Title of Invention

HIGH EFFICIENCY UNINTERRUPTIBLE POWER SUPPLY

Abstract

The high efficiency uninterruptible power supply will take the reserved power from the battery through the high frequency power DC/AC converter. Therefore, the bulky, low frequency transformer can be avoided. The ac voltage then will be rectified to dc voltage and discharged to load, preferably a personal computer. Although, power factor of the load is not equal to 1, it can be corrected so that the power factor becomes 1. Before the UPS outputs dc voltage to the load, a load characteristic analysis means provided therein will analyze whether the load can receive dc voltage supply. If the UPS according to this invention is used with the load, such as a personal computer or the like, the entirely efficient will be higher. It is able to work longer during the power shortage. It is also smaller and lighter when compare to other UPS using the same size of the battery.

Full Text

FORM 2 THE PATENTS ACT, 1970 (39 of 1970) COMPLETE SPECIFICATION [See section 10; Rule 13] HIGH EFFICIENCY UNINTERRUPTIBLE POWER SUPPLY; NATIONAL SCIENCE AND TECHNOLOGY DEVELOPMENT AGENCY A CORPORATION ORGANIZED AND EXISTING UNDER THE LAWS OF THAILAND, WHOSE ADDRESS IS 111 PAHOLYOTHIN RD., KLONG 1, KLONG LUANG, PATHUMTHANI 12120, THAILAND. THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE NATURE OF THIS INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFOMED. TITLE High Efficiency Uninterruptible Power Supply TECHNICAL FIELD The present invention is related to power supply; more particular to uninterruptible power supply having DC output voltage. BACKGROUND OF THE INVENTION In general, the uninterruptible power supply powered from a battery, so called "Standby UPS", usually have capacity less than 3 kVA. As shown in FIG. 1, an UPS consists of a battery charger which transform energy from electric source storing into the battery, a low frequency power converter a low , frequency transformer and an automatic switch. When there is a shortage of power from household power source, the battery supplies the low frequency power converter to generate the AC voltage having frequency equal to main voltage frequency (50 Hz or 60 Hz). This AC voltage from the low frequency power converter is not in a complete sine-wave shape and is raised to the same level of the main voltage source. Then, the AC Voltage from the low frequency transformer is fed to load via the automatic switch. The automatic switch is switched automatically between main voltage source and the low-frequency transformer in response to the condition of the main power source. The drawback of the prior art is that the low-frequency transformer is usually bulky and heavy. Furthermore, the transfer time, e.g. switching time using for transition from main power source to battery, is relatively high. Typically it is around 4-10 milliseconds after the main power shortage. Therefore, interruption of electrical power might cause failure in electrical devices, especially in devices that are sensitive to voltage variation, such as computer. Furthermore, the power supply in personal computers and display monitors are mainly comprise of rectifiers and capacitors resulting in power factor less than 1 (mostly at 0.6). This low power factor characteristic reduces overall efficiency of the power supplies. For example, in order to supply electric power to a 300-W load, a power supply having power factor of 0.6 has to feed 2 complex power of 500 VA to the load. This increases its overall size and weight. And the output of the supply is distorted so that the current waveform is approximately square rather than sinusoidal causing energy loss in the transformer and harmonic distortion (sometimes up to 40%). Moreover, the harmonic frequency often disturbs operation of the display monitor and other peripheral equipments. In present state-of-the-art, UPS is built without the bulky and heavy low-frequency transformers in order to reduce size and weight. As shown in FIG. 2, a low-frequency transformer is replaced by a high-frequency DC/AC converter which will convert direct current from battery (or battery charging means) into high frequency alternating current and then the alternating current is fed to a high-frequency transformer, which is smaller, lighter, and more efficient than a typical equally powered low-frequency transformer. The high-frequency transformer outputs high potential alternative current that is I then rectified by a rectifier circuit. From this point, the high potential direct current is converted again to low-frequency alternating current i.e. 50 Hz, by a low-frequency DC/AC converter. Despite the merit of lightness, however, there are still some energy losses in the last stage low-frequency DC/AC converter circuit. Due to a low P.F. characteristic of the power supply, designing such power supply requires at least a pair of a big switching means using in the converter circuit, thus increasing the manufacturing cost. Traditional UPS (Uninterruptible Power Supply) systems having power factor correction circuit (PFC) to improve the power factor presented to the main lines. Examples of such system are US patent No. 5,901,057 "Uninterruptible | power supply with fault tolerance in a high voltage environment"(BRAND, et al.) issued on May 4,1999, US patent No. 5,532,918 "High power factor switched DC power supply" (MAYRAND et al.) issued on July 2,1996, US patent No. 5,764,504 "(BRAND, et al.) issued June 9, 1998, US patent No. 5,691,890 "Power supply with factor correction circuit" (HYDE) issued on Nov. 25,1997 and a Great Britain Patent GB 2 287 843 "Off-line uninterruptible powersupply". 