Review, teardown, and testing of HLG-185H-24A Mean Well power supply

General Description

Brief Specification

The HLG-185H-24A is a power supply unit with a DC output of 24 volts and up to 7.8 amps. According to the specification, this unit has an extended input voltage range for AC power, from 90 to 305V. When the AC input voltage drops from 100 to 90V, the support load power linearly decreases from 100% to 80% of the nominal rating.

This power supply can also operate on DC power within a range of 127 to 431V.

The unit's dimensions are 9 x 2.7 x 1.5 inches (228 x 68 x 38.8 mm). The casing is made of aluminum profile, sealed with compound material, and closed with lids on both ends. The unit is designed for operation without forced cooling.

The power supply features adjustments for output voltage and current, protected by rubber-like material caps. The output voltage can be set between 22-25V and the output current between 3.9-7.8A. No indicator elements are present. The unit includes active PFC circuitry with a power factor of at least 0.98 at 115 VAC and an efficiency of approximately 93.5%. It has thermal, overload, and output overvoltage protection.

Test Conditions

Most tests were conducted using Test Circuit 1 (see appendix) at 80°F (27°C), 70% humidity, and 29.8 inHg pressure.

Unless specified, measurements were taken without pre-warming the unit in a short-term load operation mode. Input voltage was 115V AC, with 7.8A considered 100% current.

The following values were used to define the load levels:

Static Load Output Voltage

The output voltage stability is noteworthy; with changing load levels, the output voltage variation did not exceed 0.34%.

Power-On Characteristics

100% Load Startup

Before testing, the unit was turned off for at least 5 minutes with a 100% load connected.

The 100% load startup oscillogram is shown below (Channel 1: output voltage, Channel 2: input current):

Two phases of the startup process can be identified on the oscillogram:

1. Input current spike for charging input capacitors upon connection to power, with an amplitude up to 5-6A, lasting about half a cycle of the input voltage (8 ms), with a trapezoidal current waveform.

2. (Output Voltage Rise Time) Output voltage ramps up in 11 ms.

(Turn-On Delay Time) The entire process from power-on to operating state takes just 20 ms.

(Output Voltage Overshoot) The startup process is aperiodic with no overshoot.

0% Load Startup

Before testing, the unit was turned off for at least 5 minutes with a 100% load connected. Then the load was disconnected, and power was turned on.

The 0% load startup oscillogram is shown below:

Two phases of the startup process can be identified from the oscillogram:

1. Input current spike for charging input capacitors upon connection to power, with an amplitude up to 5A, lasting about one cycle of the input voltage (14 ms), with a trapezoidal waveform.

2. (Output Voltage Rise Time) Converter starts, output voltage ramps up, and reaches operating state in 9 ms.

(Turn-On Delay Time) The entire process from power-on to operating state takes 23 ms.

(Output Voltage Overshoot) The startup process is aperiodic with no overshoot.

Power-Off Characteristics

The power supply was turned off at 100% load, with the AC voltage at its nominal value at the time of shutdown. The oscillogram for the process is shown below:

Two phases of the shutdown process can be identified from the oscillogram:

1. (Shut Down Hold-Up Time) The power supply continues to operate on the input capacitors' charge until the voltage drops to a critical level, preventing the output from maintaining nominal voltage. This phase lasts 18 ms.

2. (Output Voltage Fall Time) Output voltage decreases, the converter stops, and voltage drop accelerates. This phase lasts 21 ms.

(Output Voltage Undershoot) The shutdown process is aperiodic, with no undershoot.

The current amplitude at 100% load just before shutdown was 2.5A.

Output Voltage Ripple

100% Load

At 100% load, low-frequency ripple appears at twice the grid frequency, with an amplitude of about 7 mV. The current waveform (Channel 2) shows an amplitude of approximately 2.5A.

Switching frequency ripple at around 60 kHz is minimal at 100% load and hard to measure, with switching noise of 120 mVp-p.

75% Load

At 75% load, low-frequency ripple has an amplitude of approximately 7 mV at twice the grid frequency, following a sinusoidal shape. Input current amplitude is about 2A, with a sin-like waveform.

At 75% load, converter frequency ripple remains low and hard to detect, with switching noise of 120 mVp-p.

50% Load

At 50% load, low-frequency ripple amplitude is about 7 mV. Input current amplitude is about 1.4A, with a near-sinusoidal waveform.

At 50% load, converter frequency ripple remains low and hard to detect, with switching noise around 100 mVp-p.

10% Load

At 10% load, low-frequency ripple amplitude is about 20 mV, with a waveform distantly resembling a sinusoid. Input current amplitude is about 0.3A, but with significant waveform distortion.

At 10% load, converter frequency ripple remains low and hard to detect, with switching noise around 90 mVp-p.

0% Load

The no-load input current measured with a multimeter was 47 mA.

(Power Consumption) The current in this mode is predominantly reactive, making power measurement with standard desktop instruments challenging.

At 0% load, low-frequency ripple resembles a declining sawtooth, with an amplitude of around 50 mVp-p. Input current becomes noise-like with a peak amplitude of 0.1A.

At 0% load, converter frequency ripple is masked by noise around 130 mVp-p.

Dynamic Characteristics

For dynamic characteristics evaluation, a mode switching between 50% and 100% load was used. The oscillogram of the process is shown below:

The power supply's response to a step change in load shows slight overshoot (about 45 mV) and a response to load changes of approximately 130 mV p-p. Channel 2 shows input current during these changes.

Overload Protection

The manufacturer states that the protection type is Constant current limiting, recovers automatically after fault condition is removed, and this was confirmed during testing. In the event of an overload or short across the output terminals, the power supply enters current-limiting mode, automatically restoring normal operation after the overload is cleared.

The factory-set current limit is 8.4A.

Input Circuit Safety Assessment

(Input Discharge) For safety evaluation, the input circuit discharge time constant was measured upon disconnection from the power line and found to be 0.407 s. At 120V operation, it takes about 0.65 s for the input to discharge to safe levels (<42V).

Note: This result applies only to the tested unit, obtained solely for research purposes, and should not be considered as a safety guarantee.

Leakage current via ground terminal: 24 µA.

Thermal Characteristics

When operating with no load, significant heating of components was not observed.

Thermograms were recorded at three power levels: 80%, 90%, and 100%. The hotspot of the unit is located on the primary side, but its temperature is only slightly above the average unit temperature, by around 1-2°F. At 80% load, the hotspot is 111.7°F (44.3°C, with a temperature rise of about 17° above ambient); at 90% load, 116.8°F (47.1°C, with a rise of about 20° above ambient); and at 100% load, it reaches 123.1°F (50.6°C, with a rise of around 24°).

80% Load

90% Load

100% Load

Conclusions

The HLG-185H-24A is a decent power supply for various applications, beyond LED power. First of all, it is safe, with minimal heating at full load and includes protection from overheating, overload, and overvoltage. Furthermore, it offers respectable electrical characteristics, with low noise and ripple and accurate output voltage regulation. The unit demonstrates good dynamic performance, with pulsating load response within ±0.2%.

The unit's design allows for surface mounting using its base for additional heat dissipation.

Unfortunately, the circuitry and internal structure cannot be examined without dismantling the unit.

Important: The results and conclusions apply solely to the tested unit, obtained for research purposes only, and should not be used to assess all units of this type.