JP2001078460A - Uninterruptibe power source having backup circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain uninterrupted state by a battery of a DC output switching power source. SOLUTION: Respective phases of voltages U-W inputted into a converter are formed, so that two phases have the same polarities and the other phase has the reverse polarity at respective periods T1-T6, when one period T is divided into six equal period T1-T6. This uninterruptibe power source with a backup circuit using a battery consists of a capacitor 1 connected in parallel with an input power source, a primary input circuit formed so that a series circuit consisting of the primary coil 12 of a transformer 2 and a first switching element 3 are connected in parallel with the capacitor 1, a rectifier diode 4, a battery 6 with a reverse-current blocking diode 5, a secondary switching element 8, and a secondary output circuit formed so that a smoothing circuit consisting of a diode 9, a reactor 10, and capacitor 11 is connected in parallel with a secondary coil 13 of the transformer 2. The switching cycles of the first and second switching elements 3, 8 are synchronized by PWM control circuits 7, 12 and are controlled by independent duties respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an uninterruptible power supply having an AC / DC converter and a backup circuit using a battery.

[0002]

2. Description of the Related Art The circuit configuration of an uninterruptible power supply unit comprising an AC / DC converter using a battery as a backup power supply when an AC input power supply fails is shown in FIGS.
Is as shown in the block diagram of FIG.

[0003] In FIG. 4, a primary capacitor 116 of a transformer 102 has a parallel capacitor 101 and a switching element 10.
3 is connected, and the switch element 103 is connected to the control circuit 10.
4 is turned on / off. The secondary coil 117 is connected to a diode 105 forming a rectifier circuit, a diode 106 forming a smoothing circuit, a reactor 107 and a capacitor 108, and a battery 110 having a reverse current blocking diode 109 is connected in parallel. I have. Further, the switching element 111 and the diode 11
3, a DC chopper constituted by a smoothing circuit including a reactor 112 and a capacitor 114 is provided at a secondary output terminal. When the AC input power supply fails, DC power is supplied from the battery 110 via the reverse current blocking diode 109, and power controlled by the DC chopper 111 is supplied to the load.

FIG. 5 shows an AC / DC converter in which a separate winding is provided in a transformer, and an inverter circuit using a battery as an input power supply is formed in the separate winding, and serves as a backup circuit when an AC input power supply fails. That is, the primary capacitor 139 of the transformer 123 includes the parallel capacitor 1
21 and a switch element 124, and a reverse current blocking circuit 122 composed of a diode 126 and a transistor 127 are connected. Further, the reverse current blocking diode 128, the battery 129, and the switch element 131 are connected to the other winding 138, and constitute a backup circuit at the time of AC input power failure. The secondary coil 140 of the transformer 123 has
A rectifier diode 132 and a DC chopper configured by a smoothing circuit including a switch element 133, a diode 135, a reactor 136, and a capacitor 137 are provided. When the AC input power is cut off, the battery 129
The on / off control of the switch element 131 by a signal synchronized with the control circuit 125 supplies the energy to the secondary output side. At this time, since energy also flows back to the primary coil 139, a backflow prevention circuit 122 is provided to block the injection of the energy into the primary circuit. Also, during normal operation, energy is supplied not only to the secondary coil 140 but also to another winding 138 in accordance with the on / off control of the switch element 124 provided in the primary input circuit. 128 prevents backflow to the battery 129.

[0005]

In the circuit shown in FIG. 4, the input voltage of the DC chopper 111 is
0 must be higher than 0
The on / off duty of the switching is restricted to be small, and the efficiency is not improved. Further, since two sets of smoothing circuits are provided in the DC output circuit in an overlapping manner, the number of parts increases and the integration efficiency decreases.

In the circuit shown in FIG. 5, since a transformer of an AC / DC converter is provided with a separate winding having a battery and an inverter for converting a battery power supply into an alternating current, the size of the transformer and the circuit configuration become complicated. Instead, two sets of reverse current blocking circuits are required. Also,
In the circuit shown in FIG. 4, it is possible to supply the output independently in the circuit after the battery irrespective of the primary circuit, but in the circuit of FIG. 5, the components of the primary circuit and the battery-side inverter are provided. Damage results in system down.

