JPH0221603B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an AC constant voltage power supply device.

[Conventional technology]

Generally, AC constant voltage power supplies are used in various fields. For example, in an electrophotographic copying machine,
While research is progressing on increasing the sensitivity of photoreceptors, there is a growing need for stabilization of the light output of exposure light sources, and a highly accurate AC constant voltage power supply is required in this field as well. ing.

In response to such demands, an AC constant voltage power supply device having the configuration shown in FIG. 1, for example, has been known. That is,
A load 3, such as a halogen incandescent light bulb for exposing an original, is connected to an AC power source 1 via a bidirectional semiconductor switching element 2, which is a bidirectional semiconductor switching element. And the AC power supply 1 has a power transformer 11
A full-wave rectifier 4 is connected through the full-wave rectifier 1, and a series circuit of a resistor 5 and a constant voltage diode 6 is connected between the positive output terminal a and the negative output terminal b of the full-wave rectifier 4. A control circuit 7 for controlling the conduction phase of the bidirectional thyristor 2 is connected to both ends of the constant voltage diode 6. This control circuit 7 includes a series circuit of a transistor 8 and a capacitor 9, and a resistor 10 and a resistor 11 connected to both ends of the voltage regulator diode 6.
Connect the series circuits of the capacitors 9 and 9.
A series circuit consisting of a PUT (programmable unidirectional transistor) 12 and the primary coil of a pulse transformer 13 is connected to both ends of the PUT1.
The gate of PUT 2 is connected to the connection point of the resistor 10 and the resistor 11, and the anode of PUT 12 is connected to the resistor 12.
Each time the voltage across the capacitor 9 exceeds the gate voltage of the PUT 12 determined by the resistors 10 and 11, the PUT 12 becomes conductive and generates a pulse. A trigger pulse is applied to the gate of the bidirectional thyristor 2 via the transformer 13.

On the other hand, a voltage detection circuit 14 is connected to the load 3. This voltage detection circuit 14 connects the primary coil of a load voltage detection transformer 15 in parallel to the load 3, connects the input terminals of a full-wave rectifier 16 to both ends of the secondary coil of the load voltage detection transformer 15,
A series circuit of a resistor 17 and a resistor 18 is connected between the positive output terminal c and the negative output terminal d of the full-wave rectifier 16, and the negative output terminal d is connected to the negative output terminal b of the full-wave rectifier 4. A capacitor 19 is connected across the resistor 18, and this capacitor 19
A series circuit of a resistor 20 and a capacitor 21 is connected to both ends of the capacitor 21, and a detection voltage corresponding to the voltage across the load 3 is generated across the capacitor 21.

An error amplifier 22 is connected between the connection point e between the resistor 20 and the capacitor 21 and the negative output terminal d of the full-wave rectifier 16. This error amplifier 22 connects the base of one transistor 24 to the connection point e between the resistor 20 and the capacitor 21 via a resistor 23, and connects the emitter of this transistor 24 to the emitter of the other transistor 25. The emitter of the transistor 24 is connected to the negative output terminal d of the full-wave rectifier 16 through the resistor 26, and the negative terminal of the starting DC power supply 27 is connected to the negative output terminal d, and the collector of the transistor 24 is connected to the negative output terminal d of the full-wave rectifier 16 through the resistor 26. The starting DC power supply 27 via 28
The base of the transistor 24 is connected to the collector of the transistor 24 via a resistor 29 and a capacitor 30, and the collector of the transistor 25 is connected to the starting DC power supply 2.
The base of the transistor 25 is connected to the movable element of the potentiometer 31 connected between both terminals of the starting DC power supply 27, and the collector of the transistor 24 is connected to the positive side terminal of the transistor 24 through the resistor 32. The capacitor 9 is connected to the base of the transistor 8, and the negative terminal of the startup DC power supply 27 is connected to the base of the transistor 8.
The transistor 2 is connected to the connection point of the pulse transformer 13 by the potentiometer 31.
5 is used as a reference voltage, this reference voltage is compared with the base voltage of the transistor 24 corresponding to the detection voltage generated across the capacitor 21, and the voltage generated at the collector of the transistor 24, that is, at the Q point, according to this difference. The error output is applied to the base of the transistor 8 via a resistor 32.

