JPH0652982A - Inverter power supply device for electronic oven - Google Patents

Abstract

PURPOSE:To eliminate the connection of a switching element to a high voltage section, and to prevent influences which result from that connection by detecting the ON-state of a commercial power supply from a d.c. low voltage power supply of an ON/OFF signal generating circuit, and activating a drive circuit via a start circuit and an on-off signal generating circuit. CONSTITUTION:A re-activating circuit 106 detects, from a low voltage power supply having a d.c. electric power to be supplied to an ON/OFF signal generating circuit 103, a power supply voltage to an inverter 102 from the instantaneous disconnection of a commercial power supply to the recovery of the commercial power supply. This detected signal is provided to a start circuit 105, and a start signal is generated. This start signal causes the ON/OFF signal generating circuit 103 to be oscillated, and an output from this ON/OFF signal generating circuit 103 activates the inverter 102 via a drive circuit 104. This eliminates the connection of the re-activating circuit 106 with a high voltage section, and hence the re-activating circuit 106 is prevented from being affected by influences of a power surge.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter power supply device for a microwave oven, and more particularly to an electronic device having a restart circuit for restarting the inverter circuit after the commercial power is restored from the oscillation stop of the inverter circuit when the commercial power is interrupted. The present invention relates to a range inverter power supply device.

[0002]

2. Description of the Related Art FIG. 4 is a circuit diagram showing a configuration of a conventional restart circuit. The conventional restart circuit 8 shown in FIG. 4 is connected to the points A, B and F of the circuit shown in FIG. 2 and the control voltage Vcc.
FIG. 2 is a circuit diagram of an inverter power supply device for a microwave oven. Since FIG. 2 will be described later in this embodiment, a description of normal operation is omitted.

An ON signal generation circuit 3 and an OFF signal generation circuit 4 having a circuit configuration as shown in FIG. 2 generate timings by charging / discharging a current to generate an ON / OFF signal, and the ON / OFF signal is driven by the drive circuit. When the switching element Q1 of the inverter circuit 2 is driven after the current is amplified by 5, the power supply is momentarily cut off, the resonance voltage due to the switching operation of the inverter circuit 2 does not appear at point A,
The-input side voltage of the comparator COMP3 of the ON signal generation circuit 3 becomes equal to or lower than the + input side voltage, and the output of COMP3 continues to be open (high voltage).

Therefore, the diode D3 of the OFF signal generating circuit 4 continues to be OFF, the capacitor C4 is charged to the voltage of the point C through the transistor Q3, and the comparator COM
The output of P2 continues to be ON (Low voltage) and drive circuit 5
Output is OFF and switching element Q1 is OFF
Continues.

In such a state, even if the power supply recovers from a momentary interruption, unless the switching element Q1 is turned on by some method (for example, the operation of the start switch), the inverter circuit continues to be turned off. Therefore, there is a method of providing a restart circuit. Are known.

Here, points A, B, and F of the circuit shown in FIG.
An example in which the conventional restart circuit 8 shown in FIG. 4 is connected to the point and the control voltage Vcc will be described. It utilizes the fact that the DC voltage rectified and smoothed by the diode bridge DB1 and the capacitor C1 appears at point A after the power is restored from the power interruption. After the power is restored, the diode D5 continues to be turned off and the capacitor C
4 continues to be charged through the resistor R22 to turn on the Zener diode ZD2 and then to turn on the transistor Q6, the electric charge of the capacitor C4 is discharged through the transistor Q6, the voltage at the point B drops, and the output of the comparator COMP2 opens ( High voltage) and the switching element Q1 is turned O
Then, the diode D5 is turned on and the capacitor C6 is discharged to start normal operation.

The operation of the restart circuit 8 during the normal operation of the switching element Q1 will be described. When the switching element Q1 is off, the diode D5 is also off,
The capacitor C6 is charged, but when the switching element Q1 is ON, the diode D5 is also ON and the charge of the capacitor C6 is discharged through the diode D5.

Therefore, the resistors R22 and R23 are appropriately selected, the time constants for charging and discharging the capacitor C6 are set to appropriate values, and the zener diode ZD2 is turned on during normal operation.
It is configured not to N.

[0009]

However, in the configuration of the conventional restart circuit 8, as shown in FIGS. 2 and 4, the voltage generated by the switching element Q1 at the point A reaches about 600 V during normal operation. . Also, if a surge occurs in the commercial power source at point A, it is also affected. Therefore, since the input part of the conventional restart circuit 8 is connected to the high voltage part, it is easily affected by a surge or the like, and thus the input part of the restart circuit is required to have a high withstand voltage component. Further, there is a problem that the circuit configuration is complicated and the reliability is low.

