JPH08122368A - Source voltage-detecting apparatus and load current--controlling apparatus - Google Patents

Abstract

PURPOSE: To provide a source voltage-detecting apparatus which can highly accurately measure the size of a source voltage in a simple constitution at low costs and provide a load current-controlling apparatus for controlling a load current based on the detected source voltage. CONSTITUTION: The zero cross timing of a commercial alternating input source voltage 1 is detected at a zero cross detection part 6, and the time when 110V is exceeded in a positive or negative half cycle is measured based on an output of a 110V detection part 5. A control part 7 detects the size of the source voltage based on the result from the parts 5, 6. Moreover, the control part 7 sets a controlling phase angle on the basis of the size of the source voltage and outputs the angle to a phase control part 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a commercial power supply voltage,
The present invention relates to a device for detecting the magnitude of a sine wave AC input power supply voltage and a load current control device for controlling a load current according to the detected power supply voltage.

[0002]

2. Description of the Related Art A general conventional apparatus for detecting a sine wave AC input power supply voltage is to reduce the input voltage to an appropriate voltage, and
A / D conversion is performed and then digital detection is performed, or a Zener diode or the like is used to detect whether or not the magnitude of the power supply voltage is a certain magnitude or more.

[0003]

However, the A / D
A device for digitally processing using a converter has a drawback that it is complicated and expensive due to the use of an A / D converter, and a simple structure using a Zener diode has a large power supply voltage. However, there is a drawback in that it cannot be accurately measured.

An object of the present invention is to provide a power supply voltage detecting device having a simple structure and capable of measuring the magnitude of the power supply voltage with high accuracy at low cost.

Another object of the present invention is to provide a load current control device for controlling the load current based on the power supply voltage detected as described above.

[0006]

SUMMARY OF THE INVENTION The present invention provides zero-cross timing detection means for detecting the zero-cross timing of a sine wave AC input power supply voltage, and the time during which the AC input power supply voltage exceeds a predetermined value within a half cycle from the zero-cross timing. Is provided, and the magnitude of the AC input power supply voltage is detected from this count value.

Further, the power supply voltage detecting device, the phase control means for controlling the phase of the load current, and the means for setting the control phase angle by the phase control means based on the count value are provided. .

Further, the apparatus further comprises frequency detecting means for detecting the frequency of the AC input power supply voltage, and the means for setting the control phase angle is means for setting the control phase angle based on the detected frequency. Is characterized by.

Further, the frequency detecting means is provided with means for counting between two adjacent zero-cross timings detected by the zero-cross timing detecting means, and the frequency is detected from the count value.

[0010]

In the present invention, when the zero-cross timing is detected, it is monitored whether or not the input power supply voltage exceeds the predetermined value from that time, and the counter starts counting when it exceeds the predetermined value and does not exceed the predetermined value. Calculate the count value up to the time. In this case, since the AC input power supply voltage is a commercial voltage, its waveform is a sine wave. Therefore, the count value increases as the power supply voltage increases. Therefore, the magnitude of the power supply voltage is detected based on this count value.

Further, by setting the control phase angle for controlling the load current based on the above count value, the output to the load can be made constant regardless of the fluctuation of the input power supply voltage. In addition, the power supply voltage frequency by domestic commercial AC is 5
0 Hz and 60 Hz, but since the count value changes depending on this frequency, the output can be controlled to a predetermined magnitude regardless of the frequency by also referring to this frequency when setting the control phase angle. .

The frequency can be easily known by counting between two adjacent zero-cross timings. Therefore, for example, if this operation is performed only once when the power is turned on, the power supply frequency can be immediately known, and hence the control phase angle is set with reference to this frequency.

[0013]

1 is a block diagram of a load current control device having a power supply voltage detection device according to the present invention.

An incandescent lamp 2 and a triac 3 as a load are connected to a commercial input power supply voltage 1, and the phase of the triac 3 is controlled by a phase controller 4. Further, the input power supply voltage 1 is connected to a 110V detection section 5 and a zero-cross detection section 6, and their outputs are guided to the control section 7. The 110V detection unit 5 detects a state when the instantaneous value of the voltage of the input power supply voltage 1 exceeds 110V, and the zero-cross detection unit 6 detects when the voltage value of the input power supply voltage 1 becomes 0V. . The control unit 7 uses the above 110
The control phase angle in the phase controller 4 is set based on the outputs from the V detector 5 and the zero-cross detector 6.

