Multiphase Charging Circuit Ripple Cancellation via Phase Shifting
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Solution Overview
Problem
In multiphase charging circuits, the high inductor height becomes a bottleneck for the design of compact and thin battery-powered devices, as it affects system stability and transient response due to significant feedback signal ripple, especially in two-phase charging circuits where the effective magnitude of the ac ripple current of the sum current is nearly zero, preventing improvement in system stability through conventional methods.
Innovation Solution
A multiphase charging circuit design that includes a master phase and slave phases with feedback control circuits, logic grouping, and pulse generating circuits to manage switching phases with phase differences, effectively controlling switches to minimize ripple and enhance stability by using a system voltage feedback control circuit and other feedback control signals to regulate the charging process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional two-phase charging circuits are used, then the system provides charging capability, but the ac ripple current magnitude is nearly zero which prevents improvement in system stability
Solution Approach 1:
The charging circuit is divided into multiple phases (first charging phase, second charging phase, third charging phase) with distinct switching patterns. Each phase has its own inductor and switching elements, allowing independent control of current ripple in each phase. The segmentation enables the system to achieve lower overall ripple while maintaining stability.
Solution Approach 2:
Different phases are designed with different local characteristics - specifically, different switching frequencies and duty cycles. The first charging phase operates with a higher switching frequency than the second and third phases, creating localized quality differences that result in complementary ripple patterns. This local differentiation allows the ripples to cancel each other out when summed, achieving lower overall ripple and improved stability.
2Volume of moving object
If the number of charging phases is increased to reduce inductor height, then compact device design is enabled, but feedback signal ripple increases affecting system stability
Solution Approach 1:
The circuit employs periodic switching action with different periods for different phases. The first charging phase switches at a higher frequency (shorter period) while the second and third phases switch at lower frequencies (longer periods). This periodic action with varying periods creates ripple patterns that are out of phase, allowing them to cancel each other out and reduce overall feedback signal ripple.
Solution Approach 2:
The charging phases are designed with asymmetric characteristics - specifically, the first charging phase has a different switching frequency and duty cycle pattern compared to the second and third phases. This asymmetry ensures that the ripple currents from different phases do not add constructively but instead partially cancel, reducing overall ripple while maintaining the benefits of multiple phases for compact inductor design.
3Shape
If multiphase charging circuit is used to reduce inductor height for compact design, then device thickness is reduced, but transient response deteriorates due to significant feedback signal ripple
Solution Approach 1:
The circuit incorporates feedback control mechanisms that monitor the output voltage and current from each charging phase. The feedback signals are used to adjust the switching duty cycles and frequencies dynamically, compensating for transient disturbances. This feedback control reduces the impact of feedback signal ripple on transient response, allowing the system to maintain fast response while benefiting from the compact multiphase architecture.
Data Source
AI summary
A multiphase charging circuit includes a first phase having a first switch and a second phase having a second switch to provide a system voltage for a system load, a control method of the multiphase charging circuit includes: generating a plurality of feedback control signals with generating each of feedback control signal based on a corresponding feedback signal, a ramp signal, a corresponding reference signal and a current flowing through the first phase; selecting one of the plurality of feedback control signals as a first enable signal; generating a first control signal of the first switch based on the first enable signal and a first time period control signal; generating a second enable signal by shifting a pre-determined phase difference to the first control signal; and generating a second control signal of the second switch based on the second enable signal and a second time period control signal.