Load Controller Backup Input Circuit for Headlamp Fail-Safe Drive
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Solution Overview
Problem
Existing load controllers fail to maintain operation and ensure safety when the input side experiences a failure, particularly in vehicles where a headlamp may not turn on, due to static electricity or surging voltage affecting the input circuit.
Innovation Solution
A load controller design that includes a first input circuit detecting a drive instruction signal below a threshold, activating a constant current source to supply a PWM signal or constant control signal, ensuring the load can be driven even during input side failures through a PWM drive control signal or constant drive control signal, thereby maintaining operation and enhancing safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single input circuit and comparator are used for PWM control, then the device structure is simple, but the reliability deteriorates when the input circuit fails due to static electricity or surging voltage
Solution Approach 1:
The input circuit is divided into two independent parallel input circuits (first input circuit and second input circuit), each with its own comparator. This segmentation ensures that if one input circuit fails, the other can still detect the drive instruction signal and maintain PWM control operation, thus improving reliability without requiring a complete system redesign
Solution Approach 2:
The patent implements a backup input circuit and comparator that remain standby ready to take over if the primary input circuit fails. This beforehand cushioning approach prepares compensatory measures in advance, ensuring that when static electricity or surging voltage damages the primary input circuit, the system can immediately switch to the backup circuit to maintain headlamp operation
2Ease of manufacture
If the input circuit is simplified for ease of manufacture, then the manufacturing cost is reduced, but the resistance to harmful factors like static electricity decreases
Solution Approach 1:
The input circuit is segmented into two independent parallel input circuits, each capable of independently detecting the drive instruction signal. This segmentation allows the system to tolerate damage from static electricity or surging voltage in one circuit while the other remains functional, thereby improving resistance to harmful factors without significantly complicating the manufacturing process
Solution Approach 2:
The patent changes the system's operational parameter from relying on a single input circuit to utilizing two parallel input circuits with different threshold values. This parameter change enables the system to maintain functionality under varying conditions, including when one circuit is affected by harmful factors like static electricity
Data Source
AI summary
A load controller includes: a first input circuit which detects that a drive instruction signal by an operation of a drive instructing unit is less or equal to a first input threshold value; a first constant current source activated in accordance with the detection; a PWM signal supply unit that is activated by the first constant current source and supplies a PWM signal having a prescribed frequency and a duty ratio; a constant control signal supply unit that supplies a constant control signal during failure of the first input circuit or the first constant current source; a drive control unit that generates a PWM drive control signal in accordance with the PWM signal and generates a constant drive control signal in accordance with the constant control signal; and a load driving element that is controlled by the PWM drive or constant drive control signal to drive a load.