Mean Well Switch-mode Power Supplies Manual

Where V_out is the output voltage and A_outis the output current. It is possible to adjust V_out. However, P_out must remain constant. Therefore, if V_outis increased, A_out must be decreased.

Example. A power supply has an output voltage of 5 volts and an output current of 10 amps. The maximum power output is 50 watts. The adjustable voltage range is 4.7 volts to 5.5 volts. If the output voltage is adjusted to 5.5 volts, the maximum output current can be calculated by

A_out = P_out/V_out.

i.e. A_out = 50 watts/5.5 volts = 9.09 amps.

The output voltage can also be adjusted lower than 5 volts. However, due to the design of the output circuit, exceeding a 10 amp output is not recommended.

Some multiple output power supplies have a Current Range that exceeds the Output Rated Current. The table below has some specifications for the D-60A (dual output) power supply.

Channel	Output Voltage	Output Rated Current	Output Current Range
1	5V	4A	0.3 ~ 6A
2	12V	3A	0.2 ~ 4A

Ch. 1 can output 6 amps, but the total power output cannot exceed 60 watts. For example, if Ch. 1 was operated at a 5.5 amp output, the Ch. 2 output current would have to be reduced to remain within the 60 watt limit.

The total output power for Ch. 1 would be: (5 volts)x(5.5 amps) = 27.5 watts.

This would leave 32.5 watts for Ch. 2.

The total current available left for Ch. 2 is: (32.5watts)/(12volts) = 2.7 amps.

2.2 Overcurrent (Overload) Protection

Mean Well Power Supplies are equipped with a protection circuit that will automatically engage when the output current and/or output power exceeds maximum values.

2.2.1 Types of Protection Circuits

a. Foldback Current Limiting:

The Foldback Current Limiting circuit is designed to linearly decrease both the voltage and current to a level that will prevent the power supply from being damaged during overcurrent / overload conditions.

b. Constant Current Limiting:

Constant Current Limiting allows the output current to remain stable, but reduces the output voltage to a level that permits the safe operation of the power supply.

c. Over Power Limiting:

Over Power Limiting linearly reduces the output voltage and simultaneously allows the output current to increase.

d. Foldback Current Shutdown:

The Foldback Current Shutdown circuit will shut off both the output voltage and output current.

e. Constant Current Shutdown:

Constant Current Shutdown will drop the output voltage down to a point where there would only be a minute flow of current.

Fig. 4 - Protection diagram
Fig. 4

2.2.2 Recovery Circuits

a. Automatic Recovery

Automatic Recovery senses the removal of an overcorrect (overload) condition and returns the power supply to normal operation.

b. Manual Recovery

Before proceeding with Manual Recovery, make sure that the overcurrent / overload condition is removed. Manual Recovery requires cycling the input power between off and on. A several second wait is necessary prior to re-applying the Input power.

2.2.3 Overcurrent / Overload Precautions

Protection and Recovery circuits are designed to prevent damage to the power supply during an Overcurrent / Overload situation. However, leaving the power supply overload (or shorted) for extensive periods of time is NOT recommended and may result in component damage.

2.3 Over Temperature Protection

Some power supplies have an excessive temperature shut down circuit. When power supply operating temperatures become too high the protection circuit will turn off the output. Some common causes of excessive temperature are Overcurrent / Overload, high ambient temperature, or a faulty cooling fan. Returning the power supply to normal operation will require removing the cause of the over temperature condition and allowing the power supply to cool down.

IMPORTANT NOTE

All information is based on the Mean Well Switching Power Supply User Manual - Version 1 and is provided in good faith, but without any warranty or guarantee as to fitness to purpose. It is solely left to the discretion of the user as to the suitability of the information for their application.

BACK
Input

FORWARD
Installation Wiring & Connections