With such a configuration, the error output of the error amplifier 22 causes the transistor 8 in the control circuit 7 to
By controlling the base voltage of the capacitor 9 and controlling the dv/dt of the voltage across the capacitor 9, the generation phase of the trigger pulse to the gate of the bidirectional thyristor 2 is controlled, and the voltage across the load 3 is made constant. That's what I do. In the figure, 33 is a noise filter capacitor, 34 and 35 are capacitors and inductors that constitute the noise filter, and 36 and 3 are capacitors.
7 is a capacitor and a resistor that constitute a surge absorption circuit.

[Problem to be solved by the invention]

However, according to such a configuration, since the load voltage detection transformer 15 is used to detect the load voltage of the power transformer 111 and the load 3, the entire device becomes large and heavy, and the transformer is expensive.
The disadvantage is that the manufacturing cost is high.

As a result of intensive research based on the above circumstances, the present inventor provided a series circuit of a first rectifying element and a second rectifying element so that the anode sides are connected to both ends of the load, and A series circuit of a reverse blocking 3-terminal thyristor and a resistor is inserted between the connection point between the rectifying element and the second rectifying element and the output terminal of the full-wave rectifier connected to the power supply. The present inventors have discovered that it is possible to detect the voltage across a load and a voltage close to the voltage across the load by making it conductive in synchronization with a bidirectional semiconductor switching element, and have completed the present invention.

The present invention is capable of stabilizing the voltage across the load reliably, detecting the voltage across the load without using a transformer, and is small, lightweight, and low in manufacturing cost, and does not require a power transformer. The purpose is to provide an AC constant voltage power supply device.

[Means to solve the problem]

The present invention is characterized by an AC power supply, a load supplied with power from the AC power supply, a bidirectional semiconductor switching element inserted between the load and the AC power supply, and an input terminal thereof. A full-wave rectifier connected to the AC power supply, a control circuit for controlling the conduction phase of the semiconductor control switching element connected between the output terminals of the full-wave rectifier, and an anode side connected to both ends of the load, respectively. a series circuit of a first rectifying element and a second rectifying element,
and a voltage comprising a series circuit of a semiconductor switching element and a voltage detection resistor inserted between the connection point of the first rectifying element and the second rectifying element and the output terminal of the full-wave rectifier. The control circuit comprises a detection circuit, and an error amplifier that receives a detection voltage obtained at the voltage detection resistor and generates an error output according to a difference between the detection voltage and a preset reference voltage. , the conduction phases of the bidirectional semiconductor switching device and the semiconductor switching device are synchronously controlled by the error output from the error amplifier.

〔Example〕

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

A circuit diagram of an embodiment of the present invention is shown in FIG. Components that are the same as those in FIG. 1 are designated by the same reference numerals.
In this example, a load 3 such as a halogen incandescent lamp for exposing originals is connected to the AC power source 1 via a bidirectional semiconductor switching element, such as a bidirectional thyristor 2, and the AC power source 1 is connected to, for example, four diodes D1. , D2, D3, and D4, and a series circuit of a resistor 5 and a constant voltage diode 6 is connected between the positive output terminal a and the negative output terminal b of the full-wave rectifier 4. A series circuit of a diode 41 and a capacitor 42 and a control circuit 7 for controlling the conduction phase of the bidirectional thyristor 2 are connected to both ends of the constant voltage diode 6.

This control circuit 7 has a series circuit of a resistor 43, a transistor 8, and a capacitor 9 connected to both ends of the constant voltage diode 6, and a series circuit of a resistor 10, a diode 44, and a resistor 11, and a PUT 12 connected to both ends of the capacitor 9. Connect the series circuit of the primary coil of the pulse transformer 13, and connect this PUT12
The gate of PUT12 is connected to the connection point of diode 44 and resistor 11, and the anode of PUT12 is connected to resistor 12.
1 to the positive output terminal a of the full-wave rectifier 4, and the base of the transistor 8 is connected to the diode 4.
5 to the connection point between the resistor 10 and the diode 44.

