Features: Internal Avalanche Rugged FET consumes only 0.65W at 240V AC and 0.3W load Advanced Burst Mode Operation Low EMI Frequency Modulation Accurate Fixed Operating Frequency Internal Startup Circuit Pulse-by-Pulse Current Limiting Overvoltage Protection Overload Protection Internal Thermal Shutdown Function Auto-restart mode Undervoltage lockout Low operating current (3MA) Adjustable peak current limit Built-in soft-start

Applications: Switching power camera adapters for VCRs, SVRs, set-top boxes, DVDs and DVCDs for printers, fax machines and scanners

Description: The fsdx0365rnb (x stands for l, m) is an integrated pulse width modulator (pwm) and sensing fet designed for high performance offline switching power supplies (SMP) with minimal external components. Both devices are integrated high voltage power switching regulators that combine avalanche rugged sensing FETs and current mode pulse width modulation control blocks. Features of the integrated pwm controller include: fixed frequency oscillator for reduced EMI modulation, undervoltage lockout (uvlo) protection, leading edge blanking (leb), optimized gate on/off driver, thermal shutdown (TSD) Protection and Temperature Compensation Accuracy Loop Compensation and Fault Protection for Current Source Circuits. fsdx0365rnb is softer than fsdx0365rn. When combined with discrete mosfet and controller or rcc switching converter solutions, the fsdx0365rnb reduces overall component count, design size, and weight while increasing efficiency, productivity and system reliability. Both devices are platform converters ideal for cost-effective flyback designs.

Table 1. Notes: 1. Typical continuous power in a non-vented enclosed adapter with adequate drain pattern or heat sink measured at an ambient temperature of 50°C. 2. The maximum practical continuous power of the open frame has enough heat sink for the design of the gutter under 50°C environment. three. 230 VAC or 100/115 VAC doubles.

Functional Description 1. In previous generations of Fairchild Power Switch (FPS) VSTR pins had an external resistor to the DC input voltage line. In this generation, the start-up resistor is powered by an internal high voltage current source and the switch voltage VCC is turned off after 15 minutes of power supply is higher than 12V. If VCC drops below 8V.

2. Feedback control: fsdx0365rnb adopts current mode control, as shown in the figure. Optocouplers (such as h11a817a) and shunt regulators (such as ka431) are commonly used to implement feedback networks. Comparing the feedback voltage to the voltage across the sensor resistor plus the offset voltage controls the switching duty cycle. When the KA431 exceeds the internal reference voltage of 2.5V, the H11A817A LED current increases, thereby reducing the feedback voltage and reducing the duty cycle. This activity occurs when the input voltage increases or the output load decreases. 3. Leading edge blanking (Leb): At the moment when the internal sensing FET is turned on, there is usually a large current spike of the induced current transformer caused by the primary side. Capacitor and secondary side rectifier diode reverse recovery. Excessive voltage on the RSENSE resistor can result in incorrect feedback operation control in current mode. To counteract this effect, fps uses a leading edge blanking (LEB) circuit. This circuit suppresses the short-time comparator (TLEB) turning on after the PWM sensing FET is activated.

4. Protection circuit: FPS has overload protection, overvoltage protection, abnormal overcurrent protection and other protection functions. Under Voltage Lockout (uvlo) and Thermal Shutdown (TSD). Because these protection circuits are fully integrated within the integrated circuit with no external components, reliability is improved without increasing cost. Once a fault occurs, the switch is terminated and the sensing FET remains off. This causes VCC to drop. Stop voltage when vcc reaches uvlo, 8V, protection reset, internal high voltage current source to charge VCC capacitor through VSTR pin. When the vcc reaches the uvlo startup voltage of 12v, the fps resumes normal operation. In this way, auto-restart can alternately enable and disable the power switching sense FET until the fault condition is eliminated. 4.1 Overload Protection (OLP): Overload is defined as load current exceeding a preset level due to unexpected events. In this case, the protection circuit should be activated to protect the SMPS. However, even when the switching power supply is operating normally, overloading during the load transition can activate the protection circuit. To avoid this undesired operation, overload protection circuits are designed to determine whether this is a transient condition or an overload condition as specified. Combined with the IPK current limit pin (if used) the current mode feedback path will limit the FET current at maximum PWM operating current to cycling. If the output consumes more than this maximum power, the output voltage (VO) drops below the set value. Voltage. This reduces the current through the optocoupler LED, it also reduces the current through the optocoupler transistor, which increases the feedback voltage (vfb). If VFB exceeds 3V, the feedback input diode is blocked and the 5UA IDELAY current source begins to slowly charge the CFB until it reaches VCC. Under this condition, VFB continues to increase until it reaches 6V, at which point the switching operation is terminated as shown. The delay time for shutdown is the time it takes to charge the CFB from 3V to 6V with 5uA.

