# Patent

## Title
Method for estimating power of a power converter

## Abstract

A controller for estimating a power of a power converter and method of estimating the same has been introduced herein. In one embodiment, the controller includes an analog/digital converter configured to provide samples of a rectified voltage waveform corresponding to a rectified sensed voltage of the power converter. The controller also includes a processor configured to estimate a minimum value of the rectified voltage waveform in accordance with the samples and remove an offset from the rectified voltage waveform to obtain an unbiased rectified voltage waveform in accordance with the estimate of the minimum value. The controller is also configured to obtain an unbiased rectified current waveform corresponding to sensed current of the power converter and provide an average power of the power converter.

## Background
TECHNICAL FIELD
The present invention is directed, in general, to power electronics and, more specifically, to a controller for estimating a power of a power converter and method of estimating the same.
BACKGROUND
A switched-mode power converter (also referred to as a “power converter”) is a power supply or power processing circuit that converts an input voltage waveform into a specified output voltage waveform. Alternating current to direct current (“ac-dc”) power converters convert an ac input voltage into a dc output voltage. Controllers associated with the power converters manage an operation thereof by controlling conduction periods of power switches employed therein. Generally, the controllers are coupled between an input and output of the power converter in a feedback loop configuration (also referred to as a “control loop” or “closed control loop”).
A common design requirement for a power converter is to estimate an input power accurately. Sensing and signal-conditioning circuits for a rectified sensed input voltage and current invariably produce a small, but significant dc offset (also referred to as an “offset” or a “bias”), which compromises the accuracy of an input power measurement. Calibration is a common approach for correcting dc offsets, but calibration adds a significant manufacturing cost, which is problematic in a high-volume, low-cost manufacturing environment.
Accordingly, what is needed in the art is a process for producing an accurate estimate of power in a power converter or other circuit and a related method that overcomes the deficiencies in the prior art.
SUMMARY OF THE INVENTION
These and other problems are generally solved or circumvented, and technical advantages are generally achieved, by advantageous embodiments of the present invention, including a controller for estimating a power of a power converter and method of estimating the same. In one embodiment, the controller includes an analog/digital converter configured to provide samples of a rectified voltage waveform corresponding to a rectified sensed voltage of the power converter. The controller also includes a processor configured to estimate a minimum value of the rectified voltage waveform in accordance with the samples and remove an offset from the rectified voltage waveform to obtain an unbiased rectified voltage waveform in accordance with the estimate of the minimum value. The controller is also configured to obtain an unbiased rectified current waveform corresponding to sensed current of the power converter and provide an average power of the power converter.
The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter, which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures or processes for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims.



BRIEF DESCRIPTION OF THE DRAWINGS
For a more complete understanding of the present invention, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:
FIG. 1 illustrates a schematic diagram of a switched-mode power converter constructed in accordance with an embodiment;
FIG. 2 illustrates a graphical representation of representative parameters of the switched-mode power converter illustrated in FIG. 1;
FIG. 3 illustrates a graphical representation of a process to estimate an offset of the rectified voltage waveform of FIG. 2;
FIG. 4 illustrates a graphical representation of a process to estimate a minimum value of the rectified voltage waveform of FIG. 2 employing linear interpolation of samples of the rectified voltage waveform in accordance with an embodiment;
FIG. 5 illustrates a graphical representation of an unbiased rectified voltage waveform, an unbiased rectified current waveform, an instantaneous power waveform and an average power in accordance with an embodiment;
FIG. 6 illustrates a flow diagram of a method of estimating power of a power converter according to an embodiment;
FIGS. 7 to 9 illustrate graphical representations demonstrating other processes for providing an unbiased rectified voltage waveform, an unbiased rectified current waveform, an instantaneous power waveform and an average power in accordance with embodiments; and
FIG. 10 illustrated is a flow diagram of another method of estimating power of a power converter according to an embodiment.



