Multi-phase converter with balanced currents

Abstract

A multi-phase DC/DC converter having an output voltage and including a plurality of converter channels. Each converter channel includes a converter channel input and a converter channel output. Each converter channel is configured for generating a converter channel current and for adjusting said converter channel current in response to a control signal electrically connected to each converter channel input. A control circuit generates an error signal representative of a comparison of the converter output voltage to a reference voltage. The control circuit includes a plurality of control circuit channels, each of which correspond to a converter channel. Each control circuit channel generates a channel current signal representative of a corresponding converter channel current, and generates a differential channel current signal representative of a comparison of the channel current signal to an average current signal. The average current signal is representative of an overall average current for the converter channels. Each control circuit channel generates a differential error signal representative of a comparison of the error signal to the differential channel current signal. Each control circuit channel includes a pulse width modulator having a ramp input and a control input. The control input is electrically connected to the differential error signal. The pulse width modulator generates the control signal based upon the differential error signal. The control signal is electrically coupled to a corresponding converter channel input. The control circuit generates the average current signal.

1. A multi-phase DC/DC converter having an output voltage, said converter comprising:
 a plurality of converter channels, each of said plurality of converter channels including a converter channel input and a converter channel output, each of said plurality of converter channels being configured for generating a converter channel current and for adjusting said converter channel current in response to a control signal electrically connected to each said converter channel input;  
 a control circuit, comprising:  
 means for generating an error signal, said error signal being representative of a comparison of said output voltage to a reference voltage;  
 a plurality of control circuit channels, each of said plurality of control circuit channels corresponding to one of said plurality of converter channels, each of said plurality of control circuit channels comprising: 
 means for generating a channel current signal, said channel current signal being representative of a corresponding converter channel current;  
 means for generating a differential channel current signal, said differential channel current signal being representative of a comparison of said channel current signal to an average current signal, said average current signal being representative of an overall average current for said plurality of converter channels;  
 means for generating a differential error signal, said differential error signal being representative of a comparison of said error signal to said differential channel current signal; and  
 a pulse width modulator having a ramp input and a control input, said control input being electrically connected to said differential error signal, said pulse width modulator configured for generating said control signal, said control signal being based at least in part upon said differential error signal, said control signal being electrically coupled to a corresponding said converter channel input; and  
 
 means for generating said average current signal.  
 
     
     
       2. The multi-phase DC/DC converter of  claim 1 , wherein each of said plurality of control circuit channels further includes a respective compensation circuit. 
     
     
       3. The multi-phase DC/DC converter of  claim 2 , wherein each said compensation circuit comprises a frequency compensation circuit having at least one pole and zero, said frequency compensation circuit being configured for at least one of optimizing and stabilizing said differential channel current signal. 
     
     
       4. The multi-phase DC/DC converter of  claim 1 , wherein said means for generating a differential channel current signal comprises a first subtracting circuit configured for subtracting said channel current signal from said average current signal. 
     
     
       5. The multi-phase DC/DC converter of  claim 1 , wherein said means for generating an error signal comprises an error amplifier having a first input and a second input, said first input being electrically connected to said first input, said second input being electrically connected to a reference voltage. 
     
     
       6. The multi-phase DC/DC converter of  claim 1 , wherein said means for generating a differential error signal comprises a second subtracting circuit configured for subtracting said error signal from said differential channel current signal. 
     
     
       7. The multi-phase DC/DC converter of  claim 1 , wherein each of said plurality of control circuit channels includes a control circuit channel input, said means for generating a channel current signal comprises a current feedback path, said current feedback path electrically coupling said control circuit channel input to a corresponding said converter channel output. 
     
     
       8. The multi-phase DC/DC converter of  claim 1 , wherein said means for generating said average current signal comprises a scaling circuit and a summing circuit electrically connected to said scaling circuit, said summing circuit configured for adding together each respective said channel current signal and for generating a sum signal representative thereof, said scaling circuit configured for scaling said sum signal and for generating said average current signal. 
     
     
       9. A method of balancing a plurality of channel currents, each of said plurality of channel currents flowing in a corresponding one of a plurality of channels in a multi-phase DC/DC converter, said DC/DC converter having an output voltage, said method comprising the steps of: sensing each of said plurality of channel currents to thereby determine a plurality of channel current signals;
 averaging together said plurality of channel current signals to thereby determine an average channel current signal;    comparing each of said plurality of channel current signals to said average channel current signal to thereby determine a respective differential channel current signal for each of said plurality of channels;    further comparing said output voltage to a reference voltage to thereby determine an error signal;    furthermore comparing each said differential channel current signal to said error signal to thereby determine a respective differential error signal for each of said plurality of channels; and    adjusting each of said plurality of channel currents based at least in part upon a corresponding said differential error signal to thereby make each of said plurality of channel currents substantially equal to each other.    
     
     
       10. The method of  claim 9 , comprising the further step of stabilizing and optimizing said differential channel current signal. 
     
