NXP Semiconductors SSL4120T/1,518

Overview

SSL4120T/1,518 from NXP Semiconductors is a dual-function resonant power supply control IC integrating a boundary-mode PFC controller and an LLC half-bridge resonant converter (HBC) controller in a single SO24 package. It drives discrete MOSFETs in both up-converter (PFC) and resonant half-bridge stages, supports universal AC input (70–276 V_AC), delivers regulated isolated output up to 300 W, and enables >100 W highly efficient supplies with minimal external components.

For engineers reviewing the SSL4120T/1,518 datasheet, SSL4120T/1,518 pinout, SSL4120T/1,518 application, or SSL4120T/1,518 equivalent, this IC is selected for high-efficiency, low-THD, high-PF LED lighting and TV power supplies requiring integrated PFC + resonant HBC control, valley-switching operation, adaptive frequency tuning, and comprehensive latched/soft-restart protection.

Technical Context

The SSL4120T/1,518 implements a two-chip architecture: a high-voltage Bipolar-CMOS-DMOS chip handles mains start-up (via SUPHV), level-shifting, and HV gate drive, while a low-voltage SOI chip executes precise PFC on-time control, HBC frequency regulation, and fast protection response. Its PFC operates in boundary conduction mode with valley-skip at light load; the HBC supports zero-voltage switching up to 500 kHz with adjustable min/max frequency and adaptive non-overlap timing.

Protection is implemented across domains: OCP/OVP/UVP apply separately to boost voltage, HBC output, and IC supply rails; OTP triggers thermal hold; capacitive-mode detection prevents unsafe HBC operation; and RCPROT-programmable timer governs both restart delay and latched shutdown activation. The SSHBC/EN pin enables selective enablement-PFC-only or full PFC+HBC operation-with sub-50 μA disable current.

Key Specifications

Pinout & Package

SSL4120T/1,518 is housed in a plastic small outline package (SO24) with 24 leads and 7.5 mm body width (SOT137-1). The package supports surface-mount assembly and thermal dissipation suitable for >100 W continuous operation.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar resonant power supply control applications.

Compared with UCC28070DWR and ICE2PCS01G, SSL4120T/1,518 delivers lower system cost and smaller footprint through monolithic integration of PFC and HBC control with coordinated burst mode, while trading off some tuning granularity for simplified design and faster time-to-market in LED TV and lighting applications.

Availability

SSL4120T/1,518 is available at Aetrix Electronics and suitable for LED street lighting, smart TV main power supplies, commercial LED panel lighting, and industrial display power modules requiring stable component supply, long-term lifecycle support, and consistent parametric performance across production batches.

Supply support for SSL4120T/1,518 includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

NXP Semiconductors is a global semiconductor company headquartered in Eindhoven, Netherlands, specializing in secure connectivity solutions for automotive, industrial, and consumer applications.

The SSL4120T/1,518 belongs to NXP's GreenChip™ family of high-efficiency AC-DC controllers, designed specifically for cost-sensitive, high-reliability LED lighting and flat-panel display power supplies demanding integrated PFC and resonant conversion.

FAQ

What is the maximum output power achievable with SSL4120T/1,518 in a typical design?

The SSL4120T/1,518 is rated for highly efficient power supplies delivering over 100 W, with documented capability up to 300 W in optimized LED lighting and TV applications. Real-world output depends on transformer design, MOSFET selection, heatsinking, and layout-but designs exceeding 250 W have been validated using standard SO24 thermal pads and 2-oz copper layers. SSL4120T/1,518 achieves this by combining valley-switching PFC and ZVS-enabled LLC HBC to minimize conduction and switching losses simultaneously.

Does SSL4120T/1,518 support both continuous conduction mode (CCM) and boundary conduction mode (BCM) for the PFC stage?

No-SSL4120T/1,518 implements boundary conduction mode (BCM) only for the PFC controller, using on-time control and valley-skip burst mode. It does not support CCM operation. This choice optimizes efficiency at light-to-moderate loads and simplifies magnetics design, aligning with its target applications in LED lighting and displays where partial-load efficiency is critical. SSL4120T/1,518's BCM operation is confirmed in Section 2.2 and Figure 19 of the official datasheet.

How does the SSL4120T/1,518 handle overvoltage protection on the HBC output?

SSL4120T/1,518 monitors HBC output voltage via the SNSOUT pin using an auxiliary winding, rectifier, and resistive divider. When the sensed voltage exceeds 3.5 V (Vovp(SNSOUT)), it triggers immediate latched protection shutdown. External OVP circuits (e.g., TL431-based) can also be diode-OR'd into SNSOUT to provide redundant or secondary-level protection. SSL4120T/1,518's OVP response is hardware-based with no software delay, ensuring sub-microsecond fault reaction critical for safety-critical LED and display systems.

Can SSL4120T/1,518 operate without the high-voltage start-up supply (SUPHV) connected?

Yes-SSL4120T/1,518 supports stand-alone operation with SUPHV unconnected or grounded, provided SUPIC is supplied externally (e.g., from a standby DC rail or HBC auxiliary winding). In this configuration, the start threshold drops from 22 V to 17 V, and the HV start-up source remains inactive. SSL4120T/1,518 will function fully, including PFC and HBC control, as long as SUPIC and SUPREG reach their respective start voltages (17 V and 10.3 V). This mode is explicitly defined in Section 7.2.1 of the datasheet.

What is the purpose of the n.c. pins (11 and 16) on SSL4120T/1,518?

Pins 11 and 16 on SSL4120T/1,518 are designated "not connected" and serve as high-voltage spacers to ensure adequate creepage and clearance between the high-voltage (SUPHV, GATEHS, HB) and low-voltage (SUPIC, SGND, SNSOUT) domains inside the SO24 package. They are electrically isolated from all internal circuitry and must remain unconnected on the PCB to maintain reinforced insulation integrity-critical for meeting IEC 61347 and IEC 62368 safety standards in LED lighting applications. SSL4120T/1,518's datasheet confirms these pins carry no internal bond wires or functions.