Contents
When does a power supply limit the current?
However, limiting the input power does not limit the output current of a supply. When the input power is held constant in an overload fault, as the output voltage drops, the output current rises (P=V*I).
What happens when you run power supply 20% beyond rated output?
As the graph further shows, when operating the power supply 20% beyond the rated load of 200 W, the efficiency drops a full percentage point below its 91% specification. This results in a 30% increase in power dissipation. Load regulation is another problematic spec when operating outside the rated output current.
What does the full load of a power supply mean?
The full load of a power supply refers to the maximum operation ratings of the power supply. If it is supplying the rated current (same as maximum current) at the rated voltage, then the load that is connected is the full load.
Which is the ideal voltage for overload fault protection?
Fig. 1 shows the ideal output voltage versus current for both constant power and current limits. In both cases, the overload fault protection is set to occur at 120 percent of the maximum rated load. In a system with power limit, the output current rises as the inverse of the voltage as the load is increased.
How does a 5V power supply affect the current?
An internal 5V source charges C11 through R10 and R8. As the bias voltage falls, the resistor divider of R7 and R11 turns on Q1 and over-rides the internal 5V source, decreasing the switching frequency. The bias diode (D4) must now be a dual, series-connected diode, so that R7 and R11 do not divert current from the controller during startup.
How much voltage do you need for a limiting circuit?
Generally your current limiting circuit will require a bit of voltage “headroom” to operate in. That means you’ll need an unregulated PSU of > 5 V and regulate it down to 5 V while monitoring the current.
How much current does a 5V circuit draw?
The circuit draws about 200uA from the 5V supply, in addition to the load current of 0~100uA. The Ohm’s Law police will come after you if you attempt to regulate both voltage and current into a fixed load.