LD7750R 05/12/2010 High Voltage Green-Mode PWM Controller with Over Temperature Protection Rev. 00 Features General Description The LD7750R integrates several functions of protections, z High-Voltage (500V) Startup Circuit and EMI-improved solution in a SOP-7, SOP-8 or DIP-8 z Current Mode Control package to minimize the component counts and the circuit z Green Mode Control space. z UVLO (Under Voltage Lockout) z LEB (Leading-Edge Blanking) on CS Pin z Internal Frequency Swapping z Internal Slope Compensation z Internal Over Current Protection z OVP (Over Voltage Protection) on Vcc z OLP (Over Load Protection) z External OTP through a NTC z 500mA Driving Capability The device provides functions of low startup current, green-mode power-saving operation, leading-edge blanking of the current sensing and internal slope compensation. Also, the LD7750R features more protections like OLP (Over Load Protection), OVP (Over Voltage Protection), and OTP (Over Temperature Protection) to prevent the circuit being damaged under the abnormal conditions. The LD7750R features built-in Applications auto-recovery function for OVP on Vcc pin and OLP. z Switching AC/DC Adaptor and Battery Charger z Open Frame Switching Power Supply z LCD Monitor/TV Power Typical Application 1 Leadtrend Technology Corporation LD7750R-DS-00 May 2010 www.leadtrend.com.tw LD7750R Pin Configuration NC VCC 5 8 7 6 6 OUT HV 7 SOP-8 /DIP-8 (TOP VIEW) OUT HV VCC SOP-7 (TOP VIEW) 5 4 1 OTP 2 3 4 GND 3 CS 2 YY: WW: PP: C OMP 1 GND YYWWPP CS YYWWPP COMP TOP MARK OTP TOP MARK Year code Week code Production code Ordering Information Part number Switching Freq. Package LD7750R GS 65kHz SOP-8 Green package LD7750R GS 2500 /tape & reel LD7750R GR 65kHz SOP-7 Green package LD7750R GR 2500 /tape & reel DIP-8 LD7750R GN 3600 /tube /Carton LD7750R GN 65kHz The LD7750R is ROHS compliant. Top Mark Green package Shipping Protection Mode Part number Switching Freq. VCC OVP OLP OTP Pin LD7750R 65kHz Auto recovery Auto recovery Latch Pin Descriptions SOP-8 SOP-7 NAME FUNCTION Pulling this pin below 0.95V will shutdown the controller to enter latch 1 1 OTP mode until the AC power-on recycles. Connecting a NTC between this pin and ground will achieve OTP protection function. Let this pin float to disable the latch protection. Voltage feedback pin. By connecting a photo-coupler to close the 2 2 COMP 3 3 CS 4 4 GND Ground. 5 5 OUT Gate drive output to drive the external MOSFET. 6 6 VCC Supply voltage pin. NC Unconnected Pin. 7 control loop can achieve the regulation. Current sense pin, for sensing the MOSFET current. Connect this pin to a positive terminal of bulk capacitor to provide the 8 7 HV startup current for the controller. When Vcc voltage trips the UVLO(on), this HV loop will be turned off to reduce the power loss on the startup circuit. 2 Leadtrend Technology Corporation LD7750R-DS-00 May 2010 www.leadtrend.com.tw LD7750R Block Diagram 3 Leadtrend Technology Corporation LD7750R-DS-00 May 2010 www.leadtrend.com.tw LD7750R Absolute Maximum Ratings Supply Voltage VCC -0.3V~30V High-Voltage Pin, HV -0.3V~500V COMP, OTP, CS -0.3 ~7V OUT -0.3 ~Vcc+0.3 Maximum Junction Temperature 150°C Operating Ambient Temperature -20°C to 85°C Operating Junction Temperature -40°C to 125°C Storage Temperature Range -65°C to 150°C Package Thermal Resistance (SOP-7/ SOP-8) 160°C/W Package Thermal Resistance (DIP-8) 100°C/W Power Dissipation (SOP-7/ SOP-8, at Ambient Temperature = 85°C) 400mW Power Dissipation (DIP-8, at Ambient Temperature = 85°C) 650mW Lead temperature (Soldering, 10sec) 260°C ESD Voltage Protection, Human Body Model (except HV Pin) 2.5KV ESD Voltage Protection, Machine Model 250V Gate Output Current 500mA Caution: Stresses beyond the ratings specified in “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress only rating and operation of the device at these or any other conditions above those indicated in the operational sections of this specification is not implied. 