Tri-State Class-D Amplifier Impedance Adjustment
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Solution Overview
Problem
Wireless transmission devices face challenges in reducing electric power consumption while maintaining high output power efficiency, particularly in Bluetooth standard applications, due to parasitic capacitance and impedance adjustment limitations in class-D amplifier configurations.
Innovation Solution
A wireless transmission device design incorporating a plurality of unit amplifiers and capacitive elements, where each unit amplifier is a tri-state-type class-D amplifier with sub-output terminals that can be set to low, high, or high impedance states, allowing for improved impedance adjustment and reduced parasitic capacitance by coupling output capacitors in series, thereby enhancing power efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the number of class-D amplifier units in OFF state is increased to decrease transmission electric power, then transmission electric power is reduced, but parasitic capacitance loss increases and electric power efficiency deteriorates
Solution Approach 1:
The patent extracts and removes the parasitic capacitance of OFF-state amplifier units from the output node by using switches to disconnect them. This isolation prevents the parasitic capacitance from contributing to energy loss while still allowing the units to be part of the amplifier system, thus reducing parasitic capacitance loss when transmission electric power is decreased.
Solution Approach 2:
The patent introduces switches as intermediary elements between the amplifier units and the output node. These switches act as mediators that can connect or disconnect the amplifier units from the output, enabling dynamic control of which units contribute to the output signal and which are isolated to minimize parasitic capacitance effects.
2Loss of energy
If impedance (ZDMN) is increased to efficiently output small transmission electric power, then small transmission electric power efficiency is improved, but large transmission electric power output capability is reduced
Solution Approach 1:
The patent implements dynamic impedance adjustment by using switches to selectively connect or disconnect capacitor elements based on the required transmission electric power level. The impedance is not fixed but changes dynamically with the operating conditions, allowing optimal impedance matching for both small and large power output scenarios.
Solution Approach 2:
The patent changes the impedance parameter (ZDMN) by adjusting the capacitive configuration through switch control. By changing which capacitors are connected in parallel or series, the overall impedance value is adjusted to match the optimal value for the current power output requirement, whether small or large.
3Power
If only switch capacitance array (SCA) is used for impedance adjustment in differential configuration, then large transmission electric power can be output, but impedance adjustment range is limited and electric power efficiency at small output deteriorates
Solution Approach 1:
The patent creates a composite impedance adjustment mechanism by combining switch capacitance arrays with additional capacitor elements and switch networks. This composite structure provides a broader impedance adjustment range compared to using only SCA, while maintaining the capability to output large transmission electric power through the differential configuration.
Solution Approach 2:
The patent segments the impedance adjustment function into multiple independent capacitor elements and switch groups. This segmentation allows for finer-grained control of the total capacitance value, expanding the adjustable impedance range while maintaining compatibility with the differential amplifier configuration for high power output.
Data Source
AI summary
A wireless transmission device includes an input terminal, control terminals, an amplifying circuit, a matching circuit, and an output terminal coupled to the output of the matching circuit. The amplifying circuit includes unit amplifiers and capacitive elements. Each unit amplifier includes a sub-input terminal, a sub-control terminal, and a sub-output terminal. The sub-input terminal is coupled to the input terminal, the sub-control terminal is coupled to the corresponding control terminal in the control terminals, and the sub-output terminal is coupled to the input of the matching circuit through the corresponding capacitive element in the capacitive elements in series. Each unit amplifier includes a tri-state-type class-D amplifier. The sub-output terminal of each unit amplifier is set to a low level state, a high level state, or a high impedance state based on a control signal supplied to the sub-control terminal or an input signal supplied to the sub-input terminal.