LD7575PN

LD7575 6/5/2007 Green-Mode PWM Controller with High-Voltage Start-Up Circuit REV: 04a General Description The LD7575 is a current-mode PWM controller with excellent power-saving operation. It features a highvoltage current source to directly supply the startup current from bulk capacitor and further to provide a lossless startup circuit. The integrated functions such as the leading-edge blanking of the current sensing, internal slope compensation, and the small package provide the users a high efficiency, minimum external component counts, and low cost solution for AC/DC power applications. Furthermore, the embedded over voltage protection, over load protection and the special green-mode control provide the solution for users to design a high performance power circuit easily. DIP-8 package. The LD7575 is offered in both SOP-8 and Features High-Voltage (500V) Startup Circuit Current Mode Control Non-Audible-Noise Green Mode Control UVLO (Under Voltage Lockout) LEB (Leading-Edge Blanking) on CS Pin Programmable Switching Frequency Internal Slope Compensation OVP (Over Voltage Protection) on Vcc OLP (Over Load Protection) 500mA Driving Capability Applications Switching AC/DC Adapter and Battery Charger Open Frame Switching Power Supply LCD Monitor/TV Power Typical Application 1 Leadtrend Technology Corporation LD7575-DS-04a June 2007 LD7575 Pin Configuration SOP-8 & DIP-8 (TOP VIEW) VCC 6 8 7 OUT 5 NC HV TOP MARK YYWWPP 1 2 3 4 YY: WW: PP: Year code Week code Production code RT COMP Ordering Information Part number LD7575 PS LD7575 PN Package SOP-8 DIP-8 Top Mark LD7575PS LD7575PN Shipping 2500 /tape & reel 3600 /tube /Carton The LD7575 is ROHS compliant. Pin Descriptions PIN 1 NAME RT FUNCTION 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 Ground Gate drive output to drive the external MOSFET Supply voltage pin Unconnected Pin 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 3 4 5 6 7 COMP CS GND OUT VCC NC GND CS 2 Leadtrend Technology Corporation LD7575-DS-04a June 2007 LD7575 Block Diagram HV 1mA 8V POR 32V 16.0V/ 10.0V UVLO Comparator OVP Comparator VCC internal bias & Vref VCC OK 27.5V RT OSC PG Vref OK S Q R Green-Mode Control Vbias OVP PG S Q OLP COMP PWM Comparator 2R R R ∑ + Slope Compensation POR 0.85V OCP Comparator CS Leading Edge Blanking + Driver Stage OUT clear 30mS Delay OLP Comparator /2 Counter S Q 5.0V PG R GND 3 Leadtrend Technology Corporation LD7575-DS-04a June 2007 LD7575 Absolute Maximum Ratings Supply Voltage VCC High-Voltage Pin, HV COMP, RT, CS Junction Temperature Operating Ambient Temperature Storage Temperature Range Package Thermal Resistance (SOP-8) Package Thermal Resistance (DIP-8) Power Dissipation (SOP-8, at Ambient Temperature = 85°C) Power Dissipation (DIP-8, at Ambient Temperature = 85°C) Lead temperature (Soldering, 10sec) ESD Voltage Protection, Human Body Model (except HV Pin) ESD Voltage Protection, Machine Model Gate Output Current 30V -0.3V~500V -0.3 ~7V 150°C -40°C to 85°C -65°C to 150°C 160°C/W 100°C/W 400mW 650mW 260°C 3KV 200V 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 Vcc Capacitor Switching Frequency Min. 11 10 50 Max. 25 47 130 Unit V µF KHz 4 Leadtrend Technology Corporation LD7575-DS-04a June 2007 LD7575 Electrical Characteristics (TA = +25 C unless otherwise stated, VCC=15.0V) PARAMETER High-Voltage Supply (HV Pin) High-Voltage Current Source Off-State Leakage Current Supply Voltage (Vcc Pin) Startup Current Operating Current (with 1nF load on OUT pin) UVLO (off) UVLO (on) OVP Level Voltage Feedback (Comp Pin) Short Circuit Current Open Loop Voltage Green Mode Threshold VCOMP Current Sensing (CS Pin) Maximum Input Voltage Leading Edge Blanking Time Input impedance Delay to Output Oscillator (RT pin) Frequency Green Mode Frequency Temp. Stability Voltage Stability Gate Drive Output (OUT Pin) Output Low Level Output High Level Rising Time Falling Time OLP (Over Load Protection) OLP Trip Level OLP Delay Time (note) Fs=65KHz 5.0 30 V mS VCC=15V, Io=20mA VCC=15V, Io=20mA Load Capacitance=1000pF Load Capacitance=1000pF 9 50 30 160 60 1 V V nS nS RT=100KΩ Fs=65.0KHz (-40°C ~105°C) (VCC=11V-25V) 60.0 65.0 20 3 1 70.0 KHz KHz % % 1 100 0.80 0.85 350 0.90 