Corresponding numerals and symbols in the different FIGUREs generally refer to corresponding parts unless otherwise indicated, and may not be redescribed in the interest of brevity after the first instance. The FIGUREs are drawn to illustrate the relevant aspects of exemplary embodiments.
DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
The making and using of the present exemplary embodiments are discussed in detail below. It should be appreciated, however, that the present invention provides many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed are merely illustrative of specific ways to make and use the invention, and do not limit the scope of the invention.
Exemplary embodiments will be described with respect to a specific context, namely, a controller for estimating a power (e.g., an input power) of a power converter and method of estimating the same. While the principles of the present invention will be described in the environment of a power converter, any application that may benefit from an estimate of power such as, without limitation, a power amplifier, a motor controller, or data processing equipment is well within the broad scope of the present invention.
Measurement of ac input power to an apparatus such as a power converter is a frequent design requirement. Alternating current input power is dependent on a product of an input voltage and current of a power converter. In an implementation of a controller for a power converter using digital techniques, input voltages and currents are typically sensed, conditioned, sampled, and processed in a processor (e.g., a digital signal controller (“DSC”)). In practice, sensing and signal-conditioning circuits invariably produce a small, but significant dc offset for a rectified sensed signal such as a voltage or a current, which compromises the accuracy of rectified sensed voltage and current and produces a resulting inaccuracy in an input power measurement. The rectified sensed signal is also subject to electronic noise, drift due to ambient temperature variations and aging of components, and even variations in the operating environment of the power converter.
As mentioned previously, calibration is a common approach for estimating dc offsets, and can be performed in conjunction with accurately measuring an ac voltage applied to a power converter. Actual voltage, current, and internal power signals are read on calibrated instruments and recorded. Voltage and current offsets are recorded for various operating conditions under varying loads and input voltages. The recorded data are processed and analyzed for estimation of offset values, which estimated values are then subtracted from the sampled voltages and currents. In this manner, dc offsets are reduced, but not eliminated. Although calibration can reduce an offset, calibration adds manufacturing and maintenance costs and leaves remaining inaccuracies due to thermal drift, aging and environmental variations.
A process for estimating ac input power includes scaling down and conditioning an input voltage and total inductor current on an individual signal conditioning circuit (“SCC”). Voltages and currents are generally simultaneously sampled and digitized by an analog-to-digital (“A/D”) converter. The sampled signals are multiplied together to produce instantaneous power at the sampling times. Instantaneous power is averaged such as by using the equation:




  
    
      P
      IN
    
    =
    
      
        1
        N
      
      ⁢
      
        
          ∑
          
            n
            =
            1
          
          N
        
        ⁢
        
          
        
        ⁢
        
          
            v
            ⁡
            
              (
              n
              )
            
          
          ⁢
          
            I
            ⁡
            
              (
              n
              )
            
          
        
      
    
  
  ,




wherein,

v(n) and i(n) are instantaneous voltage and current samples,
N represents the number of samples in a full cycle (which can be approximated by integrating over a half cycle), and
PIN is an estimate of an input power, which is affected due to the presence of offsets in the voltages and currents.
A signal-conditioning circuit may include a low-pass filter, typically a first-order or a second-order resistor-capacitor filter, for anti-aliasing before an analog signal is digitized by an analog-to-digital converter. With full-wave rectification of a voltage and/or a current signal, an output of such a low-pass filter is expected to have a residual dc component which becomes part of the filtered signal and which appears as a dc offset. When the cut-off frequency of the filter is significantly higher than the ac line frequency, for example a few hundreds of times higher, the effect of the resulting dc component is negligible. Otherwise, the dc component which results (e.g., from an anti-aliasing filter) should be differentiated from the dc offset to be eliminated. Differentiation is accomplished by a digital signal processing process that reconstructs the original rectified voltage and current signals using a DSC.
The general procedure can be described as follows. In the complex frequency domain “s,” a relationship between input and output of an anti-aliasing filter can be written as:

Y(s)=X(s)·H(s),

where “s” denotes complex frequency, X(s) is the Laplace transform of the anti-aliasing filter input signal, Y(s) is the Laplace transform of the anti-aliasing filter output signal, and H(s) is the s-domain transfer function of anti-aliasing filter. Due to digitization of the continuous-time output signal y(t) corresponding to the Laplace transform of the anti-aliasing filter output signal Y(s) into a discrete-time signal y(nTs) by an analog-to-digital converter with a sampling interval Ts and to the known transfer function of the filter formed (e.g., with a resistor-capacitor network), the original discrete-time input signal x(nTs) can then be reconstructed. In the discrete-time Z-transform domain, the original input signal X(z) can be represented as,





  
    
      X
      ⁡
      
        (
        z
        )
      
    
    =
    
      
        Y
        ⁡
        
          (
          z
          )
        
      
      
        H
        ⁡
        
          (
          z
          )
        
      
    
  
  ,




where, X(z) is the Z-transform of input signal to anti-aliasing filter, Y(z) is the Z-transform of output signal out of the anti-aliasing filter, and H(z) is the Z-transform of transfer function of anti-aliasing filter.

The transfer function H(z) can be derived as a bilinear transform as,




  
    H
    ⁡
    
      (
      z
      )
    
  
  =
  
    
      H
      ⁡
      
        (
        s
        )
      
    
    ⁢
    
      ❘
      
        s
        =
        
          
            2
            ⁢
            
              (
              
                1
                -
                
                  z
                  
                    -
                    1
                  
                
              
              )
            
          
          
            
              T
              s
            
            ⁡
            
              (
              
                1
                +
                
                  z
                  
                    -
                    1
                  
                
              
              )
            
          
        
      
    
    .
  




