Power Supply Reverse Current Detection Circuit
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Solution Overview
Problem
The existing power supply system allows reverse currents to flow from a secondary battery into the synchronous rectifier circuit when the output voltage falls below the battery's charged voltage, leading to battery discharge.
Innovation Solution
Incorporating a reverse current determination circuit that uses a logical OR signal and existing current detection components to detect reverse currents and stop switching operations, preventing continuous reverse current flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the synchronous rectifier circuit continues operating when output voltage falls below battery charged voltage, then the rectifier circuit maintains its rectifying function, but reverse current flows from the battery into the rectifier circuit causing battery discharge
Solution Approach 1:
The control circuit performs preliminary detection of reverse current conditions by monitoring the current detector output during the stopped period before reverse current damage occurs. When reverse current is detected, the control circuit preemptively stops the switching elements to prevent continuous reverse current flow and battery discharge, thus resolving the contradiction between maintaining rectifier operation and preventing harmful reverse current effects
Solution Approach 2:
The control circuit establishes a feedback mechanism where the current detector continuously monitors current flow direction and magnitude, and this detection signal feeds back to the control circuit. The control circuit adjusts the switching element operation based on this feedback, stopping operation when reverse current is detected, thereby preventing battery discharge while maintaining reliable rectifier operation under normal conditions
2Reliability
If a reverse current detection system is added to prevent reverse current flow, then reverse current discharge is prevented, but the device complexity increases
Solution Approach 1:
The current detector is designed with multi-functionality, serving both as an overcurrent protection device during normal operation and as a reverse current detection device when needed. By making the current detector universal, the patent avoids adding separate dedicated reverse current detection hardware, thus preventing reverse current discharge while minimizing increases in device complexity
Solution Approach 2:
The patent merges the reverse current detection function with the existing control circuit and current detector system. The control circuit integrates both normal operation control and reverse current detection/stop functions into a unified control mechanism, eliminating the need for separate complex reverse current protection circuits and thereby resolving the contradiction between reliability improvement and device complexity
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
Effectively prevents reverse current discharge from the secondary battery by using existing components for overcurrent detection, allowing for a simpler configuration and stable detection of reverse currents.
Implementation Method 1
a current transformer, which is interposed on one DC power supply line out of the pair of DC power supply lines and outputs a voltage signal whose waveform changes in keeping with a current waveform of a current that flows to the switch
Implementation Method 2
a rectifier circuit, which rectifies the voltage signal and outputs as an output current detection signal
Implementation Method 3
an isolation transformer including a primary winding and a secondary winding
Implementation Method 4
a synchronous rectifier that includes a first synchronous rectifier element and a second synchronous rectifier element, is connected to the secondary winding, and rectifies and outputs an induced voltage generated in the secondary winding
Data Source
AI summary
Reverse currents are prevented using existing components, like a primary-side current transformer. A power supply includes an isolation transformer, a switch, a synchronous rectifier, a smoother, a controller with a signal generator circuit that outputs main drive signals for main switching elements of the switch and drive signals for synchronous rectifier elements of the synchronous rectifier, and a current detector that has a current transformer, detects a current flowing to the switch, and outputs an output current detection signal. The controller includes an OR circuit that generates an OR signal for the main drive signals and a reverse current determination circuit that determines whether a reverse current has occurred based on the OR signal and the output current detection signal. When the occurrence of a reverse current has been determined, outputting of the main drive signals and the drive signals is stopped.