JPH0452813A - Ac stabilized power unit with overvoltage protecting circuit - Google Patents

Abstract

PURPOSE:To protect a load from an excess power supply voltage by detecting the excess state of a power supply voltage and inhibiting the generation of a control signal for selecting a tap. CONSTITUTION:A comparator 1 in an ignition control circuit detects an overvoltage in the power supply voltage, and when the voltage of a detection terminal exceeds the voltage of a reference terminal, an output is inverted to 'H' and the logical conditions of all NAND circuit 8 to 10 are not satisfied through an inverter 5. Thereby, all control signal output transistors(TRs) T1 to T3 are turned off by the overvoltage detecting output outputted from the comparator 1 and the generation of a tap selection control signal is inhibited. Consequently, the impression of an overvoltage to a load can be prevented, and when the power supply voltage is restored from the overvoltage state to a power supply state in a normal control range, power supply to the load can be immediately restarted and power supply based upon the stabilized voltage can be attained.

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 stabilized power supply device equipped with an overvoltage protection 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 if this voltage fluctuation is large and the power supply is unstable, the device may not be able to fully demonstrate its performance. It disappears.

By the way, the power supply situation in different countries around the world varies, and especially in developing countries, fluctuations in the 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 supply of power 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 source becomes unstable due to the region (country) or surrounding load conditions, the power source stabilizing device itself will need to have a wide control range or be expensive. Moreover, if the voltage fluctuation range is large, the system may be used at low efficiency, resulting in a larger and more complex structure, as well as higher maintenance costs and running costs.

In particular, with tap-switching AVRs, if the power supply voltage fluctuates beyond the range of adjustment capability by tap-switching, the output voltage will rise without limit in proportion to the rise in power supply voltage, making the power supply unstable and large. In a power supply system where fluctuations can occur, there is a problem of causing accidents such as equipment burnout. Another problem is the tap selection position when the power is turned on and the resulting output voltage. This is because the transient rise of the power supply voltage and the rise of the opening voltage cannot be controlled and change depending on the state at that time.

In particular, if a high voltage is applied to the device due to the above-mentioned unstable AVR control when the power is turned on, there is a problem that troubles may occur in the device or the AVR itself.

The present invention is intended to solve the above-mentioned problems, and when there is a large fluctuation in the power supply voltage that exceeds the range of adjustment capability, it prevents excessive voltage from being applied to the load and adjusts the power supply voltage. It is an object of the present invention to provide an AC stabilized power supply device equipped with an overvoltage protection circuit that can quickly apply a predetermined voltage to a load when the voltage returns to within the range.

[Means to solve the problem]

To this end, the AC stabilized power supply device equipped with the overvoltage protection circuit of the present invention includes a transformer having a plurality of taps for voltage regulation, a plurality of switching means connected to each tap, and control of tap selection by detecting the power supply voltage. The control signal generating means includes a control signal generating means for generating a signal, and an ignition means for detecting that one of the plurality of switching means is turned off and igniting the switching means by a tap selection control signal. The feature is that the overvoltage of the voltage is detected and the generation of the control signal for tap selection is prohibited based on the detection output of the overvoltage, and the control signal generating means compares the power supply voltage with a reference voltage, Multiple voltage comparison circuits that generate large judgment signals select the judgment signal with the highest priority in a preset order as the tap selection control signal through logic processing, and the judgment signal with the highest voltage is used as the overvoltage detection output for all It is characterized by having a priority processing circuit configured to cut off the output of the determination signal.

[Effect]

In the AC stabilized power supply device equipped with the overvoltage protection circuit of the present invention, generation of a tap selection control signal is prohibited when the power supply voltage becomes excessive. is adjusted to a predetermined value, and if the power supply voltage rises and becomes excessive, the power supply to the load is cut off. Therefore, it protects the load from excessive voltage and also
If the voltage drops and returns to normal, the rated voltage can be quickly supplied to the load.

〔Example〕

Examples will be described below with reference to the drawings.

