Power converter architecture and method for integrated fuel cell based power supplies

Abstract

A fuel cell based power supply comprises a main power converter architecture that allows the fuel cell stack to operate independently of a desired output voltage. The fuel cell stack may be directly connected to the main power converter eliminating high current switches and diodes. Switches are operable to selectively power an auxiliary component such as a cooling fan to the fuel cell stack or to a storage device via an auxiliary power converter. A single auxiliary power converter can replace a dedicated cooling fan power supply. The power supply operates in a variety of states.

We/I claim:  
     
         1 . A circuit to selectively provide power between a power source and a load, the circuit comprising: 
 a main power converter comprising a primary side and a secondary side, the primary side of the main power converter electrically coupled directly to the power source Without at least one of a switch and a diode therebetween, and the secondary side of the main power converter electrically couplable to the load; and    at least one controller coupled to control the main power converter.    
     
     
         2 . The circuit of  claim 1 , further comprising: 
 a power storage device electrically coupled in parallel across the secondary side of the main power converter.    
     
     
         3 . The circuit of  claim 1 , further comprising: 
 a power storage device electrically coupled in parallel across the secondary side of the main power converter; and    an auxiliary power converter electrically coupled between the power storage device and the at least one controller to provide power to the at least one controller from the power storage device.    
     
     
         4 . The circuit of  claim 1 , further comprising: 
 a power storage device electrically coupled in parallel across the secondary side of the main power converter;    an auxiliary power converter electrically coupled between the power storage device and the at least one controller to provide power to the at least one controller; and    at least a first switch selectively operable to electrically couple the auxiliary power converter to a first auxiliary load to provide power to the first auxiliary load from the power storage device.    
     
     
         5 . The circuit of  claim 1 , further comprising: 
 a power storage device electrically coupled in parallel across the secondary side of the main power converter;    an auxiliary power converter electrically coupled between the power storage device and the at least one controller to provide power to the at least one controller; and    at least a first switch selectively operable to electrically couple the auxiliary power converter to a first auxiliary load to provide power to the first auxiliary load from the power storage device in at least a first state, and alternatively, to electrically couple the power source to the first auxiliary load to provide power to the first auxiliary load from the power source in at least a second state.    
     
     
         6 . The circuit of  claim 1 , further comprising: 
 a super capacitor electrically coupled in parallel across the secondary side of the main power converter;    an auxiliary power converter electrically coupled between the super capacitor and the at least one controller to provide power to the at least one controller;    at least a first switch selectively operable to electrically couple the auxiliary power converter to a first auxiliary load to provide power to the first auxiliary load from the super capacitor during at least a first time; and    at least a second switch selectively operable to electrically couple the power source to the first auxiliary load to provide power to the first auxiliary load from the power source, during at least a second time different from the first time.    
     
     
         7 . The circuit of  claim 1  wherein the at least one controller is a main power converter controller, and the circuit further comprises: 
 a fuel cell controller coupled to receive user input and to control the power source and the main power converter controller.  
 
     
     
         8 . The circuit of  claim 1  wherein the main power converter is an isolated DC/DC converter comprising a transformer and a plurality of semiconductor power transistor switches configured as at least a portion of a bridge.  
     
     
         9 . The circuit of  claim 8  wherein the main power converter comprises a high frequency transformer, and the auxiliary power converter is a second isolated DC/DC converter.  
     
     
         10 . A power supply that selectively provides power to a load, the power supply comprising: 
 a fuel cell stack;    a main isolated DC/DC converter comprising a transformer, a primary side, and a secondary side, the primary side of the main isolated DC/DC converter electrically connected directly to the fuel cell stack;    a power storage device electrically coupled to the secondary side of the main isolated DC/DC converter to receive power therefrom; and    at least a first auxiliary fuel cell system component load alternatively electrically couplable to: the fuel cell stack to receive power therefrom, and the power storage device to receive power therefrom.    
     
     
         11 . The power supply of  claim 10  wherein the main isolated DC/DC converter is electrically connected directly to the fuel cell stack without at least one of a switch and a diode.  
     
     
         12 . The power supply of  claim 10  wherein the first auxiliary fuel cell system component load is a fan and driver electronics.  
     
     
         13 . The power supply of  claim 10  wherein the power storage device is at least one of a battery and a super capacitor electrically coupled in parallel across the secondary side of the main isolated DC/DC converter.  
     
     
         14 . The power supply of  claim 10 , further comprising: 
 an auxiliary isolated DC/DC converter comprising a primary side and a secondary side, the primary side electrically coupled to at least one of the power storage device and the secondary side of the main isolated DC/DC converter; and    a first controller electrically coupled to the secondary side of the auxiliary isolated DC/DC converter to receive power from the power storage device via the auxiliary isolated DC/DC converter, the first controller controllingly coupled to control the main isolated DC/DC converter.    
     
     
         15 . The power supply of  claim 10 , further comprising: 
 at least one switch selectively operable to electrically couple the first auxiliary fuel cell system component load, alternatively, to the fuel cell stack to receive power therefrom, and to the power storage device to receive power therefrom.    
     
