JPH10322934A - Power supply unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power supply unit which can increase the period of power supply to a load, even in a prescribed period at the time of instantaneous power failure or after power supply is turned off, and is capable of attaining reduction in size and cost. SOLUTION: A main capacitor C is disposed between the output terminals of a bridge-rectifying circuit 1 which rectifies alternating current. A capacitor part 2 is constituted by disposing auxiliary capacitors C1 to Cn and switches SW1 to SWn for turning on/off a current to C1 to Cn in parallel to the main capacitor C. A switch change-over control circuit 4 is disposed, which turns on by detecting the rectifying level of the capacitor part 2, the switches SW1 to SWn if it is below a prescribed level, and turns off the switches SW1 to SWn when it is above the prescribed level. Therefore, when the rectifying level is below the prescribed level, the electrostatic capacity of the capacity part 2 increases, and an electric charge of more than a certain amount can be stored, so that it is possible to supply power to the load longer than a fixed time, even when an instantaneous power failure occurs.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply including a rectifying / smoothing circuit.

[0002]

2. Description of the Related Art In a power supply device including a rectifying / smoothing circuit mounted on a copying machine, a printer, a facsimile, a computer, and other electronic and electric devices, an electric power supplied to a load at a momentary power failure or for a predetermined time after the power is turned off. It is required that the supply be performed for a certain period of time. In this case, it is necessary to form a rectifying / smoothing circuit with a large-capacity smoothing capacitor.

For example, when an AC input to a power supply device is in a wide range (for example, AC85V to AC264V), a rectified output of a rectifying and smoothing circuit included in the power supply device is DC and DC.
120V to 380V DC. The rectified output V of the rectifying / smoothing circuit, the smoothing capacitor C, the power W to the load,
The relationship between the power supply time S and (1/2) CV ² = W
S... (1) and the DC 120 at which the rectified output becomes the minimum value
When the capacitance of the smoothing capacitor required at V is C _a , the capacitance of the smoothing capacitor required at 380 V DC at which the rectified output has the maximum value is C _b , and when W and S are constant, C _a and C are obtained from Expression (1). The magnitude relationship of _b is C _a ≫C _b .

Accordingly, the capacity of the smoothing capacitor of the rectifying / smoothing circuit included in the power supply device corresponding to a wide range is the required value of the smoothing capacitor C _a (2) required when the rectified output becomes the minimum value. .

On the other hand, since the voltage applied when the rectified output reaches the maximum value is 380 V, the withstand voltage required for the smoothing capacitor in the case of a wide range input is 380 V _DC .
(3) The above is required.

[0006] Therefore, the above-mentioned power supply device has the above (2).
(3) a large smoothing capacitor capacitance that is proportional to _{C a × 380 (C a »C} b) from the equation becomes necessary.

[0007]

However, the size (volume) of the smoothing capacitor (eg, electrolytic capacitor)
Is proportional to the capacitance × withstand voltage, the size of the large-capacity smoothing capacitor becomes large. Further, since the cost of the smoothing capacitor is proportional to the size, this large-sized smoothing capacitor is costly. Therefore, when the power supply device is configured with the large-sized smoothing capacitor, there is a problem that the power supply device is increased in size and cost is increased.

[0008] Therefore, the present invention provides a method for controlling a power failure or an instantaneous power failure.
It is another object of the present invention to provide a small and inexpensive power supply device that can extend the power supply time to a load even during a predetermined time after the start of the power supply.

[0009]

According to the present invention, there is provided a power supply apparatus comprising: a rectifier circuit for rectifying a supplied alternating current; and a basic capacitor disposed between output terminals of the rectifier circuit. An auxiliary capacitor for the basic capacitor, and a capacitor portion in which a switch for turning on and off the power supply to the auxiliary capacitor are arranged in parallel, and a rectification level is detected. And a switch switching control circuit for controlling the switch to be turned off sometimes.

Therefore, when the rectification level is lower than a predetermined level, the switch is turned on, the auxiliary capacitor is energized, and the capacitance of the capacitor section is increased.

When the rectification level is higher than a predetermined level, the switch is turned off and only the basic capacitor is energized.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a circuit diagram of the power supply device of the present embodiment. In this embodiment, it is assumed that a wide-range AC is input as an AC input.

In FIG. 1, a bridge rectifier circuit 1 as a rectifier circuit is connected to an AC power supply, and a capacitor unit 2 as a capacitor unit is connected between output terminals of the bridge rectifier circuit 1.
The output of the capacitor unit 2 is guided to a DC / DC conversion unit 3 for converting the output to a desired potential, and S
It is supplied to the W switching control circuit 4.

The bridge rectifier circuit 1 includes diodes D ₁ to
Connect the D ₄ like a bridge which performs full-wave rectification and the DC output by rectifying an AC input received.

The capacitor section 2 includes a capacitor C as a basic capacitor and a plurality of capacitors C ₁ ... C as auxiliary capacitors connected in parallel with the capacitor C.
and _n, corresponding to each of the example C ₁ ... C _n, and are arranged in the auxiliary capacitor C ₁ ... C _n in series, a switch SW ₁ to SW _n that off the energization of the C ₁ ... C _n, from It is configured. The capacitor unit 2 smoothes and holds the output subjected to the full-wave rectification.

