JPH0452814A - Ac stabilized device with zero current detecting circuit - Google Patents

Abstract

PURPOSE:To detect the OFF states of all switching elements and to control tap switching timing with simple constitution by serially inserting and connecting a non-linear resistance element to the output side and detecting its inter-terminal voltage. CONSTITUTION:A main circuit to be the non-linear resistance element is connected to an output side load and the OFF states of TRIACs TH1 to TH5 to be the switching elements are detected by the voltage impressed between the terminals of the main circuit. At the time of detecting the OFF states of all the TRIACs TH1 to TH3, new ignition is controlled by an ignition control circuit 75. Thereby, transformer tap switching timing can stably be controlled by the simple constitution requiring no reactor detecting circuit in a load circuit.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention connects switching means to each tap of a tapped transformer, detects fluctuations in power supply voltage, controls on/off of the switching means, and adjusts the voltage. The present invention relates to an AC stabilizing device equipped with a zero current detection circuit that stabilizes the current.

[Conventional technology]

High-tech technology using computers is applied to precision scientific equipment, its peripheral equipment, various measuring devices, control devices, etc. in order to maintain advanced performance. Generally, these devices are supplied with AC power and operate using AC as a power source, but this voltage fluctuation is large (if the power supply is not stable, it may be difficult for the device to fully demonstrate its performance). become unable to do so.

By the way, the power supply situation in different countries around the world varies, and especially in developing countries, the fluctuations in power supply voltage are so large that an excessive voltage may be applied and the device may even burn out.

Further, even in areas where the power supply is stable, in factories and the like that consume large amounts of power, voltage fluctuations will increase in response to fluctuations in power consumption, resulting in problems similar to those described above.

If each device is designed according to the power supply rating and power supply situation of the region where it will be used in this way, it will not be possible to use a common control board or each component in the device due to the difference in power supply rating, and each device will be different. A problem arises in that compatible parts must be prepared. As a result, not only does the design burden increase, but also the manufacturing cost increases. Furthermore, since a large number of parts are prepared according to each rating, the burden of parts management becomes heavy and the yield of the product decreases.

Therefore, as a method to solve the above problems, a power supply stabilization device (AV
R), a method that controls the output voltage by rotating a sliding transformer using a servo motor, a method that uses a magnetic amplifier, etc., to stabilize the unstable input power and supply it to the equipment. Become.

[Problem to be solved by the invention]

However, as mentioned above, if the power supply becomes unstable due to the region (country) or surrounding load conditions, the power supply stabilization device itself needs to have a wide control range, making it expensive. Moreover, when the voltage fluctuation range is large, the device may be used with low efficiency, resulting in a larger and more complicated structure, and also increases maintenance costs and running costs.

In particular, in tap switching type AVRs, the timing of tap switching is a problem. This tap switching timing is performed by detecting that the voltage between the terminals of the tap switching switching element becomes zero so that a short circuit does not occur between the taps of the tapped transformer. In other words, the phase of voltage and current changes depending on the type of load, and in normal cases, even if the power supply voltage or load voltage becomes zero, the switching element will not turn off and the current will often continue to flow.
It is difficult to detect whether a switching element is off based on the power supply voltage or load voltage. Therefore, when switching the switching element to be turned on, simply detecting that the power supply voltage or load voltage has become zero and igniting the next switching element will result in a short circuit between the taps. Therefore, when trying to turn on the next switching element after the switching element that was on turns off, the voltage between the terminals of each switching element is detected, and on the condition that all voltages are not zero, the next switching element is turned on. It is necessary to provide an ignition signal to the switching element of the switch. That is,
The voltage between the terminals of the triac is almost zero when it is in the on state, but when it is in the off state, the output voltage of the relevant tap or the voltage between the other taps that are on appears, so each triac Whether or not such a voltage is detected can be used to confirm whether or not all triacs are off.