On the other hand, a series circuit of a first rectifying element such as a diode 46 and a second rectifying element such as a diode 47 is provided at both ends of the load 3 so that the respective anode sides are connected to each of the two ends. A series circuit consisting of a resistor 48, a semiconductor switching element such as a reverse blocking three-terminal thyristor 49, and a voltage detection resistor 50 is inserted between the connection point f and the negative output terminal b of the full-wave rectifier 4. A series circuit of a diode 51 and a resistor 52 is connected to both ends of the resistor 50, a series circuit of a resistor 53 and a capacitor 54 is connected to both ends of the resistor 52, and a series circuit of a resistor 55 and a capacitor 56 is connected to both ends of the capacitor 54. connect the circuit,
The gate of the reverse blocking three-terminal thyristor 49 is connected to the resistor 5.
7. The voltage detection circuit 14 is connected to the connection point between the PUT 12 and the primary coil of the pulse transformer 13 via the diode 58, and a resistor 59 is connected between the gate and cathode of the reverse blocking three-terminal thyristor 49. Configure.

An error amplifier 22 is connected between the connection point g between the resistor 55 and the capacitor 56 and the negative output terminal b of the full-wave rectifier 4. This error amplifier 22 connects one transistor 2 to a connection point g between the resistor 55 and the capacitor 56 via a resistor 23.
4, the emitter of this transistor 24 is connected to the emitter of the other transistor 25, and these emitters are connected to the negative output terminal b of the full-wave rectifier 4 through a resistor 26. The collector of the transistor 25 is connected to the connection point between the diode 41 and the capacitor 42 via a resistor 28, and the collector of the transistor 25 is connected to the connection point between the diode 41 and the capacitor 42 via a resistor 60.
A series circuit of a resistor 61, a potentiometer 31, and a resistor 62 is connected to both ends of the capacitor 42, and the base of the transistor 25 is connected to the movable element of the potentiometer 31. is connected to the base of the transistor 8 via a resistor 32. In the figure,
100 indicates a soft start circuit, 101,1
02 and 103 are resistors, 104 is a photocoupler,
105 is a transistor, 106 is a diode, 1
07 is a capacitor.

According to the above embodiment, when the AC power supply 1 is turned on,
Assume that the voltage waveform of this AC power source 1 starts a positive half cycle from zero voltage at time T1, as shown in FIG. (In the direction shown.)
Then, during the half cycle up to time T2 when the voltage becomes zero, the capacitor 9 is charged via the full-wave rectifier 4, and the voltage across the capacitor 9 reaches the resistor 1.
PUT12 at time Ta when the voltage across both ends of
becomes conductive, the pulse transformer 13 applies a trigger pulse to each gate of the bidirectional thyristor 2 and the reverse blocking three-terminal thyristor 49, and at this time Ta
At this point, the bidirectional thyristor 2 and the reverse blocking three-terminal thyristor 49 become conductive at the same time. bidirectional thyristor 2
When conductive, a voltage having the same waveform as the AC power supply 1 is generated across the load 3 as shown in FIG. On the other hand, when the reverse blocking 3-terminal thyristor 49 becomes conductive, the diode 47 becomes non-conductive due to the applied reverse voltage, and the series circuit of the diode 46, resistor 48, reverse blocking 3-terminal thyristor 49, voltage detection resistor 50, and diode D3 is closed. A closed circuit is connected in parallel to the AC power source 1, and a voltage corresponding to the voltage across the AC power source 1 determined by the resistor 48 is generated at both ends of the voltage detection resistor 50 as shown in FIG. By the way, from time Ta to time T2, as mentioned above, a voltage with the same waveform as the AC power supply 1 is generated across the load 3, so the voltage across the voltage detection resistor 50 corresponds to the voltage across the load 3. voltage. Therefore, in the half cycle from time T1 to time T2, the voltage across the voltage detection resistor 50 is used as the detection voltage, and a voltage determined according to this detection voltage is applied to the base of the transistor 24 of the error amplifier 22, and the voltage is applied to the base of the transistor 24 of the error amplifier 22. The base voltage of the transistor 25 measured by the potentiometer 31 is set as a reference voltage,
Depending on the difference between this reference voltage and the base voltage of the transistor 24, the collector of the transistor 24, that is, Q
An error output is generated at the point, and this error output is connected to the resistor 32.
is applied to the base of transistor 8 through the error output, and PUT 12 is made conductive with the proper phase according to this error output, thereby making the PUT 12 conductive for the next half cycle, that is, the half cycle from time T2 to time T3 as shown in FIG. The conduction phase of the bidirectional thyristor 2, that is, the timing of the conduction time Tb, is controlled so that the voltage across the load 3 becomes a constant voltage corresponding to the set reference voltage.