     
         16 . The power supply of  claim 10 , further comprising: 
 an auxiliary isolated DC/DC converter comprising a primary side and a secondary side, the primary side electrically coupled to at least one of the power storage device and the secondary side of the main isolated DC/DC converter; and    at least one switch selectively operable to electrically couple the first auxiliary fuel cell system component load to the auxiliary isolated DC/DC converter to receive power from the power storage device at a first time, to electrically couple the first auxiliary fuel cell system component load to the fuel cell stack to receive power therefrom at a second time, and to electrically uncouple the first auxiliary fuel cell system component load from both the fuel cell stack and the auxiliary isolated DC/DC converter at a third time.    
     
     
         17 . The power supply of  claim 10  wherein the auxiliary fuel cell system component load is a fuel cell stack cooling fan and driver electronics, further comprising: 
 an auxiliary isolated DC/DC converter comprising a primary side and a secondary side, the primary side electrically coupled to at least one of the power storage device and the secondary side of the main isolated DC/DC converter; and  
 a first controller electrically coupled to the secondary side of the auxiliary isolated DC/DC converter to receive power via the auxiliary isolated DC/DC converter, the first controller controllingly coupled to control the main isolated DC/DC converter and at least one switch, the first controller configured to:  
 electrically couple the cooling fan to the power storage device via the auxiliary isolated DC/DC converter and electrically uncouple the cooling fan from the fuel cell stack in a startup state; and  
 electrically uncouple the cooling fan from the power storage device and electrically couple the cooling fan to the fuel cell stack in a boost state.  
 
     
     
         18 . The power supply of  claim 10  wherein the auxiliary fuel cell system component load is a fuel cell stack cooling fan, further comprising: 
 an auxiliary isolated DC/DC converter comprising a primary side and a secondary side, the primary side electrically coupled to at least one of the power storage device and the secondary side of the main isolated DC/DC converter; and  
 a first controller electrically coupled to the secondary side of the auxiliary isolated DC/DC converter to receive power via the auxiliary isolated DC/DC converter, the first controller controllingly coupled to control the main isolated DC/DC converter and at least one switch, the first controller configured to:  
 electrically couple the cooling fan to the power storage device via the auxiliary isolated DC/DC converter and electrically uncouple the cooling fan from the fuel cell stack in a startup state;  
 electrically uncouple the cooling fan from the power storage device and electrically couple the cooling fan to the fuel cell stack in a boost state;  
 electrically couple the cooling fan to the fuel cell stack and disable the main isolated DC/DC converter in an idle state;  
 electrically uncouple the cooling fan from the fuel cell stack, electrically couple the cooling fan to the power storage device and disable the main isolated DC/DC converter in a failure state; and  
 electrically uncouple the cooling fan from both the power storage device and the fuel cell stack and maintain the auxiliary isolated DC/DC converter active in a standby state.  
 
     
     
         19 . The power supply of  claim 10  wherein the main isolated DC/DC converter comprises a high frequency transformer.  
     
     
         20 . A power supply that selectively provides power to a load via a voltage bus, the power supply comprising: 
 a fuel cell stack;    a power bus to electrically couple at least one external load to the fuel cell stack, the power bus comprising a main isolated DC/DC converter wherein the main isolated DC/DC converter is the only ON/OFF switching device between the fuel cell stack and the load; and    at least one controller coupled to control the main isolated DC/DC converter.    
     
     
         21 . The power supply of  claim 20 , further comprising: 
 a power storage device electrically coupled to the main isolated DC/DC converter to receive power from the fuel cell stack via the main isolated DC/DC converter.    
     
     
         22 . The power supply of  claim 20 , further comprising: 
 a power storage device electrically coupled to the main isolated DC/DC converter to receive power from the fuel cell stack via the main isolated DC/DC converter; and    at least a first auxiliary fuel cell system component load electrically couplable alternatively to: the fuel cell stack to receive power therefrom, and the power storage device to receive power therefrom.    
     
     
         23 . A method of selectively providing power to a load from a fuel cell stack, comprising: 
 electrically directly connecting a fuel cell stack to a main isolated DC/DC converter;    selectively operating the main isolated DC/DC converter to supply power to the load at a first time, and    selectively stopping operation of the main isolated DC/DC converter to stop supplying power to the load at a second time.    
     
     
         24 . The method of  claim 23  wherein electrically directly connecting a fuel cell stack to a main isolated DC/DC converter comprises electrically connecting the fuel cell stack to the main isolated DC/DC converter without either a switch or a diode electrically coupled therebetween.  
     
     
         25 . The method of  claim 23  wherein selectively operating the main isolated DC/DC converter to supply power to the load at a first time comprises adjusting an ON state pulse-width at an operating frequency of the main isolated DC/DC converter to regulate a voltage of the power supplied to the load, while maintaining a reactant flow to the fuel cell stack approximately constant.  
     
