DESC:

FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]

MID-FREQUENCY POWER CONVERTER

Livguard Energy Technologies Pvt. Ltd. an Indian Company, of Plot No.221, Udyog Vihar Phase I, Sector 20 Gurugram (Haryana) 122016

THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.

FIELD OF THE INVENTION:
[001] The present disclosure relates to power electronics. In particular, the present disclosure relates to electrical power converters used in electric supply backup systems.

BACKGROUND OF THE INVENTION:
[002] Electrical power converters are known for conversions of AC to DC and DC to AC, respectively. Static power converters, or popularly known as Uninterrupted Power Supply (UPS), are used in buildings and other establishments for supplying electricity to electrical devices or appliances using batteries in the event of power outages. Electrical appliances are generally configured for operating on a sine wave electricity supply. Sine wave inverters are costly as compared to similarly rated square wave inverters. High frequency inverters are known for their compactness and better efficiency ratings. However, high frequency inverters are less economic to manufacture as these inverters require additional components such as DC to DC boost converter and buck converter to meet the required specifications. Further, there may be other additional components required to generate AC output (comparable to commercial Mains supply) to run the utility. The present disclosure is directed to address the problems as discussed above and other associated problems with the art.

OBJECTS OF THE INVENTION:
[003] The present disclosure provides for an inverter with higher inverter efficiency.

[004] Another object of the present disclosure is to provide an inverter with lower manufacturing costs as compared to similarly rated other inverters.

[005] Another object of the present invention is to provide a power converter with lesser number of components.

[006] An object of the present disclosure is to provide for a power converter which operates in the charging mode with higher power factor over the entire range of charger operation.

[007] Yet another object of the present disclosure is to provide for an inverter with lower power losses in no-load situations.

SUMMARY OF THE INVENTION:
[008] One or more shortcomings of conventional methods and systems are overcome, and additional advantages are provided through the present disclosure. Additional features and benefits are realised through the techniques of the present disclosure. The present disclosure provides for a power converter that uses mid-range frequency around 400 Hz for power conversions.

[009] Further, the power converter as disclosed herein uses a lamination core based transformer for power conversion. The size and weight of the core are substantially reduced. The volume of the transformer core used in the power converter of the present disclosure may be about one-third as compared to the volume of the transformers used in similarly rated conventional power converters of 50/60Hz. Further, the leakage inductance is utilized within the circuit to eliminate the need of additional inductors in the circuit.

[0010] The converter circuit used herein works as a bidirectional circuit and thus reduces costs while improving the efficiency of the power converter. The power converter as disclosed herein may provide for higher efficiency levels of as compared to the conventional power converters. Further, the power losses are also minimized in the power converter in no-load conditions. The no-load condition power losses may be optimized as compared to the conventional power converters. Further, the power converter of the present disclosure operates closer to unity power factor in the charging mode over the entire range of charger operation. The power converter as disclosed herein utilizes a lesser number of parts as compared to conventional high frequency power converters.

[0011] The foregoing summary is illustrative only and is not intended to be limiting. In addition to the illustrative aspects, embodiments, and features described herein, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS:
[0012] Figure 1 illustrates a schematic circuit diagram of the power converter in accordance with an embodiment of the present disclosure.

[0013] The figures depict embodiments of the disclosure for purposes of illustration only. One skilled in the art will readily recognise from the following description that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the invention described herein.

DETAILED DESCRIPTION OF THE INVENTION:
[0014] While the embodiments in the present disclosure are subject to various modifications, alternative forms, or method steps, specific embodiment thereof has been shown by example. It should be understood, however, that it is not intended to limit the disclosure to the particular methods, components or circuits disclosed; on the contrary, the disclosure is to cover all modifications, equivalents, and alternatives falling within the scope of the disclosure. It is to be noted that a person skilled in the art would be motivated from the present disclosure and modify the power converter, which may vary depending on the circuit arrangement and components used. However, such modifications should be construed within the scope of the disclosure.

[0015] Accordingly, the drawings and description show and describe only those specific details that are pertinent to understanding the invention in the present disclosure so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.

[0016] A power converter is disclosed. In an embodiment, the power converter may be configured as a UPS. The power converter may be used as a power source for use in residential or commercial establishments for the supply of electricity.

[0017] Figure 1 illustrates a circuit diagram of a power converter in accordance with an embodiment of the present disclosure. In Figure 1, the circuit shown towards the left side of a transformer T1 is referred to as the primary circuit and the circuit shown towards the right side of the transformer T1 is referred to as the secondary circuit. The transformer T1 may be a laminated core-based transformer. In an embodiment, T1 may have bifilar coil winding. The winding of T1 in the primary circuit is referred to as the primary winding and of T1 in the secondary circuit is referred to as the secondary winding. A laminated core is disposed of between the first winding and the second winding of T1. As shown in Figure 1, in the first circuit, a battery, two MOSFETS (generically also known as electronic switches) Q1 and Q2 and a shunt SH1 is provided. The drain terminal of Q1 is connected to one of the terminals of the primary winding of the transformer T1 and the source terminal of Q1 is connected to the negative terminal of the battery. Whereas, the drain terminal of Q2 is connected to the other side of the bifilar winding of the transformer T1’s primary winding. SH1 is provided between the negative terminal of the battery and Q1-Q2 for measuring the battery current, other methods of current measurements may be deployed, based on the rating/configuration of the system. The gates of Q1 and Q2 may be connected with a controller to generate an appropriate signal at the gates to produce an alternating current with a frequency of 400 Hz. The voltage at the primary winding of the transformer is stepped up by T1. The two windings of the transformer may operate in 180° phase shift. The secondary circuit includes MOSFETS Q3-Q8 and capacitors C1-C2. The Mains supply is connected with the second circuit as shown in Figure 1. In inverter mode, MOSFETs Q5-Q8 are used for generating sine wave voltage using pulse width modulation. The gates of Q4-Q8 may be connected with the controller to operate at 20 kHz for generating a SPWM (sinusoidal pulse width modulation), which is filtered using the filter circuit wherein inductor L4 and capacitor C3 are used for obtaining pure sine wave for the supply of alternating current towards the utility load. In charger mode, Q6 and Q8 used to operate at 20 kHz PWM (pulse width modulation) for power factor correction and generating high voltage DC drain of Q3 and source of Q4 while, Q3 and Q4 operate at 400 Hz to convert the said high voltage DC into high voltage AC, suitable for the secondary side of transformer T1. After stepdown by the transformer T1, the current is suitably rectified, by the body diode of Q1 and Q2, into DC to charge the battery, as required.

