Multi-level dc-dc converter with galvanic isolation and adaptive conversion ratio

Abstract

A multi-level DC-DC converter includes an input side to receive a DC power having an input voltage and current, an output side to provide power to a load at a desired output voltage and current, and a plurality of transformer-isolated DC-DC converters connected between the input and output sides, with the transformer-isolated DC-DC converters being connected in series on one side and connected in parallel on another side. Each of the transformer isolated DC-DC converters further includes a power transformer having a primary winding and a secondary winding, and a plurality of switching devices each selectively operable in one of an On state and an Off state. Operating the switching devices in a complementary On state and Off state alternately at a controlled switching frequency provides for engaging the transformer isolated DC-DC converter and operating the switching devices in a simultaneously On state bypasses the transformer isolated DC-DC converter.

What is claimed is: 
     
         1 . A multi-level DC-DC converter comprising:
 an input side to receive a DC power having an input voltage and current;   an ouput side to provide power to a load at a desired output voltage and current;   a plurality of tranformer-isolated DC-DC converters connected between the input side and the output side, with the plurality of tranformer-isolated DC-DC converters being connected in series on one side and connected in parallel on another side; and   a controller in operable communication with each of the plurality of tranformer-isolated DC-DC converters to control operation thereof;   wherein each of the plurality of tranformer isolated DC-DC converters comprises:
 a power transformer comprising a primary winding arranged in an input side converter stage on the input side and a secondary winding arranged in an output side converter stage on the output side; and 
 a plurality of switching devices each selectively operable, via the controller, in one of an On state and an Off state to control voltage and current flow therethrough; 
 wherein the plurality of switching devices is operated at a substantially fixed frequency and duty ratio by the controller. 
   
     
     
         2 . The multi-level DC-DC converter of  claim 1  further comprising a rectifier circuit configured to rectify AC power from an AC power source to a DC power, with the DC power being provided to the plurality of tranformer isolated DC-DC converters. 
     
     
         3 . The multi-level DC-DC converter of  claim 1  wherein the plurality of switching devices in each tranformer isolated DC-DC converter comprises a half-bridge circuit. 
     
     
         4 . The multi-level DC-DC converter of  claim 1  wherein the plurality of switching devices in each tranformer isolated DC-DC converter comprises a full-bridge circuit. 
     
     
         5 . The multi-level DC-DC converter of  claim 1  wherein each of the plurality of tranformer isolated DC-DC converters further comprises one or more capacitors configured to store and release DC power received on the input side. 
     
     
         6 . The multi-level DC-DC converter of  claim 5  wherein, for each of the plurality of transformer isolated DC-DC converters, the controller is programmed to operate a plurality of switching devices in the On state so as to bypass the respective input capacitors, such that a respective transformer isolated DC-DC converter can be disengaged. 
     
     
         7 . The multi-level DC-DC converter of  claim 6  wherein the controller is programmed to selectively cause one or more of the transformer isolated DC-DC converters to be bypassed, so as to control a conversion ratio of the multi-level DC-DC converter. 
     
     
         8 . The multi-level DC-DC converter of  claim 1  wherein, for each of the plurality of transformer isolated DC-DC converters, the controller is programmed to operate the plurality of switching devices in the On state and the Off state alternately at the fixed switching frequency to engage the tranformer isolated DC-DC converter. 
     
     
         9 . The multi-level DC-DC converter of  claim 1  wherein, for each of the plurality of transformer isolated DC-DC converters, the controller is programmed to selectively operate each of the plurality of switching devices in the On state and the Off state such that the respective transformer isolated DC-DC converter is engaged at a peak of an AC cycle. 
     
     
         10 . The multi-level DC-DC converter of  claim 1  wherein one or more of the plurality of tranformer isolated DC-DC converters comprises a chopper stage to feed the input side converter stage of the respective tranformer isolated DC-DC converter, the chopper stage performing modulation to provide for regulation of the voltage and/or current output from the respective tranformer isolated DC-DC converter. 
     
