JPS6385808A - Ac stabilized power supply unit - Google Patents

Abstract

PURPOSE:To reduce the size and weight of a device and to make the device flat by using a photocoupler instead of a feedback transformer. CONSTITUTION:The feedback transformer in a phase control type constant voltage power supply is replaced by an AC output detecting circuit 3. Namely AC output detecting circuit 3 is provided with the photocoupler 31 for detecting an AC output voltage generated between output terminals (a) and (b), the photocoupler 31 is constituted of a light emitting diode 32 and a phototransistor 33 and the light emitting diode 33 is electrically insulated from the transistors 33, 34. Consequently, the feedback transformer constituting an AC stabilizing power supply can be omitted and the device can be reduced at its size and weight. In addition, the device can be made flat.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a phase-controlled AC stabilized power supply device, and particularly to an AC stabilized power supply device that is compact and lightweight.

[Prior Art] A conventional phase control type AC stabilized power supply device includes a feedback element composed of a reactor at the phase control output end,
For example, it has a transformer, and the output signal of the feedback transformer is transmitted to the control system to stabilize the AC output.

[Problems to be Solved by the Invention] However, in such an AC stabilized power supply, especially in the case of a constant voltage power supply (CVR) that stabilizes the AC output voltage, this feedback transformer has a primary voltage of 100%.
Since the frequency is 50 or 60H2, the device is large, which is an obstacle to making the device smaller, lighter, or flat.

SUMMARY OF THE INVENTION In view of the above-mentioned problems with the conventional type, an object of the present invention is to make an AC stabilized power supply device smaller, lighter, or flatter.

[Means for Solving the Problems and Effects 1] In order to achieve the above object, the present invention is characterized in that a photocoupler is used instead of a feedback transformer.

In addition, general photocouplers output binary signals such as on/off or H/L, so the absolute value of the AC output cannot be directly transmitted, and the output of the photocoupler is directly transmitted to the AC output. When fed back as an output value, a large error occurs in the detected AC output value depending on the input voltage and thus the peak value of the phase control output.

Therefore, in one embodiment of the present invention, another photocoupler is provided to detect the input voltage, and the AC output detection value is corrected according to the input voltage.

[Effects of the Invention] According to the present invention configured as described above, it is possible to eliminate the feedback transformer, which is one of the large components constituting the AC stabilized power supply, so that the device can be made smaller and lighter. can. Furthermore, it is possible to flatten the device.

Examples] The present invention will be described in detail below using the drawings.

FIG. 1 shows the configuration of a phase controlled constant voltage power supply device according to an embodiment of the present invention. In the figure, 1 is an AC power supply, 2 is a triac which is a phase control element, and 3 is an AC output detection circuit which is a feature of the present invention.

Moreover, a and b are output terminals to which an AC voltage whose phase is controlled by the triac 2 is output. The circuit configuration of this device is completely the same as that of the conventional device except that the feedback transformer of the conventional phase-controlled constant voltage power supply device is replaced with the AC output detection circuit 3 described above.

The AC output detection circuit 3 includes a photocoupler 31 for detecting the AC output voltage generated between the output terminals a and b. The photocoupler 31 is a light emitting diode 32. ff
The light emitting diode 32 and the transistors 33 and 34 are electrically insulated. Here, as the photocoupler 31, a commercially available photocoupler in which a transistor 36 for inverting the output of the phototransistor 33 and the like are integrated into one module is used. 35 is a light emitting diode 3 which is a DC element.
2 is a diode bridge for operating as an AC element regardless of the polarity of the AC output voltage, 36 is a resistor for limiting the current flowing to the light emitting diode 32, and 37 is an operational amplifier. The operational amplifier 37 is connected as a voltage follower to receive the high impedance photocoupler output.

FIG. 2 shows the AC input voltage e in of the device of FIG.

AC output voltage eo and detection output voltage Vo of the detection circuit 3
FIG.

Next, the operation of the apparatus shown in FIG. 1 will be explained with reference to the waveform diagram shown in FIG.

In FIG. 1, a triac 2 outputs an AC voltage eO that is turned on and off in synchronization with an AC voltage e10 inputted from an AC power source 1 and whose phase is controlled.

This AC output voltage eO is supplied to a load (not shown) via output terminals a and b, and is also applied to a series circuit consisting of a resistor 36, a diode bridge 35, and a light emitting diode 32 of the AC output detection circuit 3.

