Transformer-Coupled RF Power Amplifier Switching Around Parasitic Capacitance
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Solution Overview
Problem
High-frequency power amplifying devices face efficiency issues due to parasitic capacitances when differential amplifiers are set to non-operating states, leading to impedance matching problems and increased power consumption.
Innovation Solution
Incorporating a switch and reactance elements in series between nodes of the differential amplifier, which are controlled to simulate an 'off' state, effectively canceling out the influence of parasitic capacitances and maintaining high impedance or short-circuiting the secondary coil to reduce power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If differential amplifiers are set to non-operating state by turning off transistors, then power consumption is reduced, but parasitic capacitances remain and cause impedance matching deterioration
Solution Approach 1:
The patent extracts the harmful parasitic capacitance effect by introducing a switching mechanism that selectively connects or disconnects the primary coil from the differential amplifier output. When the differential amplifier is in non-operating state, the switch opens the circuit path, effectively removing the parasitic capacitance influence on impedance matching while maintaining the power savings from the off state.
Solution Approach 2:
The patent implements dynamic control of the circuit configuration by using switches that change state based on the operating mode. The switch connected to the primary coil dynamically opens or closes the circuit path, allowing the system to adapt between high-impedance (operating) and low-impedance (non-operating) states, thereby resolving the contradiction between power consumption and impedance matching.
2Loss of energy
If differential amplifiers are set to high-impedance state, then power consumption is reduced, but parasitic capacitances still affect impedance matching
Solution Approach 1:
The patent removes the problematic parasitic capacitance effect by physically opening the circuit path through a switch when the differential amplifier is in high-impedance state. This extraction of the harmful element (parasitic capacitance influence) allows the system to achieve both low power consumption and proper impedance matching without adding significant circuit complexity.
3Adaptability or versatility
If multiple differential amplifiers are used for different power modes, then adaptability is improved, but the influence of non-operating amplifiers on operating amplifier increases
Solution Approach 1:
The patent segments the coupling path between differential amplifiers by introducing individual switches for each primary coil. This segmentation allows each differential amplifier to be independently controlled and isolated when in non-operating state, preventing the parasitic capacitances of inactive amplifiers from affecting the impedance matching of the active amplifier while maintaining adaptability across different power modes.
Solution Approach 2:
The patent implements dynamic isolation of differential amplifiers using switches that respond to the operating state of each amplifier. When a differential amplifier transitions to non-operating state, its associated switch opens the circuit path, dynamically preventing the parasitic capacitance of that amplifier from influencing the impedance matching of other operating amplifiers, thereby maintaining system reliability across multiple power modes.
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 configuration allows for high-efficiency power transmission to the load by minimizing the impact of non-operating differential amplifiers' capacitances, reducing power consumption, and simplifying impedance matching.
Implementation Method 1
parasitic capacitances CP11 and CP12 remain between the source and drain of the MOSFETs
Implementation Method 2
the impedance seen from the secondary coil of TR11 to the primary coil side is not in a complete open state but has some value
Implementation Method 3
a first secondary coil (LD3) magnetically coupled to the first primary coil
Data Source
AI summary
The present invention provides a high-frequency power amplifying device capable of transmitting output power at high efficiency. For example, a high-frequency power amplifying device has first and second differential amplifiers and a transformer for matching output impedances of the differential amplifiers. Between differential output nodes of the first differential amplifier, an inductor, a switch, and an inductor are coupled in series. When the second differential amplifier is in an operating state and the first differential amplifier is in a non-operating state, the switch is controlled to be on. In this case, due to “off capacitance” in transistors of a differential pair included in the first differential amplifier, impedance on the first differential amplifier side seen from both ends of primary coils becomes a high impedance state (parallel resonance state) and, equivalently, the primary coils do not exert influence on the operation of the second differential amplifier.