Switching control circuit, switching power supply, and electric apparatus
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Solution Overview
Problem
Switching power supplies at light loads experience inefficiency due to short operation periods in intermittent operation modes, leading to insufficient efficiency.
Innovation Solution
A switching control circuit that introduces a prohibition mechanism to delay the start of the next operation period by a predetermined time, ensuring a minimum duration of the current operation period, thereby preventing short cycles and enhancing efficiency at light loads. This circuit includes a constant current source, comparators, and logic gates to manage the switching element's operation based on feedback voltage thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If intermittent operation mode is used at light load to reduce switching frequency, then switching loss is reduced and efficiency is improved, but operation period becomes too short which results in insufficient efficiency improvement
Solution Approach 1:
The prohibition part is activated in advance at the start of each operation period to prevent the next operation period from starting too soon. This preliminary action ensures that a minimum duration is maintained for each operation period, preventing the short operation period problem while still allowing intermittent operation mode to reduce switching loss at light loads.
2Measurement precision
If operation period and pause period are switched based on feedback voltage comparison with threshold value, then output voltage control is achieved, but operation period may appear in short period causing insufficient efficiency
Solution Approach 1:
The prohibition part acts as an intermediary mechanism between the feedback voltage comparison result and the switching element control. Even when the feedback voltage triggers an operation period start, the prohibition part ensures a minimum duration before allowing the next operation period, thus preventing short operation periods while maintaining the feedback-based output voltage control.
3Speed
If switching frequency is increased to improve power supply response, then dynamic performance is improved, but switching loss increases reducing efficiency
Solution Approach 1:
The switching element operates in a periodic intermittent mode where operation periods and pause periods alternate. By controlling the duration of operation periods to be sufficiently long through the prohibition mechanism, and appropriately setting the pause period length, the system achieves both adequate response speed and reduced switching loss through optimized periodic operation.
Data Source
AI summary
There is provided a configuration of a switching control circuit for use with a switching power supply which generates an output voltage from an input voltage, the switching control circuit having an intermittent operation mode where an operation period in which a switching element of the switching power supply is switched and a pause period in which the switching element is not switched are repeated. The switching control circuit includes a prohibition part configured to prohibit starting a next operation period until a predetermined period of time elapses from a time that a current operation period starts, in the intermittent operation mode.