阅读说明：本技术 移相全桥变换器的启动控制方法及移相全桥变换器 (Starting control method of phase-shifted full-bridge converter and phase-shifted full-bridge converter ) 是由 王翼 赵凯洪 郭水保 于 2021-09-16 设计创作，主要内容包括：本发明提供一种移相全桥变换器的启动控制方法及移相全桥变换器,包括：启动时,以第一控制模式进行发波,且发波的占空比为启动过程中的最低值；启动过程中,逐步增加所述占空比直至升至第一预设值,同时判断输出电流是否大于第二预设值,若大于,则将所述占空比设定为50％,再从所述第一控制模式切换到第二控制模式进行发波；否则,继续以所述第一控制模式进行发波；当所述移相全桥变换器的输出电压达到目标值,启动结束。本发明采用两种控制模式进行发波,在轻载启动时采用第一控制模式,待重载时再切换到第二控制模式,极大地降低了热损耗；此外,切换时设定两种控制模式为同等有效占空比,不会出现环路耦合问题,提高了切换的稳定性。(The invention provides a start control method of a phase-shifted full-bridge converter and the phase-shifted full-bridge converter, comprising the following steps: when starting, wave sending is carried out in a first control mode, and the duty ratio of the wave sending is the lowest value in the starting process; in the starting process, gradually increasing the duty ratio until the duty ratio is increased to a first preset value, simultaneously judging whether the output current is larger than a second preset value, if so, setting the duty ratio to be 50%, and then switching from the first control mode to a second control mode to send waves; otherwise, continuing to send waves in the first control mode; and when the output voltage of the phase-shifted full-bridge converter reaches a target value, starting the converter. The invention adopts two control modes for wave generation, adopts the first control mode when the light load is started, and switches to the second control mode when the heavy load is waited, thereby greatly reducing the heat loss; in addition, two control modes are set to be equal effective duty ratio during switching, the problem of loop coupling is solved, and the switching stability is improved.)

1. A start control method of a phase-shifted full-bridge converter is characterized by comprising the following steps:

when starting, wave sending is carried out in a first control mode, and the duty ratio of the wave sending is the lowest value in the starting process;

in the starting process, gradually increasing the duty ratio until the duty ratio is increased to a first preset value, simultaneously judging whether the output current is larger than a second preset value, if so, setting the duty ratio to be 50%, and then switching from the first control mode to a second control mode to send waves; otherwise, continuing to send waves in the first control mode;

and when the output voltage reaches the target value, starting is finished.

2. The startup control method according to claim 1, characterized in that: the phase-shifted full-bridge converter comprises a first bridge arm and a second bridge arm;

the first bridge arm comprises a first transistor and a second transistor, the second bridge arm comprises a third transistor and a fourth transistor, the first transistor and the third transistor are a first pair of transistors, and the second transistor and the fourth transistor are a second pair of transistors;

the first control mode includes: the driving signals of the first pair of transistors are the same, the driving signals of the second pair of transistors are the same, and the driving signals of the first transistor and the second transistor are complementary;

the second control mode includes: the driving signals of the first transistor and the second transistor are complementary, the driving signals of the third transistor and the fourth transistor are complementary, and a phase difference exists between the driving signals of the first transistor and the third transistor.

3. The start-up control method of claim 2, wherein the phase-shifted full-bridge converter further comprises a hardware mask window and a sampling module, the hardware mask window comprising a fifth transistor;

the first control mode further includes: when the phase-shifted full-bridge converter is started, a periodic control signal is output to a grid electrode of the fifth transistor based on the peak current of the phase-shifted full-bridge converter, and the control signal is matched with the switching period of the first transistor;

and the hardware shielding window is used for starting or stopping the sampling module according to the control signal.

4. The startup control method according to claim 2, characterized in that: the driving signals of the first transistor, the second transistor, the third transistor and the fourth transistor are all periodic signals with the same frequency.

5. The startup control method according to claim 2, characterized in that: the phase-shifted full-bridge converter also comprises a power output module, and the power output module is connected with a load;

the start control method further includes: and outputting a driving signal corresponding to the first control mode or the second control mode to a control end of the power output module, and controlling the power output module to output the converted voltage to a load end.

