BL8835A QR/PSR CV/CC Controller GENERAL DESCRIPTION FEATURES BL8835A is a high performance, highly integrated QR (Quasi Resonant Mode) and Primary Side Regulation (PSR) controller for offline small power converter applications. BL8835A has proprietary QR/PSR control for high efficiency and low EMI. The IC also has built-in cable drop compensation function, which can provide excellent CV performance. BL8835A integrates functions and protections of Under Voltage Lockout (UVLO), VDD Over Voltage Protection (VDD OVP), Output Over Voltage Protection (Output OVP), Soft Start, Cycle-by-cycle Current Limiting (OCP), Pin Floating Protection, VDD Clamping. ◆ Proprietary QR/PSR (Quasi-Resonant & Primary Side Regulation) Control for High Efficiency and Low EMI ◆ Less than 100mW Standby Power ◆ ±5% CC and CV Precision ◆ Proprietary Cable Drop Compensation ◆ Cycle-by-Cycle Current Limiting ◆ Built-in Leading Edge Blanking (LEB) ◆ Pin Floating Protection ◆ Built-in Soft Start ◆ Output Over Voltage Protection ◆ VDD OVP & Clamp ◆ VDD Under Voltage Lockout (UVLO) BL8835A is offered in SOP8 package. APPLICATIONS Low Power AC/DC offline SMPS for ■ Cell Phone Charger ■ Digital Cameras Charger ■ Small Power Adapter ■ Auxiliary Power for PC, TV etc. ■ Linear Regulator/RCC Replacement TYPICAL APPLICATION www.belling.com.cn 1/7 V1.0 BL8835A QR/PSR CV/CC Controller GENERAL INFORMATION Pin Configuration The pin map is shown as below for SOP8. VDD 1 8 GND COMP 2 7 GND INV 3 6 DRAIN CS 4 5 DRAIN Package Dissipation Rating Package SOP8 RθJA (℃/W) 145 Absolute Maximum Ratings Parameter Value Drain Voltage (off state) -0.3V to Bvdss -0.3 to VDD Voltage VDD_clamp VDD Zener Clamp 10mA Continuous Current COMP Voltage -0.3 to 7V CS input Voltage -0.3 to 7V INV input Voltage -0.3 to 7V Max Operation Junction 150℃ Temperature Tj Min/Max storage -55 to 150℃ Temperature T-stg Lead Temperature 260℃ (Soldering,10secs) TERMINAL ASSIGNMENTS Pin Num 1 2 Pin Name VDD COMP I/O P I 3 INV I 4 CS I 5/6 DRAIN O 7/8 GND P www.belling.com.cn Description Power Supply Loop Compensation for CV Stability The Voltage feedback from auxiliary winding. Connected to resistor divider from auxiliary winding reflecting output voltage. PWM duty cycle is determined by EA output and current sense signal at pin 4. Current sense input HV MOSFET Drain pin. The Drain pin is connected to the primary lead of the transformer Ground 2/7 V1.0 BL8835A QR/PSR CV/CC Controller OUTPUT POWER TABLE Product BL8835A Universal Voltage Adapter 7.5W Package Test Condition SOP8 Indoor temperature 40℃ BLOCK DIAGRAM www.belling.com.cn 3/7 V1.0 BL8835A QR/PSR CV/CC Controller ELECTRICAL CHARACTERISTICS (TA=25℃,VDD=16V,if not otherwise noted) Symbol Parameter Supply Voltage (VDD) I_Startup VDD Startup Current I_VDD_Op Operation Current Test Conditions VDD Under Voltage Lockout Exit (Startup) UVLO(OFF) VDD Under Voltage Lockout Enter VDD Over Voltage Protection trigger VDD_OVP VDD_Clamp VDD Zener Clamp Voltage Feedback Input Section(INV Pin) Internal Error Amplifier(EA) reference VINV_EA_Ref input Output over voltage protection thresh VINV_OVP old VINV_Short Output Short Circuit Threshold Output Short Circuit Frequency FClamp_Short Clamp Demagnetization comparator VINV_DEM threshold Tmin_OFF Minimum OFF time Tmax_OFF Maximum OFF time Max Cable compensation current ICable_max Current Sense Input Section (CS Pin) CS Input Leading Edge Blanking Tim T_blanking e Over Current Detection and Control TD_OC Delay Constant Current Section (COMP Pin) V_comp_ref Internal CC reference Power MOSFET Section I(VDD)=7mA Max Unit 2 20 uA 1 1.5 mA 13.0 14.0 15.0 V 8.0 30 32 9.0 32 34 10.0 34 36 V V V 1.98 2.0 2.02 V CL=1nF at