Class H Line Driver Supply Ramping for Low-Distortion Boosting
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Solution Overview
Problem
Conventional class H amplifiers used in xDSL line drivers face inefficiencies and signal distortion due to rapid power supply voltage changes, which degrade performance and increase power consumption, while also requiring high quiescent power and multiple power supplies, leading to increased costs and complexity.
Innovation Solution
The proposed solution involves a class H amplifier circuitry with integrator amplifiers and pump capacitors that control the ramping of supply voltages to minimize power supply coupling into the output, using asymmetric ramping rates and a recharging mechanism to optimize efficiency and reduce power consumption, allowing for improved signal fidelity and lower costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If pass transistor is driven with a fast square wave to quickly raise and lower supply voltage, then the speed of operation is improved, but the CMRR and PSRR deteriorate causing output signal distortion
Solution Approach 1:
The patent applies dynamics by transitioning from a static square wave drive to a dynamically controlled ramping waveform. The supply voltage transitions are made gradual and controlled through integrator amplifiers that generate ramping waveforms, allowing the system to adapt the voltage change rate to maintain signal fidelity while still achieving fast operation when needed.
Solution Approach 2:
The patent changes the parameter of voltage transition from abrupt (square wave) to gradual (ramping). By modifying the waveform shape and controlling the ramping rate through integrator time constants, the system achieves fast operation without the harmful effects of rapid voltage changes on CMRR and PSRR.
2Productivity
If current source magnitude is increased to quickly recharge pump capacitor, then the recharging speed is improved, but the power consumption increases
Solution Approach 1:
The patent applies dynamics by using a controlled current source that adjusts its magnitude based on operational needs. The current source provides high current only when rapid recharging is required, and reduces current during normal operation, achieving fast recharging capability without continuous high power consumption.
Solution Approach 2:
The patent uses periodic action by activating the high-current recharging mode only when pump capacitor recharging is needed, rather than maintaining continuous high current. This allows the system to achieve fast recharging when required while minimizing average power consumption through intermittent high-current operation.
3Adaptability or versatility
If multiple power supplies are used to provide high and low magnitude supply voltages, then the output voltage swing capability is improved, but the device complexity and cost increase
Solution Approach 1:
The patent merges multiple power supply functions into a single power supply combined with a pump capacitor. Instead of requiring separate high and low magnitude power supplies, the system uses one power supply and a pump capacitor to generate the necessary voltage levels, reducing component count and system complexity while maintaining output voltage swing capability.
Solution Approach 2:
The pump capacitor serves multiple functions: it acts as an energy storage element, a voltage boosting device, and a timing element. This multi-functionality replaces the need for multiple dedicated power supplies, reducing device complexity while maintaining the ability to provide both high and low magnitude supply voltages as needed.
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 approach enhances the efficiency and speed of operation of xDSL line drivers, reduces power supply coupling, and maintains low quiescent power consumption, resulting in improved signal quality and reduced operational costs.
Implementation Method 1
Terminal 2 also is connected to one plate of a capacitor C, which is sometimes referred to as a 'pump capacitor' because it is used to pump up the supply voltage
Implementation Method 2
an integrator amplifier producing an output signal that controls a pass transistor to discharge the pump capacitor into a driver amplifier supply terminal
Data Source
AI summary
Amplifier circuitry (10) includes a driver amplifier (11) and an integrator amplifier (AH) producing an output signal (VAH) that controls a pass transistor (Q2) coupled to a pump capacitor (CH). Input circuitry (16) controls the direction of ramping of the output signal during a first interval to boost a supply voltage (V12) of the driver amplifier via the pump capacitor, and also controls the direction of ramping to recharge the pump capacitor following a second interval. In one embodiment, pump capacitor recharging circuitry (Q75,R76,ICHH) completes the recharging of the pump capacitor following the second interval after it has been partially recharged by the integrator amplifier.