Boost DC-DC Converter Control Without Right-Half-Plane Zero Limits
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Solution Overview
Problem
Conventional time-based DC-DC converters face limitations due to the presence of a right-half-plane zero, which restricts the maximum achievable bandwidth and requires additional components, leading to increased area footprint and power consumption.
Innovation Solution
A boost DC-DC converter apparatus with a simplified proportional-integral controller and a time-based control loop that includes a low-pass filter and offset calibration circuit, eliminating the need for additional sensors and compensating for right-half-plane zeros, thereby extending the loop bandwidth and reducing system complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional time-based DC-DC converters use additional components to compensate for right-half-plane zero, then control stability is improved, but area footprint and device complexity increase
Solution Approach 1:
The patent extracts and eliminates the harmful right-half-plane zero from the control-to-output transfer function by using a specific switching sequence where the second switch is activated before the first switch is deactivated. This removes the need for additional compensation components while maintaining control stability.
Solution Approach 2:
Instead of adding compensation components to handle the RHP zero effect, the patent inverts the conventional approach by modifying the switching sequence itself. The second switch (S2) is turned on before the first switch (S1) is turned off, which fundamentally changes the control-to-output transfer function to eliminate the RHP zero.
2Reliability
If conventional time-based DC-DC converters add compensation components for right-half-plane zero, then control stability is improved, but power consumption increases
Solution Approach 1:
The patent removes the source of the problem (RHP zero) by changing the switching sequence, thereby eliminating the need for power-consuming compensation components. The solution achieves control stability without requiring additional active components that would consume power.
3Manufacturing precision
If the reference frequency of the converter is increased to tens of MHz, then output voltage ripples are maintained, but voltage-based control loop bandwidth and power consumption increase
Solution Approach 1:
The patent replaces the voltage-based control loop with a time-based control loop that uses timing signals and delay lines instead of voltage amplification. This substitution allows high-frequency operation (tens of MHz) while maintaining low power consumption because the time-based approach does not require high-bandwidth voltage amplifiers.
Solution Approach 2:
The patent changes the control parameter from voltage to time. By using timing-based control signals and delay elements instead of voltage amplification, the system can operate at high frequencies without proportionally increasing power consumption, as the time-based parameters do not require high-bandwidth amplification.
Data Source
AI summary
A boost DC-DC converter includes a switching network, coupled to an inductor, controlled by a PWM driving signal. A control loop receives a voltage output and provides the PWM driving signal. The control loop generates an error signal as a function of a difference between voltage output voltage and a reference, with the PWM driving signal generated based on the error signal. A low pass filter circuit within the control loop receives the PWM driving signal and provides at least one filtered signal. An adder node of the control loop receives the at least one filtered signal from the low pass filter circuit for addition to the at least one filtered signal. The PWM driving signal is generated as a function of a sum of the filtered signal and the error signal.