Patent Publication Number: US-8115458-B2

Title: Driver

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2009-238482, filed on Oct. 15, 2009; the entire contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a driver that drives an external device such as a motor. 
     2. Related Art 
     In a conventional technology that improves a power factor of the external device such as the motor, PFC (Power Factor Corrector) has been used. Ordinary PFC has adjusted a waveform of a current (hereinafter referred to as “charge current”) so as to have a waveform similar to a waveform of a driving voltage for the external device in order to improve the power factor. 
     However, conventional PFC (see JP-A 2006-510340 (Kokai), JP-A 2001-37254 (Kokai), JP-A H10-201248 (Kokai), and “Correcting Power Factor-Saving Cost using Digital Control- (pages 44-48, EE Times Japan April issue in 2009, on Apr. 17, 2009)”) has required a signal pass to sense the driving voltage or a driving current. Therefore, the number of elements included in the PFC has been increased. That is, a special sensor for the PFC has been required. As a result, a circuit area and a consumed power of the PFC have been increased. Therefore, a cost of manufacturing the PFC has been increased. 
     BRIEF SUMMARY OF THE INVENTION 
     According to one aspect of the present invention, there is provided a driver comprising: 
     a sensor configured to sense a driving current and a driving voltage for an external device comprising a capacitor; 
     a pulse width modulator configured to supply a pulse signal to the external device; 
     a power factor corrector comprising a phase angle estimation unit configured to estimate a phase angle variation of an input voltage to the power factor corrector based on a parameter regarding the driving current, a voltage compensator configured to compensate an error of the driving voltage, a first current estimation unit configured to estimate a variation of a charge current flowing to the capacitor based on the charge current for compensating the error by the voltage compensator and the phase angle variation estimated by the phase angle estimation unit, a second current estimation unit configured to estimate a driving current variation, and a calculator configured to calculate a duty ratio for the pulse width modulator based on the variation of the charge current estimated by the first current estimation unit and the driving current variation estimated by the second current estimation unit; and 
     a controller configured to control the driving current for the external device and to generate the parameter based on the driving current and the driving voltage sensed by the sensor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram showing a rough configuration of a driver of an embodiment of the present invention. 
         FIG. 2  is a block diagram showing an example of a configuration of the driver  10  and the external device  20  of  FIG. 1 . 
         FIG. 3  is a block diagram showing a rough configuration of PFC  14  of  FIG. 1 . 
         FIG. 4  is a circuit diagram of the driver  10  of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     An embodiment of the present invention will be described with reference to the accompanying drawings. 
     A configuration of a driver according to the embodiment will be described.  FIG. 1  is a block diagram showing a rough configuration of a driver of an embodiment of the present invention.  FIG. 2  is a block diagram showing an example of a configuration of the driver  10  and the external device  20  of  FIG. 1 .  FIG. 3  is a block diagram showing a rough configuration of PFC  14  of  FIG. 1 .  FIG. 4  is a circuit diagram of the driver  10  of  FIG. 1 . 
     The configuration of the driver according to the embodiment will be described referring to  FIG. 1 . 
