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Key Technical Specifications
| Parameter | Specification |
| Nominal Output Voltage | 24 V DC |
| Output Voltage Trim Range | 21.6 V DC to 28 V DC |
| Rated Output Current | 5.0 A |
| Maximum Output Power | 120 W |
| Input Voltage Range | 85–132 V AC / 170–265 V AC (Auto-selectable), 47–63 Hz |
| Efficiency (Typical) | 85% at 100/230 V AC |
| Inrush Current (Cold Start) | 20 A at 100 V AC, 45 A at 230 V AC |
| Overcurrent Protection | Constant current limiting with auto-recovery |
| Overvoltage Protection | Output shutdown (requires manual AC power-cycle reset) |
| Isolation Voltage | Input to Output: 3.0 kV AC; Input to Ground: 2.0 kV AC |
| Operating Temperature | -10°C to +60°C (100% load to +50°C, derates to 60% load at +60°C) |
| Cooling Method | Free-air convection (no internal fan required) |
| Dimensions (W x H x D) | 60 mm x 97 mm x 110 mm |
| Weight | 540 g |
Product Introduction
The TDK-Lambda DLP120-24-1 is an industrial-grade, single-phase switch-mode DIN rail power supply engineered to provide clean, regulated 24 V DC power for automated control systems. Operating with an auto-selectable dual input range of 85–132 V AC and 170–265 V AC, this 120 W unit delivers up to 5 A of continuous current, making it a standard choice for driving PLCs, HMI panels, sensors, relays, and field instrumentation in harsh factory environments.
Featuring a convection-cooled IP20 metal housing, the DLP120-24-1 eliminates the reliability risks associated with moving fan parts while maintaining continuous 100% output up to 50°C. Built-in constant current overload limiting, overvoltage protection, and front-panel output voltage trimpots allow plant engineers to compensate for line drop over extended cable runs while securing downstream automation hardware against severe line surges.
Quality Control & SOP Inspection Guidelines
Every TDK-Lambda DLP120-24-1 supply is subjected to an exhaustive physical and electrical testing workflow before entering our dispatch inventory:
- Inbound Traceability & Visual Inspection:
- Serial number audit against OEM databases to ensure authentic TDK-Lambda origin.
- Inspection of the aluminum chassis and DIN rail mounting latch for structural deformation or corrosion.
- Visual check of screw terminal blocks for damaged threads, cross-threading, or stripped clamping screws.
- Electrical Insulation & Continuity Testing:
- 500 V DC isolation resistance test between output terminals and Earth Ground (> 100 M\Omega target).
- Ground continuity check to verify the metal enclosure bonds to the primary ground terminal.
- Bench Calibration & Functional Load Testing:
- Unit mounted on standard 35 mm DIN rail in a dedicated test station.
- Power applied at 115 V AC and 230 V AC to verify the auto-select circuit switches seamlessly.
- Voltage trimpot adjusted across full range (21.6 V to 28 V DC) to verify output stability. Set to nominal 24.0 V DC.
- Dynamic Overload & Thermal Monitoring:
- Loaded to 5.0 A continuous output on an electronic load bank for 24 hours at elevated ambient temperature.
- Overcurrent threshold checked to confirm constant-current shutdown engages correctly at overload limits.
- Thermal camera inspection of internal inductors and primary switching transistors to ensure no hot spots exist.
- Final ESD Packaging & Certification:
- Unit sealed in anti-static ESD shielding bag.
- Boxed in heavy-duty corrugated cartons with customized foam inserts. Test report attached.
DLP120-24-1
DLP120-24-1
Technical Pitfall & Field Survival Guide
❗ 1. Derating Curve Overlook (Thermal Traps):
The DLP120-24-1 delivers its full 120 W (5 A) rating up to an ambient operating temperature of +50°C. Above +50°C, the unit must be derated linearly down to 60% capacity (3 A) at +60°C. Installing this unit inside a sealed control box alongside hot drives or motor starters without adequate convection spacing will lead to thermal shutdown or premature capacitor dry-out. Always leave at least 15 mm of lateral clearance on both sides of the power supply on the DIN rail.
❗ 2. Overvoltage Protection (OVP) Power-Cycle Latch:
Unlike overcurrent protection (which auto-recovers when the load fault clears), the built-in Overvoltage Protection (OVP) circuit latches the unit off when triggered. If your supply output drops to 0 V DC and stays there despite normal AC line input, check if an inductive back-EMF spike from an unsuppressed solenoid valve or motor brake triggered the OVP. You must remove AC mains power for at least 60 seconds to reset the OVP circuit.