FIG. 1 is a diagram showing one 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 Ma circuit. In the figure, 1 to 4 are comparators, 5 to 7 and 11 to 13 are inverting circuits, and 8 to 1
0 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, and Tl 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 triacs THI to TH5 serve as 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 the detected 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.
-Th5 is fired.

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 on state of triacs TH4 and TH3, 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 TH'3 were in the on state, triacs TH4 and TH'3 are turned on, and a certain range of output voltage is supplied to the load.

This tap switching timing is determined by the tapped transformer TR.
This is done by detecting when the voltage across the diode circuit becomes zero to prevent short circuits between the taps. In other words, the phase of voltage and current changes depending on the type of load, and in normal cases, even if the voltage becomes zero, the triac will not turn off and the current will continue to flow. Therefore, the power supply voltage and output It is difficult to detect triac off by voltage. Therefore, when switching the triac to be turned on, simply detecting that the power supply voltage or output voltage has become zero and turning on the next triac will result in a short circuit between the taps. Therefore, when trying to turn on the next triac after the triac that was on turns off, the voltage across the diode circuit detects that the current has become zero, and the next triac is ignited. It is necessary to give a signal.

In addition, since the current on the power supply side and the current on the load side are not in the same phase, a diode circuit (not shown) is installed in addition to the diode circuit on the load side for tap switching on the power supply side. It may be configured to detect a cross point.Of course, as described later, it may be configured to detect off from the voltage between the terminals of each triac TH1 to TH5 without providing a diode circuit.In this case,
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 corresponding tap or the voltage between the taps in the on state appears, and each Whether or not such a voltage is detected by the trier circuits can be used to confirm whether or not all the trier circuits are off.

In the above circuit, if it becomes unclear which of the triacs TH1 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, in order for the output voltage to rise from a low voltage, first turn on the triacs TH4 and TH3, and then sequentially increase the voltage from TH2 to THI.
Control is performed to stabilize the output voltage within a predetermined fluctuation range depending on the input voltage.

FIG. 2B shows an example of the configuration of a voltage detection control circuit that detects a power supply voltage and generates a tap selection control signal.

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

The rectifying and smoothing circuit RFI is for detecting input voltage, and supplies its output to the detection terminals of the regulators 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 R
3 to R7 and supplied as a reference voltage to be compared with the power supply voltage to comparison terminals of comparators 1 to 4, and as a control power supply to the collectors of control signal output transistors T1 to T3.

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 DI and a capacitor CI in series in parallel with the resistor R2 to generate a capacitor. This is a reference voltage start-up control circuit that constitutes a charging circuit for CI, and further includes a resistor R1, a discharging circuit of a capacitor C1 in which a diode D2 is connected in parallel with 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 C1 through the diode D1 with a fixed time constant, and when the power is cut off, the capacitor C1- is rapidly discharged through the diode D2. ing. As shown in 2, capacitor C1 is rapidly discharged in response to a drop in power supply voltage, so even if the power supply is momentarily interrupted, the voltage across the terminals of capacitor C1 will follow and decrease, and when the power is turned on again, Similarly, soft start is possible. Furthermore, by setting the charging time constant, it is possible to perform a high-speed soft start within a few cycles.

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

Therefore, when the power supply voltage is low, the outputs of all comparators 1 to 4 are at logic "L". and,
When the power supply voltage becomes high, first, the output of the comparator 4 becomes logic "H", and as it increases further, the outputs of the converters 3.2 and 1 become logic "H" in that order. In other words, the output becomes logic "H" in order from the bottom of the diagram, and logic rH
, + outputs of all the comparators on the lower side in the figure become logic "H".

Inversion circuits 5-7, 11-13, NAND circuits 8-10 are
If the outputs of a plurality of comparators 4 to 2 are logic "H" in order from the bottom of the diagram, only the NAND circuit corresponding to the topmost comparator in the diagram is logic "H". Since the input is "H", the output of only the corresponding inversion circuit is set to logic "H". Therefore, the control signal output transistor T I -T 3 driven by its inverting circuit
The 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 all the NAND circuits 8 to 1O 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 according to the circuit in figure (a), it consists of comparators 2 to 4. One more set of circuits is required, and the circuits are connected in order from the one with the lowest power supply voltage THI → TH2 → TH3 →
This becomes a control signal that turns on THI-TH2→TH3.

