Display Power Supply Mode Switching for Transistor Voltage Stress
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Solution Overview
Problem
Display devices face challenges in managing high voltage differences across switching transistors due to large input and output power levels, leading to increased power consumption and circuit board size when using inverting buck boost converters.
Innovation Solution
A power supply device with a mode selector that dynamically adjusts the operation mode based on input voltage levels, reducing the voltage applied to switching transistors by varying driving methods, switching frequency, and slew rate, allowing the use of smaller transistors suitable for both battery and adapter voltage ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If an inverting buck boost converter is used to generate high potential output power, then the output power level is improved, but the withstand voltage applied to switching transistors increases
Solution Approach 1:
The patent applies dynamics by making the switching frequency variable rather than fixed. The control circuit dynamically adjusts the switching frequency based on operating conditions to optimize the balance between output power delivery and transistor voltage stress, allowing the system to adapt to different load and input voltage conditions
Solution Approach 2:
The patent changes the parameter of switching frequency to resolve the contradiction. By varying the switching frequency, the system can achieve high output power while controlling the voltage stress on transistors, as the frequency adjustment affects both power transfer efficiency and voltage waveform characteristics
2Adaptability or versatility
If switching transistors are designed for high voltage ranges, then adapter voltage range is covered, but power consumption increases and Y-axis size of PCB increases
Solution Approach 1:
The patent uses dynamics by implementing variable switching frequency control that adapts to different input voltage conditions. This allows the use of smaller transistors optimized for battery voltage ranges while dynamically adjusting operation to handle adapter voltage inputs, reducing both power consumption and physical size compared to using fixed high-voltage-rated transistors
Solution Approach 2:
The patent changes the switching frequency parameter based on input voltage levels. By adjusting this parameter, the system can efficiently process both battery and adapter voltage ranges using smaller transistors, avoiding the need to design for maximum voltage stress which would increase power consumption and component size
3Use of energy by moving object
If switching frequency is increased to improve power conversion efficiency, then power consumption is reduced, but voltage stress on transistors increases
Solution Approach 1:
The patent applies dynamics by implementing variable switching frequency control that adapts to different operating conditions. The control circuit dynamically adjusts the switching frequency to optimize the balance between power consumption and voltage stress, allowing high frequency operation when it benefits efficiency while limiting frequency when voltage stress becomes excessive
Data Source
AI summary
A DC-DC converter includes a first converter outputting a first power voltage in a first driving method of generating an inductor current by alternately turning on transistors in a normal mode and outputting the first power voltage in a second driving method of generating the inductor current with the number of turn-on times less than that of the first driving method in a power saving mode, a second converter outputting a second power voltage in a third driving method of generating the inductor current with the number of turn-on times less than that of the second driving method in the power saving mode and determining differently magnitudes of the second power voltage in the power saving mode and the second power voltage in the normal mode, and a mode selector supplying a mode control signal to the converters to drive the converters according to one of the modes.