JPS6016171B2 - DC power supply - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a DC power supply device most suitable for compensating for instantaneous power outages.

Conventional DC power supplies are generally configured to convert AC supplied from an AC power supply 1 into DC using a rectifier 2, as shown in FIG. 1, and supply DC power to a load 4 via a smoothing capacitor 3. There is.

In such a DC power supply, the capacity of the smoothing capacitor 3 may be increased to compensate for instantaneous voltage drops or instantaneous power outages, and this may also be used as a capacitor for compensating for instantaneous power outages. By the way, the second form of instantaneous power outage is
It can be roughly divided into three types shown in Figures A, B, and C.

The waveforms in FIG. 2 are explanatory representations of the voltage Vin at the output stage of the rectifier 2 in the case where the capacitor 3 does not have a compensation function, without considering ripple current. Figure 2A shows a power outage mode in which the voltage Vin becomes low at time t, gradually increases, and returns to the normal state at t2, and Figure 2B
Figure 2C shows a power outage mode in which the zero volt state is maintained from time t to t2, and in Figure 2C, the voltage gradually increases from t2 after the drop volt state continues from time t to t2, and returns to normal state at time t. This shows the type of power outage that returns to . In a conventional power failure compensation circuit in which the capacity of the smoothing capacitor 3 is simply increased, the power failure conditions shown in Figure 2 A, B, and C are compensated as shown in Figure 3 A, B, and ○. As the capacitor 3 discharges, the output voltage Vo decreases.

Therefore, in the case of a load that requires a stabilized voltage, the capacitance of the capacitor 3 must be increased to reduce the voltage drop. As a result, the cost and size of the device have increased. SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a DC power supply device that can reduce voltage changes during momentary power outages or significant voltage drops, and that can be made smaller and lower in cost. .

To achieve the above object, the present invention includes a rectifier connected to an AC power source where there is a risk of instantaneous power outage or voltage drop where the power supply voltage is below a predetermined value, and a pair of rectifiers for supplying power from the rectifier to a load. a DC power line, a reverse current blocking circuit such as the diode 27 of the embodiment connected in series with one of the DC power lines of the pair of DC power lines, and an output side of the reverse current blocking circuit. a first compensation capacitor, one end of which is connected to the one DC power line, and 1 between the other end of the first compensation capacitor and the other DC power line of the pair of DC power lines; a compensation capacitor charging circuit, such as the high resistance 17 of the embodiment, connected to the one DC power supply line on the input side of the reverse current blocking circuit and the other end of the first compensation capacitor; a second compensation capacitor connected between the one DC power supply line and the other DC power supply line on the input side of the reverse current blocking circuit; A smoothing capacitor connected between the one DC power line and the other DC power line on the output side of the circuit, and detecting that the terminal voltage of the smoothing capacitor has fallen below a predetermined level. and voltage detection for controlling the transistor so as to adjust and superimpose the voltage of the second compensation capacitor on the voltage of the first compensation capacitor during a period in which it is detected that the voltage is below the predetermined level. a control circuit, which charges the first compensation capacitor and the smoothing capacitor via the rectifier and the reverse current blocking circuit when the AC power supply is normal, and supplies power to the load; The second compensation capacitor is charged via the rectifier, and during a period when the terminal voltage of the smoothing capacitor becomes equal to or lower than the predetermined level, the voltage of the first compensation capacitor and the second compensation capacitor are charged. The present invention relates to a DC power supply device configured to control the transistor so that the sum of the voltage of the capacitor and the adjusted voltage falls within a permissible range, and supply the sum of the voltage to the load. According to the above invention, the following effects can be obtained.