As a consequence, the original discrete-time signal x(nTs), or x(n) for simplicity, can be obtained in terms of an inverse Z-transform,

x(n)=Z−1[X(z)].

where x(n) represents a discretized, instantaneous voltage v(n) or current i(n) sampled prior to heavy filtering.

A signal processing approach is introduced herein to substantially remove the offset from a sampled signal. The sampled signal with the offset removed is used to estimate ac input power with better accuracy. The process may execute a software-based solution without the need for added components, and can improve digital measurement accuracy for ac input power without incrementing a bill-of-material or a build cost for its implementation. A calibration process that searches offsets under various operating conditions is considerably simplified. The result is improved productivity and reduced cost in a mass-production operation.
As introduced herein, a controller including a processor (such as a digital signal controller or a microprocessor control unit (“MCU”)) is configured to make an accurate measurement of ac input power in a power converter or other circuit. The process can be applied, without limitation, to multiphase interleaving operation of a switched-mode power converter or to the front end of a single-phase, stand-alone, power factor correction (“PFC”) switched-mode power converter.
A rectified ac voltage with an offset is sampled by an A/D converter to produce a digitized sampled signal, and the digitized sampled signal is fed to a processor. The digitized sampled signal is employed to reconstruct a complete ac signal. An averaged total inductor current, also with an offset, is also digitally sampled. Since the input ac current is substantially in phase with the ac input voltage for a properly designed power-factor correction power converter, a digitized total inductor current can be constructed as an ac signal as well, based on relevant ac input voltage information. Both synthesized ac signals are respectively processed by the processor using, for instance, digital high-pass filters to remove the respective dc offsets. At this stage, individual offsets are substantially eliminated. The resultant, reconstructed ac signals are then used to calculate input power with improved accuracy.
Turning now to FIG. 1, illustrated is a schematic diagram of a switched-mode power converter (e.g., an interleaved boost power converter) constructed in accordance with an embodiment. An ac input voltage is applied to power converter input terminals, which is rectified by a full-wave diode-bridge, not shown, to produce a rectified ac input voltage (also referred to as a “rectified input voltage”) Vin for the interleaved boost power converter. The rectified input voltage Vin is applied to input terminals A1, A2 of a power train including two interleaved and paralleled boost power converter subcircuits (power conversion circuitry) for achieving power factor correction.
A first boost power converter subcircuit is formed with an input inductor LB1, a power switch SA1, and a boost diode DA1. A second boost power converter subcircuit is formed with an input inductor LB2, a power switch SA2, and a boost diode DA2. The power switches SA1, SA2 can be n-channel metal-oxide semiconductor field-effect transistors (“MOSFETs”) that are each controlled to conduct intermittently and out of phase with a duty cycle D to produce inductor currents in the boost inductors LB1, LB2. The inductor currents in the boost inductors LB1, LB2 are conducted to the boost diodes DA1, DA2, each with a complementary duty cycle 1-D. The output currents of the first and second boost power converter subcircuits are coupled to an output filter capacitor CH. The boost diodes DA1, DA2 rectify the respective inductor currents to produce a dc output voltage Vout across the output filter capacitor CH. A diode DIR is an in-rush diode that prevents the output filter capacitor CH from being overcharged upon turn-on of the interleaved boost power converter. A capacitor CR is an input filter capacitor. A pair of terminals D1, D2 are the output terminals of the interleaved boost power converter.
The rectified input voltage Vin is sensed and scaled down with a voltage divider formed with resistors R1, R2, and a rectified sensed signal (e.g., a rectified sensed input voltage, also referred to as a “rectified sensed voltage” Vsensed) is coupled to a first signal conditioning circuit SCC1 which includes a low-pass filter for anti-alias filtering and for eliminating high-frequency noise to produce a conditioned signal representative of the rectified input voltage Vin. A sensing and conditioning offset is now present in the rectified sensed voltage Vsensed. The rectified, sensed, and conditioned voltage Vsensed can also be obtained by scaling down the ac input voltage and rectifying it with an additional diode bridge, and by feeding the scaled and rectified signal to a signal conditioning circuit.
The input current is sensed with a sense resistor RS, and a rectified current sense voltage VCS produced thereby is coupled to a second signal conditioning circuit SCC2, which also includes a low-pass filter for anti-alias filtering and for eliminating high-frequency noise to produce a signal representative of the input current. In an alternative embodiment, the input current is sensed with a current-sense transformer, with the same offset result.
