Flying-Capacitor Booster Stage for Instant PA Supply Doubling
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Solution Overview
Problem
Existing booster stage circuits for power amplifiers face limitations in output voltage range due to supply voltage constraints, particularly in battery-operated devices with high crest-factor audio amplifiers. Current solutions, such as flying capacitors and switching power stages, suffer from inefficiencies, charging delays, and increased power dissipation.
Innovation Solution
The proposed booster stage circuit utilizes a flying capacitor that is automatically recharged with high efficiency through an inductor, allowing for instantaneous doubling of the supply voltage without charging delays. This circuit switches between normal and boosted supply modes rapidly, using a small capacitance value while minimizing discharge, and avoids power dissipation associated with diodes in prior art.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a flying capacitor is used to double the supply voltage, then the output voltage range is extended, but the capacitor discharges during use and can only achieve maximum doubling of the supply with power dissipation during recharging
Solution Approach 1:
The patent replaces the diode-based recharging mechanism with an inductor-based switching circuit. The inductor stores energy in its magnetic field during the charging phase and releases it during the boosting phase, eliminating the resistive power dissipation inherent in diode-based circuits. This substitution of the recharging mechanism fundamentally resolves the energy loss problem while maintaining the voltage doubling capability.
Solution Approach 2:
The patent implements periodic switching between the flying capacitor and the inductor-based boosting circuit. The controller alternates between charging the capacitor through the inductor and using the capacitor for voltage doubling, creating a rhythmic charge-discharge-boost cycle. This periodic action allows the system to maintain high efficiency by continuously replenishing the capacitor through the low-loss inductor path rather than dissipating energy through diodes.
2Strength
If a switching power stage with inductor and capacitor is used to generate local supply, then the supply voltage can be boosted, but it takes time to charge the local supply above the external supply causing delay
Solution Approach 1:
The patent pre-charges the flying capacitor to the external supply voltage through the inductor before the boosting operation begins. This preliminary charging action ensures that when the boost phase is triggered, the capacitor is already ready to immediately double the supply voltage without any delay. The controller anticipates the need for boosting and prepares the capacitor in advance, eliminating the charging delay that plagues conventional switching boosters.
Solution Approach 2:
The flying capacitor serves dual purposes: it acts as both the energy storage element for voltage doubling and as the local supply reservoir. The inductor-based circuit automatically manages the charging and discharging of the capacitor without requiring a separate, time-consuming charging phase. The system essentially serves itself by using the same capacitor that provides the boost voltage as the element being charged, eliminating the need for a separate charging delay period.
3Strength
If a switching booster circuit is used, then the supply voltage can be boosted, but the supply current always runs through the primary inductor causing additional losses due to parasitic resistance
Solution Approach 1:
The patent segments the current path by creating two distinct operational modes: a normal supply mode where current flows directly from the external supply without passing through the inductor, and a boosting mode where the pre-charged capacitor is connected in series with the supply. By segmenting the current flow paths and only engaging the inductor when absolutely necessary for charging the capacitor, the system minimizes the time current spends flowing through the inductor's parasitic resistance, thereby reducing energy losses.
Solution Approach 2:
The patent implements periodic switching where the inductor is only engaged during brief charging intervals, while the majority of the time the system operates in a low-loss mode where current bypasses the inductor entirely. The controller switches between the inductor-based charging phase and the capacitor-based boosting phase in a periodic manner, ensuring that the inductor carries current only when necessary to replenish the capacitor, thus minimizing cumulative energy losses from parasitic resistance.
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 solution provides efficient and instantaneous voltage boosting, maintaining high power efficiency by recharging the capacitor through an inductor rather than a diode, and allowing for flexible energy transfer between the inductor and capacitor.
Implementation Method 1
The capacitor is automatically recharged with high efficiency after each lifting cycle through an inductor
Implementation Method 2
a flying capacitor that can momentarily double the supply
Data Source
AI summary
A booster stage circuit for a power amplifier, comprising an electrical connector, configured to receive an external power supply, an output terminal, configured to provide an output voltage to the power amplifier, an inductor having a first side and a second side, a capacitor, coupled between the output terminal and the first side of the inductor, and a first switch and a second switch, series coupled between the output terminal and the first side of the inductor. Each of the first switch and the second switch is adapted to operate at a switching frequency of >20 kHz. In a boost mode the first switch is in a closed status and the second switch is in an open status, and in a base mode the first switch is in the open status and the second switch is in the closed status.