Un-interruptible power supply

Details Un-interruptible power supply Un-interruptible power supply

2001-04-03

2002-11-12

Toatley, Gregory (Department: 2838)

Electricity: battery or capacitor charging or discharging

Battery or cell charging

With detection of current or voltage amplitude

C307S066000

Reexamination Certificate

active

06479970

ABSTRACT:

FIELD OF INVENTION
This invention relates to the field of power supplies or power converters and more particularly to on-line, isolated solid state sources with battery back up in which the input, the output, and battery voltages are significantly different.
BACKGROUND OF THE INVENTION
FIGS. 1 and 2
show related designs of isolated un-interruptible power supplies with battery back up in which two transformers are used to achieve isolation. In the circuit of
FIG. 1
, ac input voltage from an external mains source is rectified by a function represented by the FIRST CONVERTER BRIDGE RECTIFIER block and filtered by a function represented by the FIRST L/F FILTER block, a low frequency filter. A first high frequency inverter represented by the FIRST H/F INVERTER block uses a first transformer T
1
to provide power via a high frequency rectifier represented by a H/F RECTIFIER block and H/F FILTER to a battery charging bus identified as BATT. A low frequency inverter represented by the L/F INVERTER block uses a second transformer T
2
to provide sinusoidal power to the load via a second low frequency filter represented by SECOND L/F FILTER block. The second transformer T
2
provides galvanic isolation from the load to the battery and the low frequency inverter. Since the output power from the second transformer T
2
is at the output line frequency of 50-60 Hz, the second transformer is large and heavy.
The isolated un-interruptible power supply of
FIG. 2
uses a first high frequency inverter represented by the H/F INVERTER block to drive a first transformer T
3
. The secondary of transformer T
3
provides power via the FIRST H/F RECTIFIER and H/F FILTER blocks to a battery charging buss designated by the legend BATT. Power is provided from the BATT buss to a second high frequency inverter represented by the SECOND H/F INVERTER block. The battery clamps or limits the voltage on the BATT buss. The secondary of T
4
drives a high frequency rectifier and filter to provide one or more high voltage rails. Transformer T
4
is a small and light high frequency component.
The function represented by the L/F INVERTER block of
FIG. 2
produces a 60 Hz output source of power using a solid state dc-to-ac drive. The L/F INVERTER provides the 60 Hz output by pulse width modulating power off the dc rails from the H/F RECTIFIER & FILTER, through an inductor within the L/F INVERTER. The function represented by the L/F INVERTER block copies the required sinusoidal waveform without regard to the current required, subject to the instantaneous current required at any time remaining within predetermined limits.
The circuit of
FIG. 2
offers a saving over the circuit of
FIG. 1
in that the first circuit uses a low frequency second transformer T
2
and the circuit of
FIG. 2
uses a high frequency second transformer T
4
which would be smaller and lighter for an equivalent power output capability. Both circuits have a low frequency inverter which has at least one inductor (not shown).
Some on-line sources use a larger stack of batteries to form a high voltage battery bus to eliminate the need for a separate boost section to boost the battery stack voltage up Some on-line sources use a larger stack of batteries to form a high voltage battery bus to eliminate the need for a separate boost section to boost the battery stack voltage up to the dc rail voltages which might be +/−200 Vdc. The battery voltage can be directly used to feed the critical load. However, a smaller battery stack with a lower battery bus voltage, i.e. 48 Vdc. The lower battery bus is believed to be preferred because a battery stack with fewer cell s in series is believed to be more reliable and more easily maintained.
The systems of
FIGS. 1 and 2
are continuous on-line system that keeps the batteries connected while operating, and pass the total power consumed including battery charging power, through the first transformer T
1
or T
3
. Load power alone flows through the second transformer T
2
, or T
4
. The combined power, passing through the T
1
or T
3
transformer, increases the required power rating for the first transformer. The volume of the two input transformers as well as their size and weight exceed the volume, size and weight of the single transformer required for the single transformer used in the subject invention.
BRIEF SUMMARY OF THE INVENTION
The invention, UN-INTERRUPTIBLE POWER SUPPLY(UPS) reduces the system cost, volume, and weight by using a single three winding high frequency power transformer instead of the two transformers used by conventional systems. Input, output and battery sections are respectively connected via the three power windings of the high frequency transformer isolating the sections from each other and establishing galvanic isolation between the output load and the input power source.
FIG. 3
shows the invention un-interruptible power supply within phantom block
10
. 50-60 Hz ac Mains power from voltage source
12
is applied at input terminals
14
of I/P FILTER (input power filter)
16
. The I/P FILTER
16
filters and passes the power to rectifier
18
providing unregulated and unfiltered dc voltage to a low-pass filter
20
. The output of the low-pass filter
20
is an unregulated dc source
22
that is coupled to the input
24
of the INPUT INVERTER
26
which typically uses an H-Bridge inverter circuit to drive the primary winding N
1
of transformer T
5
. The combination of elements within phantom box
28
is represented as a dc voltage source
22
at input inverter input
24
in
FIGS. 4
,
5
and
6
.


REFERENCES:
patent: 5440179 (1995-08-01), Severinsky
patent: 6157168 (2000-12-01), Malik
patent: 6218744 (2001-04-01), Zahrte et al.

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