3 SUMMARY OF THE INVENTION The UPS system in this invention advantageously intents to provide a power supply having a power factor near 1 output, high effciency small and light weight, and to produce less interference. Further, the UPS can be selected to supply DC voltage or AC voltage accordingly to characteristic of loads, i.e. sensitive-to-frequency-variation load or insensitive-to-frequency-variation i load. The UPS system in this invention comprise of a backup battery, a battery charging means or a battery charger, a High Frequency DC/AC converter, a High Frequency transformer, and is characterized in that it is further consist of a load characteristic analysis means which can analyze and determine sensitivity to frequency variation of the connecting load. In the case that the connecting load is not sensitive to frequency variation, for example, a personal computer having a switching power supply, the UPS will output DC voltage to the load. When there is power shortage, the UPS can provide D.C. power to load directly. Therefore any ripple and current spikes in the transition period could be eliminated. Furthermore, high efficiency can be achieved since there is no loss in DC/AC converter. for example if the load is an old monitor using transformer as an input part. It is generally known that the monitor will be short circuit if it is fed by DC voltage. On the contrary, after the load characteristic analysis means has determined that the load is sensitive to frequency variation, the UPS will output AC voltage to the load as a typical UPS does. In the second embodiment of the invention, if the present invention is used as UPS for non-sensitive-to-frequency-variation load, such as computer and monitor with switching power supply, the UPS will output D.C. voltage directly to load.The second embodiment of the invention uses fewer elements and is efficient. Moreover, another embodiment of the present invention discloses a UPS further comprising a Power Factor Corrector or PFC. The PFC circuit is to improve power factor for the UPS. 4 In another embodiment of the present invention, a battery charger having D.C. voltage input is added into a UPS having a PFC. The present invention is intend to provide means to reduce interference during transition period - automatic switching between drawing energy from battery or main lines (so called "transfer time") It is another objective of the present invention to have a load analyzing means in UPS so that the UPS can determine whether the connecting load is sensitive to changing of frequency or not. In the case that the connecting load is not sensitive to changing of frequency, the UPS will supply D.C. voltage to the load since the startup so that it can switch electric energy to load smoothly without any power disruption in the transfer time. The objective of the present invention will become apparently when considering together with attached drawings and detailed description. BRIEF DESCRIPTION OF THE DRAWINGS A preferred embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which: FIG. 1 is a circuit diagram of a typical stand-by UPS using a low frequency transformer; FIG. 2 is a circuit diagram of a typical stand-by UPS using high frequency DC/AC Converter and high frequency transformer; FIG. 3 is the first embodiment of a UPS according to the present invention using a load analyzing means; FIG. 4 is the second embodiment of a UPS according to the present invention for load that is not sensitive to frequency changing; FIG. 5 is a modification of the UPS in FIG. 3 further including a Power Factor Corrector circuit; 5 FIG. 6 is a modification of the UPS in FIG. 4 further including a Power Factor Corrector circuit; FIG. 7 is a modification of the UPS in FIG. 5 with a DC/DC batter charger circuit; FIG. 8 is a modification of the UPS in FIG. 6 with a DC/DC batter charger circuit. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Herein below will be described the invention by referring to figures as examples so it will become clearer. The same or corresponding elements or parts are assigned with the same number. This is without any limitation. Scope of the invention will be according to the annexed claims. Figure 3 is the first embodiment of a UPS according to the present invention using a load characteristic analyzing means. These are its components: the automatic switch 1 (SW1) and the automatic switch 2 (SW2), which are connected to the main distribution 220V. The load characteristic analysis circuit 12 will analyze the sensitivity of load characteristic to the current variation. The control means 32 is the logic circuit or programmable microcontroller which functions to verify the status of the outside distribution and to control the automatic switch 1 (SW1) and the automatic switch 2 (SW2) in selecting to discharge to the load as specified. The control means 32 receives signal from the load characteristic analysis means 12 of which maybe consists a discrete element, such as a diode alone or together with a microprocessor and/or Digital Signal Processing (DSP) consisting of a Current Sensor and Voltage Sensor (not shown in the figure) for sensing output voltage applied to the load. It will analyze and compare the output current wave and output voltage wave discharging to the load to the specified forms or patterns. The DSP then will give a signal to the control means 32. It will determine the load characteristic