Clamp Circuit for Power Supply Rejection Ratio
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Solution Overview
Problem
Power supplies with low power supply rejection ratio (PSRR) are susceptible to significant output voltage transients due to input voltage transients, which can negatively impact applications requiring stable voltage levels, such as active matrix organic light emitting diodes (AMOLEDs).
Innovation Solution
A clamp circuit is integrated into the power supply, utilizing a source-follower circuit and logic gates to generate a reference voltage that is less sensitive to input voltage transients, thereby reducing the amplitude of output voltage transients and increasing the PSRR.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional power supply circuit is used without a clamp circuit, then the circuit complexity is low, but the power supply rejection ratio (PSRR) is poor and output voltage is highly sensitive to input voltage transients
Solution Approach 1:
The patent introduces a clamp circuit as an intermediary component between the input voltage source and the reference voltage generator. This clamp circuit includes a first clamp circuit input coupled to the voltage regulator input, and a clamp circuit output coupled to the VREF power supply input. The clamp circuit acts as a mediator that isolates the reference voltage generator from input voltage transients, thereby improving PSRR without requiring fundamental changes to the overall power supply architecture.
Solution Approach 2:
The patent segments the power supply circuit into distinct functional blocks: a voltage regulator section, a clamp circuit section, and a reference voltage generator section. By dividing the circuit into these segments, the clamp circuit can be independently optimized for transient suppression while the other sections maintain their original functions. This segmentation allows the PSRR improvement to be achieved in a modular fashion without redesigning the entire power supply system.
2Stability of the object's composition
If the reference voltage generator is directly coupled to the voltage regulator input, then the device complexity is low, but the output voltage experiences large amplitude changes during input voltage transients
Solution Approach 1:
The clamp circuit serves as an intermediary between the voltage regulator input and the reference voltage generator. It includes a second clamp circuit input coupled to the voltage regulator output and utilizes a source-follower circuit having the second clamp circuit input. This intermediary structure prevents input voltage transients from directly affecting the reference voltage generator, thereby stabilizing the output voltage while adding minimal complexity through the use of standard transistor configurations.
Solution Approach 2:
The clamp circuit provides beforehand cushioning by preparing a stable reference voltage supply for the VREF generator before input voltage transients can affect it. The clamp circuit is positioned to clamp or limit voltage variations at its output during power-on cycles and steady-state operations, cushioning the reference voltage generator against transient effects before they can propagate through the system.
3Reliability
If no clamp circuit is used, then the manufacturing cost is low, but the power supply cannot effectively reject input voltage transients during power-on and steady-state operations
Solution Approach 1:
The clamp circuit is introduced as an intermediary stage that can be manufactured as a separate module or integrated into the existing power supply chip. It includes standard components such as transistors configured as source-followers and logic gates, which are commonly available in standard semiconductor fabrication processes. This approach improves transient rejection capability without requiring exotic manufacturing techniques or specialized processes.
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
The clamp circuit effectively minimizes output voltage transients, ensuring that the power supply's output voltage remains stable and less susceptible to glitches, even during power-on cycles and steady-state operations, thereby enhancing the power supply's ability to drive loads like AMOLEDs with reduced voltage deviations.
Implementation Method 1
The clamp circuit includes a source-follower circuit having the second clamp circuit input
Data Source
AI summary
A circuit includes a digital-to-analog converter (DAC) having a DAC input and a DAC output. The circuit includes a reference voltage (VREF) generator having a VREF generator input, a VREF generator output, and a VREF power supply input. The VREF generator output is coupled to the DAC input. A voltage regulator has a voltage regulator input and a voltage regulator output. The voltage regulator output is coupled to the DAC. A clamp circuit has a first clamp circuit input, a second clamp circuit input, and a clamp circuit output. The first clamp circuit input is coupled to the voltage regulator input, and the clamp circuit output is coupled to the VREF power supply input. The second clamp circuit input is coupled to the voltage regulator output. The clamp circuit includes a source-follower circuit having the second clamp circuit input.