Multi-Phase Buck Converter Current Sharing via Reference Voltage Feedback
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Solution Overview
Problem
Existing multi-phase-buck-power-converters face issues with unequal load current sharing between buck-stages due to high input offset voltage, input offset current, and input bias current in high-speed comparators, leading to reduced maximum output current and unequal thermal power dissipation.
Innovation Solution
A multi-phase-buck-power-converter design that includes a first sub-circuit with a balanced Wheatstone measuring bridge and high-speed comparator circuits, along with a voltage control unit to regulate and correct output currents, ensuring equal reference voltages across parallel buck-stages using high-precision operational amplifiers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If high-speed comparator ICs are used for output voltage regulation, then switching frequency can be maintained at high levels (100kHz - 2MHz), but input offset voltage, input offset current and input bias current increase, leading to unequal load current share between buck-stages
Solution Approach 1:
A current sensing resistor is introduced as an intermediary element between each buck-stage and the common output node. This resistor converts the output current of each buck-stage into a proportional voltage signal that can be accurately compared by the high-speed comparator, enabling precise load current sharing while maintaining high switching frequencies.
Solution Approach 2:
The patent replaces direct voltage comparison at the comparator input with a current-based sensing approach using resistors. This substitution allows the high-speed comparator to operate with its inherent high input offset characteristics while still achieving accurate current sharing through the voltage signals developed across the sensing resistors.
2Power
If identical buck-stages are connected in parallel to increase maximum output current, then current capacity increases, but unequal load current share causes reduced maximum output current and unequal thermal power dissipation
Solution Approach 1:
The patent implements a feedback mechanism where the voltage signals from the current sensing resistors are fed back to the high-speed comparator. The comparator continuously monitors these signals and adjusts the PWM duty cycle of each buck-stage to equalize the load current distribution, ensuring reliable operation at increased power levels.
Solution Approach 2:
The patent creates an equipotential condition for current sharing by ensuring that the voltage signals at the comparator input from each buck-stage are equal when load currents are equal. This is achieved through the current sensing resistors and the comparator's ability to maintain equal voltage levels, promoting uniform current distribution across parallel buck-stages.
3Speed
If high-speed comparator ICs with high input offset current are used, then switching performance is maintained, but thermal power dissipation becomes unequal across different buck-stages
Solution Approach 1:
The feedback mechanism continuously monitors the voltage signals from current sensing resistors and adjusts each buck-stage's duty cycle to equalize power dissipation. This ensures that even with high-speed comparators having significant input offset current, the thermal distribution across parallel stages remains balanced.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design achieves nearly equal output currents across all buck-stages, resulting in higher maximum output current, balanced thermal heating, reduced hardware size and costs, and minimized power loss.
Implementation Method 1
The first sub-circuit may comprise at least a first group of resistors. The resistors of the first group of resistors are arranged as a balanced first Wheatstone measuring bridge.
Implementation Method 2
The first operational amplifier may serve as a precision proportional integral derivative (PID) controller or regulator to keep the first reference voltage of the first sub-circuit constant (and) independent of changes of the dc-output voltage.
Implementation Method 3
The third sub-circuit of each of the at least two buck-stages is configured to compare the first reference voltage of the first sub-circuit to the second reference voltage of the second sub-circuit
Implementation Method 4
a buck-converter is a DC-to-DC (DC: direct current) converter that decreases voltage and increases current from the supply to the load
Implementation Method 5
They often operate with a pulse width modulation of a high and fixed switching frequency, hereinafter also referred to as Pulse Width Modulation frequency, of 100kHz - 2MHz.
Data Source
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AI summary
The invention relates to a multi-phase-buck-power-converter. An embodiment of a multi-phase-buck-power-converter 100 comprises: a first sub-circuit 200 that is configured to supply a first reference voltage; and at least two buck-stages 500. Each buck-stage of the at least two buck-stages comprises: a second sub-circuit 300 that is configured to provide an output current, wherein the second sub-circuit 300 comprises a second resistor 320 to which a second reference voltage can be applied as a function of the output current; and a third sub-circuit 400 that is configured to compare the first reference voltage of the first sub-circuit to the second reference voltage of the second sub-circuit 300 and to correct the output current of the second sub-circuit 300 as a function of a difference between the first reference voltage and the second reference voltage. The at least two buck-stages 500 are connected in parallel to each other. The multi-phase-buck-power-converter further comprises a voltage control unit 60 configured to regulate an output voltage of the multi-phase-buck-power-converter 100.