The control signal for turning on the triac TH5 uses 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 uses the logical sum of the control signals for turning on the lower THI→TH2→TH2. →The logical sum of the control signals that turn on TH3 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. I'll come.

FIG. 2 is a diagram showing another example of the configuration of the voltage detection control circuit.

In Fig. 2, comparator 1' corresponds to comparator 1 in Fig. 1 (b) that detects overvoltage of the power supply voltage, and when the voltage at the detection terminal exceeds the voltage at the reference terminal, the exclusive OR circuit ( EXOR) 17 is turned off, all of the control signal output transistors Tl to T3 are turned off, and generation of a control signal for tap selection is prohibited.

Incidentally, is there a known configuration in which the voltage is controlled by switching the taps of a tap-switching transformer using a semiconductor-controlled rectifying element such as a triac? It is necessary to control the timing. That is,
In triage switches, forced switching requires large capacitance elements, so generally switching is performed only at the 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 changed. A conventionally adopted control method is to apply an ignition signal to the next trier 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. By additionally connecting other circuits to the main circuit through which the load current flows, it is possible to prevent the formation of a short circuit between the terminal and the terminal by connecting multiple triacs, or to extinguish the triac quickly. We are taking great care. Therefore, as the capacity of the power supply increases, the capacity of these additional circuits also increases, making the device larger and more expensive. Furthermore, when a transformer or the like is used, a phase shift occurs, which causes a problem in that the timing shifts and noise is likely to occur.

In contrast to such conventional circuits, the AC stabilized power supply device according to the present invention eliminates the accelerator, current detection transformer, etc. from the load circuit, connects the diode circuit to the main circuit, and reduces the voltage between its terminals to zero. When this happens, it is detected that the triac is off, or when the voltages between the terminals of the triacs THI to TH5 are all no longer zero, it is detected that the triac is off, and this is used as the ignition condition for the triac to be newly controlled to be on.

FIG. 3 is a diagram showing a configuration example of an ignition control circuit that detects the voltage between the terminals of each switching element, and includes a voltage zero detection circuit 2.
1-1 to 21-3 detect the voltage between the terminals of the triac THI-TH3 and control the timing bus control transistor 2.
2-1 to 22-3, and the timing bus control transistors 22-1 to 22-3 are connected to the control power supply P.
This is connected in parallel to N 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. (It is turned on/off by a gate control signal generated by the circuit shown in bl to operate the ignition circuit.

Next, the operation of the circuit will be explained. First, triac TH
When either triacs TH1 to TH3 are conducting, the voltage between the terminals of the conducting triacs THI to TH3 is zero. For example, when triac THI is conductive, zero voltage detection circuit 2I-1 detects zero voltage, and this signal turns on timing bus control transistor 22-1. In this state, for example, the gate control transistor 23-2 is controlled by the gate control signal of the triac TH2.
Even if the timing bus control transistor 22-1 is turned on, the timing bus control transistor 22-1 becomes the same potential as the negative side of the control power supply, so no firing signal is supplied to the triac TH2.

When switching from triac THI to TH2, since the input voltage becomes high, not only comparator 4 but also comparator 5 is turned on in the circuit shown in FIG. TH1
) switches from high to low, and the gate control signal (TH2) switches from low to high. As a result, the triac THI
Even if the current passes through the current zero cross point, it is not re-ignited, and the voltage across the terminals of the triac THI increases as if it were a sine wave. Then, when the zero voltage detection signal of the zero voltage detection circuit 21-1 disappears, the timing bus control transistor 22-I 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, since the gate control transistor 23-2 is turned on by the gate control signal (TH2), the gate control transistor 23-2 is turned on when all of the timing bus control transistors 22-1 to 22-3 are turned off. A voltage is applied to the ignition circuit through 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. 4 is a diagram showing another example of the configuration of the ignition control circuit for each triac.