[0018] The controller may be configured and connected with the gates of the MOSFETS Q1-Q8 for functioning in inverter or charger mode as required. In the power converter disclosed herein, the transformer is made with a laminated core. Accordingly, about one-third material may be used in making the transformer as compared to conventional power converters of power line frequency. Accordingly, the size/volume as well as the cost of the transformer and the overall power converter also reduces substantially. Further, due to the inherent nature of lamination-based transformers used in the frequency range the magnetic and winding losses are optimized, which results in higher operating efficiency. Due to the use of a lamination-based transformer, the power converter may have significant leakage inductance. The leakage inductance is utilized in the circuit itself to reduce the additional cost for inductors which are generally required for high-frequency power converters. Accordingly, the converter works as a bi-directional one, and thus helps to reduce cost and increase the efficiency of the power converter.

[0019] In particular, referring to Figure 1, there is demonstrated an inverter cum charger circuit (10) adapted to function in an inverter mode and in a charger mode. The inverter cum charger circuit (10) comprises a primary circuit (28) connected to at least one battery (not shown). The primary circuit (28) comprises a first set of components that function as a DC to AC converter in the inverter mode thereby producing a first AC signal having a first frequency value and a second voltage value from a first DC signal having a first voltage value. By way of a non-limiting example, the first voltage 12V DC, the first frequency value is 400 Hz and the second voltage value is 12V AC.

[0020] The inverter cum charger circuit (10) comprises a transformer (12) having a primary side (14) connected to the primary circuit (28) and a secondary side (16). In an embodiment of the invention, the transformer (12) is adapted to function as a step-up transformer in the inverter mode. The transformer (12) is adapted to produce a second AC signal having the first base frequency value and a third voltage value in the inverter mode. By way a non-limiting example, the third voltage value is about 170V AC. Thus, by way of example, in the inverter mode, the primary side of the transformer receives the first AC signal having the second voltage value of 12V AC at the first frequency value of 400 Hz and produces a second AC signal having the third voltage value pf about 170V AC the first frequency value of 400 Hz.

[0021] The transformer (12) comprises a primary side (14) and a secondary side (16). The primary side (14) of the transformer (12) comprises a first outer terminal (18) and a second outer terminal (20) and a center tapping (22). The secondary side (16) comprises a third outer terminal (24) and a fourth outer terminal (26). A number of turns of the secondary side (16) is greater than a number of turns of the primary side (14). Thus, when varying voltage is applied on the primary side (14), the transformer (12) functions as a step-up transformer and when varying voltage is applied on the secondary side (16), the transformer (12) functions as a step-down transformer.

[0022] The inverter cum charger circuit (10) comprises a secondary circuit (48) connected to the secondary side (16) of the transformer (12). The secondary circuit (48) comprises a second set of components that function as a rectification and voltage increasing components in the inverter mode. Thus, the second set of components convert the second AC signal available at the secondary side (16) of the transformer (12) into a second DC signal having a fourth voltage value. Typically, the fourth voltage value of the second DC signal is greater than the third voltage value of the second AC signal. By way of example, the fourth voltage value of the second DC signal is about 340 V DC.

[0023] The secondary circuit (48) further comprises a third set of components that function as a sinusoidal pulse width modulator in the inverter mode. The third set of components receive the second DC signal produced by the second set components and produce a sinusoidal pulse width modulated signal having a second base frequency value, a third pulse frequency value and a fifth voltage value. By way of a non-limiting example, the second base frequency value is about 50 Hz. By way of a non-limiting example, the third pulse frequency value is 20 kHz. By way of a non-limiting example, the fifth voltage value is 220V AC.

[0024] The secondary circuit (48) further comprises a fourth set of components that function as filter element in the inverter mode. The fourth set of components receive the sinusoidal pulse width modulated signal from the third set of components and generates a final output AC signal having a second base frequency value and a fifth voltage value. As mentioned above, by way of a non-limiting example, the second base frequency value is about 50 Hz and the fifth voltage value is 220V AC.

[0025] When the inverter cum charger circuit (10) is operated in the charger mode, the fourth set of components function as a rectifier. In this case, the fourth set of components receive an input AC signal having the second base frequency value and the fifth voltage value and produce a third DC signal having a sixth voltage value. As mentioned above, by way of a non-limiting example, the second base frequency value of the input AC signal is about 50 Hz and the fifth voltage value of the input AC signal is 220V AC. By way of a non-limiting example, the sixth voltage value of the third DC signal as produced by the fourth set of components in the charger mode is about 220V DC.

