LED | PartQuest™ Explore

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Member of the PartQuest Explore Development Team. Focused on modeling and simulation of analog, mixed-signal and multi-discipline systems covering a broad range of applications, including power electronics, controls and mechatronic systems.

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Transient Stability Testing of Transmission Line Fed LED Driver

Designer19

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12 years 2 months

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Member of the PartQuest Explore Development Team. Focused on modeling and simulation of analog, mixed-signal and multi-discipline systems covering a broad range of applications, including power electronics, controls and mechatronic systems.

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TDFS Impedance Stability of Transmission Line Fed LED Driver - Switching

Designer19

Member for

12 years 2 months

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Member of the PartQuest Explore Development Team. Focused on modeling and simulation of analog, mixed-signal and multi-discipline systems covering a broad range of applications, including power electronics, controls and mechatronic systems.

Description

This example demonstrates the use of the TDFS method (Time Domain Frequency Sweep) to measure impedance stability ratio. The system is a switching DC/DC step-down power converter used for LED lighting, supplied by a battery through a long power cable.The TDFS impedance stability measurement model applies a 0.2A sinusoidal stimulus current at the point where the cable connects to the converter. The voltage at that point, as well as the stimulus current splits (toward the source and the load) are measured, and the associated source and load impedances vs. frequency are computed.The ratio of the source to load impedance is the impedance stability ratio (Tm). Similar to the open-loop frequency response requirement for closed-loop stability, Tm must not have magnitude = 1.0 at phase = 180 degrees, at any frequency.For this system, with a cable length of 400 meters and 8 AWG wire, the results show that the impedance ratio magnitude (green waveform) reaches unity (0 dB) at close to 2 kHz, where the phase (light blue waveform) is approximately 165 degress. This implies a "phase margin" of only 15 degrees, For a longer cable, this margin is further reduced. As shown in the companion example, "Transmission Line Fed LED Driver - Switching", for the cable length = 800 meters the system is unstable.This instability is the result of the "source" impedance (which includes the cable) variation over frequency, interacting with the varying load impedance. Note that at low frequency, the load effectively has a negative impedance, due to the constant power nature of the DC to DC converter.

LED Dimmer Circuit using 555 Timer

Designer19

Member for

12 years 2 months

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Member of the PartQuest Explore Development Team. Focused on modeling and simulation of analog, mixed-signal and multi-discipline systems covering a broad range of applications, including power electronics, controls and mechatronic systems.

Description

This LED Dimmer Circuit uses a 555 Timer to control the PWM duty cycle of the current drive. Rather than apply proportional but continuous current to the LED for dimming, which can cause color shifts, modulating the duty cycle allows the LED to operate at its nominal current during the “ON” portion of the cycle. Because the frequency response of human vision is limited, using a PWM frequency of 250 Hz avoids the perception of flicker for the observer.

The LED model has an internal monitor for the "perceived" light output (blue waveform), which is a low-pass filtered version of the instantaneous light output. The filter pole frequency is set to 15 Hz to represent the bandwidth of the human eye. The value of the dimmer setting (green waveform) is increased from 10% to 90% at time 100msec. The LED current pulses (red waveform) are shown before and after the duty-cycle transition.

Part of this design is based on a dimmer schematic found on-line:

<a href="http://www.555-timer-circuits.com/led-dimmer.html">http://www.555-timer-circuits.com/led-dimmer.html</a>

That original circuit is actually incorrect, one of the&nbsp;diodes connected to pin 7 on the 555-Timer needs to be reversed. There was a comment from a reader who said he built the circuit as shown and it didn’t work. This is a good example of the value of simulating circuits before building hardware!

Copy of Transient Stability Testing of Transmission Line Fed LED Driver - on Thu, 01/22/2026 - 14:29

Designer264735

Member for

6 days 10 hours

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Welcome to the community!!

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Copy of Slayer circuit Tesla coil - on Tue, 01/20/2026 - 07:53

Designer264705

Member for

1 week 1 day

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Welcome to the community!!