FIG. 2 is a diagram for explaining the principle of power supply voltage detection in the power supply voltage detection device. Since the input power supply voltage 1 is a sine wave, the waveform when the effective value voltage is 90V or 110V is as shown in the figure. This time,
If a threshold of 110 V is set and the time when this threshold of 110 V is exceeded during the positive half cycle is measured, as shown in the figure, the time t1 when the effective value is 90 V is obtained.
In comparison with the above, the length of time t2 when the effective value is 110 V becomes longer. The relationship between the lengths of t1 and t2 and the effective voltage is always constant regardless of the magnitude of the load current. Therefore, if these relationships are stored in a table in advance, the effective value voltage of the input power supply voltage can be known by measuring the time t (t1 or t2). Further, since the length of the time t also depends on the frequency of the input power supply voltage, if the table is made to correspond to the frequency in advance, even if the frequency changes, the correct effective value voltage can be known only by switching the table. be able to.

FIG. 3 is a block diagram of a memory provided in the control unit 7. The counter includes a frequency counter and a 110V counter. The frequency counter is used to measure the frequency of the input power supply voltage 1 when the power is turned on. That is, the counter is started when the zero-cross detector 6 detects the zero-cross, and stopped when the next zero-cross is detected. At this time, the count value of the frequency counter and the frequency of the power supply voltage correspond to each other. Therefore, if the relationship between the count value and the frequency of the power supply voltage is stored in the memory in advance, this value immediately after the power is turned on can be obtained. The frequency of the power supply voltage can be known by looking at the count value of the frequency counter. The frequency thus detected is set in the frequency storage area M3. 11 in area M2
The 0V counter counts while the 110V detection unit 5 detects the instantaneous value 110V. Therefore, t (t
The time of 1, t2) is counted. The 50 Hz table of the area M4 is a trigger position table referred to when the frequency set in the area M3 is 50 Hz. This table outputs the trigger position of the triac 3, that is, the control phase angle according to the count value counted by the 110V counter. As the count value of the 110V counter increases, the effective value of the input power supply voltage increases. It is set to output a phase angle in which the output to the load becomes smaller as it becomes. Area M
5 stores the trigger position table referred to when the frequency stored in the area M3 is 60 Hz.

As described above, the control unit 7 sets the control phase angle based on the frequency of the power supply voltage and the length of the time t exceeding 110 V, and is independent of the frequency and the length of the time t. Is controlled, so that the output is kept constant even if the power supply voltage fluctuates.

4 and 5 are flow charts showing the specific operation of the control section 7.

FIG. 4 shows an operation performed once when the power of the apparatus is turned on and the zero-cross detector 6 detects a zero-cross when the power supply voltage changes from negative to positive. That is, at the zero-cross detection timing of changing from negative to positive, the operation of clearing the frequency counter and counting up the frequency counter is repeated until the zero-cross detecting unit 6 next detects a zero-cross changing from positive to negative. That is, the time T shown in FIG. 2 is counted by the frequency counter. Since this time T corresponds to the frequency of the input power supply voltage, this correspondence relationship is stored in advance in a memory (not shown), and the zero-cross timing is obtained when the power supply voltage switches from positive to negative. At time T
The frequency can be known based on. Then, this frequency is stored in the area M3.

The above operation is performed 1 immediately after the power is turned on.
Only once, the frequency of the detected power supply voltage is stored, and the process ends.

Next, the operation when the waveform is measured and the trigger control is performed will be described. FIG. 5 is a flowchart showing the operation at this time.

FIG. 6 shows a timing chart. As shown in FIG. 6, in this embodiment, waveform measurement is performed in the positive half cycle, and trigger control is performed in the negative half cycle. In the second and subsequent cycles, trigger control is performed even in the positive cycle.

The waveform measurement starts when the zero-cross detector 6 detects a zero-cross when the power supply voltage switches from negative to positive. That is, the waveform measurement starts when the power supply voltage becomes a positive half cycle. First, 11
Clear the 0V counter. And the instantaneous value is 110V
The time t when it is above is measured. This measurement is performed during the period until the zero-cross detector 6 detects the zero-cross when the power supply voltage is switched from positive to negative. That is, the time t at which the instantaneous value exceeds 110V in a positive half cycle is measured by the 110V counter. Then, this value is applied to the area M4 or the area M5 to obtain the control phase angle. As shown in FIG. 4, since the frequency of the power supply voltage is stored in the area M3 immediately after the power is turned on, whether to refer to the table of the area M4 or the table of the area M5 is determined by referring to this frequency. In each of the tables M4 and M5, the triac trigger position (control phase angle) corresponding to the measurement value of the 110V counter is stored, and the trigger position shifts in the time axis direction as the measurement value increases. ing. Therefore, the triac conduction angle increases as the input voltage increases, and the output is controlled to be constant even if the input voltage varies.

