JPH05137318A - Feeder circuit for constant-voltage power supply - Google Patents

Abstract

PURPOSE:To feed the charging voltage of the capacitor of an energy-storing circuit to a constant-voltage power supply from the energy-storing circuit at the time of detection of a momentary break by providing the energy-storing circuit on the output side of a rectifier circuit in a feeder circuit being of a line operator type for feeding DC voltage from a commercial power supply to the constant-voltage power supply and equipped with an active smoothing filter function. CONSTITUTION:An energy-storing circuit 40 is connected between a rectifier circuit 20 and active smoothing filter circuit 30 and an energy-storing capacitor 41 is charged with electricity to the peak value of rectified voltage Vr. When service interruption is detected by a momentary-break detection circuit 50, the energy-storing circuit 40 receives the detection signal DS of the circuit 50 and immediately turns ON a transistor switch 43 to supply a constant-voltage power supply 10 with the charging voltage of the capacitor 41. Thus, it is possible to normally charge the capacitor 41 without affecting the operation of the active smoothing filter circuit 30, to prevent the interruption of operation of the constant-voltage power supply 10 at the time of a momentary break and to reduce the static capacity of the capacitor 41.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is for supplying a DC voltage to a constant voltage power source such as a so-called switching regulator while intermittently controlling an AC voltage from a commercial frequency power source so that a current drawn from the power source becomes a sine wave. A circuit,
The present invention relates to a power supply circuit for a constant voltage power supply capable of continuing power supply even during a short-time power failure or a momentary power failure.

[0002]

As is well known, since a constant voltage power source such as a switching regulator is usually a so-called DC-DC converter, it is necessary to feed a DC voltage to it. In the case of a so-called line-operated type which is fed from a commercial frequency power source. A rectifier circuit having a smoothing function is used as the simplest power supply circuit of.

In this rectifier circuit, it is necessary to use a capacitor for smoothing the pulsating rectified voltage, but the current taken from the commercial frequency power source has a sharp peak waveform for charging the smoothing capacitor, so that the reactive or apparent current is excessive. There is a problem. This can be reduced by incorporating a current limiting reactor or choke coil in the rectifier circuit to make the peak of the charging current dull, but it is difficult to completely eliminate it, and the harmonics associated with the residual reactive current adversely affect the power supply side. There is still a fear, and a fairly large noise filter is required to completely remove harmonics.

For this reason, recently, an active smoothing filter circuit is often incorporated in a line-operated type power supply circuit for intermittently controlling a current from a commercial frequency power source so as to have a sinusoidal waveform as described above. The present invention also relates to this type of power supply circuit, and the configuration of a conventional example of the power supply circuit having an active smoothing filter function and the main points of its operation will be described below with reference to FIG.

The right half of FIG. 2 is a constant voltage power supply 10, and the left half is a power supply circuit composed of a rectifying circuit 20 which receives an AC voltage Va from the power supply 1 and an active smoothing filter circuit 30. The active smoothing filter circuit 30 receives the rectified voltage Vr of the full-wave rectified waveform from the rectifier circuit 20 in its choke coil 31, turns on the high-frequency field effect transistor 32, accumulates energy in this choke coil 31, and turns on the transistor 32. Main circuit configuration of a so-called step-up DC-DC converter that supplies the voltage stabilized by the capacitor 34 via the diode 33 to the constant voltage power supply 10 as its input voltage Vi while repeating the operation of turning off and releasing energy. And a transistor 32 so that the current drawn from the commercial frequency power supply 1 has a sine wave shape.
Incorporated therein is a control circuit 35 for that gate which controls the timing of the on / off operation of the. This control circuit 35
Is the actual value of the power supply voltage on the output side of the diode 33,
The full-wave rectified voltage waveform on the input side of the choke coil 31, the actual value of the current flowing through the transistor 32 detected by the resistor 32a during the charging time, and the zero point of the current flowing through the choke coil 31 are determined by the auxiliary coil 31a. The detected timing signal is provided as shown.

The control circuit 35 which receives these makes a target value of the current flowing through the transistor 32 which is similar to the rectified voltage waveform so as to keep the actual voltage value at the target value, and when the actual current value reaches this target value, the transistor The operation of turning off 32 and turning on at the current zero point of the choke coil 31 is repeated. Due to the frequent on / off operation of the transistor 32 due to this, the current flowing through the choke coil 31 has a waveform in which a triangular wave whose peak value changes sinusoidally is repeated at a high frequency,
Therefore, the current drawn from the power source 1 through the rectifier circuit 20 has a waveform in which a high frequency of several tens kHz is usually superimposed on the sine waveform of the commercial frequency. That is, the active smoothing filter circuit 30 originally functions as an active filter for smoothing a sharp peak-shaped waveform into a sine wave, as described above. The high frequency on the current waveform is not usually harmful, but if necessary, it can be easily removed by inserting a very small noise filter on the power supply 1 side.