The present invention has been made in consideration of the above circumstances, and eliminates the connection with the high-voltage section and simplifies the circuit structure, thereby providing a microwave oven having a restart circuit having a circuit structure with higher reliability. A power supply device for an inverter is provided.

[0011]

FIG. 1 is a block diagram showing a circuit configuration of the present invention. In FIG. 1, a rectifying / smoothing circuit 101 for full-wave rectifying a commercial power source and converting it into DC power,
Inverter circuit 102 that converts the converted DC power into high-frequency high power that drives a magnetron for a microwave oven with a switching element, and by charging / discharging the current obtained by using the DC power from the rectifying / smoothing circuit as a low voltage source. An on / off signal generation circuit 103 that generates timing and generates an on / off signal, a drive circuit 104 that drives a switching element of the inverter circuit 102 by the generated on / off signal, and when starting the inverter circuit 102 After the commercial power is restored from the start circuit 105 that generates a start signal for oscillating the on / off signal generating circuit 103 by the operation of the start switch or the input of an electric signal, and the oscillation stop of the inverter circuit 102 when the commercial power is interrupted Power supplied to the on / off signal generation circuit 103 A restart circuit 106 for restarting the inverter circuit by detecting from a low voltage source and applying an electric signal obtained by the detection to the start circuit 105 and controlling to generate a start signal is provided. It is an inverter power supply device for a microwave oven.

In the present invention, the rectifying / smoothing circuit 1
01 and the inverter circuit 102 are composed of components such as a high breakdown voltage diode, a diode bridge, a capacitor, a transistor (including FET), and a transformer. As the on / off signal generation circuit 103, the drive circuit 104, the start circuit 105, and the restart circuit 106, parts such as low voltage diodes, zener diodes, capacitors, transistors, resistors, and comparators (IC parts,
Hybrid IC parts).

[0013]

According to the present invention, in FIG. 1, the rectification / smoothing circuit 101 performs full-wave rectification on the commercial power source to convert the DC power into DC power, and the switching element of the inverter circuit 102 drives the magnetron for microwave oven at a high frequency. In order to convert to electric power, the rectification / smoothing circuit 101 turns on by charging / discharging a current obtained by using DC power as a low voltage source.
The off signal generation circuit 103 generates timing to generate an on / off signal, and drives the switching element of the inverter circuit 102 by the generated on / off signal.
When driving the inverter circuit 102 by driving the start circuit 105, the start circuit 105 operates the start switch or inputs an electric signal to turn on / off the signal generating circuit 10.
A start signal for oscillating 3 is generated. The restart circuit 106 detects and detects the power supply voltage after the commercial power is restored from the oscillation stop of the inverter circuit 102 when the commercial power is momentarily cut off, from the low voltage source of the DC power supplied to the on / off signal generating circuit 103. The inverter circuit 102 can be restarted by applying the obtained electric signal to the start circuit 105 and controlling it to generate a start signal.

Therefore, since the restart circuit 106 automatically generates a start signal from the start circuit 105 after the commercial power is restored after the oscillation of the inverter circuit 102 is stopped when the commercial power is interrupted, the start signal is automatically generated from the start circuit 105. The circuit 102 continues to operate normally. Further, since the restart circuit 106 is connected to a low voltage source to detect the power supply voltage after the commercial power supply is restored, the circuit can be configured with low voltage components.
Therefore, the circuit is simplified and the reliability is improved.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the embodiments shown in the drawings. The present invention is not limited to this.

FIG. 2 is a circuit diagram showing the structure of an inverter power supply device for a microwave oven. In FIG. 2, a schematic configuration of an inverter power supply device for a microwave oven includes a rectifying / smoothing circuit 1 (including a filter), an inverter circuit 2 (including a switching element Q1 and a resonance circuit), an ON signal generating circuit 3, OF.
It is composed of an F signal generation circuit 4, a drive circuit 5, and a start circuit 6.

The commercial power supply AC is full-wave rectified by the diode bridge DB1 of the rectifying / smoothing circuit 1 and converted into direct current. Further, the direct current is the choke coil C of the rectifying / smoothing circuit 1.
It is smoothed through a filter composed of H1 and capacitor C1, and supplied to an inverter circuit 2 composed of a capacitor C2, a transformer T1, a switching element Q1, and a flywheel diode D1. The DC power supplied to the inverter circuit 2 is converted into a high frequency by the switching operation of the switching element Q1 and is boosted by the transformer T1, and the high voltage capacitor CHV1 and the high voltage diode D are supplied.
The voltage is rectified by HV2 and the high frequency power is supplied to the magnetron MQ1.

