Open-Loop Line Driver Supply Modulation for Low-Distortion DSL
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional class-A and class-AB amplifiers are inefficient for high peak-to-average power ratio (PAR) applications like DSL due to constant power consumption, and closed-loop control systems for class-H amplifiers increase circuit complexity and introduce disturbance frequencies.
Innovation Solution
An open-loop control system with a mask generator and detector is used to generate and compensate for discontinuities in the mask input of a pulse width modulator, ensuring efficient power supply modulation without feedback, thereby reducing energy waste and distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If class-A or class-AB amplifiers are used in DSL equipment, then the amplifier can provide stable signal amplification, but the power consumption is excessively high because the amplifier remains fully powered even when not transmitting at peak power
Solution Approach 1:
The patent applies dynamics by making the supply voltage of the class-H amplifier dynamic rather than static. The supply voltage is adjusted in real-time according to the signal envelope, allowing the amplifier to operate at lower voltages during low-power periods and at higher voltages during peak power periods, thus reducing overall power consumption while maintaining signal amplification stability when needed
Solution Approach 2:
The patent changes the operating parameters of the amplifier by varying the supply voltage level according to the signal characteristics. The DC-DC converter dynamically adjusts the supply voltage parameter based on the envelope of the input signal, enabling the amplifier to adapt its power consumption to the actual signal requirements rather than operating at constant high power
2Manufacturing precision
If a closed-loop controller is used to control the DC-DC converter output voltage, then the output voltage can follow the signal profile accurately, but the circuit complexity increases and disturbance frequencies are introduced
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing the relationship between signal envelope levels and required supply voltage levels in a lookup table. The mask generator uses this pre-computed data to directly generate the control signal for the DC-DC converter without requiring real-time feedback or complex control algorithms, thus achieving accurate voltage tracking while avoiding closed-loop complexity
Solution Approach 2:
The patent extracts the feedback mechanism from the control system by using open-loop control with pre-computed lookup tables. Instead of continuously measuring the output voltage and adjusting based on error signals (closed-loop), the system uses pre-determined voltage profiles stored in lookup tables, eliminating the need for complex feedback circuits while maintaining voltage tracking accuracy
3Speed
If the amplifier supply voltage is ramped up quickly to match signal peaks, then the amplifier can respond to peak power demands, but the supply voltage cannot follow the signal profile at every desired speed causing signal distortion
Solution Approach 1:
The patent applies preliminary action by pre-computing the optimal supply voltage profile corresponding to the signal envelope and storing it in a lookup table. The mask generator retrieves pre-calculated voltage values that account for the finite ramping speed of the DC-DC converter, ensuring the supply voltage follows the signal profile at achievable speeds without causing distortion
Solution Approach 2:
The patent applies beforehand cushioning by incorporating compensation factors in the lookup table that anticipate the finite response time of the DC-DC converter. The pre-computed mask values include cushioning adjustments that prevent the supply voltage from attempting to change faster than the converter can physically respond, thereby avoiding signal distortion while maintaining as fast a response as possible
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 open-loop control system effectively reduces power consumption by 50% to 70% relative to conventional class-AB amplifiers while minimizing signal distortion and disturbance frequencies, ensuring reliable and efficient operation of class-H amplifiers in high PAR applications.
Implementation Method 1
The duty cycle of the PWM determines the level of supply voltage applied to the class-H amplifier
Implementation Method 2
a current always flows through a coil inductor of the converter during the entire switching cycle
Data Source
AI summary
According to an embodiment, a circuit includes an amplifier and an open-loop control system. The amplifier has an output stage for amplifying a signal, a power supply for driving a supply voltage of the output stage to different voltage levels responsive to being modulated and a pulse width modulator for modulating the power supply responsive to a mask input. The open-loop control system includes a mask generator and a detector. The mask generator is configured to generate the mask input as a function of the envelope of the signal. The detector is configured to detect discontinuities in the mask input and compensate for the discontinuities.