LED Driver Current Source Circuit With Dual-MOS Static Discharge Path
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Solution Overview
Problem
Conventional LED driver circuits lack protection against static electricity, which can damage transistors in the current source circuit and LED string, especially during connections with conductors, leading to device malfunction or destruction.
Innovation Solution
A current source device with a sourcing circuit using high-voltage and low-voltage MOS transistors, along with a control circuit and discharge circuit, to manage and discharge static electricity, ensuring the withstand voltage of the high-voltage MOS transistor is higher than that of the low-voltage transistor, providing multiple discharge paths without high-voltage electrostatic discharge elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional LED driver circuit without static electricity protection is used, then the circuit structure is simple and power consumption is low, but the transistor is destroyed by static electricity applied to the common terminal
Solution Approach 1:
The circuit is divided into two separate MOS transistor paths: a first MOS transistor path for normal current operation and a second MOS transistor path for static electricity discharge. This segmentation allows each path to be optimized for its specific function, with the second path specifically designed to handle high-voltage static electricity events without interfering with normal circuit operation.
Solution Approach 2:
The second MOS transistor is pre-configured with a higher withstand voltage rating and is kept in a standby state, ready to activate when static electricity is detected. The control circuit continuously monitors the common terminal and can quickly switch to the protection path when needed, preventing damage before it occurs.
2Ease of manufacture
If separate modules for LED string and current source circuit are used with conductor connections, then the modules can be independently manufactured and assembled, but the transistor is destroyed by static electricity applied at the connection part
Solution Approach 1:
The second MOS transistor acts as an intermediary protection element between the external connection terminal and the internal sensitive transistor. It provides a dedicated discharge path that intercepts static electricity before it can reach the vulnerable internal circuitry, while allowing normal signal and power connections to pass through unaffected.
3Reliability
If high-voltage electrostatic discharge elements are used to protect against static electricity, then the circuit is protected from static damage, but the chip size increases and power consumption increases
Solution Approach 1:
The protection circuit uses a second MOS transistor with withstand voltage higher than needed for normal operation, but this transistor remains inactive during normal operation. It only activates when static electricity exceeds the threshold, providing protection only when needed and avoiding continuous power consumption or size overhead for the protection capability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Effectively protects internal circuits from static electricity, reduces chip size, and minimizes power consumption by stabilizing operations and efficiently discharging static electricity.
Implementation Method 1
a first MOS transistor configured to transmit a current flowing from a pad to a first node in response to a current control voltage
Implementation Method 2
a second MOS transistor configured to transmit the current flowing from the first node to a ground in response to a bias voltage
Implementation Method 3
an amplifier configured to generate the current control voltage based on a setting voltage applied from an outside and a voltage of the first node
Data Source
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AI summary
A current source device for electrostatic discharge and a display device including the same are disclosed. A current source device according to one of the various embodiments of the present disclosure can include a sourcing circuit including a first MOS transistor configured to transmit a current flowing from a pad to a first node in response to a current control voltage, and a second MOS transistor configured to transmit the current flowing from the first node to a ground in response to a bias voltage; and a control circuit including an amplifier configured to generate the current control voltage based on a setting voltage applied from an outside and a voltage of the first node, a first resistor disposed between an output terminal of the amplifier and a gate terminal of the first MOS transistor, and a first switch configured to transmit the bias voltage to a gate terminal of the second MOS transistor in response to a switching control signal, wherein the current flowing from the pad contains a current corresponding to static electricity, wherein a withstand voltage of the first MOS transistor is higher than that of the second MOS transistor.