In the inverter power supply device for a microwave oven configured as described above, as the voltage waveform at point A during operation, the emitter-collector saturation voltage (several V) appears when the switching element Q1 is ON, and the switching element Q1 is turned on. When Q1 is off, the resonance voltage of the resonance circuit formed by the primary winding of the transformer T1 and the capacitor C2 appears (not shown).

Here, the normal operation of the inverter circuit 2, the ON signal generation circuit 3, the OFF signal generation circuit 4, the drive circuit 5, and the start circuit 6 will be briefly described. First, the start switch S1 of the start circuit 5 is turned ON. Then, the output of the comparator COMP1 opens (High
Voltage) → the output of the start circuit 6 (transistor Q2) is ON → the voltage on the negative side of the comparator COMP2 (the capacitor C4 is discharged / the voltage at the point B) decreases → the drive circuit 5
Is a low voltage (the output of the comparator COMP2 is open) → the output of the drive circuit 5 is OFF → the switching element Q1 remains in the OFF state

When the start switch S1 is turned off, the −input side voltage of the comparator COMP1 rises → the output of the comparator COMP1 turns on → the output of the transistor Q2 opens (high voltage) → the input of the drive circuit 5 becomes high.
Voltage → output of drive circuit 5 is high voltage → switching element Q1 is ON.

Next, the voltage on the minus input side of the comparator COMP3 decreases → the output of the comparator COMP3 opens (High voltage) → the voltage at the point B (the capacitor C4 charges) rises to the EI voltage → the output of the comparator COMP2 turns ON ( Low voltage) → Output of drive circuit 5 is OFF → Switching element Q1 is OFF → Comparator COMP3
-The input side voltage rises → the output of the comparator COMP3 is ON (Low voltage) → the voltage at the point B (the capacitor C4 is discharged) decreases → the output of the comparator COMP2 is open → the output of the drive circuit 5 is a high voltage → the switching element Q1 turns on.

In this way, the above-mentioned operations are repeated and the ON / OFF signal is supplied to the switching element Q2 to drive the inverter circuit 2. However, if the power supply is momentarily cut off during the operation of the inverter circuit 2, the resonance voltage does not appear at the point A, and the comparator COMP3 of the ON signal generation circuit 3 has a negative voltage.
The input side voltage becomes equal to or less than the + input side voltage, and the output of COMP3 remains open (high voltage).

Therefore, the diode D3 of the OFF signal generating circuit 4 continues to be OFF, the capacitor C4 is charged to the voltage at the point C through the transistor Q3, and the comparator COM
The output of P2 continues to be ON (Low voltage) and drive circuit 5
Output is OFF and switching element Q1 is OFF
Keep doing

Even if the power supply recovers from the momentary interruption in such a state, the inverter circuit 2 will continue to be turned off unless the switching element Q1 is turned on by some method (for example, the operation of the start switch). Therefore, a restart circuit is provided. There is.

FIG. 3 is a circuit diagram showing an embodiment of the restart circuit of the present invention. An embodiment in which points B, E and F of FIG. 2 and the restart circuit 7 of the present invention shown in FIG. 3 are connected will be described.

The voltage of the capacitor C4 (the voltage at the point B) that determines the ON time width of the switching element Q1 in the OFF signal generation circuit 4 of FIG. 2 is the maximum reference voltage E1 during normal operation.
Only a little higher. However, when the inverter oscillating operation at the momentary power failure is stopped, the voltage rises to the point C. Further, the voltage rises to the voltage at point D after the power supply recovers from the instantaneous interruption.

Therefore, it is detected based on the Zener voltage (reference voltage) of the Zener diode ZD3 that the voltage at the point B has risen to the voltage at the point D (voltage obtained by dividing the power supply voltage by the resistors R7 and R8), and the transistor is turned on. At Q7, the capacitor C3 of the start circuit 6 is discharged, a start signal is generated, and the switching element Q1 is restarted.

In other words, the voltage at point B in FIG. 2 is only slightly higher than the reference voltage E1 during normal operation,
When the power supply is momentarily cut off, the control power supply Vcc is selected to be higher than the value (voltage at point C) divided by resistors R9 and R10, and lower than the value (voltage at point D) divided by resistors R7 and R8. Therefore, at the time of normal operation and power interruption, the Zener diode ZD3 shown in FIG.
Therefore, the transistor Q7 is not turned on, and the restart circuit 7 of FIG. 3 continues the state in which nothing is operated (standby state).