[0026] When the inverter cum charger circuit (10) is operated in the charger mode, the third set of components function as a boost converter as well as a power factor corrector. In this case, the third set of components receive the third DC signal from the fourth set of components and produce a fourth pulsed DC signal having a seventh voltage value and a fourth pulse frequency value. By way a non-limiting example, the seventh voltage value of the third DC signal is about 340V DC and fourth pulse frequency value is 40 kHz.

[0027] When the inverter cum charger circuit (10) is operated in the charger mode, the second set of components function as a DC to AC converter and a voltage decreasing components. Thus, the second set of components receive the fourth pulsed DC signal from the third set of components and produce a third AC signal having the first base frequency value and the third voltage value.

[0028] When the inverter cum charger circuit (10) is operated in the charger mode, the transformer (12) functions as a step-down transformer. Thus, the secondary side (16) of the transformer (12) receives the third AC signal from the second set of components, and the primary side (14) of the transformer (12) produces a fourth AC signal having the first base frequency value and the second voltage value.

[0029] When the inverter cum charger circuit (10) is operated in the charger mode, the first set of components further functions as an AC-DC converter. Thus, the first set of components receives the fourth AC signal from the primary side (14) of the transformer (12) and produces an output DC signal having the first voltage value.

[0030] In an embodiment of the invention, the first set of components comprise a first MOSFET (Q1, 30), a second MOSFET (Q2, 32) and optionally a shunt resistor (SH1, 34). In an embodiment of the invention, a first source terminal (36) of the first MOSFET (Q1, 30) is connected to a second source terminal (42) of the second MOSFET (Q2, 32) such that there lies a first point (P1) therebetween. The first point (P1) is connected directly or indirectly to a negative terminal of the at least one battery. In another words, the first point (P1) in one option is connected directly to a negative terminal of the at least one battery (not shown). In another option, the first point (P1) may be connected to the negative terminal of the at least one battery (not shown) vide the shunt resistor (SH1, 34).

[0031] In an embodiment of the invention, a first drain terminal (38) of the first MOSFET (Q1, 30) is connected to a first outer terminal (18) of the transformer (12). In another embodiment of the invention, a second drain terminal (44) of the second MOSFET (Q2, 32) is connected to a second outer terminal (20) of the transformer (12). In yet another embodiment of the invention, the primary side (14) of the transformer comprises a center tapping (22) of which is connected to a positive terminal of the at least one battery.

[0032] In a further embodiment of the invention, the first MOSFET (Q1, 30) comprises a first Gate terminal (40) and the second MOSFET (Q2, 32) comprising a second Gate terminal (46). In an embodiment of the invention, the first Gate terminal (40) of the first MOSFET (Q1, 30) receives a first gate control signal (GE) in the inverter mode. In another embodiment of the invention, the second Gate terminal (46) of the second MOSFET (Q2, 32) receives a second gate control signal (GF) in the inverter mode.

[0033] In a furthermore embodiment of the invention, when the first gate control signal (GE) is applied at the first Gate terminal (40) of the first MOSFET (Q1, 30) in the inverter mode, the second gate control signal (GF) is not provided to the second Gate terminal (46) of the second MOSFET (Q2, 32). Likewise, when the second gate control signal (GF) is applied at the second Gate terminal (46) of the second MOSFET (Q2, 32) in the inverter mode, the first gate control signal (GE) is not applied at the first Gate terminal (40) of the first MOSFET (Q1, 30). In an embodiment of the invention, first gate control signal (GE) and the second gate control signal (GF) are produced by a control unit (not shown). In an embodiment of the invention, the first gate control signal (GE) supplied to the first Gate terminal (40) of the first MOSFET (Q1, 30) in the inverter mode and the second gate control signal (GF) supplied to the second gate terminal (46) of the second MOSFET (Q2, 32) in the inverter mode are such that the first MOSFET (Q1, 30) along with the second MOSFET (Q2, 32) function as a DC to AC converter.

[0034] By way of a non-limiting example, a first gate control signal (GE) having a frequency of 400 Hz is applied at the first Gate terminal (40) of the first MOSFET (Q1, 30) and a second gate control signal (GF) having a frequency of 400 Hz is applied at the second Gate terminal (46) of the second MOSFET (Q2, 32). Generally, there is maintained a time difference between a time when the first gate control signal (GE) is applied at the first Gate terminal (40) of the first MOSFET (Q1, 30) and a time when the second gate control signal (GF) is applied at the second Gate terminal (46) of the second MOSFET (Q2, 32).

[0035] Because of the application of the input voltage to the primary circuit (28), application of the first gate control signal (GE) to the first MOSFET (Q1, 30), and application of the second gate control signal (GF) to the second MOSFET (Q2, 32), an alternating current having a square wave pattern start flowing through the primary side (14) of the transformer (12) and the frequency of the alternating current flowing through the primary side (14) of the transformer (12) is equal to the frequency of the first gate control signal (GE) and the second gate control signal (GF) i.e. 400 Hz.

[0036] It may be noted that the primary circuit (28) merely converts the DC voltage as produced by the at least one battery (not shown) to an AC output. Thus, if the at least one battery (not shown) produces a DC voltage having a value of about 12V, the primary circuit (28) produces a square wave pulse width modulated signal having an amplitude of 12V.

