LD7575PS

LD7575 6/5/2007 Green-Mode PWM Controller with High-Voltage Start-Up Circuit REV: 04a General Description Features The LD7575 is a current-mode PWM controller with z High-Voltage (500V) Startup Circuit excellent power-saving operation. It features a high- z Current Mode Control voltage current source to directly supply the startup current z Non-Audible-Noise Green Mode Control from bulk capacitor and further to provide a lossless startup z UVLO (Under Voltage Lockout) circuit. z LEB (Leading-Edge Blanking) on CS Pin blanking of the current sensing, internal slope compensation, z Programmable Switching Frequency and the small package provide the users a high efficiency, z Internal Slope Compensation minimum external component counts, and low cost solution z OVP (Over Voltage Protection) on Vcc for AC/DC power applications. z OLP (Over Load Protection) z 500mA Driving Capability The integrated functions such as the leading-edge Furthermore, the embedded over voltage protection, over load protection and the special green-mode control provide Applications the solution for users to design a high performance power circuit easily. The LD7575 is offered in both SOP-8 and DIP-8 package. Typical Application 1 Leadtrend Technology Corporation LD7575-DS-04a June 2007 z Switching AC/DC Adapter and Battery Charger z Open Frame Switching Power Supply z LCD Monitor/TV Power LD7575 Pin Configuration HV NC VCC OUT SOP-8 & DIP-8 (TOP VIEW) 8 7 6 5 YY: WW: PP: TOP MARK 2 3 4 CS GND RT 1 COMP YYWWPP Year code Week code Production code Ordering Information Part number Package Top Mark Shipping LD7575 PS SOP-8 LD7575PS 2500 /tape & reel LD7575 PN DIP-8 LD7575PN 3600 /tube /Carton The LD7575 is ROHS compliant. Pin Descriptions PIN NAME FUNCTION 1 RT 2 COMP 3 CS 4 GND Ground 5 OUT Gate drive output to drive the external MOSFET 6 VCC Supply voltage pin 7 NC Unconnected Pin This pin is to program the switching frequency. By connecting a resistor to ground to set the switching frequency. Voltage feedback pin (same as the COMP pin in UC384X), By connecting a photo-coupler to close the control loop and achieve the regulation. Current sense pin, connect to sense the MOSFET current Connect this pin to positive terminal of bulk capacitor to provide the startup current 8 HV for the controller. When Vcc voltage trips the UVLO(on), this HV loop will be off to save the power loss on the startup circuit. 2 Leadtrend Technology Corporation LD7575-DS-04a June 2007 LD7575 Block Diagram HV 1mA 8V POR UVLO Comparator 32V OVP Comparator internal bias & Vref 16.0V/ 10.0V VCC 27.5V VCC OK RT OSC PG Vref OK S Q R OVP Green-Mode Control PG Vbias S Q PWM Comparator COMP 2R OLP R R ∑ + Leading Edge Blanking CS + Slope Compensation Driver Stage POR OCP Comparator 0.85V clear 30mS Delay 5.0V OLP Comparator S /2 Counter PG GND 3 Leadtrend Technology Corporation LD7575-DS-04a June 2007 R Q OUT LD7575 Absolute Maximum Ratings Supply Voltage VCC 30V High-Voltage Pin, HV -0.3V~500V COMP, RT, CS -0.3 ~7V Junction Temperature 150°C Operating Ambient Temperature -40°C to 85°C Storage Temperature Range -65°C to 150°C Package Thermal Resistance (SOP-8) 160°C/W Package Thermal Resistance (DIP-8) 100°C/W Power Dissipation (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) 3KV ESD Voltage Protection, Machine Model 200V 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. Recommended Operating Conditions Item Supply Voltage Vcc Min. Max. Unit 11 25 V Vcc Capacitor 10 47 µF Switching Frequency 50 130 KHz 4 Leadtrend Technology Corporation LD7575-DS-04a June 2007 LD7575 Electrical Characteristics o (TA = +25 C unless otherwise stated, VCC=15.0V) PARAMETER CONDITIONS MIN TYP MAX UNITS 0.5 1.0 1.5 mA 35 µA 100 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 Operating Current (with 1nF load on OUT pin) VCOMP=0V 2.0 3.0 mA VCOMP=3V 2.5 4.0 mA Protection tripped (OLP, OVP) 0.5 mA UVLO (off) 9.0 10.0 11.0 V UVLO (on) 15.0 16.0 17.0 V OVP Level 25.0 27.5 30.0 V 2.2 mA Voltage Feedback (Comp Pin) Short Circuit Current VCOMP=0V 1.5 Open Loop Voltage COMP pin open 6.0 V 2.35 V Green Mode Threshold VCOMP Current Sensing (CS Pin) Maximum Input Voltage 0.80 Leading Edge Blanking Time 0.85 0.90 350 Input impedance nS 1 Delay to Output V MΩ 100 nS Oscillator (RT pin) Frequency RT=100KΩ 60.0 65.0 70.0 Green Mode Frequency Fs=65.0KHz Temp. Stability (-40°C ~105°C) 3 % Voltage Stability (VCC=11V-25V) 1 % Output Low Level VCC=15V, Io=20mA 1 V Output High Level VCC=15V, Io=20mA Rising Time Load Capacitance=1000pF 50 160 nS Falling Time Load Capacitance=1000pF 30 60 nS 20 KHz KHz Gate Drive Output (OUT Pin) 9 V OLP (Over Load Protection) OLP Trip Level OLP Delay Time (note) Fs=65KHz Note: The OLP delay time is proportional to the period of switching cycle. frequency and the shorter OLP delay time. 5 Leadtrend Technology Corporation LD7575-DS-04a June 2007 5.0 V 30 mS So that, the lower RT value will set the higher switching LD7575 Typical Performance Characteristics 0.90 0.89 1.3 VCS (off) (V) HV Current Source (mA) 1.5 1.1 0.88 0.87 0.9 0.86 0.7 -40 0 40 80 0.85 120 125 -40 0 Temperature (°C) Fig. 2 18.0 12 17.2 11.2 UVLO (off) (V) UVLO (on) (V) Fig. 1 HV Current Source vs. Temperature (HV=500V, Vcc=0V) 16.4 15.6 125 120 125 120 125 Temperature (°C) VCS (off) vs. Temperature 9.6 8 -40 0 40 80 120 125 -40 0 40 80 Temperature (°C) Fig. 4 UVLO (off ) vs. Temperature 70 26 68 24 Frequency (KHz) Frequency (KHz) 120 10.4 Temperature (°C) Fig. 3 UVLO (on) vs. Temperature 66 64 22 20 18 62 60 80 8.8 14.8 14.0 40 16 -40 0 40 80 120 125 -40 80 Fig. 6 Green Mode Frequency vs. Temperature 6 LD7575-DS-04a June 2007 40 Temperature (°C) Temperature (°C) Fig. 5 Frequency vs. Temperature Leadtrend Technology Corporation 0 LD7575 25 Green mode frequency (KHz) 70 Frequency (KHz) 68 66 64 62 12 14 16 18 20 22 24 21 19 17 15 11 25 12 14 16 22 Fig. 7 Frequency vs. Vcc Fig. 8 Green mode frequency vs. Vcc 35 80 30 75 70 65 24 25 120 125 120 125 25 20 15 60 10 -40 0 40 80 120 125 -40 40 0 80 Temperature (°C) Temperature (°C) Fig. 10 Fig. 9 Max Duty vs. Temperature 7.0 6.0 6.5 5.5 6.0 5.0 OLP (V) VCOMP (V) 20 Vcc (V) 85 5.5 5.0 4.5 18 Vcc (V) VCC OVP (V) Max Duty (%) 60 11 23 VCC OVP vs. Temperature 4.5 4.0 -40 0 40 80 3.5 120 125 -40 0 Temperature (°C) Fig. 11 VCOMP open loop voltage vs. Temperature Fig. 12 7 Leadtrend Technology Corporation LD7575-DS-04a June 2007 40 80 Temperature (°C) OLP-Trip Level vs. Temperature LD7575 Application Information threshold thus the current source is on to supply a current Operation Overview with 1mA. Meanwhile, the Vcc supply current is as low as As long as the green power requirement becomes a trend 100µA thus most of the HV current is utilized to charge the and the power saving is getting more and more important for Vcc capacitor. the switching power supplies and switching adaptors, the By using such configuration, the turn-on delay time will be almost same no matter under low-line or traditional PWM controllers are not able to support such new high-line conditions. requirements. Furthermore, the cost and size limitation force Whenever the Vcc voltage is higher than UVLO(on) to the PWM controllers need to be powerful to integrate more power on the LD7575 and further to deliver the gate drive functions to reduce the external part counts. The LD7575 signal, the high-voltage current source is off and the supply is targeted on such application to provide an easy and cost current is provided from the auxiliary winding of the effective solution; its detail features are described as below: transformer. Therefore, the power losses on the startup circuit can be eliminated and the power saving can be easily Internal High-Voltage Startup Circuit and achieved. Under Voltage Lockout (UVLO) An UVLO comparator is included to detect the voltage on the Vcc pin to ensure the supply voltage enough to power on the LD7575 PWM controller and in addition to drive the Vin power MOSFET. As shown in Fig. 14, a hysteresis is provided to prevent the shutdown from the voltage dip Cbulk D1 R1 during startup. The turn-on and turn-off threshold level are set at 16V and 10.0V, respectively. C1 Vcc HV VCC OUT UVLO(on) LD7575 UVLO(off) CS Comp GND Rs t Fig. 13 HV Current Traditional circuit powers up the PWM controller through a 1mA startup resistor to provide the startup current. However, the startup resistor consumes significant power which is more ~ 0mA (off) and more critical whenever the power saving requirement is coming tight. t Theoretically, this startup resistor can be very high resistance value. However, higher resistor value Vcc current will cause longer startup time. Operating Current (Supply from Auxiliary Winding) To achieve an optimized topology, as shown in figure 13, Startup Current (