Start-up of step-up power converter with switched-capacitor network

Abstract

A step-up power-converter has stack nodes, each of which connects to a stack switch and to a pump capacitor to form a switched-capacitor network. Among the stack nodes are first and second stack-nodes. The second stack-node drives a particular stack switch from the plurality of stack switches. When all of the stack switches are open, the first voltage causes the first stack-node to have a first stack-node voltage and causes the second stack-node to have a second stack-node voltage that is less than the first stack-node voltage. During the first state, the second stack-node voltage is insufficient to drive the particular stack-switch. During the second state, the second stack-node voltage is sufficient to drive the particular stack-switch. Causing the switched-capacitor network to transition from the first state to the second state includes, among other things, causing the second stack-node voltage to become sufficient to drive the particular stack-switch.

Having described the invention and a preferred embodiment thereof, what is claimed as new and secured by Letters Patent is: 
     
         1 . An apparatus comprising a step-up power-converter, wherein said step-up power converter comprises a controller, a plurality of stack switches, and stack nodes, wherein each stack node connects to one of said stack switches and to a pump capacitor to form a switched-capacitor network that comprises an input terminal that receives a first voltage and an output terminal that outputs a second voltage that exceeds said first voltage, wherein said stack nodes comprise a first stack-node and a second stack-node, said second stack-node being configured for driving a particular stack switch from said plurality of stack switches, wherein said controller is configured to use said first voltage to cause said switched-capacitor network to transition from operating in a first state to operating in a second state by causing said switched-capacitor network to transition between a first state, in which said first voltage causes said first stack-node to have a first stack-node voltage and causes said second stack-node to have a second stack-node voltage that is less than said first stack-node voltage, said second stack-node voltage being insufficient to drive said particular stack switch, and a second state, in which said second stack-node has developed a voltage that is sufficient to drive said particular stack-switch. 
     
     
         2 . The apparatus of  claim 1 , further comprising a lockout circuit configured to transition into a state in which said lockout circuit prevents said particular stack-switch from being driven by said second stack-node. 
     
     
         3 . The apparatus of  claim 1 , further comprising a lockout circuit configured to prevent said particular stack-switch from being driven by said second stack-node when said second stack-node voltage is below a predetermined threshold. 
     
     
         4 . The apparatus of  claim 1 , further comprising a comparator having first and second inputs and an output, wherein said first input connects to a predetermined threshold voltage and wherein said second input connects to a voltage that depends on said second stack-node voltage, wherein said comparator outputs a signal indicative of whether said voltage that depends on said second stack-node voltage is equal to or greater than said predetermined threshold voltage, and wherein said signal selectively prevents said second stack-node voltage from being used to operate said particular stack-switch. 
     
     
         5 . The apparatus of  claim 1 , further comprising a first and second resistors connected across a supply voltage to form a voltage divider and a comparator having first and second inputs and an output, wherein said first input connects to a node between said first and second resistors, wherein said second input connects to a voltage source that provides a predetermined threshold voltage, wherein said output outputs a signal indicative of whether said predetermined threshold voltage is less than a voltage at said node, and wherein said signal selectively prevents said second stack-node voltage from being used to operate said particular stack-switch. 
     
     
         6 . The apparatus of  claim 1 , wherein said switched-capacitor network comprises a first stack node and a second stack node, wherein said first pump capacitor is connected to said first stack node and a second pump capacitor is connected to said second stack node, wherein a plurality of stack switches connects said second stack node to said input terminal, wherein said power converter further comprises a bypass path between said input terminal and said second stack node, wherein said bypass path bypasses said first stack node, said plurality of stack switches, and said first pump capacitor. 
     
     
         7 . The apparatus of  claim 1 , wherein said power converter comprises a path that connects said input terminal to said second stack-node and bypasses at least one other stack node, wherein said path becomes inoperative when said switched-capacitor network begins transitioning from said first state to said second state. 
     
     
         8 . The apparatus of  claim 1 , further comprising a plurality of bypass paths, each of which extends between said input terminal and one of said stack nodes, wherein each of said paths fails to conduct current from said input terminal to each of said stack nodes when said switched-capacitor network transitions from said first state to said second state. 
     
     
         9 . The apparatus of  claim 1 , wherein said power converter comprises a diode along a path that connects said first terminal and said second stack-node, wherein said path bypasses at least one of said stack nodes, wherein said diode is configured to block current from said second stack-node to said input terminal during said first and second states, wherein current flows through said path during said first state, and wherein current flow through said path ceases following transition into said second state. 
     
     
         10 . The apparatus of  claim 1 , wherein said power converter comprises a switch along a path that connects said first terminal and said first pump capacitor, wherein said path bypasses at least one other pump capacitor, wherein said switch is configured to close during said first state and to open during said second state. 
     
     
         11 . The apparatus of  claim 1 , wherein said power converter comprises a path that connects said input terminal to said output terminal, wherein current flows between said input and output terminals during said first state, and wherein current flow between said input and output terminals ceases during said second state. 
     
     
         12 . The apparatus of  claim 1 , further comprising a switch that connects to said input terminal, wherein said controller is configured to control said switch so as to cause a voltage having a predetermined slew rate to be present at said input terminal. 
     
     
         13 . The apparatus of  claim 1 , wherein said power converter comprises an input port, an intermediate capacitor connected to said input terminal, an LC filter between said input port and said input terminal, and a switch that selectively connects and disconnects said LC filter from said input terminal, wherein said controller is configured to time opening and closing of said switch to induce current in said LC filter, thereby causing charge to be delivered to said intermediate capacitor to be made available for charging said pump capacitors, wherein said controller is configured to time opening of said switch to prevent charge stored in said intermediate capacitor from escaping towards said LC filter. 
     
     
         14 . The apparatus of  claim 1 , wherein said power converter comprises an input port, an intermediate capacitor connected to said input terminal, and a boost converter connected between said input terminal and said input port, wherein said controller is configured to control said boost converter such that said boost converter provides a voltage to said input terminal, said voltage being provided to said input terminal being greater than a voltage that is being provided to said input port. 
     
     
         15 . The apparatus of  claim 1 , wherein said switched-capacitor network comprises a phase switch that connects to one of said pump capacitors opposite one of said stack nodes, wherein said controller is configured to operate said phase switch so as to collapse said first voltage during said first state. 
     
     
         16 . The apparatus of  claim 1 , wherein during said first state, said controller is configured to operate said switched-capacitor network so as to collapse said first voltage, thereby inducing current directed toward said switched-capacitor network so as to cause a voltage at said input terminal to surpass said first voltage. 
     
     
         17 . The apparatus of  claim 1 , wherein during said first state, said controller is configured to operate said switched-capacitor network so as to control a slew rate of said first voltage. 
     
     
         18 . The apparatus of  claim 1 , wherein said power converter comprises an input port, an intermediate capacitor connected to said input terminal, and a regulator connected between said input terminal and said input port, wherein said controller is configured to control said regulator such that said regulator provides a regulated voltage to said input terminal, said voltage being provided to said input terminal being greater than a voltage that is being provided to said input port.