JPH0729675A - High frequency heating device - Google Patents

Abstract

PURPOSE:To easily and safely suppress the dispersion in operating time of a relay by applying a voltage larger than the rated voltage of the coil of the relay to the coil only at the start of voltage application. CONSTITUTION:When a relay 10 is in OFF state, the charge of a voltage E1 is charged in a capacitor 31 by resistors 29, 30, and voltages of 0V and -E1 are applied to the resistor 30 side and the resistor 29 side, respectively. When a relay drive signal is then outputted from a microcomputer 16, a transistor 26 is ON, and since the resistor 30 side potential of the capacitor 31 is about -E1 at this moment, the resistor 29 side potential is 2E1. Since this voltage is limited by the Zener voltage V2 of a Zener diode 22, it is clamped when it exceeds -V2. Just after a relay signal is outputted from the microcomputer 16 to a relay coil 10b, a voltage larger than the rated voltage is applied, and the rated voltage, or a voltage lower than the rated voltage is applied in the steady state. Then, the operating time of the coil 10b is shortened, and its dispersion can be easily and safely suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive control configuration of a relay in a high frequency heating apparatus having a relay for controlling heating means.

[0002]

2. Description of the Related Art As a drive control configuration of this type of relay, for example, as shown in Japanese Patent Application Laid-Open No. 2-160393,
There is a method in which a bias current is passed through the relay coil to shorten the operating time of the relay, thereby suppressing variations in operating time and suppressing inrush current generated in the high frequency circuit.

[0003]

However, a large bias current is required in order to suppress the variation in operating time by flowing the bias current through the relay coil as described above. Therefore, if there are variations in the relay characteristics, the bias current will turn on the relay contacts or
It may not turn off from the N state.
There is a risk of equipment failure or fire.

The present invention has been made in view of the above problems, and an object thereof is to suppress variations in relay operation time easily and safely.

[0005]

According to the present invention, in a high frequency heating apparatus having a relay for controlling heating means, a relay drive for applying a voltage higher than a rated voltage of the coil to a coil of the relay only when voltage application is started. It is configured to include a circuit.

[0006]

Function When the voltage applied to the coil of the relay coil is started, a voltage higher than the rated voltage is applied to the coil, whereby the operation time of the relay is shortened, and thereafter, the coil is driven at a voltage of the rated value to the rated value or less.

[0007]

FIG. 1 shows a microwave oven circuit according to an embodiment of the present invention.

Reference numeral 1 is a commercial power supply, 2 is a fuse, 3 is a door switch which is interlocked with opening and closing of a door, and 5 is a monitor switch which operates in a reverse operation of the door switch and blows the fuse when the door switch fails. 6 is a room light, 7 is a blower motor, 8 is a step-up transformer, magnetron, diode,
A high-frequency oscillation circuit composed of a capacitor, and 9a and 10a are relay contacts for energizing and interrupting the load.

Reference numeral 11 is a step-down transformer, 12 is a rectifying diode, and 13 is a smoothing capacitor, which forms a half-wave rectifying circuit. Reference numeral 15 is a regulator, which forms a power source of a microcomputer (hereinafter referred to as a microcomputer) 16.
The power sources of the relays 9 and 10 are not stable. Resistance 17,
Commercial power supply 1 with 20, transistor 18, diode 19
The signal synchronized with is input to the interrupt signal port of the microcomputer 16. 9b and 10b are relay contacts 9a and 10b, respectively.
It is the exciting coil of a. Reference numeral 21 is a surge absorbing diode, 22 is a surge absorbing and relay coil voltage limiting Zener diode, 23 and 26 are transistors, 24,
25, 27 and 28 are resistors.

Since the relay drive circuit power supply voltage E ₁ (V) does not pass through the regulator, it contains ripple components and is affected by the voltage fluctuation of the commercial power supply. However, the voltage E ₁ is larger than the rated voltage of the coil 10b, and the effective voltage of the relay coil 10b when the relay ON state is stable is the resistance 29
The relay coil 10b is configured to be supplied with a voltage from the rated value to the rated value or less.