in order to control how to output voltage to the specific load. The process of load analysis and decision whether the 6 load is sensitive to frequency variation or not is well known in the art so it will not be described further. In figure 3, the number 14 is a current alternating circuit or a low frequency DC/AC converter circuit. It will transform the dc voltage to the low frequency ac voltage (50 or 60 Hz). The number 16 and 22 are current rectifying circuit for transforming the ac voltage to the dc voltage. The number 18 is the filter circuit, which will smooth the current discharging to the load. The filter 18 may be a large capacitor or a resonance circuit. In figure 3, the battery charger circuit 26 charges the battery to reserve electrical energy in the battery. The current alternating circuit or high frequency DC/AC converter 24 will transform the dc voltage to high frequency ac voltage for feeding through the high frequency transformer to increase the voltage. The Operation of first embodiment of this Invention Referring to figure 3, in normal status (i.e. the main line normally discharges to load), the UPS according to this invention will provide the ac voltage from 220 V transmission line via the current rectifying circuit 16, the battery charger 26 and SW1 switch through the load characteristic analysis means 12 and to the load. In the meantime, the battery charger 26 will charge the battery and reserve the power. The load characteristic analysis means 12 will analyze the load whether it is sensitive to the frequency variation or not. Then, it will give a signal to the control means 32 to control the operation of the SW1 and SW2, as shown in Table 1 below. "Table 1 Shows The Position of SW1 and SW2 and Output Voltage of UPS Status of the Main Line Load Characteristic Position of SW1 Position of SW2 Output Voltage 1. AC 220 V - sensitive to the frequency variation - not sensitive to the frequency variation a b a b AC DC 2. 0 V or lower than specified voltage. - sensitive to the frequency variation - not sensitive to the frequency variation a b a b AC DC 7 The case of load that is sensitive to the frequency variation In normal status, the ac voltage from the outside power source is fed to the load by SW1 and SW2 in the position "a". When the voltage of the main line is lower than a specific level, the control means 32 will change the SW1 to the position "a" and the SW2 to the position "b". The ac voltage will be fed to the load by the reserved power in battery through the high frequency DC/AC converter circuit 24, through the high frequency transformer. It will be transformed to the dc voltage by the rectifier circuit 22 and gone through the low frequency DC/AC converter circuit 14 to be the low frequency ac voltage, before it is discharged through SW1 and SW2 as the power to the load. The Case of Load that is not sensitive to the frequency variation In normal status, the UPS according to this invention will discharge the dc voltage to the load at the beginning. The ac voltage from the main line is * provided through the current rectifying circuit 16 and the filter circuit 18 to be the high dc voltage and goes through the SW1 and SW2 which are in the position of "b" to the load. When the voltage of the main line is lower than a specific level, the, the control means32 will set the SW1 and SW2 in the position "b". The dc voltage is discharged to the load from the reserved power in battery. It will be provided through the high frequency current alternated circuit 24 and high frequency transformer. It will be transformed to the directed voltage by the rectifier circuit 22 and gone through the current filter circuit 18, SW1 and SW2 to be the power for the load. Figure 4, shows a UPS according to the second embodiment of this invention. " It will be used in case of proving that the UPS will be used with the load that is not sensitive to the frequency variation. The UPS as in the figure 4 is cheap for it has lesser parts. Though it can work well with the load of a display monitor, it cannot supply ac voltage for monitor degaussing. Therefore, the monitor is connected to the automatic switch to transfer the alternating current to the screen when the main distribution does not put off. Although the 8 transfer time is not zero, there is no any disadvantage for the monitor as already described in figure 4. The UPS according to the second embodiment of this invention, as shown in figure 4, is almost similar to the UPS in the first embodiment. Therefore the same equipments or parts will be assigned the same number and will be described only the different parts. Since the load that connected to the UPS is not sensitive to the frequency variation, for example, a monitor and computer, some parts can be reduced. Switch SW2, an low frequency alternated circuit and load characteristic analysis circuit 12 can be eliminated. Thus, the cost can be reduced. The Operation of Invention in the second embodiment As shown in figure 4, in the normal state, the UPS will discharge the ac voltage to the load 1 and dc voltage to the load 2 at the beginning. The ac voltage from outside power source will be fed through SW 1 while it is in the position "a", to the load 1. At the same time, the ac voltage will be provided through the current rectifying diode circuit 16 and a filter circuit 18 which then It can be seen that the function of the both of the current rectifying diode 9 UPS will be higher. There is no need of a large and heavy low frequency transformer. There is no need to discharge