Thereby, the light emitting diode 32 is energized and emits light while the AC voltage eO exceeds a predetermined threshold voltage every half cycle of the AC voltage eO. This [Jl voltage is determined by the ON voltage of the light emitting diode 32 and the diode bridge 35. Therefore, by connecting a resistor in parallel with the light emitting diode 32 or the diode bridge 35, or by connecting an element such as a Zener diode in series with the light emitting diode 32:! It can be divided into sections.

The light emitted from the light emitting diode 32 is incident on the phototransistor 33, and the phototransistor 33 is turned on while the light from the light emitting diode 32 is incident, and the collector becomes the "L" level. After being inverted to the "H11 level" by the "L" level signal transistor 34, it is output via the voltage follower 37 (VO). In other words, the detection output VO of the AC output detection circuit 3 represents the magnitude of the AC output voltage eo. The detection output vO is input to a control circuit (not shown). The control circuit compares the average voltage (DC value) of this output Vo with a predetermined reference voltage, generates an ignition pulse with a phase according to the error, and fires the triac 2.
supply to the gate. Thereby, the conduction angle of the triac 2 is controlled by negative feedback so that the AC voltage eO becomes a predetermined voltage corresponding to the reference voltage.

By the way, as mentioned above, the photocoupler 31 is turned on and off at a certain threshold voltage, and the detection output VO
is a square wave. Therefore, when simulating the above AC output voltage eo, which is a part of a sine wave, with this detection output ``0'' as it is, due to the nonlinearity of the detection output ``0'' versus the AC output voltage eO, especially when the input voltage changes from the rated voltage. Significant detection errors occur when there is a large variation. In other words, there is a problem that the output voltage fluctuation is large and the constant voltage characteristics are poor.

One means of solving this problem is to amplitude modulate the photocoupler output with a sine wave or full-wave rectified waveform that is in phase with the AC output voltage. This can be achieved by applying full-wave rectification (pulsating current) output before smoothing and stabilization as the photocoupler power supply VCC when rectifying AC power to obtain DC power for control circuits, etc. .

However, in general, in order to miniaturize equipment, DC power supplies for control circuits, etc. are isolated from AC power supplies using switching regulators or PC-DC converters, or are stepped down and stabilized, so DC power supplies for control circuits, etc. are isolated from AC power supplies. It is difficult to obtain a relatively low pulsating voltage.

FIG. 3 shows a further embodiment of the invention. The device shown in the figure is
In contrast to the one in FIG. 1, a circuit 5 for detecting input voltage ein,
By adding a correction circuit (not shown) that compares the output Vin of the circuit 5 and the output VO of the output voltage detection circuit 3 and corrects the output vO based on the comparison result, the above simulation error (detection error) to improve constant voltage characteristics.

In the correction circuit, the simulation accuracy (constant voltage characteristics) can be further improved by converting the effective values of the detection outputs Vin and VO into DC values (for example, average values) and then comparing them.

Such rms value (RMS)/direct current value (DC) conversion is
This can be easily implemented using an analog multiplier (eg NJM422: product number).

FIG. 4 shows an example of an effective value/DC value converter using a D/A converter. In the figure, reference numeral 11 denotes a clock pulse oscillator, which generates a clock pulse CPI of, for example, several kHz. 72 is an AND gate, 73 is a rising differential circuit, 74 is a falling differential circuit, 75 is a counter, 76 is a latch circuit, and 17 is a D/A converter.

Next, the operation of the circuit shown in FIG. 4 will be explained with reference to the waveforms of each part shown in FIG. First, the square wave human power vin (or Vo
) becomes H" level, input of the clock pulse CP2 to the counter 75 via the AND gate 12 is started, and at the rise of the rectangular wave input Vin, a pulse P[ is generated from the differentiating circuit 73, which is input to the counter 75. input to the clear terminal CL of the counter 75.
is instantaneously cleared and subsequently starts counting the clock pulses.

Next, when the rectangular wave input voltage ■in becomes "L''' level, the AND gate 72 turns off and prohibits the passage of the clock pulse CP1, and when the rectangular wave input voltage vin falls,
Pulse P[ is generated from the differentiating circuit 74 and the latch circuit 76
It is input to the store input terminal ST of. As a result, the latch circuit 76 takes in the counting output of the counter 75 at that time, and thereafter latches and outputs this counting output until the next pulse Pt is generated from the differentiating circuit 14. That is, the latch circuit outputs digital data representing the length of the rectangular wave input.

The D/A converter 77 converts this digital data into an analog value (for example, a DC voltage of 0 to 10 cm). This analog value is proportional to the length of the rectangular wave force Vin. In other words, since the amplitude of the rectangular wave is constant, this analog value is proportional to the effective value. That is, the circuit shown in FIG. 4 can convert the effective value of a rectangular wave signal into a DC voltage (average value).