FIG. 2 is a diagram showing an example of the configuration of an ignition control circuit that detects the voltage between the terminals of each switching element.
1-1 to 21-3 detect the voltage between the terminals of the triac THI-TH3 and control the timing bus control transistor 2.
The timing bus control transistors 22-1 to 22-3 are connected in parallel to the control power supply PN through a resistor R3 to form a wired-OR circuit. Then, a timing bus is connected to the connection point between this resistor R3 and the timing bus control transistors 22-1 to 22-3, and the gate control transistors 23-1 to 23-3 are also connected to this timing bus to receive gate control signals. The emitter output is used as the firing signal for the triacs THI to TH3.

Next, the operation of the circuit will be explained. First, triac TH
When any of the triacs 2 to TH3 is conductive, the voltage between the terminals of the triacs THI to TH3 that are conductive is zero. For example, when l.Liac THI is conductive, the zero voltage detection circuit 21-1 detects zero voltage, and this signal causes the timing bus control transistor 22
-1 is on. In this state, for example, even if the gate control transistor 23-2 is turned on by the gate control signal of the triac TH2, the timing bus becomes the same potential as the negative side of the control power supply due to the timing bus control transistor 22-1 being turned on, so the triac T
No firing signal is provided to H2.

When switching from triac THI to TH2, the gate control signal (THI) switches from high to low, and the gate control signal (TH2) switches from low to high. As a result, when the triac THI passes the current zero cross point, it is extinguished, and the voltage between the terminals of the triac THI increases according to a sine wave. And the voltage zero detection circuit 21
When the -1 voltage zero detection signal disappears, the timing bus control transistor 22-1 is turned off, and at this point, all of the timing bus control transistors 22-1 to 22-3 are turned off. On the other hand, the gate control transistor 23-2
are turned on by the gate control signal (TH2), so the timing control transistors 22-1 to 22-2
When all of the triacs 2-3 are turned off, a voltage is applied to the ignition circuit through the gate control transistor 23-2, and the triac TH2 is turned on.

As described above, the timing bus control transistor 2 is wired-OR connected to the voltage zero detection circuits 21-1 to 21-3.
Since the timing bus is controlled by 2-1 to 22-3, tap switching for voltage stabilization can be smoothly performed with a simple circuit configuration. Moreover, without delaying the firing timing, the next triac can be fired with only a slight delay from when one triac goes out until the voltage rises between the terminals of the triac.

FIG. 3 is a diagram showing another example of the configuration of the ignition control circuit for each triac.

In FIG. 3, a circuit consisting of diodes D1 and D2 and a transistor Q1 constitutes a zero voltage detection circuit, and a timing bus is controlled by a transistor Q2. Further, the gate control signal is supplied to a photocoupler PC consisting of a photodiode and a phototransistor, and the output signal thereof controls on/off of the transistor Q3 of the ignition circuit.

Briefly explaining the operation, when the voltage between the terminals of the triac TH is zero, the transistor Q1 is off, so a base bias is applied to the transistor Q2 from the control power supply and the transistor Q2 is turned on. Therefore, the timing bus has the same potential as the negative side of the control power supply.

When the voltage across the terminals of the triac TH is no longer zero, and if the potential on the tap side of the transformer (upper side in the figure) is positive, that voltage passes through the diode D1 and is applied to the transistor Q1.
is applied as a base bias, so transistor Q1 is turned on. As a result, the base and emitter of the transistor Q2 are shorted and the transistor Q2 is turned off. Further, when the potential on the load side (lower side in the figure) is positive, that voltage is applied as a reverse bias between the base and emitter of the transistor Q2 through the diode D2, so that the transistor Q2 is turned off. When all the transistors Q2 are turned off in the firing control circuit (not shown) of each triac connected in a wired-OR connection in this way, the output of the photocoupler PC causes the transistor Q3 to turn off.
can be turned on and a firing signal can be supplied to the triac TH. Note that it goes without saying that the trigger signal applied to the triac may be generated by a commonly used circuit combining one-shot multi or pulse transformers.

Detecting the off state of a switching element using the voltage between the terminals of each switching element as described above requires a voltage detection circuit for each switching element and a circuit for logically processing the output, and the larger the number of taps, the larger the circuit size. There is a problem of becoming

The present invention solves the above-mentioned problems, and is a zero current detection device that can detect the off state of all of a plurality of tap switching switching elements with a simple configuration and control the timing of switching between taps and taps. An object of the present invention is to provide an AC stabilizing device equipped with a circuit.

