Rev. D 06/15

7

PFS7323-7329

www.power.com

Figure 9.

(a) Frequency Variation over Line Half-Cycle as a Function of Input Voltage (b) Frequency Variation over Line Half-Cycle as a Function of Load.

0

45

90

135

180

120

230 VAC

180 VAC

135 VAC

115 VAC

Peak Load

90 VAC

110

100

90

80

70

60

50

40

30

20

10

Line Conduction Angle (°)

0

45

90

135

180

120

110

100

90

80

70

60

50

40

30

20

10

Line Conduction Angle (°)

100% Peak Load

75% Peak Load

VIN = 115 VAC

25% Peak Load

50% Peak Load

Expected Frequency

Range at Peak

Rated Load

Figure 10. V

OFF vs. VE and VOFF vs. Input Voltage.

and FEEDBACK pins are satisfied and the sensed VOLTAGE

MONITOR pin current is above I

UV+ ,the IC applies a ~6 mA

current sink through the VOLTAGE MONITOR pin and checks

that the status of the REFERENCE pin voltage is still in a valid

range. This checks to ensure that the FEEDBACK and

REFERENCE pins are not shorted together. In the event that

these pin voltage are shorted or the REFERENCE pin current is

no longer in the valid range, VOLTAGE MONITOR pin holds the

6 mA current sink indefinitely until the REFERENCE pin is in the

valid range. Figure 8 illustrates this sequence.

Timing Supervisor and Operating Frequency Range

Since the controller is expected to operate with a variable

switching frequency over the line frequency half-cycle, typically

spanning a range of 24 – 110 kHz, the controller also features a

timing supervisor function which monitors and limits the

maximum switch on-time and off-time as well as ensures a

minimum cycle off-time.

~5 V

VIN < ~140 VAC

VIN > ~170 VAC

~5 V

(Full Power)

~140 VAC

~170 VAC

~5 V

~1.25 V

~1.25 V

~0.8 V

VE

VIN

PI-6864-050313

Figure 9a shows the typical half-line frequency profile of the

device switching frequency as a function of input voltage at

peak load conditions. Figure 9b shows for a given line

condition the effect of EcoSmart™ to the switching frequency

as a function of load. The switching frequency is not a function

of boost choke inductance in CCM (continuous conduction

mode) operation.

EcoSmart

The HiperPFS-2 includes an EcoSmart mode wherein the

internal error signal (V

E) is used to detect the converter output

power. Since the internal error-signal is proportional to the

output power, this signal level is used to set the average

switching frequency as a function of output power. The off-time

integrator control reference (V

OFF) is controlled with respect to

the internal error-voltage level (output power) to allow the

converter to maintain output voltage regulation and relatively flat

conversion efficiency between 20% to 100% of rated load