During a momentary power outage or voltage drop and during recovery, the rectifier, the second compensation capacitor, the transistor, and the first
Since the first compensation capacitor and the second compensation capacitor are connected in series, and the voltage is adjusted by the transistor, the voltage drop of the first compensation capacitor can be well compensated for by the voltage of the second compensation capacitor, and the load There will be less variation in the voltage supplied to the That is, if the first compensation capacitor and the second compensation capacitor are simply connected in series, the voltage between the pair of DC power supply lines will be doubled, but in the present invention, the voltage is adjusted using a transistor. No double voltage condition occurs. {o} During a complete power outage period when the input and output of the rectifier are zero, the series circuit consisting of the first and second compensation capacitors is connected in parallel to the smoothing capacitor by turning on the transistor, so all capacitors are This allows power to be supplied to the load, and significant voltage drops can be suppressed.

However, since substantially all of the charge in the first compensation capacitor can be used during voltage compensation, the capacitance of the capacitor can be reduced, and the device can be made more compact.

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 4 is a circuit diagram showing a DC power supply device with an instantaneous power failure compensation circuit according to the present invention.

This DC power supply system converts AC supplied from an AC power supply 11 into DC using a rectifier 12, and converts this into DC using a smoothing capacitor 1.
It has a main circuit that supplies the load 14 via 3, and
A first compensation capacitor 8 connected between the positive power line 15 and the negative power line 16 via a high resistance 17
further includes a resistor 17 and a first compensation capacitor 8
A transistor 21 having the function of a switch and a voltage regulating circuit is connected between a point 19 between the rectifier 12 and an output point 20 of the rectifier 12. This transistor 21 is controlled by a control circuit 22. The control circuit 22 has an output voltage Vo
a comparison circuit 23 that generates a comparison output by comparing the voltage with a separately determined reference voltage; a mirror tooth wave generation circuit 25 that generates a chain tooth wave as shown in 24; and an oven 26 whose input is the output of the wave generating circuit 25. A diode 27 connected in series with the power supply line 15 between the output point 20 of the rectifier 12 and one end of the first compensation capacitor 8 forms a reverse current blocking circuit and is non-conducting during a power outage. This is a suitable state, and a conductive state under normal conditions.

A second compensation capacitor 28 is connected between the positive power line 15 and the negative power line 16 of the output stage of the rectifier 12.

A smoothing reactor 29 is connected between the transistor 21 and the point 19.

This diode is a protection diode for the transistor 21, and prevents a high voltage from being applied to the transistor 21 when it is turned off.

The load 14 in this circuit is a load such as a computer equipped with a voltage stabilization circuit. AC power supply 11 with the above circuit
When AC power is being normally supplied from the load 14, DC power is supplied to the load 14 via the rectifier 12 and the smoothing capacitor 3. At the same time, the first compensation capacitor 18 is charged to approximately the power supply voltage Vin via the resistor 17, and the second compensation capacitor 28 is also charged to approximately the power supply voltage Vin.
is charged. At this time, the output Vo is maintained at a predetermined voltage level Vo, as shown in FIG. When the output voltage Vo is at the voltage level Vo, a low level output is generated from the comparator circuit 23. That is, a comparison output having a level as shown by the dotted line 31 in FIG. 5A is generated and applied to the oven amplifier 26. Therefore, since the mirror-tooth wave 24 is not crossed, a signal capable of turning on the transistor 21 is not generated from the amplifier 26, and the transistor 2
1 is kept off. As shown in FIG. 6, a momentary power outage occurs on the shipboard, and the power supply voltage Vin at the output point of the rectifier 12 becomes the state shown by the dotted line in FIG. In the case of a power outage mode, the power supply voltage Vin is no longer supplied, so that the output voltage yo is provided by the discharge of the smoothing capacitor 13 and the second compensation capacitor 28.