[Means to solve the problem]

For this purpose, an AC stabilizing device equipped with a zero current detection circuit according to the present invention includes a transformer having a plurality of voltage regulating pipes,
A plurality of switch notching means connected to each tap, a nonlinear resistance element inserted and connected in series on the output side, and a control signal generation means that detects the power supply voltage by comparing it with a reference voltage and generates a control signal for tap selection. , and ignition means for detecting that the plurality of switching means are turned off from the voltage between the terminals of the nonlinear resistance element and igniting the switching means using a tap selection control signal. Further, the transformer of the present invention has voltage adjustment taps on the input side and the output side, and the control signal generation means includes a plurality of voltage comparison circuits that compare the power supply voltage with a reference voltage and generate a determination signal that is larger than the reference voltage. , and is configured to select the highest priority judgment signal in a preset order as a control signal for tap selection by logic processing, and to use the judgment signal with the highest voltage as an overvoltage detection output and cut off output of all judgment signals. It is characterized by having a priority processing circuit.

[Effect]

In the AC stabilizing device equipped with the zero current detection circuit of the present invention,
Since a nonlinear resistance element is inserted and connected in series on the output side, it is possible to detect the on/off state of the switching element connected to each tap of the tapped transformer without having to detect the voltage between each terminal. By detecting the voltage between the terminals, it is possible to detect that all of the switching elements are turned off. Therefore, it is possible to detect from the voltage between the terminals that all of the plurality of switching means are turned off, and to fire a new switching means using the tap selection control signal.

〔Example〕

Examples will be described below with reference to the drawings.

FIG. 1 is a diagram showing an embodiment of the AC stabilized power supply device according to the present invention, in which (a) shows the configuration of the main circuit, and (b) shows the configuration of the control circuit. In the figure, 1 to 4 are comparators, 5 to 7 and 11 to 13 are inverting circuits, and 8 to l.
O is a NAND circuit, CN is a voltage detection control circuit, TG is an ignition control circuit, TR is a tapped transformer, THI to TH5 are triacs (bidirectional control rectifiers), D is a diode circuit, T1 to T3 are control signals Output transistors, RFI and RF2 are rectifier and smoothing circuits, ST is soft start circuit, R
G indicates a constant voltage generation circuit.

In FIG. 1(a), the tapped transformer TR has a plurality of switching taps on the input side and the output side, respectively, and the triac THI-TH5 serves as a tap switching means for the tapped transformer TR. This is a bidirectionally controlled rectifier connected to the The diode circuit is connected in antiparallel and inserted into the output side as a means for detecting the zero point of the output current. The voltage detection control circuit CN detects the voltage on the input side (power supply voltage) and generates a control signal for selecting a tap according to that voltage, and the ignition control circuit TG is a diode circuit. The zero cross point of the current is detected from the voltage between the terminals, and the triac THI is activated by the control signal generated by the voltage detection control circuit CN.
- This is to ignite TH5.

Next, the overall operation will be explained.

First, in the lowest power supply voltage range, the triac TH
5 and THI are turned on, and as the power supply voltage fluctuates and increases, the triac THI→T
Turn on H2 → TH3 in sequence and switch taps to step down the voltage. When the temperature rises further, triac TH4 and THI are controlled to be on, and similarly triac THI→TH
By sequentially controlling the switching from 2 to 2, the output voltage is stabilized within a certain range (the range of the voltage between taps) against fluctuations in the input voltage. In this way, when the power supply voltage further increases from the state where triacs TH4 and TR3 are on, triacs TH4 or TH3 or TH4 and TH3 are turned off, and the power supply is cut off.

However, the power supply voltage drops and the triac TH4 and TH
When the voltage returns to the voltage when TRIAC TH4 and TH3 were in the on state, triacs TH4 and TH3 are turned on and a certain range of output voltage is supplied to the load.