GATE 490 2.4 V 0.65 V 50 KHz 75 mV 2 2.8 40 us ms uA 500 ns 100 ns 500 510 610 BVdss Static, Id=0.4A Rdson www.belling.com.cn Typ. VDD=UVLO(ON)-1V , Measure current into VDD VINV=1V,CL=0.5nF, VDD=20V UVLO(ON) MOSFET Drain Source Breakdown Voltage ON Resistance Min 4/7 mV V 5.2 6.5 Ω V1.0 BL8835A QR/PSR CV/CC Controller OPERATION DESCRIPTION BL8835A is a high performance, multimode controlled, highly integrated QR (Quasi Resonant) Primary Side Regulation (PSR) controller. The built-in high precision CV/CC control with high level protection features make it very suitable for offline small power converter applications. ◆ Startup Current and Startup Control Startup current of BL8835A is designed to be very low (typically 2uA) so that VDD could be charged up above UVLO(ON) 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. ◆ Operating Current The operating current in BL8835A is as small as 0.65mA (typical). The small operating current results in higher efficiency and reduces the VDD hold-up capacitance requirement. ◆ QR/PSR Control BL8835A uses a proprietary QR/PSR control for high efficiency and low EMI. The IC works in Quasi-Resonant (QR) mode in Constant Current (CC) and Constant Voltage (CV) mode. In this way, the efficiency is boosted and the EMI is reduced greatly. The IC can easily meet EPS level 6 standard. ◆ Constant Current (CC) Regulation I CC (mA) N 500(mV ) 2 RCS () In the equation above, N---- The turn ratio of primary side winding to secondary side winding. Rcs---- The sensing resistor connected between the Source to GND. ◆ Precision CV/CC Performance In BL8835A, the parameters are trimmed to tight range, which makes the system CC/CV to have less than 5% variation. www.belling.com.cn 5/7 ◆ Soft Start BL8835A features an internal soft start that slowly increases the threshold of cycle-by-cycle current limiting comparator during startup sequence. It reduces the stress on the secondary diode during startup. Every startup process is followed by a soft start activation. ◆ Proprietary Cable Voltage Drop Compensation in CV Mode When it comes to cellular phone charger applications, the battery is located at the end of cable, which causes typically several percentage of voltage drop on the actual battery voltage. BL8835A has a proprietary built-in cable voltage drop compensation block which can provide a constant output voltage at the end of the cable over the entire load range in CV mode. ◆ Leading Edge Blanking (LEB) Each time the power MOSFET is switched on, a turn-on spike occurs across the sensing resistor. To avoid premature termination of the switching pulse, an internal leading edge blanking circuit is built in. During this blanking period (500ns, typical), the cycle-by-cycle current limiting comparator is disabled and cannot switch off the gate driver. Thus, external RC filter with a small time constant is enough for current sensing. ◆ Minimum and Maximum OFF Time In BL8835A, a minimum OFF time (typically 2us) is implemented to suppress ringing when GATE is off. The minimum OFF time is necessary in applications where the transformer has a large leakage inductance, particularly at low output voltages or startup. The maximum OFF time in BL8835A is typically 2.8ms, which provides a large range for frequency reduction. In this way, a low standby power of 100mW can be achieved. ◆ Output OVP(Over Voltage Protection) and Output UVP (Under Voltage Protection) In BL8835A, the output OVP is integrated by plateau sampling the auxiliary winding in flyback phase. The threshold voltage for output OVP is 2.4V, as shown in Fig.1 Output OVP is auto-recovery mode protection (mentioned below). In BL8835A, when sensed INV