Electronic Components Datasheet Search |
|
ACT512 Datasheet(PDF) 6 Page - Active-Semi, Inc |
|
ACT512 Datasheet(HTML) 6 Page - Active-Semi, Inc |
6 / 14 page ACT512 Rev 4, 13-Feb-14 Innovative PowerTM - 6 - www.active-semi.com Copyright © 2014 Active-Semi, Inc. Active-Semi Proprietary―For Authorized Recipients and Customers ActiveQR TM is a trademark of Active-Semi. ACT512 is a high performance peak current mode low-voltage PWM controller IC. The controller includes the most advance features that are required in the adaptor applications up to 60 Watt. Unique fast startup, frequency foldback, QR switching technique, accurate peak current line compensation, idle mode, short winding protection, OCP, OTP, OVP and UVLO are included in the controller. Startup Startup current of ACT512 is designed to be very low so that VDD could be charged to VDDON threshold level and device starts up quickly. A large value startup resistor can therefore be used to minimize the power loss yet reliable startup in application. For a typical AC/DC adaptor with universal input range design, two 1MΩ, 1/8 W startup resistors could be used together with a VDD capacitor(4.7uF) to provide a fast startup and yet low power dissipation design solution. During startup period, the IC begins to operate with minimum Ippk to minimize the switching stresses for the main switch, output diode and transformers. And then, the IC operates at maximum power output to achieve fast rise time. After this, VOUT reaches about 90% VOUT , the IC operates with a ‘soft-landing’ mode(decrease Ippk) to avoid output overshoot. Constant Voltage (CV) Mode Operation In constant voltage operation, the ACT512 regulates its output voltage through secondary side control circuit . The output voltage information is sensed at FB pin through OPTO coupling. The error signal at FB pin is amplified through TL431 and OPTO circuit. When the secondary output voltage is above regulation, the error amplifier output voltage decreases to reduce the switch current. When the secondary output voltage is below regulation, the error amplifier output voltage increases to ramp up the switch current to bring the secondary output back to regulation. The output regulation voltage is determined by the following relationship: where RF1 (R15) and RF2 (R16) are top and bottom feedback resistor of the TL431. No Load Idle Mode In no load standby mode, the feedback voltage falls below VFBBM2 and reaches VFBBM1, ACT512 stop switching. After it stops, as a result of a feedback reaction, the feedback voltage increases. When the feedback voltage reaches VFBBM2, ACT512 start switching again. Feedback voltage drops again and output voltage starts to bounds back and forward with very small output ripple. ACT512 leaves idle mode when load is added strong enough to pull feedback voltage exceed VFBBM2. Figure 2: Idle Mode Primary Inductor Current Limit Compensation The ACT512 integrates a primary inductor peak current limit compensation circuit to achieve constant OLP over wide line and wide inductance. Frequency Foldback When the load drops to 75% of full load level, ACT512 starts to reduce the switching frequency, which is proportional to the load current ,to improve the efficiency of the converter. ACT512’s load adaptive switching frequency enables applications to meet all latest green energy standards. The actual minimum average switching frequency is programmable with output capacitance, feedback circuit and dummy load (while still meeting standby power). Valley Switching ACT512 employed valley switching from no load to heavy load to reduce switching loss and EMI. In discontinuous mode operation, the resonant voltage between inductance and parasitic capacitance on MOSFET source pin is coupled by auxiliary winding and reflected on VDET pin through feedback network R5, R6. Internally, the VDET pin is connected to an zero-crossing detector to generate the switch turn on signal when the conditions are met. FUNCTIONAL DESCRIPTION (1) ) R R 1 ( V V 2 F 1 F 431 TL _ REF OUTCV + × = Ip Vo Vfb t Ip_FL Ilim Vfb_fl Vfb_olp 2A Vfbbm1 Io 12V Vfbbm2 0A |
Similar Part No. - ACT512_14 |
|
Similar Description - ACT512_14 |
|
|
Link URL |
Privacy Policy |
ALLDATASHEET.NET |
Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Contact us | Privacy Policy | Link Exchange | Manufacturer List All Rights Reserved©Alldatasheet.com |
Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
Family Site : ic2ic.com |
icmetro.com |