     
         11 . The multi-level DC-DC converter of  claim 1  wherein the output side converter stage of each of the plurality of tranformer isolated DC-DC converters comprises one of a diode rectifier or an arrangment of active swithcing devices. 
     
     
         12 . A multi-level DC-DC converter comprising:
 an input side to receive a DC power having an input voltage and current;   an ouput side to provide power to a load at a desired output voltage and current;   a plurality of tranformer isolated DC-DC converters connected between the input side and the output side such that the plurality of tranformer isolated DC-DC converters are connected in series on one side and connected in parallel on the other side, each of the plurality of tranformer isolated DC-DC converters including:
 a bridge circuit; 
 an input capacitor arranged in parallel with the bridge circuit; and 
 a power transformer comprising a primary winding arranged on the input side and a secondary winding arranged on the output side; 
 wherein the bridge circuit and the input capacitor selectively control voltage and current flow through the respective tranformer isolated DC-DC converter. 
   
     
     
         13 . The multi-level DC-DC converter of  claim 12  further comprising a controller in operable communication with each of the plurality of tranformer isolated DC-DC converters to selectively operate each respective bridge circuit, the controller being programmed to:
 determine a desired value of a voltage conversion ratio between the input voltage and the output voltage; and 
 control operation of the bridge circuit in each respective tranformer isolated DC-DC converter based on the desired value of the voltage conversion ratio; 
 wherein one or more of the tranformer isolated DC-DC converters may be shorted based on the controlled operation of the respective bridge circuits, so as to bypass one or more of the tranformer isolated DC-DC converters and set the voltage conversion ratio to the desired value. 
 
     
     
         14 . The multi-level DC-DC converter of  claim 13  wherein, for each of the plurality of transformer isolated DC-DC converters, the controller is programmed to operate the bridge circuit so as to bypass the input capacitor, such that a respective transformer isolated DC-DC converter is bypassed. 
     
     
         15 . The multi-level DC-DC converter of  claim 12  wherein one or more of the plurality of tranformer isolated DC-DC converters comprises a chopper stage to feed the input side converter stage of the respective tranformer isolated DC-DC converter, the chopper stage performing modulation to provide for regulation of the voltage and/or current output from the respective tranformer isolated DC-DC converter. 
     
     
         16 . The multi-level DC-DC converter of  claim 12  wherein the bridge circuit in each of the plurality of tranformer isolated DC-DC converters comprises one of a half-bridge circuit and a full bridge circuit. 
     
     
         17 . A method of manufacturing a multi-level DC-DC converter, the method comprising:
 providing a plurality of tranformer isolated DC-DC converters, each of the plurality of tranformer isolated DC-DC converters comprising:
 a power transformer comprising a primary winding arranged in an input side converter stage and a secondary winding arranged in an output side converter stage; and 
 a plurality of switching devices arranged in the input side converter stage, with each of the plurality of switching devices being selectively operable in one of an On state and an Off state to control voltage and current flow to the primary winding; and 
   providing a controller that is in operable communication with each of the plurality of tranformer isolated DC-DC converters and the plurality of switching devices therein, with the controller being programmed to operate the plurality of switching devices in each respective tranformer isolated DC-DC converter in one of the On state and the Off state so as to selectively engage and disengage the respective tranformer isolated DC-DC converter.   
     
     
         18 . The method of  claim 17  wherein each of the plurality of tranformer isolated DC-DC converters further comprises one or more input capacitors that are selectively shorted based on the operation of the plurality of switching devices in one of the On state and the Off state, so as to so as to selectively engage and disengage the respective tranformer isolated DC-DC converter. 
     
     
         19 . The method of  claim 17  wherein one or more of the plurality of tranformer isolated DC-DC converters further comprises a chopper stage that performs a modulation to provide for regulation of an input voltage or current provided to a respective tranformer isolated DC-DC converter.