ACT334 Rev 2, 14-Nov-12 High Performance ActivePSRTM Primary Switching Regulator FEATURES over temperature conditions. • Ultra Low Standby Power < 30mW The ACT334 ActivePSRTM is optimized for high performance, cost-sensitive applications, and utilizes Active-Semi’s proprietary primary-side feedback architecture to provide accurate constant voltage, constant current (CV/CC) regulation without the need of an opto-coupler or reference device. Integrated line and primary inductance compensation circuitry provides accurate constant current operation despite wide variations in line voltage and primary inductance. Integrated output cord resistance compensation further enhances output accuracy. The ACT334 achieves excellent regulation and transient response, yet requires less than 30mW of standby power. • Patented Primary Side Regulation Technology • Suitable Operation Frequency up to 85kHZ • Proprietary Fast Startup Circuit • Integrated Line and Primary Inductance Compensation • Integrated Programmable Output Cord Resistance Compensation • Line Under-Voltage, Output Over-Voltage, Output Short-Circuit and Over-Temperature Protection The ACT334 is optimized for compact size 2W to 6W charger applications. It is available in spacesaving 6 pin SOT23-6 package. • Complies with all Global Energy Efficiency and CEC Average Efficiency Standards • Adjustable Power from 2W to 6W • Minimum External Components • Tiny SOT23-6 Package Figure 1: Simplified Application Circuit APPLICATIONS • Chargers for Cell Phones, PDAs, MP3, Portable Media Players, DSCs, and Other Portable Devices and Appliances • RCC Adapter Replacements • Linear Adapter Replacements • Standby and Auxiliary Supplies GENERAL DESCRIPTION The ACT334 belongs to the high performance patented ActivePSRTM Family of Universal-input AC/DC off-line controllers for battery charger and adapter applications. It is designed for flyback topology working in discontinuous conduction mode (DCM). The ACT334 meets all of the global energy efficiency regulations (CEC, European Blue Angel, and US Energy Star standards) while using very few external components. The ACT334 ensures safe operation with complete protection against all fault conditions. Built-in protection circuitry is provided for output shortcircuit, output over-voltage, line under-voltage, and Innovative PowerTM -1- www.active-semi.com Copyright © 2012 Active-Semi, Inc. ACT334 Rev 2, 14-Nov-12 ORDERING INFORMATION PART NUMBER TEMPERATURE RANGE PACKAGE PINS PACKING METHOD TOP MARK ACT334US-T -40°C to 85°C SOT23-6 6 TAPE & REEL FSTA PIN CONFIGURATION SOT23-6 ACT334US-T PIN DESCRIPTIONS PIN NAME DESCRIPTION 1 SW Switch Drive. Switch node for the external NPN transistor. Connect this pin to the external power NPN’s emitter. This pin also supplies current to VDD during startup. 2 GND 3 BD 4 VDD Power Supply. This pin provides bias power for the IC during startup and steady state operation. 5 FB Feedback Pin. Connect this pin to a resistor divider network from the auxiliary winding. 6 CS Current Sense Pin. Connect an external resistor (RCS) between this pin and ground to set peak current limit for the primary switch. The peak current limit is set by (0.396V × 0.9) / RCS. For more detailed information, see Application Information. Innovative PowerTM Ground. Base Drive. Base driver for the external NPN transistor. -2- www.active-semi.com Copyright © 2012 Active-Semi, Inc. ACT334 Rev 2, 14-Nov-12 ABSOLUTE MAXIMUM RATINGSc PARAMETER VALUE UNIT -0.3 to + 28 V 100 mA -0.3 to + 6 V Internally limited A Maximum Power Dissipation (derate 4.5mW/˚C above TA = 50˚C)(SOT23-6) 0.45 W Junction to Ambient Thermal Resistance (θJA)(SOT23-6) 220 ˚C/W Operating Junction Temperature -40 to 