[0037] Since, the primary side (14) of the transformer (12) now receives an alternating current, the alternating current is transferred to the secondary side (16) of the transformer (12). As mentioned above, the transformer (12) functions as a step-up transformer when varying voltage is applied on the primary side (14) and hence, a stepped-up voltage is available between the third outer terminal (24) and the fourth outer terminal (26) on the secondary side (16) of the transformer (12).

[0038] It may be noted that the alternating current flowing through the primary side (14) of the transformer (12) as well as coming out of the secondary side (16) of the transformer (12) have a square wave pattern and not a sinusoidal wave pattern. Also, both alternating current flowing through the primary side (14) of the transformer (12) as well as coming out of the secondary side (16) of the transformer (12) have a frequency of 400 Hz. While it is possible to produce an AC output having a voltage value which can be directly used for driving AC loads (not shown) connected to the inverter and charger circuit (10), the output of the secondary side (16) of the transformer (12) cannot be directly coupled to the load (even if it has the desired voltage value of the AC output thus produced). Thus, in some cases, instead of attempting to produce the desired voltage value of the AC output, an AC output having a different voltage value is produced. For instance, the output of the secondary side (16) of the transformer (12) may produce an AC output having a voltage value of about 170V (Peak to Peak).

[0039] Additionally, it may be noted that, when the inverter cum charger circuit (10) is operated in the charger mode, no gate control signal is provided to the first Gate terminal (40) of the first MOSFET (Q1, 30). Also, no gate control signal is provided to the second Gate terminal (46) of the second MOSFET (Q2, 32) in the charger mode. Due to the above, the first MOSFET (Q1, 30) along with the second MOSFET (Q2, 32) function as a rectifier in the charger mode.

[0040] Thus, the inverter and charger circuit (10) comprise a secondary circuit (48) which is connected to the secondary side (16) of the transformer (12). In particular, the inverter and charger circuit (10) comprise a secondary circuit (48) which is connected to the third outer terminal (24) and the fourth outer terminal (26) of the transformer (12). The secondary circuit (48) comprises a second set of components, a third set of components, and a fourth set of components.

[0041] In an embodiment of the invention, the second set of components comprise a first capacitor (66) connected to a second capacitor (68) at a fifth point (P5). In an embodiment of the invention, one of a third outer terminal (24) and a fourth outer terminal (26) of the transformer (12) is connected to the fifth point (P5). The second set of components further comprise a third MOSFET (Q3, 50) connected to a fourth MOSFET (Q4, 52) at a second point (P2). In an embodiment of the invention, another of the third outer terminal (24) and a fourth outer terminal (26) of the transformer (12) is connected to the second point (P2). In other words, the second point (P2) is formed between a third source terminal (54) of a third MOSFET (Q3, 50) and a fourth drain terminal (62) of a fourth MOSFET (Q4, 52) while the fifth point (P5) is formed between a positive terminal of the first capacitor (66) and a negative terminal of the second capacitor (68).

[0042] It can be seen that one of the third outer terminal (24) and the fourth outer terminal (26) of the transformer (12) is connected to a second point (P2) which is formed between a third source terminal (54) of a third MOSFET (Q3, 50) and a fourth drain terminal (62) of a fourth MOSFET (Q4, 52). The other of the third outer terminal (24) and the fourth outer terminal (26) of the transformer (12) is connected to a point (P5) which is between a first capacitor (66) and a second capacitor (68). The first capacitor (66) and the second capacitor (68) are connected back-to-back in that a positive terminal of the first capacitor (66) is connected to a negative terminal of the second capacitor (68) and the other of the third outer terminal (24) and the fourth outer terminal (26) of the transformer (12) is connected to the fifth point (P5) which there-between.

[0043] In another embodiment of the invention, a negative terminal of the first capacitor (66) is connected to a fourth source terminal (60) of the fourth MOSFET (Q4, 52) and a positive terminal of the second capacitor (68) being connected to a third drain terminal (56) of the third MOSFET (Q3, 50).

[0044] In yet another embodiment of the invention, the third MOSFET (Q3, 50) comprises a third gate terminal (58) to receive a third gate control signal (GH) and the fourth MOSFET (Q4, 52) comprises a fourth gate terminal (64) adapted to receive a fourth gate control signal (GG).

[0045] When the inverter cum charger circuit (10) is operated in the inverter mode, the third gate terminal (58) of the third MOSFET (Q3, 50) and the fourth gate terminal (64) of the fourth MOSFET (Q4, 52) are not being supplied with any gate control signal. Due to the above reason, the third MOSFET (Q3, 50) and the fourth MOSFET (Q4,52) purely function as a rectifier. This is attained by the body diode contained in each of the third MOSFET (Q3, 50) and the fourth MOSFET (Q4, 52). The voltage increase effect is provided by the first capacitor (66) connected to a second capacitor (68). Thus, the first capacitor (66) and the second capacitor (68) together with the third MOSFET (Q3, 50) and the fourth MOSFET (Q4, 52) function as a rectifier cum voltage increasing components.

[0046] If a capacitance value of the first capacitor (66) and a capacitance value of the second capacitor (68) are kept equal, the voltage doubling effect is observed at the third drain terminal (56) of the third MOSFET (Q3, 50). Thus, a voltage value of about 170V (Peak to Peak) at the output of the secondary side (16) of the transformer (12) gets transformed to about 340V DC voltage which is non-pulsating in nature at the third drain terminal (56) of the third MOSFET (Q3, 50). Thus, the combination of the first capacitor (66), the second capacitor (68), the third MOSFET (Q3, 50) and the fourth MOSFET (Q4, 52) can be referred to as a rectification and voltage increasing components when the inverter and charger circuit (10) is being operated in the inverter mode.

