inverter circuit operates normally, the output corresponding to this state is maintained for a certain period of time, and the signal maintained for this predetermined time is output to the inverter circuit as an output signal. A signal maintaining circuit for stopping the operation of the inverter circuit for a fixed time; Controls the operation of the road, when the voltage applied to the rectifier circuit or the inverter circuit receives the output signal of the fixed time signal maintaining circuit becomes larger than the value which the inverter circuit to operate properly, the
A signal to stop the operation of the inverter circuit within a certain time
Signal and the inverter circuit operates normally.
Time each part of the voltage to allow work is to stabilize, the inverter control circuit having a that control circuit to stop operation of said inverter circuit.