150 ˚C Storage Junction -55 to 150 ˚C 300 ˚C VDD, BD, SW to GND Maximum Continuous VDD Current FB, CS to GND Continuous SW Current Lead Temperature (Soldering, 10 sec) c: Do not exceed these limits to prevent damage to the device. Exposure to absolute maximum rating conditions for long periods may affect device reliability. ELECTRICAL CHARACTERISTICS (VDD = 14V, VOUT = 5V, LP = 1.6mH, NP = 140, NS = 8, NA = 23, TA = 25°C, unless otherwise specified.) PARAMETER SYMBOL TEST CONDITIONS MIN TYP MAX UNIT Supply VDD Turn-On Voltage VDDON VDD Rising from 0V 17.6 18.6 19.6 V VDD Turn-Off Voltage VDDOFF VDD Falling after Turn-on 5.25 5.5 5.75 V IDD VDD = 14V, after Turn-on 240 340 440 uA 25 45 µA 1 µA Supply Current Start Up Supply Current IDDST BD Current during Startup IBDST VDD = 14V, before Turn-on Internal Soft Startup Time 10 ms Oscillator Switching Frequency Maximum Switching Frequency fSW 100% VOUTCV @ full load 80 25% VOUTCV @ full load 40 kHz FCLAMP 89 98 107 kHz DMAX 65 75 85 % Effective FB Voltage VFB 2.17 2.192 2.216 V FB Leakage Current IFBLK 1 µA Maximum Duty Cycle Feedback Output Cable Resistance Compensation Innovative PowerTM DVCOMP No RCORD between VDD and SW 0 RCORD = 300k 3 RCORD = 150k 6 RCORD = 75k 9 RCORD = 33k 12 -3- % www.active-semi.com Copyright © 2012 Active-Semi, Inc. ACT334 Rev 2, 14-Nov-12 ELECTRICAL CHARACTERISTICS CONT’D (VDD = 14V, VOUT = 5V, LP = 1.5mH, NP = 140, NS = 8, NA = 23, TA = 25°C, unless otherwise specified.) PARAMETER SYMBOL TEST CONDITIONS MIN TYP MAX UNIT 600 mA 412 mV Current Limit SW Current Limit Range 100 ILIM CS Current Limit Threshold VCSLIM tOFF_DELAY = 0 Leading Edge Blanking Time 380 396 200 300 ns Driver Outputs Switch ON-Resistance RON ISW = 50mA SW Off Leakage Current 1.6 VSW = VDD = 22V 3 Ω 1 µA VDDON +4 V Protection VDD Latch-Off Voltage VDDON +2 VDDOVP VDDON +3 Thermal Shutdown Temperature 135 ˚C Thermal Hysteresis 20 ˚C 134 µA Line UVLO IFBUVLO FUNCTIONAL BLOCK DIAGRAM VDD BD SW REGULATOR ON & UVLO BASE DRIVER OTP REFERENCE OVP + - + - + 2.20V SIGNAL FILTER - FB LOGIC + CABLE COMPENSATION OSCILLATOR 0.4V - CURRENT SHAPING + G Innovative PowerTM CS -4- www.active-semi.com Copyright © 2012 Active-Semi, Inc. ACT334 Rev 2, 14-Nov-12 FUNCTIONAL DESCRIPTION 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: As shown in the Functional Block Diagram, to regulate the output voltage in CV (constant voltage) mode, the ACT334 compares the feedback voltage at FB pin to the internal reference and generates an error signal to the pre-amplifier. The error signal, after filtering out the switching transients and compensated with the internal compensation network, modulates the external NPN transistor peak current at CS pin with current mode PFWM (Pulse Frequency and Width Modulation) control. To regulate the output current in CC (constant current) mode, the oscillator frequency is modulated by the output voltage. ⎛ R VOUTCV = 2 .20 V × ⎜⎜1 + FB 1 R FB 2 ⎝ (1) where RFB1 (R5) and RFB2 (R6) are top and bottom feedback resistor, NS and NA are numbers of transformer secondary and auxiliary turns, and VD is the rectifier diode forward drop voltage at approximately 0.1A bias. SW is a driver output that drives the emitter of an external high voltage NPN transistor. This baseemitter-drive method makes the drive circuit the most efficient. Standby (No Load) Mode In no load standby mode, the ACT334 oscillator frequency is further reduced to a minimum frequency while the current pulse is reduced to a minimum level to minimize standby power. The actual minimum switching frequency is programmable with an output preload resistor. Fast Startup VDD is the power supply terminal for the ACT334. During startup, the ACT334 typically