LDO Regulator Offset Voltage for Ripple Rejection
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Solution Overview
Problem
Low drop-out (LDO) voltage regulators face challenges in automotive applications due to noise, power supply ripple, and electromagnetic interference (EMI) caused by current spikes, which are not effectively addressed by existing solutions that often increase costs and reduce reliability.
Innovation Solution
A system comprising a first transistor, a capacitor, and a circuit configuration that includes a cascode transistor and a regulation transistor with compensation capacitors to provide an offset voltage referenced to the output voltage, reducing noise and EMI by improving power supply ripple rejection (PSRR) and managing current spikes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If external capacitors are used to reduce power supply ripple, then ripple rejection is improved, but cost increases and reliability decreases
Solution Approach 1:
The patent implements a feedback mechanism where the control circuit continuously monitors the output voltage and adjusts the pass transistor's gate voltage accordingly. This closed-loop feedback system actively compensates for power supply ripple without requiring external capacitors, thereby improving ripple rejection while maintaining reliability.
Solution Approach 2:
The patent replaces the passive mechanical/electrical approach of using external capacitors with an active electronic control system. The control circuit uses electronic signal processing to generate compensation voltages that counteract ripple effects, substituting passive component-based ripple filtering with active electronic control.
2Productivity
If the LDO regulator responds quickly to current spikes, then load regulation is improved, but electromagnetic interference (EMI) increases
Solution Approach 1:
The patent implements a dynamic control mechanism that adapts the regulator's response characteristics based on operating conditions. The control circuit can adjust its gain and bandwidth dynamically, enabling fast response to legitimate load changes while filtering out high-frequency EMI-generating transitions, thus achieving both fast load regulation and reduced EMI.
Solution Approach 2:
The patent changes key control parameters such as compensation capacitance values and feedback network resistances to optimize the regulator's frequency response. By carefully selecting these parameters, the system achieves fast transient response for load regulation while suppressing high-frequency oscillations that would generate EMI.
3Loss of energy
If gate voltage pumping is used to reduce drop-out voltage, then power efficiency is improved, but noise and power consumption increase
Solution Approach 1:
The patent introduces an intermediary control circuit that mediates between the power supply and the pass transistor. Instead of directly pumping gate voltage, the control circuit generates compensated gate drive signals that achieve low drop-out voltage without the high-frequency switching noise associated with traditional gate voltage pumping methods.
Data Source
AI summary
A system including a first transistor, a first capacitor and a circuit. The first transistor has a first control input and is configured to regulate an output voltage. The first capacitor is coupled at one end to the first control input and at another end to a circuit reference. The circuit is configured to provide a first voltage to the first control input, where the first voltage includes an offset voltage that is referenced to the output voltage and adjusted to compensate for variations in the first transistor.