UNISONIC TECHNOLOGIES CO., LTD US3706 Preliminary CMOS IC CURRENT MODE PWM POWER SWITCH DESCRIPTION The UTC US3706 combines a dedicated current mode PWM controller with a high voltage power MOSFET. Low VDD startup current make the power reliable on startup design and a large value resistor could be used in the startup circuit to minimize the standby power. At no load condition, the IC operates in power-saving mode for lower standby power, decreasing frequency for Higher conversion efficiency at light load condition. The UTC US3706 offers complete protection coverage with automatic self-recovery feature including Cycle-by-Cycle current limiting (OCP), over load protection (OLP), over temperature protection (OTP), over voltage protection and VDD under voltage lockout (UVLO). The internal slope compensation improves system stability at high PWM duty cycle output. Leading-edge blanking on current sense input removes the signal glitch, which offering minimal external component count in the design. Excellent EMI performance is achieved with UTC proprietary frequency hopping technique (ZL201020615247.1) together with soft driver control. Audio noise is eliminated due to switch frequency more than 20kHz during operation. The US3706 has such applications as: battery charger, power adaptor, set-top box power supplies, ink jet printers, open-frame SMPS. TO-220F-6 FEATURES * UTC proprietary frequency hopping technology for Improved EMI performance. * Power-saving mode for high light-load and standby efficiency * Soft Start * Dynamic peak current limiting for constant output power * Built-in synchronized slope compensation 1 * OLP,OVPand OTP for higher security * Fixed switch frequency 65kHz * Low start-up current * Cycle-by-cycle Current Limiting * Under voltage lockout (UVLO) * Leading edge blanking on source input * Few external components required ORDERING INFORMATION Ordering Number Lead Free US3706L-TF6-T Halogen Free US3706G-TF6-T www.unisonic.com.tw Copyright © 2015 Unisonic Technologies Co., Ltd Package Packing TO-220F-6 Tube 1 of 8 QW-R129-001.b US3706 Preliminary MARKING PIN CONFIGURATION PIN DESCRIPTION PIN NO. PIN NAME 1 DRAIN 2 3 4 VDD Source RT 5 FB 6 GND CMOS IC DESCRIPTION HV MOSFET Drain Pin. The Drain pin is connected to the primary lead of the transformer. Supply voltage HV MOSFET Source Pin. Connected through a NTC resistor to ground for over temperature protection. Feedback input pin. The PWM duty cycle is determined by voltage level into this pin and the current-sense signal at Pin 3. Ground BLOCK DIAGRAM UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 2 of 8 QW-R129-001.b US3706 Preliminary CMOS IC ABSOLUTE MAXIMUM RATING PARAMETER SYMBOL RATINGS UNIT VDD Voltage -0.3~30 V FB Input Voltage -0.3~7 V Source Input Voltage -0.3~7 V Operating Junction Temperature TJ 150 °C Storage Temperature TSTG -55~150 °C Lead Temperature (Soldering, 10secs) TL 260 °C Note: Absolute maximum ratings are those values beyond which the device could be permanently damaged. Absolute maximum ratings are stress ratings only and functional device operation is not implied. ELECTRICAL CHARACTERISTICS (TA=25°C , VDD=16V, RT=100KΩ, unless otherwise noted) PARAMETER SUPPLY SECTION Start Up Current IC Operating current VDD Zener Clamp current UNDER-VOLTAGE LOCKOUT SECTION Start Threshold Voltage Min. Operating Voltage CONTROL SECTION VFB Open Loop Voltage Level Burst-Mode Out FB Voltage Reduce-Frequency end FB Voltage Burst-Mode Enter FB Voltage Normal Switch Frequency Power-Saving Duty Cycle Frequency Hopping Frequency VDD Stability Frequency Temperature Stability Feedback Resistor PROTECTION SECTION VCC Over Voltage Protection Threshold FB PIN Over Load Protection Threshold Power Limiting Debounce Time Soft start time CURRENT LIMITING SECTION Peak Current Flat Threshold Voltage Peak Current Valley Threshold Voltage Lead Edge Blanking Time RT SECTION Output current of RT pin Threshold voltage for OTP Mosfet Section MOSFET Drain-Source Breakdown Voltage Static Drain to Source On Resistance SYMBOL MIN TYP MAX UNIT 26 2.5 2.4 27.5 20 3.0 29 μA mA V VDD(ON) VDD(MIN) 12 7 13.5 8 15 9 V V VFB-OPEN VFB(OUT) VFB(END) VFB(IN) 4.9 5.1 1.6 2.2 1.5 60 22 77 5.3 V V V V KHz KHz % % % % KΩ V V mS mS ISTR