The constant voltage power supply 10 for receiving a substantially constant DC voltage from the power supply circuit shown in FIG. 2 is a normal switching power supply, and will be briefly described. In the illustrated example, the flyback transformer 11 receives an input voltage Vi and interrupts the current of its primary coil 11a with a transistor 12, and rectifies the AC voltage of the secondary coil 11b with a diode 13 and stabilizes it with a capacitor 14. For example, a DC voltage of 5V is output as the output voltage Vo. The voltage control circuit 15 receives the output voltage Vo and sends a switching command according to the actual value to the drive circuit 17 via the photocoupler 16 in the example shown in the figure, and the transistor 12 is turned on / off to keep the output voltage Vo constant. Keep on. The constant voltage power supply 10 shown in FIG. 2 is an insulating type, and its input side ground point Ei and output side ground point Eo are separated from each other.

[0008]

The power feeding circuit having the active smoothing filter function as described above has an advantage that a sinusoidal current can be taken from the commercial frequency power source, but since the operating principle is the high frequency operation as described above, However, there is a problem that the operation is interrupted by a shortage of the commercial frequency power source within a very short time of one cycle or less, and an electronic circuit or the like fed from the constant voltage power source malfunctions.

That is, in a normal power supply circuit, it is possible to sufficiently cope with such short-time power failure or momentary power failure by using a capacitor 34 having a large stored energy as shown in FIG. 2, but as mentioned above, the active smoothing filter circuit 30 is choked. Because high-frequency operation is performed under self-excited oscillation that controls the on / off timing of the transistor 32 according to the waveform of the current in the coil 31, the capacitance value of the capacitor 34 cannot be increased so much in relation to such high-frequency operation. is there. Further, even on the side of the constant voltage power supply 10, if the amount of energy stored in the stabilizing capacitor 14 is increased, instantaneous power failure can be dealt with.
Since the output voltage Vo is low, the required capacitance value is extremely large, making it impractical.

An object of the present invention is to solve the above problems and improve a power supply circuit having an active smoothing filter function so that the output voltage of the constant voltage power supply is not interrupted or lowered even when the commercial frequency power supply is instantaneously stopped. ..

[0011]

According to the present invention, an object of the present invention is to provide a rectifier circuit which receives an AC voltage from a commercial frequency power source, and an active smoothing filter which receives a rectified output from the commercial frequency power source and controls a current from the commercial frequency power source in a sine wave shape. When a power failure is detected by the instantaneous blackout detection circuit, the power supply circuit is composed of a circuit, an energy storage circuit that charges the capacitor by the rectified output of the rectifier circuit, and an instantaneous blackout detection circuit that detects a short-term blackout of the commercial frequency power supply. This is achieved by supplying the charging voltage of the capacitor from the energy storage circuit to the constant voltage power supply.

It is advantageous to incorporate a charging diode, which conducts in the direction of charging the capacitor, in the energy storage circuit having the above-mentioned structure. In addition, in order to supply power to the constant-voltage power supply from the energy storage circuit during an instantaneous power failure, a transistor switch that turns on in response to the detection signal from the instantaneous power failure detection circuit is installed in the energy storage circuit, and the charging diode and energy storage capacitor are connected at a fixed point. It is sufficient to supply power to the voltage power supply. Further, it is advantageous to prevent current from flowing into the active smoothing filter circuit side when the power is supplied from the energy storage circuit to the constant voltage power supply by a diode.

Although the instantaneous blackout detection circuit may monitor the voltage on the input side or the output side of the rectifier circuit, it is simplest and practical to monitor the substantially constant output voltage of the active smoothing filter circuit. It may be arranged to emit a detection signal indicating a power failure or a momentary power failure when the monitored voltage falls below a predetermined limit value. To eliminate the difference between the voltage supplied from the active smoothing filter circuit and the voltage supplied from the accumulator circuit to the constant voltage power supply by this detection signal, use the fact that the active smoothing filter circuit is a boost type. The output voltage is preferably set to about the peak value of the AC voltage of the commercial frequency power supply, which is the charging voltage of the capacitor of the accumulator circuit.

[0014]

According to the present invention, an energy storage circuit for accumulating necessary energy in the capacitor to guarantee the power supply to the constant voltage power supply at the momentary interruption of the commercial frequency power supply is provided and connected to the output side of the rectifier circuit. This allows the capacitor to be always charged by the rectified output without affecting the operation of the active smoothing filter circuit, and the rectified voltage of the commercial frequency power supply must be much higher than the output voltage of the constant voltage power supply. By utilizing this, the capacitance of the capacitor of the energy storage circuit required for energy storage is reduced by two digits or more compared to the case where energy is stored on the output side of the constant voltage power supply.

