JPS60220891A - Electronic timer - Google Patents

Abstract

PURPOSE:To perform invariably precise timer clocking by discriminating on the frequency of a power source signal a specific time after a source voltage rises, and performing the timer clocking operation. CONSTITUTION:When the power source is turned on, the microcomputer 20 of a control part 10 counts clocks of the oscillation output of an oscillator 21 up to a specific number from the rising of the source voltage and counts the period of a frequency signal T based upon a commercial power source with the clocks a specific time later, i.e. when the source voltage becomes stable, thus deciding whether the power source frequency is 50 or 60Hz. Then, the signal T is counted by the computer 20 and the timer time which is set with a key 14 and displayed on a display device 12 varies, so that the rest time is displayed. Consequently, the electronic timer of cooking appliance, etc., provides invariably precise timer clocking.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an electronic timer used in home appliances such as cookers.

[Technical background of the invention]

Conventionally, some electronic timers of this kind are designed to first determine the power supply frequency based on a reference clock signal when the power is turned on, and to measure time by counting the determined power supply frequency.

[Problems with background technology]

By the way, in general, when chattering occurs when the power plug is inserted into an outlet, or when the generator rotation has not yet reached a sufficient speed, such as immediately after a power outage is restored,
The power frequency is in an unstable state. However, in the above-mentioned electronic timer, an error may occur in determining the power frequency, and an error may occur in the time measured.

[Purpose of the invention]

This invention was made in view of the above circumstances,
The purpose is to provide an electronic timer that can accurately determine the power supply frequency and thereby always perform accurate timekeeping.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

First, FIG. 1 shows an example of a control circuit for a cooking appliance, such as a microwave oven, according to the present invention.

In Fig. 1, 1 is a commercial AC power supply, and this power supply 1 includes a fuse 2, door switches 3 and 4, and a relay contact 1.
The temporary side coil 5a of the high voltage transformer 5 is connected through the coil 18 and the like in series. Secondary coil 5b of high voltage transformer 5
The anode and cathode of a magnetron 8, which is a high frequency generator, are connected through a rectifier circuit consisting of a high voltage capacitor 6 and a high voltage diode 7. The anode of the magnetron 8 is grounded, and the heater (cathode) is connected to the secondary coil 5C of the high voltage transformer 5.

A temporary coil 9a of a transformer 9 is connected to the power source 1 via the fuse 2, and a control section 1o incorporating an electronic timer of the present invention is connected to a secondary coil 9b of the transformer 9. A control relay 11, a display section 12, a key power section 13, and the like are connected to the control section 10.

Therefore, FIG. 2 shows the main parts of the control section 10 and the control section 10.
This is a concrete illustration of the surrounding area.

That is, in the control section 10, 20 is a microcomputer which is a main control section, 21 is an oscillator that generates a reference clock signal with a frequency of, for example, 400 KHz, and 22 is a reset signal generation circuit that generates a reset signal R. . This reset signal generation circuit 22 includes a resistor 23
An integrating circuit consisting of a transformer 9 and a capacitor 24.
By applying a DC voltage (2) obtained by rectifying the secondary side voltage of , a reset signal R is generated in response to the rise of the power supply voltage. Further, the microcomputer 20 is configured to receive the reset signal R and a frequency signal (pulse signal) (2) corresponding to the frequency of the power supply voltage. And microcomputer 2
0 is the relay control signal C1 display unit 1 for the relay 11
Segment signal S1 for display unit 12 and digit signal D1 for key input unit 14. D2, D3
, D4, respectively.

On the other hand, the display section 12 is, for example, a four-digit digital display formed by segmenting a plurality of light emitting diodes, and is provided on the operation panel (not shown) of the main body of the microwave oven. Press the numerical keys corresponding to ``O'' to ``9'', press 1゜...Ks, and press the strong output setting key 1 (a), the weak output setting key Kb, and the illumination start key 1 (c). It is provided on the operation panel similarly to the display section 12 described above.

Next, the operation in the above configuration will be explained.

Now, when a power plug (not shown) is inserted into an outlet to turn on the power 8i1, a voltage is generated on the secondary side of the transformer 9, and the control section 10 operates. That is, the microcomputer 20 is supplied with the frequency signal (2) corresponding to the power supply frequency, and the reference clock signal emitted from the oscillator 21 is taken into the microcomputer 20.