The detection signals ■0 and Vin converted into DC voltages by this effective value/DC value conversion circuit 7 are, for example, divided into only Vin, and then subtracted from ■0 by a comparator (not shown), and then used as a corrected detection signal for the above-mentioned control. sent to the circuit.

[Other Examples] Note that the present invention is not limited to the above-mentioned embodiments, and can be implemented with appropriate modifications. Example (For example, in the above, an example in which an AC output voltage is stabilized has been described, but the present invention is also applicable to a case where an output current or power is stabilized.

Further, as the photocoupler mentioned above, a bidirectional light emitting diode as shown in FIG. 6 may be used. In this case the diode bridge can be removed. Furthermore, the light receiving element may be anything such as a photodiode, a photothyristor, or a photocell, as long as it can extract a signal using light.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of the main parts of a phase-controlled constant voltage power supply device according to an embodiment of the present invention, FIG. 2 is a voltage waveform diagram of each part of the device of FIG. 1, and FIG.
FIG. 6 is a circuit diagram of a main part of a phase-controlled constant voltage power supply device according to another embodiment of the present invention. 4 is a main circuit diagram showing a modification of the correction circuit in FIG. 3, FIG. 5 is a signal waveform diagram of each part of the circuit in FIG. 4, and FIG.
4 is a circuit diagram showing a modification of the photocoupler in FIG. 1 or 3. FIG. 1: AC power supply, 2: Phase control element, 3: AC output detection circuit, 31: Photocoupler, 32: Light emitting diode, 33
: Phototransistor, 5: AC input voltage detection circuit, 7
: Effective value/DC value conversion circuit, 71: Clock pulse oscillator, 72: AND gate, 75: Counter, 76: Latch circuit, 77: D/A converter. Figure 3 Figure 4

Claims (1)

[Scope of Claims] 1. A photovoltaic device comprising a phase control element that generates an AC output whose phase is controlled by an AC power source, a light emitting element energized by the AC output, and a light receiving element that detects light from the light emitting element. An AC stabilized power supply device comprising: a coupler; and a control circuit that performs negative feedback control of the conduction angle of the phase control element according to the output of the light receiving element. 2. The photocoupler responds to the voltage of the AC output and generates a first rectangular wave signal whose state is reversed between a period in which the voltage exceeds a predetermined first threshold voltage and a portion below the threshold voltage. The control circuit generates a detection signal representing the AC output voltage value from the first rectangular wave signal, and adjusts the conduction angle of the phase control element to make the detection signal match a predetermined value. Claim 1 which is a negative feedback control of
The AC stabilized power supply device described in . 3. The control circuit generates a second rectangular wave signal in response to the voltage of the AC power source, the state of which is inverted between a period in which the voltage exceeds a predetermined second threshold voltage and a portion below the threshold voltage. Claim 2, which comprises: a second photocoupler that generates the signal; and a correction circuit that creates the detection signal by correcting the first rectangular wave signal with the second rectangular wave signal. The AC stabilized power supply device described in . 4. The correction circuit converts the first rectangular wave signal into the second rectangular wave signal.
4. The AC stabilized power supply device according to claim 3, further comprising means for amplitude modulating a sine wave signal having an amplitude corresponding to the on/off duty ratio of the rectangular wave signal. 5. The light receiving element of the first photocoupler is a phototransistor whose emitter is grounded, and the amplitude modulation means applies a full-wave or half-wave rectified waveform of a sine wave to the collector of the phototransistor via a collector resistor. An alternating current stabilized power supply device according to claim 4. 6. The correction circuit includes an RMS/DC converter that converts the effective voltages of the first and second rectangular wave signals into first and second DC voltages, respectively, and converts the effective voltages of the first and second rectangular wave signals into first and second DC voltages, 4. The AC stabilized power supply device according to claim 3, wherein a DC voltage obtained by subtracting a voltage proportional to the DC voltage of No. 2 is output as the detection signal. 7. The AC stabilized power supply device according to claim 6, wherein the RMS/DC converter uses an analog multiplier. 8. The RMS/DC converter includes a clock pulse oscillator, a gate circuit that passes the clock pulse only while the rectangular wave signal is at "H" level, and counts the number of clock pulses that have passed through the gate circuit. The AC stabilizing device according to claim 6, which includes a counter, a latch circuit that latches the counted value, and a D/A converter that converts the digital output of the latch circuit into the DC voltage. power supply.