the imaginary power to load. There is no current disruption during the power shortage. To supply the dc voltage directly to the load that is a type of a switching power supply will increase the overall efficiency of the supply. Because there is no need for the ripple reduction circuit that will operate at two time higher frequency of the ac frequency paying to the load. Therefore, the entire efficient of the device is higher. The power from battery is saved, as well. Figure 5 is the modification of the UPS in the first embodiment of this (invention, including a Power Factor Corrector (hereafter called "PFC"). In i figure 6 is the UPS in the second embodiment of this invention modified with PFC. The PFC circuit 34 is added between current rectifying circuit 16 and current filter circuit 18 as shown in figure 5 and 6. The power factor of the UPS can be improved. The battery charger 26 is of a type that has dc input voltage. Therefore, the connection position of the charger 26 to the main line, which is alternated current, will be changed to the point behind the current rectifying circuit 16 when switch is at the position "a". Otherwise it will be connected to the point after PFC circuit 34 as the switch go to the position "b", as illustrated , | in figure 7 and 8. There are many methods to adjust the load that have power factor less than 1, to become pf 1 or close to 1. For example, by adding an inductor coil or a capacitor to the load in order to minimize the imaginary power of the load to zero or as least as possible. However, this may need a large and heavy capacitor or inductor coil, so that it will make the device a lot heavier and larger. This method works well for load without current distortion and using only base frequency. The wide range of voltage, such as 100-270 VAC, can be used with the load that is not sensitive to the alternated current frequency variation such as the switching power supply of computer and screen. If the , j load characteristic is as mentioned above, the power factor will not be 1 and the current waveform will not be sine. Apart from the base frequency, it is harmonic current. However, the load can be minimized the impact from 10 imaginary power by reduction the distribution frequency to be 0 Hz, in other words, by feeding dc voltage directly to the load. On the other hand, the load " which is sensitive to the frequency variation, such as load having main power transformer inside, supplying DC voltage to this kind of load will cause short circuit and damage the power source and the load, as well. Therefore, the load characteristic analysis circuit is used to verify whether the load is sensitive to the AC frequency variation or not. The power factor corrector is a well-known technique so it is not described in detail. Though, this invention is completely described with the attached figures. The modification or correction by any ordinary skilled people in this field within the scope and purpose of the invention may be possible. For example, the switch process or switch SW1, SW2 may be solid state relay or semi-conductor switch such as SCR, BJT transistor, MOSFET. The control means may be a microcontroller or a logic circuit. 11 WE.CLAIM: 1. A high efficiency Uninterruptible Power Supply (UPS) receiving power from the outside AC voltage source and outputting stable voltage continuously to a load even if the AC voltage received from said outside AC voltage source is irregular or is briefly disrupted; said uninterruptible power supply comprising: a battery charging means connected to said AC voltage source for receiving input voltage from the AC voltage source and supplying DC voltage at its output terminal to charge a chargeable battery as the reserved power in normal operation; - a high frequency DC/AC converter circuit coupled to the output of said battery charging means and to said chargeable battery for transforming DC voltage at its input to high frequency AC voltage at its output; - a high frequency transformer coupled to the output terminals of said high frequency DC/AC converter circuit for increasing the high frequency AC voltage at its output terminals; - a first current rectifying circuit connected to the output of said high frequency transformer for supplying on its output a DC voltage to the load; - a second current rectifying circuit receiving input voltage from the AC source and paralleling connected its output with the output of the first current rectifying circuit wherein it outputs DC voltage to the load in normal operation; 12 a filter circuit connected to the output of both of the current rectifying circuits for smoothing the DC voltage discharging to the load; a low frequency DC/AC converter circuit connected to the output of the filter circuit for converting a DC voltage oMtputting from said filter circuit to an AC voltage at the output of the circuit; characterized in that a switch means including a first switch and a second switch, whereby the first switch connected to the AC source, second switch and the load; said first switch is controllably switched, in response to the first contorl signal tor selection between discharging Yne AC voltage from the AC source, and discharging the voltage from the second switch for supplying power to the load; whereby the second switch connected to the first switch, output of the said low frequency DC/AC converter and the output of the filter circuit; said second switch is controllably switched, in response to the second control signal for selection between discharging the AC voltage from output of the said low frequency DC/AC converter and discharging the DC voltage from the output of the filter circuit for supplying power to the load; and a control means coupled to said switch means for providing the first and the second control signals to said switch means; said control means including a voltage sensing means for monitoring voltage level of the AC source, and a load characteristic analysis means connected to the load 13 input for analyzing and determining whether the load is sensitive to the alternated current frequency variation or not; whereby the control means establishes control signals for said first switch and said second switch of the switch means in response to the voltage level of the AC source and the load characteristic. 