LED Driver IC Pin Reduction via Integrated Current Sources
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Solution Overview
Problem
Conventional light emitting device controller circuits require a large number of pins due to the need for external high-voltage transistors to manage multiple LED channels, increasing complexity and pin count.
Innovation Solution
Integration of current source circuits within the integrated circuit and the use of transistor switches with a control voltage to manage LED channels, reducing the number of pins required by allowing low-voltage devices to be used and incorporating a short circuit detection mechanism without additional pins.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If external high-voltage transistors are used to control multiple LED channels, then the brightness control capability is improved, but the pin count increases to twice the number of channels
Solution Approach 1:
The patent combines multiple current source circuits and their control functions into a single integrated circuit. The controller integrates N current source circuits (CSI-CSN) that can control N LED channels, reducing the need for separate external transistors and their associated pins. The integrated circuit provides control voltages (VGI-VGN) to transistor switches located outside the IC, consolidating multiple functions into one device and reducing pin count from 2N to N+1 pins.
2Power
If high-voltage transistors are placed outside the integrated circuit, then the voltage handling capability is improved, but the integration level deteriorates
Solution Approach 1:
The patent extracts the high-voltage transistor switches (M1-MN) from the integrated circuit and places them outside the IC. This allows the integrated circuit to use low-voltage devices for the current source circuits, while the external transistors handle the high-voltage requirements for LED channels. The integrated circuit provides control voltages to these external transistors, achieving a division of labor that satisfies both voltage handling and integration requirements.
3Reliability
If drain signals of external transistors are connected to the integrated circuit for monitoring, then the fault detection capability is improved, but the pin count increases to three times the channel number
Solution Approach 1:
The integrated circuit uses the same control pins (P1-PN) that provide control voltages to the external transistors to also acquire drain signals for monitoring. The controller can detect short circuits by monitoring the drain signals through existing pins, making these pins serve multiple functions: control signal output and fault detection input. This multi-functionality avoids the need for additional dedicated monitoring pins.
Data Source
AI summary
The present invention discloses a circuit and a method for controlling a light emitting device, and an integrated circuit therefore. The circuit for controlling a light emitting device comprises: a power stage controller circuit controlling a power stage circuit to convert an input voltage to an output voltage, which is supplied to at least one light emitting device channel including at least one light emitting device; a transistor switch in the light emitting device channel; and a current source circuit controlling a current through the light emitting device channel, wherein the power stage controller circuit and the current source circuit are integrated in an integrated circuit which provides a control voltage to control a gate of the transistor switch.