LDO PSRR Boost Circuit With Adaptive Bias Current Injection

The patent implements a dynamic bias current adjustment mechanism where the bias current is varied based on the detected ripple frequency and amplitude. The system transitions from a static bias current approach to a dynamic one, allowing the bias current to be increased only when and where ripple suppression is needed, thereby improving PSRR selectively without proportionally increasing overall quiescent current consumption.

The invention applies ripple suppression selectively to specific frequency ranges and circuit nodes where ripple is most problematic. By using frequency-selective filtering and targeted bias current injection at critical nodes (such as the error amplifier input), the system achieves local improvement in PSRR at problematic frequencies without applying large bias currents across the entire circuit, thus reducing overall current consumption.

The patent introduces an intermediary frequency-selective filter network and a controlled current source that acts as a mediator between the bias current generation and the main regulation loop. This intermediary structure enables frequency-selective ripple suppression by filtering specific frequency components before they affect the output, while the controlled current source provides targeted compensation current only at problematic frequencies, achieving high-frequency suppression without requiring complete redesign of the entire regulator circuit.

The invention implements a feedback mechanism where the output voltage ripple is detected and fed back to control the bias current injection. The system monitors the ripple content at the output and dynamically adjusts the PSRR enhancement circuitry accordingly. This feedback approach allows the system to achieve frequency-selective suppression by detecting specific ripple frequencies and applying corrective bias currents only when and where needed, reducing the need for complex hardwired frequency-selective circuits.