6. A phase-shifted full-bridge converter, comprising: the device comprises a controller, a first bridge arm, a second bridge arm, a hardware shielding window, a sampling module and a power output module;

the input end of the controller is connected with the output end of the sampling module, and the output end of the controller is respectively connected with the first bridge arm, the second bridge arm, the hardware shielding window and the control end of the power output module;

the first bridge arm and the second bridge arm are connected in parallel between a positive power supply and a negative power supply;

a first input end of the power output module is connected with a bridge arm center of the first bridge arm, a second input end of the power output module is connected with a bridge arm center of the second bridge arm, and an output end of the power output module is connected with a load;

the output end of the hardware shielding window is connected with the control end of the sampling module;

the sampling module is connected in series between a positive power supply and the first bridge arm.

7. The phase-shifted full-bridge converter according to claim 6, wherein: the first bridge arm comprises a first transistor and a second transistor, the second bridge arm comprises a third transistor and a fourth transistor, the first transistor and the third transistor are a first pair of transistors, and the second transistor and the fourth transistor are a second pair of transistors;

the controller is configured to, when starting up, perform wave generation on the first bridge arm and the second bridge arm in a first control mode, where the first control mode includes: the driving signals of the first pair of transistors are the same through the controller, the driving signals of the second pair of transistors are the same through the controller, and the driving signals of the first transistor and the second transistor are complementary through the controller;

the controller is further configured to determine whether the output current is greater than a second preset value in a starting process, and if so, perform wave generation on the first bridge arm and the second bridge arm in a second control mode, where the second control mode includes: the controller complements driving signals of the first transistor and the second transistor, the controller complements driving signals of the third transistor and the fourth transistor, and a phase difference exists between the driving signals of the first transistor and the third transistor.

8. The phase-shifted full-bridge converter according to claim 7, wherein:

the hardware shielding window comprises a first resistor, a second resistor and a fifth transistor, one end of the first resistor is connected with the output end of the controller, the other end of the first resistor is connected with one end of the second resistor and the grid electrode of the fifth transistor, the other end of the second resistor and the source electrode of the fifth transistor are respectively grounded, and the drain electrode of the fifth transistor is connected with the control end of the sampling module;

the first control mode further includes: when the inverter is started, the controller outputs a periodic control signal to the grid electrode of the fifth transistor based on the peak current of the phase-shifted full-bridge inverter, and the control signal is matched with the switching period of the first transistor.

9. The phase-shifted full-bridge converter according to claim 7, wherein: the power output module comprises a sixth transistor and a seventh transistor;

the controller is further configured to output a driving signal corresponding to the first control mode or the second control mode to the gates of the sixth transistor and the seventh transistor, and control the power output module to output the converted voltage to a load at a rear end.

10. The phase-shifted full-bridge converter according to claim 7, wherein:

the controller is also used for setting the duty ratio of the wave generation as the lowest value in the starting process when the starting is carried out, and gradually increasing the duty ratio until the duty ratio is increased to a first preset value in the starting process;

the controller is further configured to determine whether the output current is greater than a second preset value, set the duty ratio to 50% if the output current is greater than the second preset value, and switch to a second control mode to perform wave generation on the first bridge arm and the second bridge arm.

Technical Field

The invention relates to the technical field of vehicle-mounted converters, in particular to a starting control method of a phase-shifted full-bridge converter and the phase-shifted full-bridge converter.

Background

The vehicle-mounted DCDC plays a role in energy conversion between a vehicle-mounted high-voltage battery and a vehicle-mounted low-voltage battery, and the phase-shifted full bridge (PSFB) converter is widely applied to the vehicle-mounted DCDC converter due to the characteristics of high efficiency, low cost, simple design and electrical isolation. The charging device can be used for charging constant voltage type loads such as batteries and the like, and can also be used for directly supplying power to various constant resistance type or constant current type loads.