In FIG. 4, a circuit including 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 from the control power supply to the transistor Q2, 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, 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.
Since the base bias is applied to the transistor Q1, the transistor Q1 is turned on. As a result, the base and emitter of transistor Q2 are short-circuited, and 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. In this way, when transistor Q2 or all of the ignition control circuits (not shown) of the wired-OR connected triacs are turned off, the output of the photocoupler PC causes the transistor Q to turn off.
3 and can now supply the firing signal to the triac TH.

Note that the present invention is not limited to the above embodiments, and various modifications are possible. For example, in the above embodiment, a bidirectional control rectifier (TRIAC) is used as the tap switching means, but it goes without saying that an anti-parallel connection circuit of direction control rectifiers or other switching elements or circuits may also be used. . Also, 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, and the detection voltage is divided and applied according to each comparator. It may be configured as follows. Furthermore, as a method for switching the taps on the power supply side and the load side, the pitch between the taps on the power supply side is increased, and all taps on the load side are sequentially switched for every tap on the power supply side, or TRIAC TRI
-The pitch between taps on the power supply side where triacs TH4 and TH5 are connected is made smaller than the pitch between taps on the load side where triacs TH4 and TH5 are connected, and the control width is TRIAC THI → TH
2 → TH3 is configured so that it is approximately 1/2 of the switching control width, and as the power supply voltage fluctuates and increases, TH5 and TH4 are switched in the middle of switching from triac THI → TH2 → TH3. You can do it like this.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, a tap selection control signal is generated by detecting the power supply voltage, and a tap selection control signal is generated by detecting that a plurality of switching means are turned off. Since the switching means is ignited to change the taps of the tapped transformer, it is possible to prevent noise generation and supply a stable voltage to the load. In addition, the overvoltage of the power supply voltage is detected and the detection output prohibits the generation of the control signal for control knob selection, so it is possible to prevent overvoltage from being applied to the load. If the condition is restored, the power supply to the load can be restarted immediately. Therefore, it is possible to eliminate accidents such as burnout of the load, and it is possible to supply power with a stable voltage.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an embodiment of the AC stabilized power supply device according to the present invention, FIG. 2 is a diagram showing another configuration example of the voltage detection control circuit, and FIG. 3 is a configuration example of the ignition timing control circuit. FIG. 4 is a diagram showing another example of the configuration of the ignition control circuit of each triac. 1-4...Comparators, 5-7 and 12-15...
Inverting circuit, 8 to 11... NAND circuit, TR... Tap transformer, TH1-TH6... Triac (bidirectional control rectifier), D... Diode circuit, Tl to T
4...Control signal output transistor, RFI and RF2.
... Rectifier smoothing circuit, ST... Soft start circuit, R
G... Constant voltage generation circuit. Applicant Japan Electronics Engineering Co., Ltd. Agent Patent Attorney Ryukichi Abe (7 others) Figure (b) Figure 3 Figure 2 Figure 4 1 Nits Hired OR of TRAN-containing Tap Bay B To debt relief

Claims (2)

[Claims] (1) A transformer having a plurality of taps for voltage adjustment, a plurality of switching means connected to each tap, a control signal generation means for detecting the power supply voltage and generating a control signal for tap selection, and a plurality of switching means. The control signal generation means detects that the switch is turned off and fires the switching means using a tap selection control signal, and the control signal generation means detects an overvoltage of the power supply voltage and uses the detection output of the overvoltage to trigger the tap selection. An AC stabilized power supply device equipped with an overvoltage protection circuit, characterized in that it is configured to prohibit generation of a control signal. (2) 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 larger than the reference voltage, and tap selects the judgment signal with the highest priority in a preset order by logic processing. 2. The overvoltage protection circuit according to claim 1, further comprising a priority processing circuit configured to select the highest voltage as the control signal and to select the highest voltage determination signal as an overvoltage detection output and cut off output of all determination signals. AC stabilized power supply device with