[0047] When the inverter cum charger circuit (10) is operated in the charger mode, the third gate terminal (58) of the third MOSFET (Q3, 50) is provided with a third gate signal (GH) and the fourth gate terminal (64) of the fourth MOSFET (Q4, 52) is provided with a fourth gate signal (GG). It may be noted that the third gate signal (GH) and the fourth gate signal (GG) are produced by the control unit (not shown). The third gate signal (GH) and the fourth gate signal (GG) being supplied to the third MOSFET (Q3, 50) and the fourth MOSFET (Q4, 52) in the charger mode cause the third MOSFET (Q3, 50) and the fourth MOSFET (Q4, 52) to function as a DC to AC converter.

[0048] In an embodiment of the invention, the third set of components comprise a fifth MOSFET (Q5, 70), a sixth MOSFET (Q6, 72), a seventh MOSFET (Q7, 74), and an eighth MOSFET (Q8, 76) connected in a bridge configuration. In particular, a fifth drain terminal (80) of the fifth MOSFET (Q5, 70) is connected to a seventh drain terminal (92) of the seventh MOSFET (Q7, 74) at a sixth point (P6); a sixth source terminal (84) of the sixth MOSFET (Q6, 72) is connected to an eighth source terminal (96) of the eighth MOSFET (Q8, 76) at a seventh point (P7); a fifth source terminal (78) of the fifth MOSFET (Q5, 70) is connected to a sixth drain terminal (86) of the sixth MOSFET (Q7, 72) at a third point (P3); and a seventh source terminal (90) of the seventh MOSFET (Q7, 74) being connected to an eighth drain terminal (98) of the eighth MOSFET (Q8, 76) at a fourth point (P4).

[0049] The fifth MOSFET (Q5, 70) comprises a fifth gate terminal (82) which adapted to receive a fifth gate control signal (GC); while the sixth MOSFET (Q6, 72) comprises a sixth gate terminal (88) adapted to receive a sixth gate control signal (GA); while the seventh MOSFET (Q7, 74) comprises a seventh gate terminal (94) adapted to receive a seventh gate control signal (GD); and the eighth MOSFET (Q8, 76) comprises an eighth gate terminal (100) adapted to receive an eighth gate control signal (GB).

[0050] When the inverter cum charger circuit (10) is operated in the inverter mode, the fifth gate control signal (GC) is supplied to the fifth gate terminal (82) of the fifth MOSFET (Q5, 70), the sixth gate control signal (GA) is supplied to the sixth gate terminal (88) of the sixth MOSFET (Q6, 72), the seventh gate control signal (GD) is supplied to the seventh gate terminal (94) of the seventh MOSFET (Q7, 74) and the eighth gate control signal (GB) is supplied to the eighth gate terminal (100) of the eighth MOSFET (Q8, 76). The fifth gate control signal (GC), the sixth gate control signal (GA), the seventh gate control signal (GD) and the eighth gate control signal (GB) are such that the fifth MOSFET (Q5, 70), the sixth MOSFET (Q6, 72), the seventh MOSFET (Q7, 74), and the eighth MOSFET (Q8, 76) operate as a sinusoidal pulse width modulator.

[0051] By wat of a non-limiting example, the fifth gate control signal (GC), the sixth gate control signal (GA), the seventh gate control signal (GD), and the eighth gate control signal (GB) have a frequency of about 20 kHz and is supplied by the controller (not shown). It may be noted that fifth MOSFET (Q5, 70), the sixth MOSFET (Q6, 72), the seventh MOSFET (Q7, 74), and the eighth MOSFET (Q8, 76) may also be referred to as sinusoidal pulse width modulator when the inverter and charger circuit (10) is being operated in the inverter mode.

[0052] When the inverter cum charger circuit (10) is operated in the charger mode, no gate control signal is supplied to the fifth gate terminal (82) of the fifth MOSFET (Q5, 70), and no gate control signal is supplied to the seventh gate terminal (94) of the seventh MOSFET (Q7, 74). Additionally, in the charger mode, the sixth gate control signal (GA) is supplied to the sixth gate terminal (88) of the sixth MOSFET (Q6, 72), and the eighth gate control signal (GB) is supplied to the eighth gate terminal (100) of the eighth MOSFET (Q8, 76). The sixth gate control signal (GA) and the eight gate control signal (GB) are such that the sixth MOSFET (Q6, 72), and the eighth MOSFET (Q8, 76) operate as a boost converter as well as a power factor corrector.

[0053] In an embodiment of the invention the fourth set of components comprise a combination of an inductor (102) and a third capacitor (104). Since the sinusoidal pulse width modulator produces pulses whose average voltage value is in the range of ± 220V and a frequency of 50Hz, there is provided a filter component, which comprises of the inductor (102) and the third capacitor (C3, 104) which smoothens the output and produces a 50Hz sinusoidal waveform whose voltage value is in the range of ± 220V, which can now be supplied to one or more loads which are connected between Output Line (L_O) and a Neutral Line (N) of the inverter and charger circuit (10).

[0054] In an embodiment of the invention, the first AC signal supplied to the primary side (14) of the transformer (12) in the inverter mode has a frequency of 400 Hz; and the third AC signal supplied to the secondary side (16) of the transformer (12) in the charger mode has a frequency of 400 Hz.

[0055] It can be seen that each of the set of components functions in different manners when the inverter and charger circuit (10) is operated in the inverter mode as compared to the inverter and charger circuit (10) being operated in the charger mode.

