Data Sheet G14309EJ2V0DS00

13

µµµµPC1909

3.2 Steady Operation

The operating waveforms during steady operation are shown in Figure 3-2 below. Steady operation as used here refers

to the state in which the overcurrent and overvoltage latches are not working. The operations that occur during steady

operation are as follows.

<1>

When the converter is operating at the rated input and output, the FB voltage is between DTC1 and DTC2 (in

the T3 period in Figure 3-2).

•The FB voltage and CT triangle wave are compared by PWM comparator 1. OUT1 is high level when the FB

voltage is higher than the CT voltage.

•The FB voltage and level-shifted dCT triangle wave are compared by PWM comparator 2. OUT2 is high level

when the FB voltage is lower than the dCT voltage.

<2>

Because the input voltage becomes lower as the load of the converter is increased, there is a period when the

FB voltage rises and the OUT1 duty increases (the T4 period in Figure 3-2).

When the FB voltage is greater than the DTC1 voltage, OUT1 operates at the maximum duty determined by

DTC1. At this time also, OUT2 operates at the minimum duty determined by DTC1.

<3>

Because the input voltage becomes higher as the load of the converter is decreased, there is a period when

the FB voltage falls and the OUT1 duty decreases (the T5 period in Figure 3-2).

When the FB voltage is less than the DTC2 voltage, OUT2 operates at the maximum duty determined by DTC2.

Figure 3-2. Waveforms During Steady Operation

OUT1

DTC1

FB

DTC2

OUT2

CT

dCT

Vd

T4

T3

T5