With the above operation, the power supply voltage can be easily and accurately known without using an A / D converter and the like, and the output to the load can be constantly controlled regardless of the fluctuation of the power supply voltage. You can

FIG. 7 shows a specific circuit diagram of the load current control device shown in FIG.

In the figure, 10 is AC100V, 50
It is a commercial AC power supply voltage of / 60 HZ, and four incandescent bulbs 11 are connected in parallel as incandescent light bulbs for loads. The incandescent bulb 11 is connected to a current transformer T1 as current-voltage converting means and triacs Q1 and Q2. IC
Reference numeral 3 denotes a microcomputer, b, c, d are input terminals, and a is an output terminal. The phase control signal is output to the output terminal a. This signal is
It is converted into a current by the transistor Q5 and drives the triac Q2 for phase control. Zener diode D
1, the resistance R1 and the transistor Q4 are instantaneous value 110V
Is detected, and when this 110V is detected, the transistor IC
The detection signal is led to the input terminal b of 3. This part is 1 in Figure 1
It corresponds to the 10V detection unit 5.

The resistor R8 and the transistor Q3 detect the zero-cross timing. The output is led to the input terminal c of the IC3. The input terminal c falls from "H" to "L" at the zero-cross timing when the power supply voltage changes from negative to positive, and from "L" to "H" at the zero-cross timing when the power supply voltage changes from positive to negative. "Stand up." The resistor R8 and the transistor Q3 correspond to the zero-cross detector 6 in FIG.

The voltage stepped down by the current transformer T1 is half-wave rectified by the diode D3 and the resistor R2.
IC2 that constitutes a comparator by being appropriately divided by R3
Input to the inverting input terminal of. The input power supply voltage is half-wave rectified by the diode D2, and the resistors R4, R5 and
The voltage is divided by R6 and input to the non-inverting input terminal of IC2.
In the IC2, when the input power supply voltage is a positive half cycle, the voltage divided by the resistors R4 to R6 is used as a reference voltage, and this reference voltage is compared with the voltage obtained by the current transformer T1. When the voltage is higher than the voltage detected by the transformer T1, "H" is output because a normal current is flowing in the load, and when it is opposite, "L" is output because an overcurrent is flowing. Input terminal d of IC3
Since its output is input to the IC3, the IC3 detects the overload condition by looking at the level. In this embodiment, by also including this overcurrent detection unit, the gate control signal output to the output terminal a is controlled so that the incandescent bulb 11 is controlled to perform half-wave lighting when an overload is detected. There is.

In the above embodiment, the time over 110 V is measured in the positive half cycle, but the time over -110 V may be measured in the negative half cycle. Also, the threshold is not limited to 110V,
An appropriate value can be set by experiment or the like.

[0030]

According to the present invention, the magnitude of the commercial AC input power supply voltage can be detected easily and accurately without complicating the circuit configuration. In addition, the power supply voltage can be accurately detected even if the frequency changes, and when the load current is phase-controlled, the output to the load is output by performing phase control based on the power supply voltage detected as described above. There is an advantage that it can be made constant regardless of fluctuations.

[Brief description of drawings]

FIG. 1 is a block diagram of a load current control device that is an embodiment of the present invention.

FIG. 2 is a diagram for explaining the principle of the power supply voltage detection device according to the present invention.

FIG. 3 is a block diagram of a memory of the load current control device shown in FIG.

FIG. 4 is a flowchart showing an operation executed only once when the power is turned on.

FIG. 5 is a flowchart showing an operation when performing waveform measurement and phase control.

FIG. 6 is a timing chart during waveform measurement and phase control.

FIG. 7 is a diagram showing a specific circuit example of the load current control device.

[Explanation of symbols]

 1-Commercial AC power supply voltage 2-Incandescent bulb 3-Triac 4-Phase control unit 5-110V detection unit 6-Zero cross detection unit 7-Control unit

Claims (4)

[Claims] 1. A zero-cross timing detecting means for detecting a zero-cross timing of a sine wave AC input power supply voltage, and a means for counting a time during which the AC input power supply voltage exceeds a predetermined value within a half cycle from the zero-cross timing. A power supply voltage detection device characterized by detecting the magnitude of an AC input power supply voltage from this count value. 2. A load comprising a power supply voltage detecting device according to claim 1, phase control means for phase controlling a load current, and means for setting a control phase angle by the phase control means based on the count value. Current control device. 3. The frequency detecting means for detecting the frequency of the AC input power supply voltage according to claim 2, wherein the means for setting the control phase angle further sets the control phase angle based on the detected frequency. A load current control device comprising: 4. The frequency detecting means according to claim 3, further comprising means for counting between two adjacent zero-cross timings detected by the zero-cross timing detecting means, and detecting the frequency from the count value. Load current control device.