This tap switching timing is performed by detecting that the voltage between the terminals of the diode circuit becomes zero. When trying to turn on the next triac after the triac that was on turns off, the voltage between the terminals of the diode circuit detects that the current flowing to the load through the triac has become zero, and the next triac is turned on. Give a firing signal to the triac. In this voltage detection circuit, the voltage between the terminals of the diode circuit is amplified to a predetermined voltage using, for example, an OP amplifier, and the voltage is amplified by transistors Ql and Q2 in positive and negative half waves using diodes D1 and D2 as shown in Fig. 3. It may be configured to detect. In this way, the timing at which all triacs are turned off can be detected with one circuit, without providing a voltage detection circuit for each triac as shown in FIG. For example, in the case of the illustrated circuit, conventionally it was necessary to provide a voltage detection circuit for each triac THI-TH5 as shown in FIG. 2, but according to the present invention, a voltage detection circuit is provided only for the diode circuit. All you have to do is set it up. Also, since the current on the power supply side and the current on the load side are not in the same phase, for tap switching on the power supply side, a diode circuit (not shown) is provided separately from the diode circuit on the load side. It may be configured to detect a zero cross point of the current.

In the above circuit, if it becomes unclear which of the triacs THI to TH5 will fire when the power is turned on, an abnormal voltage may be applied to the device, which may cause a failure. Therefore, when the power is turned on, the triacs TH4 and TH3 are first turned on, and then the voltage is increased sequentially from TH2 to THI so that the output voltage rises from a low voltage.
Control is performed to stabilize the output voltage within a predetermined fluctuation range depending on the input voltage.

An example of the configuration of a voltage detection control circuit that detects a power supply voltage and generates a tap selection control signal is shown in the same figure (bl).

In the figure (b), the rectifier and smoothing circuits RFI and RF2 are connected to the input side of the figure (al), and convert the power supply voltage through a transformer at a predetermined transformation ratio to rectify and smooth it.

The rectifying and smoothing circuit RFI is for input voltage detection, and supplies its output to the detection terminals of the comparators 1 to 4. The rectifying and smoothing circuit RF2 is for generating a control voltage, and its output is controlled to a constant voltage by a constant voltage generating circuit RG, and a resistor R3
It is divided by R7 and supplied to the comparison terminals of comparators 1 to 4 as a reference voltage to be compared with the power supply voltage, and is also supplied as a control power source to the collector of the control signal output transistor Tl-73.

The soft start circuit ST is connected to the output terminal of the constant voltage generating circuit RG, and constitutes a voltage dividing circuit for constant voltage output by resistors R1 and R2, and connects a diode D1 and a capacitor C1 in series in parallel with the resistor R2 to generate a capacitor. This is a reference voltage start-up control circuit comprising a charging circuit for capacitor C1, and a discharging circuit for capacitor C1 in which a diode D2 is connected in parallel with a resistor R1 and a diode DI in the opposite direction. With this circuit configuration, when the power is turned on, the reference voltage is gradually raised by charging the capacitor CI through the diode D1 with a fixed time constant, and when the power is cut off, the capacitor CI is rapidly discharged through the diode D2. There is. In this way, capacitor C1 is rapidly discharged in response to a drop in power supply voltage, so even if the power supply is momentarily interrupted, for example, capacitor C1 will follow the voltage across the terminals and become low (lower when the power is turned on again). In addition, by setting the charging time constant, a high-speed soft start is possible in a few cycles.

Each of the comparators 1 to 4 outputs logic "LJ" when the voltage at the detection terminal is lower than the voltage at the comparison terminal, and outputs logic "H" when the voltage at the comparison terminal becomes higher.

However, when the power supply voltage is low, the outputs of all comparators 1 to 4 become logic rLJ. and,
When the power supply voltage becomes high, first, the output of the comparator 4 becomes logic "H", and when it becomes higher still, the output of the comparator 3.2 and then becomes logic rHj in that order. In other words,
The output becomes logic rHJ in order from the bottom of the diagram, and becomes logic "H".
All the comparators on the lower side of the figure than the output comparators become outputs or logic "H".

Inverting circuits 5-7, 11-13, NAND circuits 8-1O are
It constitutes a priority circuit, and when the outputs of a plurality of comparators 4 to 2 are at logic rHj in order from the bottom in the figure, only the NAND circuit corresponding to the comparator at the top is all at logic rHJ. Therefore, only the corresponding inverting circuit outputs logic "H". Therefore, only the control signal output transistors T1 to T3 driven by the inverting circuit are turned on, and this emitter output is used as a control signal to turn on the triac.