     
       11. The method of  claim 10 , wherein said stabilizing and optimizing step comprises filtering each said differential channel current signal with a frequency compensation circuit, said frequency compensation circuit having at least one pole and zero. 
     
     
       12. The method of  claim 9 , wherein said averaging step comprises:
 adding with a summing circuit each of said plurality of channel current signals to thereby produce a summing signal; and    scaling said summing signal with a scaling circuit to thereby produce said average channel current signal.    
     
     
       13. The method of  claim 9 , wherein said comparing step comprises subtracting with a subtracting circuit said average channel current signal from each of said plurality of channel. 
     
     
       14. The method of  claim 9 , wherein said further comparing step comprises subtracting with a subtracting circuit said reference voltage from said output voltage of said converter. 
     
     
       15. The method of  claim 9 , wherein said furthermore comparing step comprises subtracting with a subtracting circuit said error signal from each said differential channel current signal. 
     
     
       16. The method of  claim 9 , wherein said adjusting step comprises electrically coupling a respective one of each said differential error signal to an input of a corresponding pulse width modulator, each said pulse width modulator configured for issuing a control signal, each said control signal based at least in part upon a corresponding said differential error signal, each said control signal being electrically coupled to a corresponding one of said plurality of channels, each of said plurality of channels being configured for adjusting a corresponding one of said plurality of channel currents based at least in part upon said control signal to thereby make each of said plurality of channel currents substantially equal to each other. 
     
     
       17. A multi-phase DC/DC converter, comprising:
 a converter output;  
 a plurality of converter channels, each of said plurality of converter channels having a respective converter channel input and a respective converter channel output, each said converter channel output being electrically connected to said converter output, each of said plurality of converter channels being configured for sourcing a respective channel current, each of said plurality of converter channels being configured to adjust a corresponding said channel current in response to a control signal electrically connected to a corresponding said converter channel input; and  
 a control circuit, comprising: 
 a summing circuit having a plurality of summing circuit inputs and a summing circuit output;  
 a plurality of current feedback paths, each of said plurality of current feedback paths electrically connecting a respective said converter channel output to a corresponding one of said plurality of summing circuit inputs;  
 a scaling circuit having a scaling input and a scaling output, said scaling input being electrically connected to said sing circuit output;  
 a plurality of first subtraction circuits each having a first input, a second input and a first subtraction circuit output, each said second input being electrically connected to said scaling output, each said first input being electrically connected to a corresponding one of said plurality of current feedback paths;  
 an error amplifier having a reference input, an error input, and an error output, said reference input being electrically connected to a reference voltage;  
 a voltage feedback path connecting said converter output to said error input of said error amplifier;  
 a plurality of second subtraction circuits each having a first input, a second input and a second subtraction circuit output, each said first input being electrically connected to said error output, each said second input being electrically connected to a corresponding said first subtraction circuit output; and  
 a plurality of pulse width modulators each having a ramp input, a control input, and a pulse width modulator output, each said control input being electrically connected to a corresponding said second subtraction circuit output, each said ramp input being connected to a ramp voltage source, each said pulse width modulator output being electrically connected to a corresponding said converter channel input.  
 
 
     
     
       18. The DC/DC converter of  claim 17 , further comprising a plurality of frequency compensation circuits each having an input and an output, each said input being electrically connected to a corresponding said first subtraction circuit output, each said output being electrically connected to a corresponding said second input of one of said plurality of said second subtraction circuits. 
     
     
       19. A control circuit for a multi- phase DC/DC converter having an output voltage, the control circuit comprising:      an averaging circuit, responsive to a plurality of channel current signals representative of channel currents for a plurality of channels, that averages the values of the plurality of channel current signals to produce one or more signals representative of the average channel current;        an error amplifier, responsive to the output voltage and a reference signal, the error amplifier providing a common error signal; and        a plurality of pulse width modulator circuits, each responsive to the common error signal, the one or more signals representative of the average channel current, one of the plurality of channel current signals, and a second reference signal to produce a plurality of pulse width modulated signals to control the plurality of channels of the multi - phase DC/DC converter.      
     
     
       20. The control circuit of  claim 19 , wherein the averaging circuit further comprises:
   a summing circuit to add the plurality of channel current signals to produce a sum; and        a scaling circuit to produce the one or more signals representative of the average channel current from the sum.      
     
     
       21. The control circuit of  claim 19 , further comprising:
   a signal combiner circuit responsive to at least the one or more signals representative of the average channel current from the averaging circuit and producing an output signal; and        wherein the pulse width modulator circuit has at least a first input responsive to the output signal of the signal combiner circuit.      
     
     
       22. The control circuit of  claim 21 , wherein each pulse width modulator circuit has a second input responsive to the second reference signal.  
     
