Power Supply Switch Control Circuit With Slope Compensator
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Solution Overview
Problem
Power supply devices experience excessive drain current beyond maximum current limitation values, particularly during high AC line voltage periods, leading to potential damage to the power switch, especially under overload conditions.
Innovation Solution
A power supply device with a switch control circuit that includes a feedback circuit and a slope compensator to generate a threshold voltage with a decreasing slope, controlling the switching operation of the power switch to prevent excessive current by maintaining constant impedance initially and increasing it later, thereby preventing the drain current from exceeding the maximum current limitation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the power switch is turned off after a delay period following the drain current reaching the reference value, then the switching operation is completed, but the drain current exceeds the maximum current limitation value
Solution Approach 1:
The patent applies preliminary action by generating the threshold voltage with a curved line waveform before the switching operation begins. This pre-established threshold voltage profile anticipates the drain current increase during the delay period, ensuring that the power switch is turned off at the precise moment when the drain current would otherwise exceed the maximum current limitation value, thus preventing overcurrent damage before it occurs.
Solution Approach 2:
The patent implements feedback by using the curved line waveform threshold voltage as a dynamic reference that automatically adjusts the power switch turn-off timing. The threshold voltage waveform provides continuous feedback information about the maximum allowable drain current throughout the switching cycle, enabling the control circuit to precisely control the turn-off moment and maintain drain current within safe limits.
2Productivity
If the drain current increases during the delay period, then the switching cycle is completed, but the drain current may be over the maximum current limitation value
Solution Approach 1:
The patent applies preliminary action by pre-generating the threshold voltage with a curved line waveform that accounts for the expected drain current increase during the delay period. This allows the control circuit to predict when the drain current will reach the maximum limitation value and turn off the power switch at that precise moment, ensuring complete switching operation while preventing overcurrent.
3Power
If the AC line voltage is high, then the power supply output is increased, but the drain current increases quickly to exceed the maximum current limitation value
Solution Approach 1:
The patent applies dynamics by using a threshold voltage that varies dynamically throughout the switching cycle rather than remaining constant. The curved line waveform of the threshold voltage adapts to the changing drain current conditions, particularly during high AC line voltage periods when the drain current increases rapidly. This dynamic threshold voltage ensures precise turn-off control regardless of the rate of current increase or the AC line voltage level.
Data Source
AI summary
The present invention relates to a power supply device generating an output power by using an AC line voltage generated through rectification of an AC input, and a driving method thereof. The power supply device controls the switching operation of the power switch by using a sensing voltage corresponding to the drain current flowing to the power switch and the feedback voltage corresponding to the output voltage. The power supply device controls the feedback current every switching cycle to generate a threshold voltage, and compares the sensing voltage and the threshold voltage to control the turn-off of the power switch. The feedback current includes the first current to generate the feedback voltage, and the threshold voltage follows a curved line waveform in which the increasing slope is decreased during the switching cycle.