JPH07122646B2 - Frequency detector - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a frequency detection device used in equipment having a motor, a solenoid valve, a heater, a timer, etc. that operate in synchronization with an AC power supply (hereinafter referred to as an AC power supply). is there.

2. Description of the Related Art Generally, a motor whose phase is controlled by an AC power supply and a timer which counts time have a difference in the number of revolutions of the motor and a time unit counted by the timer depending on whether the AC power supply is 50 Hz or 60 Hz. Therefore, a frequency detection device for detecting the frequency of the AC power source is naturally required to correct the difference so that the difference between them does not occur.

The conventional frequency detecting device will be described below.

As shown in FIG. 5, the frequency detecting device has an input section 1 for inputting a zero volt switching pulse synchronized with an AC power source and a timer section 2 as a timer means for measuring time t2, t3, t4 (t2 <t3 <t4). And a determination unit 3'as a determination unit for determining the frequency based on the time keeping state of the timer unit 2 when the zero volt switching pulse is input from the input unit 1 (hereinafter referred to as a microcomputer) 6 '. It is composed of. The microcomputer 6'is combined with a pulse generating circuit 8 which outputs a zero volt switching pulse to the microcomputer 6'by an AC power source 7 as shown in FIG.

The operation of the above configuration will be described below.

When the voltage V1 of the AC power supply 7 (Fig. 7 (a)) is in a positive cycle, the transistor Q1 to which the base current I1 is supplied is turned on (see Fig. 7).
(B)) Also, since the transistor Q2 to which the base current I2 is supplied is turned on during the negative cycle (Fig. 7 (d)), the base current I3 of the transistor Q3 is the AC power supply 7 whose voltage V1 is near zero volt. Transistor Q3 because it is always supplied except
A zero volt switching pulse as shown by V2 (Fig. 7 (e)) is output from the collector of the above, and the zero volt switching pulse is supplied to the input section 1 of the microcomputer 6 '.

The determination unit 3 ′ of the microcomputer 6 ′ receives the pulse P1 via the input unit 1.
When it senses, the timer section 2'starts counting the time at the same time as setting the T2 flag. When the timer unit 2 ′ measures the time t2 from the start of counting, it outputs an interrupt signal to the judging unit 3 ′, and the judging unit 3 ′ receives the interrupt signal.
Change T2 flag to T3 flag. When the timer unit 2'counts time t3 from the start of counting, an interrupt signal is output to the determination unit 3'to change the T3 flag T4 flag of the determination unit 3 '. When a pulse is input while the timer unit 2'is operating, the judging unit 3'sees the timer unit 2'by checking the flag state (T2, T3 or T4) of the judging unit 3 '.
Can know the time zone that is counting.

Next, the method of determining the frequency of the AC power supply 7 by the microcomputer 6'will be described in detail.

In FIG. 8, the determination unit 3'of the present apparatus uses the first pulse P1.
When T2 is detected, the T2 flag is set and at the same time, the timer unit 2'starts counting the time, and the frequency detecting device (microcomputer 6 ') enters the operating state (frequency detecting operating state). At times t2, t3, and t4 measured by the timer unit 2 '
If T2 = t2, T3 = t3-t2, and T4 = t4-t3, the time T2 is 7.
5 m sec, time T3 and time T4 are set to 1.5 m sec respectively. The period of the output pulse V2 of the pulse generation circuit 8 shown in FIG. 7 (e) is 10 msec at 50 Hz and 8.33 ms at 60 Hz.
Since it becomes ec, the next pulse P2 has a timekeeping state of the timer unit 2 ′ between time t2 and time t3 at 60 Hz, and has a timekeeping state of the timer unit 2 ′ between time t3 and time t4 at 50 Hz. . As a result, the frequency of the AC power supply 7 is 50Hz or 60Hz
I was making a decision.

If the pulse P2 is input to the determination unit 3'at a time point outside this range, it is determined to be abnormal and detection is performed again. The frequency detection range at the set values of the times T2, T3 and T4 of the timer unit 2'has the following values.

50Hz 47.6 to 55.0Hz 60Hz 55.0 to 66.7Hz By the way, the above frequency detection method is 10.0msec (50Hz
Or a relatively large error range of 1.5 msec with respect to the detection cycle of 8.33 msec (at 60 Hz). It has a very important meaning when considering the environment where consumer electronic devices are placed. That is, it can be said that generally, the environment in which consumer electronic appliances are placed is susceptible to electrical stress such as noise, strong electric field, and power supply voltage fluctuation in addition to mechanical stress such as temperature, humidity, and vibration. Under these circumstances, it is very difficult for the pulse generating circuit 8 described above to always maintain a stable waveform under all conditions.

For example, as shown in FIG. 9 (a), the threshold voltage VTH of zero volt switching changes depending on the temperature characteristics of the pulse generating circuit 8 and the pulse interval fluctuates several msec back and forth due to fluctuations in the power supply load and the like. This can easily occur (Fig. 9 (b)).

Therefore, by setting the error range in advance in consideration of the fluctuation of the pulse interval, it was configured so that the determination of 50/60 Hz could be performed stably.

