Buck Regulator ESL Compensation via Synchronized Voltage Offsets
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Solution Overview
Problem
Fast transient buck regulators face poor power efficiency and noise performance due to disturbances caused by the parasitic series inductance (ESL) of the output capacitor, leading to oscillations in the switching voltage.
Innovation Solution
A voltage regulator circuit that includes a reference generator, a pulse width modulator, and a level shifter to provide positive feedback, stabilizing the output voltage against ESL interactions by introducing voltage offsets synchronized with the switching node transitions, thereby preventing oscillations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the modulator component is designed to respond quickly to disturbances, then the response speed is improved, but oscillations occur due to ESL-generated negative feedback
Solution Approach 1:
The patent applies preliminary anti-action by detecting the ESL-induced voltage swing at the output node and generating a compensating signal that opposes this disturbance before it can cause oscillations. The compensation signal is injected into the feedback path to preemptively counteract the harmful effect of capacitor ESL, allowing fast response without oscillations.
2Measurement precision
If the regulator responds to ESL transitions, then response accuracy is improved, but power efficiency deteriorates due to increased switching losses
Solution Approach 1:
The patent introduces an intermediary compensation signal that mediates between the ESL-induced disturbance and the feedback control system. This compensation signal, generated through the capacitor divider network and level shifter, acts as an intermediate element that corrects the feedback error without requiring the regulator to over-react to ESL transitions, thereby maintaining accuracy while reducing unnecessary switching losses.
3Stability of the object's composition
If the reference signal level is increased to prevent oscillations, then stability is improved, but the reference signal may no longer accurately represent the desired output voltage
Solution Approach 1:
The patent segments the reference signal generation into two independent parts: the original reference voltage that maintains accuracy, and a separate compensation signal that provides the necessary offset to prevent oscillations. The compensation signal is generated through the capacitor divider network and level shifter, allowing stability improvement without compromising the accuracy of the reference signal itself.
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 solution effectively mitigates ESL-induced oscillations, improving power efficiency and noise performance by ensuring the reference signal remains above the ESL-generated artifacts, stabilizing the output voltage.
Implementation Method 1
An inductor divider is formed between the primary buck inductor L and the capacitor ESL. Each time the switching node connecting the power transistors transitions between minimum and maximum voltage (e.g., ground potential and V DD ), the voltage swing Vsw seen at the switching nodes (typically several volts) will be divided down by the ratio of the inductances of the primary inductor L and the capacitor ESL.
Implementation Method 2
the level shifter 204 introduces voltage offsets into the modulated signal 212 to produce a level-shifted modulated signal 212a that is AC-coupled to the output of the modulator circuit 202
Data Source
Figure 1
Figure 2
Figure 2A
AI summary
A fast transient switching voltage regulator includes a reference signal generator to provide a reference in a feedback path to control switching. The reference signal generator is operative to incorporate a voltage offset into the reference signal timed with the control pulses used to control the switching. The voltage offset moves the reference signal out of the way of pulses introduced in the feedback path due to capacitance ESL in the output capacitor of the switching voltage regulator.