The comparator 1 detects overvoltage of the power supply voltage, and when the voltage at the detection terminal exceeds the voltage at the reference terminal, the logic conditions of the NAND circuits 8 to 10 no longer hold. That is, all of the control signal output transistors T1 to T3 are turned off by the overvoltage detection output of the comparator 1, and generation of the control signal for tap selection is prohibited.

The circuit in figure (b) is an example of the configuration without triacs TH4 and TH5, or if the circuit in figure (b) is configured in accordance with the circuit in figure (a), it is a circuit consisting of comparators 2 to 4. In addition, one more set is required, and in order from the lowest power supply voltage, triac TH5, THI groan TH2 → T
This becomes a control signal that turns on H3→TH4→THI→TH2→TH3. The control signal for turning on the triac TH5 is the logical sum of the control signals for turning on the lower THI→TH2→TH3, and the control signal for turning on the triac TH4 is the logical sum of the control signals for turning on the lower THI→TH2→TH3.
A logical sum of control signals to turn on 3 can be used.

Note that, in contrast to the feedforward control system described above, a feedback control system may be used, and the load voltage may be input to the rectifier circuit. In this case, the rectifier circuit and the
A pair of comparison circuits (determining whether the upper limit value is exceeded and whether or not the lower limit value is divided) are sufficient, and a priority processing circuit is not required. However, in this case, control is required to sequentially lower the tap position each time the load voltage exceeds the upper limit value, and conversely, to sequentially lower the tap position each time the load voltage falls below the lower limit value. A circuit is required that retains this information and recognizes the next switching tap based on the determination signal from the comparison circuit. As this specific circuit, for example, an up/down counter can be used. In this case, for example, the gate control signal may be selectively generated by counting up by the tap rounding up signal from the comparator circuit, counting down by the tap rounding down signal, and making the count value correspond to the tap position. can.

By the way, is there a known configuration in which the voltage is controlled by switching the taps of a tap-switching transformer using a semiconductor-controlled rectifier such as a tritic? It is necessary to control the timing. That is,
In a triac, forced switching requires an element with a large capacity, so switching is generally performed at a zero cross point where the current becomes zero.

For example, when the triac THI is turned on and power is being supplied to the load, if you want to switch from the triac THI to TH2 because the voltage has increased, the supply of the ignition signal to the triac THI is stopped, and the current of the triac THI is reduced. A conventionally adopted control method is to apply an ignition signal to the next triac TH2 on the condition that it becomes zero. Furthermore, in order to make this switching smooth, current detection means such as a transformer (CT) is inserted and connected in series to each triac in the load circuit, and an arc extinguishing reactor is connected. A configuration in which other circuits are additionally connected to the main circuit through which the load current flows to prevent short circuits from being formed between taps by connecting multiple triacs, or to quickly extinguish the triacs. Various proposals have been made. Therefore, as the capacity of the power supply increases, the capacity of these additional circuits also increases, making the device larger and more expensive. Further, when a transformer or the like is used, a phase shift occurs, which causes a problem in that the timing is shifted and noise is likely to occur.

In contrast to the conventional circuit, the AC stabilized power supply device according to the present invention connects the diode circuit to the main circuit as described above, detects the off state of the triac from the voltage between its terminals, and controls the triac to turn on again. By providing the TRIAC ignition conditions, the load circuit eliminates the need for an accelerator, current detection transformer, etc.

FIG. 4 is a diagram for explaining another embodiment of tap switching according to the present invention.

In the above embodiment, the pitch between taps on the power supply side is increased, and for every tap on the power supply side, all taps on the load side are connected to the triac TH5, THI→TH2-TH3→TH4→THI→
Either TH2 and TH3 are switched sequentially, or the pitch between taps on the power supply side is smaller than the pitch between taps on the load side, so that the tap control width on the power supply side is approximately 1/2 of the tap control width on the load side. It may be configured as follows. FIG. 4 shows an example of this.

In the example shown in Figure 4, the power supply side 1
91.4V on the load side for 00v and 104V taps
, 98.6V, 106V, and 114V taps are provided, and triacs THI to TH are used as the respective switching means.
6.

