Variable Sample-and-Hold Circuit for Power Converter Load Adaptation
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Solution Overview
Problem
Existing sample-and-hold circuits for power converters use a fixed sample time, which leads to poor regulation and incorrect sampling of voltage VFB when the load on the secondary side of the power converter changes, resulting in inefficient control of the output voltage.
Innovation Solution
A sample-and-hold circuit that includes a first and second voltage generator and a stabilization capacitor, where the second voltage generator outputs a voltage based on a multiple of the discharge time of the secondary side and a predetermined delay time, and the stabilization capacitor stabilizes the voltage, allowing the circuit to adjust the sample time based on the load conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed sample time is used in the sample-and-hold circuit, then the circuit structure is simple, but the regulation effect deteriorates when the load changes
Solution Approach 1:
The patent implements a dynamic sample time mechanism where the sample time is adjusted based on the discharge time of the secondary side. The control circuit measures the discharge time and uses it to determine the appropriate sample time, transforming the fixed sample time into a variable parameter that adapts to different load conditions, thereby resolving the contradiction between circuit simplicity and regulation effectiveness
Solution Approach 2:
The patent introduces a feedback mechanism where the discharge time of the secondary side is measured and fed back to the control circuit. This feedback information is used to adjust the sample time dynamically, ensuring that the sample-and-hold circuit operates optimally under varying load conditions without requiring complex additional hardware
2Ease of operation
If a fixed sample time is used, then the circuit operation is simple, but the sampling accuracy deteriorates when the load is light
Solution Approach 1:
The patent makes the sample time dynamic by linking it to the measured discharge time. When the load is light, the discharge time changes, and the sample time is automatically adjusted accordingly, ensuring accurate sampling without requiring complex manual intervention or additional operational steps
Solution Approach 2:
The control circuit automatically measures the discharge time and determines the appropriate sample time without external intervention. The system self-adjusts the sampling parameters based on the actual operating conditions, maintaining high sampling accuracy across different load conditions while keeping the operation simple
Data Source
AI summary
A sample-and-hold circuit includes a first voltage generation unit, a second voltage generation unit, a stabilization capacitor. The first voltage generation unit generates a first voltage according to a first predetermined delay time and a voltage corresponding to an auxiliary winding of a power converter. The second voltage generation unit generates a second voltage according to K multiple of a discharge time of a secondary side of the power converter during a previous period of the power converter and the voltage, wherein K<1. When a sum of the K multiple of the discharge time and a second predetermined delay time leads a first valley of the voltage corresponding to a current period of the power converter, the second voltage generation unit outputs the second voltage. When the sum lags the first valley, the first voltage generation unit outputs the first voltage.