Since the power storage circuit maintains the energy storage state without power consumption after the capacitor is charged immediately after the commercial frequency power is turned on, the power storage circuit immediately maintains the power failure when the power failure is detected by the instantaneous power failure detection circuit. Can supply power to a constant voltage power supply. The capacitance required for the capacitor is, for example, 1 to 3 of the commercial frequency power supply.
Even when assuring power supply to a constant voltage power supply with a current capacity of several tens of amps during a two-cycle power outage, it can be done with about several hundred μF.

[0016]

Embodiments of the present invention shown in FIG. 1 will be described below. The parts corresponding to those in FIG. 2 of FIG. 1 are designated by the same reference numerals, and the description of the overlapping parts will be appropriately omitted. The constant voltage power supply 10 shown in FIG. 1 is the same as that shown in FIG.

The energy storage circuit 40 of FIG. 1 is connected between the rectification circuit 20 and the active smoothing filter circuit 30, and the commercial frequency power supply 1 is a full-wave rectification type rectification circuit for the AC voltage Va of usually 100V.
Pulsating rectified voltage with a peak value of about 140 V rectified by 20
Receive Vr. In the power supply circuit of the present invention, the waveform of the current taken from the power supply 1 is controlled by the active smoothing filter circuit 30 to have a sine wave shape. Therefore, the rectification output side of the rectification circuit 20 has a smoothing capacitor or smoothing reactor as in the case of FIG. Is not connected.

The energy storage circuit 40 of this embodiment comprises a capacitor 41 for energy storage and a charging diode which conducts only in the charging direction.
42 and a transistor switch 43 for power supply, which is connected to the interconnection point of both. In this way the storage capacitor 41
Is charged through the charging diode 42, the capacitor 41 is charged to the peak value of the rectified voltage Vr, and discharge is prevented when the ripple occurs. Therefore, after the capacitor 41 is charged immediately after the power source 1 is turned on, the energy storage circuit 40 always maintains the energy storage state without consuming any electric power. The transistor switch 43 may be, for example, a field effect transistor and turned on by the detection signal DS of the instantaneous blackout.

The active smoothing filter circuit 30 has the same structure as that shown in FIG. The energy storage circuit 40 is connected between this and the rectifier circuit 20, but since the current is not taken as described above after the capacitor 41 is initially charged, the active smoothing filter circuit 30 has the energy storage circuit 40. It is possible to perform the operation described in FIG. 2 in which a sinusoidal current is taken from the power source 1 without being affected by the above.

The instantaneous blackout detection circuit 50 of this embodiment is connected to the output side of the active smoothing filter circuit 30. The instantaneous blackout detection circuit 50 may be connected to any place as long as it can detect a power failure by the voltage on the input side or output side of the rectifier circuit 20, for example, but the active smoothing filter circuit 30 with the most stable voltage in the power supply circuit 30 It is advantageous to connect to the output side of, and it is possible to detect the almost constant DC voltage by, for example, resistance voltage division and to issue a detection signal DS indicating a power failure or an instantaneous blackout when the voltage falls below a predetermined limit value. ..

When a power failure is detected by the instantaneous power failure detection circuit 50, the energy storage circuit 40 receives the detection signal DS and immediately turns on the transistor switch 43 to supply the charging voltage of the capacitor 41 to the constant voltage power source 10. .. The power supply path at this time is preferably connected from the transistor switch 43 to the output side of the diode 33 of the active smoothing filter circuit 30 as shown in the figure, whereby the power supply current from the energy storage circuit 40 is directed to the active smoothing filter circuit 30 side. It is possible to prevent backflow.

The output of the active smoothing filter circuit 30 should be minimized in order to minimize the fluctuation of the input voltage Vi of the constant voltage power supply 10 when the power supply is switched from the active smoothing filter circuit 30 side to the energy storage circuit 40 side. It is preferable to set the voltage together with the peak value of the rectified voltage Vr, which is the charging voltage of the capacitor 41 in the energy storage circuit 40. Since the active smoothing filter circuit 30 is the step-up DC-DC converter as described above, it is easy to set the output voltage. For example, the inductance value of the choke coil 31 and the capacitance value of the capacitor 34 are set, and the operation of the control circuit 35 is adjusted. This condition can be satisfied by the following.

