NCP1219PRINTGEVB
http://onsemi.com
21
Input Voltage (Vac)
A
verage Ef
ficiency (%)
90
89
88
87
86
85
84
83
82
81
80
50
300
100
150
200
250
Figure 35. Average Efficiency vs. Line Voltage
The standby input power requirement is less than 1 W
over the range of input voltage. Figure 36 shows the standby
input power versus input voltage. Starting at low line, the
input power rises with increasing input voltage. At line
voltages less than 180 Vac, the controller operates in DSS
mode, because the forward auxiliary winding voltage is less
than that required to maintain V
CC
greater than V
CC(MIN)
.
A portion of the standby input power is due to the startup
circuit. As the input voltage increases, the auxiliary winding
begins to supply the controller and the startup circuit is no
longer active. A sudden drop in the standby input power is
observed when DSS is disabled. As the input voltage
continues to increase, so does the input power.
INPUT VOLTAGE (Vac)
DSS mode
Aux winding
mode
Figure 36. Standby Power versus Input Voltage (Forward Auxiliary Winding Connection)
1200
1100
1000
900
800
700
600
500
80
100
120
140
160
180
280
260
240
220
200
ST
ANDBY
POWER (mW)