     
       23. The control circuit of  claim 19 , further comprises:
   a first difference circuit producing an output signal;        a second difference circuit coupled to receive an output of the averaging circuit and an associated channel current signal, the second difference circuit is adapted to output a signal that is equal to the associated channel current signal minus the one or more signals representative of the average channel current, and output of the second difference circuit is coupled to an input of the first difference circuit; and        wherein the pulse width modulator circuit has a first input responsive to the output signal of the first difference circuit.      
     
     
       24. The control circuit of  claim 23 , wherein the first difference circuit further receives an output from the error amplifier and the output of the second difference circuit.  
     
     
       25. A multi- phase DC/DC converter having an output voltage comprising:      a plurality of converter channels to supply a plurality of channel currents, each converter channel having a control input and an output; and        a control circuit coupled to the control input of each converter channel to provide each converter channel with an associated pulse width modulated signal to regulate the channel current flowing through each converter channel, the control circuit is further coupled to receive channel current signals representative of the plurality of channel currents, the control circuit comprising,      a scaling circuit, responsive to the plurality of channel current signals, that produces one or more scaled values based on the plurality of channel current signals,        an error amplifier, responsive to the output voltage and a first reference signal, the error amplifier providing a common error signal, and        a plurality of pulse width modulator circuits, each pulse width modulator circuit responsive to the common error signal, the one or more scaled values, one of the plurality of channel current signals, and a second reference signal to produce a plurality of pulse width modulated signals to control the plurality of channels of the multi - phase DC/DC converter.        
     
     
       26. The DC/DC converter of  claim 25 , wherein the scaling circuit comprises:
   a summing circuit to sum up the plurality of channel current signals; and        a scaler, responsive to an output signal from the summing circuit, that produces the one or more scaled values.      
     
     
       27. The DC/DC converter of  claim 25 , wherein the scaling circuit comprises an averaging circuit that produces one or more signals representative of the average channel current signal.  
     
     
       28. The DC/DC converter of  claim 25 , further comprising:
   a signal combiner responsive to the one or more scaled values of the scaling circuit and producing an output signal; and        wherein the pulse width modulator circuit has a first input responsive to the output signal of the signal combiner circuit.      
     
     
       29. The DC/DC converter of  claim 28 , wherein each pulse width modulator circuit has a second input responsive to the second reference signal.  
     
     
       30. A multi- phase DC/DC converter having an output voltage, the converter comprising:      a plurality of converter channels, each converter channel having a control input to receive a control signal and an output, wherein each converter channel is adapted to output a converter channel current based at least on the control signal received at the control input of the converter channel; and        a control circuit comprising,      an error amplifier to output a common error signal, the error amplifier coupled to a first reference signal and the output voltage, a summing circuit coupled to receive channel current signals representative of the converter channel currents, the summing circuit outputting a cumulative current signal representative of the summation of the channel current signals,        a scaling circuit coupled to the summing circuit and producing one or more scaled signals based on the cumulative current signal, and        a pulse width modulator for each converter channel, each pulse width modulator responsive to a combination of the one or more scaled signals, an associated channel current signal, a second reference signal, and the common error signal.        
     
     
       31. The multi- phase DC/DC converter of    claim 30   , wherein each pulse width modulator has a first and second input, the first input of each pulse width modulator coupled to a combination of three of the one or more scaled signals, an associated channel current signal, a second reference signal and the error signal and the second input of each pulse width modulator coupled to the remaining one of the signals.    
     
     
       32. The DC/DC converter of  claim 31 , wherein the scaling circuit divides the cumulative current signal by the number of converter channels to produce the one or more scaled signals.  
     
     
       33. The DC/DC converter of  claim 31 , wherein the scaling circuit multiplies the cumulative current signal by a fraction to produce the one or more scaled signals.  
     
     
       34. A control circuit for a multi- phase DC/DC converter having an output voltage, the control circuit comprising:      a scaling circuit, responsive to a plurality of channel current signals representative of channel currents for a plurality of channels, that scales the values of the plurality of channel current signals to produce one or more scaled signals;        an error amplifier, responsive to the output voltage and a reference signal, the error amplifier providing a common error signal; and        a plurality of pulse width modulator circuits, each responsive to the common error signal, the one or more scaled signals, one of the plurality of channel current signals, and a second reference signal to produce a plurality of pulse width modulated signals to control the plurality of channels of the multi - phase DC/DC converter.      
     
     
       35. A control circuit for a multi- phase DC/DC converter having an output voltage, the control circuit comprising:      a scaling circuit, responsive to a plurality of channel current signals representative of channel currents for a plurality of channels, that scales the values of the plurality of channel current signals to produce one or more scaled signals;        an error amplifier, responsive to the output voltage and a reference signal, the error amplifier providing a common error signal; and        a plurality of pulse width modulator circuits, each responsive to the common error signal, the one or more scaled signals, and one of the plurality of channel current signals to produce a plurality of pulse width modulated signals to control the plurality of channels of the multi - phase DC/DC converter.