However, the output voltage Vo decreases with discharge, and becomes Vo2 from Vo at t2. When the output voltage drops to Vo2, the output of the comparison circuit 23 rises from the level shown by the dotted line 31 in FIG. 5A to the level shown by the solid line 32, for example. Therefore, a state occurs where the level is higher than that of the sawtooth wave 24, and a signal that turns on the transistor 21 is generated from the output of the amplifier 26. FIG. 5B shows the on/off state of the transistor 21. When the transistor 21 is turned on, the voltage Vc of the second compensation capacitor 28 passes through the transistor 21 and is controlled, and becomes the compensation voltage Vx after passing through the smoothing reactor 29. Furthermore, since a discharge circuit for the first compensation capacitor 18 is also formed,
This capacitor voltage Vco and compensation voltage Vx are added to form an output voltage Vo. That is, a closed circuit consisting of the second compensation capacitor 28, the transistor 21, the reactor 29, the first compensation capacitor 18, and the load is substantially formed, thereby providing the output voltage Vo. As the power outage progresses, the voltage Vc of the first compensation capacitor 18
Since o decreases, transistor 21 is controlled to increase Vx. As a result, the output voltage Vo becomes Vo
It is kept at a level of 2. When the power outage is restored at time t3 and the power supply voltage yin is applied, the diode 27 enters the forward bias state, and the power supply voltage V at the level of Vo,
in appears as the output voltage Vo. When the output voltage Vo at the level of Vo, is generated, the dotted line 31 in FIG.
As shown in , the output level of the comparator circuit 23 is a sawtooth wave 24
Since the voltage becomes lower, no on signal is applied to the transistor 21, and the transistor 21 is kept in the off state. As a result, the first compensation capacitor 18 and the second compensation capacitor 28 are separated, and each capacitor 1
8 and 28 are charged with the power supply voltage Vin to prepare for the next power outage. According to this device, as is clear from the voltages Vco and Vc of the first and second compensation capacitors 18 and 28 in FIG. It is possible to supply Vo2 to

Therefore, the utilization rate of the charges in the capacitors 18 and 28 becomes extremely high, and the capacitance of the capacitors can be made smaller than before. That is, when compensating for the same power outage time between the present invention and the conventional method, the sum of the capacities of the smoothing capacitor 13 and the first and second compensation capacitors 8 and 28 is the capacitance of the conventional capacitor. Smaller is better. Furthermore, if the capacitor capacity is the same as the conventional one, the power failure compensation time will be longer. FIG. 7 shows the voltage relationship when the power outage of the form shown in FIG. 2C is compensated for.

If a power outage occurs later in Fig. 7, the smoothing Li factor 13 and the second compensation capacitor 2
8 gives the output voltage Vo. Thereafter, the output voltage decreases due to discharge, and when it reaches the level Vo2 at t2, the transistor 21 is turned on as in the case of FIG. 6, and the first compensation capacitor 8 and the second compensation capacitor 8 are The output voltage is applied based on the capacitor 28. At this time, the power supply voltage Vin has already risen, but the voltage V of the second compensation capacitor 28
c, so it does not contribute to the output voltage Vo. When the voltage Vc of the second compensation capacitor 28 becomes equal to the power supply voltage Vjn at time t3, the capacitor 28 can no longer be discharged, so after t3, the power supply voltage Vin becomes the compensation voltage Vx via the transistor 21 form. When the duty ratio reaches 4 and the power supply voltage Vjn becomes higher than the minimum allowable level Vo2, the diode 27 becomes conductive, and the power supply voltage Vin appears as it is at the output voltage Vo. As a result, from the comparison circuit 23, the dotted line 3 in FIG.
A signal with a level indicated by 1 is generated, and the signal to turn on the transistor 21 is no longer applied from the obeamp 26.
Transistor 21 is turned off. When the time ratio reaches 3, the power supply voltage Vin reaches the normal level Vo, and normal power supply starts. Further, from t4 when the transistor 21 is turned off, charging of the first compensation capacitor 18, which has been discharged to almost zero, starts. As is clear from the above, the output voltage Vo can be maintained at or above the minimum allowable level Vo2 until all the charges in the first compensation capacitor 18 are discharged.

