CR623X—CR6235/6236/6238 High Precision CC/CV Primary-Side PWM Power Switch Features z z z z z z z 5% Constant Voltage Regulation, 5% Constant Current Regulation at Universal AC input Primary-side Sensing and Regulation Without TL431 and Opto-coupler Power on Soft-start Built-in Leading Edge Blanking (LEB) Cycle-by-Cycle Current Limiting VDD Under Voltage Lockout with Hysteresis (UVLO) Programmable CV and CC Regulation z z z Adjustable Constant Current and Output Power Setting Built-in Secondary Constant Current Control with Primary Side Feedback Built-in adaptive current peak regulation Built-in Primary winding inductance compensation Program cable drop compensation VDD OVP and VDD Clamp Pb-free SOP-8L & DIP-8L z z Auxiliary Power for PC, TV etc. Linear Regulator/RCC Replacement z z z z Applications z z Cell Phone /Digital Cameras Charger Small Power Adaptor General Description CR623X is a high performance offline PWM Power switch for low power AC/DC charger and adaptor applications. It operates in primary-side sensing and regulation. Consequently, opto-coupler and TL431 could be eliminated. Proprietary Constant Voltage (CV) and Constant Current (CC) control is integrated as shown in the Fig.1. In CC control, the current and output power setting can be adjusted externally by the sense resistor RS at CS pin. In CV control, multi-mode operations are utilized to achieve high performance and high efficiency. In addition, good load regulation is achieved by the built-in cable drop compensation. Device operates in PFM in CC mode as well at large load condition and it operates in PWM with frequency reduction at light/medium load. Sep, 2009 V1.6 CR623X offers power on soft start control and protection coverage with auto-recovery features including Cycle-by-Cycle current limiting, VDD OVP, VDD clamp and UVLO. Excellent EMI performance is achieved with frequency jitter technique. Fig.1. Typical CC/CV Curve 1/10 CR623X High Precision CC/CV Primary-Side PWM Power Switch Pin Assignment （SOP-8L & DIP-8L ） Pin Description Pin Num 1 2 Pin Name VDD COMP 3 INV 4 CS 5/6 DRAIN 7/8 GND 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 Typical Application Vo AC NP NS NAUX VDD GND COMP GND INV DRAIN CS DRAIN CR623X Sep, 2009 V1.6 2/10 CR623X High Precision CC/CV Primary-Side PWM Power Switch Block Diagram Simplified Internal Circuit Architecture Absolute Maximum Ratings Parameter Value Drain Voltage (off state) -0.3V to Bvdss VDD Voltage -0.3 to VDD_clamp VDD Zener Clamp Continuous Current 10 mA COMP Voltage -0.3 to 7V CS Input Voltage -0.3 to 7V INV Input Voltage -0.3 to 7V Min/Max Operating Junction Temperature TJ -20 ℃to 150℃ Min/Max Storage Temperature Tstg -55 ℃to 150℃ Lead Temperature (Soldering, 10secs) 260℃ Note: Stress beyond those listed under “absolute maximum ratings” may cause permanent damage to the device. Exposure to absolute maximum-rated conditions for extended periods may affect device reliability. Output Power Table Product Package CR6235 CR6236 CR6238 SOP-8L DIP-8L DIP-8L 230VAC ±15% Adapter1 6W 8W 15W 85-265VAC Adapter 1 5W 7W 13W Notes: 1. Maximum practical continuous power in an open frame design with sufficient drain pattern as a heat sink, at 50℃ ambient. Sep, 2009 V1.6 3/10 CR623X High Precision CC/CV Primary-Side PWM Power Switch Electrical Characteristics (Ta=25°C unless otherwise noted, VDD = 16V) Symbol Parameter Test Conditions Min Typ Max Unit 5 20 uA 2.5 3.5 mA Supply Voltage (VDD) Section IDD_ST Standby current VDD=13V Operation IDD_OP Operation Current supply current INV=2V,CS=0V, VDD=VDDG=20V VDD Under Voltage Lockout UVLO(ON) Enter UVLO(OFF) VDD Under Voltage Lockout Exit Over OVP voltage protection voltage 7.5 8.5 10 V VDD rising 13.5 14.5 16.0 V 27.5 29.5 31.5 V 30.5 32.5 34.5 V Ramp up VDD until gate clock is off Maximum VDD opertation VDD_clamp VDD falling voltage IDD=10mA Current Sense Input Section TLEB LEB time 540 Vth_oc Over current threshold Td_oc OCP Propagation delay 150 ns Input Impedance 50 Kohm Soft start time 10 ms ZSENSE_IN T_ss 870 900 ns 930 mV CV Section System Freq_Nom Nominal switch