Power Converter Average Output Current Detection Circuit
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Solution Overview
Problem
Existing power converter systems face challenges in accurately detecting the average output current, particularly on the secondary side, due to the influence of inductors and gate control signal periods, leading to lower accuracy in output power calculations.
Innovation Solution
A controller and device that utilize a comparison unit and intermediate voltage generation unit to adjust intermediate voltages based on charge and discharge currents, turning-on times, and current mirrors to generate voltages corresponding to the average output current, enabling timely detection and dynamic information retrieval.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If output power is calculated based on primary side current and gate control signal period, then output power can be obtained, but accuracy is lower due to influence of inductor and period variations
Solution Approach 1:
The patent introduces an intermediate voltage as a mediator between the primary side current detection and the output power calculation. This intermediate voltage is generated by integrating the primary side current during the power switch conduction period and then discharging it during the off period. The intermediate voltage directly reflects the average output current on the secondary side, eliminating the need for complex calculations based on inductor values and gate control periods, thus improving measurement accuracy without significantly increasing device complexity.
2Loss of information
If traditional current sensing method is used on primary side, then current can be detected, but dynamic information of secondary side average output current cannot be obtained in real-time
Solution Approach 1:
The patent replaces the traditional mechanical/electrical integration method with a capacitor-based voltage integration approach. The intermediate voltage generation unit uses capacitors to integrate the primary side current during the switch conduction period and discharge during the off period. This electrical integration method provides real-time dynamic information of the average output current without time delay, as the voltage changes continuously and immediately reflects the current state of the secondary side load.
3Measurement precision
If inductor value and gate control period are used for calculation, then output power can be derived, but accuracy decreases due to parameter variations
Solution Approach 1:
The patent transforms the static calculation method (relying on fixed inductor values and gate periods) into a dynamic measurement method. The intermediate voltage is continuously updated based on the actual primary side current and switch conduction time in real-time. This dynamic approach automatically adapts to variations in load conditions, inductor parameters, and gate control settings, eliminating the accuracy degradation caused by parameter variations while maintaining system versatility.
Data Source
AI summary
A device for detecting an average output current of a power converter includes a current generation unit, a first voltage generation unit, a first current mirror unit, and a second current mirror unit. The current generation unit generates a first charge current according to an intermediate voltage. The first voltage generation unit generates a first node voltage according to the first charge current, a first discharge current, a turning-on time, and an inverse turning-on time. The first current mirror unit generates a first current according to the first node voltage, and generates a second voltage corresponding to the average output current of a secondary side of the power converter according to the first current. The second current mirror unit generates the first discharge current according to the first current.