The interleaved boost power converter also includes a controller 100 including the first and second signal conditioning circuits SCC1, SCC2, an A/D converter 110, a processor 120 and memory 140. The processor 120 also includes a high-pass filter (“HPF”) 130. The inputs to the controller 100 include the input current sensed with a sense resistor RS, the rectified sensed voltage Vsensed and the output voltage Vout. The controller employs the output voltage Vout to regulate the same by controlling the conduction of the power switches SA1, SA2. Those skilled in the art should understand that the controller 100 (and its respective components) may include other subsystems and circuits to control the operation of the interleaved boost power converter.
Turning now to FIG. 2, illustrated is a graphical representation of representative parameters of the switched-mode power converter illustrated in FIG. 1. In particular, FIG. 2 illustrates a waveform 210 of the rectified input voltage Vin applied to the interleaved boost power converter illustrated in FIG. 1, and a corresponding waveform (a rectified voltage waveform 220) of the rectified sensed voltage Vsensed produced by the A/D converter 110 and stored in the memory 140 of the controller 100. FIG. 2 also illustrates the offset 230 present in the rectified sensed voltage Vsensed.
Turning now to FIG. 3, illustrated is a graphical representation of a process to estimate the offset 230 of the rectified voltage waveform 220 (corresponding to a rectified sensed voltage Vsensed) of FIG. 2. With continuing reference to FIG. 1, the controller (e.g., a programmable digital control unit) 100 starts with a minimal-value searching process executed (e.g., by a firmware code—or an integrated circuit—(“IC”) based hardware implementation) to determine a minimum value of the rectified voltage waveform 220 of the rectified sensed voltage Vsensed.
If the analog signal to the A/D converter input channel is noisy, the minimum-value searching process can be performed employing a comparison of sampled data over a half line cycle or a whole line cycle. In order to ensure desired measurement accuracy, the sampling rate should be sufficiently high. If the sampled signal series or the analog signal to the A/D converter input channel is clean with no higher frequency spike than the line frequency, then the minimum-value searching process can be performed employing a comparison or a first-derivative detection process. The minimum value of the rectified voltage waveform 220 is located at a slope discontinuity over at least a half cycle thereof. In the comparison process, the controller 100 (via, for instance, an A/D converter 110) samples and compares each sample to one another in a half cycle to estimate the minimal value of the rectified voltage waveform 220. Letting y(n) represent a sample of the rectified voltage waveform 220 at sample point n, if y(1)>y(2), a minimum value of the rectified voltage waveform 220 is taken as sample y(2). If y(2)>y(3), then the minimum value of the rectified voltage waveform 220 is taken as sample y(3), else the minimum value of the rectified voltage waveform 220 is taken as sample y(2). Thus, in the first case (designated “Case 1”), the sample y(n−2) lies on the left-hand side of the minimum value of the rectified voltage waveform 220. Although this sample value is the closest one to the minimum value of the rectified voltage waveform 220, there still is an apparent difference with the minimum value thereof. In the second case (designated “Case 2”), the sample y(n−2) lies on the right-hand side of the minimum value of the rectified voltage waveform 220. Again, an apparent error in finding the minimum value of the rectified voltage waveform 220 remains. In order to find the minimum value of the rectified voltage waveform 220 with reasonable accuracy, the sampling rate should be sufficiently high, and the sample size should be sufficiently large.
For an improved low cost, high-accuracy solution, the rectified voltage waveform 220 is sampled at a lower rate, which would ordinarily introduce substantial error in identifying a minimum value thereof. The improved solution employs linear interpolation of the samples of the rectified voltage waveform 220 to make a better estimate of the minimum value thereof.
Turning now to FIG. 4, illustrated is a graphical representation of a process to estimate the minimum value of the rectified voltage waveform 220 of FIG. 2 employing linear interpolation of samples of the rectified voltage waveform 220 in accordance with an embodiment. With continuing reference to FIG. 1, the rectified voltage waveform 220 is sampled to produce a sequence of samples or sample values y(1), y(2), . . . y(n−1) and y(n). The present sample y(n) and its previous four sample values y(n−1), y(n−2), y(n−3) and y(n−4) are retained. If (y(n−3)>y(n−2) and if y(n−2)<y(n−1), then the minimum value of the rectified voltage waveform 220 lies between samples y(n−1) and y(n−2). Employing linearization for the rectified voltage waveform 220 in the vicinity of its minimum value (designated “yMIN”), it is assumed for the first case (designated “Case 1”) that a straight line through the samples y(n−4), y(n−3), y(n−2) and yMIN have an opposite slope as a straight line through the sample points y(n), y(n−1) and yMIN. In the second case (designated “Case 2”), it is assumed that a straight line through the sample points y(n−4), y(n−3) and yMIN have an opposite slope as a straight line through the sample points y(n), y(n−1), y(n−2) and yMIN. In either case, the sample y(n−2) is not needed to estimate the minimum value assuming the linear slopes. In either case, the minimum value of the rectified voltage waveform 220 can be estimated with good accuracy. Several minimum values that are obtained over several half cycles of an input voltage Vin can also be passed through a low-pass filter for averaging and noise rejection.