V nS MΩ nS VCOMP=0V COMP pin open 1.5 6.0 2.35 2.2 mA V V VCOMP=0V VCOMP=3V Protection tripped (OLP, OVP) 9.0 15.0 25.0 2.0 2.5 0.5 10.0 16.0 27.5 11.0 17.0 30.0 100 3.0 4.0 µA mA mA mA V V V Vcc< UVLO(on), HV=500V Vcc> UVLO(off), HV=500V 0.5 1.0 1.5 35 mA µA CONDITIONS MIN TYP MAX UNITS o Note: The OLP delay time is proportional to the period of switching cycle. frequency and the shorter OLP delay time. So that, the lower RT value will set the higher switching 5 Leadtrend Technology Corporation LD7575-DS-04a June 2007 LD7575 Typical Performance Characteristics 1.5 0.90 HV Current Source (mA) 1.3 0.89 VCS (off) (V) 0 40 80 120 125 0.88 1.1 0.87 0.9 0.86 0.7 -40 0.85 -40 0 40 80 120 125 Temperature (°C) Fig. 1 HV Current Source vs. Temperature (HV=500V, Vcc=0V) 18.0 12 Fig. 2 Temperature (°C) VCS (off) vs. Temperature 17.2 11.2 UVLO (on) (V) UVLO (off) (V) -40 0 40 80 120 125 16.4 10.4 15.6 9.6 14.8 8.8 14.0 8 -40 0 40 80 120 125 Temperature (°C) Fig. 3 UVLO (on) vs. Temperature 70 26 Temperature (°C) Fig. 4 UVLO (off ) vs. Temperature 68 24 Frequency (KHz) -40 0 40 80 120 125 Frequency (KHz) 66 22 64 20 62 18 60 16 -40 0 40 80 120 125 Temperature (°C) Fig. 5 Frequency vs. Temperature Temperature (°C) Fig. 6 Green Mode Frequency vs. Temperature 6 Leadtrend Technology Corporation LD7575-DS-04a June 2007 LD7575 70 25 68 Green mode frequency (KHz) 12 14 16 18 20 22 24 25 23 Frequency (KHz) 66 21 64 19 62 17 60 11 15 11 12 14 16 18 20 22 24 25 Vcc (V) Fig. 7 Frequency vs. Vcc 85 35 Vcc (V) Fig. 8 Green mode frequency vs. Vcc 80 30 Max Duty (%) 75 VCC OVP (V) -40 0 40 80 120 125 25 70 20 65 15 60 10 -40 0 40 80 120 125 Temperature (°C) Fig. 9 Max Duty vs. Temperature 7.0 6.0 Temperature (°C) Fig. 10 VCC OVP vs. Temperature 6.5 5.5 VCOMP (V) 5.5 OLP (V) -40 0 40 80 120 125 6.0 5.0 4.5 5.0 4.0 4.5 3.5 -40 0 40 80 120 125 Temperature (°C) Fig. 11 VCOMP open loop voltage vs. Temperature Fig. 12 Temperature (°C) OLP-Trip Level vs. Temperature 7 Leadtrend Technology Corporation LD7575-DS-04a June 2007 LD7575 Application Information Operation Overview As long as the green power requirement becomes a trend and the power saving is getting more and more important for the switching power supplies and switching adaptors, the traditional PWM controllers are not able to support such new requirements. Furthermore, the cost and size limitation force the PWM controllers need to be powerful to integrate more functions to reduce the external part counts. The LD7575 is targeted on such application to provide an easy and cost effective solution; its detail features are described as below: threshold thus the current source is on to supply a current with 1mA. Meanwhile, the Vcc supply current is as low as 100µA thus most of the HV current is utilized to charge the Vcc capacitor. By using such configuration, the turn-on delay time will be almost same no matter under low-line or high-line conditions. Whenever the Vcc voltage is higher than UVLO(on) to power on the LD7575 and further to deliver the gate drive signal, the high-voltage current source is off and the supply current is provided from the auxiliary winding of the transformer. achieved. An UVLO comparator is included to detect the voltage on the Vcc pin to ensure the supply voltage enough to power Vin Therefore, the power losses on the startup circuit can be eliminated and the power saving can be easily Internal High-Voltage Startup Circuit and Under Voltage Lockout (UVLO) on the LD7575 PWM controller and in addition to drive the power MOSFET. Cbulk R1 D1 As shown in Fig. 14, a hysteresis is provided to prevent the shutdown from the voltage dip during startup. The turn-on and turn-off threshold level are set at 16V and 10.0V, respectively. C1 Vcc HV VCC OUT LD7575 Comp GND CS UVLO(on) UVLO(off) Rs t Fig. 13 Traditional circuit powers up the PWM controller through a startup resistor to provide the startup current. However, the startup resistor consumes significant power which is more and more critical whenever the power saving requirement is coming tight. Theoretically, this startup resistor can be HV Current 1mA ~ 0mA (off) t Vcc current Operating Current (Supply from Auxiliary Winding) Startup Current (