Power Converter Switching Control via Extrapolated Signal Pulses
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Solution Overview
Problem
Switched-mode power converters face challenges in maintaining continuous power output over a wide range, particularly at low load conditions, due to parasitic oscillations that decay, leading to potential discontinuity when switching on the switch based on local minima detection, and existing methods change operating modes, causing power disruptions.
Innovation Solution
A method and control circuit that extend the delay time by generating signal pulses to detect oscillations across the switch, allowing the switch to be reactivated after the oscillations have decayed, ensuring reliable detection of local minima even at low power consumption, using a pulse signal with a first portion representing local minima and a second portion obtained by extrapolating the initial signal pulses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the delay time is extended to maintain parasitic oscillation for local minima detection, then switching accuracy is improved, but the oscillation decays and detection becomes unreliable at low power consumption
Solution Approach 1:
The patent applies preliminary action by generating artificial signal pulses that represent local minima before the actual parasitic oscillation would provide them. The control circuit proactively creates these timing signals based on the relationship between the auxiliary voltage and switch voltage, ensuring that reliable switching timing information is available even when the natural oscillation has decayed too much to be detected reliably.
2Productivity
If the power converter changes operating mode to maintain continuous power output, then power continuity is improved, but mode changes cause power disruptions and loss of resonance benefits
Solution Approach 1:
The patent implements continuity of useful action by maintaining the quasi-resonant operating mode across the entire output power range, including very low power levels. The artificial pulse signal generation ensures that the beneficial resonant oscillations continue to occur and be utilized for switching timing, eliminating the need to exit the resonant mode and avoid the energy losses and disruptions associated with mode transitions.
3Loss of energy
If local minima detection is used to reduce switching losses, then switching efficiency is improved, but detection becomes unreliable when parasitic oscillation decays at low load conditions
Solution Approach 1:
The patent uses an intermediary approach by introducing artificial signal pulses as a mediator between the auxiliary voltage and the switching control. These pulses are generated based on the known relationship between the auxiliary voltage waveform and the switch voltage local minima, providing reliable switching timing information without requiring direct detection of the decayed parasitic oscillation. This intermediary signal ensures accurate switching point detection while maintaining the energy-saving benefits of resonant switching.
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
Enables continuous operation in quasi-resonant mode over a wide output power range, including low power conditions, by ensuring reliable detection of switching points, reducing switching losses and maintaining power continuity without mode changes.
Implementation Method 1
Converting power with a switched-mode power converter of this type usually includes receiving an input voltage and an input current at an input by the power converter and driving the electronic switch in a plurality of successive drive cycles, each including an on-time and an off-time, wherein the inductor receives energy from the input during the on-time and transfers energy to the rectifier circuit during the off-time
Implementation Method 2
During this delay time, a parasitic oscillation of a voltage across the inductor and the switch may occur, wherein this oscillation results from an inductance of the inductor and parasitic capacitances, such as parasitic capacitances of the switch
Data Source
AI summary
A method for operating an electronic switch in a power converter and a control circuit for operating an electronic switch in a power converter are disclosed. The method includes: driving an electronic switch coupled to an inductor in a power converter in successive drive cycles each including an on-time and an off-time, wherein the off-time includes a demagnetization time period in which the inductor is demagnetized and a delay time, and wherein an end of the delay time is dependent on the occurrence of a predefined number of signal pulses of a pulse signal. The pulse signal includes a first portion that represents local minima of a voltage across the switch and, a second portion that includes signal pulses obtained by timely extrapolating the pulse signal of the first portion.