Furthermore, with the rise of the power supply voltage, a DC voltage V is generated, and a reset signal R (logic "1" signal) is generated from the reset signal generating circuit 22, which is supplied to the microcomputer 20.

After the microcomputer 20 initializes according to the reset signal R, the oscillator 2
A constant time t is measured by counting the reference clock signal from 1. In this case, the reference clock signal has a frequency of 40
Since it is 0 KHz, the count value is "'400"
The time is measured with 1 second.

After a certain period of time t has elapsed, the microcomputer 20 counts the reference clock signal in one period of the frequency signal T, and determines the power supply frequency based on the count value. In this case, the frequency of the reference clock signal is 400 -
Therefore, if the count value is approximately "8000", it is determined that the power supply frequency is 50 Hz, and if the count value is approximately "6600", the power supply frequency is determined to be 60 t.
It is determined that h.

In other words, when the power plug is inserted, the power frequency is unstable due to chattering, etc., and immediately after the power outage returns, there is a delay in the startup of the generator's rotational speed, so as shown in Figure 3, the power supply frequency is unstable. Since the frequency is in an unstable state, the power supply frequency is determined after a certain period of time that sufficiently covers these unstable periods.

However, when the cooking time is set in the key human power section 13,
The microcomputer 20 displays the set cooking time on the display section 12. and a heating chamber (not shown)
When the cooking start key 1 (c) of the key operator section 13 is turned on, the microcomputer 20 operates the relay 11 with the relay control signal C. When the relay 11 operates, the contact 11a closes. This causes the magnetron 8 to operate in oscillation. That is, high frequency waves are supplied into the heating chamber and cooking begins.

During cooking, the microcomputer 20 counts the frequency signal (2) and uses the count value and the frequency determination result to perform timekeeping. Then, the remaining cooking time based on this time measurement is sequentially displayed on the display section 12. Thereafter, when the preset cooking time has elapsed, the microcomputer 20 stops the operation of the relay 11, opens the contact 11a, and finishes the cooking. In addition, when it is necessary to perform time measurement immediately after initialization, the microcomputer 20 adds the time measured by counting the reference clock signal to the time measured by counting the frequency signal T.

In this way, the power supply frequency is determined after a certain period of time has elapsed since the rise of the power supply voltage, that is, after the power supply frequency has become stable, so that the power supply frequency can be accurately determined. Since timer timing is carried out by counting the power supply frequency based on this determination result, timekeeping errors do not occur and highly accurate timer timing can always be performed.

By the way, in this invention, even though there is a timekeeping function by counting the reference clock signal, the timer performs timekeeping by counting the power supply frequency. This is because when measuring time, a highly accurate oscillator 21 is required, resulting in an increase in cost. In other words, a timekeeping method based on counting the power supply frequency is more advantageous in that sufficiently high accuracy can be obtained without increasing costs.

In the above embodiment, application to a microwave oven has been described, but the present invention is not limited thereto, and can be similarly applied to other household IftII devices that require timekeeping.

C. Effects of the Invention] As described above, according to the present invention, it is possible to provide an electronic timer that can accurately determine the power supply frequency and thereby always perform accurate timekeeping.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a control circuit of a microwave oven according to the present invention, Fig. 2 is a block diagram specifically showing the main parts of Fig. 1 and an embodiment of the present invention, and Fig. 3 is a block diagram showing a power outage. FIG. 6 is a diagram showing changes in power supply frequency immediately after recovery. DESCRIPTION OF SYMBOLS 1... Commercial AC power supply, 20... Microcomputer (main control part), 21... Oscillator, 22... Reset signal generation circuit, ■... Frequency signal, C... Relay III signal Moon, S... segment signal, Dl,
D2, Dl. D4...Digital signal. Applicant's agent Patent attorney Takehiko Suzue Figure 1

Claims (1)

[Claims] It is characterized by comprising means for measuring a fixed time from the rise of the power supply voltage, means for determining the power supply frequency after measuring this fixed time, and means for performing timer timing by counting the power supply frequency based on the result of this determination. electronic timer.