IOP vCLAMP FSW DMAX FJ(SW) FDV FDT RFB VDD = VDD(ON)-0.1V VFB=3.5V IVDD=10mA VSENSE =0 VSENSE =0 VSENSE =0 VFB=3.5V Before enter burst mode VFB=3.5V, VSENSE=0 VFB=3.5V VCS-F VCS-V TLEB VFB=4.2V, Duty≥60% VFB=4.2V, Duty=0% IRT 55 17 70 -4 17 20 65 27 85 +4 5 10 23 22.5 4.6 100 1 23 4.8 125 2 24.5 5.0 150 3 VDD=12V~20V T=-20~100°C VOVP VOLP TD_PL TSS 0.8 0.7 350 VTH_OTP 90 0.9 BVdss 600 Rdson UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw TEST CONDITIONS 100 1 V V ns 110 1.1 uA V V 1.5 Ω 3 of 8 QW-R129-001.b US3706 Preliminary CMOS IC OPERATION DESCRIPTION The UTC US3706 is a low power off-line SMPS Switcher optimized for off-line flyback converter. It integrates many useful designs into one controller for low-power switch-mode power supplies. The following descriptions highlight some of the features of the US3706 series. Startup Current and Start up Control The start-up current is only 2.5μA. Low start-up current allows a start-up resistor with a high resistance and a low-wattage to supply the start-up power for the controller. For AC/DC adaptor with universal input range design, a 2.5~3MΩ, 1/8W startup resistor could be used together with a VDD capacitor to provide a fast startup and low power dissipation solution. Power-Saving Mode Operation The proprietary Power-Saving Mode function provides linearly decreasing the switching frequency under light-load conditions for higher efficiency. The feedback voltage, which is sampled from the voltage feedback loop, is taken as the reference. Once the feedback voltage dropped below the threshold voltage, the switching frequency starts to decrease. This Power-Saving Mode function dramatically reduces power consumption under light-load conditions. The 22KHz minimum frequency control also eliminates the audio noise at any loading conditions. At zero load condition, the magnitude of power loss is in proportion to the number of switching events within a fixed period of time. Reducing switching events leads to the reduction on the power loss and thus conserves the energy. The US3706 enter burst mode at standby condition to minimize the switching loss and reduces the standby power consumption. Power supplies using the US3706 can easily meet even the strictest regulations regarding standby power consumption. Switch Frequency Set The maximum switch frequency is fixed to 60KHz. Switch frequency is modulated by output power POUT during IC operating. At no load or light load condition, most of the power dissipation in a switching mode power supply is from switching loss on the MOSFET transistor, the core loss of the transformer and the loss on the snubber circuit. The magnitude of power loss is in proportion to the number of switching events within a fixed period of time. So lower switch frequency at lower load, which more and more improve IC’s efficiency at light load. At from no load to light load condition, The IC will operate at from Burst mode to Reducing Frequency Mode. The relation curve between fSW and POUT/POUT (MAX) as followed Fig.1. 70 1%~100% Load @ 115 & 230 Vac 60 55 115V 40 230V 25 10 1% 9% 19% 30% 100% POUT/POUT(max) Fig.1 The relation curve between fSW and relative output power POUT/ POUT (MAX) UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 4 of 8 QW-R129-001.b US3706 Preliminary CMOS IC OPERATION DESCRIPTION (Cont.) Frequency Hopping For EMI Improvement The Frequency hopping is implemented in the IC; there are two oscillators built-in the IC. The first oscillator is to set the normal switching frequency; the switching frequency is modulated with a period signal generated by the 2nd oscillator. The relation between the first oscillator and the 2nd oscillator as followed Fig.2. So the tone energy is evenly spread out, the spread spectrum minimizes the conduction band EMI and therefore eases the system design in meeting stringent EMI requirement. Fig.2 Frequency Hopping Built-in Slope Compensation Built-in slope compensation circuit greatly improves the close loop stability at CCM and prevents the sub-harmonic oscillation. Leading-Edge Blanking Each time the power MOSFET is switched on, a turn-on spike will inevitably occur at the sense-resistor. To avoid premature termination of the switching pulse, a 400ns