TDK-Lambda DSP10-12 DIN Rail Ultra-Slim Power Supply

DSP = DIN rail ultra-slim AC-DC power supply; 10 = rated power 10W; 12 = fixed 12VDC output; full part number DSP10-12, commonly known in industry as DSP10-12VDC

1. Core Electrical Specifications

2. Mechanical & Environmental

Mounting: Standard 35mm DIN rail

Dimensions: W18 × H91 × D55.6 mm

Weight: Approx. 60g

Operating Temperature: -25℃ ~ +71℃; linear derating above 55℃ at 2.5%/℃

Storage Temperature: -40℃ ~ +85℃

3. Indicator LEDs

Green LED: Normal output power

Red LED: Output undervoltage / fault condition

4. Certifications & Application Scenarios

Certifications: UL508, UL60950-1, EN60950-1

Typical Applications: Building automation, access control, security alarm, fire protection systems, small sensors, PLC IO module power supply; ideal for tight space installation inside control cabinets

5. Model Selection & Replacement Information
6. Other models within the same series: DSP10-5 (5V/1.5A), DSP10-15 (15V/0.67A), DSP10-24 (24V/0.42A)
7. Domestic alternative references (DIN rail 10W 12V ClassII):

Meanwell DR-10-12 (same power rating, pay attention to insulation class difference)

Mornsun LI10-12B24

Difference Notes: DSP10-12 advantages: ultra-slim 18mm width, Class II double insulation, no PE ground required, preferred for building & fire protection projects; verify UL1310 Class2 certificate for domestic alternatives.

6. Troubleshooting Guidelines
7. Green LED off: Check AC/DC input connection; blown input fuse; primary-side internal damage
8. Red LED constantly on: Output overload / short circuit; load leakage; ageing output capacitor
9. Low output voltage: Load exceeds 0.83A; high-temperature derating; input voltage at lower limit
10. Intermittent power dropout: Loose input terminals; grid surge, small EMI filter recommended at front end
11. Important Notes

Output voltage fixed 12V, no trimming potentiometer, voltage cannot be fine-tuned

Class II power supply, floating casing; casing cannot be used as protective earth

Derating is mandatory under high-temperature environments; continuous full-power operation at 70℃ is prohibited

Factors Affecting Efficiency of TDK-Lambda DSP10-12

Stated typical efficiency 78% (test condition: 230VAC input, full load, 25℃ ambient). This value is not constant and is affected by the following 5 categories of factors.

1. Output Load Ratio (Most Critical Factor)

DSP10-12 is a low-power flyback switching power supply; internal control circuits consume static power.

Light load (<30% load, ＜3W): Fixed standby loss accounts for larger proportion; efficiency drops significantly. At no load, only the control IC is powered, efficiency is extremely low.

50%~100% load: Optimal efficiency range; the datasheet 78% typical value is measured under full load.

Overload (>100%): Triggers overcurrent foldback protection, losses surge and efficiency collapses.

2. Input Voltage (AC/DC Input)

Input range: 90~~264VAC / 120~~370VDC

High input voltage (around 230VAC): Higher efficiency, smaller primary current, lower conduction loss of transformer and switching MOSFET.

Low input voltage (90~110VAC): Primary current rises for same output power; copper loss and switching loss increase, efficiency decreases by 3%~6%.

Universal AC/DC input: if powered by DC source, the same rule applies – lower input voltage results in poorer efficiency.

3. Ambient Temperature & Heat Dissipation (Natural Convection Unit)

DSP10-12 fanless, pure natural convection cooling, linear derating 2.5%/℃ above 55℃:

Low temperature (~25℃): Component internal resistance is low, losses minimized; highest efficiency, benchmark test condition of datasheet.

High cabinet temperature (＞55℃): ESR of electrolytic capacitors rises, transformer copper loss increases. Not only output power needs derating, power conversion efficiency itself declines. Heat accumulation in sealed compact control cabinets further worsens performance.

