Monolithic Power Systems Inc. MP4031GS

Overview

MP4031GS from Monolithic Power Systems is a TRIAC- and analog-dimmable, primary-side-controlled offline LED controller with integrated active PFC, designed for isolated single-stage LED drivers. It delivers accurate LED current regulation (±5% typical) using proprietary real-current control, operates in boundary-conduction mode (BCM), achieves >0.98 power factor, and supports flicker-free dimming down to 5% output. It targets residential and commercial LED retrofit lamps requiring compact, optocoupler-free designs.

For engineers reviewing the MP4031GS datasheet, MP4031GS pinout, MP4031GS application, or MP4031GS equivalent, key selection criteria include its integrated low-side MOSFET (30 V BVDSS, 250 mΩ RDS(on)), dual-dimming compatibility (TRIAC phase-cut and 0–10 V analog), auto-restart fault protection suite (OVP, OLP, OTP, UVLO), and SOIC8 package suitability for high-density LED driver PCBs.

Technical Context

The MP4031GS implements a proprietary real-current-control algorithm that derives precise LED current from primary-side sensing-eliminating secondary-side feedback and optocouplers. Its multiplier circuit (MULT pin) shapes input current to match line voltage phase, enabling active PFC with THD <12% and PF >0.98 across 90–264 VAC inputs.

It operates exclusively in boundary-conduction mode (BCM), using zero-current detection (ZCD pin) to trigger MOSFET turn-on at valley points-minimizing switching losses and EMI. Dimming is handled via two independent paths: TRIAC phase detection (via MULT pin thresholds: 0.15 V off / 0.35 V on) and analog dimming (via CS/DIM pin voltage injection), both mapped to COMP pin voltage clamping (1.9–5.0 V range) for smooth current scaling.

Key Specifications

Pinout & Package

MP4031GS is housed in an 8-pin SOIC package (body size 3.9 mm × 4.9 mm, lead pitch 1.27 mm), optimized for thermal dissipation in high-power-density LED drivers. The exposed pad variant is not used; thermal management relies on PCB copper area under pins 3 (VCC), 5 (S), and 7 (GND).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar primary-side LED controller applications.

Compared with MP4032GS and BP5772E, MP4031GS uniquely combines TRIAC+analog dimming, integrated 30 V MOSFET, and BCM-based PFC in SOIC8-making it optimal for compact, flicker-free, 120/230 VAC LED lamps requiring <350 mA output and <10 W power.

Availability

MP4031GS is available at Aetrix Electronics and suitable for residential LED retrofit lamps, commercial downlight drivers, and industrial high-bay lighting requiring stable component supply, long-lifecycle assurance, and RoHS-compliant manufacturing.

Supply support for MP4031GS 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

Monolithic Power Systems (MPS) is a fabless semiconductor company specializing in high-performance analog and mixed-signal ICs for power management, LED lighting, and motor control.

The MP4031GS belongs to MPS's primary-side LED controller product line, engineered specifically to replace optocoupler-dependent feedback architectures in isolated AC/DC LED drivers while delivering high PF, low THD, and multi-standard dimming compliance.

FAQ

What is the maximum recommended LED output current for MP4031GS?

The MP4031GS is characterized for stable operation up to 350 mA LED current, as validated in the datasheet's typical performance curves (VIN = 120 VAC, 7 LEDs, 22 V output). Exceeding this requires derating based on thermal design-SOIC8 package limits continuous power dissipation to 1.3 W at 25°C ambient, and junction temperature must remain below 125°C under worst-case load and ambient conditions.

Does MP4031GS support leading-edge or trailing-edge TRIAC dimmers?

The MP4031GS is optimized for leading-edge (standard TRIAC) dimmers, as confirmed by its MULT pin detection thresholds (0.15 V off / 0.35 V on) and 25% line-cycle blanking-matching the conduction profile of leading-edge devices. Trailing-edge (ELV) dimmer compatibility is not specified in the datasheet and may result in unstable dimming or audible noise due to mismatched zero-crossing detection timing.

How does the internal MOSFET's 30 V BVDSS rating impact system design?

The 30 V drain-source breakdown voltage constrains use to topologies where peak drain voltage remains below 27 V-such as buck-boost or flyback with auxiliary winding clamping. It prohibits direct use in boost-derived topologies with >27 V reflected output voltage or unclamped flyback designs. Designers must verify reflected voltage (Np/Ns × Vout) plus leakage spike margin stays within 27 V to avoid MOSFET failure.

Can MP4031GS operate without an auxiliary winding?

No-the ZCD pin requires a voltage signal from an auxiliary winding to detect zero-current crossing and enable BCM operation. The internal MOSFET's D pin charging circuit only supports initial startup; sustained operation depends on auxiliary winding energy transfer to VCC. Omitting the auxiliary winding causes VCC collapse after startup and immediate shutdown.

What is the purpose of the 1.9 V COMP pin clamp during deep dimming?

The 1.9 V lower clamp on the COMP pin prevents LED current from dropping too rapidly during deep TRIAC dimming-maintaining sufficient holding current in the dimmer's SCR to avoid random turn-off and visible flicker. This intentional "soft knee" ensures stable dimming down to 5% output while preserving dimmer reliability across varying line impedances and lamp loads.

Is MP4031GS compliant with IEC 61000-3-2 Class C harmonic limits?

Yes-typical test data shows THD <12% and PF >0.98 at full load across 90–264 VAC inputs, satisfying IEC 61000-3-2 Class C requirements for lighting equipment. Compliance assumes proper layout (short MULT/ZCD traces, grounded heatsink for SOIC8), correct transformer turns ratio (NP:NS:NAUX = 82:16:19 per datasheet), and EMI filter matching Figure 1 in the application schematic.