Next, from time T2, the polarity of the voltage waveform of the AC power source 1 is reversed as shown in FIG. 3, and a negative half cycle is started (at this time, the direction of current flow is the second
The direction is indicated by arrow B in the figure. ), then during the half cycle until time T3 when the voltage becomes zero, the capacitor 9 after discharge is controlled by the transistor 8 that received the above-mentioned error output during the half cycle from time T1 to time T2. At time Tb, when the voltage across the capacitor 9 becomes larger than the voltage across the resistor 11, the PUT 12 becomes conductive, and the trigger pulse is transmitted by the pulse transformer 13 to the bidirectional thyristor 2.
and to each gate of the reverse-blocking three-terminal thyristor 49, and at this time Tb, the bidirectional thyristor 2 and the reverse-blocking three-terminal thyristor 49 become conductive at the same time. When the bidirectional thyristor 2 becomes conductive, a voltage having the same waveform as the AC power source 1 is generated across the load 3 as shown in FIG. On the other hand, when the reverse blocking 3-terminal thyristor 49 becomes conductive, the diode 46 becomes non-conductive because a reverse voltage is applied, and the series circuit of the diode 47, the resistor 48, the reverse blocking 3-terminal thyristor 49, the voltage detection resistor 50, and the diode D1 is closed. A closed circuit is connected in parallel to the load 3, and a voltage is generated across the voltage detection resistor 50 that directly corresponds to the voltage across the load 3 determined by the resistor 48 as shown in FIG. Therefore, even in the half cycle from time T2 to time T3, the voltage across the voltage detection resistor 50 is used as the detection voltage, and a voltage determined according to this detection voltage is applied to the base of the transistor 25 of the error amplifier 22, and as described above. Similarly, the conduction phase of the bidirectional thyristor 2 during the next half cycle, that is, the half cycle from time T3 to time T4 as shown in FIG. 3, that is, the timing of the conduction time Tc, is controlled.
As a result, the voltage across the load 3 is controlled to be a constant voltage corresponding to the set reference voltage.

Although the above explanation was limited to one cycle of the AC power supply 1, the above-mentioned effect can be obtained in all cycles of the AC power supply 1, and therefore, even if there is a voltage fluctuation of the AC power supply 1, the voltage at both ends of the load 3 is The voltage can be maintained at a constant voltage corresponding to the set reference voltage.

In this way, according to the above embodiment, the diode 46
A series circuit of a resistor 48, a reverse blocking three-terminal thyristor 49, and a voltage detection resistor 50 is connected to a series circuit of a resistor 48, a reverse blocking three-terminal thyristor 49, and a voltage detection resistor 50. and the output terminal of the full-wave rectifier 4 whose input terminal is connected to the AC power source 1, and the AC power source A closed circuit in which a series circuit of a diode 46, a resistor 48, a reverse blocking three-terminal thyristor 49, a voltage detection resistor 50, and a diode D3 is connected in parallel to the AC power supply 1, and a diode 47 and a resistor are connected every half cycle of 1. 48, reverse blocking three-terminal thyristor 49,
A closed circuit in which a series circuit of the voltage detection resistor 50 and the diode D1 is connected in parallel to the load 3 is repeatedly formed, and in one half cycle, the AC power supply 1 is connected across the voltage detection resistor 50. A voltage corresponding to the voltage across the load 3 is generated, but since the voltage across the load 3 is substantially the same as the voltage across the AC power supply 1, the voltage across the voltage detection resistor 50 indirectly corresponds to the voltage across the load 3. In the other half cycle, a voltage that directly corresponds to the voltage across the load 3 is generated across the voltage detection resistor 50, so by using the voltage across the voltage detection resistor 50 as the detection voltage. In addition, the voltage across the load 3 can be detected every half cycle without using a transformer, and a power transformer is not required. As a result, an AC constant voltage power supply device that is small, lightweight, and low in manufacturing cost can be obtained.

The soft start circuit 100 is provided as necessary to prevent rush current when the load 3 starts up.

In the above, the configuration of the error amplifier 22 and the control circuit 7 is not limited to this embodiment, but may be any other known configuration. Further, in the voltage detection circuit 14, the circuit configuration for applying the voltage across the voltage detection resistor 50 to the error amplifier 22 can be changed as appropriate. As the semiconductor switching element, it is sufficient that it has the same function as the reverse blocking three-terminal thyristor, and other elements may be selected as appropriate. resistance 4
8 is provided as necessary and may be omitted. Further, if necessary, various bias circuits, noise filters, etc. may be added to the reverse blocking three-terminal thyristor 49 so that the blocking three-terminal thyristor 49 operates satisfactorily. The first rectifying element and the second rectifying element are not limited to diodes, but other elements may be used as long as they have a rectifying function.

