Constant Current Power Supply Feedback Period Restriction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing constant current power supply apparatuses with isolation type converters experience time delays in feedback control due to the use of transformers, leading to inconsistent current supply to LEDs, especially during PWM control, resulting in suboptimal performance and increased magnetic flux resonance.
Innovation Solution
A constant current power supply apparatus that includes a feedback signal generator circuit, a feedback circuit for feeding back the feedback signal from the secondary side to the primary side, and a feedback period restricting circuit that limits the feedback period to the logical sum of the ON period and a replenishment period, ensuring stable power supply during time delays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If feedback control is performed continuously in isolation type converter, then current control precision is improved, but time delay causes excessive power supply and current inconsistency
Solution Approach 1:
The invention performs preliminary actions by storing feedback signals during the ON period and proactively controlling the switching device during the time delay period. The controller stores the feedback signal when the switching device is on, and uses this stored signal to control the switching device during the subsequent time delay period, ensuring continuous and stable power supply without waiting for real-time feedback.
Solution Approach 2:
The invention implements periodic action by dividing the control into distinct periods: ON period for storing feedback signals, time delay period for maintaining power supply using stored signals, and OFF period for halting power supply. This periodic control strategy ensures that feedback control is effectively performed during active periods while avoiding the issues caused by continuous control during time delays.
2Reliability
If feedback control is halted during OFF period, then power supply stability is improved, but excessive power is supplied during time delay
Solution Approach 1:
The controller performs preliminary action by storing the feedback signal during the ON period before the time delay occurs. This stored feedback signal is then used to control the switching device during the time delay period, ensuring that power supply is maintained at appropriate levels without excessive power consumption, thereby improving energy efficiency.
3Reliability
If minimum off-period is extended to account for time delay, then power supply stability is improved, but productivity and response speed deteriorate
Solution Approach 1:
The controller performs preliminary action by storing the feedback signal during the ON period and using this stored signal to control the switching device during the time delay period. This approach maintains power supply stability without extending the minimum off-period, thereby preserving productivity and response speed.
4Device complexity
If feedback signal is used directly without storage, then device complexity is reduced, but current control precision deteriorates due to time delay
Solution Approach 1:
The controller performs preliminary action by storing the feedback signal during the ON period before the time delay occurs. This stored feedback signal is then used to control the switching device during the time delay period, ensuring continuous and stable power supply without waiting for real-time feedback, thereby maintaining current control precision without significantly increasing device complexity.
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
The apparatus maintains a constant current supply to LEDs even with time delays in feedback control, preventing excessive power supply and reducing magnetic flux resonance, thereby ensuring reliable operation and improved brightness control.
Implementation Method 1
which isolates between the primary and the secondary through a transformer
Implementation Method 2
a delay of the feedback control is generated by a photocoupler or a control circuit used
Data Source
AI summary
A constant current power supply apparatus is provided which can drive a load with a constant current, even if the circuit configuration is such that a time delay is generated in the feedback control of a converter, or the like. An FB period restricting circuit including an ON generation circuit, OR circuit, inverter, and PMOS restricts the period during which an FB signal is fed back, to the logical sum of the ON period of an SW signal for driving an LED array on and a replenishment period generated by the OR circuit based on the SW signal. An FB signal generation circuit including a differential amplifier, NMOS, reference voltage, capacitor, and shunt regulator generates, in the replenishment period other than the ON period of the SW signal, an FB signal corresponding to an output current having flown through the LED array during the ON period of the SW signal.