leading-edge blanking time is built in. Conventional RC filtering can therefore be omitted. During this blanking period, the current-limit comparator is disabled and it cannot switch off the power MOSFET. Under Voltage Lockout (UVLO) The turn-on and turn-off thresholds of the US3706 are fixed internally at VDD(ON)/VDD(MIN) During start-up, the hold-up capacitor must be charged to VDD(ON) through the start-up resistor, so that the US3706 will be enabled. The hold-up capacitor will continue to supply VDD until power can be delivered from the auxiliary winding of the main transformer. VDD must not drop below VDD(MIN) during this start-up process. This UVLO hysteresis window ensures that hold-up capacitor will be adequate to supply VDD during start-up. UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 5 of 8 QW-R129-001.b US3706 Preliminary CMOS IC OPERATION DESCRIPTION (Cont.) Protection Controls The IC takes on more protection functions such as OVP, OLP and OTP etc. In case of those failure occurs for continual blanking time, the power MOSFET is shut down. Power MOSFET is reset after failure is eliminated. OVP The OVP will shut down the switching of the power MOSFET whenever VDD >VOVP. The OVP event as followed Fig.3. Fig.3 OVP case Fig.4 OLP case OLP OLP will shut down driver when VFB> VOLP for continual a blanking time. The OLP event as followed Fig.4. OTP OTP will shut down driver when the NTC resistor temperature TJ>T (THR). UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 6 of 8 QW-R129-001.b US3706 Preliminary CMOS IC TYPICAL APPLICATION CIRCUIT L N LF1 F1 3 1 4 2 R1 R2 LF2 3 3 4 1 4 2 R40 C40 T1 4 BD1 + 1 R6 C1 2 C2 + R7 L1 VOUT+ R8 2 D5 C41 + C43 C42 + B R23 VOUT GND 5 8 D1 R13 C7 9 D3 4 C10 U1 U3 6 GND DRAIN 1 5 VDD 2 FB 4 RT SOURCE 3 C6 R41 RM-8 + 3 1 R45 R42 R43 2 C45 C46 C12 U4 R12 C5 R46 RT1 BOM Reference BD1 C2 C3 C6 C10 C7, C46 C11 C43 C45 CX1 CY1 R21 R20 Component 2A_600V Capacitor, aluminum electrolytic,33uF/400V, 105℃,±20% Capacitor, ceramic, 1000pF/1KV, NPO, SMD1206 Capacitor, ceramic, 1nF/50V, X7R, SMD0805 Capacitor, aluminum electrolytic,10uF/50V; 105℃,±20% Capacitor, ceramic, 0.1uF/50V, X7R, SMD0805 Capacitor, ceramic, 68pF/50V, X7R, SMD0805 Capacitor, aluminum electrolytic, 680uF/25V, 105℃,±20% Capacitor, ceramic, 10NF/50V, X7R, SMD0805 Capacitor, X2, 0.33uF/275VAC, 105℃ ,±20% Capacitor, Y1, 1000pF/400V, 105℃,±20% D5 Capacitor, ceramic, 100pF/200V, ±20%, SMD1206 Diode , fast recovery, 1N4007, 1.0A/1000V Diode , fast recovery, BAV20WG, SOT-123 Diode, MGBR20L60CG, 20A/60V,TO-220 F1 Fuse, 3.15A / 250V C40 D1 D3 LF1, LF2 choke UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw R47 CY1 R22 Reference R6, R2 Component Resistor, chip,1.5M, 1/4W,±5%, SMD1206 R7, R8 Resistor, chip,180K, 1/4W,±5%, SMD1206 R13 Resistor, chip,4.7-, 1/8W,±5%, SMD0805 R18 Resistor, chip,1K, 1/8W,±5%, SMD0805 R20, R21 Resistor, chip, 1.8-, 1/4W,±5%, SMD1206 R40 Resistor, chip, 47-, 1/4W,±5%, SMD1206 R41 Resistor, chip,820-, 1/10W,±5%, SMD0603 R42 Resistor, chip,2.2K, 1/10W,±5%, SMD0603 R43 Resistor, chip,300-, 1/10W,±1%, SMD0603 R45 Resistor, chip,39K, 1/10W,±1%, SMD0603 R47 Resistor, chip,10K, 1/10W,±1%, SMD0603 T1 Transformer, RM-8 U1 IC, PWM controller, UTC US3706, TO-220F-6 U4 IC, TL431 SOT-23 U3 No Component PCB IC, Opto-Coupler, LTV-357-T-C, SMD C1, C41, C42, C5, R1, R2, R3, R5, R12, R22, R47 32mmX71mmX1.6mm 7 of 8 QW-R129-001.b US3706 Preliminary CMOS IC UTC assumes no responsibility for equipment failures that result from using products at values that exceed, even momentarily, rated values (such as maximum ratings, operating condition ranges, or other parameters) listed in products specifications of any and all UTC products described or contained herein. UTC products are not designed for use in life support appliances, devices or systems where malfunction of these products can be reasonably expected to result in personal injury. Reproduction in whole or in part is prohibited without the prior written consent of the copyright owner. The information presented in this document does not form part of any quotation or contract, is believed to be accurate and reliable and may be changed without notice. UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 8 of 8 QW-R129-001.b