Further, in order to improve the reliability of frequency detection, the frequency determination operation may be repeated a plurality of times.

However, if the electrical stress further escalates and the voltage V2 of the AC power supply 7 begins to be distorted as described above, the disturbance of the pulse generated from the pulse generation circuit 8 will be less than the fluctuation of the pulse interval. The length of one pulse width also changes.
When the pulse width becomes long, the determination unit 3'may check the pulse P1 at the leading edge of one pulse and then erroneously recognize the tail of the pulse as the pulse P2.

The cause of these electrical stresses is that in recent years clean energy has spread to electric heaters, air conditioners, etc., which have large-capacity electrical loads, and in terms of housing conditions, many apartments such as condominiums are common. It's coming.
Considering the power supply wiring of an apartment house, if the power supply lines 10 are wired independently in each room 9 as shown in FIG. 10 (a), it is very inefficient and the number of lines increases. It is usual to take a structure that branches off from a single wiring 10 'as shown in FIG. With such a configuration, the power supply impedance increases as the distance to the terminal room increases, and this phenomenon is extremely prominent if it becomes a large apartment house with dozens or hundreds of rooms in one building. come. Therefore, if the load is almost a sine wave with a small load, the power supply waveform will also be a distorted power supply waveform as shown in Fig. 10 (b) when the large-capacity electric equipment is often used in winter and summer.
That is, as shown in FIG. 9 (b), the zero-volt switching pulse V2 has an oscillation waveform corresponding to the waveform distortion.

When such a waveform is generated, it means that the intervals between the respective pulses measure the first and second pulse widths or the second and third pulse widths. If the method described in the conventional technology is adopted, the abnormality judgment is repeated near zero volt switching, and only the interval between the last pulse of the oscillating pulse group and the first pulse of the next cycle can be measured normally only once. Becomes As described at the end of the conventional technology, if the judgment operation for improving reliability is repeated multiple times, it will not be possible to detect a constant frequency continuously, and the power supply frequency cannot be determined. Had the problem of becoming.

The present invention solves the above-described problems and provides a frequency detection device capable of performing stable power supply frequency detection even when the power supply waveform is in an oscillating state near zero volts due to wiring impedance or the like.

Means for Solving the Problems In order to solve the above problems, the frequency detection device of the present invention,
A timer means that starts by receiving the pulse output of a pulse generation circuit that generates a signal synchronized with the power supply frequency and that counts time t1, t2t3't4 (t1 <t2 <t3 <t4) from the start time. When the pulse output is detected from the pulse generating circuit from the start to time t1, it is ignored, and when the pulse output is detected from the pulse generating circuit from time t1 to time t2 or after time t4, the timer means is initialized. If the pulse output is detected from the pulse generation circuit from time t2 to time t3, the power supply frequency is determined to be 60 Hz, and if the pulse output from the pulse generation circuit is detected from time t3 to time t4, the power supply frequency is changed. It is composed of a determination means for determining 50 Hz.

Operation With the above configuration, when the pulse output is received from the pulse generating circuit, the timer means is set to time t1, t2, t3, t4 (t1 <t2 <t3 <t.
4) Start timing. The determination means restarts the timer state that detects the pulse output from the initial state between the time t1 and the time t2 or after the time t4 elapses, and when the pulse output is detected between the time t2 and the time t3, the frequency of the AC power supply becomes 60 Hz. Judgment, AC is detected when pulse output is detected between time t3 and time t4.
Judge that the power supply frequency is 50Hz.

Example Hereinafter, a frequency detection device showing an example of the present invention will be described with reference to the drawings.

The same components as those of the conventional example are designated by the same reference numerals, and detailed description thereof will be omitted.

In FIG. 1, the frequency detection device has an input unit 1 for inputting a zero volt switching pulse, and times t1, t2, t3, t4.
A timer unit 2 as a timer unit for measuring (t1 <t2 <t3 <t4), and a determination unit 3 and an input unit 1 as a determination unit for determining the frequency based on the timekeeping state of the timer unit 2 at the time of inputting a zero volt switching pulse. It is composed of a switch control unit 5 for controlling a switch 4 for turning ON / OFF between the determination units 3, and in the present embodiment, each of these components is integrated as a microcomputer 6. And the microcomputer 6 is the second
As shown in the figure, an AC power supply 7 is combined with a pulse generation circuit 8 similar to the conventional example which outputs a zero volt switching pulse to the input unit 1 of the microcomputer 6. The operation of the pulse generation circuit 8 for producing the zero-cross switching pulse V2 (see FIG. 7 (e)) from the AC power supply 7 is exactly the same as the conventional example.

Next, the operation of the above configuration will be described.

In FIG. 3, the determination unit 3 of the present apparatus detects the first pulse P1 and, at the same time, causes the timer unit 2 to detect time t1, t2, t3, t4 (t1, <
Start the timing of t2 <t3 <t4). Where T1 = t1,
When T2 = t2, T3 = t3-t2, T4 = t4-t3, the time values of timer section 2 are set to 1msec for T1, 7.5msec for T2, and 1.5msec for T3 and T4 respectively. . The output pulse cycle of the pulse generator 8 shown in Fig. 2 is 10msec60H at 50Hz.
At z, it is 8.33 msec, so the pulse P2 following the pulse P2 is 60 Hz, and the timekeeping state of the timer unit 2 is at time t2 and time.
At 50 Hz during t3, the timekeeping state of the timer unit 2 should be between time t3 and time t4, and it can be determined whether the frequency of the AC power supply 7 is 50 Hz or 60 Hz.

