Power Converter Overcurrent Protection Threshold Adjustment
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Solution Overview
Problem
Conventional over-current protection systems in power converters are not effective across a wide range of line input voltages, leading to inconsistent maximum power delivery and potential damage due to excessive current and voltage stress, particularly during output short circuits or overloading.
Innovation Solution
A system controller that adjusts the current threshold for over-current protection based on the bulk voltage, using a ratio of the primary and secondary winding turns and a reference voltage, to ensure consistent maximum energy delivery across varying voltage conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional over-current protection systems are used in power converters, then the system structure is simple, but the protection effectiveness is inconsistent across wide range of line input voltages leading to potential damage
Solution Approach 1:
The patent implements dynamic adjustment of the over-current protection threshold based on bulk voltage levels. The controller dynamically calculates and updates the current threshold using the formula Ith = (Np/Ns) × (Vref/Rs) × (Vin/Vnom), where the threshold varies with input voltage Vin. This dynamic adaptation ensures consistent maximum power delivery and reliable protection across the full range of line input voltages, resolving the contradiction between protection effectiveness and system complexity.
Solution Approach 2:
The patent changes the protection threshold parameter based on bulk voltage conditions. By deriving the current threshold from bulk voltage through the relationship Ith ∝ Vin, the system adapts the protection level to match operating conditions. This parameter change approach maintains consistent energy delivery limits while accounting for voltage variations, effectively resolving the reliability issue without requiring complex external circuitry.
2Reliability
If the current threshold for over-current protection is adjusted based on bulk voltage, then consistent maximum energy delivery is achieved, but the control system becomes more complex
Solution Approach 1:
The patent implements feedback control by continuously monitoring bulk voltage Vin and using it to adjust the over-current protection threshold. The controller reads the bulk voltage, calculates the appropriate threshold using the derived relationship Ith = (Np/Ns) × (Vref/Rs) × (Vin/Vnom), and applies this dynamic threshold to the protection circuit. This feedback mechanism ensures consistent maximum energy delivery across varying voltage conditions while keeping the control implementation integrated and manageable.
Solution Approach 2:
The system performs self-adjustment of protection parameters based on its own operating conditions. The controller automatically derives the current threshold from the bulk voltage without requiring external intervention or complex calibration circuits. The relationship Ith ∝ Vin allows the system to self-adapt to voltage variations, maintaining reliable protection and consistent energy delivery while minimizing additional complexity.
3Reliability
If additional resistors are used for over-current protection, then the protection range is improved, but significant power is consumed
Solution Approach 1:
The patent extracts the voltage-dependent scaling function from external passive components (resistors) and implements it digitally within the controller. Instead of using additional resistors to set fixed protection thresholds, the system calculates the appropriate threshold dynamically using the formula Ith = (Np/Ns) × (Vref/Rs) × (Vin/Vnom). This extraction of the scaling function to the digital domain eliminates the need for power-consuming external resistors while maintaining extended protection range across all voltage conditions.
Solution Approach 2:
The patent replaces the mechanical/electrical approach of using physical resistors for threshold setting with a digital computation approach. The controller uses digital processing to calculate and apply the voltage-dependent current threshold, substituting the passive resistor-based mechanism with an active digital control system. This substitution eliminates the continuous power consumption associated with resistor-based voltage division while achieving the same protection range extension through computational methods.
Data Source
AI summary
System controller and method for protecting a power converter. The system controller includes a first controller terminal configured to output a drive signal to a switch to affect a first current flowing through a primary winding of a power converter. The power converter further includes a secondary winding coupled to the primary winding, and the drive signal is associated with one or more switching periods. Additionally, the system controller includes a second controller terminal configured to receive a sensing voltage from a sensing resistor. The sensing voltage represents a magnitude of the first current flowing through the primary winding of the power converter. The system controller is configured to process information associated with the sensing voltage and a reference voltage, and determine whether an average output current of the power converter is larger than a current threshold.