Overvoltage Protection Circuit for Switched-Mode Power Supplies
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Solution Overview
Problem
Switched-mode power supplies (SMPS) face inefficiencies due to voltage fluctuations, leading to potential damage from overvoltage and unnecessary power dissipation, which existing protection circuits fail to adequately address.
Innovation Solution
An overvoltage protection circuit is implemented on the primary side of the SMPS, utilizing a band gap reference comparator and a low voltage blocker in parallel with an input capacitor, which remains inactive during normal voltage ranges and inactivates the SMPS controller when an overvoltage is detected, preventing damage and power dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protection circuit is continuously active to detect overvoltage conditions, then overvoltage protection reliability is improved, but power dissipation increases during normal operation
Solution Approach 1:
The protection circuit transitions from a static continuously-active state to a dynamic state that adapts based on voltage conditions. The circuit alternates between an active protection mode (when overvoltage is detected) and an inactive low-power mode (during normal operation), optimizing both reliability and energy efficiency through state changes.
Solution Approach 2:
The circuit changes its operational parameters based on the voltage level. By monitoring the voltage parameter and switching between active and inactive states, the circuit adjusts its power consumption and protection functionality dynamically, resolving the contradiction between continuous protection and energy savings.
2Loss of energy
If the protection circuit remains inactive during normal operation, then power dissipation is reduced, but response time to overvoltage conditions increases
Solution Approach 1:
The circuit performs preliminary monitoring of voltage conditions even in inactive state, maintaining readiness to detect overvoltage conditions. This preliminary surveillance ensures rapid response when needed while minimizing power consumption during normal operation, as the circuit only fully activates when abnormal conditions are detected.
Solution Approach 2:
The protection circuit uses feedback from voltage sensing to determine when to activate. The continuous voltage monitoring provides feedback that triggers circuit activation only when overvoltage conditions are detected, balancing low power consumption with rapid response capability.
3Measurement precision
If the band gap reference comparator is continuously energized, then overvoltage detection precision is improved, but unnecessary power dissipation occurs during normal voltage ranges
Solution Approach 1:
The band gap reference comparator operates periodically rather than continuously. It is energized only during periods when overvoltage detection is necessary (when voltage exceeds normal ranges) and remains de-energized during normal operation, maintaining detection precision when needed while eliminating unnecessary power dissipation.
Solution Approach 2:
The comparator operates at full precision only when necessary (partial action principle). During normal voltage ranges, the comparator is completely deactivated rather than operating at reduced precision, achieving optimal balance between measurement accuracy and energy consumption by applying full measurement capability only when required.
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 solution effectively prevents damage from overvoltage and reduces inefficient power dissipation by ensuring the SMPS controller is only activated when necessary, enhancing the reliability and efficiency of the power supply.
Implementation Method 1
The low voltage blocker (5) ensures that if a bus voltage that is lower than a certain level is measured, a band gap reference comparator that is in series with said low voltage blocker is not energized
Implementation Method 2
said band gap reference comparator in response to a bus potential greater than the upper limit of said predefined voltage range, inactivates said switched-mode power supply controller
Implementation Method 3
The AC power is rectified by a half-wave rectifier, i.e. a diode (2) and filtered into a DC voltage by an input capacitor (4)
Implementation Method 4
a transformer having primary and secondary windings (9 and 10)... building up magnetizing flux in said primary winding (9), which in turn induces a current in said secondary winding (10)
Data Source
Figure 1~2
AI summary
The present invention relates to electrical power supplies and, more particularly, to an overvoltage protection and power saving circuit in switched-mode power supplies (SMPS) (1). It is proposed a switched-mode power supply (1) coupled to an AC voltage source and comprising a transformer having a primary side winding and a secondary side winding, said switched-mode power supply (1) further comprising a rectifier, an input capacitor and an SMPS controller. According to the invention, a low voltage blocker ensures that if a bus voltage that is lower than a certain level is measured, a band gap reference comparator that is in series with said low voltage blocker is be energized.