Method of controlling a buck-boost circuit

Abstract

In accordance with some embodiments, a buck-boost circuit is contemplated which is bi-directional. That is, the buck-boost circuit be configured to produce a load voltage for a load responsive to a source voltage from a voltage source, and the buck-boost circuit may also be configured to produce a charging voltage for the voltage source responsive to a second voltage source connected to the load. In an embodiment, the buck-boost circuit may be operating in boost mode when providing the load voltage and may be operating in buck mode when providing the charging voltage.

What is claimed is: 
     
         1 . A method comprising:
 monitoring operation of a plurality of buck-boost converters operating in parallel to generate an output voltage on a first power bus responsive to an input voltage on a second power bus, wherein each of the plurality of buck-boost converters is coupled to receive a feedback voltage from the first power bus to generate the output voltage;   determining, separate from the plurality of buck-boost converters, that a voltage on the first power bus differs from a desired voltage;   generating an adjustment voltage responsive to the determining; and   adjusting the feedback voltage measured by the plurality of buck-boost converters using the adjustment voltage to cause the voltage on the first power bus to approach the desired voltage.   
     
     
         2 . The method of  claim 1 , wherein the desired voltage is a plating voltage for a flow cell battery coupled to the first power bus, and wherein the plating voltage is lower than a charging voltage generated to charge the flow cell battery. 
     
     
         3 . The method of  claim 1 , further comprising causing the plurality of buck-boost converters to operate in buck mode to charge a flow cell battery coupled to the first power bus. 
     
     
         4 . The method of  claim 3 , further comprising causing the plurality of buck-boost converters to operate in boost mode to discharge a flow cell battery and generate a voltage on the second power bus. 
     
     
         5 . The method of  claim 4 , further comprising detecting a loss of power on the second power bus and switching from buck mode to boost mode in response to detecting the loss of power. 
     
     
         6 . The method of  claim 3 , further comprising detecting power on the second power bus and switching from boost mode to buck mode in response to the detecting. 
     
     
         7 . The method of  claim 1 , further comprising:
 monitoring a voltage across an inductor in each of the plurality of buck-boost converters;   detecting a failure of a first buck-boost converter of the plurality of buck-boost converters in response to detecting a peak voltage of zero across the inductor in the first buck-boost converter; and   generating a signal to indicate the failure.   
     
     
         8 . The method of  claim 1 , further comprising limiting a current to the plurality of buck-boost converters to a defined maximum value. 
     
     
         9 . The method of  claim 8 , wherein limiting the current comprises:
 latching off a current limiter when the current to the plurality of buck-boost converters reaches the defined maximum value; and   enabling the current limiter from being latched off in response to receiving a latch release signal.   
     
     
         10 . The method of  claim 1 , further comprising:
 generating a buck enable control signal to enable buck mode in the plurality of buck-boost converters;   generating a boost enable control signal to enable boost mode in the plurality of buck-boost converters; and   disabling the plurality of buck-boost converters responsive to concurrent assertion of the buck enable control signal and the boost enable control signal.   
     
     
         11 . The method of  claim 1 , further comprising supplying current, using a surge current circuit coupled in parallel to the plurality of buck-boost converters, to the plurality of buck-boost converters during a power on event on one of the first power bus and the second power bus, wherein the surge current circuit comprises a polyfuse. 
     
     
         12 . The method of  claim 11 , wherein the polyfuse increases in temperature when supplying a surge current during use, and wherein the polyfuse is configured to create an open circuit in response to reaching a predetermined temperature during use. 
     
     
         13 . The method of  claim 1 , further comprising generating a plurality of sync signals, wherein each of the sync signals provides timing for a respective one of the buck-boost converters and each of the sync signals is out of phase with each other.