feature

Avalanche internal sensor (650V) under 50 MW power consumption in no-load state Precision fixed frequency Frequency modulation to reduce EMI Internal start circuit built on soft start: 20MS pulse double pulse Current limit OLP), Output Short Protection (OSP), Abnormal Over Current Internal Thermal Shutdown Protection Hysteresis Function Self-Recovery Mode Under Voltage Lock (UVLO) Low Operating Current: 1.8MA Adjustable Peak Current Limit.

application

VCR, STB, DVD, & DVCD Players Home Application System Adaptation Related Resources AN-4147 - RCD Snubber Design Guidelines Flyback Description The FSL116LR integrated pulse width modulator (pwm) and sensefet is designed for high performance offline switching power supplies (smps) using minimal external components. The FSL116LR includes an integrated high voltage power switch combined with an avalanche voltage regulator sensor with a current mode PWM control block. The integrated pwm controller includes: undervoltage lockout (uvlo) protection, leading edge blanking (LEB), frequency generator for EMI attenuation, optimized gate switch driver, thermal shutdown (TSD) protection and temperature compensation precision for loop Current source compensation and fault protection circuits. The FSL116LR has good soft-start performance. when? Compared to discrete mosfet and controller or rcc switching converter solutions, the FSL116LR reduces total component count, design size and weight; while improving efficiency, productivity and system reliability. This device provides a very suitable basic platform for designing cost-effective flyback converters.

Function description

At startup, the internal high voltage current source provides internal bias and connects an external charging capacitor (CA) to the VCC pin as shown. When VCC reaches 12V , the FPS™ starts switching and the internal high voltage current source is disabled. The FPS continues normal switching operation and supplies power from the auxiliary transformer winding unless VCC falls below the 8V stop voltage.

Oscillator block oscillator frequency is set internally, fps has random frequency fluctuation function. Switching frequency fluctuating power supplies reduce EMI by dispersing energy measured by EMI test equipment over a wider frequency range than bandwidth. Quantitative EMI reduction and frequency variation. The frequency range is fixed internally; however, the choice is a random combination of external feedback voltages and an internal free-running oscillator. This randomly chosen switching frequency effectively extends the EMI noise around the switching frequency, allowing the use of a cost-effective inductor instead of an AC input line filter to meet global EMI requirements.

The feedback control fsl116lr adopts the current mode control, as shown in the figure. Optocouplers (such as the FOD817A) and feedback networks are typically implemented using shunt regulators (such as the KA431 ). Comparing the feedback voltage to the voltage across the sensor resistor makes it possible to control the switching load cycle. When the reference pin voltage of the parallel regulator exceeds the internal reference voltage of 2.5V, the optocoupler LED current increases, the feedback voltage VFB is pulled down, and the duty cycle is reduced. When the input voltage is increasing or decreasing the output load. Pulse Width Modulation Circuits Leading Edge Blanking (LEB) Primary side capacitance and secondary side rectifier diode reverse recovery typically cause high currents to pass through the sensor mesh when the internal sensor is turned on. Over voltage sensor resistance causes incorrect feedback in current mode operation of pwm control. To deal with this effect, fps adopts leading edge blanking (LEB) circuit. This circuit suppresses the short-time pulse width modulation comparator (TLEB) after the sensefet has been turned on.

The protection circuit fps has several protection functions such as overload protection (OLP), over voltage protection (ovp), output short circuit protection (osp), under voltage lockout (uvlo), abnormal over current protection (AOCP) and thermal shutdown (TSD) . Because these integrated circuits integrate various protection circuits without external components, reliability is improved without increasing costs. In the event of a fault, the switch is terminated and the sensor remains off. This causes VCC to drop. When vcc reaches uvlo stop voltage, VSTOP(8V), protection reset, internal high voltage current source charges VCC through capacitor at VSTR pin. When vcc reaches uvlo start voltage, V starts (12V), FPS returns to normal operation. This way, auto-restart can alternately enable and disable the power sensor settings until troubleshooting. FSL116LR - Green Mode FAIRC Leading Edge Blanking (LEB) Primary side capacitance and secondary side rectifier diode reverse recovery typically cause high currents through the sensor mesh when the internal sensor is turned on. Overvoltage sensor resistance causes incorrect feedback for pwm control operating in current mode. To deal with this effect, fps adopts leading edge blanking (LEB) circuit. This circuit suppresses the short-time pulse width modulation comparator (TLEB) after the sensefet has been turned on. The protection circuit fps has several protection functions such as overload protection (OLP), over voltage protection (ovp), output short circuit protection (osp), under voltage lockout (uvlo), abnormal over current protection (AOCP) and thermal shutdown (TSD) . Because these integrated circuits integrate various protection circuits without external components, reliability is improved without increasing costs. In the event of a fault, the switch is terminated and the sensor remains off. This causes VCC to drop. When vcc reaches uvlo stop voltage, VSTOP(8V), protection reset, internal high voltage current source charges VCC through capacitor at VSTR pin. When vcc reaches uvlo start voltage, V starts (12V), FPS returns to normal operation. This way, auto-restart can alternately enable and disable the power sensor settings until troubleshooting. Output Short-Circuit Protection (OSP) If the output is short-circuited, a steep current high di/dt can occur at the Leber time. Such large currents produce high voltage stress on the sensor drain when shutting down. That protects the device from abnormal conditions, the osp detects the on time of vfb and sensefet. When VFB is higher than 1.6V and the sensor turn-on time is lower than 1.0m, FPS recognizes this condition as an abnormal error and turns off the pwm switch until VCC reaches VStart again.

Abnormal Conditions Soft Start The FPS has an internal soft start circuit that increases the feedback voltage, as well as the induced current, after startup. A typical soft-start time is 20 ms, as shown, where sensor current is allowed to increase during the start-up phase. The pulse width switching device of the power is stepped up to establish the correct operating conditions of the transformer, inductor and capacitor. The output voltage capacitor is gradually increased to smoothly establish the desired output voltage. Soft-start helps prevent transformer saturation and reduces stress on the secondary diode. Burst Operation To minimize power consumption in standby mode, fps goes into burst mode. As the load decreases, the feedback voltage decreases. When the feedback voltage drops below Vburh. Switching continues, but the current limit is fixed internally to minimize the flux density of the transformer. The fixed current limit is greater than the limit defined by vfb=vBurh Therefore, vfb is further reduced. Switching continues until the feedback voltage drops below vburl. At this point, switching stops and the speed at which the output voltage begins to drop depends on the backup current load. This causes the feedback voltage to rise. Once it passes vburh, the switch continues. The feedback then drops the voltage and the process repeats. Burst Mode alternately enables and disables sensing in standby and reduces switching losses.