Active LC filtering damping circuit with galvanic isolation

Abstract

Active damping of voltage across a LC output filter includes providing a feedback signal from a feedback circuit in relation to operation substantially at a resonant frequency of the LC circuit.

1 . A method of actively damping voltage across an electrical load coupled to or having a resonant LC output filter, the voltage being provided to the load by power amplifier electronics, the method comprising: 
 providing a feedback circuit operably coupled to the LC output filter, the feedback circuit having a transformer-coupled voltage feedback element;    sensing a condition of the LC output filter; and    providing a feedback signal from the feedback circuit in relation to operation substantially at a resonant frequency of the LC circuit so as to actively damp the voltage across the load.    
   
   
       2 . The method of  claim 1  wherein sensing power comprises sensing current, and the voltage feedback element comprises a current transformer.  
   
   
       3 . The method of  claim 2  wherein providing the feedback signal comprises operation of the feedback circuit at the resonant frequency of the LC output filter.  
   
   
       4 . The method of  claim 3  wherein the feedback circuit includes a sense capacitor operably connected to the LC output filter and a burden resistor operably connected to the current transformer, and wherein providing the feedback signal when a frequency of AC voltage across the sense capacitor substantially reaches the resonant frequency of the LC output filter.  
   
   
       5 . The method of  claim 3  and further comprising combining the feedback signal with a command signal to provide a system error signal to the power electronics.  
   
   
       6 . The method of  claim 1  wherein providing the feedback signal comprises operation of the feedback circuit at the resonant frequency.  
   
   
       7 . The method of  claim 1  and further comprising combining the feedback signal with a command signal to provide a system error signal to the power electronics.  
   
   
       8 . An apparatus for providing electrical power through terminals to a load wherein a LC filter circuit is connectable to the terminals, the apparatus comprising: 
 power electronics configured to provide power to a load based in part on a command signal;    a feedback circuit operably couplable to the LC output filter, the feedback circuit having a transformer-coupled voltage feedback element; and    a circuit configured to combining the command signal with the feedback signal.    
   
   
       9 . The apparatus of  claim 8  wherein the voltage feedback element comprises a current transformer.  
   
   
       10 . The apparatus of  claim 9  wherein the feedback circuit is configured to operate and provide the feedback signal at the resonant frequency of the LC output filter.  
   
   
       11 . The apparatus of  claim 9  wherein the feedback circuit includes a sense capacitor operably connected to the LC output filter and a burden resistor operably connected to the current transformer, and wherein the feedback circuit is configured to provide the feedback signal when a frequency of AC voltage across the sense capacitor substantially reaches the resonant frequency of the LC output filter.  
   
   
       12 . The apparatus of  claim 8  wherein the feedback circuit is configured to operate and provide the feedback signal at the resonant frequency of the LC output filter.  
   
   
       13 . The apparatus of  claim 12  wherein the feedback circuit is configured such that the feedback signal is proportional to current in the LC circuit at the resonant frequency.  
   
   
       14 . An apparatus for providing electrical power, the apparatus comprising: 
 power electronics configured to provide power to a load based in part on a command signal;    a LC output filter operably connected to the power electronics;    a feedback circuit operably connected to the LC output filter, the feedback circuit having a transformer-coupled voltage feedback element; and    a circuit configured to combining the command signal with the feedback signal.    
   
   
       15 . The apparatus of  claim 14  wherein the voltage feedback element comprises a current transformer.  
   
   
       16 . The apparatus of  claim 15  wherein the feedback circuit is configured to operate and provide the feedback signal at the resonant frequency of the LC output filter.  
   
   
       17 . The apparatus of  claim 15  wherein the feedback circuit includes a sense capacitor operably connected to the LC output filter and a burden resistor operably connected to the current transformer, and wherein the feedback circuit is configured to provide the feedback signal when a frequency of AC voltage across the sense capacitor substantially reaches the resonant frequency of the LC output filter.  
   
   
       18 . The apparatus of  claim 14  wherein the feedback circuit is configured to operate and provide the feedback signal at the resonant frequency of the LC output filter.  
   
   
       19 . The apparatus of  claim 18  wherein the feedback circuit is configured such that the feedback signal is proportional to current in the LC circuit at the resonant frequency.