When the DCDC converter is started, the hysteresis arm is difficult to be opened softly when the current is light-load and the current is small because the hysteresis arm only has the resonance of the primary side leakage inductance and the parasitic capacitance to ensure the soft switching of the hysteresis arm, so that the power consumption is extremely high and the heat loss is serious. Therefore, PSFB mode launch requires a control operation at light load. In a traditional analog power supply circuit, a special soft start circuit is designed, extra circuit resources are needed in the method, the size is increased, the cost is increased, and the design is not flexible; secondly, because the peak current is extremely small when the load is light, the control of the peak current is extremely easy to interfere, the existing schemes are all chip internal control at present, the current schemes cannot be set automatically according to requirements, and instability and limitation exist.

Therefore, how to implement low loss of light load and stability during switching without changing hardware circuit is a technical problem that needs to be solved by those skilled in the art at present.

Disclosure of Invention

In view of the above drawbacks of the prior art, an object of the present invention is to provide a start-up control method for a phase-shifted full-bridge converter and a phase-shifted full-bridge converter, which are used to solve the problems of large loss and unstable switching during light load in the prior art.

The first aspect of the present invention provides a start control method for a phase-shifted full-bridge converter, including:

when starting, wave sending is carried out in a first control mode, and the duty ratio of the wave sending is the lowest value in the starting process;

in the starting process, gradually increasing the duty ratio until the duty ratio is increased to a first preset value, simultaneously judging whether the output current is larger than a second preset value, if so, setting the duty ratio to be 50%, and then switching from the first control mode to a second control mode to send waves; otherwise, continuing to send waves in the first control mode;

and when the output voltage of the phase-shifted full-bridge converter reaches a target value, starting the converter.

In an embodiment of the present invention, the phase-shifted full-bridge converter includes a first bridge arm and a second bridge arm;

the first bridge arm comprises a first transistor and a second transistor, the second bridge arm comprises a third transistor and a fourth transistor, the first transistor and the third transistor are a first pair of transistors, and the second transistor and the fourth transistor are a second pair of transistors;

the first control mode includes: the driving signals of the first pair of transistors are the same, the driving signals of the second pair of transistors are the same, and the driving signals of the first transistor and the second transistor are complementary;

the second control mode includes: the driving signals of the first transistor and the second transistor are complementary, the driving signals of the third transistor and the fourth transistor are complementary, and a phase difference exists between the driving signals of the first transistor and the third transistor.

In an embodiment of the present invention, the phase-shifted full-bridge converter further includes a hardware shielding window and a sampling module, wherein the hardware shielding window includes a fifth transistor;

the first control mode further includes: when the phase-shifted full-bridge converter is started, a periodic control signal is output to a grid electrode of the fifth transistor based on the peak current of the phase-shifted full-bridge converter, and the control signal is matched with the switching period of the first transistor;

and the hardware shielding window is used for starting or stopping the sampling module according to the control signal.

In an embodiment of the invention, the driving signals of the first transistor, the second transistor, the third transistor and the fourth transistor are all periodic signals with the same frequency.

In an embodiment of the present invention, the phase-shifted full-bridge converter further includes a power output module, and the power output module is connected to a load;

the start control method further includes: and outputting a driving signal corresponding to the first control mode or the second control mode to a control end of the power output module, and controlling the power output module to output the converted voltage to a load end.

The second aspect of the present invention also provides a phase-shifted full-bridge converter comprising: the device comprises a controller, a first bridge arm, a second bridge arm, a hardware shielding window, a sampling module and a power output module;

the input end of the controller is connected with the output end of the sampling module, and the output end of the controller is respectively connected with the first bridge arm, the second bridge arm, the hardware shielding window and the control end of the power output module;

the first bridge arm and the second bridge arm are connected in parallel between a positive power supply and a negative power supply;

a first input end of the power output module is connected with a bridge arm center of the first bridge arm, a second input end of the power output module is connected with a bridge arm center of the second bridge arm, and an output end of the power output module is connected with a load;

the output end of the hardware shielding window is connected with the control end of the sampling module;

the sampling module is connected in series between a positive power supply and the first bridge arm.

