PT4557ENEASG Integrated Non-Isolated Buck LED Constant Current Driver Chip

High Precision | Wide Voltage 85Vac~265Vac | High Integration | Quasi-Resonant Mode | Built-in 500V Power MOS | Built-in Bridge Rectifier | Built-in Freewheeling Diode

Description

PT4557EN is a high-precision non-isolated buck LED constant current driver chip. It operates in quasi-resonant mode, suitable for non-isolated buck LED constant current power supplies with an input voltage range of 85Vac~265Vac. PT4557EN integrates a bridge rectifier, 500V power MOS, high-voltage power supply circuit, freewheeling diode, and sampling circuit on a single chip. It requires no start-up resistor or VDD capacitor, and the system uses very few external components, greatly reducing system cost and size. PT4557EN adopts a highly reliable constant current control method to achieve excellent line regulation, load regulation, and temperature characteristics. The output current mass production deviation is within ±5%. PT4557EN provides complete protection functions including LED short-circuit protection and over-temperature derating protection. PT4557EN is packaged in ASOP-7.

Features

High-voltage monolithic integration of 500V power transistor with high stability. Internal freewheeling diode integrated. Internal bridge rectifier integrated. No start-up resistor or VDD capacitor required. Inductor current quasi-resonant mode (QR) reduces switching loss. Efficiency up to 93%. ±5% current accuracy. Excellent line regulation, load regulation and temperature characteristics. LED short-circuit protection. Over-temperature current derating protection. ASOP-7 package.

Applications

LED candle lights, A-shape bulbs. LED downlights, tube lights. Other LED lighting.

Core Advantages

Fully integrated single-chip solution eliminates external bridge rectifier, freewheeling diode, start-up resistor, and VDD capacitor, minimizing external components. Quasi-resonant QR mode reduces switching loss, achieving up to 93% system efficiency and lower temperature rise. Wide voltage 85Vac-265Vac for global use, compatible with power grids in different regions. ±5% output current accuracy ensures excellent mass production consistency. Built-in LED short-circuit protection and over-temperature derating greatly improve system reliability. ASOP-7 SMD package features small size and good heat dissipation, ideal for compact LED lamps. Stable supply from domestic original manufacturer with superior cost-performance ratio over imported counterparts.

Ordering Information

Pin Definition (ASOP-7)

Absolute Maximum Ratings

Recommended Output Power

Electrical Characteristics (TA=25℃)

Typical Application Circuit

Package Dimensions (ASOP-7)

Unit: mm, Typical size L=6.2mm, W=3.9mm, SMD package, excellent thermal performance

Functional Description

PT4557EN is a constant current driver chip dedicated to LED lighting, used in non-isolated buck LED driver power supplies. The chip integrates a 500V power switch internally and achieves excellent constant current characteristics with minimal external components. No auxiliary winding power supply or sensing is required, resulting in extremely low system cost.

After power-on, the bus voltage supplies the internal VDD module through the HV pin. The chip has a built-in Zener diode to clamp the VDD voltage. The VDD current required during normal operation is very low, so no auxiliary winding power supply is needed. Therefore, no external VDD capacitor is required, reducing external components and cost. An output capacitor of 1nF or more is recommended to ensure good EMC and output ripple performance.

The chip detects the inductor peak current cycle-by-cycle. The CS pin is connected to the input of the internal peak current comparator and compared with the internal 387mV threshold voltage. When the CS voltage reaches the internal detection threshold, the power transistor turns off. Inductor peak current: Ipk=387/Rcs(mA). LED output current: ILED=Ipk/2.

PT4557EN operates in quasi-resonant mode. When the power transistor turns on, the current through the inductor rises from zero. The turn-on time is controlled by internal logic. When the inductor current drops to zero after the power transistor turns off, the internal logic turns on the power transistor again. The chip sets a minimum and maximum demagnetization time to ensure stable critical conduction mode operation.

Protection Functions

LED Short-Circuit Protection: When LED is shorted, the system operates at low frequency of 2-4KHz, and the CS turn-off threshold is reduced by about half, resulting in very low power consumption. Over-Temperature Protection: When the chip temperature exceeds 150℃, the output current is gradually reduced to control power and temperature rise. The system resumes normal operation when the temperature drops below 150℃.

Application Scenarios

PT4557ENEASG is suitable for LED lighting drivers with 85Vac-265Vac full voltage input, mainly used in LED candle lights, A-shape bulbs, downlights, tube lights, panel lights, ceiling lamps, small integrated LED driver power supplies and other low-power indoor LED lighting products. With high integration, few external components, low cost and high efficiency, it is especially suitable for LED lamps with compact space and strict requirements for cost and reliability.

Application Method

ACL and ACN connect to AC mains. HV is the high-voltage power supply pin. SW connects to inductor and output loop. CS connects a current-sense resistor to GND. GND is system ground. Output current is set by adjusting the sense resistor Rcs at CS pin: Ipk=387/Rcs, ILED=Ipk/2. A capacitor ≥1nF is recommended at the output to improve ripple and EMC performance. The circuit requires no start-up resistor, VDD capacitor, external bridge rectifier or freewheeling diode, providing an extremely simple design.

Compatible Replacements & Advantage Comparison

Direct replacement models: BP2861, PT4556, SDH8322, SDH8323, LN8K09 and other non-isolated buck LED driver ICs.

Advantages over competitors: PT4557ENEASG has higher integration with built-in bridge rectifier and freewheeling diode, eliminating more external components. No start-up resistor or VDD capacitor reduces BOM cost further. Quasi-resonant mode delivers higher efficiency and lower temperature rise. ±5% current accuracy ensures better mass production consistency. Complete dual protection improves system stability. ASOP-7 package provides better thermal performance for compact lamps. Stable supply from domestic original manufacturer offers clear advantages in price and lead time.

PT4557EN Datasheet Ver. CH1.3 | PowTech | GSMICRO SEMICONDUCTOR (Shenzhen) Co., Ltd.