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1、CCM-PFC ICE2PCS02 ICE2PCS02G Standalone Power Factor Correction (PFC) Controller in Continuous Conduction Mode (CCM) with Input Brown-Out Protection N e v e r s t o p t h i n k i n g . Version 2.3, 9 Oct 2007 Power Management the inner current loop and the outer voltage loop. The inner current loop
2、of the IC controls the sinusoidal profile for the average input current. It uses the dependency of the PWM duty cycle on the line input voltage to determine the corresponding input current. This means the average input current follows the input voltage as long as the device operates in CCM. Under li
3、ght load condition, depending on the choke inductance, the system may enter into discontinuous conduction mode (DCM) resulting in a higher harmonics but still meeting the Class D requirement of IEC 1000-3-2. The outer voltage loop controls the output bus voltage. Depending on the load condition, OTA
4、1 establishes an appropriate voltage at VCOMP pin which controls the amplitude of the average input current. The IC is equipped with various protection features to ensure safe operating condition for both the system and device. 3.2Power Supply An internal under voltage lockout (UVLO) block monitors
5、the VCC power supply. As soon as it exceeds 11.8V and both voltages at pin 6 (VSENSE) 0.6V and pin 4 (VINS) 1.5V, the IC begins operating its gate drive and performs its Startup as shown in Figure 3. . Figure 3State of Operation respect to VCC If VCC drops below 11V, the IC is off. The IC will then
6、be consuming typically 300A, whereas consuming 10mA during normal operation. The IC can be turned off and forced into standby mode by pulling down the voltage at pin 6 (VSENSE) to lower than 0.6V. In this standby mode, the current consumption is reduced to 300A. Other condition that can result in th
7、e standby mode is when a Brown-out condition occurs, ie pin 4 (VINS) 0.6 V) AND (VVINS 1.5 V) 11.8 V 11.0 V t OFF Start Up Open loop/ Standby Normal Operation ICs State OFF Normal Operation (VVSENSE 0.6 V) AND (VVINS 1.5 V) VCOMP C5 C4 VSENSE OTA1 3V ICE2PCS02/G protect R3 + R4 R4 x VOUT )( R6 S1 3F
8、unctional Description CCM-PFC ICE2PCS02/G Functional Description Version 2.389 Oct 2007 . Figure 5Startup with controlled maximum current 3.4System Protection The IC provides several protection features in order to ensure the PFC system in safe operating range: VCC Undervoltage Lockout (UVLO) Input
9、Brown-out Detection (IBOP) Soft Over Current Control (SOC) Peak Current Limit (PCL) Open-Loop Detection (OLP) Output Over-Voltage Protection (OVP) After the system is supplied with the correct level of VCC and VIN, the system will enter into its normal mode of operation. Figure 6 shows situation whe
10、n these protections features are active, as a function of the output voltage VOUT. An activation of the UVLO, IBOP and OLP results in the internal fault signal going high and brings the IC into the standby mode. As the function of UVLO has already described in the earlier “Power Supply” section, the
11、 following sections continue to describe the functionality of these protection features. Figure 6Protection Features 3.4.1Input Brown-Out Protection (IBOP) Brown-out occurs when the input voltage VIN falls below the minimum input voltage of the design (i.e. 85V for universal input voltage range) and
12、 the VCC has not entered into the VCCUVLO level yet. For a system without IBOP, the boost converter will increasingly draw a higher current from the mains at a given output power which may exceed the maximum design values of the input current. ICE2PCS02/G provides a new IBOP feature whereby it sense
13、s directly the input voltage for Input Brown-Out condition via an external resistor/capacitor/diode network as shown in Figure 7. This network provides a filtered value of VIN which turns the IC on when the voltage at pin 4 (VINS) is more than 1.5V. The IC enters into the standby mode when VINS goes
14、 below 0.71V. The hysteresis prevents the system to oscillate between normal and standby mode. Note also that VIN needs to at least 20% of the rated VOUT in order to overcome OLP and powerup the system. Figure 7Input Brown-Out Protection (IBOP) av(IIN) VOUT t VOUT =rated 95%rated Window DetectNormal
15、 Control t Max Vcomp current 83%rated VCOMP Level-shifted VCOMP t VOUT PCL / SOC 20% 100% OLPOLP 108% OVP VOUT,Rated UVLO / IBOP Supply related Current related Output related ICE2PCS02/G 85 . 265 VAC Vin C1 D2 . D5 VINS C4 C5R S 1.5V 0.71V Brown-Out Detection R8 R9C6 D7 brown-out 3.5V CCM-PFC ICE2PC
16、S02/G Functional Description Version 2.399 Oct 2007 3.4.2Soft Over Current Control (SOC) The IC is designed not to support any output power that corresponds to a voltage lower than -0.75V at the ISENSE pin. A further increase in the inductor current, which results in a lower ISENSE voltage, will activate the Soft Over Current Control (SOC). This is a soft control as it does not directly switch off the gate drive. It acts on the nonlinear gain block to result in a reduced PWM duty cycle.
