Buck-Boost Latch Circuitry for Fixed-Frequency Regulator Control
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Solution Overview
Problem
Conventional step up-step down switching regulators experience increased electromagnetic interference (EMI) and inconsistent switching frequency during buck-boost mode operation, failing to maintain a fixed frequency.
Innovation Solution
Incorporation of buck-boost latch circuitry that controls transitions between buck, boost, and buck-boost modes based on predetermined on-time values, using clock signals and comparators to ensure switches operate at a fixed frequency, preventing transitions until on-time reaches minimum or exceeds maximum values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional control circuit controls switches in buck-boost mode, then the regulator can operate when input voltage is close to output voltage, but the switching frequency becomes inconsistent and EMI increases
Solution Approach 1:
The patent applies periodic action by using a fixed-frequency clock signal to control the switching of all switches in buck-boost mode. The clock signal ensures that switches S1-S4 are turned on and off at predetermined fixed frequency intervals, eliminating the inconsistent switching behavior that causes EMI. This periodic control mechanism maintains regular switching patterns even when the regulator operates in the challenging buck-boost mode where input voltage is close to output voltage.
Solution Approach 2:
The patent implements feedback through latch circuitry that monitors the operational mode and provides feedback control signals to maintain fixed-frequency switching. The latch circuitry detects when the regulator enters buck-boost mode and activates the fixed-frequency control mechanism, creating a closed-loop system that adapts the switching behavior based on real-time operational conditions. This feedback ensures that the switching frequency remains consistent regardless of the voltage differential between input and output.
2Adaptability or versatility
If conventional control circuit controls switches in buck-boost mode, then the regulator can operate when input voltage is close to output voltage, but the switching frequency cannot be maintained at a fixed value
Solution Approach 1:
The patent applies periodic action by using a fixed-frequency clock signal to control the switching of all switches in buck-boost mode. The clock signal ensures that switches S1-S4 are turned on and off at predetermined fixed frequency intervals, eliminating the inconsistent switching behavior that causes EMI. This periodic control mechanism maintains regular switching patterns even when the regulator operates in the challenging buck-boost mode where input voltage is close to output voltage.
Solution Approach 2:
The patent applies parameter changes by transitioning from variable-frequency control to fixed-frequency control when operating in buck-boost mode. The control circuit detects the buck-boost condition and changes the switching parameter from error amplifier-driven variable frequency to clock-signal-driven fixed frequency, thereby stabilizing the switching frequency parameter while maintaining operational versatility across different voltage conditions.
3Measurement precision
If error amplifier controls switches off before minimum on-time is reached, then voltage regulation can be maintained, but switching frequency becomes variable and EMI increases
Solution Approach 1:
The patent applies preliminary action by pre-establishing minimum on-time requirements for switches in buck-boost mode before voltage regulation takes effect. The latch circuitry ensures that switches remain on for a predetermined minimum duration regardless of the error amplifier's regulation signals, preventing premature switch turn-off. This preliminary timing constraint ensures that voltage regulation precision is maintained while avoiding the variable-frequency switching that generates EMI.
Solution Approach 2:
The patent applies periodic action by using a fixed-frequency clock signal to control the switching of all switches in buck-boost mode. The clock signal ensures that switches S1-S4 are turned on and off at predetermined fixed frequency intervals, eliminating the inconsistent switching behavior that causes EMI. This periodic control mechanism maintains regular switching patterns even when the regulator operates in the challenging buck-boost mode where input voltage is close to output voltage.
Data Source
AI summary
Novel circuitry and methodology for controlling a step up-step down switching regulator that produces a regulated output signal at an output node in response to an input signal at an input node, and has an inductive device, a plurality of switching circuits for providing connection of the inductive device to the input and output nodes and a ground node, and a switch control circuit for driving the switching devices so as to enable the power supply system to operate in a boost mode to increase the input signal, in a buck mode to decrease the input signal, and in a buck-boost mode when a difference between the input signal and the output signal is within a predetermined range. Buck-boost latch circuitry is provided for latching a transition between the buck mode and the buck-boost mode, or between the boost mode and the buck-boost mode based on a predetermined condition.