Here, when the power supply is momentarily cut off and restored, the voltage at the point B rises and exceeds the Zener voltage, so the Zener diode ZD3 is turned on, and then the transistor Q7 is turned on.
Then, the electric charge of the capacitor C3 of the start circuit 6 is discharged through the transistor Q7, and the voltage at the point E decreases.

The voltage at the point E is + of the comparator COMP1.
When the voltage drops to the input side voltage, the output of the comparator COMP1 becomes open (high voltage), and the transistor Q2 turns off.
At the same time as N, the voltage on the + input side of the comparator COMP1 is raised by the hysteresis circuit composed of the resistor R4, and a stable start signal (Low voltage) is generated.

By turning on the transistor Q2,
The electric charge of the capacitor C4 of the OFF signal generating circuit 4 is discharged through the resistor R12, the diode D3 and the transistor Q2, and the output of the comparator COMP2 becomes open.

Therefore, at this time, the outputs of the comparators COMP2 and COMP3 are both open, but since the transistor Q2 is ON, the comparator COMP2
Since the outputs of COMP3 and COMP3 both become Low voltage, the output of drive circuit 5 becomes OFF and switching element Q1
Is also turned off.

Since the electric charge of the capacitor C4 is also discharged, the Zener diode ZD3 of the restart circuit 7 is turned off.
Also, the transistor Q7 is also turned off, its restarting operation is stopped, and the capacitor C3 of the start circuit 6 starts to be charged by the control power supply Vcc through the resistor R1, as in the normal state where the normal start switch S1 is opened. Become.

Therefore, the voltage at the point E becomes the comparator COM.
When the voltage on the + input side of P1 is reached, the comparator COM
The output of P1 becomes Low voltage, and the transistor Q2 becomes OF.
Then, the outputs of the comparators COMP2 and COMP3 both become high voltage, and the switching element Q1 is turned on.

At the same time, the diode D3 of the OFF signal generating circuit 4 is also turned OFF, charging of the capacitor C4 begins, and the comparator COMP is reached when the voltage at the point B reaches the reference voltage E1.
Low voltage is output from 2 and switching element Q1 is O
Normal switching operation such as FF is repeated.

By configuring the restart circuit 7 as described above, the connection of the high voltage section is eliminated, and the power supply after the power supply is restored using the time constants of the resistors R22 and R23 and the capacitor C6 as in the conventional example. Since a circuit for detecting the voltage is not necessary, the circuit configuration is simplified and the reliability is improved.

[0037]

According to the present invention, the configuration of the restart circuit as shown in FIG. 3 eliminates the connection with the high voltage portion of the switching element, and the structure which is not affected by the power surge or the like can be realized. , Furthermore, the circuit configuration is simplified,
Reliability can also be improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing a circuit configuration of the present invention.

FIG. 2 is a circuit diagram showing a configuration of an inverter power supply device for a microwave oven.

FIG. 3 is a circuit diagram showing an embodiment of a restart circuit of the present invention.

FIG. 4 is a circuit diagram showing a configuration of a conventional restart circuit.

[Explanation of symbols]

 1 Rectification / Smoothing Circuit 2 Inverter Circuit 3 ON Signal Generation Circuit 4 OFF Signal Generation Circuit 5 Drive Circuit 6 Start Circuit 7 Restart Circuit (Example of the Present Invention) 8 Restart Circuit (Conventional Example)

Claims (1)

[Claims] 1. A rectifying / smoothing circuit for full-wave rectifying a commercial power source to convert it into DC power, an inverter circuit for converting the converted DC power into high-frequency high power for driving a magnetron for a microwave oven, and a rectifier.・ Charging the current obtained by using the DC power from the smoothing circuit as a low voltage source
An on / off signal generation circuit that generates timing by discharging and generates an on / off signal, a drive circuit that drives the switching element of the inverter circuit by the generated on / off signal, and a start when starting the inverter circuit A start circuit that generates a start signal to oscillate the on / off signal generation circuit when a switch is activated or an electric signal is input, and the power supply voltage is turned on after the commercial power is restored from the oscillation stop of the inverter circuit when the commercial power is cut・ Re-start the inverter circuit by detecting from a low voltage source of DC power supplied to the off signal generation circuit and controlling the generated electric signal to the start circuit to generate a start signal. An inverter power supply device for a microwave oven, which is provided with a starting circuit.