4 Leadtrend Technology Corporation LD7750R-DS-00 May 2010 www.leadtrend.com.tw LD7750R Electrical Characteristics (TA = +25°C unless otherwise stated, VCC=15.0V) PARAMETER CONDITIONS MIN TYP MAX UNITS 0.5 1.0 1.5 mA 35 μA 400 μA High-Voltage Supply (HV Pin) High-Voltage Current Source VCC< UVLO(on), HV=500V Off-State Leakage Current VCC> UVLO(off), HV=500V Supply Voltage (Vcc Pin) Startup Current 200 320 VCOMP=0V 1.2 mA Operating Current VCOMP=3V, 2.3 mA (with 1nF load on OUT pin) OLP tripped 0.61 mA OVP tripped, VCC=OVP 0.70 mA UVLO (off) 9.0 10.0 11.0 V UVLO (on) 15.0 16.0 17.0 V OVP Level 25.0 26.0 27.0 V 0.32 mA Voltage Feedback (COMP Pin) Short Circuit Current VCOMP=0V 0.20 0.26 Open Loop Voltage COMP pin open 5.5 6.0 V Green Mode Threshold VCOMP 2.75 V Zero Duty 1.8 V Current Sensing (CS Pin) Maximum Input Voltage, Vcs_off 0.80 Leading Edge Blanking Time 250 Input impedance 1 Delay to Output LD7750R-DS-00 May 2010 www.leadtrend.com.tw 0.90 V ns MΩ 100 5 Leadtrend Technology Corporation 0.85 ns LD7750R Electrical Characteristics (TA = +25°C unless otherwise stated, VCC=15.0V) PARAMETER CONDITIONS MIN TYP MAX UNITS Oscillator for Switching Frequency Frequency 61.0 Green Mode Frequency Trembling Frequency ° ° Temp. Stability -20 C~85 C Voltage Stability (VCC=11V-25V) 65.0 69.0 KHz 20 KHz ±4 kHz 5 % 1 % OTP Pin Latch Protection (OTP Pin) 92 100 108 μA Turn-On Trip Level 1.00 1.05 1.10 V Turn-Off Trip Level 0.90 0.95 1.0 V OTP Pin Source Current De-latch VCC Level (PDR, Power Down Reset) 8.0 V Gate Drive Output (OUT Pin) Output Low Level VCC=15V, Io=20mA Output High Level VCC=15V, Io=20mA Rising Time Load Capacitance=1000pF 100 160 ns Falling Time Load Capacitance=1000pF 30 60 ns 5.0 5.2 V 1 9 V V OLP (Over Load Protection) OLP Trip Level 4.8 OLP Delay Time 64 ms 2 ms OTP Level 140 °C OTP Hysteresis 30 °C Soft Start Duration Soft Start Duration On Chip OTP (Internal Over Temperature Protection, Auto-Recovery) 6 Leadtrend Technology Corporation LD7750R-DS-00 May 2010 www.leadtrend.com.tw LD7750R Typical Performance Characteristics 0.88 0.87 1.3 VCS (off) (V) HV Current Source (mA) 1.5 1.1 0.86 0.85 0.9 0.84 0.7 -40 0 40 80 0.83 120 125 -40 Temperature (°C) UVLO (off) (V) UVLO (on) (V) 120 125 11.2 17.2 16.4 15.6 10.4 9. 6 8.8 14.8 8 -40 0 40 80 120 125 -40 Temperature (°C) Fig. 3 UVLO (on) vs. Temperature 0 40 80 120 125 120 125 Temperature (°C) Fig. 4 UVLO (off ) vs. Temperature 70 25 68 23 Frequency (KHz) Frequency (KHz) 80 12 18.0 66 64 21 19 17 62 60 40 Temperature (°C) Fig. 2 VCS (off) vs. Temperature Fig. 1 HV Current Source vs. Temperature (HV=500V, Vcc=0V) 14.0 0 -40 0 40 80 120 15 125 -40 80 Fig. 6 Green Mode Frequency vs. Temperature 7 LD7750R-DS-00 May 2010 40 Temperature (°C) Temperature (°C) Fig. 5 Frequency vs. Temperature Leadtrend Technology Corporation 0 www.leadtrend.com.tw LD7750R 25 Green mode frequency (KHz) 70 Frequency (KHz) 68 66 64 62 12 14 16 18 20 22 24 19 17 14 16 18 20 22 Vcc (V) Fig. 7 Frequency vs. Vcc Fig. 8 Green mode frequency vs. Vcc 85 35 80 30 75 70 24 25 120 125 25 20 15 60 -40 0 40 80 10 120 125 -40 0 40 80 Temperature (°C) Temperature (°C) Fig. 9 Max Duty vs. Temperature Fig. 10 VCC OVP vs. Temperature 6.0 6.5 5.5 6.0 5.0 OLP (V) 7.0 5.5 5.0 4.5 12 Vcc (V) 65 VCOMP (V) 21 15 11 25 VCC OVP (V) Max Duty (%) 60 11 23 4.5 4.0 -40 0 40 80 3.5 120 125 -40 Temperature (°C) 8 LD7750R-DS-00 May 2010 40 80 Temperature (°C) Fig. 12 OLP-Trip Level vs. Temperature Fig. 11 VCO MP open loop voltage vs. Temperature Leadtrend Technology Corporation 0 www.leadtrend.com.tw 120 125 LD7750R Application Information signal, disable the high-voltage current source, and the Operation Overview Vcc supply current will be only provided from the auxiliary winding of the transformer. As green power requirements become a trend and the Therefore, the power loss for the startup circuit after the startup period can be power saving gets more and more important for the eliminated and the power saving can be easily achieved. switching power supplies and switching adaptors, the In traditional PWM controllers are not able to support such general application, a 39KΩ resistor is still recommended to be placed in high voltage path to limit new requirements. Furthermore, the cost and size the current if there is a negative voltage