Electronic Components Datasheet Search 

NCP1654BD133R2G Datasheet(PDF) 16 Page  ON Semiconductor 

NCP1654BD133R2G Datasheet(HTML) 16 Page  ON Semiconductor 
16 / 23 page NCP1654 http://onsemi.com 16 Input and output power (Pin and Pout) are derived in (Equation 15) when the circuit efficiency η is obtained or assumed. The variable Vac stands for the rms input voltage. Pin + Vac 2 Zin + 2pRCS @ (Vcontrol * VCONTROL(min)) @ VREF @ Vac 2 RMRSENSEVoutKBO (eq. 15) T (Vcontrol * VCONTROL(min))Vac Vout Pout + h Pin + h 2pRCS @ (Vcontrol * VCONTROL(min)) @ VREF @ Vac 2 RMRSENSEVoutKBO (eq. 16) T (Vcontrol * VCONTROL(min))Vac Vout Follower Boost The “Follower Boost” is an operation mode where the pre−converter output voltage stabilizes at a level that varies linearly versus the ac line amplitude. This technique aims at reducing the gap between the output and input voltages to optimize the boost efficiency and minimize the cost of the PFC stage (refer to MC33260 data sheet for more details at http://www.onsemi.com ). The NCP1654 operates in follower boost mode when Vcontrol is constant, i.e. Vcontrolraises to its maximum value VCONTROL(max). Re−formulate (Equation 16) to become (Equation 17) and (Equation 18) by replace Vcontrol by VCONTROL(max). If Vcontrol is constant based on (Equation 15), for a constant load or power demand the output voltage Vout of the converter is proportional to the rms input voltage Vac. It means the output voltage Vout becomes lower when the rms input voltage Vac becomes lower. On the other hand, the output voltage Vout becomes lower when the load or power demand becomes higher. Pout + h 2pRCS @ (VCONTROL(max) * VCONTROL(min)) @ VREF @ Vac 2 RMRSENSEVoutKBO (eq. 17) + h 2pRCS @ DVCONTROL @ VREF @ Vac 2 RMRSENSEVoutKBO Vout + h 2pRCS @ DVCONTROL @ VREF 2 RMRSENSEKBO @ Vac Pout (eq. 18) where VCONTROL(max) is the maximum control voltage. DVCONTROL is the gap between VCONTROL(max) and VCONTROL(min). It is illustrated in Figure 39. Figure 39. Follower Boost Characteristics Vout (Traditional Boost) Vout (Follower Boost) Vin Pout Time Time Follower Boost Benefits The follower boost circuit offers and opportunity to reduce the output voltage Vout whenever the rms input voltage Vac is lower or the power demand Pout is higher. Because of the step−up characteristics of boost converter, the output voltage Vout will always be higher than the input voltage Vin even though Vout is reduced in follower boost operation. As a result, the on time t1 is reduced. Reduction of on time makes the loss of the inductor and power MOSFET smaller. Hence, it allows cheaper cost in the inductor and power MOSFET or allows the circuit components to operate at a lower stress condition in most of the time. Reference Section The internal reference voltage (VREF) is trimmed to be ±2% accurate over the temperature range (the typical value is 2.5 V). VREF is the reference used for the regulation. VREF also serves to build the thresholds of the fast transient response, Overvoltage (OVP), brown out (BO), and Undervoltage protections (UVP). Output Feedback The output voltage Vout of the PFC circuits is sensed at Vfb pin via the resistor divider (RfbL and RfbU) as shown in Figure 38. Vout is regulated as described in (Equation 19). Vout + VREF RfbU ) RfbL RfbL (eq. 19) 
