Texas Instruments UCC29950D

Overview

UCC29950 from Texas Instruments is a CCM boost PFC and half-bridge LLC resonant combo controller in SOIC-16 package, delivering fixed 100-kHz PFC switching with dithering and adjustable 70–350 kHz LLC frequency. It integrates self-bias startup via depletion-mode MOSFET control (SUFG/SUFS), three-level LLC over-current protection, and true input power limiting independent of line voltage - enabling high-efficiency (>90%) offline AC-to-DC server and industrial power supplies.

For engineers reviewing the UCC29950 datasheet, UCC29950 pinout, UCC29950 application, or UCC29950 equivalent, key selection considerations include its dual-stage control coordination, integrated X-cap discharge, active thermal shutdown at 125°C, dead-time variation across load for extended ZVS range, and internal PFC loop compensation eliminating external Type-II/III networks.

Technical Context

The UCC29950 implements a proprietary hybrid average/peak current control algorithm for the CCM boost PFC stage - using average current regulation for THD optimization and peak current sensing (PFC_CS) for cycle-by-cycle MOSFET current limiting. Its internal compensation eliminates external error amplifier components while maintaining stability across bulk capacitor and inductor tolerances.

For the LLC stage, the controller uses FB pin voltage to directly modulate switching frequency (70–350 kHz), dynamically adjusts dead time (224–388 ns at f_LLCmin) to sustain zero-voltage switching across load, and applies three-tiered over-current protection (OCP1/OCP2/OCP3) with hiccup-mode recovery. AC_DET provides synchronized brownout indication with 100-ms hold-up before shutdown.

Key Specifications

Pinout & Package

UCC29950 is housed in a 9.90 mm × 6.00 mm SOIC-16 (D) package with standard 1.27-mm pitch, rated for 125°C junction operation and 78.9°C/W junction-to-ambient thermal resistance.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar CCM PFC + LLC combo controller applications.

Compared with UCC28070 and ICE2PCS01, the UCC29950 uniquely integrates both CCM PFC and LLC control in one SOIC-16 IC - enabling compact, high-efficiency (>94%), low-standby designs without external coordination logic or additional gate drivers.

Availability

UCC29950 is available at Aetrix Electronics and suitable for server power supplies, industrial DIN rail converters, gaming PSUs, high-density adapters, and lighting drivers requiring stable component supply and long-term production continuity.

Supply support for UCC29950 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

Texas Instruments is a global semiconductor leader specializing in analog, embedded processing, and power management ICs, with decades of expertise in high-reliability power conversion solutions.

The UCC29950 belongs to TI's high-efficiency AC/DC controller product line, designed specifically for compact, high-power-density offline power supplies targeting 80 PLUS Titanium/Gold server, industrial, and computing applications.

FAQ

What is the primary function of the UCC29950?

The UCC29950 is a single-chip combo controller that manages both a continuous conduction mode (CCM) boost power factor correction (PFC) stage and a half-bridge LLC resonant DC-to-DC stage. It integrates gate drivers, voltage/current sensing inputs, protection logic, and startup circuitry - enabling complete AC-to-DC conversion in one SOIC-16 device. The UCC29950 performs real-time coordination between PFC and LLC stages to optimize efficiency, transient response, and standby power.

How does the UCC29950 achieve low standby power?

The UCC29950 achieves low standby power (<150 mW) through three integrated features: (1) self-bias startup using an external depletion-mode MOSFET controlled by SUFG/SUFS pins, eliminating lossy startup resistors; (2) high-impedance AC line sensing (9.3 MΩ) minimizing quiescent current; and (3) active X-capacitor discharge circuitry triggered automatically during AC removal. These functions are implemented internally - no external components are needed to meet IEC 62368-1 discharge requirements or DOE Level VI standards.

Can the UCC29950 operate in both self-bias and auxiliary bias modes?

Yes, the UCC29950 supports both self-bias and auxiliary bias operation via the MD_SEL/PS_ON pin. When pulled high at power-up, it enters self-bias mode - using SUFG/SUFS to control an external depletion FET for VCC charging from the rectified AC line. When held low ≥10 ms at startup, it enters auxiliary bias mode - accepting external 11–18 V bias from an auxiliary winding or small SMPS. In aux bias mode, the same pin also serves as PS_ON to independently enable PFC-only or PFC+LLC operation.

What protection features does the UCC29950 include?

The UCC29950 includes comprehensive system-level protection: AC line brownout detection (AC_DET output), PFC bus over/under-voltage lockout, three-level LLC over-current protection (OCP1/OCP2/OCP3) with hiccup-mode recovery, thermal shutdown at 125°C, PFC input current limiting, active X-cap discharge, and VBLK sensing network fault detection. All protections are hardware-based with no firmware dependency - ensuring fail-safe behavior under fault conditions.

Is the UCC29950 pin-compatible with other TI PFC+LLC controllers?

No, the UCC29950 is not pin-compatible with other TI combo controllers such as the UCC28950 or UCC25630x series. Its SOIC-16 pinout is unique - featuring dedicated SUFG/SUFS pins for depletion-FET startup, differential AC1/AC2 inputs, and dual LLC gate drivers (GD1/GD2) alongside PFC_GD. Substitution requires PCB layout revision and firmware revalidation due to differences in control architecture, protection thresholds, and functional pin assignments.