     
         26 . The method of  claim 23 , further comprising: 
 from time-to-time, generating a current pulse to decontaminate the fuel cell stack.    
     
     
         27 . The method of  claim 23 , further comprising: 
 electrically coupling a power storage device in parallel across an output side of the main isolated DC/DC converter.    
     
     
         28 . A method of operating a fuel cell system comprising a fuel cell stack, a fan, a main isolated power converter, an auxiliary power converter, and a power converter controller, the method comprising: 
 electrically coupling a power storage device in parallel across an output side of the main isolated power converter;    supplying power to the power converter controller via the auxiliary power converter;    supplying power to the fan via the auxiliary power converter at a first time; and    supplying power to the fan directly from the fuel cell stack without the use of the auxiliary power converter at a second time.    
     
     
         29 . The method of  claim 28 , further comprising: 
 storing power from the fuel cell stack in a power storage device via the main isolated power converter, wherein supplying power to the fan via the auxiliary power converter at a first time comprises supplying power to the fan from the power storage device via the auxiliary power converter.    
     
     
         30 . A method of operating a fuel cell system comprising a fuel cell stack, a fan, a main isolated power converter, an auxiliary power converter, and a power converter controller, the method comprising: 
 electrically coupling a power storage device in parallel across an output side of the main isolated power converter;    supplying power to the power converter controller via the auxiliary power converter;    supplying power to the fan via the auxiliary power converter at a first time;    supplying power to the fan directly from the fuel cell stack without the use of the auxiliary power converter at a second time; and    operating the fuel cell stack at an approximately maximum efficiency polarization curve without regard to a desired output voltage.    
     
     
         31 . A method of operating a power supply comprising a fuel cell stack, a fan and at least one power storage device, the method comprising: 
 in a startup state, 
 supplying power to the fan from the power storage device via an auxiliary power converter; and  
   in a boost state, 
 supplying power to the fan from the fuel cell stack, and  
   enabling a main power converter to supply power to a load from the fuel cell stack via the main power converter.    
     
     
         32 . The method of  claim 31  wherein the main power converter is directly connected to the fuel cell stack without any intervening switches and diodes therebetween.  
     
     
         33 . The method of  claim 31 , further comprising: 
 in an idle state, 
 supplying power to the fan from the fuel cell stack, and  
 disabling the main power converter to prevent the supplying of power to the load from the fuel cell stack.  
   
     
     
         34 . The method of  claim 31 , further comprising: 
 in a failure state, 
 disabling the main power converter to prevent the supplying of power to the load from the fuel cell stack, and  
 supplying power to the fan from the power storage device via the auxiliary power converter.  
   
     
     
         35 . The method of  claim 31 , further comprising: 
 in a standby state, 
 operating the auxiliary power converter,  
 stopping a reactant flow to the fuel cell stack to stop the fuel cell stack from operating, and  
 disabling the main power converter to prevent the supplying of power to the load from the fuel cell stack.  
   
     
     
         36 . A power supply system, comprising: 
 a power bus;    a first power supply comprising a first fuel cell stack, a first fan, a first main power converter selectively operable to supply power to the power bus, a first power converter controller coupled to control the first main power converter, a first auxiliary power converter coupled to supply power to the first power converter controller and to selectively supply power to the first fan wherein the first fuel cell stack is selectively couplable to directly supply power to the first fan; and    at least a second power supply comprising a second fuel cell stack, a second fan, a second main power converter selectively operable to supply power to the power bus, a second power converter controller coupled to control the second main power converter, a second auxiliary power supply coupled to supply power to the second power converter controller and to selectively supply power to the second fan wherein the second fuel cell stack is selectively couplable to directly supply power to the second fan, wherein the first and the second power supplies are electrically coupled to the power bus.    
     
     
         37 . The power supply system of  claim 36  wherein the first and the second power supplies are electrically coupled to the power bus in parallel, each of the main power converters comprising a first desired output voltage.  
     
     
         38 . The power supply system of  claim 36  wherein the first and the second power supplies are electrically coupled to the power bus in series.  
     
     
         39 . The power supply system of  claim 36  wherein the first and the second main power converters are each a respective DC/DC converter comprising a bridge circuit and a transformer comprising a turns ratio selected according to a desired output voltage range.  
     
     
         40 . A method of forming a power supply system, the method comprising: 
 determining a desired voltage output of the power supply system;    selecting a DC/DC converter based on the determined desired voltage output;    determining a desired power output of the power supply system;    determining a number of power supply modules required based on the desired power output of the power supply system, each of the power supply modules comprising a respective fuel cell stack and a respective DC/DC converter;    for each of the determined number of power supply modules, electrically coupling an input of a respective one of the DC/DC converters to an output of the respective fuel cell stack; and    electrically coupling an output of each of the DC/DC converters to a power bus.    
     
     
         41 . The method of  claim 40  wherein each of the power supply modules further comprises a fan and a power storage device electrically coupled in parallel with the output of the respective fuel cell stack.