Phase-Multiplexed Stacked Buck Converter for Low-Ripple EMI Control
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Solution Overview
Problem
Current series stacked DC-DC power converters exhibit low efficiency, substantial inductor equivalent series resistance (ESR) rise, and undesirable electromagnetic interference (EMI) spectrum, particularly in battery-powered IoT applications with high input voltage and low nominal output current.
Innovation Solution
A phase multiplexed series stacked DC-DC power converter circuit that alternately turns on and off top-phase and bottom-phase buck converters, using a control circuit to regulate voltage at a junction node within the converter, thereby reducing output voltage ripple and EMI, and moving fluctuations to an internal node.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If series stacked DC-DC power converters are used to step down high input voltage, then voltage conversion is achieved, but inductor equivalent series resistance (ESR) rises substantially and efficiency decreases
Solution Approach 1:
The power converter is divided into multiple phases (first phase and second phase) with separate inductors and switches. Each phase handles a portion of the power conversion independently, allowing the inductors to operate at lower currents and reducing their equivalent series resistance losses.
Solution Approach 2:
The converter operates in alternating phases where the first phase is active during a first time interval and the second phase is active during a second time interval. This periodic switching distributes the power conversion load over time, reducing the instantaneous current through each inductor and thereby reducing ESR losses.
2Productivity
If series stacked DC-DC power converters operate at high switching frequencies, then power density increases, but electromagnetic interference (EMI) spectrum becomes undesirable
Solution Approach 1:
The converter uses periodic alternating phases with controlled switching intervals. By carefully designing the switching frequencies and duty cycles of each phase, the EMI spectrum can be shaped to avoid problematic frequency ranges while maintaining high power density.
Solution Approach 2:
The patent converts the potential EMI harm into a benefit by using the alternating phase structure to cancel out certain EMI components. The complementary switching of the two phases creates current waveforms that can cancel electromagnetic interference at critical frequencies, thereby improving the EMI spectrum while maintaining high power density.
3Power
If dedicated power converter circuits are used for each integrated circuit, then voltage regulation is achieved, but the converter consumes more space than the integrated circuit it powers
Solution Approach 1:
The multi-phase power converter is designed to serve multiple integrated circuits simultaneously. By providing multiple output terminals and configuring the phases to deliver regulated voltage to different loads, a single converter circuit can replace multiple dedicated converters, thereby reducing the total space required.
Solution Approach 2:
The patent combines multiple power conversion functions into a single integrated converter circuit. The first and second phases work together to provide regulated voltage to multiple integrated circuits, merging what would traditionally require separate converter circuits into one compact unit.
4Loss of energy
If phase multiplexing is implemented to reduce inductor losses, then efficiency improves, but control circuit complexity increases
Solution Approach 1:
The control circuit uses feedback signals from the output voltage and current to dynamically adjust the switching timing and duty cycles of the phases. This feedback mechanism allows the control circuit to optimize the phase switching for maximum efficiency while managing the complexity through systematic control algorithms.
Solution Approach 2:
The control circuit dynamically adjusts the operating parameters of each phase based on real-time load conditions. By making the switching frequencies and duty cycles variable rather than fixed, the control circuit can optimize efficiency across different operating points while managing complexity through adaptive control strategies.
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
The solution achieves reduced output voltage ripple, improved EMI spectrum, and decreased inductor losses at low nominal loads, enhancing efficiency and reducing electromagnetic interference.
Implementation Method 1
sense a voltage at the junction; compare the sensed voltage to a first threshold voltage and in response to the sensed voltage at a voltage lower than the first threshold voltage, the control circuit operates the first buck converter and disables the second buck converter; and compare the sensed voltage to a second threshold voltage and in response to the sensed voltage at a voltage higher than the second threshold voltage, the control circuit operates the second buck converter and disables the first buck converter
Implementation Method 2
a first buck converter having a first switch having a first gate terminal, a first drain terminal and a first source terminal, and a second switch having a second gate terminal, a second drain terminal and a second source terminal
Implementation Method 3
the first and second buck converters are arranged to generate an output voltage at the output terminal that is lower that an input voltage at the input terminal
Implementation Method 4
A phase multiplexed series stacked DC-DC power converter circuit that alternately turns on and off top-phase and bottom-phase buck converters, using a control circuit to regulate voltage at a junction node within the converter, thereby reducing output voltage ripple and EMI, and moving fluctuations to an internal node
Data Source
AI summary
A power converter circuit. In one aspect, the power converter circuit includes a first buck converter coupled in series to a second buck converter at a junction, and a control circuit coupled to each of the first and second buck converters. In another aspect, the control circuit is arranged to sense a voltage at the junction, compare the sensed voltage to a first threshold voltage and in response to the sensed voltage being at a voltage lower than the first threshold voltage, the control circuit operates the first buck converter and disables the second buck converter. In yet another aspect, the control circuit is arranged to compare the sensed voltage to a second threshold voltage and in response to the sensed voltage being at a voltage higher than the second threshold voltage, the control circuit operates the second buck converter and disables the first buck converter.