PRIMARY SIDE CONTROL IC FOR OFF-LINE BATTERY CHARGERS AP3706 General Description. Features

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1 General Description The AP3706 is a high performance AC/DC power supply controller for battery charger and adapter applications. The device uses Pulse Frequency Modulation (PFM) method to build discontinuous conduction mode (DCM) flyback power supplies. The AP3706 provides constant voltage, constant current (CV/CC) regulation without requiring an optocoupler and secondary control circuitry. It also eliminates the need of loop compensation circuitry while maintaining stability. The AP3706 achieves excellent regulation and high power efficiency, the no-load power consumption is less than 00mW at 65VAC input. The AP3706 is available in OIC-8 package. Features Primary ide Control for Rectangular Constant Current and Constant Voltage Output Eliminates Opto-Coupler and econdary CV/CC Control Circuitry Eliminates Control Loop Compensation Circuitry Flyback Topology in DCM Operation Random Frequency Modulation to Reduce ystem EMI Valley Turn on of External Power NPN Transistor Built-in oft tart Open Circuit Protection Over Voltage Protection hort Circuit Protection Applications Adapters/Chargers for Cell/Cordless Phones, PDAs, MP3 and Other Portable Apparatus tandby and Auxiliary Power upplies OIC-8 Figure 1. Package Type of AP3706 1

2 Pin Configuration M Package (OIC-8) C 1 8 VCC 7 BIA OUT 3 6 VDD GND 4 5 FB Figure. Pin Configuration of AP3706 (Top View) Pin Description Pin Number Pin Name Function 1 C The primary current sense VCC upply voltage 3 OUT This pin drives the base of external power NPN switch 4 GND Ground 5 FB The voltage feedback from the auxiliary winding 6 VDD The 5V output of the internal voltage regulator 7 BIA This pin sets the bias current inside AP3706 with an external resistor to GND 8 This pin connects a bypass capacitor for CC function

3 Functional Block Diagram VCC FB 5 0.1V UVLO pfm OVP & OCkP Tonsec Detector pro Tons Regulator & Bias UVLO 6 7 VDD BIA 4.0V EA Tons V+ &H Vea V+ Vea pfm_d R Q CV_ctrl pfm Driver 3 OUT C 1 t 0.5V pfm LEB Delay 430ns pfm_d 0.46V V DD Tons I V R Q CC_ctrl 4 GND 0.75*I Figure 3. Functional Block Diagram of AP3706 3

4 Ordering Information AP Circuit Type E1: Lead Free G1: Green TR: Tape and Reel Blank: Tube Package M: OIC-8 Package OIC-8 Temperature Range -40 to 85 o C Part Number Marking ID Lead Free Green Lead Free Green Packing Type AP3706M-E1 AP3706M-G1 3706M-E1 3706M-G1 Tube AP3706MTR-E1 AP3706MTR-G1 3706M-E1 3706M-G1 Tape & Reel BCD emiconductor's Pb-free products, as designated with "E1" suffix in the part number, are RoH compliant. Products with "G1" suffix are available in green packages. Absolute Maximum Ratings (Note 1) Parameter Value Unit upply Voltage VCC -0.3 to 30 V Voltage at C, BIA, OUT, VDD, to GND -0.3 to 7 V FB input (Pin 5) -40 to 10 V Output Current at OUT Internally limited A Power Dissipation at T A =5 o C W Operating Junction Temperature 150 o C torage Temperature -65 to 150 o C Lead Temperature (oldering, 10s) 300 o C Thermal Resistance Junction-to-Ambient 190 o C/W ED (Machine Model) 00 V Note 1: tresses greater than those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated under "Recommended Operating Conditions" is not implied. Exposure to "Absolute Maximum Ratings" for extended periods may affect device reliability. 4

5 Electrical Characteristics (V CC =15V, T A =5 o C, unless otherwise specified.) Parameter ymbol Conditions Min Typ Max Unit UVLO ECTION tart-up Threshold V TH (T) V Minimal Operating Voltage V OPR (min) After turn on V REFERENCE VOLTAGE ECTION R BIA Pin Voltage V BIA =00kΩ, BIA Before turn on V VDD Pin Voltage VDD V TANDBY CURRENT ECTION V tart-up Current I CC = V TH (T) -0.5V, T R BIA =00kΩ, Before turn on μa Operating Current I CC(OPR) R BIA =00kΩ μa DRIVE OUTPUT ECTION OUT Maximum Current ink I OUT R BIA =00kΩ 50 ma ource 5 30 CURRENT ENE ECTION Current ense Threshold V C mv Pre-Current ense V C(PRE) mv Leading Edge Blanking 430 ns FEEDBACK INPUT ECTION Feedback Threshold V FB V Enable Turn-on Voltage V FB(EN) V THREHOLD VOLTAGE ECTION Turn-on Threshold Voltage V V PROTECTION ECTION Over Voltage Protection V FB(OVP) V May 008 Rev. 1. 5

6 Typical Performance Characteristics tart-up Voltage (V) tartup Current (μa) R BIA =00kΩ 30 R BIA =00kΩ Ambient Temperature ( o C) Ambient Temperature ( o C) Figure 4. tart-up Voltage vs. Ambient Temperature Figure 5. tart-up Current vs. Ambient Temperature Operating Current (μa) V DD (V) R BIA =00kΩ Ambient Temperature ( o C) Ambient Temperature ( o C) Figure 6. Operating Current vs. Ambient Temperature Figure 7. V DD vs. Ambient Temperature 6