Turning now to FIG. 5, illustrated is a graphical representation of an unbiased rectified voltage waveform, an unbiased rectified current waveform, an instantaneous power waveform and an average power in accordance with an embodiment. With continuing reference to the preceding FIGUREs, the unbiased rectified voltage waveform 510 (corresponding to an unbiased rectified sensed voltage V′sensed) is determined by subtracting the estimated minimum value yMIN (determined above) from the rectified voltage waveform 220 (corresponding to the rectified sensed voltage Vsensed) thereby removing the offset therefrom.
As mentioned above with respect to FIG. 1, a rectified current sense voltage VCS is sensed with a sense resistor RS and provided to the second signal conditioning circuit SCC2 of the controller 100. In a process analogous to the process described above with respect to the rectified voltage waveform 220 (corresponding to the rectified sensed voltage Vsensed), another rectified voltage waveform corresponding to the rectified current sense voltage VCS is processed to remove an offset therefrom. Once a minimum value (another minimum value) of the another rectified voltage waveform is determined, an unbiased another voltage waveform (corresponding to an unbiased rectified current sense voltage V′CS) is determined by subtracting the estimated another minimum value from the another rectified voltage waveform (corresponding to the rectified current sense voltage VCS) thereby removing the offset therefrom. Thereafter, a scaling factor is applied to the unbiased another rectified voltage waveform to determine an unbiased rectified current waveform 520. An instantaneous power (illustrated as an instantaneous power waveform 530) is determined by multiplying the unbiased rectified voltage waveform 510 and the unbiased rectified current waveform 520. An average of the instantaneous power waveform 530 provides an average power 540.
Turning now to FIG. 6, illustrated is a flow diagram of a method of estimating power (e.g., an input power) of a power converter according to an embodiment. The method begins in a start module 600. A voltage (e.g., a rectified sensed voltage) of the power converter is sensed in a module 610 and a current of the power converter is sensed in a module 615. The current of the power converter may be sensed with a sense resistor and a rectified current sense voltage is produced therefrom. The respective voltages (e.g., the rectified sensed voltage and the rectified current sense voltage) are filtered (via, for instance, a signal conditioning circuit) in modules 620, 625, respectively. In a module 630, the method provides samples of a rectified voltage waveform corresponding to the rectified sensed voltage via, for instance, an A/D converter. In a module 635, the method provides samples of another rectified voltage waveform corresponding to the rectified current sense voltage via, for instance, an A/D converter.
Thereafter, a linear interpolation of the rectified voltage waveform and the another rectified voltage waveform is performed via, for instance, a processor, to estimate of a minimum value of the rectified voltage waveform and the another rectified voltage waveform in modules, 640, 645, respectively. In a module 650, an unbiased rectified voltage waveform (corresponding to an unbiased rectified sensed voltage) is determined by subtracting the estimated minimum value from the rectified voltage waveform (corresponding to the rectified sensed voltage) via, for instance, a processor, thereby removing the offset therefrom. In a module 655, another unbiased rectified voltage waveform (corresponding to an unbiased rectified current sense voltage) is determined by subtracting an estimated minimum value from the another rectified voltage waveform (corresponding to the rectified current sense voltage) via, for instance, a processor, thereby removing the offset therefrom.
In a module 660, a scaling factor is applied to the another unbiased rectified voltage waveform to provide an unbiased rectified current waveform via, for instance, a processor. The method continues by multiplying the unbiased rectified voltage waveform by the unbiased rectified current waveform to provide an instantaneous power via, for instance, a processor in a module 670. In a module 680, an average of the instantaneous power is calculated to provide an average power via, for instance, a processor. The method, thereafter, is complete in an end module 690.
Turning now to FIGS. 7 to 9, illustrated are graphical representations demonstrating other processes for providing an unbiased rectified voltage waveform, an unbiased rectified current waveform, an instantaneous power waveform and an average power in accordance with embodiments. Beginning with FIG. 7, a rectified voltage waveform 710 (corresponding, for instance, to the rectified sensed voltage Vsensed of FIG. 1 and samples of which are denoted as y(n)) and with an offset 720 is restructured to obtain a reconstructed voltage waveform 730 (samples of which are denoted as z(n)). As shown in FIG. 8 and described in more detail below, an unbiased reconstructed voltage waveform 740 (samples of which are denoted as z′(n)) is obtained from the rectified voltage waveform 710. It should be noted that yMIN is an estimate of the minimum value of the rectified voltage waveform 710 corresponding to the offset 720. The estimate of the minimum value of the rectified voltage waveform 710 may be determined as described above with respect to FIG. 4.
In a positive half cycle, (y(n)−yMIN)≧0, and the reconstructed voltage waveform 730 is given by the equation:

z(n)=y(n),

and the unbiased reconstructed voltage waveform 740 is given by the equation:

z′(n)=y(n)−yMIN.

In a negative half cycle, (y(n)−yMIN)=(yMIN−z(n)). Accordingly, in a negative half cycle, the reconstructed voltage waveform 730 is given by the equation:

z(n)=2*yMIN−y(n),

and the unbiased reconstructed voltage waveform 740 is given by the equation:

z′(n)=yMIN−y(n).

These logical and arithmetic operations can be implemented in a processor 120 using a digital process.

Alternatively and with continuing reference to FIG. 1, the reconstructed voltage waveform 730 can be applied to a high-pass filter 130 to remove the offset 720. A high-pass filter 130 can be readily implemented with a digital process on a processor 120 (e.g., a digital signal processor). The high-pass filter 130 that allows high-frequency signal components to pass through and blocks a dc offset and low-frequency components can be employed to obtain the unbiased reconstructed voltage waveform 740. The high-pass filter 130 can be implemented in a processor 120 via software with a programmable digital control unit or with specific hardware employing an integrated circuit.
A digital high-pass filter 130 can be constructed employing the equation:

z′i=α·z′i-1+β·(zi−zi-1),

where zi and zi-1 represent a sequence of samples in time of the reconstructed voltage waveform 730 with the offset 720, and z′i and z′i-1 represent a corresponding sequence of computed values of the unbiased reconstructed voltage waveform 740 with the offset 720 removed. The coefficients α and β are generally constants, 0<α<1, and 0<β, e.g., α=0.999 and β=1 for samples spaced one millisecond apart. The result of application of the equation above to the reconstructed voltage waveform 730 is to progressively remove the offset 720 a number of waveform cycles. It should be understood that while the two processes described with respect to FIGS. 7 and 8 (i.e., with or without the use of the high-pass filter 130) provide an unbiased reconstructed voltage waveform 740, the numerical values thereof may be a different.