In an embodiment of the invention, the first bridge arm includes a first transistor and a second transistor, the second bridge arm includes a third transistor and a fourth transistor, the first transistor and the third transistor are a first pair of transistors, and the second transistor and the fourth transistor are a second pair of transistors;

the controller is configured to, when starting up, perform wave generation on the first bridge arm and the second bridge arm in a first control mode, where the first control mode includes: the driving signals of the first pair of transistors are the same through the controller, the driving signals of the second pair of transistors are the same through the controller, and the driving signals of the first transistor and the second transistor are complementary through the controller;

the controller is further configured to determine whether the output current is greater than a second preset value in a starting process, and if so, perform wave generation on the first bridge arm and the second bridge arm in a second control mode, where the second control mode includes: the controller complements driving signals of the first transistor and the second transistor, the controller complements driving signals of the third transistor and the fourth transistor, and a phase difference exists between the driving signals of the first transistor and the third transistor.

In an embodiment of the present invention, the hardware shielding window includes a first resistor, a second resistor, and a fifth transistor, one end of the first resistor is connected to the output terminal of the controller, the other end of the first resistor is connected to one end of the second resistor and the gate of the fifth transistor, the other end of the second resistor and the source of the fifth transistor are respectively grounded, and the drain of the fifth transistor is connected to the control terminal of the sampling module;

the first control mode further includes: when the inverter is started, the controller outputs a periodic control signal to the grid electrode of the fifth transistor based on the peak current of the phase-shifted full-bridge inverter, and the control signal is matched with the switching period of the first transistor.

In an embodiment of the invention, the power output module includes a sixth transistor and a seventh transistor;

the controller is further configured to output a driving signal corresponding to the first control mode or the second control mode to the gates of the sixth transistor and the seventh transistor, and control the power output module to output the converted voltage to a load at a rear end.

In an embodiment of the present invention, the controller is further configured to set a duty ratio of the wave to a lowest value in a starting process when the starting is performed, and gradually increase the duty ratio until the duty ratio is increased to a first preset value in the starting process;

the controller is further configured to determine whether the output current is greater than a second preset value, set the duty ratio to 50% if the output current is greater than the second preset value, and switch to a second control mode to perform wave generation on the first bridge arm and the second bridge arm.

As described above, the start control method of the phase-shifted full-bridge converter and the phase-shifted full-bridge converter of the invention have the following advantages:

the invention adopts two control modes for wave generation, adopts the first control mode when the light load is started, and switches to the second control mode when the heavy load is waited, thereby greatly reducing the heat loss; in addition, two control modes are set to be equal effective duty ratio during switching, the problem of loop coupling is solved, and the switching stability is improved.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the description of the embodiments of the present application will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art that other drawings can be obtained according to these drawings without inventive exercise.

Fig. 1 shows a connection schematic diagram of a phase-shifted full-bridge converter disclosed in the embodiment of the invention.

FIG. 2 is a general waveform diagram illustrating a start-up control method according to an embodiment of the present invention

Fig. 3 is a waveform diagram illustrating a first control mode disclosed in the embodiment of the present invention.

Fig. 4 is a waveform diagram illustrating a second control mode disclosed in the embodiment of the present invention.

Fig. 5 is a waveform diagram of a control signal received for a hardware mask window disclosed in the embodiment of the present invention.

Element number description:

100-phase-shifted full-bridge converter; 101-a controller; 102-a first leg; 103-a second leg;

104-hardware mask window; 105-a sampling module; 106-power output module.

Detailed Description

The following description of the embodiments of the present invention is provided for illustrative purposes, and other advantages and effects of the present invention will become apparent to those skilled in the art from the present disclosure.

Please refer to fig. 1 to 5. It should be understood that the structures, ratios, sizes, and the like shown in the drawings are only used for matching the disclosure of the specification, so as to be understood and read by those skilled in the art, and are not used to limit the conditions that the present invention can be implemented, so that the present invention has no technical significance, and any structural modification, ratio relationship change or size adjustment should still fall within the scope of the present invention without affecting the efficacy and the achievable purpose of the present invention. In addition, the terms "upper", "lower", "left", "right", "middle" and "one" used in the present specification are for clarity of description, and are not intended to limit the scope of the present invention, and the relative relationship between the terms and the terms is not to be construed as a scope of the present invention.

Referring to fig. 1, a phase-shifted full-bridge converter 100 is disclosed in a first embodiment of the present invention.

