Abstract:
This invention relates to a controller, more particularly, to a controller for driving a power transistor for obtaining improving impedance matching. An embodiment of a flow chart is revealed for the operation of the controller. The controller has frequency modulation capability with Lenz current of a loop linking to the driven power transistor to function with, Miller effect cancelling capability to its driven power transistor and fault detecting capability by detecting the absence of a Lenz current of a loop linking to the driven power transistor to function with.

Description:
FIELD OF INVENTION 
       [0001]    This invention relates to a controller, more particularly, to a controller for driving a power transistor for obtaining improving impedance matching. An embodiment of a flow chart is revealed for the operation of the controller. The controller has frequency modulation capability with Lenz current of a loop linking to the driven power transistor to function with, Miller effect cancelling capability to its driven power transistor and fault detecting capability by detecting the absence of a Lenz current of a loop linking to the driven power transistor to function with. 
       BACKGROUND INFORMATION 
       [0002]    It has been known that one important application of a PWM controller is for controlling the on/off switchings of a power transistor. 
         [0003]      FIG. 4  has shown a power transistor network which contains a first power transistor  401 , a second power transistor  402  and a third power transistor  403  respectively controlled by a PWM controller  404  of which the first power transistor  401  and the second power transistor  402  are electrically connected in series and the third power transistor  403  is electrically connected in parallel with the first power transistor  401  and the second power transistor  402 . The power transistor network tries to present both the parallel and serial connections among the three power transistors.  FIG. 4  has also shown a loop linking to the power transistor network to function with. The loop tries to be expressed in a general form containing a power source  406 , a loading  405  and the power transistor network electrically connected in series with each other. 
         [0004]    A PWM controller  404  outputs a waveform containing a baseband  4041  and a carrier  4042  modulated with the baseband  4041  for controlling the alternating on/off switchings of each power transistor. For the purpose of convenience, an “on” of the power transistor expresses the driving current from the power source  406  flowing through the power transistor and an “off” of the power transistor expresses the driving current from the power source  406  is cut off at the power transistor. 
         [0005]    When an “on” of each power transistor, a driving current from the power source  406  flows through the loop and an “off” after the previous “on” of each power transistor forms a cut-open point at the power transistor resulting in the cut-off of the driving current from the power source  406  in the loop and the formation of a Lenz current at the cut-open point opposite to its driving current from the power source  403 . As long as there is an “action”, there is a “reaction” to the “action”. Lenz current is a “reaction”, a system responding signal not a given signal, to an “action”, the driving current from the power source  406  of the loop. The system responding signal “Lenz current” contains the frequency responses of the loop including that of the loading  405  and the three power transistors  401 ,  402  and  403  shown in  FIG. 4  and the phase difference between the Lenz current and its opposite driving current is 180°. 
         [0006]    The input capacitance of a power transistor will be amplified by the power transistor, which is known as Miller effect. A very small gate capacitance of power transistor decides a very big electrical power to flow through the power transistor such as MOS power transistor, which reflects the importance of the Miller effect. Further, the discrepencies exist among the three power transistors shown in  FIG. 4  so that the three power transistors are hard to be turned “on” or “off” at the same time. 
         [0007]    If the frequency response of the loop including that of the loading  405  and the three power transistors brought by Lenz current can be modulated with the baseband of the PWM controller  404  and copied into the loop by the three power transistors, then a better impedance matchings between the PWM controller  404  and its driven power transistors can be obtained, in other words, the benefits brought by the matching are: (1) the three power transistors can easier find their respective matching points in the waveform sent by the PWM controller  404 , (2) the on/off switchings of the three power transistors will be more likely to follow the waveform sent by the PWM controller  401 , (3) the power transistor will consume less power, (4) more accurate control to the on/off switchings of the power transistor can be obtained and (5) the Miller effect can be cancelled. 