voltage is below 0.65V, the IC will enter into Under Voltage Protection (UVP) mode, in which the switching frequency is clamped, as shown in Fig.1 V1.0 BL8835A QR/PSR CV/CC Controller ◆ Pin Floating Protection In BL8835A, if pin floating situation occurs, the IC is designed to have no damage to system. ◆ Soft Gate Drive BL8835A has a soft totem-pole gate driver with optimized EMI performance. An internal 16V clamp is added for MOSFET gate protection at higher than expected VDD input. ◆ Gate Drive The internal power MOSFET in BL8835A is driven by a dedicated gate driver for power switch control. Too weak the gate drives strength results in higher conduction and switch loss of MOSFET while too strong gate drive compromises EMI. A good tradeoff is achieved through the built-in totem pole gate design with right output strength control. Fig.1 ◆ Programmable Cable drop Compensation Fig.1 ◆Frequency Clamping @ Output Short Circuit In BL8835A, when INV voltage is below 0.65V, the IC will enter into Under Voltage Protection (UVP) mode, the switching frequency is fixed to 50KHz (typical). This protection is useful for LED short circuit protection. When output is short, the frequency clamping can lower power MOSFET Vds spike and the system reliability can be improved. In BL8835A, when output short circuit occurs, the IC will fix the switching frequency to 50KHz. In this way, the power MOSFET Vds spike voltage is suppressed greatly. ◆VDD OVP(Over Voltage Protection) VDD OVP (Over Voltage Protection) is implemented in BL8835A and it is a protection of auto-recovery mode. ◆Auto Recovery Mode Protection Once a fault condition is detected, switching will stop. This will cause VDD to fall because no power is delivered form the auxiliary winding. When VDD falls to UVLO(off) (typical 9.0V), the protection is reset and the operating current reduces to the startup current, which causes VDD to rise. However, if the fault still exists, the system will experience the above mentioned process. If the fault has gone, the system resumes normal operation. In this manner, the auto restart can alternatively enable and disable the switching until the fault condition is disappeared. www.belling.com.cn 6/7 In BL8835A, cable drop compensation is implemented to achieve good load regulation. An offset voltage is generated at INV by an internal current flowing into the resister divider. The current is inversely proportional to the voltage across pin COMP, as a result, it is inversely proportional to the output load current, thus the drop due to the cable loss can be compensated. As the load current decreases from full-load to no load, the offset voltage at INV will increase. It can also be programmed by adjusting the resistance of the divider to compensate the drop for various cable lines used. ◆Protection Control Good power supply system reliability is achieved with its rich protection features including Cycle-by-Cycle current limiting (OCP), VDD clamp, Power on Soft Start, and Under Voltage Lockout on VDD (UVLO). VDD is supplied by transformer auxiliary winding output. The output of BL8835A is shut down when VDD drops below UVLO (ON) limit and Switcher enters power on start-up sequence thereafter. V1.0 BL8835A QR/PSR CV/CC Controller PACKAGE MECHANICAL DATA SOP8 PACKAGE OUTLINE DIMENSIONS Dimensions In Millimeters Dimensions In Inches Symbol Min Max Min Max A 1.350 1.750 0.053 0.069 A1 0.050 0.250 0.002 0.010 A2 1.250 1.650 0.049 0.065 B 0.310 0.510 0.012 0.020 C 0.170 0.250 0.006 0.010 D 4.700 5.150 0.185 0.203 E 3.800 4.000 0.150 0.157 E1 5.800 6.200 0.228 0.244 e 1.270(BSC) 0.05(BSC) L 0.400 1.270 0.016 0.050 θ 0° 8° 0° 8° www.belling.com.cn 7/7 V1.0