Class D Push-Pull Amplifier With Filterless Harmonic Blocking
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Solution Overview
Problem
Traditional power amplifiers face inefficiencies due to RF output filtering, which increases size, weight, cost, and complexity while reducing reliability and frequency agility, and generate undesirable harmonics that need to be filtered.
Innovation Solution
A filterless high-efficiency power amplification (HEPA) device that employs an operational harmonic block with transformers to block even harmonics and pass odd harmonics to ground, eliminating the need for output filtering and allowing only the fundamental frequency to reach the load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If RF output filtering is used to eliminate harmonics, then harmonic suppression is improved, but device weight increases substantially
Solution Approach 1:
The patent extracts and eliminates the RF output filter from the power amplifier system entirely. Instead of using traditional filtering components, the invention employs a class D push-pull amplifier configuration that inherently suppresses even harmonics through its symmetric operation and transformer coupling, removing the heavy filtering hardware while maintaining harmonic suppression performance.
Solution Approach 2:
The patent converts the potentially harmful even harmonics generated by the amplifier into a beneficial feature by using the push-pull configuration where even harmonics are naturally cancelled at the output. The transformer coupling and symmetric drive signals cause even harmonic currents to flow in opposite directions, resulting in cancellation and automatic harmonic suppression without requiring additional filtering components.
2Object-generated harmful factors
If RF output filtering is used to eliminate harmonics, then harmonic suppression is improved, but amplifier size increases
Solution Approach 1:
The patent removes the RF output filter section from the amplifier design, eliminating the space required for inductors, capacitors, and associated mounting structures. The harmonic suppression function is integrated into the core amplifier operation through the push-pull configuration, reducing overall device volume.
Solution Approach 2:
The patent merges the harmonic suppression function with the power amplification function itself. The push-pull amplifier stage simultaneously performs power amplification and even harmonic cancellation through its symmetric architecture, eliminating the need for separate filtering sections and reducing overall amplifier size.
3Object-generated harmful factors
If RF output filtering is used to eliminate harmonics, then harmonic suppression is improved, but device complexity increases
Solution Approach 1:
The patent extracts and removes the complex RF filtering network from the system, eliminating multiple inductors, capacitors, switches, and control logic that would be required for dynamic filtering. The solution simplifies the architecture by relying on the inherent symmetry of the push-pull configuration to provide harmonic suppression.
Solution Approach 2:
The amplifier system serves itself by using its own symmetric push-pull architecture to automatically cancel even harmonics. The transformer coupling and differential operation create natural cancellation of even harmonic components without requiring external filtering components or additional control systems.
4Object-generated harmful factors
If RF output filtering is used to eliminate harmonics, then harmonic suppression is improved, but reliability decreases
Solution Approach 1:
The patent removes the RF output filter components that would be potential failure points. By eliminating inductors, capacitors, and associated switches from the signal path, the system reduces the number of components that can fail, thereby improving overall reliability while maintaining harmonic suppression through the push-pull configuration.
5Adaptability or versatility
If band switching is implemented for frequency agility, then frequency adaptability is improved, but power loss increases
Solution Approach 1:
The patent maintains continuous efficient operation across frequency bands by using a broadband class D push-pull amplifier design that does not require switching between different filter configurations. The amplifier operates continuously in its high-efficiency mode across the entire frequency range, avoiding the power losses associated with band switching and filter reconfiguration.
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 solution reduces size, weight, and cost, improves reliability, and enhances frequency agility by eliminating the need for RF output filtering and band switching, resulting in an ultra-high-efficiency, low-harmonic signal.
Implementation Method 1
a first transformer coupled to the output path of the PA, the first transformer configured to block each even harmonic current of the harmonic currents. Here, the first transformer may further be configured to pass an odd harmonic current of the harmonic currents.
Implementation Method 2
The ideal source also configured to shunt the odd harmonic current to ground
Implementation Method 3
a second transformer may be coupled with the output path in parallel or series with the first transformer and at a point downstream of the operational harmonic block. The second transformer may be configured to superimpose the fundamental frequency to the load.
Data Source
AI summary
A filterless high-efficiency class D power amplifier (HEPA) exploits the phase relationships of even and odd harmonics at transistor drains of a push-pull topology to eliminate output filtering, enabling an ultra-high-efficiency, low harmonic signal. The filterless HEPA relieves the amplifier of a requirement for a power consuming filter by implementing a high-quality operational harmonic block on an output stage without output buffering. The operational harmonic block senses the voltage source radio frequency to the amplifier prior to waveform squaring and employs a harmonic canceling balun to block even harmonics (in-phase) but pass odd harmonics (180° out of phase). The sensed ideal voltage source shunts the odd-harmonic currents to ground, leaving only the fundamental current on its primary to pass to the load.