[0007]

The secondary output circuit constituting the uninterruptible power supply is constituted by connecting a battery provided with a reverse current blocking diode and a DC chopper comprising a switch element and a smoothing circuit in parallel. The oscillation frequency of the first switch element provided in the next input circuit is synchronized with the oscillation frequency of the second switch element constituting the DC chopper, and when the primary input power supply fails, the battery is connected via the reverse current blocking diode. DC output from PW by DC chopper
By performing M control, a stable secondary output can be supplied. Also, when the primary input power is restored, the oscillation circuit operates in synchronization, so that the output is not affected by adjusting the pulse conduction width of the DC chopper. The secondary voltage of the transformer may be set to be slightly higher than the battery voltage, and can be used with almost the same duty both when driving the primary input power supply and when driving the battery. can avoid.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a circuit configuration of an uninterruptible power supply provided with a backup circuit according to the present invention. FIGS. 2 and 3 show voltage waveforms at respective components in FIG.

In FIG. 1, a parallel capacitor 1 and a first switch element 3 connected in series to a primary coil 12 are provided on a primary input side of a transformer 2. A rectifier diode 4 and a reverse current blocking diode 5 are provided on the secondary output side of the transformer 2.
, A second switch element 8 constituting a DC chopper, a diode 9, a reactor 10,
A smoothing circuit including a capacitor 11 is provided. In addition,
The oscillation frequencies of the first switch element 3 and the second switch element 8 are set so as to be synchronized, and the PWM control circuit 7
And 12 are controlled collectively.

Next, the operation characteristics of the uninterruptible power supply according to the present invention will be described with reference to FIGS. When the input power supply is normal, the oscillation periods of the first switch element 3 and the second switch element 8 are synchronized, and the points [A], [B], [C] and The voltage waveform at the point [D] is as shown in FIGS.

FIG. 2A shows the state of the first switch element 3.
At the output terminal [A] of the secondary coil 13 as the
FIG. 2B shows a voltage waveform of the rectifier diode 4.
Therefore, the rectified voltage waveform from point [A] and the reverse current blocking
Output voltage V from the battery 6 via the protection diode 5
_DC3B shows a composite voltage waveform at point [B]. FIG. 3 (c)
Is the voltage at the output terminal [C] of the second switch element 8
In the figure, ton indicates that the second switch element 8 is turned on.
Indicates the period. FIG. 2D shows an output terminal of the secondary output circuit.
Output voltage V in [D]₀And the following equation
Can be expressed. V₀= (Ton / T) · V_in  Where T is the switching period, V_inIs the transformer 2
It shows the output voltage in the lath direction.

Next, when the input power supply is interrupted,
The next output voltage is as shown in FIGS.
The voltage at the output terminal [A] of the secondary coil 13 is zero.
3 (a), and the point [B] shows the battery
Output voltage V from 6_DCAppears. As shown in FIG.
As described above, the ON period of the second switch element 8 is indicated by ton '.
The output voltage V at the point [D].₀Is V₀= (Ton '/ T) · V_DC  Becomes Secondary output voltage V regardless of input power supply₀To
In order to make it constant, when the second switch element 8 is turned on,
This can be achieved by changing the ratio.

[0013]

As described above, in the uninterruptible power supply according to the present invention, stable DC power can always be supplied by supplying DC power from the battery and PWM control of the DC chopper, even if the input power is interrupted. . AC /
During the DC operation, the transformer turns ratio can be set so that the peak value of the switching voltage waveform input to the DC chopper is slightly higher than the battery voltage, so that the transformer can be used with an efficient and appropriate duty. The redundant smoothing circuit and the reverse current blocking circuit provided in the converter according to the prior art become unnecessary, and the transformer 1 which causes a system down is not required.
By reducing the number of secondary circuit components, a circuit having a simple circuit configuration, excellent reliability, and high conversion efficiency can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a circuit configuration of an uninterruptible power supply provided with a backup circuit according to the present invention.

FIG. 2 is a waveform diagram.

FIG. 3 is a waveform diagram.

FIG. 4 is a block diagram showing a circuit configuration of a conventional uninterruptible power supply.

FIG. 5 is a block diagram showing a circuit configuration of a conventional uninterruptible power supply.

[Explanation of symbols]

 1,11 capacitor 2 transformer 3,8 switch element 4,5,9 diode 6 battery 7,12 PWM control circuit 10 reactor

Claims (1)

[Claims] A capacitor connected in parallel to an input power supply;
A primary input circuit configured by connecting a series circuit including a primary coil of a transformer and a first switch element in parallel to the capacitor; a rectifier circuit including a diode; a battery including a reverse current blocking circuit; And a DC chopper comprising a switching element and a smoothing circuit, connected in parallel with a secondary coil of a transformer. The pulse output of the transformer is directly PW
M control and at the time of the primary input power failure,
The DC output from the battery is synchronized with the first switch element and the pulse conduction width of the second switch element is adjusted so that PW
An uninterruptible power supply device equipped with a backup circuit, characterized in that M control is continued and stable power supply is performed regardless of the presence or absence of a primary input power supply.