[0056] When the inverter and charger circuit (10) is operated in a charger mode, the inductor (102) and the third capacitor (C3, 104) functions as a rectifier and produces DC voltage, whose value is typically equal to peak value of a one cycle of the AC voltage i.e. about 220 V. The DC voltage thus produced by the combination of the inductor (102) and the third capacitor (C3, 104) is supplied between the third point (P3) and the fourth point (P4). In the charger inverter mode, the fifth MOSFET (Q5, 70) and the seventh MOSFET (Q7, 74) are not operated i.e. the fifth gate control signal (GC) and the seventh gate control signal (GD) are not supplied to the fifth gate terminal (82) of the fifth MOSFET (Q5, 70) and the seventh gate terminal (94) of the seventh MOSFET (Q7, 74), respectively. On the other hand, the sixth MOSFET (Q6, 72) and the eighth MOSFET (Q8, 76) are controlled to operate as a boost converter component as well as a power factor corrector in the charger mode. This is done by controlling the sixth gate signal (GA) which is supplied to the sixth gate terminal (88) of the sixth MOSFET (Q6, 72) and by controlling the eighth gate signal (GB) which is supplied to the eighth gate terminal (100) of the eighth MOSFET (Q8, 76). Typically, when the sixth MOSFET (Q6, 72) and the eighth MOSFET (Q8, 76) are controlled to operate as a boost converter component as well as a power factor corrector, a DC voltage of about 340V is produced between the sixth point (P6) and the seventh point (P7). By way of a non-limiting example, the sixth gate terminal (88) of the sixth MOSFET (Q6, 72) is supplied a sixth gate signal (GA) which is having a frequency of 40 kHz supplied and the eighth gate terminal (100) of the eighth MOSFET (Q8, 76) is supplied an eighth gate signal (GB) which is having a frequency of 40 kHz.

[0057] Now the DC voltage as produced by the boost converter component (or alternatively the power factor corrector) which comprises the sixth MOSFET (Q6, 72) and the eighth MOSFET (Q8, 76) is fed to the combination of third MOSFET (Q3, 50), the fourth MOSFET (Q4, 52), the first capacitor (C1, 66) and the second capacitor (C2, 68). The combination of third MOSFET (Q3, 50), the fourth MOSFET (Q4, 52), the first capacitor (C1, 66) and the second capacitor (C2, 68) are now operated to convert the DC voltage to an AC voltage having a desired frequency and a desired voltage magnitude. Even within this combination of combination of third MOSFET (Q3, 50), the fourth MOSFET (Q4, 52), the first capacitor (C1, 66) and the second capacitor (C2, 68), the combination of the third MOSFET (Q3, 50), the fourth MOSFET (Q4, 52) changes the DC voltage having pulses of very high frequency (frequency of 40 kHz) into an AC voltage of desired frequency and having a voltage value of 340V (peak to peak). Typically, the desired frequency is 400 Hz. This is done by supplying a third gate signal (GH) which is having the desired frequency of about 400 Hz to the third gate terminal (58) of the third MOSFET (Q3, 50) and similarly by supplying a fourth gate signal (GG) which is having the desired frequency of about 400 Hz to the fourth gate terminal (64) of the fourth MOSFET (Q4, 52).

[0058] Now the combination of first capacitor (C1, 66) and the second capacitor (C2, 68) receive the AC signal as generated by the third MOSFET (Q3, 50) and the fourth MOSFET (Q4, 52) and function to reduce a magnitude level of the voltage. Typically, the combination of first capacitor (C1, 66) and the second capacitor (C2, 68) functions as a voltage reducing component and if the capacitance value of the first capacitor (C1, 66) is equal to capacitance value of the second capacitor (C2, 68), the voltage value of the AC signal is reduced by 50% i.e. we get an AC signal having a voltage value of about 170V (Peak to Peak).

[0059] Now this AC voltage as produced by the combination of first capacitor (C1, 66) and the second capacitor (C2, 68) is applied to the secondary side (16) of the transformer (12). Now the transformer (12) functions as a step down transformer and produces an AC output of -12V to +12V. Typically, now the first MOSFET (Q1, 30) and the second MOSFET (Q2, 32) are operated as a bridge rectifier i.e. without providing the first gate control signal (GE) and the second gate control signal (GF). Thus, a pure DC signal is obtained, which can be used for charging of the at least one battery.

[0060] It may be noted that the values provided above are merely by way of illustration and these values can be changed, By way of example, the first voltage value of the first DC signal, the first frequency value of first AC signal, the second voltage value of the first AC signal, the third voltage value of the second AC signal, the first base frequency value of the second AC signal, the fourth voltage value of the second DC signal, the second base frequency value of the sinusoidal pulse width modulated signal, the third pulse frequency value of the sinusoidal pulse width modulated signal, the fifth voltage value of the sinusoidal pulse width modulated signal, the second base frequency value of the input AC signal, the fifth voltage value of the input AC signal, the seventh voltage value of the fourth pulsed DC signal, the fourth pulse frequency value of the fourth pulsed DC signal, the first base frequency value of the third AC signal, the third voltage value of the third AC signal, the first base frequency value of the fourth AC signal, the second voltage value of the fourth AC signal, and the first voltage value of the output DC signal as described in the aforesaid paragraphs may be varied and alternatively values can be easily arrived.