         [0008]    For example, if a square baseband  4041  and a carrier  4042  modulated with the baseband  4041  is output by the PWM controller  404  as shown in  FIG. 4  and if the carrier  4042  is a “given” high-frequency waveform nothing to do with the loop as done by the conventional PWM controller, then the waveform responded by each power transistor will be like a waveform  302  shown in  FIG. 3  with a slope with both “on”  3021  and “off”  3022  due to the unmatching and Miller effect. If the carrier  4042  modulated with the baseband  4041  shown in  FIG. 4  is Lenz waveform, then a better matching can be obtained between the PWM controller and its driven power transistor and the waveform responded by each power transistor will be almost the same to the waveform sent by the PWM controller. 
         [0009]    The Lenz current waveform can be decoupled from the loop linking to the three power transistors to function with.  FIG. 4  has shown a “Lenz waveform decoupling circuit” for decoupling the Lenz waveform from the loop into the PWM controller  404 . The “Lenz waveform decoupling circuit” will be revealed in our later invention. 
         [0010]    The present invention has provided two controllers, a first controller with one output for controlling one power transistor and a second controller with two outputs for respectively controlling two power transistors, for having frequency modulation capability with Lenz current of a loop linking to the driven power transistor to function with for improving matching, having Miller effect cancelling capability to its driven power transistor and having fault detecting capability by detecting the absence of a Lenz current of a loop linking to the driven power transistor to function with, which will be more detailedly revealed in the following “detailed description of the invention”. The controllers in the present invention have also characterized both the frequency modulation capability and the phase modulation capability. 
       SUMMARY OF THE INVENTION 
       [0011]    It&#39;s a first objective to provide a first controller with one output for driving one power transistor having frequency modulation capability with Lenz current of a loop linking to the driven power transistor to function with. 
         [0012]    It&#39;s a second objective to provide a second controller with two outputs for driving two power transistors having frequency modulation capability with Lenz current of a loop linking to the driven power transistors to function with. 
         [0013]    It&#39;s a third objective to provide a first controller with one output for driving one power transistor having both the frequency modulation and the phase modulation capabilities. 
         [0014]    It&#39;s a fourth objective to provide a second controller with two outputs for respectively driving two power transistors having both the frequency modulation and the phase modulation capabilities. 
         [0015]    It&#39;s a fifth objective to provide a first controller with one output for driving one power transistor having fault detecting capability by detecting the absence of a Lenz current of a loop linking to the driven power transistor to function with. 
         [0016]    It&#39;s a sixth objective to provide a second controller with two outputs for driving two power transistors having fault detecting capability by detecting the absence of a Lenz current of a loop linking to the driven power transistors to function with. 
         [0017]    It&#39;s a seventh objective to provide a first controller with one output for driving one power transistor having Miller effect cancelling capability to its driven power transistor. 
         [0018]    It&#39;s an eighth objective to provide a second controller with two outputs for respectively driving two power transistors having Miller effect cancelling capability to its driven power transistors. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINS 
         [0019]      FIG. 1  has shown an embodiment of a first flow chart describing the operation of a first controller for controlling one power transistor; 
           [0020]      FIG. 2  has shown an embodiment of a second flow chart describing the operation of a second controller for controlling two power transistors; 
           [0021]      FIG. 3  has shown an unmatching case of a waveform on a power transistor; and 
           [0022]      FIG. 4  has shown a loop in a general form containing a power source, a loading and a power transistor network electrically connected in series with each other of which the power transistor network contains a first power transistor, a second power transistor and a third power transistor of which the first power transistor and the second power transistor are electrically in series and the third power transistor is in parallel with the first power transistor and the second power transistor. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0023]    A first controller for driving a power transistor is operated by a first flow chart shown by a first embodiment of  FIG. 1  and a second controller for driving two power transistors is operated by a second flow chart shown by a second embodiment of  FIG. 2 . The two controllers are based on a same concept but with different numbers of outputs. 
