Power Converter Controller with Loop Impedance Modulation
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Solution Overview
Problem
Existing switching power converters face significant power losses at light loads due to uncontrolled switching frequency and uncontrollable output ripple, primarily because of the limitations in load detection circuits and burst switching, which generate acoustic noise and are inefficient.
Innovation Solution
A control circuit with a switching circuit, soft start circuit, and comparison circuit that generates a mode signal to disable the switching signal at light loads, using an external capacitor and resistive device to determine the off period of the switching signal, thereby controlling pulse width and reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If burst switching is used to reduce power loss at light load, then power efficiency is improved, but output ripple becomes uncontrollable and acoustic noise is generated
Solution Approach 1:
The patent implements periodic action by using a programmable counter to generate controlled switching cycles. Instead of uncontrolled burst switching, the counter enables a predetermined number of switching cycles followed by an off period, creating a periodic pattern that reduces power loss while maintaining controllability of output ripple through programmed parameters.
Solution Approach 2:
The patent applies parameter changes by making the switching frequency and cycle duration programmable through external resistors and capacitors. This allows dynamic adjustment of the switching behavior to optimize between power efficiency and output ripple control, resolving the contradiction by enabling adaptive parameter tuning based on load conditions.
2Difficulty of detecting and measuring
If hysteresis comparator is used for load detection, then load condition detection is achieved, but switching frequency cannot be programmed and acoustic noise is generated
Solution Approach 1:
The patent replaces the mechanical hysteresis comparator system with an electronic counter-based detection mechanism. The counter counts switching cycles and generates control signals based on programmable thresholds, eliminating the fixed hysteresis behavior while maintaining load detection capability and enabling programmable switching frequency control.
Solution Approach 2:
The patent introduces dynamics by replacing the static hysteresis threshold with a dynamic counting mechanism. The counter can be programmed to trigger at different cycle counts, allowing adaptive load detection that can adjust to different operating conditions and enable programmable switching frequency without the limitations of fixed hysteresis.
3Manufacturing precision
If switching frequency is increased to improve regulation, then output regulation is improved, but power loss increases at light load
Solution Approach 1:
The patent uses periodic action to alternate between high-frequency switching for regulation and off periods for power savings. The programmable counter controls the duty cycle, enabling the converter to operate at high frequency when regulation is needed and enter low-power mode when load conditions permit, thus resolving the trade-off between regulation quality and power consumption.
Solution Approach 2:
The patent applies dynamics by making the switching frequency and duty cycle programmable and adaptive. The system can dynamically adjust the switching behavior based on load conditions, maintaining high frequency for good regulation when needed while reducing frequency or entering burst mode when power efficiency is the priority, eliminating the fixed trade-off.
Data Source
AI summary
A control circuit is provided to generate a mode signal at light load of the power converter. The mode signal is coupled to disable the switching signal for saving power. The impedance of an input circuit is increased in response to the mode signal. Furthermore, a soft start circuit is initiated by the mode signal when switching signal is enabled. An external capacitor associates with the impedance of the input circuit determine the off period of the switching signal.