draws only 25μA supply current. The startup resistor from the rectified high voltage DC rail supplies current to the base of the NPN transistor. This results in an amplified emitter current to VDD through the SW pin via Active-Semi's proprietary fast-startup circuitry until it exceeds the VDDON threshold 19V. At this point, the ACT334 enters internal startup mode with the peak current limit ramping up in 10ms. After switching starts, the output voltage begins to rise. The VDD bypass capacitor must supply the ACT334 internal circuitry and the NPN base drive until the output voltage is high enough to sustain VDD through the auxiliary winding. The VDDOFF threshold is 5.5V; therefore, the voltage on the VDD capacitor must remain above 5.5V while the output is charging up. Loop Compensation The ACT334 integrates loop compensation circuitry for simplified application design, optimized transient response, and minimal external components. Output Cable Resistance Compensation The ACT334 provides programmable output cable resistance compensation during constant voltage regulation, monotonically adding an output voltage correction up to predetermined percentage at full power. There are four levels to program the output cable compensation by connecting a resistor (R10 in Figure 6) from the SW pin to VDD pin. The percentage at full power is programmable to be 3%, 6%, 9% or 12%, and by using a resistor value of 300k, 150k, 75k or 33k respectively. If there is no resistor connection, there is no cord compensation. Constant Voltage (CV) Mode Operation This feature allows for better output voltage accuracy by compensating for the output voltage droop due to the output cable resistance. In constant voltage operation, the ACT334 captures the auxiliary flyback signal at FB pin through a resistor divider network R5 and R6 in Figure 6. The signal at FB pin is pre-amplified against the internal reference voltage, and the secondary side output voltage is extracted based on Active-Semi's proprietary filter architecture. Constant Current (CC) Mode Operation When the secondary output current reaches a level set by the internal current limiting circuit, the ACT334 enters current limit condition and causes the secondary output voltage to drop. As the output voltage decreases, so does the flyback voltage in a proportional manner. An internal current shaping circuitry adjusts the switching frequency based on the flyback voltage so that the transferred power remains proportional to the output voltage, resulting This error signal is then amplified by the internal error amplifier. 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 Innovative PowerTM ⎞ NS ⎟⎟ × − VD ⎠ NA -5- www.active-semi.com Copyright © 2012 Active-Semi, Inc. ACT334 Rev 2, 14-Nov-12 FUNCTIONAL DESCRIPTION CONT’D in a constant secondary side output current profile. The energy transferred to the output during each switching cycle is ½(LP × ILIM2) × η, where LP is the transformer primary inductance, ILIM is the primary peak current, and η is the conversion efficiency. From this formula, the constant output current can be derived: 2 IOUTCC = ⎛ 0.396V × 0.9 ⎞ ⎛ η × fSW 1 ⎟⎟ × ⎜⎜ × LP × ⎜⎜ 2 RCS ⎝ ⎠ ⎝ VOUTCV ⎞ ⎟⎟ ⎠ die temperature. The typical over temperature threshold is 135°C with 20°C hysteresis. When the die temperature rises above this threshold the ACT334 is disabled until the die temperature falls by 20°C, at which point the ACT334 is re-enabled. TYPICAL APPLICATION Design Example (2) The design example below gives the procedure for a DCM flyback converter using the ACT334. Refer to Application Circuit in Figure 6, the design for a charger application starts with the following specification: where fSW is the