Emulated Ripple Generator for Voltage Regulator Stability
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Solution Overview
Problem
Voltage regulators face instability when the ripple in the output voltage is small, and to maintain stability, they often require a relatively constant series resistance and additional external components, which limits the use of low ESR capacitors and increases costs.
Innovation Solution
The implementation of an emulated ripple generator allows the voltage regulator to regulate output voltage based on an emulated ripple that is in-phase with the inductor current, enabling the use of low ESR capacitors, such as ceramic capacitors, which can be internal to the integrated circuit without additional components, thereby maintaining stability and reducing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional external components are used to maintain stability with small ripple, then stability is improved, but device complexity increases
Solution Approach 1:
The patent creates an emulated ripple signal that copies the essential characteristics of the actual output voltage ripple. This emulated ripple is generated internally using simple circuit elements (resistors and capacitors) that replicate the ripple waveform shape and frequency, allowing the control loop to respond to ripple without requiring external components. The copying principle resolves the contradiction by providing the necessary stability feedback through an internal emulation rather than external hardware additions.
Solution Approach 2:
The emulated ripple signal acts as an intermediary between the actual output voltage and the control loop. Instead of directly using the small actual ripple (which provides insufficient feedback) or adding complex external components, the patent introduces an emulated ripple as a mediator that provides adequate feedback signal to the control loop. This intermediary signal has amplified amplitude while maintaining the correct frequency and phase relationship, enabling stable regulation without external components.
2Reliability
If a relatively constant series resistance is used to maintain stability, then stability is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent emulates the ripple signal using RC circuits that replicate the ripple waveform without requiring precise resistance values. The emulated ripple copying mechanism uses resistors and capacitors to generate a signal with the same frequency and phase characteristics as the actual ripple, but the amplitude can be independently controlled. This approach eliminates the need for precisely matched series resistance values, as the emulation circuit can accommodate normal component tolerances while still providing stable feedback.
3Productivity
If low ESR capacitors are used, then productivity and cost are improved, but stability deteriorates due to insufficient ripple
Solution Approach 1:
The patent enables the use of low ESR capacitors by implementing an emulated ripple generator that copies and amplifies the ripple signal. Low ESR capacitors naturally produce smaller actual ripple, which would normally insufficient for stable control. However, the emulated ripple copying circuit creates a feedback signal with adequate amplitude that mirrors the ripple characteristics, allowing the control loop to function properly even with minimal actual ripple from low ESR capacitors. This resolves the contradiction by decoupling the capacitor ESR value from the feedback signal amplitude.
Solution Approach 2:
The patent replaces the mechanical/physical ripple generation mechanism (relying on capacitor ESR to generate sufficient ripple voltage) with an electronic signal generation mechanism. Instead of depending on the physical property of capacitor ESR to create adequate ripple voltage, the system uses active circuitry to synthesize an emulated ripple signal. This substitution allows the use of low ESR capacitors while maintaining stable control, as the feedback signal is electronically generated rather than physically derived from capacitor characteristics.
Data Source
AI summary
According to an exemplary implementation, a voltage regulator includes an emulated ripple generator. The emulated ripple generator includes a high side switch configured to control charging of an emulated ripple. The emulated ripple generator further includes a low side switch configured to control discharging of the emulated ripple. The high side switch and the low side switch are configured to control the charging and the discharging such that the emulated ripple is substantially in-phase with an inductor current of the voltage regulator. The high side switch can be configured to control the charging by selectively enabling a high side current source. Furthermore, the low side switch can be configured to control the discharging by selectively enabling a low side current source.