Open-Loop Class-H Line Driver Control for DSL Power Tracking
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Solution Overview
Problem
Conventional class-A and class-AB amplifiers in DSL equipment are inefficient due to high peak-to-average power ratio (PAR) applications, leading to significant energy wastage and distortion, while closed-loop class-H amplifiers require complex feedback systems and additional circuitry, increasing routing and circuit outlay.
Innovation Solution
An open-loop control system with a mask generator and detector is used to modulate the power supply of a class-H amplifier, generating compensation pulses to offset discontinuities in the mask input, allowing the supply voltage to track the signal envelope efficiently without feedback, thereby reducing power consumption 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 signal can be amplified and driven onto the line, but significant energy is wasted because the amplifiers remain fully powered even when not transmitting at peak power
Solution Approach 1:
The patent applies dynamics by making the amplifier supply voltage adjustable and dynamic rather than fixed. The class-H amplifier configuration allows the supply voltage to vary dynamically according to the signal envelope, enabling the amplifier to operate efficiently at lower voltages during low-power periods while maintaining full power capability when needed.
Solution Approach 2:
The patent changes the operating parameters of the amplifier by varying the supply voltage level based on the signal characteristics. The mask generator creates a control signal that modulates the supply voltage to match the envelope of the input signal, thereby changing the amplifier's operating point dynamically to reduce power consumption.
2Loss of energy
If the amplifier supply voltage is ramped up and down quickly to follow signal peaks, then power efficiency is improved, but the signal may be distorted due to finite edge response time
Solution Approach 1:
The patent applies preliminary action by ramping up the amplifier supply voltage before the actual signal peak occurs. The mask generator anticipates the signal envelope and adjusts the supply voltage in advance, allowing the amplifier to be ready to handle the peak without distortion while still maintaining efficiency during lower power periods.
3Measurement precision
If a closed-loop controller is used to control the DC-DC converter output voltage, then the supply voltage can track the signal envelope accurately, but additional feedback lines and circuitry are required, increasing routing and circuit outlay
Solution Approach 1:
The patent extracts and eliminates the feedback component from the control system. Instead of using a closed-loop controller that requires feedback lines and additional circuitry, the invention uses an open-loop mask generator that generates the control signal directly from the input signal envelope, removing the need for feedback paths while maintaining voltage tracking accuracy.
Solution Approach 2:
The mask generator operates autonomously by deriving its control signal directly from the input signal characteristics without requiring external feedback. The system serves itself by using the input signal envelope to automatically modulate the amplifier supply voltage, eliminating the need for separate feedback control circuitry.
4Speed
If the mask input to the PWM has discontinuities, then the DC-DC converter responds quickly to changes, but transient oscillations are generated in the supply voltage
Solution Approach 1:
The patent applies preliminary anti-action by generating compensation pulses that counteract the transient oscillations caused by mask discontinuities. The detector identifies these discontinuities and generates opposing voltage adjustments that cancel out the harmful oscillations, allowing the system to respond quickly to signal changes while maintaining supply voltage stability.
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 up to 50% relative to conventional class-AB amplifiers, minimizes distortion, and simplifies the circuitry by eliminating the need for complex feedback systems, ensuring efficient and reliable signal amplification in high PAR applications like DSL.
Implementation Method 1
The duty cycle of the PWM determines the level of supply voltage applied to the class-H amplifier
Implementation Method 2
In the continuous mode, a current always flows through a coil inductor of the converter during the entire switching cycle
Data Source
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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.