Switching Amplifier Amplitude Control for Low-Interference LF Transmission
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Solution Overview
Problem
Existing switching amplifier circuits face challenges in controlling load current over a wide range, leading to complex designs, increased component count, and higher costs, particularly in low-frequency transmission systems like automotive applications, where minimizing signal power is crucial to avoid interference and extend communication distance.
Innovation Solution
A switching amplifier circuit with an output-amplitude control mechanism that limits the maximum achievable gate and source voltages of opposing-phase electronic switches, ensuring they operate within the supply voltage limits, thereby minimizing signal power without compromising signal integrity, using a configuration of FETs and voltage clamping circuitry to control the ON-phase duration of the switches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If regulators and diodes are used to clamp gate and source voltages for amplitude control, then load current control is achieved, but device complexity and component count increase
Solution Approach 1:
The patent extracts the amplitude control function from complex regulator and diode networks and implements it through a simplified mechanism using the body effect in FETs. By removing unnecessary clamping components and using the intrinsic body effect of the FET structure, the circuit achieves load current control without increasing device complexity
Solution Approach 2:
The patent makes the FET body effect serve multiple functions: it provides both the switching function and the amplitude control function simultaneously. The body terminal is used to control the threshold voltage, which in turn controls the output amplitude, eliminating the need for separate control circuits and reducing overall system complexity
2Adaptability or versatility
If regulators and diodes are used for amplitude control, then load current control is achieved, but component count and costs increase
Solution Approach 1:
The patent removes regulators and diodes from the amplitude control path and replaces them with the FET body effect mechanism. This extraction of unnecessary components directly reduces component count and associated costs while maintaining the load current control capability
Solution Approach 2:
The FET's body effect is a self-inherent property that requires no external components to function. By utilizing this self-service mechanism, the circuit achieves amplitude control using only the FET structure itself, eliminating the need for additional regulators, diodes, and associated components
3Length of moving object
If gate voltage is increased to extend communication distance, then signal power increases, but interference increases in automotive environments
Solution Approach 1:
The patent changes the control parameter from gate voltage to body voltage. By controlling the body terminal voltage, the threshold voltage of the FET is modulated, which provides amplitude control without requiring high gate voltages. This parameter change enables communication distance extension through efficient power utilization while avoiding the interference problems associated with high voltage operation
Data Source
Figure 1A~1B
Figure 2A
Figure 2B
AI summary
An amplifier circuit including opposing-phase electronic switches, and an output drive circuit that provides an output drive signal in response to output signals from the opposing-phase electronic switches. Each of the opposing-phase electronic are configured and arranged to rapidly switch back and forth in response to an amplifier input signal and based on a power source defined to provide a supply voltage to the switching amplifier circuit. Further, an output-amplitude control circuit is used to limit a maximum-achievable voltage that is applied (e.g., gate or source voltage) to at least one of the opposing-phase electronic switches, with each such applied voltage being less than the supply voltage provided by the power source. Consistent therewith, more specific aspects concern an arrangement or circuit-based system of wireless communication in an automobile, wherein an automotive battery is the power source.