     A driver  10  according to the embodiment is connected to an external device  20  that performs a predetermined operation. Furthermore, the driver  10  includes ADC (analog to digital converter)  12 , PFC  14 , a controller  16 , PWMs (Pulse Width Modulator)  18   a  and  18   b . The ADC  12  is configured to operate as a sensor that senses a driving current and a driving voltage for the external device  20 . The PFC  14  is configured to calculate a duty ratio for the PWM  18   a  in order to improve a power factor of the external device  20 . The controller  16  is configured to control the driving current for the external device  20  based on the driving current and the driving voltage sensed by the ADC  12 , and to supply a parameter for the driving current to the PFC  14 . The PWM  18   a  is configured to modulate a pulse width of a signal supplied from the ADC  12  by using the duty ratio calculated by the PFC  14  and to supply a pulse signal having a modulated pulse width to the external device  20 . The PWM  18   b  is configured to modulate a pulse width of a signal output from the controller  16  by using a predetermined duty ratio and to supply a pulse signal having a modulated pulse width to the external device  20 . 
     An example of the configuration of the driver  10  and the external device  20  of  FIG. 1  will be described referring to  FIG. 2 . 
     The external device  20  includes an air conditioner having a motor  21  and a compressor  22 , a boost converter  23 , and a 3-phase converter  24 . In addition, in the embodiment, the external device  20  is not limited to the air conditioner. For example, the external device  20  may be a fan such as ceiling fan or air fan. 
     A current is supplied to terminals I and N of the external device  20 . The boost converter  23  and the 3-phase converter  24  are configured to generate a power based on the current supplied to the terminals I and N, and to supply the power to the motor  21 . The motor  21  is configured to drive based on the current supplied from the boost converter  23  and the 3-phase converter  24 . Furthermore, the external device  20  is configured to supply the driving voltage V M  and shunt currents I U , I V , and I W  to the ADC  12 . In addition, in the embodiment, a topology of the external device  20  is not limited to a boost. For example, the topology of the external device  20  may be a buck or a boost and back. 
     The ADC  12  is configured to convert the driving voltage V M  and the shunt currents I U , I V , and I W  to digital signals V M ′, I U ′, I V ′, and I W ′, and to supply the digital signals V M ′, I U ′, I V ′, and I W ′ to the PFC  14  and the controller  16 . That is, the ADC  12  operates as the sensor that employs a three shunts system, and senses the driving current I M , and the driving voltage V M  of the external device  20  in order to supply the digital signals V M ′, I U ′, I V ′, and I W ′ to the PFC  14  and the controller  16 . 
     The controller  16  is configured to perform operations. In a first operation, the controller  16  estimates a position of the motor  21  based on the digital signals V M ′, I U ′, I V ′, and I W ′ supplied from the ADC  12  and determines a voltage V DC  applied to the motor  21 . In a second operation, the controller  16  calculates a duty ratio D 2  and supply the duty ratio D 2  to the PWM  18   b . In a third operation, the controller  16  supplies a parameter (current vector (I d , I q )) for the driving current I M  to the PFC  14 . The duty ratio D 2  is equal to a value of the voltage V DC  divided the driving voltage V M . That is, D 2 =V DC /V M . 
     The PFC  14  is configured to calculate a duty ratio D 1  based on the digital signal V M  supplied from the ADC  12  and the current vector (I d , I q ) supplied from the controller  16 , and to supply the duty ratio D 1  to the PWM  18   a . For example, the PFC  14  calculates the duty ratio D 1  using Formula 1. 
     