[0016] Also, the capacity and the capacity of the auxiliary capacitor C ₁ ... C _n of the basic capacitor C, V ₁ rectified output is minimum value
(E.g., 120 V), the required capacitance of the smoothing capacitor is C _a , and the rectified output is V ₂ (e.g., 380
If the capacity of the V) at the time required the smoothing capacitor and C _b,
V ₂ × C _b (for example, 380 ×
The capacity of the C _b), the auxiliary capacitor C ₁ ... C _n are V ₁ × (C _a
−C _b ) (for example, 120 × (C _a −C _b )).

[0017] The switch SW ₁ ... SW _n is composed of, for example, by a relay and a semiconductor switch, for example, the switches SW ₁ ... SW _n accordance with the rectified output level of the capacitor portion 2
The capacitor C ₁ ... C _n are connected in parallel by opening and closing is performed to increase or decrease the total capacitance of the capacitor portion 2.

The DC / DC converter 3 converts the rectified output of the capacitor 2 into a desired voltage.

The SW switching controller 4 controls opening and closing of SW ₁ to SW _n of the capacitor unit 2 in accordance with the level of the rectified output of the capacitor unit 2. For example, based on V ₃ , V ₄ ,... V _n (V ₃ <V ₄ <... <V _n ) existing between V ₁ and V ₂ , when V ₃ or less, all switches SW ₁
Close ~ SW _n . V ₄ or less of the time, the switch SW ₁ ~
Close SW _n-1 . In addition, when more than V _n is, open all of the switches SW ₁ ~SW _n.

The operation of the above configuration will be described below. The minimum value of the rectified output is V ₁ , the maximum value of the rectified output is V ₂ , V ₁ and V ₂
Are defined as V ₃ ... V _n . The input AC input is rectified by the bridge rectifier circuit 1 and the rectified output is V
₃ or less, the switches SW ₁ to SW ₁
SW _n are all turned on. Therefore, the auxiliary capacitors C ₁ .
Since C _n are all energized, the capacitance of the capacitor portion 2 is increased, the greater the electric charge. Thus, even if an instantaneous power failure occurs at the time of AC input such that the rectified output becomes a minimum value, power can be supplied to the load for a certain period of time or more.

Further, when the commutation level is above V _n, the switch SW ₁ to SW _n of the capacitor portion 2 is because all turned off, only the basic capacitor C is energized. Therefore,
When the rectified output of the maximum value to become such AC input is not energized the auxiliary capacitor C ₁ ... C _n. As a result, a rectifying and smoothing circuit can be designed by adjusting only the basic capacitor to the maximum value of the AC input, and the power supply device can be downsized.
In addition, the cost of the power supply device can be reduced.

In the present embodiment, the switching of the SW switching control circuit 4 is performed by detecting the rectified output after smoothing. However, as shown in FIG. The control circuit 4 may be switched.

As shown in FIG. 3, the connection between the auxiliary capacitors C ₁ ... C _n and the switches SW _{1 to} SW _n may be configured upside down in this embodiment.

In this embodiment, the switches SW ₁ -S
W _n and a plurality of auxiliary capacitors C ₁ ... C _n are used, but one switch SW and one auxiliary capacitor may be used.
One switch SW as shown in FIG. 4, may be configured of a plurality of auxiliary capacitors C ₁ ... C _n.

Although the present embodiment describes a case where a wide-range AC is input as an AC input, the same effect can be obtained for a single range of a 100 V system or a 200 V system.

[0026]

As described above, according to the power supply device of the present invention, a rectifier circuit for rectifying the supplied AC and a basic capacitor are arranged between the output terminals of the rectifier circuit. An auxiliary capacitor, and a capacitor section in which a switch for turning on and off the auxiliary capacitor is arranged in parallel, and a rectification level is detected. The switch is turned on when the level is lower than a predetermined level, and is turned off when the level is higher than a predetermined level. And a switch switching control circuit that controls the switch to be turned on when the rectification level is equal to or lower than a predetermined level.
Since the auxiliary capacitor is energized, it is possible to store more than a certain amount of charge in the capacitor unit.For example, even when an instantaneous power failure occurs at the time of AC input that results in a rectified output of a predetermined level or less, the power supply time to the load can be reduced. It has the effect that it can be lengthened.

When the rectification level is higher than a predetermined level, the switch is turned off, and only the basic capacitor C is energized. Therefore, for example, a rectifying / smoothing circuit can be designed in accordance with the value of an AC input at which only a basic capacitor has a rectified output of a predetermined level or more, and a small and inexpensive power supply device can be provided.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a power supply device (example).

FIG. 2 is a circuit diagram of a power supply device (an embodiment in which a SW switching control circuit is switched by an AC input before rectification).

FIG. 3 is a circuit diagram of a power supply device (an embodiment in which the arrangement of auxiliary capacitors and switches is modified).

FIG. 4 is a circuit diagram of a power supply device (an embodiment in which a capacitor section is configured by one switch and a plurality of auxiliary capacitors).

[Explanation of symbols]

1 ... bridge rectifier circuit (rectifying circuit), 2 ... capacitor section, C ... base capacitor, C ₁ -C _n ... auxiliary capacitor,
SW _{1 to} SW _n ... switches, 3 ... DC / DC converter, 4 ...
SW switching controller (switch switching control circuit)

Claims (2)

[Claims] A rectifier circuit for rectifying the supplied alternating current; and a basic capacitor disposed between output terminals of the rectifier circuit.
An auxiliary capacitor for this basic capacitor, and a capacitor section in which a switch for turning on and off the power supply to this auxiliary capacitor are arranged in parallel.A rectification level is detected. And a switch switching control circuit for controlling the switch to be turned off at the time of the power supply. 2. The power supply device according to claim 1, wherein the capacitor section has a plurality of the auxiliary capacitors.