In this configuration, when the horizontal axis is the input voltage and the vertical axis is the output voltage, the input/output characteristics are as shown in FIG. 3(b).

In other words, the input/output characteristics are triac TRI and TH6
When turned on, it becomes ■, and the triac TH6 becomes TH5.
When switching to and turning on triac THI and TH5, it becomes ■. Similarly, when triacs TH2 and TH6 are turned on, ■, when triacs TH2 and TH5 are turned on, ■, when triacs TH3 and TH6 are turned on, ■, when triacs TH3 and TH5 are turned on, ■, when triacs TH4 and TH6 are turned on, ■, Triac T
When H4 and TH5 are turned on, the input/output characteristics become as shown in ■. In this way, even if the input voltage fluctuates in the range of 85V to 117V, it will be 1'00V±2.3 as shown in the same figure (bl).
The fluctuation range of v can be suppressed, and the output voltage can be stabilized within a narrower range.

Note that the present invention is not limited to the above embodiments, and various modifications are possible. For example, in the above embodiment, by inserting and connecting a diode circuit in series with the load circuit to detect the load current, it was detected whether all the switching elements were in the on state. A triac, an anti-parallel connection of triacs, or a series circuit of other switching means and a nonlinear resistance element may be used.

It goes without saying that a bidirectionally controlled rectifying element, an inverse parallel connection circuit of unidirectionally controlled rectifying elements, or other switching elements or circuits may be used as the tap switching means. Furthermore, the configuration is such that the reference voltage is divided and the reference voltage is applied according to each comparator, or the same reference voltage is applied to each comparator,
The detection voltage may be divided and applied to each comparator.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, a non-linear resistance element is inserted and connected in series with the load circuit and the load current is detected from the voltage between its terminals. It is possible to detect the vicinity of the zero point of the load current and perform smooth tap switching without providing a detection circuit to determine whether the switching element connected to the tap is turned off. It can be simplified. It is possible to prevent noise from occurring due to

[Brief explanation of the drawing]

FIG. 1 is a diagram showing one embodiment of the AC stabilized power supply device according to the present invention, FIG. 2 is a diagram showing an example of the configuration of an ignition control circuit, and FIG.
This figure is a diagram showing another example of the configuration of the ignition control circuit, and FIG. 4 is a diagram for explaining another embodiment of tap switching according to the present invention. 1-4...Comparators, 5-7 and 11-13...
Inverting circuit, 8~IO...NAND circuit, CN...Voltage detection control circuit, TG...Ignition control circuit, TR...Tapped transformer, THI~TH5...Bidirectional control rectifier element , D... Diode circuit, T1-T3... Control signal output transistor, RFI and RF2... Rectifier and smoothing circuit, ST... Soft start circuit, RG... Constant voltage generation circuit. Applicant Japan Electronics Engineering Co., Ltd. Agent Patent Attorney Ryukichi Abe (7 others) Figure 2 Figure 3 Tufts with Trane 1 Ni 7 Hifiiyad OR Giei Keito Hayabusa 11 Monument

Claims (3)

[Claims] (1) A transformer with multiple voltage adjustment taps, multiple switching means connected to each tap, a nonlinear resistance element inserted and connected in series on the output side, and a tap that detects the power supply voltage by comparing it with a reference voltage. A control signal generating means for generating a selection control signal, and an ignition means for detecting that the plurality of switching means are turned off from the voltage between terminals of the nonlinear resistance element and igniting the switching means with a tap selection control signal. An alternating current stabilizing device equipped with a zero current detection circuit. (2) The AC stabilizing device equipped with a zero current detection circuit according to claim 1, wherein the transformer has voltage adjustment taps on the input side and the output side. (3) The control signal generation means includes a plurality of voltage comparison circuits that compare the power supply voltage with a reference voltage and generate a judgment signal greater than the reference voltage, and tap selects the judgment signal with the highest priority in a preset order by logic processing. 2. The zero current detection according to claim 1, further comprising a priority processing circuit configured to select the determination signal based on the highest voltage as the control signal of the overvoltage detection output and to cut off output of all determination signals. AC stabilizer with circuit.