switching frequency and VOUTCV is the nominal secondary output voltage. The constant current operation typically extends down to lower than 40% of nominal output voltage regulation. Input Voltage Range Primary Inductance Compensation The ACT334 integrates a built-in proprietary (patent-pending) primary inductance compensation circuit to maintain constant current regulation despite variations in transformer manufacturing. The compensated range is ±7%. Primary Inductor Current Limit Compensation 5W Output Voltage, VOUTCV 5.0V Full Load Current, IOUTFL 1A OCP Current, IOUTMAX 1.3A Transformer Efficiency, ηxfm 0.90 System Efficiency CC, ηsystem 0.72 System Efficiency CV, η 0.73 The operation for the circuit shown in Figure 6 is as follows: the rectifier bridge D1−D4 and the capacitor C1/C2 convert the AC line voltage to DC. This voltage supplies the primary winding of the transformer T1 and the startup resistor R7/R8. The primary power current path is formed by the transformer’s primary winding, the NPN transistor, the ACT334 internal MOSFET and the current sense resistor R9. The network consisting of capacitor C4 and diode D6 provides a VDD supply voltage for ACT334 from the auxiliary winding of the transformer. C4 is the decoupling capacitor of the supply voltage and energy storage component for startup. The diode D8 and the capacitor C5 rectifies and filters the output voltage. The resistor divider consisting of R5 and R6 programs the output voltage. The ACT334 integrates a primary inductor peak current limit compensation circuit to achieve constant input power over line and load ranges. Protection The ACT334 incorporates multiple protection functions including over-voltage, over-current and over-temperature. Output Short Circuit Protection When the secondary side output is short circuited, the ACT334 enters hiccup mode operation. In this condition, the VDD voltage drops below the VDDOFF threshold and the auxiliary supply voltage collapses. This turns off the ACT334 and causes it to restart. This hiccup behavior continues until the short circuit is removed. The minimum and maximum DC input voltages can be calculated: Output Over Voltage Protection The ACT334 includes output over-voltage protection circuitry, which shuts down the IC when the output voltage is 40% above the normal regulation voltage for 4 consecutive switching cycles. The ACT334 enters hiccup mode when an output over voltage fault is detected. 1 − tC ) 2 fL η × C IN 2 POUT ( VINDCMIN = = Over Temperature Shutdown 2V 2 ACMIN − 1 2 × 5( − 3 . 8 ms ) 2 2 × 50 2 × 85 − ≈ 90 V 72 % × 2 × 6 . 8 μ F VINDCMAX = 2 × VACMAX = 2 × 265 = 375V The thermal shutdown circuitry detects the ACT334 Innovative PowerTM 85VAC - 265VAC, 50/60Hz Output Power, PO -6- (3) (4) www.active-semi.com Copyright © 2012 Active-Semi, Inc. ACT334 Rev 2, 14-Nov-12 TYPICAL APPLICATION CONT’D where η is the estimated circuit efficiency, fL is the line frequency, tC is the estimated rectifier conduction time, CIN is empirically selected to be 2 × 6.8µF electrolytic capacitors based on the 3µF/W rule of thumb. VINDCMAX × ( VOUTCV + VDS ) 375 × ( 5 + 0 .2 ) = = 73 V VDREV − VOUTCV 40 × 0 . 8 − 5 2 × I IN 2 × 75 .6 = = 338 mA D 45 % VINDCMIN × D 90 × 45% = ≈ 1.6 mH IPK × fSW 338mA × 76kHz LP × IPK OUTCV + VDS ) × NP NS < 0.9 N ⇒ P > 17.1 fSW NS (13) 0.9 ×VCSLIM (IOUTFL + IOUTMAX) ×VOUT = 0.9 × 0.396 = 1R (1 +1.3 ) × 5 ⎛ 0.72 ⎞ 1.6 ×75 × ⎜ ⎟ ⎝ 0.90 ⎠ are NA LP 23 1.6 × ×K = × × 229656 ≈ 60.4k NP RCS 140 1 R FB 2 = (14) selected (15) VFB ( VOUTCV + VDS ) NA − VFB NS R FB 1 (16) 2 .20 = × 60 .4 = 10 .5 k ( 5 + 0 . 4 ) × 2 . 