Voltage Converter Startup Current Suppression Circuit
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Solution Overview
Problem
Conventional power conversion systems, such as Flyback converters, experience high inrush currents during start-up, which can exceed device capacity and lead to damage, and existing solutions like soft start circuits or regulating circuits either increase complexity or produce sub-harmonics, making them unsuitable for heavy load conditions.
Innovation Solution
A control circuit and method that utilizes a leading edge blanking signal to suppress initial spikes in primary current, coupled with an acquisition unit and sample/hold latch to accurately measure primary current, and adjusts the oscillator frequency to prevent primary current from exceeding target values, thereby reducing inrush currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a soft start circuit is added to increase start up time, then inrush current is reduced, but device complexity increases and the problem cannot be eliminated entirely
Solution Approach 1:
The patent introduces a current detector as an intermediary component that monitors primary current and provides feedback to the controller. This mediator enables precise detection and control of inrush current without requiring complex soft-start circuits, thereby reducing overall system complexity while effectively limiting harmful current peaks during startup.
Solution Approach 2:
The patent implements a feedback mechanism where the current detector continuously monitors the primary current and feeds this information back to the controller. The controller adjusts the duty cycle of the switching element based on this feedback to maintain current within safe limits. This closed-loop feedback system effectively controls inrush current without increasing device complexity.
2Object-affected harmful factors
If a regulating circuit is added to adjust the PWM signal, then inrush current is controlled, but circuit complexity increases and sub-harmonics are produced under heavy load
Solution Approach 1:
The current detector serves as an intermediary that directly monitors primary current and provides accurate feedback to the controller. This eliminates the need for complex regulating circuits that adjust PWM signals, as the feedback from the current detector enables direct and precise control of inrush current without introducing sub-harmonics or increasing overall circuit complexity.
3Power
If maximum duty is used during start-up to provide more power, then power delivery is improved, but inrush current exceeds device capacity and causes damage risk
Solution Approach 1:
The patent employs dynamic control where the controller adjusts the duty cycle of the switching element in real-time based on feedback from the current detector. During startup, the duty cycle is dynamically optimized to provide sufficient power delivery while simultaneously maintaining current within safe limits. This dynamic adjustment resolves the contradiction between maximizing power delivery and preventing inrush current damage.
Solution Approach 2:
The feedback mechanism allows the controller to continuously monitor primary current and adjust the duty cycle accordingly. This enables the system to deliver maximum safe power during startup without exceeding device current capacity, as the feedback loop prevents inrush current while optimizing power transfer.
Data Source
AI summary
A control circuit and the control method for controlling the current voltage converter of a power conversion system in the start-up phase are disclosed. A first voltage is applied to the non-inverting input terminal of the comparator and a reference voltage is applied to the inverting input terminal of the comparator. When the first voltage exceeds the reference voltage, the comparison result from the comparator triggers the frequency of the clock signal generated by the oscillator to reduce preventing the primary current flowing through the primary winding of the transformer exceeding a pre-set value.