In the power supply circuit of FIG. 1 described above, the amount of energy stored in the energy storage circuit 40 is set so that power supply can be guaranteed against a power failure of the commercial frequency power supply 1 for, for example, 1 to 2 cycles. When the output voltage Vo of the constant voltage power supply 10 is 5V and its current capacity is 20A, the capacitor on the low voltage output side of Fig. 2
When trying to store the power supply energy in 14, the commercial frequency 1
At least 80,0 to guarantee power during a cycle interruption
It is necessary to have an extremely large capacitance of 00 μF.
However, in the present invention, the capacitor 41 of the storage circuit 40 is charged to the peak value of the rectified voltage Vr, and the AC voltage Va of the power source 1 is reduced to 10%.
When the peak value of rectified voltage Vr is 0V and the peak value of rectified voltage is 140V, the amount of energy stored is proportional to the square of the charging voltage.
In other words, it is sufficient to have a capacitance of 1/800.
The required reduction rate of the electrostatic capacity depends of course on the rated voltage, but in the present invention, the capacitor of the storage circuit 40 is
The capacitance required for 41 can be reduced by at least two digits, and the practicality of the power supply circuit with guaranteed power supply during an instantaneous power failure can be improved.

[0024]

As described above, according to the present invention, a power supply circuit for receiving an AC voltage from a commercial frequency power supply and supplying a DC voltage to a constant voltage power supply is provided with a rectifier circuit for receiving the AC voltage and a rectified output of the rectifier circuit. An active smoothing filter circuit that controls the current taken from the commercial frequency power supply so that it has a sinusoidal waveform, an energy storage circuit that charges the capacitor by the rectified output of the rectifier circuit, and an instantaneous power failure detection circuit that detects a short-term power failure of the commercial frequency power supply. The following effects can be obtained by supplying the charging voltage of the capacitor from the energy storage circuit to the constant voltage power source when the power failure is detected by the instantaneous blackout detection circuit.

(A) Energy is stored and stored in the capacitor of the energy storage circuit, and the charging voltage of the capacitor is supplied to the constant voltage power supply by the detection signal of the instantaneous power failure detection circuit. It is possible to surely prevent the interruption of the operation and surely prevent the malfunction of the electronic circuit or the like which is supplied with power. (b) By connecting the storage circuit to the rectification output side of the rectification circuit, the capacitor can be always charged and placed without affecting the operation of the active smoothing filter circuit. (c) Utilizing the fact that the rectified voltage of the commercial frequency power supply is usually higher than the output voltage of the constant voltage power supply by one digit or more to store the capacitance of the capacitor of the energy storage circuit required for energy storage at the output side of the constant voltage power supply. It is possible to increase the practicality of the power supply circuit with guaranteed power supply at the time of instantaneous power failure by reducing the power consumption by two digits or more. As described above, the present invention can exert a remarkable effect in adding a power supply function during a momentary power failure to a power supply circuit for a constant voltage power supply having an active smoothing filter function that takes a sinusoidal current from a commercial frequency power supply. ..

[Brief description of drawings]

FIG. 1 is a circuit diagram of an embodiment of a constant voltage power supply circuit according to the present invention.

FIG. 2 is a circuit diagram showing a conventional power supply circuit together with an example of contents of a constant voltage power supply.

[Explanation of symbols]

 1 Commercial frequency power supply 10 Constant voltage power supply 20 Rectifier circuit 30 Active smoothing filter circuit 40 Energy storage circuit 41 Energy storage capacitor 42 Charging diode 43 Transistor switch for power supply at momentary power failure 50 Instantaneous power failure detection circuit DS Detection signal of instantaneous power failure detection circuit Va AC voltage of commercial frequency power supply Vr Rectified voltage of rectifier circuit

Claims (3)

[Claims] 1. A circuit for receiving an AC voltage from a commercial frequency power source and supplying a DC voltage to a constant voltage power source, wherein the rectifier circuit receives the AC voltage and the rectified output of the rectifier circuit is taken from the commercial frequency power source. An active smoothing filter circuit that controls the current in a sine wave shape, an energy storage circuit that charges a capacitor by the rectified output of the rectifier circuit, and an instantaneous blackout detection circuit that detects a short-time blackout of the commercial frequency power supply A power supply circuit for a constant voltage power supply, wherein a charging voltage of a capacitor is supplied from a power storage circuit to a constant voltage power supply when a power failure is detected by. 2. The power supply circuit for a constant voltage power supply according to claim 1, wherein a charging diode which is conductive only in a direction for charging the capacitor is incorporated in the energy storage circuit. 3. The circuit according to claim 1, wherein a diode prevents the current from flowing into the active smoothing filter circuit side while the power is being supplied from the energy storage circuit to the constant voltage power source. Power supply circuit for voltage power supply.