Mounting method: Power supplies tightly arranged on both sides of DIN rail block airflow, equivalent ambient temperature rises and efficiency degrades.

4. AC Input Frequency

Rated range: 47~63Hz. Impact is minimal within this range; outside the range, switching timing and rectifier loss change and efficiency drops slightly.

5. Load Characteristics & Wiring Loss

Load type: Pure resistive load delivers best efficiency; capacitive impulse load & high-frequency pulsating load increase ripple current on output capacitors, heating from capacitor ESR rises and reduces overall efficiency.

Terminal wiring: Undersized wire gauge or poor terminal contact produces extra I²R loss, reducing total system efficiency (power supply conversion efficiency unchanged, but additional loss in power delivery path).

Supplement: Root Causes of Intrinsic Internal Loss

1. Switching loss & conduction loss of power MOSFET
2. Core loss + winding copper loss of high-frequency transformer
3. Heating caused by ESR of input/output electrolytic capacitors
4. Static power consumption of PWM control circuit and auxiliary power supply (dominant at light load)

Engineering Optimization Recommendations

1. Operate power supply within 50%~100% rated load as much as possible; avoid long-term light-load operation.
2. Prefer 220/230VAC power supply to reduce low-voltage operating conditions.
3. Reserve ventilation gaps in control cabinet, avoid dense stacking of multiple ultra-slim DIN rail power supplies; keep cabinet temperature ≤55℃.
4. Minimize long-distance and thin-gauge wiring on output side to reduce external line loss.

TDK-Lambda DSP10-12: Specific Impacts of Ambient Temperature on Efficiency

Baseline condition: datasheet typical efficiency 78%, 230VAC, full load, Ta=25℃. This is a fanless naturally cooled DIN rail power supply, power derating starts at 55℃ (derating slope: 2.5%/℃).

Distinguish two concepts: direct change of conversion efficiency with temperature + operating point shift caused by high-temperature derating which indirectly changes efficiency

1. At Component Level: Rising Temperature Directly Increases Internal Loss and Reduces Power Conversion Efficiency
2. Power Switching MOSFET

MOSFET on-resistance Rds(on) increases with temperature. Conduction loss I²R rises at same current, positive feedback heating, slightly reduces overall efficiency. This effect is more obvious for this low-power flyback PSU under high temperature & full load.

2. High-frequency Transformer

Winding copper resistance rises with temperature → higher copper loss;

Core loss slightly increases with temperature rise;

Combined effects heat the transformer and reduce power conversion efficiency.

3. Electrolytic Capacitors (Input & Output)

In low-temperature zone, capacitor equivalent series resistance (ESR) decreases with temperature rise. However, long-term continuous high temperature will gradually raise ESR with ageing.

Ripple current generates extra heating at high temperature, increasing reactive loss, lowering overall efficiency and accelerating capacitor ageing.

4. Rectifier Diode

Diode forward voltage slightly decreases as temperature rises (minor reduction in forward loss), but reverse leakage current increases and creates extra reverse loss. For this 10W low-power PSU, diode thermal effect on efficiency is weaker than MOSFET and transformer.

✅ Summary: Conversion efficiency of the power supply peaks around 25℃. As temperature continuously rises, native conversion efficiency slowly decreases. However, the efficiency drop purely from temperature is moderate. The main engineering concern is the power derating mechanism.

2. High-temperature Derating: Reduces Maximum Permissible Output Power and Indirectly Changes Load Ratio, Further Impacting Efficiency

Derating rule for DSP10-12:

Ambient Temperature Ta ≤ 55℃: Full 10W output available, power supply works in optimal load zone with high efficiency;

Ta＞55℃: Output power derates linearly at 2.5% / ℃.

Example: Ta=65℃, 10℃ above 55℃, maximum allowable output power = 10W × (1−2.5%×10) = 7.5W.

Key engineering consequences:

1. If fixed load =8W: under 55℃, load ratio is 80% (high-efficiency zone); when cabinet temperature reaches 65℃, max power limited to7.5W. 8W load becomes overload and triggers foldback protection, losses surge and efficiency plummets.
2. Under high temperature, load power must be reduced to stay within PSU rating. Reduced load ratio enters light-load region, light load itself degrades conversion efficiency, creating superimposed negative effects.

