Boost Power Supply PWM Protection for Low-Voltage Heat Control
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Solution Overview
Problem
Conventional power supply circuit protection methods for liquid crystal display backlights, particularly in vehicles, face challenges in accurately detecting load and preventing breakdown due to high power loss and heat generation, especially when input voltage is low, leading to potential part destruction.
Innovation Solution
A voltage detection unit is implemented to sense the input voltage and generate a control signal with a reduced duty cycle when the input voltage meets a predetermined condition, thereby reducing the load on the power supply circuit and protecting it from breakdown.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a step-up power supply circuit is used to obtain high brightness, then the backlight performance is improved, but the load due to power loss increases and parts may be destroyed due to heat generation
Solution Approach 1:
The patent applies preliminary action by detecting the input voltage before the power supply circuit operates and proactively adjusting the duty cycle to prevent excessive power loss and heat generation. The control device monitors VIN and preemptively modifies PWM signal parameters to keep the power supply circuit within safe operating limits, preventing the contradiction from manifesting into actual damage.
Solution Approach 2:
The patent implements feedback by continuously monitoring the input voltage VIN and using this information to dynamically adjust the duty cycle of the PWM signal. The control device creates a closed-loop system where the power supply circuit's operating conditions are fed back to the controller, which then optimizes the duty cycle to balance brightness output with power loss prevention, resolving the contradiction between illumination intensity and energy loss.
2Adaptability or versatility
If the boosting range is large to raise low input voltage to output voltage, then the power supply circuit can operate with low input voltage, but the load due to power loss increases significantly
Solution Approach 1:
The patent applies dynamics by making the duty cycle adjustable and variable rather than fixed. The control device dynamically changes the duty cycle based on the detected input voltage level, creating an adaptive power supply system that optimizes its operation in real-time. This dynamic adjustment allows the system to maintain input voltage adaptability while minimizing power loss by using higher duty cycles only when necessary for low input voltages.
Solution Approach 2:
The patent implements parameter changes by modifying the duty cycle parameter of the PWM signal based on the input voltage detection. When VIN is low, the duty cycle is increased to maintain adequate power transfer; when VIN is high, the duty cycle is reduced to minimize power loss. This parameter adjustment strategy resolves the contradiction between maintaining broad input voltage adaptability and minimizing energy loss across different operating conditions.
3Reliability
If temperature sensor is attached in the vicinity of the power supply circuit for protection, then heat detection is enabled, but the detection accuracy is reduced due to position differences and ambient temperature inclusion
Solution Approach 1:
The patent applies preliminary action by detecting the input voltage VIN before the power supply circuit generates heat and operating proactively to prevent excessive temperature rise. Rather than reactively measuring temperature after heat generation, the system preemptively adjusts the duty cycle based on voltage detection, eliminating the need for temperature sensors and their associated measurement precision problems while maintaining protection capability.
Solution Approach 2:
The patent uses input voltage detection as an intermediary parameter to indirectly monitor and control the power supply circuit's operating conditions. Instead of directly measuring temperature with a sensor, the system uses VIN as a proxy indicator that correlates with power loss and heat generation. This intermediary approach provides more accurate and reliable protection information without the measurement precision limitations of direct temperature sensing.
Data Source
AI summary
A power supply circuit protection device has a PWM control circuit and a voltage sensor that detects an input voltage to be supplied to a step-up power supply circuit. When it is sensed that the input voltage detected by the voltage sensor satisfies a predetermined voltage condition, the PWM control circuit sets the duty cycle of a PWM signal to a value smaller than a duty cycle setting at a normal time. On the basis that the load of the step-up power supply circuit correlates to the input voltage, the input voltage to the step-up power supply circuit is detected by the voltage sensor. This enables the load of the step-up power supply circuit to be more accurately detected. Therefore, when the duty cycle of the PWM signal is set to a value smaller than at the normal time, the load of the step-up power supply circuit is reduced.