Current-Mode Step Up/Down Switching Regulator Without RHP Zero
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing step up/down switching regulators face issues with right half-plane zero characteristics, increased cost due to additional components, and difficulty in maintaining responsiveness and stability across varying battery voltages, particularly in idling-stop vehicles.
Innovation Solution
A switching regulator design that incorporates a current mode control mechanism, utilizing a step-down control circuit with MOS transistors, an inductor, and a current detection circuit to maintain stability and responsiveness without increasing component costs, by ensuring the transfer function does not exhibit right half-plane zeros and maintaining a response characteristic similar to step-down mode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a general step up/down switching regulator structure is used, then output voltage can be maintained when input voltage decreases, but right half-plane zero characteristics appear and responsiveness deteriorates
Solution Approach 1:
The patent applies dynamics by making the on-duty of the first step-up switch fixed rather than variable, and introducing a second step-up switch that operates with a fixed duty cycle. This dynamic configuration change eliminates the right half-plane zero characteristic while maintaining output voltage stability across varying input voltages, thereby improving responsiveness without sacrificing reliability.
2Speed
If additional components are added to improve responsiveness, then response characteristic improves, but device complexity and cost increase
Solution Approach 1:
The patent achieves multi-functionality by using the inductor L1 for both step-down and step-up operations, and by having the control unit CNT11 manage multiple switching modes (step-down, step up/down, and step-up) with a single control architecture. The fixed on-duty configuration of the first step-up switch Q13 simplifies the control logic while maintaining improved responsiveness, avoiding the need for additional complex components.
3Measurement precision
If current mode control is implemented with traditional structures, then control precision improves, but right half-plane zero characteristics appear causing stability issues
Solution Approach 1:
The patent applies parameter changes by fixing the on-duty of the first step-up switch Q13 to a constant value rather than allowing it to vary with load conditions. This parameter fixation eliminates the right half-plane zero characteristic that typically appears in current mode control, thereby maintaining both control precision and system stability across different operating conditions.
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 design achieves stable operation across varying battery voltages with reduced component costs, maintaining output voltage stability and responsiveness, and simplifies current mode control, thereby addressing the limitations of existing regulators.
Implementation Method 1
an inductor L11, MOS transistors Q13 and Q14 as step-up switches
Implementation Method 2
an output capacitor C11
Data Source
Figure 1
Figure 2A~2B
Figure 3~4
AI summary
Provided is a switching regulator in which a MOS transistor Q1 (first switch) and a MOS transistor Q2 (second switch) are complementarily turned on/off according to an output voltage VOUT, and in which a MOS transistor Q3 (third switch) and a MOS transistor Q4 (fourth switch) are complementarity turned on/off by fixing an on-duty D of the MOS transistor Q3 (third switch) in a step up/down mode. The switching regulator performs current mode control according to information of current flowing in the second switch.