Turning to FIG. 9, after the obtaining the unbiased reconstructed voltage waveform 740 using either process above, the unbiased rectified voltage waveform 750 is determined. The unbiased rectified voltage waveform 750 is established by reversing the sign of negative digital samples of the unbiased reconstructed voltage waveform 740. In a process analogous to the process described above with respect to the rectified voltage waveform 710 (corresponding to the rectified sensed voltage Vsensed), another rectified voltage waveform corresponding to a rectified current sense voltage VCS (e.g., a sensed current across the sense resistor Rs of FIG. 1) may be processed to remove an offset therefrom to obtain another unbiased rectified voltage waveform. Once the offset is removed, a scaling factor can be applied to the another unbiased rectified voltage waveform to obtain an unbiased rectified current waveform 760. An instantaneous power (illustrated as an instantaneous power waveform 770) is determined by multiplying the unbiased rectified voltage waveform 750 and the unbiased rectified current waveform 760. An average of the instantaneous power waveform 770 provides an average power 780.
The process to produce the unbiased rectified current waveform 760 can be simplified employing the assumption that the current waveform is in phase with its voltage counterpart due to the property of high power factor produced by a controller 100 for the power converter. This assumption simplifies a search for a minimal point in a half line cycle for the another rectified voltage waveform corresponding to a rectified current sense voltage VCS (e.g., a sensed current across the sense resistor Rs) because the minimum sample value corresponds closely in time to the minimum sample value of the rectified voltage waveform 710 (corresponding to the rectified sensed voltage Vsensed of FIG. 1). The timing of the minimum sample value of the rectified voltage waveform 710 can be taken at least as a starting value in a search for the minimum sample value of the another rectified voltage waveform corresponding to a rectified current sense voltage VCS in a half line cycle of the input voltage Vin of the power converter.
Turning now to FIG. 10, illustrated is a flow diagram of another method of estimating power (e.g., an input power) of a power converter according to an embodiment. The method that follows will describe determining an unbiased rectified voltage waveform, which may pertain to the rectified sensed voltage Vsensed and/or the rectified current sense voltage Vcs introduced with respect to FIG. 1. The method that follows assumes that a rectified voltage waveform (with an offset) has been sensed and filtered and, thereafter, begins in a start module 1000. In a module 1010, the method provides samples of a rectified voltage waveform via, for instance, an A/D converter.
Thereafter, a linear interpolation of the rectified voltage waveform is performed via, for instance, a processor, to estimate of a minimum value of the rectified voltage waveform in a module 1020. In a decisional module 1025, it is determined if the method will employ a high pass filter (“HPF”) of, for instance, a processor. If the method does not employ a high pass filter, the method continues to a module 1030 wherein an unbiased reconstructed voltage waveform (without the offset) is determined from the rectified voltage waveform employing the estimate of the minimum value via, for instance, a processor.
If the method employs a high pass filter, the method continues to a module 1040 wherein the rectified voltage waveform is then restructured via, for instance, a processor into a reconstructed voltage waveform in a module 1040. The reconstructed voltage waveform can then passed through the high pass filter to obtain the unbiased reconstructed voltage waveform in a module 1045. As mentioned above, it should be understood that while the two processes described with respect to FIG. 10 (i.e., with or without the use of the high-pass filter) provide an unbiased reconstructed voltage waveform, the numerical values thereof may be a different. Then, an unbiased rectified voltage waveform is established via, for instance, the processor by reversing the sign of negative digital samples of the unbiased reconstructed voltage waveform in a module 1050.
The modules 1010 to 1050 can be repeated on another rectified waveform corresponding to the rectified current sense voltage Vcs introduced with respect to FIG. 1 to obtain another unbiased reconstructed voltage waveform in a module 1060. In a module 1065, a scaling factor is applied to the another unbiased rectified voltage waveform to provide an unbiased rectified current waveform via, for instance, a processor. The method continues by multiplying the unbiased rectified voltage waveform by the unbiased rectified current waveform to provide an instantaneous power via, for instance, a processor in a module 1070. In a module 1080, an average of the instantaneous power is calculated to provide an average power via, for instance, a processor. The method, thereafter, is complete in an end module 1090.
Those skilled in the art should understand that the previously described embodiments of a power converter, controller, and related methods of operating the same are submitted for illustrative purposes only. In addition, various power converter topologies are well within the broad scope of the present invention. While the controller has been described in the environment of an interleaved boost power converter, it may also be applied to other systems such as, without limitation, a power amplifier and a motor controller.
For a better understanding of power converters, see “Modern DC-to-DC Power Switch-mode Power Converter Circuits,” by Rudolph P. Severns and Gordon Bloom, Van Nostrand Reinhold Company, New York, N.Y. (1985) and “Principles of Power Electronics,” by J. G. Kassakian, M. F. Schlecht and G. C. Verghese, Addison-Wesley (1991). The aforementioned references are incorporated herein by reference in their entirety.
Program or code segments making up the various embodiments may be stored in a computer readable medium. For instance, a computer program product including a program code stored in a computer readable medium (e.g., a non-transitory computer readable medium) may form various embodiments. The “computer readable medium” may include any medium that can store or transfer information. Examples of the computer readable medium include an electronic circuit, a semiconductor memory device, a read only memory (“ROM”), a flash memory, an erasable ROM (“EROM”), a floppy diskette, a compact disk (“CD”)-ROM, and the like.
As described above, the exemplary embodiment provides both a method and corresponding apparatus consisting of various modules providing functionality for performing the steps of the method. The modules may be implemented as hardware (embodied in one or more chips including an integrated circuit such as an application specific integrated circuit), or may be implemented as software or firmware for execution by a processor. In particular, in the case of firmware or software, the exemplary embodiment can be provided as a computer program product including a computer readable storage structure embodying computer program code (i.e., software or firmware) thereon for execution by the processor.
Also, although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims. For example, many of the processes discussed above can be implemented in different methodologies and replaced by other processes, or a combination thereof.
Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods, and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed, that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.

## Claims

1. A controller, comprising:
an analog/digital converter configured to provide samples of a first rectified voltage waveform and a second rectified voltage waveform; and
a processor configured to:
estimate a first minimum value of said first rectified voltage waveform and a second minimum value of said second rectified voltage waveform in accordance with said samples;
remove a first offset from said first rectified voltage waveform and a second offset from said second rectified voltage waveform to obtain a first unbiased rectified voltage waveform in accordance with said estimate of said first minimum value and a second unbiased rectified voltage waveform in accordance with said estimate of said second minimum value;
apply a scaling factor to said second unbiased rectified voltage waveform to determine an unbiased rectified current waveform;
multiply said first unbiased rectified voltage waveform and said unbiased rectified current waveform to determine an instantaneous power; and
provide an average of said instantaneous power to determine an average power.

2. The controller as recited in claim 1 wherein said processor is configured to estimate said first minimum value of said first rectified voltage waveform by employing a linear interpolation of said samples.

3. The controller as recited in claim 1, wherein
said processor is configured to perform a minimum value searching process to estimate said first minimum value of said first rectified voltage waveform.

4. The controller as recited in claim 1 further comprising a filter configured to substantially eliminate high-frequency noise from said first rectified voltage waveform.