The PSFB converter 100 has input terminals respectively connected to the positive power supply V + and the negative power supply V-for converting the input energy to provide a suitable voltage for a load at the back end. PSFB converter 100 comprises controller 101, first leg 102, and second leg 103. First leg 102 includes a first transistor Q1 and a second transistor Q2, and second leg 103 includes a third transistor Q3 and a fourth transistor Q4, wherein first transistor Q1 and third transistor Q3 are a first pair of transistors, and second transistor Q2 and fourth transistor Q4 are a second pair of transistors. The drains of the first transistor Q1 and the fourth transistor Q4 are connected to a positive power supply V +, the source of the first transistor Q1 is connected to the drain of the second transistor Q2, the source of the fourth transistor Q4 is connected to the drain of the third transistor Q3, and the sources of the second transistor Q2 and the third transistor Q3 are connected to a negative power supply V-.

Controller 101 outputs first drive signal Ctrl1 to the gate of first transistor Q1, outputs second drive signal Ctrl2 to the gate of second transistor Q2, outputs third drive signal Ctrl3 to the gate of third transistor Q3, and outputs fourth drive signal Ctrl4 to the gate of fourth transistor Q4, thereby controlling first leg 102 and second leg 103 to perform wave-sending in two different control modes at startup.

Considering that the peak current of the PSFB converter 100 is very small during light load, which easily causes the duty ratio to be easily interfered during the first control mode, and the existing shielding window in the DSP chip is difficult to cover the full range, which causes false triggering, the PSFB converter 100 in this embodiment further includes a hardware shielding window 104 for starting or stopping the sampling module 105 according to the control signal of the controller 101.

The PSFB converter 100 further includes a sampling module 105, the sampling module 105 is connected in series between the positive power supply V + and the drain of the first transistor Q1, the sampling module 105 is configured to collect a peak current of the PSFB converter 100, and is a current measurement device commonly used in the prior art, and the sampling module 105 has a mature device and design method, for example, an operational amplifier and a sampling resistor may be used to convert the obtained peak current into a digital signal by inputting the digital signal to the controller 101, and the controller 101 outputs a control signal matched with the switching period of the first transistor Q1 to the hardware shielding window 104 according to the real-time peak current.

The hardware shielding window 104 includes a first resistor R1, a second resistor R2, and a fifth transistor Q5, one end of the first resistor R1 is connected to the output terminal of the controller 101, the other end of the first resistor R1 is connected to one end of the second resistor R2 and the gate of the fifth transistor Q5, the other end of the second resistor R2 and the source of the fifth transistor Q5 are grounded, respectively, and the drain of the fifth transistor Q5 is connected to the control terminal of the sampling module 105.

The PSFB converter 100 also includes a power output module 106 for outputting the converted voltage to a load at the back end. The power output module 106 includes a resonant inductor Lp, a transformer TX1, a sixth transistor Q6, a seventh transistor Q7, an inductor L1, an inductor L2, a capacitor C2, and a capacitor C3. One end of a resonant inductor Lp is used as a first input end of the power output module 106 and is connected with the bridge arm center of the first bridge arm 102, the other end of the resonant inductor Lp is connected with one end of an inductor L1 and one end of the primary side of the transformer TX1, and the other end of an inductor L1 is used as a second input end of the power output module 106 and is connected with the bridge arm center of the second bridge arm 103 and the other end of the primary side of the transformer TX 1; one end of the secondary side of the transformer TX1 is connected with the drain electrode of a sixth transistor Q6, and the other end of the secondary side of the transformer TX1 is connected with the source electrode of a seventh transistor Q7; an inductor L2, a capacitor C2 and a capacitor C3 form an LC filter, the center point of the secondary side of the transformer TX1, the connection point of the source of the sixth transistor Q6 and the drain of the seventh transistor Q7 are respectively used as the input of the LC filter, and the output end of the LC filter is connected with a load at the rear end; wherein, the gates of the sixth transistor Q6 and the seventh transistor Q7 are respectively connected with the output terminal of the controller 101.

In another embodiment, the PSFB converter 100 further comprises an input capacitor C1, the input capacitor C1 being connected in parallel between the positive supply V + and the negative supply V-for filtering the input supply.

