RF Supply Modulator Using Sensing Transistor Duty Control
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Solution Overview
Problem
Mobile wireless communications devices face challenges in designing communications circuitry for increased operational and performance stability within limited space, particularly in efficiently managing the power supply for RF transmitters.
Innovation Solution
A mobile wireless communications device incorporates a supply modulator with a linear amplifier and a switching amplifier, including a current sensor and hysteretic comparator, which dynamically adjusts the duty ratio to maintain zero output current from the linear amplifier, enhancing power efficiency by eliminating the need for sensing resistors and using current conveyors for improved bandwidth and cost-effectiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If sensing resistors are used to sense current from the linear amplifier, then current sensing is achieved, but power consumption increases and device area increases
Solution Approach 1:
The patent extracts the current sensing function from the traditional resistor-based approach and implements it using the inherent properties of the sensing transistor itself. The sensing transistor's drain current directly reflects the linear amplifier's output current without requiring external sensing resistors, thereby eliminating the power consumption and area overhead of separate sensing components.
Solution Approach 2:
The sensing transistor serves multiple functions: it acts as both the switching element in the amplifier stage and the current sensor simultaneously. This multi-functionality eliminates the need for dedicated sensing resistors, reducing both power consumption and device area while maintaining current sensing capability.
2Measurement precision
If sensing resistors are used to sense current from the linear amplifier, then current sensing is achieved, but device area increases
Solution Approach 1:
The patent extracts the current sensing function from the traditional resistor-based approach and implements it using the inherent properties of the sensing transistor itself. The sensing transistor's drain current directly reflects the linear amplifier's output current without requiring external sensing resistors, thereby eliminating the power consumption and area overhead of separate sensing components.
Solution Approach 2:
The sensing transistor serves multiple functions: it acts as both the switching element in the amplifier stage and the current sensor simultaneously. This multi-functionality eliminates the need for dedicated sensing resistors, reducing both power consumption and device area while maintaining current sensing capability.
3Use of energy by moving object
If duty ratio is dynamically adjusted to maintain zero output current, then power efficiency is improved, but control complexity increases
Solution Approach 1:
The patent implements a feedback mechanism where the hysteretic comparator continuously monitors the output current through the sensing transistor and dynamically adjusts the duty ratio of the switching amplifier accordingly. This closed-loop feedback control automatically maintains zero output current from the linear amplifier, improving power efficiency while the hysteresis provides natural stability and noise immunity.
Solution Approach 2:
The system dynamically changes the duty ratio parameter of the switching amplifier based on real-time current conditions. By modulating this single parameter through feedback control, the system achieves optimal power efficiency without requiring complex multi-parameter adjustments or additional control circuitry.
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 configuration achieves maximum power efficiency for the RF power amplifier by dynamically adjusting the duty ratio and using current conveyors, reducing power consumption and improving operational stability within the limited space constraints of mobile devices.
Implementation Method 1
at least one sensing transistor configured to sense current output from the linear amplifier and generate a drive voltage
Implementation Method 2
a hysteretic comparator coupled to the at least one sensing transistor and configured to be driven by the drive voltage
Data Source
AI summary
A mobile wireless communications device may include a portable housing, and a supply modulator carried by the portable housing. The supply modulator may include an output node, a linear amplifier coupled to the output node, and a switching amplifier also coupled to the output node. The switching amplifier may include at least one sensing transistor configured to sense current output from the linear amplifier and generate a drive voltage, and a hysteretic comparator coupled to the at least one sensing transistor and configured to be driven by the drive voltage. The mobile wireless communications device may also include a radio frequency (RF) power amplifier coupled to the output node of the supply modulator, and a wireless transceiver carried by the portable housing and coupled to the RF power amplifier.