87 − 2 .20 (6) When selecting the output capacitor, a low ESR electrolytic capacitor is recommended to minimize ripple from the current ripple. The approximate equation for the output capacitance value is given by: (7) COUT = (8) IOUTCC× D 1× 0.45 = = 120μF fSW ×△VRIPPLE 75kHz× 50mV (17) A 470µF electrolytic capacitor is used to keep the ripple small. PCB Layout Guideline Good PCB layout is critical to have optimal performance. Decoupling capacitor (C4), current sense resistor (R9) and feedback resistor (R5/R6) should be placed close to VDD, CS and FB pins respectively. There are two main power path loops. One is formed by C1/C2, primary winding, NPN transistor and the ACT334. The other is the secondary winding, rectifier D8 and output capacitors (C5). Keep these loop areas as small as possible. Connect high current ground returns, the input capacitor ground lead, and the ACT334 G pin (9) (10) Where VDA is diode forward voltage of the auxiliary side and VR is the resister voltage. An EFD15 transformer gapped core with an effective inductance ALE of 82nH/T2 is selected. The number of turns of the primary winding is: Innovative PowerTM NA × N S = 2 . 87 × 8 = 23 NS Where K is IC constant and K = 229656. The auxiliary to secondary turns ratio NA/NS: NA VDD +VDA +VR 15 + 0.3 + 0.8 = = = 2.87 NS VOUTCV +VDS +VCORD 5 + 0.20 + 0.402 NA = RFB1 = ACT334 needs to work in DCM in all conditions, thus NP/NS should meet LP × IPK + VINDCMIN (V (12) The voltage feedback resistors according to below equation: (5) The primary inductance of the transformer: LP = NS 1 × NP = × 140 = 8 NP 17 .5 ⎛η ⎞ LP × fSW × ⎜⎜ system ⎟⎟ ⎝ ηxfm ⎠ The maximum input primary peak current at full load base on duty of 45%: I PK = NS = RCS = The maximum duty cycle is set to be 45% at low line voltage 85VAC and the circuit efficiency is estimated to be 73%. Then the full load input current is: VOUTCV × IOUTPL 5 ×1 = = 75 .6 mA VINDCMIN × η 90 × 72 % (11) The current sense resistance (RCS) determines the current limit value based on the following equation: where VDS is the Schottky diode forward voltage, VDREV is the maximum reverse voltage rating of the diode and VOUTCV is the output voltage. IIN = 1 .6 mH = 140 82 nH / T 2 The number of turns of secondary and auxiliary windings can be derived when Np/Ns=17.5: When the transistor is turned off, the voltage on the transistor’s collector consists of the input voltage and the reflected voltage from the transformer’s secondary winding. There is a ringing on the rising top edge of the flyback voltage due to the leakage inductance of the transformer. This ringing is clamped by a RCD network if it is used. Design this clamped voltage as 50V below the breakdown of the NPN transistor. The flyback voltage has to be considered with selection of the maximum reverse voltage rating of secondary rectifier diode. If a 40V Schottky diode is used, then the flyback voltage can be calculated: VRO = LP = ALE NP = -7- www.active-semi.com Copyright © 2012 Active-Semi, Inc. ACT334 Rev 2, 14-Nov-12 TYPICAL APPLICATION CONT’D to a single point (star ground configuration). output information can be sent back into the IC to do the appropriate control. NPN Selection Guideline VFB waveforms of Figure 3, Figure 4, and Figure 5 violate the sampling design margin and are not recommended. Figure 3 has very long overshoot period. Figure 4, and Figure 5 have very long ringing period. The undesired waveforms cause the IC to operate in an unstable mode easily due to wrong feedback information. NPN transistors with HFE of 20 to 30 are highly recommended in the design due to the start up time. If the HFE is too low the start up time becomes longer because of 30M start up resister. VFB Sampling Waveforms ACT334 senses the output voltage information through the VFB waveforms. Proper VFB waveforms