Digitally Controlled Driver Amplifier for Crossover Distortion
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Solution Overview
Problem
Conventional AB class amplifiers face challenges in balancing efficiency and crossover distortion due to complex circuitry and inappropriate bias current control, leading to shoot-through currents and inefficiencies in sourcing and sinking operations.
Innovation Solution
An operational amplifier with a digital control circuit that automatically switches between PMOS and NMOS drivers based on load current polarity, utilizing a differential input signal, bias circuits, and enabling switches to manage bias current efficiently, thereby simplifying circuitry and preventing shoot-through.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a conventional AB class amplifier uses a small bias current to improve efficiency, then power consumption is reduced, but crossover distortion increases
Solution Approach 1:
The patent applies dynamic bias current control where the bias current automatically adjusts between small and large values based on operating conditions. The control circuit monitors driver currents and dynamically switches bias current magnitude to eliminate crossover distortion during transitions while maintaining low power consumption during steady-state operation.
Solution Approach 2:
The patent changes the bias current parameter from a fixed small value to a variable parameter that switches between small and large values. This parameter change is controlled by monitoring the currents in the PMOS and NMOS drivers and adjusting the bias current accordingly to prevent crossover distortion while optimizing power efficiency.
2Reliability
If both PMOS and NMOS drivers carry large currents to reduce crossover distortion, then crossover distortion is reduced, but shoot-through current from the power supply increases
Solution Approach 1:
The patent implements a feedback control mechanism where the control circuit continuously monitors the currents carried by the PMOS and NMOS drivers. Based on this feedback information, the control circuit adjusts the bias current to ensure that both drivers never carry large currents simultaneously, thereby preventing shoot-through current while maintaining low crossover distortion.
3Object-generated harmful factors
If accurate control of bias current is implemented to prevent shoot-through current, then shoot-through current is reduced, but circuit complexity increases
Solution Approach 1:
The patent employs a self-service control mechanism where the control circuit automatically monitors driver currents and adjusts the bias current without external intervention. The system uses the existing driver current signals to generate the control voltage that regulates the bias current, creating a self-regulating system that prevents shoot-through current while adding minimal circuit complexity.
Data Source
AI summary
A driving amplifier circuit includes: a first driver for souring a load current to a load; a second driver for sinking the load current from the load; a first operational amplifier (op-amp) coupled to a differential input signal for driving the first driver; a second operational amplifier coupled to the differential input signal for driving the second driver; a first bias circuit for biasing the first driver; a second bias circuit for biasing the second driver; an enabling circuit, coupled to the first bias circuit and the second bias circuit, for enabling either the first bias circuit or the second bias circuit according to a control signal; and a digital control circuit, coupled to the enabling circuit, for monitoring currents of the first driver and the second driver to generate the control signal.