I was of late tasked amongst doing a presentation on the advantages of ability supplies incorporating Digital Control to ability non-linear loads, thus I thought I would portion the content amongst you.
A non-linear charge is i that does non acquit similar an ideal resistor, inward that the electrical flow drawn from the ability provide is non proportional to voltage and/or the initial currents are frequently much higher than the rating of the ability supply.
These loads tin crusade problems for ability supplies, but are genuinely acquaint inward many applications:
Large switched capacitor banks
Point of Load DC-DC converters
Thermal printers
DC motors
The master copy number from a ability supply’s indicate of persuasion is that the charge tin activate the internal over-current protection. Over-current protection (OCP) is an essential characteristic for a ability supply, but the ability provide is commonly expected to recover automatically amongst no manual intervention.
So to get-go with, let’s facial expression at the types of OCP. There are several basic methods used:
Constant Current
Fold Back
Fold Forward
Hiccup
Constant Current
When an overload status occurs, the output voltage falls but the output electrical flow remains at a fixed level. This type of protection is non good suited for delivering peak loads equally it tin Pb to the ability provide latching.
Fold back
When the electrical flow drawn reaches the OCP limit, the voltage falls, but this fourth dimension the electrical flow decreases equally the overload gets heavier. Again this type of protection is non good suited for delivering peak loads equally it tin consequence inward the ability provide latching.
Fold forward
When the electrical flow drawn reaches the OCP limit, the voltage falls. This fourth dimension the output electrical flow increases to a laid maximum at curt circuit.
Fold frontwards is good suited for powering upward motors, but requires heavier arrangement charge cabling to handgrip the additional overload current.
Hiccup
At the OCP limit, the ability provide turns off for a curt interval together with and thus automatically tries to restart. Hiccup agency reduces the demand for heavy cabling or pcb traces, together with this type of protection tin move modified to deliver a peak load.
With traditional Analog Control though, the OCP points together with recovery timing are fixed.
With Digital Control nosotros tin operate software settings to adjust the limits together with timing; for illustration nosotros tin set:
10s for an initial overload condition
60ms for heavy overloads
5ms for a curt circuit status amongst recovery times or 1 to two seconds
Let’s accept an application illustration of a discharged capacitor depository fiscal establishment beingness switched onto an operating ability provide amongst Analog control.
The lower (blue) line is the ability provide current; restarting twice amongst the ability provide electrical flow boundary laid at but about 60A.
The hand (gold) line shows the output eventually recovering, but tolerances amongst the hiccup agency timing could stimulate got prevented a total recovery.
This fourth dimension the same discharged capacitor depository fiscal establishment is switched into a TDK-Lambda CFE400M provide incorporating digital control.
The bluish line is the current, gilded line is the output voltage
Using Digital Control, nosotros tin laid the thresholds together with timing accurately.
50A for 1.5ms (The curt circuit condition)
30A for 50ms (The over electrical flow condition)
Notice that at that spot are no multiple attempts to recover later on the capacitor depository fiscal establishment is applied to the ability supply.
To summarize:
Digital command tin allow for precise together with repeatable electrical flow limiting using charge dependant timing. We are non restricted to the value of a timing capacitor which tin alter due to:
a) Batch tolerances
b) Aging of the capacitor
c) Capacitor values changing amongst temperature
Digital command allows for slow tailoring for dissimilar applications amongst no physical modification of the ability provide is needed. All changes are handled amongst software programming!
Power Guy
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