Display DC-DC Converter Hysteresis Mode Switching for Stable Output
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Solution Overview
Problem
As battery and adapter voltages increase, the stability of DC-DC converters in display apparatuses decreases, leading to instability in output voltage generation when input voltage exceeds output voltage.
Innovation Solution
A DC-DC converter with a mode selecting circuit that switches between different operating modes based on input voltage levels, using a first and second switch controlled by switching control signals to maintain stable output voltage, and an adaptive loader circuit to change current modes for continuous conduction, pulse skip, and discontinuous conduction modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If battery voltage and adapter voltage are increased to meet high speed charging demand, then charging speed is improved, but the stability of DC-DC converter decreases and output voltage cannot be stably generated when input voltage exceeds output voltage
Solution Approach 1:
The patent implements dynamic mode switching in the DC-DC converter based on input voltage levels. The converter transitions between different operating modes (first mode for voltage step-up, second mode for voltage step-down) according to real-time input voltage conditions, enabling stable output voltage generation across a wide input voltage range including high voltage inputs for fast charging
2Device complexity
If a single converting mode is used in DC-DC converter, then device complexity is reduced, but the converter cannot stably generate output voltage when input voltage varies widely
Solution Approach 1:
The patent divides the DC-DC converter operation into multiple converting modes (first converting mode for voltage step-up, second converting mode for voltage step-down) with distinct switch configurations. The mode selecting circuit automatically chooses the appropriate mode based on input voltage levels, enabling stable operation across wide voltage ranges while maintaining manageable device complexity through systematic mode division
3Adaptability or versatility
If mode switching threshold is set at a specific voltage level, then converting mode can be selected based on input voltage, but repetitive mode changes occur near threshold voltage causing output instability
Solution Approach 1:
The patent implements different threshold voltages for mode transition in different directions: a first threshold voltage for transitioning from first mode to second mode, and a second threshold voltage for transitioning from second mode to first mode. This asymmetric threshold design prevents repetitive mode switching near the threshold by creating a hysteresis effect, ensuring stable output voltage while maintaining adaptability to input voltage changes
Data Source
AI summary
A DC-DC converter includes: a first switch; a second switch connected to the first switch; a mode selecting circuit to select a converting mode from one of at least a first mode and a second mode based on an input voltage; and a controller to generate a first switching control signal for controlling the first switch based on the converting mode, and a second switching control signal for controlling the second switch based on the converting mode.