       The First Controller 
       [0024]    A first controller for driving a power transistor is operated by steps shown by a flow chart in  FIG. 1 . For m≧1 and m=1 stands for the first round. A m th  baseband waveform and a m th  high-frequency waveform modulate together shown by a first modulation  105  in  FIG. 1 . The frequency of the high-frequency waveform is distinguishingly higher than that of the baseband waveform. A first input  103  is phase-shifted shown by a phase shifting  104  in  FIG. 1 . The m th  high-frequency waveform and the first input  103  after the phase shifting  104  modulate together shown by a second modulation  106 . With the presence of the first input  103 , the modulated waveform after the first modulation  105  is blocked against outputting shown by a first switch  108  in  FIG. 1 . A first “yes”  107  indicates the presence of the first input  103  is found. 
         [0025]    A second input  109  is used to duty-adjust the modulated waveform either after the first modulation  105  or the second modulation  106  shown by a duty adjusting  110  and the second input  109  is also used to adjust or stop generating a next baseband waveform, which is a m+1 th  baseband waveform. To stop generating the m+1 th  baseband waveform aims to shut down the first controller. 
         [0026]    Without the presence of the second input  109 , the modulated waveform either after the first modulation  105  or the second modulation  106  is output as a m th  output  113  for driving the power transistor. 
         [0027]    With the presence of the second input  109 , the modulated waveform either after the first modulation  105  or the second modulation  106  is blocked against outputting by a second switch  111  and the modulated waveform either after the first modulation  105  or the second modulation  106  after the duty adjusting  110  is output as a m th  output  113  for driving the power transistor. A second “yes”  112  indicates the presence of the second input  109 . The first controller for driving a power transistor has characterized that the first input  103  is a Lenz current of a loop linking to its driven power transistor to function with. Obviously, the Lenz current is a system responding signal not a “given” signal. 
         [0028]    Lenz current is a system responding signal, a reaction to its driving current, so that it should be there as long as the system functions normally. A fault can be detected if at any time an absence of the Lenz current is detected after a defined initiation of the first controller. When a fault is found, immediately shut down the operation of the first controller for the consideration of safety by shutting off either the baseband waveform  101  and the high-frequency waveform  102  or shutting off the first modulation  105  and the second modulation  106 .  FIG. 1  has shown a “a fault is detected when no Lenz current is detected after a defined initiation”  114  to shut off the first modulation  105  and the second modulation  106  aiming to shut down the operation of the first controller. The defined initiation is not limited, for example, it can be defined as a certain number running rounds of the flow chart shown in  FIG. 1 . The first controller for driving a power transistor has also revealed a fault detection technique by detecting the absence of Lenz current decoupled from the loop linking to the power transistor to function with. 
         [0029]    The phase in the phase shifting  104  is not limited, for example, it ranges between 0° and 360°. With the presence of the Lenz current input, the Lenz current is 180° phase-shifted by the phase-shifting  104  before being sent into the second modulation  106 . 
         [0030]    The second input  111  is not limited, for example, it can be a signal from a sensor such as temperature sensor, voltage sensor, current sensor or chemical sensor, etc., a signal from an emergency procedure such as a “stop” command, a signal from a manual control such as a control manipulated by hand or foot or a control by a software. 
       The Second Controller 
       [0031]    The first controller has one baseband waveform and one output. A second controller is based on the same concept as the first controller but with two basebands and two outputs. 
         [0032]    The second controller for driving a first power transistor and a second power transistor is operated by steps shown by an embodiment of a flow chart in  FIG. 2 . For m≧1 and m=1 stands for the initial round. A first input  204  is phase-shifted shown by a phase shifting  205  in  FIG. 2 . A m th  first baseband waveform  201  and a m th  high-frequency waveform  203  modulate together shown by a first modulation  206  in  FIG. 2 . A m th  first baseband waveform  201  and the first input  204  after the phase-shifting  205  modulate together shown by a second modulation  207 . A m th  second baseband waveform  202  and a m th  high-frequency waveform  203  modulate together shown by a third modulation  208 . A m th  second baseband waveform  202  and the first input  204  after the phase-shifting  205  modulate together shown by a fourth modulation  209 . 
