Repeated pulse load

Typically a load current is not constant and varies with time. This power supply is designed to support loads with a higher short-term power demand (Extra Power). The short-term duration is hardware-controlled by an output power manager and is available repeatedly. If the Extra Power load lasts longer than the hardware controller allows, the output voltage drops. Extra Power is available again after the Extra Power recovery time has elapsed (see Output voltage over output current, typ.; bonus time over output power chapter).

To avoid this, the following conditions must be met:

• The power requirement of the pulse must be less than 150% of the rated output power.
• The duration of the pulse power must be shorter than the permitted extra power time. (see Output)
• The average (RMS) output current must be below the specified continuous output current.
  If the effective current is higher, the device responds with a thermal shutdown after a certain time. The maximum duty cycle curve (Fig. Repeated pulse loads, definitions) can be used to check whether the average output current is below the rated current.

Calculation:

Duty cycle = T_PEAK / (T_PEAK + T₀)

T₀ = (T_PEAK - (DutyCycle x T_PEAK)) / DutyCycle

Example:

A load is operated continuously with 120 W (= 50% of the nominal output load).
From time to time a peak power of 360 W (= 150% of the nominal output load) is required for 1 second.

• The question is: how often can this impulse be supplied without overloading the power supply?
• Draw a vertical line at P_PEAK = 150% and a horizontal line where the vertical line crosses the curve P₀ = 50%. Read the maximum duty cycle from the duty cycle axis (= 0.37)
• Calculate the required pause length T₀ (base load):
• Result: Required pause length = 1.7 s
• Max. repetition rate = pulse + pause length = 2.7 s

T₀ = (T_PEAK - (DutyCycle x T_PEAK)) / DutyCycle = (1 s - (0.37 x 1 s)) / 0.37 = 1.7 s

Further examples of pulse load tolerance