Output Transistor Control for Faster Switching Power Supply Response
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Solution Overview
Problem
Existing switching power supplies have room for improvement in terms of load response characteristics and source response characteristics.
Innovation Solution
A switching power supply is designed with a switching output stage that generates an output voltage by rectifying and smoothing a pulse-driven switching voltage, and includes a discharge circuit to discharge the output voltage when it remains above a target value for a predetermined time. Additionally, an oscillation circuit generates an on signal with a maximum on period, and skips the off period if the output voltage drops below a target value despite the output transistor being kept on for the maximum on period.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the output transistor is kept on for the maximum on period, then the output voltage stability is improved, but the load response characteristics deteriorate
Solution Approach 1:
The oscillation circuit dynamically adjusts the on period of the output transistor based on load conditions. When load current increases, the on period is extended beyond the maximum predetermined period to maintain output voltage, enabling the system to adapt to changing load requirements while maintaining stability
Solution Approach 2:
The patent changes the operating parameters of the output transistor by allowing the on period to exceed the maximum predetermined period under specific load conditions. This parameter change enables faster response to load variations while maintaining voltage stability during normal operation
2Speed
If the switching frequency is increased to improve response speed, then the load response characteristics are improved, but the source response characteristics deteriorate
Solution Approach 1:
The system dynamically adjusts the on period based on detected load current levels. When load current exceeds a predetermined threshold, the on period is extended, allowing the system to respond quickly to load changes without requiring a permanent increase in switching frequency that would affect source response characteristics
3Speed
If the on period is extended beyond maximum to improve response, then the response speed is improved, but the risk of output voltage instability increases
Solution Approach 1:
The oscillation circuit continuously detects the load current and uses this feedback to determine when to extend the on period. This feedback mechanism ensures that the on period is extended only when necessary to maintain output voltage during load transients, preventing unnecessary extensions that would cause voltage instability
Solution Approach 2:
The system temporarily changes the on period parameter beyond its maximum predetermined value only under specific detected load conditions, allowing rapid response when needed while maintaining stable operation during normal conditions through controlled parameter variation
Data Source
AI summary
A switching power supply includes a switching output stage configured to generate an output voltage by rectifying and smoothing a switching voltage that is pulse-driven as an output transistor is turned on and off. An oscillation circuit is configured to generate an on signal that alternates between an on period and an off period at a predetermined switching frequency, and a logic circuit is configured to set the on period of the on signal as a maximum on period of the output transistor. The oscillation circuit is configured to skip the off period of the on signal when, despite the output transistor being kept on for the maximum on period, the output voltage drops below a target value.