Display Power Supply Dead-Time Control via LX Node Sensing
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Solution Overview
Problem
Existing display apparatuses face challenges in reducing power consumption and dead time during switching operations, which affects the stability and efficiency of power generation, especially under zero current conditions.
Innovation Solution
A power supply system for display apparatuses that includes an output circuit with first and second switches and an output controller with a driving circuit. The driving circuit senses the LX node voltage to determine if the body diodes of the switches are turned on, and based on this, it controls the dead time for each switch to optimize power generation and maintain stability during zero current conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the switching operation is performed with fixed dead time, then the switching operation is simple to control, but the power consumption increases and the dead time cannot be optimized under zero current conditions
Solution Approach 1:
The dead time is made dynamic rather than fixed. The controller adjusts the dead time duration based on real-time detection of zero current conditions and body diode states. When zero current is detected, the dead time is extended to ensure proper body diode turn-off; otherwise, a shorter dead time is used to minimize switching losses and improve efficiency.
Solution Approach 2:
The system implements feedback control by continuously monitoring the current state and body diode turn-on status. Based on this feedback, the controller dynamically adjusts the dead time parameter to optimize power consumption while ensuring reliable switching operation under varying load conditions.
2Productivity
If the dead time is reduced to improve switching efficiency, then the power generation efficiency improves, but the stability of switching operation deteriorates under zero current conditions
Solution Approach 1:
The dead time is dynamically adjusted based on operating conditions. Under zero current conditions, the dead time is automatically extended to maintain switching stability. During normal operation with sufficient current, the dead time is reduced to maximize power generation efficiency, thus resolving the contradiction between efficiency and stability.
Solution Approach 2:
The dead time parameter is changed adaptively rather than remaining constant. The system detects zero current conditions and modifies the dead time parameter accordingly, allowing short dead time for high efficiency during normal operation and long dead time for stability during zero current conditions.
3Reliability
If the body diode turn-on time is not detected, then the control circuit is simple, but the dead time cannot be accurately controlled to prevent shoot-through current
Solution Approach 1:
The control circuit uses feedback from body diode detection to accurately determine when the body diode turns on. This feedback information is used to precisely control the dead time duration, ensuring that the switching transistor turns off before the body diode conducts, thereby preventing shoot-through current while maintaining circuit simplicity.
Solution Approach 2:
Instead of using complex hardware circuits to prevent shoot-through, the system uses software-based detection and control. The controller detects body diode turn-on through voltage sensing and programmatically adjusts the dead time, replacing complex hardware protection circuits with flexible software control logic.
Data Source
AI summary
A display apparatus includes a display panel configured to display an image, a panel driver configured to drive the display panel, and a power supply including an output circuit, including a first switch and a second switch configured to charge or discharge power input through an input terminal thereof to output through an output terminal thereof, and an output controller including a driving circuit configured to control charging or discharging of the output circuit, for supplying power to the display panel, wherein the driving circuit senses an LX node voltage of the output circuit to determine whether at least one of a first body diode included in the first switch and a second body diode included in the second switch is turned on or not, and based thereon, controls a dead time corresponding to one of the first switch and the second switch.