2. The Uninterruptible Power Supply (UPS) according to claim 1, wherein said control means establishes the first control signal for said first switch to connect the load to the AC source, when the control means determines that the voltage level of the AC source is higher than a predetermine level. 3. The Uninterruptible Power Supply (UPS) according to claim 1, wherein said control means establishes the first control signal for said first switch to connect the load to the output voltage from the second switch, when the control means determines that the voltage level of the AC source is lower than a predetermine level by using reserved power in said battery. 4. The Uninterruptible Power Supply (UPS) according to claim 1, wherein said control means establishes the first control signal and second control signal for said first switch and said second switch respectively, to connect the load to the DC voltage from the output of said filter circuit for discharging said load with DC voltage, when the control means determines that the load is not sensitive to the frequency variation. 5. The Uninterruptible Power Supply (UPS) according to claim 1, said UPS further comprising a power factor corrector circuit connected between 14 the second current rectifying circuit and the filter circuit for adjusting the entire power factor of the uninterruptible power supply. 6. An Uninterruptible Power Supply (UPS) receiving power from the outside AC voltage source and outputting stable voltage continuously to a load even if the AC voltage received from said outside AC voltage source is irregular or is briefly disrupted; said uninterruptible power supply comprising: a battery charging means connected to said AC voltage source for receiving input voltage from the AC voltage source and supplying DC voltage at its output terminal to charge a chargeable battery as the reserved power in normal operation; a high frequency DC/AC converter circuit coupled to the output of said battery charging means and to said chargeable battery for transforming DC voltage at its input to high frequency AC voltage at its output; a high frequency transformer coupled to the output terminals of said high frequency DC/AC converter circuit for increasing the high frequency AC voltage at its output terminals; a first current rectifying circuit connected to the output of said high frequency transformer for supplying on its output a DC voltage to the load; a second current rectifying circuit receiving input voltage from the AC source and paralleling connected its output with the output of the first 15 current rectifying circuit wherein it outputs DC voltage to the load in normal operation; a filter circuit connected to the output of both of the current rectifying circuits for smoothing the DC voltage discharging to the load; a switch means including a first switch whereby the first switch connected to the AC source, the output of the filter circuit; said first switch is controllably switched, in response to the first control signal, for selection between discharging the AC voltage from the AC source, and discharging the DC voltage from the output of said filter circuit for supplying power to the load; and a control means coupled to said switch means for providing the first control signal to said switch means; said control means including a voltage sensing means for monitoring voltage level of the AC source; whereby the control means establishes a control signal for said first switch of the switch means in response to the voltage level of the AC source. 7. The Uninterruptible Power Supply (UPS) according to claim 6, wherein said control means establishes the first control signal for said first switch to connect the load to the AC source, when the control means determines that the voltage level of the AC source is higher than a predetermine level. 16 8. The Uninterruptible Power Supply (UPS) according to claim 6, wherein said control means establishes the first control signal for said first switch to connect the load to the DC voltage from the output of said filter circuit, when the control means determines that the voltage level of the AC source is lower than the predetermine level by using reserved power in said battery. 9. The Uninterruptible Power Supply (UPS) according to claim 6, said UPS further comprising a power factor corrector circuit connected between the second current rectifying circuit and the filter circuit for adjusting the entire power factor of the uninterruptible power supply. 10. The Uninterruptible Power Supply (UPS) according to any of proceeding claims, wherein the battery charging means is of a type that has DC voltage. ith Dated this 1T day of August, 2003 FOR NATIONAL SCIENCE AND TECHONOLOGY DEVELOPMENT AGENCY (MANISH SAURASTRI) KRISHNA & SAURASTRI 17