Further, the determination unit 3 is only available while the timer unit 2 is counting the time T1 (time t1) after the pulse P1 is input to the determination unit 3.
Since the switch 4 is turned off via the switch controller 5, the pulse P2 is not detected. Further, if the timekeeping state of the timer unit 2 is abnormal between the time t1 and the time t2 or after the time t4 elapses, it is determined to be abnormal, and the newly detected pulse is set as P1, and the frequency detection operation is performed again.

Considering the difference between the case where the pulse voltage is generated during the time t1 of the timer unit 2 and the case where the pulse voltage is generated between the time t1 and the time t2, first, when there is no hardware failure, There is a possibility that the pulse voltage will be generated during the time t1 of 2 in the case as described in the conventional example, that is, the change of the waveform of the AC power source 7 may cause the zero-volt switch pulse to have an oscillation waveform. It is considered unlikely that a pulse will be generated after the subsequent voltage rises unless there is a great deal.

A specific waveform is shown in FIG. 4 for explanation. If V1 is the waveform of the AC power supply 7 and V2 is a zero volt switching pulse, the deviations TM1 and TM2 from zero volt are determined by the threshold levels VTH1 and VTH2 of the circuit shown in FIG. 2 and the cycle T of one cycle.

Now, assuming that VTH1 and VTH2 are 1.5V, TM1 and TM2 can be calculated by the following equations.

50Hz: TMI = 16.9μsec 60Hz: TMI = 14.1μsec The time t1 of the timer section 2 ends when the value of TM is subtracted from the set value of T1 from the zero volt point of the AC power supply 7. , If it is T1 ', then 50Hz: T1' = 0.983m sec 60Hz: T1 '= 0.986m sec, and if the AC voltage at this point is VAC (T1), then VAC (T1) = VAC × × SIN (T1 '/ T) x 2π) At 50Hz: VAC (T1) = 81.6V At 60Hz: VAC (T1) = 95.5V. However, VTH = VTH1 = VTH2, TM = TM1 = TM
2 That is, in this embodiment, 81.6V or 95.5V is set as a boundary between the zero-volt region where the output AC power supply 7 of the pulse generating circuit 8 shown in FIG.

This setting actually anticipates that a pulse may occur earlier due to variations in circuit constants, fluctuations in the power supply voltage 7, distortions in the power supply waveform, and the like.

Therefore, even if the pulse width generated from the pulse generation circuit 8 fluctuates due to fluctuations in the power supply voltage 7 or the like, one pulse will not be erroneously recognized as two pulse waves.
The frequency of the power supply voltage 7 can be accurately detected.

In addition, the frequency determination operation can be performed more accurately in the configuration in which the frequency determination operation is performed a plurality of times.

EFFECTS OF THE INVENTION As is clear from the above description of the embodiments, the frequency detecting device of the present invention is capable of detecting a stable power supply waveform even if the power supply waveform is in an oscillation state near zero volts due to the influence of wiring impedance or the like. An extremely effective power supply frequency detection device can be provided.

[Brief description of drawings]

FIG. 1 is a block diagram of a frequency detecting device showing an embodiment of the present invention, FIG. 2 is a circuit diagram showing a circuit including the same, FIG. 3 is a time chart in the circuit, and FIG. 5 is a detailed waveform diagram, FIG. 5 is a configuration diagram of a conventional frequency detecting device, FIG. 6 is a circuit diagram including the same, FIG. 7 is a waveform diagram of a pulse generating circuit, and FIG. 8 is a circuit diagram of FIG. Time charts, FIGS. 9 (a) and 9 (b) are waveform diagrams of an alternating current and a synchronous pulse of the alternating current when subjected to electrical stress,
FIGS. 10 (a) and 10 (b) show indoor wiring diagrams of the power supply line in an apartment house or the like. 1 ... Input section, 2 ... Timer section, 3 ... Judgment section, 4 ...
Switches, 5 ... Switch control section.

Claims (1)

[Claims] 1. Starting with receiving a pulse output of a pulse generating circuit that generates a pulse signal synchronized with a power supply frequency, and integrating from the start time, times t1, t2, t3, t4
(T1 <t2 <t3 <t4) timer means, and ignores the pulse output from the pulse generation circuit when it detects the pulse output from the start to time t1, and ignores the pulse output from time t1 to time t2 or time t4 When the pulse generation circuit later detects a pulse output, the timer means and the initial state are restarted,
When the pulse output from the pulse generation circuit is sensed between time t2 and time t3, the power supply frequency is determined to be 60 Hz,
A frequency detecting device comprising: a determining unit that determines the power supply frequency to be 50 Hz when a pulse output is sensed from the pulse generating circuit from t3 to time t4.