LED Driver IC Power Readiness Detection Circuit
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Solution Overview
Problem
Existing LED backlight systems for LCD panels face issues with uneven brightness due to potential erroneous open- or short-circuit determinations when the system is first connected to power, leading to incorrect operation of the LED chain driving circuit.
Innovation Solution
An integrated circuit with a detection node, comparator, and logic controller is used to assert a ready signal only when the sense voltage exceeds a reference voltage, ensuring that the LED chains are not driven until the power is sufficiently ready, thereby preventing erroneous determinations and ensuring even brightness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the LED chain driving circuit is connected to power immediately, then the system can start operating quickly, but erroneous open-circuit or short-circuit determinations occur due to insufficient power readiness
Solution Approach 1:
The patent applies preliminary action by asserting a ready signal before enabling the LED chain driving circuit. The logic controller monitors a sense voltage and only asserts the ready signal when the sense voltage exceeds a reference voltage, ensuring power is sufficiently ready before the LED chains are driven. This prevents erroneous determinations while maintaining relatively quick startup by not delaying unnecessarily.
2Reliability
If the LED chain driving circuit waits for power readiness before operation, then erroneous determinations are prevented, but system startup time increases
Solution Approach 1:
The patent performs the necessary power readiness check (sensing and comparison) in advance before enabling LED operation. The logic controller continuously monitors the sense voltage and prepares the ready signal assertion, so that when power is ready, the transition to LED operation can occur immediately without excessive delay. This balances reliability with minimal startup time loss.
Solution Approach 2:
The patent uses dynamic voltage monitoring where the sense voltage is continuously compared against the reference voltage. The ready signal is dynamically asserted or deasserted based on the real-time relationship between sense voltage and reference voltage, allowing the system to transition quickly from waiting state to operational state as soon as power conditions are met.
3Illumination intensity
If sensing circuitry is added to detect LED open- or short-circuits, then brightness uniformity is improved, but device complexity increases
Solution Approach 1:
The patent makes the existing sense voltage node serve multiple functions: it is used both for the normal LED chain driving operation and for the power readiness detection. The same sense voltage that reflects LED chain status is also used by the logic controller to determine when power is ready. This eliminates the need for separate sensing circuitry while maintaining brightness uniformity through proper power sequencing.
Solution Approach 2:
The system uses its own existing voltage signals (sense voltage from the LED chain) to perform the power readiness detection. Rather than adding external sensing circuitry, the system leverages its internal voltage nodes and existing components to determine when it is safe to operate, reducing overall circuit complexity while achieving the desired protection function.
Data Source
AI summary
An integrated circuit is capable of controlling current through several light-emitting diode (LED) chains, each having several LEDs forward-connected in series between a major anode and a major cathode. Each major anode is coupled to a power node. The integrated circuit has several driving circuits, a detection node, a comparator, and a logic controller. The driving circuits can light the LED chains, respectively. Detection voltage at the detection node corresponds to voltage at one of the major cathodes. The comparator asserts a ready signal when the detection voltage exceeds a reference voltage. Receiving a dimming signal and the ready signal, if the dimming signal is asserted and the ready signal has been asserted, the logic controller enables the driving circuits to light the LED chains.