5. The controller as recited in claim 1 wherein said processor is configured to determine a first unbiased reconstructed voltage waveform from said first rectified voltage waveform employing said estimate of said first minimum value and determine said first unbiased rectified voltage waveform by reversing a sign of negative samples of said first unbiased reconstructed voltage waveform.

6. The controller as recited in claim 1 wherein said processor is configured to restructure said first rectified voltage waveform into a first reconstructed voltage waveform.

7. The controller as recited in claim 6 wherein said processor is configured to determine a first unbiased reconstructed voltage waveform from said first reconstructed voltage waveform employing a high pass filter and determine said first unbiased rectified voltage waveform by reversing a sign of negative samples of said first unbiased reconstructed voltage waveform.

8. A method, comprising:
providing samples of a first rectified voltage waveform and a second rectified voltage waveform;
estimating a first minimum value of said first rectified voltage waveform and a second minimum value of said second rectified voltage waveform in accordance with said samples;
removing a first offset from said first rectified voltage waveform and a second offset from said second rectified voltage waveform to obtain a first unbiased rectified voltage waveform in accordance with said estimate of said first minimum value and a second unbiased rectified voltage waveform in accordance with said estimate of said second minimum value;
applying a scaling factor to said second unbiased rectified voltage waveform to determine an unbiased rectified current waveform;
multiplying said first unbiased rectified voltage waveform and said unbiased rectified current waveform to determine an instantaneous power; and
providing an average of said instantaneous power to determine an average power.

9. The method as recited in claim 8 further comprising employing a linear interpolation of said samples to estimate said first minimum value of said first rectified voltage waveform.

10. The method as recited in claim 8, further comprising performing a minimum value searching process to estimate said first minimum value of said first rectified voltage waveform.

11. The method as recited in claim 8, further comprising
substantially eliminating high-frequency noise from said first rectified voltage waveform.

12. The method as recited in claim 8 further comprising determining a first unbiased reconstructed voltage waveform from said first rectified voltage waveform employing said estimate of said first minimum value and reversing a sign of negative samples of said first unbiased reconstructed voltage waveform to determine said first unbiased rectified voltage waveform.

13. The method as recited in claim 8 further comprising restructuring said first rectified voltage waveform into a first reconstructed voltage waveform.

14. The method as recited in claim 13 further comprising determining a first unbiased reconstructed voltage waveform from said first reconstructed voltage waveform employing a high pass filter and reversing a sign of negative samples of said first unbiased reconstructed voltage waveform to determine said first unbiased rectified voltage waveform.

15. A power converter, comprising:
a power train including power conversion circuitry configured to receive a rectified sensed voltage corresponding to an input voltage of said power converter and a rectified current sense voltage corresponding to an input current of said power converter;
a controller, comprising:
an analog/digital converter configured to provide samples of a first rectified voltage waveform corresponding to said rectified sensed voltage and a second rectified voltage waveform corresponding to said rectified current sense voltage; and
a processor configured to
estimate a first minimum value of said first rectified voltage waveform and a second minimum value of said second rectified voltage waveform in accordance with said samples;
remove a first offset from said first rectified voltage waveform and a second offset from said second rectified voltage waveform to obtain a first unbiased rectified voltage waveform in accordance with said estimate of said first minimum value and a second unbiased rectified voltage waveform in accordance with said estimate of said second minimum value;
apply a scaling factor to said second unbiased rectified voltage waveform to determine an unbiased rectified current waveform;
multiply said first unbiased rectified voltage waveform and said unbiased rectified current waveform to determine an instantaneous power; and
provide an average of said instantaneous power to determine an average input power of said power converter.

16. The power converter as recited in claim 15 wherein said processor of said controller is configured to estimate said first minimum value of said first rectified voltage waveform by employing a linear interpolation of said samples.

17. The power converter as recited in claim 15, wherein
said processor of said controller is configured to perform a minimum value searching process to estimate said first minimum value of said first rectified voltage waveform.

18. The power converter as recited in claim 15 wherein said controller further comprises a filter configured to substantially eliminate high-frequency noise from said first rectified voltage waveform.

19. The power converter as recited in claim 15 wherein said processor of said controller is configured to determine a first unbiased reconstructed voltage waveform from said first rectified voltage waveform employing said estimate of said first minimum value and determine said first unbiased rectified voltage waveform by reversing a sign of negative samples of said first unbiased reconstructed voltage waveform.

20. The power converter as recited in claim 15 wherein said processor of said controller is configured to restructure said first rectified voltage waveform into a first reconstructed voltage waveform, determine a first unbiased reconstructed voltage waveform from said first reconstructed voltage waveform employing a high pass filter and determine said first unbiased rectified voltage waveform by reversing a sign of negative samples of said first unbiased reconstructed voltage waveform.