[0061] Accordingly, the power converter as disclosed herein provides for a substantially higher power inverter efficiency while optimizing no-load losses. The power converter as disclosed herein may achieve a near unity power factor over the entire range of the charging mode operation. Further, the power converter disclosed herein can be made using components readily available in the industry. Therefore, the power converter is simple in construction and economical to manufacture. While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for illustration purposes and are not intended to be limiting.
,CLAIMS:WE CLAIM:

1. An inverter cum charger circuit (10) adapted to function in an inverter mode and in a charger mode, said inverter cum charger circuit (10) comprising:
a primary circuit (28) connected to at least one battery, the primary circuit (28) comprising a first set of components that function as a DC to AC converter in the inverter mode thereby producing a first AC signal having a first frequency value and a second voltage value from a first DC signal having a first voltage value;
a transformer (12) having a primary side (14) connected to the primary circuit (28) and a secondary side (16), the transformer (12) being adapted to function as a step-up transformer in the inverter mode, the transformer (12) being adapted to produce a second AC signal having the first base frequency value and a third voltage value in the inverter mode;
a secondary circuit (48) connected to the secondary side (16) of the transformer (12); the secondary circuit (48) comprising:
a second set of components that function as a rectification and voltage increasing components in the inverter mode to convert the second AC signal available at the secondary side (16) of the transformer (12) into a second DC signal having a fourth voltage value which is greater than the third voltage value of the second AC signal;
a third set of components that function as a sinusoidal pulse width modulator in the inverter mode, the third set of components receiving the second DC signal produced by the second set components and producing a sinusoidal pulse width modulated signal having a second base frequency value, a third pulse frequency value and a fifth voltage value; and
a fourth set of components that function as filter element in the inverter mode, the fourth set of components receiving the sinusoidal pulse width modulated signal from the third set of components and generating a final output AC signal having the second base frequency value and the fifth voltage value.

2. The inverter cum charger circuit (10) as claimed in claim 1, wherein at least one of:
a. the fourth set of components function as a rectifier in the charger mode, the fourth set of components receiving an input AC signal having the second base frequency value and the fifth voltage value and producing a third DC signal having a sixth voltage value;
b. the third set of components function as a boost converter as well as power factor corrector in the charger mode, the third set of components receiving the third DC signal from the fourth set of components and producing a fourth pulsed DC signal having a seventh voltage value and a fourth pulse frequency value;
c. the second set of components function as a DC to AC converter and a voltage decreasing components in the charger mode; the second set of components receiving the fourth pulsed DC signal from the third set of components and producing a third AC signal having the first base frequency value and the third voltage value;
d. the transformer (12) functions as a step-down transformer in the charger mode with the secondary side (16) of the transformer (12) receiving the third AC signal from the second set of components, and the primary side (14) of the transformer (12) producing a fourth AC signal having the first base frequency value and the second voltage value; and
e. the first set of components further functioning as an AC-DC converter in the charger mode; the first set of components receiving the fourth AC signal from the primary side (14) of the transformer (12) and producing an output DC signal having the first voltage value.

3. The inverter cum charger circuit (10) as claimed in claim 1, wherein the first set of components comprise a first MOSFET (Q1, 30) and a second MOSFET (Q2, 32); a first source terminal (36) of the first MOSFET (Q1, 30) being connected to a second source terminal (42) of the second MOSFET (Q2, 32) such that there lies a first point (P1) therebetween, the first point (P1) being connected directly or indirectly to a negative terminal of the at least one battery; and a first drain terminal (38) of the first MOSFET (Q1, 30) being connected to a first outer terminal (18) of the transformer (12); a second drain terminal (44) of the second MOSFET (Q2, 32) being connected to a second outer terminal (20) of the transformer (12); and a center tapping (22) of the primary side (14) being connected to a positive terminal of the at least one battery.

4. The inverter cum charger circuit (10) as claimed in claim 3, wherein the first MOSFET (Q1, 30) comprising a first Gate terminal (40) and the second MOSFET (Q2, 32) comprising a second Gate terminal (46) and at least one of:
a. the first Gate terminal (40) of the first MOSFET (Q1, 30) receives a first gate control signal (GE) in the inverter mode;
b. the second Gate terminal (46) of the second MOSFET (Q2, 32) receives a second gate control signal (GF) in the inverter mode;
c. when the first gate control signal (GE) is applied at the first Gate terminal (40) of the first MOSFET (Q1, 30) in the inverter mode, the second gate control signal (GF) is not provided to the second Gate terminal (46) of the second MOSFET (Q2, 32);
d. when the second gate control signal (GF) is applied at the second Gate terminal (46) of the second MOSFET (Q2, 32) in the inverter mode, the first gate control signal (GE) is not applied at the first Gate terminal (40) of the first MOSFET (Q1, 30);
e. the first gate control signal (GE) and the second gate control signal (GF) are produced by a control unit (not shown);
f. no gate control signal is provided to the first Gate terminal (40) of the first MOSFET (Q1, 30) in the charger mode; and
g. the first gate control signal (GE) supplied to the first Gate terminal (40) of the first MOSFET (Q1, 30) in the inverter mode and the second gate control signal (GF) supplied to the second gate terminal (46) of the second MOSFET (Q2, 32) in the inverter mode are such that the first MOSFET (Q1, 30) along with the second MOSFET (Q2, 32) function as a DC to AC converter;
h. no gate control signal is provided to the second Gate terminal (46) of the second MOSFET (Q2, 32) in the charger mode due to which the first MOSFET (Q1, 30) along with the second MOSFET (Q2, 32) function as a rectifier.

