Overview: The TOPSwitch-HX Family is an advanced EcoSmart® integrated off-line switcher designed for high efficiency and flexibility in power supply applications. It supports a wide power range and includes advanced functionalities suitable for various electronic devices.

Functional Description: The TOPSwitch-HX integrates a 700 V power MOSFET, PWM control, oscillator, thermal shutdown, and fault protection into a single device. It supports both primary and secondary sensing and features a soft-start function to minimize startup stress.

Output Power Table: Detailed tables show the output power capabilities of various TOPSwitch-HX models under different voltage conditions, highlighting adaptability for both adapter and open frame designs.

Application Examples: Examples of high-efficiency power supply designs demonstrate the versatility of the TOPSwitch-HX family in different power and input scenarios.

Design Considerations: Guidelines for designing with TOPSwitch-HX include layout considerations and a quick design checklist to ensure optimal performance.

Specifications: Voltage thresholds such as VUV = 102.8 VDC and VOV = 451 VDC are specified. Resistor values (RIL) for selecting different ILIMIT values are detailed, with examples like RIL = 12 k resulting in ILIMIT = 61%.

Pin Descriptions: Various pins and their functions are described:

• VOLTAGE MONITOR (V) Pin: Used for line sensing, overvoltage protection, and remote ON/OFF.
• MULTI-FUNCTION (M) Pin: Combines VOLTAGE MONITOR and EXTERNAL CURRENT LIMIT functions.
• FREQUENCY (F) Pin: Sets switching frequency to 132 kHz or 66 kHz.
• SOURCE (S) Pin: Output MOSFET source connection for high voltage power return.

Operational Modes: The chip operates in several modes to enhance efficiency:

• Full Frequency PWM Mode: Maintains constant switching frequency with duty cycle reduction.
• Variable Frequency PWM Mode: Reduces switching frequency while maintaining peak drain current.
• Low Frequency PWM Mode: Holds frequency constant at a lower rate, reducing duty cycle.
• Multi-Cycle-Modulation Mode: Enables output switching for a set period at a reduced frequency.

Additional Features: Features like frequency jittering to reduce EMI, hysteretic over-temperature shutdown, and a fully integrated soft-start to minimize output overshoot are highlighted.

Peak Drain Current Control: A mode of operation maintains low peak drain current and minimizes harmonic frequencies between 6 kHz and 30 kHz, reducing transformer audible noise.

Maximum Duty Cycle: The default maximum duty cycle is set at 78%, adjustable to 40% by connecting specific pins to the DC high voltage bus through a resistor.

Error Amplifier: The shunt regulator functions as an error amplifier in primary side feedback applications, with the CONTROL pin setting the gain.

On-Chip Current Limit: The cycle-by-cycle peak drain current limit uses the MOSFET ON-resistance as a sense resistor, with the current limit externally programmable.

Line Undervoltage Detection (UV): UV keeps the device off until the input voltage reaches a threshold, preventing glitches during power down.

Line Overvoltage Shutdown (OV): Exceeding the overvoltage threshold stops switching, with a hysteresis to prevent noise triggering.

Hysteretic or Latching Output Overvoltage Protection (OVP): Triggered by line overvoltage, this protection latches the device off if certain conditions are met.

Line Feed-Forward with DCMAX Reduction: This feature minimizes output line ripple and reduces sensitivity to line transients.

Remote ON/OFF: The device can be turned on or off remotely by controlling specific pins.

Soft-Start: A 17 ms soft-start minimizes current and voltage stresses during start-up.

Shutdown/Auto-Restart: The TOPSwitch-HX features a shutdown/auto-restart circuit that minimizes power dissipation during fault conditions.

Hysteretic Over-Temperature Protection: A precision analog circuit provides temperature protection by turning off the output MOSFET when the junction temperature exceeds 142°C.

Bandgap Reference: Critical internal voltages are derived from a temperature-compensated bandgap reference.

High-Voltage Bias Current Source: This source biases the TOPSwitch-HX from the DRAIN pin and charges the CONTROL pin capacitance during start-up.

Figures and Schematics: Various figures illustrate the voltage monitor, external current limit, and multi-function pin operations.

Application Example: A high-efficiency, 35 W dual output power supply design is presented, utilizing TOPSwitch-HX features to reduce cost and size while improving efficiency.

Specifications: Specifications for various power supply designs are outlined, including input voltage ranges, output power, efficiency ratings, and component configurations.

Design Procedures: Each power supply design is accompanied by a detailed circuit diagram and explanation of the components used.

Standards and Recommendations: The document emphasizes the importance of using high-efficiency components and proper circuit configurations.

Performance Comparisons: A comparison table highlights the advantages of TOPSwitch-HX over TOPSwitch-GX.

Key Considerations: Design considerations for achieving maximum practical continuous output power are provided.

TOPSwitch-HX Selection: The selection of the optimal TOPSwitch-HX depends on factors such as maximum output power, efficiency, and system requirements.

Input Capacitor: The input capacitor should provide the minimum DC voltage required for regulation.

Primary Clamp and Output Reflected Voltage (VOR): A primary clamp limits the peak drain-to-source voltage.

Output Diode: Selection is based on peak inverse voltage, output current, and thermal conditions.

Bias Winding Capacitor: A 10 μF capacitor is recommended for low frequency operation at no-load.

Soft-Start: The on-chip soft-start feature reduces stress on components during start-up.

EMI: Frequency jitter reduces conducted EMI peaks.

Transformer Design: Recommended maximum operating flux density is 3000 Gauss.

Standby Consumption: Frequency reduction minimizes power loss at light or no load.

High Power Designs: Special considerations are needed for designs delivering up to 333 W.

Layout Considerations: Proper layout is crucial for high power levels.

Heat Sinking: Heat sinks should not be electrically tied to primary ground/source nodes.

Quick Design Checklist: Includes verifying maximum drain voltage, maximum drain current, and performing thermal checks.