Therefore, the power outage compensation period becomes longer than before. Also, by keeping the power outage compensation period the same, the capacitor capacity can be reduced. Incidentally, even in the power outage mode shown in FIG. 2A, it is possible to compensate for the power outage in the same manner as in the power outage mode shown in FIG. 2C.

Therefore, according to this device, in all types of power outages, the capacitor can be effectively used to compensate for power outages. Although the embodiments of the present invention have been described above, the present invention is not limited to the above-mentioned embodiments, and can be further modified. For example, instead of the transistor 21, another element may be connected. Furthermore, the control form for obtaining the desired voltage Vx may be changed. Further, the control circuit 22 may be provided with a power failure detection circuit and a voltage detection circuit for output voltage control independently. Alternatively, a switch circuit and a voltage adjustment circuit may be provided in place of the transistor 21, and the switch circuit may be turned on only during a power outage period, and the desired voltage yx may be obtained by the voltage adjustment circuit during this period. Also, instead of the diode 27, another switching element may be used to prevent reverse current. It is also possible to compensate for voltage drops other than power outages. Also, connect the substitute switch circuit of resistor 17,
The switch may be turned on only when charging.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing a conventional DC power supply device, Fig. 2 is a waveform diagram illustrating the mode of power outage using power supply voltage Vin, and Fig. 3
The figure shows the status of power outage compensation by the circuit in Figure 1 with the output voltage yo
FIG. 4 is a circuit diagram showing a DC power supply device according to an embodiment of the present invention, FIG. 5 is a waveform diagram explaining the states of each part in FIG. 4, and FIG. 6 is a waveform diagram shown in FIG. 2. Waveform diagram 7 explanatoryly showing the state of each part in FIG. 4 in the power outage mode shown in B.
The figure is a waveform diagram illustratively showing the state of each part in FIG. 4 in the power outage mode shown in FIG. 2C. In the symbols used in the drawings, 11 is an AC power supply, 12 is a rectifier, 13 is a smoothing capacitor, 14 is a rice bowl, 15 and 16 are power lines, 17 is a resistor, and 18 is for the first compensation. 21 is a transistor, 22 is a control circuit, 27 is a backflow blocking diode, and 28 is a second compensation capacitor. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7

Claims (1)

[Claims] 1. A rectifier connected to an AC power source that is likely to cause a momentary power outage or voltage drop where the power source voltage falls below a specified value;
A pair of DC power lines for supplying power from the rectifier to a load, a reverse current blocking circuit connected in series to one of the DC power lines of the pair of DC power lines, and an output side of the reverse current blocking circuit. a first compensation capacitor, one end of which is connected to the one DC power supply line, and the other end of the first compensation capacitor connected to the other DC power supply line of the pair of DC power supply lines. and a transistor connected between the one DC power supply line and the other end of the first compensation capacitor on the input side of the reverse current blocking circuit. , a second compensating capacitor connected between the one DC power supply line and the other DC power supply line on the input side of the reverse current blocking circuit; A smoothing capacitor connected between one DC power supply line and the other DC power supply line, and detecting that the terminal voltage of the smoothing capacitor has become below a predetermined level, and that the voltage is below the predetermined level. a voltage detection and control circuit that controls the transistor so as to adjust and superimpose the voltage of the second compensation capacitor on the voltage of the first compensation capacitor during a period when the voltage of the first compensation capacitor is detected; When the AC power supply is normal, the first
charging the compensation capacitor and the smoothing capacitor, supplying power to the load, and charging the second compensation capacitor via the rectifier, so that the terminal voltage of the smoothing capacitor is equal to or lower than the predetermined level. During the period when the voltage of the first compensation capacitor and the voltage of the second compensation capacitor are adjusted, the transistor is controlled so that the voltage of the sum of the voltage of the first compensation capacitor and the voltage of the second compensation capacitor is within a permissible range. A DC power supply configured to supply voltage to the load.