4.2.Thermal shutdown ("TSD"): The sense fet and the control IC are integrated, making it easy to control the IC to detect the temperature of the sensor. 4.3 Overvoltage protection is activated when the temperature exceeds about 140°C, thermal fracture: Take a fault in a two-sided feedback circuit as an example, or an opening of the feedback loop due to a solvent defect, the current through the photo-coupled transistor becomes minimum zero. Then, the VFB click resembles an overload condition, forcing the current maximum current to be supplied to the SMPS. until the overload protection is activated. Because of excess energy output, the output voltage can be activated in addition to the voltage rate before the overload protection, resulting in rupture of the device in the second zone. To prevent this, an overvoltage protection (OVP) circuit is used. In general the ratio of output voltage to FPS used directly monitors the output voltage. ifVCC Exceeds 19V, OVP circuit is activated in termination of switching operation. To avoid uncontrolled activation of the UFP during normal operation, VCC should be preset at the following 5. Soft Start: The FPS has an internal soft start circuit that increases the feedback voltage and the sense current starts slowly after the current. A typical soft-start time is 15 MSEC, as shown in Figure 7, where progressive increments are allowed in the initial phase and rational fet currents are allowed. The pulse width of the power switching device is gradually increased to establish the correct operating conditions. For transformers, inductors and capacitors. The voltage output capacitance is gradually increased. Smooth the intended age of building the desired output volts. It also helps prevent transformer saturation and reduce stress on the secondary diode.

6. Burst operation: To minimize power consumption in standby mode, fps enters burst mode operation.

As the load decreases, the feedback voltage decreases. As shown, the device automatically enters a burst when the feedback voltage falls below Vburh (500 mV). Switching continues, but the current limit is set to a fixed internal limit to minimize flux density in the transformer. The fixed current limit is greater than that defined by vfB=vBurh, so vfB is driven down further. Continue switching until the feedback voltage drops below vburl (350mv). The rate at which switching stops and the output voltage begins to drop depends on the backup current load. This causes the feedback voltage to go up. Once Vburh (500 mV) is passed, the switch resumes. Then the feedback voltage drops and the process repeats. Burst Mode operation alternately enables and disables the switching of the power-sensing FET, reducing switching losses in standby mode.

7. Frequency modulation: EMI reduction can be achieved by modulating the switching frequency of the power supply. FM can be measured by spreading energy over a wider bandwidth than EMI test equipment. This EMI reduction is related to the reference frequency. As shown, for the FSDM0365RNB. Frequency modulation allows the use of cost-effective inductors instead of AC input mode chokes to meet global EMI limits. 8. Adjust the current limiting function: As shown, the 2.8kΩ internal resistance of the A combination is connected to the non-inverting wire on the pwm comparator. External main current source when the internal diode is biased at 900uA.

For example, the fsdx0365rnb has a typical sense fet current limit (iover) of 2.15A. By inserting a 2.4kΩ limit between the current limit to the 1A pin and ground, derived by the following equation:

Multi-Output, 20W, 85-265Vac Input Power Supply: The diagram shows a typical multi-output power supply containing a high-capacity hard drive for a terminal set-top box recording or a LIPS (LCD Inverter Power Supply) 15" liquid crystal display. This power supply provides an output power of 20W continuous/24 W peak (thermally limited), input voltage from 85 to 265 Vac. ≥75% efficiency at 20W, 85Vac. 3.3 V and 5 V outputs regulated to ±5%, no secondary linear regulator required. DC superimposed (other outputs Secondary winding reference for voltage is to D15 anode. For better accuracy, connection to D15 cathode would be better.) Used to minimize voltage error at high voltage output. Due to typical high ambient operating temperature requirements set-top boxes (60 °C) The FSDM0365RNB is used to reduce conduction losses without a heat sink. Resistor R5 sets the device current limit to limit overload power. A leakage inductance clamp is provided by R1 and C8 to keep the drain voltage below 650 volts under all conditions. Resistor r1 and capacitor c8 are chosen such that r1 dissipates power to prevent the drain voltage from rising through the leakage inductance. The frequency modulation characteristics of the fsdm0365rnb allow the circuit shown to meet requirements with simple EMI filtering (C1, LF1 and C2) and output grounding. The second The batch has been corrected and smoothed through D12, D13, D14 and D15. Diode D15. The 3.4V output is a Schottky diode to maximize efficiency. Diode D14 for the 5V output is a pn type to center the 5V on 5 23V output. The 3.3V and 5V output voltages require two parallel capacitors to meet the ripple current requirement. Switching noise filtering is provided by l3, l2 and l1. Resistor R15 prevents peak charging of light loads on the 23V output. The output is regulated by reference (TL431) Secondary voltage. Both 3.3 V and 5 V outputs are sensed through R13 and R14. Resistor r22 provides bias. For tl431 and r21, sets the overall DC gain. Resistors r21, C209, R14, and R13 provide loop compensation.