Variable Pulse Width Control for Single-Inductor Dual-Output Power Circuits
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Solution Overview
Problem
Single-inductor dual-output power circuits generate peak currents that lead to noise and electromagnetic interference (EMI) due to fixed on-time and off-time pulse signals, which are not effectively managed.
Innovation Solution
The solution involves adjusting the pulse width of either the maximum on-time or minimum off-time pulse signals based on comparisons of positive and negative voltages with reference values, using comparison units, a controller, and a pulse width adjuster to control switch control signals and prevent excessive peak current flow through the inductor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fixed period on-time and off-time pulse signals are used, then the converter meets desired current capacity, but peak current increases causing noise and EMI
Solution Approach 1:
The patent applies dynamics by making the on-time pulse signal width variable rather than fixed. The controller adjusts the pulse width dynamically based on the difference between reference voltage and actual output voltage, allowing the system to adapt to different operating conditions and prevent excessive peak current while maintaining current capacity.
Solution Approach 2:
The patent changes the parameter of pulse width from a fixed value to a variable parameter controlled by voltage comparison. By modifying the pulse width parameter based on voltage feedback, the system optimizes current flow to avoid peak current issues while maintaining the required current capacity for reliable operation.
2Ease of operation
If fixed period pulse signals are used, then the switching operation is simple, but inductor current increases abnormally
Solution Approach 1:
The patent implements feedback control by comparing the actual output voltage with a reference voltage and using the voltage difference to adjust the on-time pulse width. This feedback mechanism prevents abnormal inductor current increase while maintaining simple switching operation through automated controller adjustment.
Solution Approach 2:
The system transitions from static fixed-period pulse signals to dynamic variable-width pulse signals that adapt to real-time voltage conditions. This dynamic adjustment prevents excessive inductor current while keeping the switching operation straightforward through controller management.
3Power
If on-time pulse width is increased to meet current capacity, then current delivery is sufficient, but peak current and EMI increase
Solution Approach 1:
The patent uses dynamic pulse width adjustment based on voltage feedback to deliver sufficient current without excessive peak current. The controller modulates the on-time pulse width in real-time, increasing it only when needed to maintain current capacity while avoiding the EMI problems associated with consistently high peak current.
Solution Approach 2:
The system changes the pulse width parameter dynamically based on voltage conditions, allowing sufficient current delivery when required while minimizing peak current during normal operation. This parameter modulation resolves the contradiction between power delivery and EMI generation.
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
This adjustment stabilizes the inductor current, preventing abnormal increases and reducing noise and EMI in the power circuit.
Implementation Method 1
a current flows through the inductor L
Implementation Method 2
capacitors C1 and C2 for performing smoothing functions
Data Source
AI summary
An apparatus configured to control a pulse frequency modulation in a single-inductor dual-output power circuit. The apparatus fixes a pulse width of one of a maximum on-time pulse signal (which is used to define a maximum on-time during which a current flowing through the inductor is generated) and a minimum off-time pulse signal (which is used to define a minimum off-time during which either the boost voltage converter or the buck-boost voltage converter produces a positive voltage or a negative voltage). The apparatus adjusts a pulse width of the other pulse signal.