Current Resonance Power Supply Low-Voltage Detection
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Solution Overview
Problem
Conventional switching power supplies of the current resonance type face challenges in achieving power saving, particularly in the stop state, due to the continuous consumption of power by voltage divider resistors used in low-voltage detection circuits.
Innovation Solution
The proposed solution involves a low-voltage detection circuit that utilizes the drain-source voltage of FETs to detect the AC input voltage, eliminating the need for voltage divider resistors and thereby reducing power consumption during both normal and stop states by stopping switching operations when a low voltage is detected.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a voltage divider resistor is used to detect AC input voltage, then low voltage detection is achieved, but power is continuously consumed even in stop state
Solution Approach 1:
The patent extracts the voltage detection function from the conventional voltage divider resistor circuit and relocates it to the control IC. The control IC measures the voltage across the FET during its off-state, eliminating the need for a separate voltage divider resistor that would continuously consume power. This extraction of the detection function to a different location (the control IC) resolves the contradiction by enabling detection without continuous power consumption.
Solution Approach 2:
The patent implements self-service by using the FET's own voltage during its off-state as the detection signal. Instead of requiring an external voltage divider circuit that continuously draws power, the system utilizes the naturally occurring voltage across the FET when it is off to detect the AC input voltage level. This self-service approach eliminates the need for separate detection components and their associated power consumption.
2Stability of the object's composition
If on-period of FET is extended to maintain constant output, then output stability is improved, but overcurrent state and through-current are generated
Solution Approach 1:
The patent implements feedback by having the control IC continuously monitor the voltage across the FET during its off-state. When the AC input voltage drops below a predetermined threshold, the control IC detects this through the FET voltage and responds by extending the off-period of the FET. This feedback mechanism allows the system to maintain output stability while preventing overcurrent and through-current conditions by dynamically adjusting the switching timing based on real-time voltage detection.
Solution Approach 2:
The patent applies preliminary action by detecting the AC input voltage level before the harmful overcurrent or through-current conditions can develop. By monitoring the FET voltage during the off-state and detecting low input voltage conditions in advance, the control IC can proactively extend the off-period to prevent the generation of harmful currents, rather than reacting after the damage has occurred.
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 effectively prevents overcurrent states and through-currents, reducing power consumption and achieving greater power saving compared to conventional methods while maintaining stable DC output.
Implementation Method 1
after the FET is turned off, a reverse recovery current of the FET that has been turned off is generated, causing a through-current to flow
Implementation Method 2
a voltage acquired by rectifying and smoothing an alternating-current voltage (hereinafter, AC input voltage) input from a commercial power supply by means of switching elements, and outputs a stable direct-current (DC) voltage via an insulating transformer
Implementation Method 3
a capacitor for current resonance
Data Source
AI summary
A current resonance power supply (301) includes a transformer (115) having a primary winding and a secondary winding, two switching elements (106, 107) connected to one end of the primary winding (116) of the transformer (115) and arranged in series, a resonance capacitor (108) connected to the other end of the primary winding (116), and a voltage detection unit connected between the one end of the primary winding (116) and the two switching elements (106, 107) and configured to detect a voltage input to a primary side of the transformer (115) , wherein operations of the switching elements (106, 107) are stopped, or increased in rate, based on the voltage detected by the voltage detection unit.