are required for IC to operate in a stable status. To avoid mis-sampling, 1.8µs blanking time is added to blank the ringing period due to the leakage inductance and the circuit parasitic capacitance. Figure 2 is the recommended VFB waveform to guarantee the correct sampling point so that the Figure 3 Figure 2 1.8µs 1.8µs Figure 5 Figure 4 1.8µs 1.8µs Innovative PowerTM -8- www.active-semi.com Copyright © 2012 Active-Semi, Inc. ACT334 Rev 2, 14-Nov-12 Figure 6: Universal VAC Input, 5V/1A Output Charger Table 1: ACT334 Bill of Materials Item Reference 1 C1,C2 2 Description QTY Capacitor, Electrolytic, 6.8µF/400V, 10x12mm(Low leakage current) 2 C3 Capacitor, Ceramic,220pF/500V,1206,SMD 1 3 C4 Capacitor, Ceramic,4.7µF/35V,1206,SMD 1 4 C5,C6 Capacitor, Electrolytic, 680µF/10V, 8x12mm 2 5 C9 Capacitor, Ceramic,1000pF/50V, 0805, SMD 1 6 D1-D4 Diode,Rectifier,1000V/1A,1N4007, DO-41 4 7 D5,D6 Diode,Ultra Fast, FR107,1000V/1.0A, DO-41 2 8 D8 Diode, schottky, 40V/5A, SB540, DO-15 1 9 L1 Axial Inductor, 1.5mH, 0410,Dip 1 10 Q1 Transistor, HFE 20-25, NPN,13003,TO-126 1 11 FR1 Wire Round Resistor,1W,10Ω, KNP, 5% 1 12 R2 Chip Resistor, 1.5mΩ, 1206, 5% 1 13 R3 Chip Resistor, 100Ω, 1206, 5% 1 14 R1 Chip Resistor, 22Ω, 0805, 5% 1 15 R4 Chip Resistor, 15Ω, 0805, 5% 1 16 R5 Chip Resistor, 60.4kΩ, 0805,1% 1 17 R6 Chip Resistor, 10.5kΩ, 0805, 1% 1 18 R7,R8 Chip Resistor, 15mΩ, 1206, 5% 2 19 R9 Chip Resistor, 1.0Ω, 1206,1% 1 20 R10 Chip Resistor, 162kΩ, 0805, 5% 1 21 R11 Chip Resistor, 3.6kΩ, 0805, 5% 1 22 R13 Chip Resistor, 10Ω, 0805, 5% 1 23 T1 Transformer, Lp=1.6mH, EFD15 1 24 U1 IC, ACT334US-T,SOT23-6 1 Innovative PowerTM -9- www.active-semi.com Copyright © 2012 Active-Semi, Inc. ACT334 Rev 2, 14-Nov-12 TYPICAL PERFORMANCE CHARACTERISTICS CONT’D (Circuit of Figure 6, unless otherwise specified.) Start Up Supply Current vs. Temperature VDD ON/OFF Voltage vs. Temperature VDDON 16.5 26 24 14.5 IDDST (µA) VDDON and VDDOFF (V) 18.5 ACT334-008 28 ACT334-007 20.5 12.5 10.5 22 20 18 8.5 VDDOFF 6.5 16 4.5 14 0 25 50 75 0 Temperature (°C) 50 75 Normalized ILIM vs. Temperature FB Voltage vs. Temperature 1.01 Normalized ILIM (mA) 2.20 ACT334-010 1.02 ACT334-009 2.25 VFB (V) 25 Temperature (°C) 2.15 2.10 2.05 1.00 0.99 0.98 0.97 0.96 2.00 0.95 0 25 50 75 0 Temperature (°C) 25 50 75 Temperature (°C) Internal MOSFET RON vs. Temperature ACT334-012 2.4 2.0 RON (Ω) 1.6 1.2 0.8 0.4 0.0 0 25 50 75 Temperature (°C) Innovative PowerTM - 10 - www.active-semi.com Copyright © 2012 Active-Semi, Inc. ACT334 Rev 2, 14-Nov-12 PACKAGE OUTLINE SOT23-6 PACKAGE OUTLINE AND DIMENSIONS D θ 0.2 SYMBOL E E1 c e A A1 A2 e1 DIMENSION IN MILLIMETERS DIMENSION IN INCHES MIN MAX MIN MAX A - 1.450 - 0.057 A1 0.000 0.150 0.000 0.006 A2 0.900 1.300 0.035 0.051 b 0.300 0.500 0.012 0.020 c 0.080 0.220 0.003 0.009 L b D 2.900 BSC 0.114 BSC E 1.600 BSC 0.063 BSC E1 2.800 BSC 0.110 BSC e 0.950 BSC 0.037 BSC e1 1.900 BSC 0.075 BSC L 0.300 0.600 0.012 0.024 θ 0° 8° 0° 8° Active-Semi, Inc. reserves the right to modify the circuitry or specifications without notice. Users should evaluate each product to make sure that it is suitable for their applications. Active-Semi products are not intended or authorized for use as critical components in life-support devices or systems. Active-Semi, Inc. does not assume any liability arising out of the use of any product or circuit described in this datasheet, nor does it convey any patent license. Active-Semi and its logo are trademarks of Active-Semi, Inc. For more information on this and other products, contact [email protected] or visit http://www.active-semi.com. is a registered trademark of Active-Semi. Innovative PowerTM - 11 - www.active-semi.com Copyright © 2012 Active-Semi, Inc.