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Copy of Transient Stability Testing of Transmission Line Fed LED Driver - on Fri, 11/28/2025 - 14:51

Designer249130

Member for

2 years 4 months

34

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Description

LED Dimmer Circuit using 555 Timer

Designer263365

Member for

5 months

71

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Welcome to the community!!

Description

This LED Dimmer Circuit uses a 555 Timer to control the PWM duty cycle of the current drive. Rather than apply proportional but continuous current to the LED for dimming, which can cause color shifts, modulating the duty cycle allows the LED to operate at its nominal current during the “ON” portion of the cycle. Because the frequency response of human vision is limited, using a PWM frequency of 250 Hz avoids the perception of flicker for the observer.The LED model has an internal monitor for the "perceived" light output (blue waveform), which is a low-pass filtered version of the instantaneous light output. The filter pole frequency is set to 15 Hz to represent the bandwidth of the human eye. The value of the dimmer setting (green waveform) is increased from 10% to 90% at time 100msec. The LED current pulses (red waveform) are shown before and after the duty-cycle transition.Part of this design is based on a dimmer schematic found on-line:<a href="http://www.555-timer-circuits.com/led-dimmer.html">http://www.555-timer-circuits.com/led-dimmer.html</a>That original circuit is actually incorrect, one of the&nbsp;diodes connected to pin 7 on the 555-Timer needs to be reversed. There was a comment from a reader who said he built the circuit as shown and it didn’t work. This is a good example of the value of simulating circuits before building hardware!

Copy of Analog LED Driver with Thermal Protection using FloTHERM Netlist - on Thu, 10/09/2025 - 17:35

Designer248415

Member for

2 years 5 months

23

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4

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Description

This&nbsp;LED spotlight example demonstrates the value of simulating both the electrical and thermal&nbsp;aspects of power dissipating circuits together, simultaneously.In this design, a Vishay NTCLE100&nbsp;Thermistor is used in a detection circuit to monitor&nbsp;the enclosure temperature. It is used for&nbsp;thermal shut-down protection, to keep the enclosure temperature well below the "Tg" (glass transition temperature) of the spotlight's Nylon 6 polymer&nbsp;lens. This is particularly helpful when operating at higher&nbsp;external ambient temperatures.The "Thermals" (thermal dynamics) model was automatically generated from a full 3D-CFD analysis of the spotlight board layout and enclosure, using FloTHERM. The model is in the IEEE Standard VHDL-AMS format, so it can be directly imported into the SystemVision "1D" circuit and system simulation context. The ability to include an accurate model of the thermal environment is key to having&nbsp;"thermally-aware" circuit function design&nbsp;and board layout&nbsp;processes.

Copy of Analog LED Driver with Thermal Protection using FloTHERM Netlist - on Thu, 10/09/2025 - 15:23

Designer248415

Member for

2 years 5 months

23

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4

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Welcome to the community!!

Description

This&nbsp;LED spotlight example demonstrates the value of simulating both the electrical and thermal&nbsp;aspects of power dissipating circuits together, simultaneously.In this design, a Vishay NTCLE100&nbsp;Thermistor is used in a detection circuit to monitor&nbsp;the enclosure temperature. It is used for&nbsp;thermal shut-down protection, to keep the enclosure temperature well below the "Tg" (glass transition temperature) of the spotlight's Nylon 6 polymer&nbsp;lens. This is particularly helpful when operating at higher&nbsp;external ambient temperatures.The "Thermals" (thermal dynamics) model was automatically generated from a full 3D-CFD analysis of the spotlight board layout and enclosure, using FloTHERM. The model is in the IEEE Standard VHDL-AMS format, so it can be directly imported into the SystemVision "1D" circuit and system simulation context. The ability to include an accurate model of the thermal environment is key to having&nbsp;"thermally-aware" circuit function design&nbsp;and board layout&nbsp;processes.