applying in any limitations force PWM controllers to be more powerful by case. integrating more functions and, thus, reducing the LD7750R is designed for such An UVLO comparator is included to detect the voltage of application to provide an easy and cost effective solution. the VCC pin to ensure the supply voltage is high enough to Its detailed features are described as below. power on the LD7750R PWM controller and in addition to external part count. drive the power MOSFET as well. As shown in Fig. 14, a Internal High-Voltage Startup Circuit and Hysteresis is provided to prevent the shutdown caused by Under Voltage Lockout (UVLO) the voltage dip during startup. The turn-on and turn-off threshold levels are set at 16V and 10.0V, respectively. The traditional circuits power on the PWM controller through a startup resistor to constantly provide current from a rectified voltage to the capacitor connected to Vcc pin. Nevertheless, this startup resistor was usually of larger resistance, and it therefore consumed more power and required longer time to start up. To achieve an optimized topology, as shown in Fig. 13, The LD7750R is built in with high voltage startup circuit to optimize the power saving. During the startup sequence, a high-voltage current source sinks current from CBULK capacitor to provide the startup current as well as to Fig. 13 charge the Vcc capacitor C1. During the initialization of the startup, Vcc voltage is below UVLO(off) threshold thus the current source is on to supply a current of 1mA. Meanwhile, as the Vcc current consumed by the LD7750R is only 320μA thus most of the HV current is left to charge the Vcc capacitor. With using such configuration, the turn-on delay time will be almost the same no matter what operation condition is under low-line or high-line. When Vcc voltage reaches UVLO(on) threshold, the LD7750R is powered on to start issuing the gate drive 9 Leadtrend Technology Corporation LD7750R-DS-00 May 2010 www.leadtrend.com.tw LD7750R R-C filter (as shown in Fig. 16) for higher power applications to avoid the CS pin being damaged by the negative turn-on spike. Fig. 14 Current Sensing, Leading-edge Blanking and the Negative Spike on CS Pin Fig. 15 The typical current mode PWM controller feedbacks both current signal and voltage signal to close the control loop and achieve regulation. The LD7750R detects the primary MOSFET current from the CS pin, which is not only for the peak current mode control but also for the pulse-by-pulse current limit. The maximum voltage threshold of the current sensing pin is set as 0.85V. Thus the MOSFET peak current can be calculated as: IPEAK(MAX) = 0.85V RS A 250nS leading-edge blanking (LEB) time is included in the input of CS pin to prevent false-trigger caused by the current spike. For low power applications, if the total pulse width of the turn-on spike is less than 250nS and the negative spike on the CS pin is above -0.3V, the R-C filter (as shown in Fig.15) is eliminatable. However, the total pulse width of the turn-on spike is related to the output power, circuit design and PCB layout. Fig. 16 Nevertheless, it is strongly recommended to add a small 10 Leadtrend Technology Corporation LD7750R-DS-00 May 2010 www.leadtrend.com.tw LD7750R Oscillator and Switching Frequency On/Off Control The LD7750R is implemented with Frequency Swapping The LD7750R can be turned off by pulling COMP pin to function which helps the power supply designers to both below 1.8V. optimize EMI performance and minimize the system disabled immediately under such condition. The off-mode cost. The switching frequency substantially centers at can be released when the pull-low signal is removed. The gate output pin of LD7750R will be 65KHz, and swaps between a range of ±4KHz. Green-Mode Operation Output Stage and Maximum Duty-Cycle By using the green-mode control, the switching frequency An output stage of a CMOS buffer with driving capability can be reduced under the light load condition. This feature of 500mA typically is incorporated to drive a power helps to improve the efficiency in light load conditions. MOSFET directly. The green-mode