Resonant converter with synchronous average harmonic current control

Abstract

A synchronous average harmonic current controller for a bidirectional resonant power converter provides efficient load invariant voltage gain. The controller includes a switched capacitor filter which averages and compensates a current signal over each half of the synchronous switching period. The control signal encodes an independent modulated phase and non-modulated differential duty cycle error response. The error response signals provide negative feedback to a pulse width modulation stage which results in reduction of the synchronous average harmonic current. At this operating point, the harmonic voltage gain is related closely to the commanded bridge duty cycles.

The invention claimed is: 
     
         1 . A power converter comprising:
 a first bridge circuit;   a second bridge circuit;   a phase feedback loop configured to control a difference in average current over each half switching period by adjusting a phase command, wherein the phase command causes net current flow coupling a primary harmonic voltage of the first bridge circuit and a secondary harmonic voltage of the second bridge circuit; and   a synchronous pulse width modulation process wherein a reference duty cycle is modulated to generate a phase shifted pulse width modulation waveform with prescribed average reference duty cycle.   
     
     
         2 . The power converter of  claim 1 , wherein the first bridge circuit is further comprised of a first plurality of switches arranged in a first half bridge or first full bridge configuration, and the second bridge circuit is further comprised of a second plurality of switches arranged in a second half bridge or second full bridge configuration. 
     
     
         3 . The power converter of  claim 2 , wherein an isolated transformer device is magnetically coupled between a first one or more switching nodes of the first bridge circuit and a second one or more switching nodes of the second bridge circuit. 
     
     
         4 . The power converter of  claim 3 , wherein an admittance is coupled to the isolated transformer device, wherein the admittance is further comprised of one or more inductors, or one or more capacitors, or one or more inductors and capacitors. 
     
     
         5 . The power converter of  claim 4 , wherein the first plurality of switches is driven by a first pulse width modulation process, and the second plurality of switches is driven by a second pulse width modulation process, wherein one or more of the first or second pulse width modulation processes is generated using a one or more complementary pulse width modulation processes, a one or more antiphase pulse width modulation processes, or a one or more differences of phase shifted pulse width modulation processes. 
     
     
         6 . The power converter of  claim 5 , wherein one or more of the first or second pulse width modulation processes is further comprised of a differential duty cycle relative to the prescribed average reference duty cycle. 
     
     
         7 . The power converter of  claim 6 , wherein a sensor measures a signal related to a bridge current. 
     
     
         8 . The power converter of  claim 7 , wherein the differential duty cycle is modified to control a low frequency component of the signal related to bridge current. 
     
     
         9 . The power converter of  claim 1 , wherein the phase feedback loop is further comprised of a switched capacitor filter circuit configured to average and compensate current synchronously over each half of a switching period and alternately sample each half switching period average. 
     
     
         10 . The power converter of  claim 1 , wherein the phase feedback loop is further comprised of a multiplying phase detector, an integrating error amplifier and a voltage controlled oscillator. 
     
     
         11 . The power converter of  claim 1 , wherein a low frequency bridge current is controlled using capacitive elements. 
     
     
         12 . A method comprising:
 controlling a difference in average current over each half switching period by adjusting a phase command, wherein the phase command causes net current flow that couples a primary harmonic voltage of a first bridge circuit to a secondary harmonic voltage of a second bridge circuit; and   generating a phase shifted modulation waveform with prescribed average reference duty cycle.   
     
     
         13 . The method of  claim 12 , further comprising controlling an average current over the switching period by adjusting a duty cycle command. 
     
     
         14 . The method of  claim 12 , further comprising:
 controlling a harmonic buck boost relationship between the first bridge circuit and the second bridge circuit by defining a primary differential gate signal harmonic, a secondary differential gate signal harmonic, or a primary differential gate signal harmonic and a secondary differential gate signal harmonic.   
     
     
         15 . The method of  claim 14 , further comprising generating pulse width modulation signals with harmonic content similar to a pulse width modulated duty cycle input using a complementary pulse width modulation process, an antiphase pulse width modulation process, or an opposing phase shift pulse width modulation process. 
     
     
         16 . A method comprising:
 generating a first synchronous pulse width modulated signal relative to a commanded input to control a first bridge;   generating a second synchronous pulse width modulated signal relative to a superposition of independent control signals to control a second bridge and control coupled power flow across an isolation transformer to the first bridge; and   generating the superposition of independent control signals by encoding a first control signal in a modulated time reference frame and a second control signal in a non-modulated time reference frame.   
     
     
         17 . The method of  claim 16 , further comprising encoding a phase command onto the first control signal in a modulated time reference frame. 
     
     
         18 . The method of  claim 17 , further comprising encoding a duty cycle command onto the second control signal in a modulated time reference frame.