PWM Frequency Divider for Multi-Phase DC-DC Converter
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Solution Overview
Problem
Current DC-DC converters face limitations in reducing physical size due to the need for multiple output inductors and filter capacitors, with indirectly coupled inductors offering only partial reductions in size while being constrained by efficiency and current ripple issues.
Innovation Solution
A method and apparatus for dividing a single phase PWM signal into multiple phases using a PWM frequency divider, which provides an output pulse train to one phase while holding others at a tri-state voltage, allowing for a directly coupled inductor configuration that reduces inductance and current ripple by alternating switch activations without simultaneous switch engagement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If indirectly coupled inductors are used to reduce physical footprint, then the size of DC-DC converters is reduced, but efficiency and current ripple performance deteriorate
Solution Approach 1:
The patent divides a single phase PWM signal into multiple phases (e.g., two phases) using a PWM frequency divider. This segmentation allows the use of directly coupled inductors with reduced size while maintaining efficiency, as each phase operates with its own switch and the inductors are magnetically coupled but electrically isolated during switching transitions.
Solution Approach 2:
The patent employs periodic switching of multiple phases where switches are activated in alternating periods. During each period, one phase is active while the other is inactive, and vice versa. This periodic action allows directly coupled inductors to be used without suffering from the efficiency and current ripple issues of continuously coupled inductors in single-phase designs.
2Area of stationary object
If indirectly coupled inductors are used to reduce physical footprint, then the size of DC-DC converters is reduced, but current ripple increases
Solution Approach 1:
By segmenting the single-phase operation into multiple phases with separate inductors that are directly coupled, the patent reduces current ripple while maintaining compact size. Each phase's inductor handles a portion of the total current, and the direct coupling allows for better current sharing and reduced ripple compared to indirectly coupled designs.
Solution Approach 2:
The patent changes the operating parameters by using multiple phases with alternating switch activation. This parameter change allows the use of directly coupled inductors with lower inductance values, which reduces physical footprint while the multi-phase operation smooths out current ripple through the alternating conduction patterns.
3Loss of energy
If multiple phases are used with direct coupling, then inductance and current ripple are reduced, but simultaneous switch activation occurs
Solution Approach 1:
The patent uses periodic action with phase interleaving where multiple phases operate in alternating periods. The PWM frequency divider ensures that when one phase is active, the other phases are inactive, preventing simultaneous switch activation. This periodic interleaving maintains the benefits of direct coupling while avoiding the harmful effect of simultaneous switching.
Solution Approach 2:
The patent introduces a PWM frequency divider as an intermediary device that takes a single-phase PWM signal and distributes it to multiple phases with appropriate timing offsets. This intermediary ensures proper phase sequencing and prevents simultaneous switch activation while enabling the use of directly coupled inductors for reduced inductance and current ripple.
Data Source
AI summary
Dividing a single phase PWM signal into a plurality of phases includes: receiving, from a phase controller by a PWM frequency divider, an input pulse train comprising a period; and dividing, by the PWM frequency divider, the input pulse train amongst a plurality of output phases of the PWM frequency divider, including, at the onset of each period of the input pulse train: providing, on a next output phase of the PWM frequency divider, an output pulse train; and holding all other output phases at a tri-state voltage level.