control is Leadtrend Technology’s own And the maximum duty-cycle of IP. LD7750R is limited to 75% to avoid the transformer saturation. Over Load Protection (OLP) - Auto Voltage Feedback Loop Recovery The voltage feedback signal is provided from the TL431 in To protect the circuit from damage due to overload the secondary side through the photo-coupler to the condition or output short condition, a smart OLP function COMP pin of LD7750R. The input stage of LD7750R, is implemented in the LD7750R for it. The OLP function is like the UC384X, is incorporated with 2 diodes voltage an auto-recovery type protection. Fig. 17 shows the offset circuit and a voltage divider with 1/3 ratio. waveforms of the OLP operation. Therefore, condition, the feedback system will force the voltage loop 1 V+ (PWM COMPARATOR ) = × ( VCOMP − 2VF ) 3 Under such fault toward saturation and thus pull up the voltage of COMP pin (VCOMP). If the VCOMP trips the OLP threshold of A pulled-high resistor is embedded internally and thus no 5.0V and stays for over 63mS, the protection will be external one is required. activated to turn off the gate output and to shutdown the switching of power circuit. The 30mS delay time is to prevent the false-trigger during the power-on and turn-off Internal Slope Compensation transient. Stability is crucial for current mode control when it A divided-by-2 counter is implemented to reduce the operates at more than 50% of duty-cycle. To stabilize the average power consumption under OLP behavior. control loop, the slope compensation is required in the Whenever OLP is activated, the output is latched off and traditional UC384X design by injecting the ramp signal the divided-by-2 counter starts to count the number of from the RT/CT pin through a coupling capacitor. In the UVLO(off). The latch will be released if the 2nd UVLO(off) LD7750R, the internal slope compensation circuit has point is counted, and then the output recovers switching been implemented to simplify the external circuit design. again. By using such protection mechanism, the average input power can be reduced to a very low level so that the 11 Leadtrend Technology Corporation LD7750R-DS-00 May 2010 www.leadtrend.com.tw LD7750R VCC component temperature and stress can be controlled OVP Tripped within a safe operating area. OVP Level UVLO(on) UVLO(off) t OUT Switching Non-Switching Switching t Fig. 18 OTP Pin --- Latched Mode Protection To protect the power circuit from damage due to system failure, over temperature protection (OTP) is required. The OTP circuit is implemented to sense a hot-spot of power Fig. 17 circuit like power MOSFET or output rectifier. It can be easily achieved by connecting a NTC with OTP pin. As the device temperature or ambient temperature rises, the OVP (Over Voltage Protection) on Vcc- Auto resistance of NTC decreases. So, the voltage on the OTP Recovery pin could be written as below. The VGS ratings of the nowadays power MOSFETs are VOTP = 100μA ⋅ R NTC mostly 30V maximum. To protect the VGS from the fault When the VOTP falls below the defined threshold (typ. condition, LD7750R is implemented with OVP function at Vcc. 0.95V), LD7750R will shut down the gate output and then Once the Vcc voltage is larger than the OVP latch off the power supply. threshold voltage, the output gate drive circuit will be shut The controller will remain latched unless the Vcc drops below 8V (power down reset) down simultaneously and stop switching of the power and the fault condition is removed at the same time. MOSFET until the next UVLO(ON). There are 2 conditions required to restart it successfully. The Vcc OVP function in LD7750R is an auto-recovery First, cool down the circuit so that NTC resistance will type protection. If the OVP condition, usually caused by increase and raise VOTP above 1.05V. Then, remove the open feedback loop, is not released, the Vcc will trip the AC power cord and restart AC power-on recycling. The OVP level again and shutdown the output. The Vcc is detailed operation is depicted in Fig. 19. working in hiccup mode. Fig. 18 shows its operation. Once the OVP condition is removed, the Vcc and the output will resume to normal operation. 