Referring to fig. 2, based on the phase-shifted full-bridge converter in the first embodiment, a second embodiment of the present invention discloses a start control method of the phase-shifted full-bridge converter, which includes:

t at startup₀At the moment, wave sending is carried out in a first control mode, and the duty ratio of the wave sending is the lowest value in the starting process;

in the starting process, gradually increasing the duty ratio until the duty ratio is increased to a first preset value; meanwhile, judging whether the output current is larger than a second preset value, if so, determining whether the output current is larger than the second preset value₁If the time is greater than a second preset value, setting the duty ratio to be 50%, and switching from the first control mode to the second control mode to send waves; otherwise, continuing to send waves in the first control mode;

and when the output voltage of the phase-shifted full-bridge converter reaches a target value, starting the converter.

Referring to fig. 3, fig. 3 is a waveform diagram of driving signals output to first arm 102 and second arm 103 by controller 101 when a first control mode is adopted for transmitting. At this time, the driving signals of the first pair of transistors are the same, the driving signals of the second pair of transistors are the same, that is, the first driving signal and the third driving signal are the same, the second driving signal and the fourth driving signal are the same, and the first driving signal and the second driving signal are complementary. By adopting the starting mode, when the light load is started, the voltage of the transistor is only half of the input voltage, so that the heat loss during starting can be effectively reduced, but the starting mode is easy to introduce circulating current during heavy load, so that the conversion efficiency is reduced.

Referring to fig. 4, fig. 4 is a waveform diagram of driving signals output by controller 101 to first leg 102 and second leg 103 when the second control mode is adopted for transmitting signals. At this time, the first driving signal and the second driving signal are complementary, the third driving signal and the fourth driving signal are complementary, and a phase difference different from zero exists between the first driving signal and the third driving signal. By adopting the starting mode, the internal circulation of the circuit can be effectively reduced during heavy load, the temperature of the transformer is reduced, and the conversion efficiency is increased.

The first driving signal, the second driving signal, the third driving signal and the fourth driving signal are all periodic signals and have the same frequency.

It should be understood that fig. 2-4 are only schematic diagrams of the driving signals, actually, at the initial start, the duty ratio is set to the lowest value in the starting process, and in the starting process, the duty ratio is gradually increased according to the preset step length until the duty ratio is increased to the first preset value, which may be set according to the actual needs, and this embodiment is not specifically limited thereto. When the output current of the phase-shifted full-bridge converter 100 increases to the second preset value, the second preset value in this embodiment is 30A, that is, the load is considered to be a heavy load, and in order to avoid the circulating current introduced by the first control mode and reduce the conversion efficiency, the duty ratio is first set to 50%, and then the first control mode is switched to the second control mode. The first control mode and the second control mode are set to be the same effective duty ratio during switching, the difference of the peak current of the phase-shifted full-bridge converter 100 is very small, and the problem of loop coupling cannot be caused during switching, so that the two modes are stably switched.

Referring to fig. 5, in order to reduce the interference of the peak current to the duty ratio during the light load start, the first control mode further includes: at start-up, a periodic control signal is output to the gate of the fifth transistor Q5 based on the peak current of the phase-shifted full-bridge inverter 100, and the control signal matches the switching period of the first transistor Q1. With this arrangement, in each switching period of the first transistor Q1, the gate of the fifth transistor Q5 receives a high signal, and the fifth transistor Q5 is turned on, so as to stop the sampling of the sampling module 105; in other periods, the gate of the fifth transistor Q5 is low, the fifth transistor Q5 is turned off, and the sampling module 105 operates normally.

In addition, the peak current of the phase-shifted full-bridge converter 100 obtained by the module 105 is further used for comparing with a pre-stored reference current value, when the collected peak current is greater than the reference current value, the driving signal is stopped to be output, and when the collected peak current is less than the reference current value and a carrier counter in the controller 101 is cleared, the driving signal is output again, so that the wave-by-wave current limiting function is realized.

In summary, the start control method of the phase-shifted full-bridge converter and the phase-shifted full-bridge converter adopt two control modes for wave launching, adopt the first control mode when the converter is started under light load, and switch to the second control mode when the converter is started under heavy load, so that the heat loss is greatly reduced; in addition, two control modes are set to be equal effective duty ratio during switching, the problem of loop coupling is solved, and the switching stability is improved. Therefore, the invention effectively overcomes various defects in the prior art and has high industrial utilization value.

The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.