         [0033]    With the presence of the first input  204 , the modulated waveform after the first modulation  206  is blocked against outputting shown by a first switch  210  and the modulated waveform after the third modulation  208  is blocked against outputting shown by a second switch  211  in  FIG. 2 . A first “yes”  220  indicates the presence of the first input  204 . 
         [0034]    A second input  215  is used to duty-adjust the modulated waveform either after the first modulation  206  or the second modulation  207  shown by a first dutyadjusting  213  and the modulated waveform either after the third modulation  208  or the fourth modulation  209  shown by a second duty-adjusting  216 , and the second input  215  is also used to adjust or stop generating a next first baseband waveform and a next second baseband waveform, which are respectively a m+1 th  first baseband waveform and a m+1 th  second baseband waveform. 
         [0035]    Without the presence of the second input  214 , the modulated waveform either after the first modulation  206  or the second modulation  207  is output as a m th  first channel output  218  for driving the first power transistor and the modulated waveform either after the third modulation  208  or the fourth modulation  209  is output as a m th  second channel output  219  for driving the second power transistor. 
         [0036]    With the presence of the second input  215 , the modulated waveform either after the first modulation  206  or the second modulation  207  is blocked against outputting by a third switch  212  and the modulated waveform either after the third modulation  208  or the fourth modulation  209  is blocked against outputting by a fourth switch  217 , instead the modulated waveform either after the first modulation  206  or the second modulation  207  after the first duty-adjusting  213  is output as a m th  first channel output  218  for driving the first power transistor and the modulated waveform either after the third modulation  208  or the fourth modulation  209  after the second duty-adjusting  216  is output as a m th  second channel output  219  for driving the second power transistor. A second “yes”  214  indicates the presence of the second input  215  is found. 
         [0037]    The phase in the phase shifting  205  is not limited, for example, it ranges between 0 degree and 360 degree. With the presence of the Lenz current, the Lenz current is 180° phase-shifted by the phase-shifting  205  before being sent into the second modulation  207  and the fourth modulation  209 . 
         [0038]    The second controller has characterized that the first input  204  is a system responding signal such as Lenz current not for a given signal. As same as revealed in the first controller in  FIG. 1 , a “no Lenz current is detected after initiation and it is verified as a fault”  221  is seen in  FIG. 2  to shut off the operation of the second controller for the consideration of safety. 
         [0039]    Lenz current is a system responding signal, a reaction to its driving current, so that it should be there as long as the system functions normally. A fault can be detected if at any time an absence of the Lenz current is detected after a defined initiation of the second controller. When a fault is detected, immediately shut down the operation of the second controller for the consideration of safety by shutting off either the first baseband waveform  201 , the second baseband waveform  202  and the high-frequency waveform  203  or shutting off the first modulation  206 , the second modulation  207 , the third modulation  208  and the fourth modulation  209 .  FIG. 2  has shown a “a fault is detected when no Lenz current is detected after a defined initiation”  221  to shut off the first baseband waveform  201 , the second baseband waveform  202  and the high-frequency waveform  203  aiming to shut down the operation of the first controller. The defined initiation is not limited, for example, it can be a certain number running rounds of the flow chart shown in  FIG. 2 . The second controller for driving two power transistors has also revealed a fault detection technique by detecting the presence of Lenz current of a loop linking to the power transistors to function with. 
         [0040]    The second input  215  is not limited, for example, it can be a signal from a sensor such as temperature sensor, voltage sensor, current sensor or chemical sensor, etc., a signal from an emergency procedure such as a “stop” command, a signal from a manual control such as a control manipulated by hand or foot or a control by a software.