5. The inverter cum charger circuit (10) as claimed in claim 1, wherein the second set of components comprise a first capacitor (66) connected to a second capacitor (68) at a fifth point (P5); one of a third outer terminal (24) and a fourth outer terminal (26) of the transformer (12) being connected to the fifth point (P5); a third MOSFET (Q3, 50) connected to a fourth MOSFET (Q4, 52) at a second point (P2); and another of the third outer terminal (24) and a fourth outer terminal (26) of the transformer (12) being connected to the second point (P2).

6. The inverter cum charger circuit (10) as claimed in claim 5, wherein at least one of:
a. the second point (P2) being formed between a third source terminal (54) of a third MOSFET (Q3, 50) and a fourth drain terminal (62) of a fourth MOSFET (Q4, 52);
b. the fifth point (P5) being formed between a positive terminal of the first capacitor (66) and a negative terminal of the second capacitor (68);
c. a negative terminal of the first capacitor (66) being connected to a fourth source terminal (60) of the fourth MOSFET (Q4, 52);
d. a positive terminal of the second capacitor (68) being connected to a third drain terminal (56) of the third MOSFET (Q3, 50);
e. the third MOSFET (Q3, 50) comprising a third gate terminal (58) to receive a third gate control signal (GH);
f. the fourth MOSFET (Q4, 52) comprising a fourth gate terminal (64) adapted to receive a fourth gate control signal (GG);
g. the third gate terminal (58) and the fourth gate terminal (64) are not being supplied with any gate control signal in the inverter mode due to which the third MOSFET (Q3, 50) and the fourth MOSFET (Q4,52) purely function as a rectifier;
h. the third gate terminal (58) of the third MOSFET (Q3, 50) being provided with a third gate signal (GH) in the charger mode;
i. the fourth gate terminal (64) of the fourth MOSFET (Q4, 52) being provided with a fourth gate signal (GG) in the charger mode;
j. the third gate signal (GH) and the fourth gate signal (GG) are produced by a control unit (not shown); and
k. the third gate signal (GH) and the fourth gate signal (GG) being supplied to the third MOSFET (Q3, 50) and the fourth MOSFET (Q4, 52) in the charger mode being such that the third MOSFET (Q3, 50) along with the fourth MOSFET (Q4, 52) function as a DC to AC converter.

7. The inverter cum charger circuit (10) as claimed in claim 1, wherein the third set of components comprise a fifth MOSFET (Q5, 70), a sixth MOSFET (Q6, 72), a seventh MOSFET (Q7, 74), and an eighth MOSFET (Q8, 76) connected in a bridge configuration; and at least one of:
a. a fifth drain terminal (80) of the fifth MOSFET (Q5, 70) being connected to a seventh drain terminal (92) of the seventh MOSFET (Q7, 74) at a sixth point (P6);
b. a sixth source terminal (84) of the sixth MOSFET (Q6, 72) being connected to an eighth source terminal (96) of the eighth MOSFET (Q8, 76) at a seventh point (P7);
c. a fifth source terminal (78) of the fifth MOSFET (Q5, 70) being connected to a sixth drain terminal (86) of the sixth MOSFET (Q7, 72) at a third point (P3);
d. a seventh source terminal (90) of the seventh MOSFET (Q7, 74) being connected to an eighth drain terminal (98) of the eighth MOSFET (Q8, 76) at a fourth point (P4);
e. the fifth MOSFET (Q5, 70) comprises a fifth gate terminal (82) adapted to receive a fifth gate control signal (GC);
f. the sixth MOSFET (Q6, 72) comprises a sixth gate terminal (88) adapted to receive a sixth gate control signal (GA);
g. the seventh MOSFET (Q7, 74) comprises a seventh gate terminal (94) adapted to receive a seventh gate control signal (GD);
h. the eighth MOSFET (Q8, 76) comprises an eighth gate terminal (100) adapted to receive an eighth gate control signal (GB);
i. in the inverter mode, the fifth gate control signal (GC) supplied to the fifth gate terminal (82) of the fifth MOSFET (Q5, 70), the sixth gate control signal (GA) supplied to the sixth gate terminal (88) of the sixth MOSFET (Q6, 72), the seventh gate control signal (GD) supplied to the seventh gate terminal (94) of the seventh MOSFET (Q7, 74) and the eighth gate control signal (GB) supplied to the eighth gate terminal (100) of the eighth MOSFET (Q8, 76) are such that the fifth MOSFET (Q5, 70), the sixth MOSFET (Q6, 72), the seventh MOSFET (Q7, 74), and the eighth MOSFET (Q8, 76) operate as a sinusoidal pulse width modulator;
j. in the charger mode, no gate control signal is supplied to the fifth gate terminal (82) of the fifth MOSFET (Q5, 70), no gate control signal is supplied to the seventh gate terminal (94) of the seventh MOSFET (Q7, 74); and
k. in the charger mode, the sixth gate control signal (GA) supplied to the sixth gate terminal (88) of the sixth MOSFET (Q6, 72), and the eighth gate control signal (GB) supplied to the eighth gate terminal (100) of the eighth MOSFET (Q8, 76) are such that the sixth MOSFET (Q6, 72), and the eighth MOSFET (Q8, 76) operate as a boost converter as well as a power factor corrector.

8. The inverter cum charger circuit (10) as claimed in claim 1, wherein the fourth set of components comprise a combination of an inductor (102) and a third capacitor (104).

9. The inverter cum charger circuit (10) as claimed in claim 1, wherein the first AC signal supplied to the primary side (14) of the transformer (12) in the inverter mode has a frequency of 400 Hz; and the third AC signal supplied to the secondary side (16) of the transformer (12) in the charger mode has a frequency of 400 Hz.