       
         
           
             
               
                 
                   
                     
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     The PWM  18   a  is configured to modulate a pulse width of the duty ratio D 1  supplied from the PFC  14  and supply a pulse signal P A  to the boost converter  23 . 
     The PWM  18   b  is configured to modulate a pulse width of the duty ratio D 2  supplied from the controller  16  and supply pulse signals P 1 -P 6  to the 3-phase converter  24 . 
     A configuration of the PFC  14  of  FIG. 1  will be described referring to  FIG. 3 . 
     The PFC  14  includes a phase angle estimation unit  141 , a voltage compensator  142 , a first current estimation unit  143 , a second current estimation unit  144 , a calculator  145 , and a mode selector  146 . 
     The phase angle estimation unit  141  is configured to estimate a phase angle variation Δθ of an input voltage to the PFC  14  based on the parameter (current vector (I d , I q )) supplied from the controller  16  and to supply the phase angle variation Δθ to the first current estimation unit  143 . 
     The voltage compensator  142  is configured to compensate an error of the driving voltage V M  based on the digital signal V M ′ supplied from the ADC  12  and to supply a compensated result to the first current estimation unit  143 . 
     The first current estimation unit  143  is configured to estimate a charge current variation ΔI C  of the charge current that flows to a capacitor in the external device  20  of  FIG. 1  based on the compensated result supplied from the voltage compensator  142  and the phase angle variation Δθ supplied from the phase angle estimation unit  141 , and to supply the charge current variation ΔI C  to the calculator  145 . 
     The second current estimation unit  144  is configured to estimate a driving current variation ΔI M  based on the digital signal V M ′ supplied from the ADC  12  and the parameter (current vector (I d , I q )) supplied from the controller  16 , and to supply the driving current variation ΔI M  to the calculator  145 . 
     The calculator  145  is configured to calculate the duty ratio D 1  in which the charge current I C  has a waveform similar to a waveform of the driving voltage V M  based on the charge current variation ΔI C  supplied from the first current estimation unit  143  and the driving current variation ΔI M  supplied from the second current estimation unit  144 , and to supply the duty ratio D 1  to the PWM  18   a.    
     The mode selector  146  is configured to select a current control mode for controlling the charge current I C  or a phase angle estimation mode for estimating a phase angle θ of the driving voltage V M . Preferably, the mode selector  146  is configured to periodically select the phase angle estimation mode while the current control mode is selected. The phase angle estimation unit  141  is configured to operate when a mode signal ( 2 ) for selecting the phase angle estimation mode is supplied to the phase angle estimation unit  141 , that is the mode selector  146  selects the phase angle estimation mode for estimating the phase angle θ of the driving voltage V M . 
     A configuration of the driver  10  of  FIG. 1  will be described referring to  FIG. 4 . 
     The phase angle estimation unit  141  includes a phase angle detector  141   a , a phase angle measuring unit  141   b , a phase angle calculator  141   c , and a grid voltage calculator  141   d.    
     The phase angle detector  141   a  is configured to detect a change position, at which a polarity of the phase angle θ in a function of the driving voltage V M  changes, based on the duty ratio D 1  calculated by the calculator  145 . That is, the phase angle detector  141   a  detects whether a phase angle of the input voltage to the PFC  14  becomes 0° or 90°. More specifically, the phase angle detector  141   a  adds a constant α (α&gt;0) to the duty ratio D 1  (an initial value of the duty ratio D 1  is equal to 0) supplied from the calculator  145  to calculate an estimated duty ratio D 1 ′ (D 1 ′=D 1 +α). Then the phase angle detector  141   a  calculates a cyclic driving voltage variation ΔV Mest  (ΔV Mest =((dV M /dt)−(I M /C), C indicates a capacitance of the capacitor in the external device  20 )) based on a variation of the driving voltage V M  per the estimated duty ratio D 1 ′. Then the phase angle detector  141   a  detects the change position, at which the polarity in a function of the phase angle θ of the driving voltage V M  changes, based on the cyclic driving voltage variation ΔV Mest . For example, the phase angle detector  141   a  supplies a reset signal (indicating that the phase angle θ is equal to 0°) to the phase angle measuring unit  141   b  when the cyclic driving voltage variation ΔV Mest  changes from negative to positive. Furthermore, the phase angle detector  141   a  supplies a set signal (indicating that the phase angle θ is equal to 90°) to the phase angle measuring unit  141   b  when the cyclic driving voltage variation ΔV Mest  changes from positive to negative. That is, the phase angle detector  141   a  determines whether the driving voltage V M  changes in a cycle based on a direction (from negative to positive or from positive to negative) in which the polarity in a function of the cyclic driving voltage variation ΔV Mest  changes at the change position. 
     The phase angle measuring unit  141   b  is configured to measure the phase angle θ of the driving voltage V M  based on a detected result (reset signal or set signal) of the phase angle detector  141   a  and to supply a measured result to the phase angle calculator  141   c . More specifically, the phase angle measuring unit  141   b  includes a counter that is reset or started when the change position is detected by the phase angle detector  141   a . In addition, the counter is regularly reset based on a preset input current frequency F g  (F g =1/T g ). 
