Switching Power Supply Voltage Detection Circuit
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Solution Overview
Problem
Existing voltage detection methods in switching power supplies are overly complex and costly, often relying on optical couplers or auxiliary windings, which result in low conversion efficiency and high product costs.
Innovation Solution
A method and circuit for detecting output voltage in switching power supplies that generates a first current and a second current to charge and discharge a detection capacitor during specific time periods of a switching cycle, allowing for accurate determination of the output voltage without optical couplers or auxiliary windings, using a converting resistor and switches to control the charging and discharging process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If optical couplers or auxiliary windings are used for voltage detection, then measurement precision is improved, but device complexity and product cost increase
Solution Approach 1:
The patent extracts the voltage detection function from traditional complex components (optical couplers, auxiliary windings) and implements it using a simplified capacitor charging/discharging circuit. The detection capacitor charges during the transistor on-time and discharges during off-time, allowing voltage detection without needing optical couplers or auxiliary windings, thus reducing device complexity while maintaining detection accuracy.
Solution Approach 2:
The patent creates a simplified model of voltage detection by using a capacitor to replicate the function of complex detection circuits. Instead of using expensive optical couplers or auxiliary windings, the invention uses a capacitor whose charging/discharging characteristics copy the voltage information, providing a cheaper and simpler alternative that maintains measurement precision.
2Measurement precision
If optical couplers or auxiliary windings are used for voltage detection, then measurement precision is improved, but product cost increases
Solution Approach 1:
The patent replaces expensive, complex components (optical couplers, auxiliary windings) with inexpensive passive components (capacitor, resistors, switches). The detection capacitor and associated simple passive components cost significantly less than optical couplers or auxiliary windings, reducing product cost while maintaining voltage detection accuracy through the charging/discharging mechanism.
Solution Approach 2:
The invention uses a simplified capacitor-based model to copy the voltage detection function, replacing expensive optical couplers or auxiliary windings with cheap passive components. This copying approach maintains measurement precision while dramatically reducing product cost and simplifying manufacturing.
3Measurement precision
If traditional voltage detection methods are used, then output voltage can be detected, but conversion efficiency decreases
Solution Approach 1:
The patent implements a self-service detection mechanism where the detection capacitor uses the existing switching transistor and inductor current to charge and discharge automatically during normal operation. The capacitor charges when the transistor is on and discharges when off, using the power supply's own operational cycles without requiring separate detection power, thus improving conversion efficiency while maintaining detection capability.
Solution Approach 2:
The detection capacitor undergoes periodic charging during the transistor on-time and periodic discharging during the off-time, synchronized with the switching cycle. This periodic action allows continuous voltage detection without interfering with the power conversion process, maintaining conversion efficiency while enabling accurate output voltage monitoring.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach simplifies the circuit design, reduces product costs, and improves conversion efficiency by enabling adaptive regulation of the output voltage without the need for complex detection components, ensuring the output voltage meets the required levels for electronic products.
Implementation Method 1
charging a detection capacitor by the first current during a first time period of a switching cycle
Implementation Method 2
charging the detection capacitor by a second current during a second time period of the switching cycle, where the first and second currents flow in opposite directions
Data Source
AI summary
In one embodiment, a method of detecting a voltage can include: (i) generating a first current according to a first voltage and a converting resistor; (ii) charging a detection capacitor by the first current during a first time period of a switching cycle of a switching power supply; (iii) charging the detection capacitor by a second current during a second time period of the switching cycle; (iv) detecting a voltage across the detection capacitor to obtain a detection voltage at an end time of the second time period, where the first time period includes a rising portion of a current flowing through the inductor, and the second time period includes a decreasing portion of the inductor current; and (v) determining a state of a present output voltage of the switching power supply according to the detection voltage.