When the relay 10 is off, the resistor 30,
The resistor 29 charges the capacitor 31 with a voltage of E ₁ (V), and the capacitor 30 has no voltage on the resistor 30 side.
A voltage of −E ₁ (V) is applied to the (V) (GND) and the resistor 29 side.

When the relay drive signal is output from the microcomputer 16, the transistor 26 is turned on. At that moment, the potential on the resistance 30 side of the capacitor 31 is about −E ₁ (V), so that the potential on the resistance 29 side of the capacitor 31 is originally about −−.
It becomes 2E ₁ (V).

However, since the generated voltage is limited by V _z due to the Zener voltage of the Zener diode 22, -V _z
Voltages above (V) are clamped.

The capacitor 31 is discharged through the resistor 29, and the potential on the resistor 29 side of the capacitor 31 eventually becomes a voltage divided by the relay coil 10b and the resistor 29. That is, as shown in FIG. 2, a voltage larger than the rated voltage is applied to the relay coil 10b immediately after the relay signal is output from the microcomputer 16, and only a voltage of the rated value to the rated value or less is applied in the steady state. Has become. The transistor 26, the resistors 29 and 30, and the capacitor 31 constitute a relay drive circuit.

By using such a relay drive circuit, a voltage larger than that in a stable state is applied to the relay coil 10b immediately after the relay ON signal is output from the microcomputer 16,
The operation time of the relay can be greatly shortened. The Zener voltage V is applied to the relay coil 10b at the maximum.
Commercial power supply 1 because only the power limited by _Z is applied.
Even if there is a change in the voltage, the effect on the voltage applied to the coil 10b is small and the effect on the variation in the operating time is small.

FIG. 3 shows (ratio of coil voltage to rated voltage of relay coil) vs. (ratio of operating time to rated) characteristic. When the exciting voltage of the relay coil increases, the operating time shortens, and the variation in operating time due to the individual difference of the relay decreases accordingly.

In a microwave oven or the like, in order to suppress an inrush current in a high frequency circuit, it is desirable to turn on a contact of a relay or the like in a phase in which a voltage change is 0. According to the present invention,
Even if there are variations in operating time due to individual differences in relays,
By applying a large applied voltage, the closing phase of the relay contact can be stabilized.

FIG. 4 is a circuit diagram of another embodiment.
In this embodiment, the regulator 15 is used to relay 9 and 10.
That the power source of the
Without using the surge absorbing diode 40
It differs from the above-described embodiment in that According to
As shown in FIG. 5, the relay drive circuit power supply voltage E ₁
(V) does not include a ripple component,
Immediately after the relay ON signal is output from the relay coil 10b
Is more than twice the voltage when stable
ing.

[0019]

According to the present invention, the operation time of the relay is shortened by applying a voltage larger than the rated voltage to the coil at the start of the application of the relay coil voltage. Therefore, the operation time of the relay can be reduced with a safe and simple circuit configuration. Can be suppressed, and the ON phase of the relay contact can be stabilized, so that the inrush current in the high frequency circuit can be suppressed stably.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram of a microwave oven of the present invention.

FIG. 2 is a relay coil voltage waveform time chart for explaining the operation of the embodiment of the present invention.

FIG. 3 is an explanatory diagram of correspondence between coil voltage and operating time.

FIG. 4 is a circuit configuration diagram of another embodiment of the microwave oven of the present invention.

FIG. 5 is a relay coil voltage waveform time chart for explaining the operation of another embodiment of the present invention.

[Explanation of symbols]

 10 relay 10b relay coil 26 transistor (relay drive circuit) 29 resistance (relay drive circuit) 30 resistance (relay drive circuit) 31 capacitor (relay drive circuit)

Claims (1)

[Claims] 1. A high-frequency heating apparatus having a relay for controlling heating means, wherein a coil of the relay is provided with a relay drive circuit for applying a voltage higher than a rated voltage of the coil only when starting voltage application. High frequency heating device.