     The phase angle calculator  141   c  is configured to calculate a difference between a phase angle before measured by the phase angle measuring unit  141   b  and a phase angle after measured by the phase angle measuring unit  141   b  as the phase angle variation Δθ (Δθ=(θ−θ/z)), and to supply the phase angle variation Δθ to the first current estimation unit  143 . 
     The grid voltage calculator  141   d  is configured to calculate a grid voltage V g  based on the phase angle θ measured by the phase angle measuring unit  141   b  and to supply the grid voltage V g  to the calculator  145 . 
     The voltage compensator  142  includes a voltage compensating unit PI. The voltage compensator  142  is configured to calculate an average peak I C     —     peak     —     ref  of the charge current for compensating the error of the driving voltage V M  to a predetermined target driving voltage V M     —     ref  based on a difference between the digital signal V M ′ supplied from ADC  12  and a predetermined the target driving voltage V M     —     ref , and to supply the average peak I C     —     peak     —     ref  of the charge current to the first current estimation unit  143 . The voltage compensator  142  includes a comparatively slow loop in which a feedback is performed every ten cycles in half sine wave of an alternate current, for example, 10 [Hz]. 
     The first current estimation unit  143  is configured to calculate a difference between the charge current I C (Δθ) corresponding to the phase angle variation Δθ supplied from the phase angle calculator  141   c  and the average peak I C     —     peak     —     ref  of the charge current supplied from the voltage compensator  142  as a variation ΔI C  of the charge current. 
     The second current estimation unit  144  is configured to calculate the driving current from the current vector (I d , I q ) supplied from the controller  16 , and to calculate a difference between the driving current sensed by the ADC  12  and the driving current calculated on the basis of the current vector (I d , I q ) as a variation ΔI M  (ΔI M =I M −I M /z) of the driving current. 
     The calculator  145  includes a current compensating unit PI. In an average current mode, the calculator  145  is configured to calculate the duty ratio D 1  in which the charge current I C  flowing to the capacitor has the waveform similar to the waveform of the driving voltage V M , and to supply the duty ratio D 1  to the phase angle detector  141   a  and the PWM  18   a . In order to generate the charge current I C  in which has a low distortion and a low phase lag, a feedback frequency (for example, 100 [kHz]) and a switching frequency (for example, 100 [kHz]) having comparatively high speed are required. More specifically, the current compensator PI calculates a new duty ratio D 1  from an error ΔI L     —     ava     —     error  between the charge current calculated on the basis of the average peak I C     —     peak     —     ref  and a present driving current, which is equal to the driving current corresponding to the duty ratio D 1  one cycle before, on the basis of a sum of the driving current I M . 
     The mode selector  146  generates the mode signal ( 1 ) or ( 2 ). When the mode signal ( 1 ) is generated, the current control mode for controlling the charge current I C  is performed. When the mode signal ( 2 ) is generated, the phase angle estimation mode for estimating the phase angle of the input voltage to the PFC  14 . The phase angle estimation unit  141  operates when the mode signal ( 2 ) is generated. 
     Conventionally, it has been required to sense the driving voltage and the driving current in order to improve the power factor. That is, the special sensor for PFC and the signal pass to sense the driving voltage or the driving current have been required. As a result, a circuit area and a consumed power of the driver including the PFC, and a cost of manufacturing the driver have been increased. 
     On the other hand, according to the embodiment, PFC  14  calculates the duty ratio D 1  based on the digital signal V M ′ supplied from the ADC  12  and the signal (current vector (I d , I q )) supplied from the controller  16 . That is, an application (ADC  12  and controller  16 ) for monitoring the driving voltage V M  and the driving current I M  is combined with the PFC  14 . Therefore, the special sensor for PFC  14  and the signal pass to sense the driving voltage are not substantially required. As a result, a circuit area and a consumed power of the driver  10  including the PFC  14 , a cost of manufacturing the driver  10  are reduced. 
     In addition, in the embodiment, a scope of the present invention is not limited by the phase angle detector  141   a  that performs a predetermined calculation to determine the cyclic driving voltage variation ΔV Mest . The phase angle detector  141   a  may use an arcsine table to determine the cyclic driving voltage variation ΔV Mest . In this case, the power factor can be more effectively improved. 
     In addition, in the embodiment, the scope of the present invention is not limited by the controller  16  that employs FOC (Field Oriented Control). 
     In addition, in embodiment, the driver  10  may include DSP/MCU (Digital Signal Processor/Micro Controller Unit) having one chip or two chips in which a chip of the PFC  14  is different from a chip of the other modules. 
     In addition, in embodiment, the scope of the present invention is not limited by the driver  10  that includes the sensor employing three shunts system. For example, the driver  10  may include a sensor employing one shunt system or two shunts system. The driver  10  may be the driver for 3-phase DC motor driver without a brush or AC motor. Furthermore, the driver  10  may be applied to the external device  20  except for the fan. 
     Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.