Documents:

787-mum-2003-abstract(13-07-2004).doc

787-mum-2003-abstract(13-07-2004).pdf

787-mum-2003-abstract(amended)-(13-7-2004).pdf

787-mum-2003-abstract(granted)-(17-10-2007).pdf

787-mum-2003-cancelled pages(24-03-2005).pdf

787-mum-2003-claims(amended)-(24-3-2005).pdf

787-mum-2003-claims(complete)-(11-8-2003).pdf

787-mum-2003-claims(granted)-(17-10-2007).pdf

787-mum-2003-correspondence(13-7-2004).pdf

787-mum-2003-correspondence(ipo)-(17-10-2007).pdf

787-mum-2003-corrospondence(ipo)-(19-01-2005).pdf

787-mum-2003-corrospondence-1-(13-07-2004).pdf

787-mum-2003-corrospondence-2-(26-09-2003).pdf

787-mum-2003-description(complete)-(11-8-2003).pdf

787-mum-2003-description(granted)-(17-10-2007).pdf

787-mum-2003-drawing(11-8-2003).pdf

787-mum-2003-drawing(13-07-2004).pdf

787-mum-2003-drawing(amended)-(13-7-2004).pdf

787-mum-2003-drawing(granted)-(17-10-2007).pdf

787-mum-2003-form 1(11-08-2003).pdf

787-mum-2003-form 19(26-02-2004).pdf

787-mum-2003-form 2(complete)-(11-8-2003).pdf

787-mum-2003-form 2(granted)-(17-10-2007).pdf

787-mum-2003-form 2(granted)-(24-03-2005).doc

787-mum-2003-form 2(granted)-(24-03-2005).pdf

787-mum-2003-form 2(title page)-(complete)-(11-8-2003).pdf

787-mum-2003-form 2(title page)-(granted)-(17-10-2007).pdf

787-mum-2003-form 3(11-08-2003).pdf

787-mum-2003-form 3(13-07-2004).pdf

787-mum-2003-form 5(11-08-2003).pdf

787-mum-2003-general power of attorney(11-08-2003).pdf

787-mum-2003-petition under rule 137(13-07-2004).pdf

787-mum-2003-specification(amended)-(13-7-2004).pdf

787-mum-2003-we claims(13-07-2004).doc

abstract1.jpg