Constant On-Time Pulse Width Control for Voltage Converter Transients
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Solution Overview
Problem
Conventional constant on-time controllers in voltage converters are limited by small ESR of output capacitors, failing to effectively detect and respond to transient events due to small output voltage ripple, and lack flexibility in adjusting on-time pulse width during transient variations.
Innovation Solution
A constant on-time pulse width control apparatus comprising a comparator, logic circuit, and controller that generates logic control signals to dynamically adjust the on-time pulse width based on amplified output voltage ripple signals and a voltage ramp signal, enabling adaptive control of switching transistors to enhance transient response.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional constant on-time controller is used, then the control structure is simple, but the transient event detection capability is poor due to small ESR of output capacitor
Solution Approach 1:
The patent introduces an intermediary circuit that includes a capacitor connected in parallel with the output capacitor and a resistor connected in series with the capacitor. This intermediary RC circuit acts as a mediator between the output voltage and the comparator, transforming the small voltage ripple signal into an amplified signal that can be effectively detected. The capacitor charges and discharges through the resistor, creating a measurable voltage change across the resistor that corresponds to the output voltage ripple, thereby solving the detection problem without significantly complicating the overall control structure.
2Device complexity
If fixed on-time pulse width is adopted, then the control is simple, but the adaptability to different transient events is poor
Solution Approach 1:
The patent implements dynamic control by making the on-time pulse width adjustable based on detected transient events. When the comparator detects a significant voltage ripple signal indicating a transient event, the controller dynamically extends the on-time pulse width to provide adequate response time. This dynamic adjustment mechanism allows the system to adapt to different transient events while maintaining simple constant on-time control during normal operation, achieving versatility without excessive complexity.
Solution Approach 2:
The patent changes the parameter of on-time pulse width dynamically in response to detected transient events. During normal operation, a fixed on-time is used for simple control. When a transient event is detected through the amplified voltage ripple signal, the on-time parameter is extended to ensure proper response. This parameter change approach enables the system to handle various transient conditions adaptively while maintaining operational simplicity during steady-state conditions.
3Loss of energy
If output capacitor with small ESR is used, then the efficiency is improved, but the transient event detection capability deteriorates
Solution Approach 1:
The patent introduces an intermediary RC circuit that decouples the detection function from the power delivery function. The output capacitor with small ESR continues to provide low-power-loss performance, while the separate RC circuit (comprising the parallel capacitor and series resistor) acts as an intermediary detection pathway. This intermediary circuit generates a measurable voltage signal across the resistor that reflects output voltage changes without requiring the output capacitor to have large ESR, thereby maintaining both efficiency and detection capability.
Data Source
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AI summary
A constant on-time pulse width control-based apparatus (103) capable of detecting a transient event of a voltage converter (100) includes a specific comparator (110), a logic circuit (115), and a controller (105). The specific comparator (110) generates a logic control signal to the logic circuit (115) according to two resultant signals (VC1, VC2) of the controller (105). The logic circuit (115) generates a pulse control signal (Ton) with an on-time pulse width to charge an output capacitor according to the logic control signal. The controller (105) generates the two resultant signals (VC1, VC2) to the specific comparator (110) by generating a voltage ramp signal (Vramp) and amplifying an output voltage ripple signal (Vripple) based on a reference voltage (Vref), and detects the transient event to dynamically adjust the on-time pulse width of the pulse control signal (Ton) according to the amplified output voltage ripple signal (VC1).