[Function and effect of the invention]

According to the present invention, the series circuit of the first rectifying element and the second rectifying element is provided such that the respective terminal sides are connected to both ends of the load, and the series circuit of the semiconductor switching element and the voltage detection resistor is connected to the first rectifying element and the second rectifying element. It is inserted between the connection point of the first rectifying element and the second rectifying element and the output terminal of a full-wave rectifier whose input terminal is connected to an AC power supply, and the semiconductor switching element is synchronized with the bidirectional semiconductor switching element. a closed circuit in which a series circuit of a first rectifying element, a semiconductor switching element, and a voltage detection resistor is connected in parallel to the AC power source via a full-wave rectifier for each half cycle of the AC power source to conduct the AC power. and a second rectifying element,
A closed circuit is repeatedly formed in which a series circuit of a semiconductor switching element and a voltage detection resistor is connected in parallel to a load via a full-wave rectifier.
During one half cycle of the AC power supply, a voltage corresponding to the voltage across the AC power supply is generated across the voltage detection resistor, but at this time, the voltage across the load is substantially the same as the voltage across the AC power supply, so The voltage across the voltage detection resistor indirectly corresponds to the voltage across the load, and in the other half cycle, a voltage that directly corresponds to the voltage across the load occurs across the voltage detection resistor, so voltage detection By using the voltage across the load voltage detection resistor as the detection voltage, the voltage across the load can be detected every half cycle without using a transformer. A voltage is applied to an error amplifier, and an error output corresponding to the difference between a reference voltage set in advance and a detection voltage is applied to a control circuit by this error amplifier. Because the tropic semiconductor switching element conducts, the voltage across the load can be stably maintained at a constant voltage corresponding to the set reference voltage, regardless of voltage fluctuations in the AC power supply. It is possible to provide an AC constant voltage power supply device that is lightweight and has low manufacturing cost.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing an example of a conventional AC constant voltage power supply device, Fig. 2 is a circuit diagram showing an embodiment of the present invention, Fig. 3 is a waveform diagram showing the voltage of the AC power supply, and Fig. 4 is a circuit diagram showing an example of a conventional AC constant voltage power supply.
The figure is a waveform diagram showing the voltage across the load, and FIG. 5 is the waveform diagram showing the voltage across the voltage detection resistor. DESCRIPTION OF SYMBOLS 1... AC power supply, 2... Bidirectional thyristor (bidirectional semiconductor switching element), 3... Load, 11
1...Power transformer, 4...Full-wave rectifier, 7...Control circuit, 8...Transistor, 9...Capacitor, 12...
PUT, 13... Pulse transformer, 14... Voltage detection circuit, 15... Load voltage detection transformer, 16... Full wave rectifier, 19, 21... Capacitor, 17, 18,
20... Resistor, 22... Error amplifier, 24, 25... Transistor, 27... DC power supply for starting, 31... Potentiometer, D1, D2, D3, D4, 44,
45, 46, 47, 51, 58...Diode, 4
9... Reverse blocking 3-terminal thyristor (semiconductor switching element), 50... Voltage detection resistor, 52, 53,
55, 57, 59...Resistor, 54, 56...Capacitor, 100...Soft start circuit.

Claims (1)

[Claims] 1. An AC power supply, a load supplied with power from this AC power supply, a bidirectional semiconductor switching element inserted between this load and the AC power supply, and a full-wave switching element whose input terminal is connected to the AC power supply. rectifier and
A control circuit that controls the conduction phase of the bidirectional semiconductor switching element is connected between the output terminals of the full-wave rectifier, and a first rectifier and a second rectifier whose anode sides are connected to both ends of the load, respectively. A series circuit of rectifying elements, and a series circuit of a semiconductor switching element and a voltage detection resistor inserted between a connection point between the first rectifying element and the second rectifying element and an output terminal of the full-wave rectifier. and an error amplifier that receives the detected voltage obtained at the voltage detection resistor and generates an error output according to the difference between the detected voltage and a preset reference voltage. The AC constant voltage power supply device is characterized in that the control circuit synchronously controls conduction phases of the bidirectional semiconductor switching device and the semiconductor switching device using an error output from the error amplifier.