Simple summary: High temperature increases component losses on one hand; on the other hand, maximum available power of PSU drops, making load easily deviate from optimal working zone → dual deterioration of efficiency.

3. Low-temperature Environment (-25℃ ~ 25℃)

Lower temperature reduces MOS Rds(on) and copper wire resistance, component losses decrease; theoretical conversion efficiency slightly higher than room temperature.

Negative effect: ESR of electrolytic capacitors rises significantly at low temperature, increasing capacitor loss and partially offsetting efficiency gain. Inrush charging current increases during cold start, while steady-state efficiency is generally better than high-temperature operation.

-25℃ is the minimum rated operating temperature; capacitor performance degrades rapidly below this threshold.

4. Secondary Effect from Mounting / Cabinet Temperature (Easily Overlooked)

DSP10-12 is only 18mm wide. When multiple units are mounted side-by-side with no gap:

Mutual radiant heat transfer between adjacent power supplies → component case temperature marked ambient temperature Ta. Even if cabinet measured temperature is 52℃, tightly stacked installation may push PSU case temperature above 55℃ and trigger derating in advance, reducing efficiency prematurely.

5. Quantitative Engineering Trend (Qualitative, derived from datasheet characteristics)

Ta=25℃, full load, 230VAC: η≈78%

Ta=55℃, full load, 230VAC: efficiency drops approx. 1~2 percentage points

Ta=70℃ (maximum allowable operating point, power heavily derated): native efficiency drops another 1~3 percentage points, full-load operation prohibited.

Note: Datasheet does not contain full temperature-efficiency curve. Values above are typical variation range for low-power Class II DIN rail flyback power supplies, not precise fixed figures.

6. Engineering Application Recommendations
7. Control cabinet ambient temperature ≤55℃ to maintain full power output and high conversion efficiency.
8. Reserve gaps between adjacent DSP10 units in multi-device installation to avoid thermal coupling and prevent case temperature overshoot.
9. Derate and calculate maximum load for high-temperature cabinet design; do not design load directly based on rated 10W.
10. Do not mount power supply close to heat-generating components (contactors, high-wattage power supplies). Local hotspots greatly degrade efficiency and shorten service life.

TDK-Lambda DSP Series: Complete List of Models Related to DSP10-12

DSP Series: Ultra-slim DIN rail, Class II double insulation, natural-cooled AC-DC power supplies; DSP10 =10W sub-series, higher power models DSP30/60/100 also available; DSP10 fixed non-adjustable output; DSP30/60/100 with output voltage trim capability

✅ DSP10 (10W, 18mm width, subseries of your reference model)

✅ DSP30 (30W, width 36mm)

✅ DSP60 (60W, width 54mm)

✅ DSP100 (100W, width72mm)

General Characteristics for full DSP series

1. Input: 90~~264VAC /120~~370VDC, universal AC/DC input
2. Insulation: Class II double insulation, Protective Earth (PE) not required
3. Cooling: Pure natural convection, fanless
4. Derating: Linear derating at 2.5%/℃ when ambient temperature＞55℃
5. Mounting: Standard 35mm DIN rail

Important Engineering Remarks

1. DSP series status: NRND (Not Recommended for New Design). TDK recommends new-generation DRL series as replacement: DRL10-xx, DRL30-xx, DRL60-xx, DRL100-xx. Pin and mounting footprint compatible but parameters not fully equivalent; use DRL series preferentially for new projects.
2. DSP10 (10W) without trimming potentiometer; DSP30/60/100 equipped with output trim pot.
3. All models in series built-in: overcurrent, foldback short-circuit, overvoltage protection.

Other TDK-Lambda DIN Rail Series for Reference (Not DSP family)

DRL series (new replacement for DSP), DR series, DRB series, DIN rail AC-DC power supplies.