12 Leadtrend Technology Corporation LD7750R-DS-00 May 2010 www.leadtrend.com.tw LD7750R V(-)Latch OTP Release 1.05V 0.95V OTP t VCC UVLO(on) UVLO(off) PDR (8V) Latch Released t AC input Voltage AC Off AC On (Recycle) t OUT Fig. 20 Switching Non-Switching Switching t Fig. 19 Pull-Low Resistor on the Gate Pin of i = Cgd ⋅ MOSFET dVbulk dt An anti-floating resistor is built in with the OUT pin to prevent the output from any uncertain state. Otherwise, it may cause the MOSFET work abnormally or mis-trigger. However, such design won’t cover the condition of disconnection between the OUT pin and the gate terminal for the MOSFET. Thus it is still strongly recommended to have a resistor connected at the MOSFET gate terminal (as shown in Fig. 20) to provide extra protection for fault conditions. This external pull-low resistor is to prevent the MOSFET Fig. 21 from damaging during power-on when the gate resistor Rg is disconnected. In such a fault condition, as show in Fig. Protection Resistor on the Hi-V Path 21, the resistor R8 can provide a discharge path to avoid the MOSFET from being falsely triggered by the current In some Hi-V processes and designs, there may be a through the gate-to-drain capacitor CGD. Therefore, the parasitic SCR between HV pin, Vcc and GND. As shown MOSFET should be always pulled-low to persist in in Fig. 22, a small negative spike on the HV pin may off-state. trigger this parasitic SCR and cause latchup between Vcc 13 Leadtrend Technology Corporation LD7750R-DS-00 May 2010 www.leadtrend.com.tw LD7750R and GND. And such latchup will easily damage the chip because of the equivalent short-circuit induced. With the Leadtrend’s proprietary Hi-V technology, there is no such parasitic SCR in LD7750R. Fig. 23 shows the equivalent circuit of LD7750R’s Hi-V structure. The LD7750R has higher capability to sustain negative voltage than similar products. Nevertheless, a 39KΩ resistor is recommended to plant in the Hi-V path as a current limit resistor, no matter what negative voltage is present in any situation. Fig. 23 Fig. 22 14 Leadtrend Technology Corporation LD7750R-DS-00 May 2010 www.leadtrend.com.tw LD7750R Reference Application Circuit ---19V/2.15A Adapter Pin < 0.10W when Pout = 0W & Vin = 264Vac L N 6 VCC NC 8 HV CS 3 OUT 5 LD7750R 2 COMP 1 OTP 4 GND D6 RM8 IC432 ZENER1 LD7750R-DS-00 May 2010 www.leadtrend.com.tw +Vo RTN 15 Leadtrend Technology Corporation LD7750R Package Information SOP-7 Dimensions in Millimeters Dimensions in Inch Symbols MIN MAX MIN MAX A 4.801 5.004 0.189 0.197 B 3.810 3.988 0.150 0.157 C 1.346 1.753 0.053 0.069 D 0.330 0.508 0.013 0.020 F 1.194 1.346 0.047 0.053 H 0.178 0.229 0.007 0.009 I 0.102 0.254 0.004 0.010 J 5.791 6.198 0.228 0.244 M 0.406 1.270 0.016 0.050 θ 0° 8° 0° 8° 16 Leadtrend Technology Corporation LD7750R-DS-00 May 2010 www.leadtrend.com.tw LD7750R Package Information SOP-8 Dimensions in Millimeters Dimensions in Inch Symbols MIN MAX MIN MAX A 4.801 5.004 0.189 0.197 B 3.810 3.988 0.150 0.157 C 1.346 1.753 0.053 0.069 D 0.330 0.508 0.013 0.020 F 1.194 1.346 0.047 0.053 H 0.178 0.229 0.007 0.009 I 0.102 0.254 0.004 0.010 J 5.791 6.198 0.228 0.244 M 0.406 1.270 0.016 0.050 θ 0° 8° 0° 8° 17 Leadtrend Technology Corporation LD7750R-DS-00 May 2010 www.leadtrend.com.tw LD7750R Package Information DIP-8 Symbol Dimension in Millimeters Dimensions in Inches Min Max Min Max A 9.017 10.160 0.355 0.400 B 6.096 7.112 0.240 0.280 C ----- 5.334 ------ 0.210 D 0.356 0.584 0.014 0.023 E 1.143 1.778 0.045 0.070 F 2.337 2.743 0.092 0.108 I 2.921 3.556 0.115 0.140 J 7.366 8.255 0.29 0.325 L 0.381 ------ 0.015 -------- Important Notice Leadtrend Technology Corp. reserves the right to make changes or corrections to its products at any time without notice. Customers should verify the datasheets are current and complete before placing order. 18 Leadtrend Technology Corporation LD7750R-DS-00 May 2010 www.leadtrend.com.tw LD7750R Revision History Rev. Date Change Notice 00 5/12/2010 Original specification 19 Leadtrend Technology Corporation LD7750R-DS-00 May 2010 www.leadtrend.com.tw