Horticultural Lighting: Powering LED Grow Lights with Constant Voltage Drivers

Horticultural lighting has grown from a niche research tool into a mainstream market, and a significant segment of it runs on constant voltage technology. Indoor farms, vertical farms, greenhouses, and home growers use LED strips and modules to provide the light that plants need for photosynthesis, and these products are powered by the same 24V constant voltage drivers that serve commercial lighting. But horticulture has specific requirements — light spectrum, photoperiod, humidity, and thermal management — that influence driver selection and installation in ways that general commercial lighting does not.

The first consideration is the light itself. Plants respond to specific wavelengths of light, primarily in the blue (400-500nm) and red (600-700nm) ranges, with far-red (700-750nm) playing a role in photoperiodic responses. LED horticultural products deliver these spectra through discrete LED chips — deep red (660nm), royal blue (450nm), and white — arranged on strips or boards. These products are commonly designed for constant voltage operation at 24V, with the LEDs and current-limiting resistors or constant current regulators integrated into the product. The driver's job is the same as in general lighting: maintain a stable 24V bus. The difference is that horticultural fixtures may draw more current per meter and may be configured in longer runs, making voltage drop management more critical.

Light intensity is measured in PPFD (photosynthetic photon flux density, in micromoles per square meter per second), and achieving the PPFD targets for different crops — 200 to 400 for leafy greens, 600 to 900 for fruiting crops, up to 1,200 for high-light crops like tomatoes and cannabis — requires significant installed wattage. A vertical farm shelf might use 100 to 200W of LED strips per shelf, powered by one or more 100W or 150W drivers. The load calculation follows the same rules as general lighting, but the density of the load in a confined rack means the drivers must be mounted where they can dissipate heat — typically on the rack frame outside the canopy area, or at the end of the shelf away from the plants.

Photoperiod control is essential in horticulture. Crops require specific light/dark cycles, and the lighting must be switched on and off reliably, often multiple times per day. The simplest control is a time clock or relay switching the mains supply to the driver — exactly the architecture described for simple smart lighting, and fully compatible with non-dimmable constant voltage drivers. Some operations use dimming for sunrise/sunset simulation or for adjusting light intensity during plant hardening, which requires dimmable drivers; but a large share of commercial horticulture operates at fixed intensity with strict on/off schedules, where non-dimmable drivers are ideal. The relay or contactor must be rated for the driver inrush current, as discussed in multi-driver circuit design.

Humidity is the dominant environmental challenge. Indoor farms and greenhouses are humid by design — 60 to 80 percent relative humidity is common, and hydroponic systems create splashing and mist. The driver must be protected against this moisture: an IP65 or IP67 rated driver is recommended inside the growing area, while drivers mounted outside in a dry electrical room can be standard IP20. Connections between the driver and the strips must also be moisture-protected — sealed connectors or IP-rated junction boxes. In greenhouses, drivers may also face direct sunlight and day-night temperature swings, so the temperature rating and enclosure UV stability should be considered.

Thermal interaction between the driver and the growing environment deserves attention. In an indoor farm, the heat from the drivers adds to the cooling load of the facility — every watt of driver loss must be removed by HVAC, exactly as in an air-conditioned office. High-efficiency drivers (above 88 percent) reduce this load directly. Conversely, the drivers must not overheat in the growing environment: a vertical farm shelf with dense LED coverage may have an ambient temperature near the driver of 30 to 40 degrees, within the Ta rating of most drivers, but the driver should be mounted with clearance and airflow. Some growers mount drivers outside the rack on a ventilated panel to keep them cool, which extends their lifetime.

The final consideration is spectrum stability over time. Plants respond to the exact spectrum delivered, and any drift in LED output — caused by current variation or temperature — shifts the spectrum. A constant voltage driver with low output ripple and tight regulation maintains stable current through the LEDs, preserving the spectrum. This is another reason to specify a quality driver: in horticulture, the driver's regulation quality directly affects the consistency of the light that the crop receives. For commercial growers, the driver is not an accessory to the lighting system — it is the component that determines whether the light delivered to the crop remains within specification day after day, crop after crop.