Doherty Amplifier Drain Voltage Control Across Output Power Levels
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Solution Overview
Problem
Conventional power amplification devices with Doherty amplifiers suffer from significantly reduced power efficiency at lower input signal levels, particularly in mobile communication devices that operate across a wide output power range.
Innovation Solution
A power amplification device that includes a DC power supply, a Doherty amplifier with a voltage control circuit and a voltage converter circuit, which adjusts the drain voltage based on output power levels, applying a lower voltage when output power is equal to or lower than a given value and a higher voltage when it exceeds this value, optimizing efficiency across varying signal conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a Doherty amplifier with carrier amplifier and peak amplifier is used, then saturated electric power is ensured at larger signal levels, but power efficiency deteriorates at smaller signal levels
Solution Approach 1:
The patent applies dynamic voltage scaling to the drain terminals of the carrier amplifier and peak amplifier. A voltage control circuit dynamically adjusts the drain voltage based on the output power level, switching between a first drain voltage (higher) and a second drain voltage (lower). This dynamic adjustment allows the amplifier to maintain high power efficiency at smaller signal levels by operating at lower voltage, while still ensuring adequate saturated electric power at larger signal levels.
Solution Approach 2:
The patent changes the operating voltage parameter of the amplifier based on the signal level. By controlling the drain voltage to be lower at smaller signal levels and higher at larger signal levels, the system optimizes power efficiency across different operating conditions. This parameter change resolves the contradiction by adapting the voltage parameter to match the required output power level.
2Reliability
If the carrier amplifier operates at class A to class AB bias, then linearity is ensured at smaller signal levels, but power efficiency deteriorates due to continuous operation
Solution Approach 1:
The patent applies dynamic voltage control to the carrier amplifier's drain terminal based on the output power level. At smaller signal levels, the voltage control circuit applies a lower second drain voltage to the carrier amplifier, improving power efficiency while maintaining acceptable linearity. At larger signal levels, the higher first drain voltage is applied to ensure adequate power output. This dynamic voltage adjustment resolves the contradiction between linearity and power efficiency.
Solution Approach 2:
The patent changes the drain voltage parameter of the carrier amplifier based on operating conditions. By switching between higher and lower drain voltages according to the output power level, the system maintains linearity when needed while improving power efficiency during low-power operation. This parameter adaptation resolves the trade-off between reliability and energy consumption.
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 improves power efficiency by operating at lower voltages during lower signal levels and higher voltages during higher signal levels, enhancing overall power amplification performance.
Implementation Method 1
a voltage converter circuit that applies a second drain voltage obtained by subjecting the first drain voltage to voltage conversion
Data Source
AI summary
Provided is a power amplification device including: a DC power supply that outputs a drain voltage; a Doherty amplifier including a carrier amplifier and a peak amplifier, which are connected in parallel, and amplifies an RF signal; a voltage control circuit that outputs a first instruction to output a low voltage when an output power is equal to or lower than a given value, and outputs a second instruction to output a high voltage when the output power is larger than the given value; and a voltage converter circuit that converts the drain voltage to a voltage lower than the drain voltage and applies the converted voltage to drain terminals of the carrier amplifier and the peak amplifier according to the first instruction, and applies the drain voltage directly to the drain terminals of the carrier amplifier and the peak amplifier according to the second instruction.