Synthesis of load-independent switch-mode power converters
First Claim
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1. A method for synthesizing load independent switching power converters of buck or buck derived type comprising:
- accepting a source of electrical energy of a constant voltage or a feedforward compensated voltage at an input,coupling through an output filter to a load to be energized at an output controlling a power flow from said input to said output,periodically enabling a power semiconductor switch for the control of said power flow,supplying a resultant control voltage signal for periodically enabling said power semiconductor switch,sampling a voltage across said load,sensing a current through said load,feeding back the sampled voltage signal in a negative feedback loop with respect to a reference voltage source and summing the two voltages passing a signal obtained as the algebraic sum of the sampled voltage and the reference voltage through a stabilizing network;
thereby producing an error voltage signal proportional to a difference between the two voltages,feeding back the sensed current signal through a current feedback circuit in a positive feedback loop with respect to said error voltage signal and summing the two signals,supplying said resultant control voltage signal, obtained as the sum of said error voltage signal and the current signal fed through said current feedback circuit, for periodically enabling said power semiconductor switch for the control of the flow of power from the input source to the output load, whereby said voltage across said load is made independent of said load.
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Abstract
A method of synthesizing load invariant switch-mode power converters comprising positive current feedback of exactly specified nature and value of its transfer function. The system transfer function independent of load is realized while stability and dynamics of the system are controlled by an additional voltage loop.
117 Citations
9 Claims
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1. A method for synthesizing load independent switching power converters of buck or buck derived type comprising:
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accepting a source of electrical energy of a constant voltage or a feedforward compensated voltage at an input, coupling through an output filter to a load to be energized at an output controlling a power flow from said input to said output, periodically enabling a power semiconductor switch for the control of said power flow, supplying a resultant control voltage signal for periodically enabling said power semiconductor switch, sampling a voltage across said load, sensing a current through said load, feeding back the sampled voltage signal in a negative feedback loop with respect to a reference voltage source and summing the two voltages passing a signal obtained as the algebraic sum of the sampled voltage and the reference voltage through a stabilizing network;
thereby producing an error voltage signal proportional to a difference between the two voltages,feeding back the sensed current signal through a current feedback circuit in a positive feedback loop with respect to said error voltage signal and summing the two signals, supplying said resultant control voltage signal, obtained as the sum of said error voltage signal and the current signal fed through said current feedback circuit, for periodically enabling said power semiconductor switch for the control of the flow of power from the input source to the output load, whereby said voltage across said load is made independent of said load. - View Dependent Claims (2, 3, 4)
- 4. The method of claim 3 wherein said equation providing transfer function of said current feedback circuit is physically implemented, thereby implementing said current feedback circuit, as a differentiator circuit with a direct current path wherein said differentiator circuit with said direct current path is arranged to provide a differentiating time constant equal to
- space="preserve" listing-type="equation">L.sub.o /KR
and a direct current gain constant equal to
space="preserve" listing-type="equation">R.sub.w /KR,Lo being the output filter inductance, K being the overall voltage gain of the pulse width modulation stage, R being the load current sense device transresistance, and Rw being the output filter inductor wire resistance.
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5. A method for synthesizing load independent switching power converters of buck or buck derived type comprising:
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accepting a source of electrical energy of a slope compensated voltage at an input, coupling through a transformer and an output filter to a load to be energized at an output, controlling a power flow from said input to said output, periodically enabling a power semiconductor switch for the control of said power flow, supplying a resultant control voltage signal for periodically enabling said power semiconductor switch, sampling a voltage across said load, sensing a current through said load, feeding back the sampled voltage signal in a negative feedback loop with respect to a reference voltage source and summing the two voltages passing a signal obtained as the algebraic sum of the sampled voltage and the reference voltage through a stabilizing network;
thereby produce an error voltage signal proportional to a difference between the two voltages,feeding back the sensed current signal through a current feedback circuit in a positive feedback loop with respect to said error voltage signal and summing the two signals, supplying said resultant control voltage signal, obtained as the sum of said error voltage signal and the current signal fed through said current feedback circuit, for periodically enabling said power semiconductor switch for the control of the flow of power from the input source to the output load, whereby said voltage across said load is made independent of said load. - View Dependent Claims (6, 7, 8, 9)
- 9. The method of claim 8 wherein said equation providing transfer function of said current feedback circuit is physically implemented, thereby implementing said current feedback circuit, as a differentiator circuit with a direct current path wherein said differentiator circuit with said direct current path is arranged to provide a differentiating time constant equal to
- space="preserve" listing-type="equation">TL.sub.o /L.sub.m
and a direct current gain constant equal to
space="preserve" listing-type="equation">1+R.sub.w T/L.sub.m,T being said switching period, Lo being the output filter inductance, Lm being the transformer magnetizing inductance, and Rw being the output filter inductor wire resistance.
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Specification