An indoor LED lighting project starts with a simple question that has more than one answer: is the supply a constant-voltage source feeding drivers, or a constant-current driver feeding the LEDs directly? The choice shapes the electrical design, the thermal design and the way the fixture is built.
This guide covers indoor LED lighting power supply design: how constant-voltage and constant-current architectures differ, how to size voltage and current for an LED load, what the enclosure does to the thermal case, how dimming interacts with the supply, and the criteria an OEM should apply when selecting a supply for a lighting product.
Constant Voltage and Constant Current: Two Architectures
LED lighting uses two power architectures, and the difference matters more than the name suggests.
Constant voltage (CV). The supply holds a fixed output voltage, and the current is decided by the load. LED strip, signage modules and panels with built-in driver circuitry are typical CV loads, because each element regulates its own current from a fixed rail.
Constant current (CC). The supply holds a fixed output current, and the voltage settles wherever the LED string requires. Luminaire-integrated designs that drive an LED string directly are CC loads, because the LED array’s forward voltage varies with temperature and current.
Some products combine the two: a constant-voltage supply feeding a separate driver, or a multi-stage design where a CV front end feeds CC stages. What matters for the OEM is knowing which party regulates the current — the supply, the fixture, or the LED module itself.
YHYadapter product positioning: YHYadapter provides regulated constant-voltage (CV) AC/DC power adapters for LED systems where a CV supply is the design choice — for example LED strip, signage and panel lighting with external or integrated drivers. Constant-current drivers for luminaire-integrated designs are supplied by dedicated lighting driver manufacturers.
Sizing Voltage and Current for the LED Load
Sizing an indoor LED supply is a matter of establishing the load’s real range rather than a single figure.
- Forward voltage range. An LED’s forward voltage falls as it warms, and the string voltage follows. A CC driver’s output voltage window has to cover the string at its coldest and its warmest.
- Current and dimming margin. The rated current sets the light output, and dimming may be implemented by reducing current, by pulse-width control, or by a separate control signal. Which one it is decides what the supply has to support.
- Start-up and inrush. LED modules and their input capacitors draw a brief current at power-up, and the supply must start into that load.
- Tolerance over life. The current the fixture needs can shift with ageing and with the driver’s own tolerance, so the sizing margin is a design choice, not an overhead.
Thermal Design Inside a Luminaire
An LED supply inside a luminaire lives in an enclosure that is warm by design: the LEDs themselves are a heat source, and the enclosure retains what they produce.
What shapes the thermal case:
- The enclosure’s ability to move heat to its surface, and from there to the room
- The placement of the supply relative to the LED array and its heat sink
- Whether the supply is inside the luminaire or mounted remotely, which changes the ambient it sees
- Continuous operation, since indoor lighting often runs for long hours
The practical consequence is that the supply’s derating position should be evaluated against the ambient inside the fixture, not the room. A supply selected for the room temperature may be operating outside its comfortable range inside a closed luminaire.
Dimming and Control Compatibility
Dimming is where the lighting design and the power design meet.
- Constant-voltage loads commonly dim by controlling the rail: mains-side phase dimming, or a low-voltage dimming signal interpreted by the LED module.
- Constant-current drivers commonly dim by reducing output current, or by pulse-width modulating it, with the control coming from a separate signal.
- Control interfaces differ in how they are wired and in what the driver or module expects, so the supply and the control method have to be chosen together.
The question to settle early is who interprets the dimming command — the supply, the module, or a separate controller — because it determines the compatibility that matters.
Reliability Over a Long Duty Cycle
Indoor lighting is often on for long hours, and continuous operation changes the reliability picture.
- Components accumulate operating hours quickly, so derating and thermal design carry more weight
- The steady-state temperature matters more than a short peak, because the load is continuous
- Protection behaviour is a lighting concern as well as a power concern, since an unexpected shutdown is visible to the user
- Service access to the supply affects the cost of a repair, and lighting fixtures are often installed where access is awkward
Specifying for the continuous position, rather than for a peak that may never occur, is what keeps a lighting installation dependable.
Selection Criteria for an Indoor LED Supply
Bringing the threads together, the specification for an indoor LED supply typically records:
- The architecture: whether the supply provides a constant voltage rail or a constant current
- The output voltage and current, together with the tolerance the load accepts
- The load’s range, including start-up behaviour and how it changes over life
- The ambient inside the fixture, and the supply’s derating position at that ambient
- The dimming or control method, and who interprets it
- The connector, cable and mounting arrangements
- The target markets and applicable requirements for the product
Certification availability for a given supply is by model and depends on the model and the target market.
Frequently Asked Questions
Do I need a constant-voltage supply or a constant-current driver for indoor LED lighting?
It depends on where the current is regulated. LED strip and modules that regulate their own current use a constant-voltage supply; a luminaire that drives an LED string directly uses a constant-current driver.
How much margin should an LED supply have?
Enough to cover the load’s real range — the string voltage at its coldest and its warmest, the start-up current, and the drift over life. A margin based on the nominal figure alone is not a specification.
Why does the enclosure change the supply requirement?
Because the LEDs are a heat source and the enclosure retains what they produce. The ambient inside the fixture can be well above the room temperature, so the derating position is evaluated against the internal ambient.
Can any LED supply be dimmed?
Dimming depends on how it is implemented and who interprets the command. Constant-voltage loads often dim by controlling the rail, while constant-current drivers commonly reduce or pulse the output current. The supply and the control method are chosen together.
Is certification the same for every LED power product?
No. Certification availability is by model and depends on the model and the target market, so the applicable requirements are confirmed for the specific product and destination.