DC Power Supply Discharge Unit for LED Feedback Protection
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Solution Overview
Problem
Existing power supply devices for driving LEDs face issues with high-voltage feedback causing internal circuit elements to break, leading to increased production costs and complexity when trying to prevent floating nodes during shutdown.
Innovation Solution
A direct-current power supply device with a switching element, a control circuit, a variable current source, and a discharge unit connected between the external terminal and ground, which is turned on by a shutdown signal to discharge the output current into the ground, preventing internal element damage without requiring high-voltage elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the constant current source is turned off by a shutdown signal to prevent floating nodes, then the circuit stability is improved, but the feedback terminal potential rises to output voltage level which may break internal elements
Solution Approach 1:
A discharge unit (resistor and switch) is introduced as an intermediary component between the feedback terminal and ground. This discharge unit provides a safe discharge path for feedback current during shutdown, preventing both floating nodes and high-voltage damage to internal elements. The resistor limits current while the switch controls the discharge path activation.
2Object-affected harmful factors
If high-voltage elements are used to replace internal elements connected to feedback terminal, then the resistance to high-voltage feedback is improved, but the area and process complexity increase leading to high production costs
Solution Approach 1:
The harmful high-voltage feedback effect is extracted and redirected through the discharge unit to ground, away from the sensitive internal elements. This allows the use of standard low-voltage rated components in the control circuit while still protecting against high-voltage feedback conditions during shutdown.
3Ease of operation
If the variable current source is turned off during shutdown, then the drive current control is improved, but the feedback terminal becomes open state causing potential rise
Solution Approach 1:
The discharge unit is activated simultaneously with or immediately after the variable current source shutdown. This preliminary action ensures that the feedback terminal has a discharge path ready before the current source stops sourcing current, preventing potential rise and maintaining terminal stability throughout the shutdown transition.
Data Source
AI summary
Disclosed is a direct-current power supply device, including: an inductor; a switching element to intermittently supply a current to the inductor; an external terminal to which an output current of an external unit is fed back; a control circuit to generate a pulse signal having a pulse width corresponding to an output voltage of the external terminal, generate a drive signal for driving the switching element in response to the pulse signal, and output the drive signal to the switching element; a variable current source which is connected to the external terminal and which is turned on and off in response to a shutdown signal; and a discharge unit which is connected between the external terminal and a ground point and which is turned on in response to the shutdown signal so that the output current fed back to the external terminal is discharged into the ground point.