Hiccup Mode Overload Protection in DC-to-DC Converters
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Solution Overview
Problem
In primary side regulated converters, imperfect cross regulation prevents the voltage on the feedback winding from reducing when the output load is high and the auxiliary load is low, making it difficult to trigger hiccup mode for overload protection, which is costly and complex to implement using existing methods.
Innovation Solution
A DC-to-DC converter with a transformer having a primary and secondary coil, a switching circuit with a first sense circuit for voltage detection and a second sense circuit for current detection, and an auxiliary winding for feedback, along with a comparator circuit to boost the feedback signal and initiate hiccup mode when an overload is detected, allowing reliable overload detection and power dissipation in both windings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If auxiliary transformer winding is used for feedback, then cost is reduced and reliability is improved, but voltage feedback signal does not reduce during overload making hiccup mode triggering impossible
Solution Approach 1:
The feedback signal is segmented into two independent sources: the auxiliary winding voltage feedback and the primary side current sense feedback. This allows the system to use the strengths of each - the auxiliary winding for normal operation feedback and the current sense for accurate overload detection - without the limitations of either alone.
Solution Approach 2:
The patent combines the auxiliary winding feedback path with a primary side current sense path into a unified feedback mechanism. The current sense resistor and associated circuitry are integrated with the existing auxiliary winding feedback to create a composite feedback signal that enables both continuous regulation and reliable overload detection.
2Manufacturing precision
If opto-coupler is used for voltage feedback, then voltage and current regulation is improved, but device complexity and cost increase
Solution Approach 1:
The patent introduces a current sense resistor as an intermediary element that converts the difficult-to-detect overload condition (auxiliary winding voltage not dropping) into an easily detectable signal (voltage across sense resistor). This intermediary enables accurate overload detection without requiring complex circuitry or opto-couplers.
Solution Approach 2:
The patent replaces the optical isolation mechanism (opto-coupler) with an electrical sensing mechanism using a current sense resistor and associated comparison circuitry. This substitution maintains the necessary isolation while simplifying the overall system by eliminating the optical components and their associated complexity.
3Loss of energy
If hiccup mode is triggered, then power loss is reduced during overload, but requires reliable overload detection capability
Solution Approach 1:
The patent implements a feedback mechanism where the voltage across the current sense resistor is continuously monitored and fed back to the control circuit. This feedback enables real-time detection of overload conditions and automatic triggering of hiccup mode when the sensed voltage exceeds a predetermined threshold, ensuring energy loss is minimized during overload events.
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
Enables reliable triggering of hiccup mode for overload protection without the need for costly opto-isolators or complex circuit designs, reducing power loss and maintaining isolation between the primary and secondary sides.
Implementation Method 1
an auxiliary winding electromagnetically coupled to the primary and/or the secondary transformer coils of the transformer that feeds back to the first sense circuit a first signal indicating a voltage condition at the transformer
Implementation Method 2
a switching circuit that supplies a periodic signal to a switch to energize the primary transformer coil, the voltage condition being used to regulate the duty cycle of the switch and to initiate a hiccup mode that dissipates power in the primary and/or secondary windings
Data Source
AI summary
A DC-to-DC converter includes a transformer including a primary transformer coil connected to a power input terminal; a secondary transformer coil connected to a power output terminal; a switching circuit including a first sense circuit that detects a voltage condition of the transformer, the voltage received at the first sense circuit being used to regulate the duty cycle of the switch and to initiate a hiccup mode that dissipates power in the primary and/or secondary windings when the voltage condition detected at the first sense circuit indicates an overload of the transformer; a second sense circuit that detects an over-current condition at the switch and/or primary winding; and a further feedback path connected between the second sense circuit and the first sense circuit that provides a second signal to the first sense circuit to boost the first signal when an overload is detected, and to initiate the hiccup mode.