7 Typical Performance Characteristics (Continued) tart-up Current (μa) Out ource Current (ma) T A =5 o C 10 T A =5 o C Bias Resistor (kω) Bias Resistor (kω) Figure 8. tart-up Current vs. Bias Resistor Figure 9. OUT ource Current vs. Bias Resistor 7

8 Operation Description Bridge Vg V D1 V O V IN + C1 L M N P N I + CO I O Q1 V AUX AP3706 OUT FB GND C I P N AUX R C Figure 10. implified Flyback Converter Controlled by AP3706 Figure 10 illustrates a simplified flyback converter controlled by AP3706. Constant Primary Peak Current The primary current ip(t) is sensed by a current sense resistor R C as shown in Figure 10. The current rises up linearly at a rate of: dip ( t) vg( t) =...(1) dt Ip 0A L M As illustrated in Figure 11, when the current ip(t) rises up to Ipk, the switch Q1 turns off. The constant peak current is given by: ee equation Figure 11. Primary Current Waveform Vcs Ipk =...() Rcs The energy stored in the magnetizing inductance LM each cycle is therefore: Eg = 1 L M Ipk o the power transferring from the input to the output is given by: 1 P = LM Ipk f...(4) W Where the fsw is the switching frequency. When the peak current Ipk is constant, the output power depends on the switching frequency fsw. Constant Voltage Operation The AP3706 captures the auxiliary winding feedback voltage at FB pin and operates in constant-voltage (CV) mode to regulate the output voltage. Assuming the secondary winding is master, the auxiliary winding is slave during the D1 on-time. The auxiliary voltage is given by: V N AUX = ( Vo Vd )...(5) N AUX +...(3) 8

9 Operation Description (Continued) Where the Vd is the diode forward drop voltage. The relationship between the output constant-current and secondary peak current Ipks is given by: ee equation 5 1 Tons Iout = Ipks Tons + Toffs...(7) 0V /3 Tons Tons Figure 1. Auxiliary Voltage Waveform The output voltage is different from the secondary voltage in a diode forward drop voltage. The diode drop voltage depends on the current. If the secondary voltage is always detected at a constant secondary current, the difference between the output voltage and the secondary voltage will be a fixed Vd. The voltage detection point is at two-thirds of the D1 on-time. The CV loop control function of AP3706 then generates a D1 off-time to regulate the output voltage. Constant Current Operation The AP3706 is designed to work in constant-current (CC) mode. Figure 13 shows the secondary current waveforms. At the instant of D1 turn-on, the primary current transfers to the secondary at an amplitude of: N Ipks = P Ipk...(8) N Thus the output constant-current is given by: Iout = 1 N N P Tons N Ipk = Tons + Toffs 7 N Ipk Leading Edge Blanking When the power switch is turned on, a turn-on spike will occur on the sense-resistor. To avoid falsetermination of the switching pulse, a 430ns leadingedge blanking is built in. During this blanking period, the current sense comparator is disabled and the gate driver can not be switched off. P...(9) Is 0A Tons Toffs ee equation 8 Iout CCM Protection The AP3706 is designed to operate in discontinuous conduction mode (DCM) in both CV and CC modes. To avoid operating in continuous conduction mode (CCM), the AP3706 detects the falling edge of the FB input voltage on each cycle. If a 0.1V falling edge of FB is not detected, the AP3706 will stop switching. Figure 13. econdary Current Waveform In CC operation, the CC loop control function of AP3706 will keep a fixed proportion between D1 ontime Tons and D1 off-time Toffs by discharging or charging the capacitance connected in pin. The fixed proportion is Tons 4 = Toffs 3...(6) OVP & OCkP The AP3706 includes output over-voltage protection (OVP) and open circuit protection (OCkP) circuitry as shown in Figure 14. If the voltage at FB pin exceeds 8V, 100% above the normal detection voltage, or the -0.7V falling edge of the FB input can not be monitored, the AP3706 will immediately shut off and enters hiccup mode. The AP3706 sends out a fault detection pulse every 8ms in hiccup mode until the fault has been removed. 9

10 Operation Description (Continued) FB 8V R Q pro -0.7V Timer_8ms UVLO Figure 14. OVP and OCkP Function Block Typical Application Bridge T1 D 5V/1A V O + J1 AC 85-64V + C1 R1 R6 C + Z1 D1 C6 + V O - R Q1 C VCC OUT R3 AP3706 R9 C5 BIA FB GND VDD R7 R10 R11 R4 R5 C3 C4 R8 Figure 15. 5V/1A Output for Battery Charger of Mobile Phone 10

11 Mechanical Dimensions OIC-8 Unit: mm(inch) (0.185) 5.100(0.01) 1.350(0.053) 1.750(0.069) 0.30(0.013) (0.039) (0.050) TYP 0.100(0.004) 0.300(0.01) R0.150(0.006) 0.675(0.07) 0.75(0.09) D 0 8 D 0: (0.8) 6.00(0.44) φ 0.800(0.031) 0.00(0.008) 3.800(0.150) 4.000(0.157) 0.330(0.013) 0.510(0.00) 0.190(0.007) 0.50(0.010) 0.900(0.035) (0.017) 0.800(0.031) R0.150(0.006) May 008 Rev

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