Freq_startup △f/Freq 60 frequency INV=0V,Comp=5V Frequency jitter range 14 KHZ +/-4 % Error Amplifier section Vref_EA Gdc Reference voltage for EA DC gain of the EA Max. Cable compensation I_COMP_MAX 1.97 current INV=2V,COMP=0V 2 2.03 V 60 dB 42 uA 650 V Power MOSFET Section BVdss RDS(on) Sep, 2009 MOSFET Drain-Source Breakdown Voltage Static Drain to Source On Resistance V1.6 CR6235S 12 15 Ω CR6236T 9.2 12 Ω CR6238T 3.0 3.6 Ω 4/10 CR623X High Precision CC/CV Primary-Side PWM Power Switch Operation Description CR623X is a cost effective PWM power switch optimized for off-line low power AC/DC applications including battery chargers and adaptors. It operates in primary side sensing and regulation, thus opto-coupler and TL431 are not required. Proprietary built-in CV and CC control can achieve high precision CC/CV control meeting most adaptor and charger application requirements. Startup Current and Start up Control Startup current of CR623X is designed to be very low so that VDD could be charged up above UVLO threshold and starts up quickly. A large value startup resistor can therefore be used to minimize the power loss in application. Operating Current The Operating current of CR623X is as low as 2.5mA. Good efficiency is achieved with the low operating current together with Multi-mode control features. Soft Start CR623X features an internal soft start to minimize the component electrical over-stress during power on startup. As soon as VDD reaches UVLO (OFF), the control algorithm will ramp peak current voltage threshold gradually from nearly zero to normal setting of 0.90V. Every restart is a soft start. CC/CV Operation CR623X is designed to produce good CC/CV control characteristic as shown in the Fig. 1. In charger applications, a discharged battery charging starts in the CC portion of the curve until it is nearly full charged and smoothly switches to operate in CV portion Sep, 2009 V1.6 of the curve. In an AC/DC adapter, the normal operation occurs only on the CV portion of the curve. The CC portion provides output current limiting. In CV operation, the output voltage is regulated through the primary side control. In CC operation mode, CR623X will regulate the output current constant regardless of the output voltage drop. Principle of Operation To support CR623X proprietary CC/CV control, system needs to be designed in DCM mode for flyback system (Refer to Typical Application Diagram). In the DCM flyback converter, the output voltage can be sensed via the auxiliary winding. During MOSFET turn-on time, the load current is supplied from the output filter capacitor CO. The current in the primary winding ramps up. When MOSFET turns off, the primary current transfers to the secondary at the amplitude of IS = NP ⋅ IP NS The auxiliary voltage reflects the output voltage as shown in fig.2 and it is given by VAUX = N AUX ⋅ (VO + ΔV) NS Where ΔV indicates the drop voltage of the output Diode. Fig.2. Auxiliary voltage waveform 5/10 CR623X High Precision CC/CV Primary-Side PWM Power Switch Via a resistor divider connected between the auxiliary winding and INV (pin 3), the auxiliary voltage is sampled at the end of the demagnetization and it is hold until the next sampling. The sampled voltage is compared with Vref (2.0V) and the error is amplified. The error amplifier output COMP reflects the load condition and controls the PWM switching frequency to regulate the output voltage, thus constant output voltage can be achieved. When sampled voltage is below Vref and the error amplifier output COMP reaches its maximum, the switching frequency is controlled by the sampled voltage thus the output voltage to regulate the output current, thus the constant output current can be achieved. Adjustable CC point and Output Power In CR623X, the CC point and maximum output power can be externally adjusted by external current sense resistor RS at CS pin as illustrated in Typical Application Diagram. The output power is adjusted through CC point change. The larger RS, the smaller CC point is, and the smaller output power becomes, and vice versa