❗ 3. Terminal Block Over-Torquing:
Rushing an installation leads to stripped terminal block screws or cracked internal trace joints on the terminal PCB. Use a 0.6 mm x 3.5 mm flathead screwdriver and tighten the input/output screw terminals to a maximum torque of 0.5–0.6 N·m (4.4–5.3 lb·in). Loose wires create high-resistance contacts that melt terminal blocks under full 5 A loads.
❗ 4. Paralleling Units for Higher Current:
Do not connect multiple DLP120-24-1 units in parallel to double your output current unless using appropriate external isolation diodes. Standard units tied directly together will fight each other due to minute differences in factory trim voltage, causing one unit to carry the entire load, overheat, and trip while the secondary unit remains idle.
Troubleshooting Quick Reference
| Symptom | Possible Cause | Relevance to DLP120 | Quick Check Method | Recommendation |
| No DC output LED / 0V Output | Blown internal AC fuse or missing AC input line | ⚠️ Medium | Check AC input terminals with multimeter (85–132 V AC or 170–265 V AC) | If AC line voltage is present but internal LED remains dark, internal input fuse has blown due to severe surge. Replace unit. |
| DC output drops below 24V under load | Overcurrent protection active / load exceeds 5A | ✅ High | Measure output current with a clamp meter while load is connected | If load > 5.0 A, reduce system load or add an auxiliary power supply. |
| Output latches off at 0V continuously | OVP tripped by back-EMF or voltage spike | ✅ High | Measure DC output after fully cycling AC mains power OFF for 60 seconds | If unit resumes 24V output after power-cycle, install flyback diodes on field solenoids/relays to suppress inductive kickback. |
| Output voltage fluctuates/hums | Loose wiring or damaged output filter capacitors | ✅ High | Check DC ripple with an oscilloscope (spec is < 240 mV peak-to-peak) | Re-torque output terminals. If ripple exceeds spec, internal filter caps are degraded. Replace power supply. |
| Drive/PLC resets when heavy load starts | High inrush current pulling voltage low | ⚠️ Medium | Measure transient DC voltage drop during load startup using peak-hold multimeter | Adjust front panel V.ADJ pot slightly up to 24.5 V DC to compensate for line drop under startup loads. |
Note: If diagnostic checks do not resolve the issue, take photos of your terminal voltage readings and contact our engineering support team for live assistance.
Frequently Asked Questions (FAQ)
Q: Can I use the DLP120-24-1 on a 480 V AC industrial line?
A: No, not directly phase-to-phase. The maximum input voltage rating is 265 V AC. To operate this supply on a standard North American 480 V 3-phase system, you must power it off Line-to-Neutral (277 V AC is still too high—do not use) or install a control transformer to drop the voltage down to 120 V AC or 230 V AC single-phase.
Q: Is the output voltage adjustable on the ?
A: Yes. A small potentiometer located on the front faceplate allows output adjustment from approximately 21.6 V DC up to 28.0 V DC. This feature is useful for boosting output voltage slightly to overcome line resistance on long wire runs to remote remote I/O junction boxes.
Q: Does the require an external bridge jumper to select 115 V AC vs 230 V AC input?
A: No. The DLP120 series features an automatic input range selection circuit. It detects whether your input line is within 85–132 V AC or 170–265 V AC automatically, eliminating the need to set manual DIP switches or wire line select jumpers.
Q: How do New Surplus units compare to brand-new units straight from TDK-Lambda?
A: New Surplus units are original, unused OEM power supplies sourced from panel builders’ overstock, canceled plant integrations, or warehouse spare reserves. They provide the exact same performance and reliability as factory-new stock, but at a significantly lower cost. Every New Surplus unit in our stock undergoes 100% full-load bench testing before shipment and comes backed by our 1-year replacement warranty.
Q: What happens if the output is accidentally shorted out?
A: The includes built-in constant-current foldback protection. If a dead short occurs across the +24V and -24V terminals, the power supply restricts output current to prevent internal component failure. Once the short circuit is cleared, the unit automatically restores standard 24 V DC output voltage. Avoid leaving the unit in a dead-short condition for longer than 30 seconds to prevent thermal stress.