as shown in Fig.3. external frequency setting components are required. The operation switching frequency at maximum output power is set to 60KHz internally. For flyback operating in DCM, The maximum output power is given by Po MAX = 1 2 L P FSW I P 2 Where LP indicate the inductance of primary winding and IP is the peak current of primary winding. Refer to the equation 3, the change of the primary winding inductance results in the change of the maximum output power and the constant output current in CC mode. To compensate the change from variations of primary winding inductance, the switching frequency is locked by an internal loop such that the switching frequency is FSW = 1 2TDemag Since TDemag is inversely proportional to the inductance, as a result, the product LP and Fsw is constant, thus the maximum output power and constant current in CC mode will not change as primary winding inductance changes. Up to +/-10% variation of the primary winding inductance can be compensated. Frequency jitter for EMI improvement The frequency jitter (switching frequency modulation) is implemented in CR623X. The oscillation frequency is modulated so that the tone energy is spread out. The spread spectrum minimizes the conduction band EMI and therefore eases the system design. Fig.3. Adjustable output power by changing RS Operation switching frequency The switching frequency of CR623X is adaptively controlled according to the load conditions and the operation modes. No Sep, 2009 V1.6 Current Sensing and Leading Edge Blanking Cycle-by-Cycle current limiting is offered in CR623X current mode PWM control. The switch current is detected by a sense resistor into the CS pin. An internal leading 6/10 CR623X High Precision CC/CV Primary-Side PWM Power Switch edge blanking circuit chops off the sensed voltage spike at initial internal power MOSFET on state so that the external RC filtering on sense input is no longer needed. The PWM duty cycle is determined by the current sense input voltage and the EA output voltage. winding output. The output of CR623X is shut down when VDD drops below UVLO (ON) limit and Switcher enters power on start-up sequence thereafter. Gate Drive The internal power MOSFET in CR623X is driven by a dedicated gate driver for power switch control. Too weak the gate drive 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. Programmable Cable drop Compensation In CR623X, 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 Sep, 2009 V1.6 7/10 CR623X High Precision CC/CV Primary-Side PWM Power Switch Characterization Plots The characteristic graphs are normalized at TA=25℃. UVLO(off)(V) VS TEMP(C) 9.5 15.5 9 15 UVLO(off) (V) UVLO(on) (V) UVLO(on)(V) VS TEMP(C) 8.5 8 7.5 -40 -10 20 50 Temperature( C) 80 110 14.5 14 13.5 -40 125 -10 20 75 2.5 70 2 1.5 1 -40 -10 20 50 110 125 80 110 65 60 55 -40 125 -10 20 50 80 110 125 Tempterature(C) Temperature(C) I_cable_compensation (uA) vs Vcomp(V) Rdson(ohm) vs Temperature( C) 45 I_cable_compensation (uA) 35 30 25 Rdson(ohm) 80 Freq_Max (KHz) VS TEMP(C) 3 Freq_Max (KHz) Istartup (uA) Istartup (uA) VS TEMP(C) 50 Temperature(C) 20 15 10 5 40 35 30 25 20 15 10 5 0 0 25 Sep, 2009 50 V1.6 75 100 Tempterature( C) 125 150 0 1 2 3 4 Vcomp (V) 8/10 CR623X High Precision CC/CV Primary-Side PWM Power Switch Package Information DIP-8L Symbol Millimeters Min. Typ. A 0.381 A2 3.175 b Typ. 0.015 3.302 3.429 0.125 9.271 6.223 6.350 0.130 0.135 0.060 0.018 10.160 0.355 7.620 e Max. 0.210 0.457 9.017 E Sep, 2009 Min. 1.524 b1 E1 Max. 5.334 A1 D Inches 0.365 0.400 0.300 6.477 0.245 2.540 0.250 0.255 0.100 L 2.921 3.302 3.810 0.115 0.130 0.150 eB 8.509 9.017 9.525 0.335 0.355 0.375 θ˚ 0˚ 7˚ 15˚ 0˚ 7˚ 15˚ V1.6 9/10 CR623X High Precision CC/CV Primary-Side PWM Power Switch SOP-8L Symbol Min. Max. Min. Inch Typ. Max. A 1.346 1.752 0.053 0.069 A1 0.101 0.254 0.004 0.010 b 0.406 0.016 c 0.203 0.008 D 4.648 4.978 0.183 E 3.810 3.987 0.150 e 1.016 1.524 0.040 F Sep, 2009 Millimeter Typ. 1.270 0.381X45 ° 0.196 0.157 0.050 0.015X45 ° 0.060 H 5.791 6.197 0.228 0.244 L 0.406 1.270 0.016 0.050 θ˚ 0° 8° 0° 8° V1.6 10/10