Diodes Incorporated AP3128S-13

Overview

AP3128S-13 from Diodes Incorporated is a peak-current-mode, multi-mode (QR + CCM) PWM controller for offline flyback converters, featuring 105 kHz maximum clamp frequency, 22 kHz burst-mode operation to suppress audible noise, and integrated valley detection (DEM pin) for quasi-resonant switching. It delivers <0.25 mA operating current in burst mode and supports universal AC input with internal line compensation for constant output power limit.

For engineers reviewing the AP3128S-13 datasheet, AP3128S-13 pinout, AP3128S-13 application, or AP3128S-13 equivalent, key selection criteria include QR/CCM mode transition behavior, SOVP/SUVP protection via DEM pin, FOCP with 1.2 V threshold and 7-cycle debounce, and HV pin startup capability up to 700 V - all critical for PD3.0 PPS charger and STB auxiliary supply designs.

Technical Context

The AP3128S-13 implements a multi-mode control architecture that dynamically transitions between burst mode (22 kHz fixed), QR mode (20–105 kHz with frequency foldback), and CCM mode (72–88 kHz) based on load and line voltage. Valley detection at the DEM pin enables zero-voltage switching at primary MOSFET turn-on, reducing switching loss and EMI.

It integrates piecewise linear line compensation to maintain constant output power across 90–264 VAC input, plus comprehensive fault handling: cycle-by-cycle OCP with 0.56 V typical CS threshold, SOVP (3.2 V) and SUVP (0.4 V) triggered via DEM sampling, and internal OTP with 150 °C trip and 25 °C hysteresis.

Key Specifications

Pinout & Package

AP3128S-13 is housed in an SO-8 (Type A1) package with exposed pad thermal enhancement, RoHS-compliant matte tin plating, and moisture sensitivity level 1. The 8-pin layout supports compact flyback transformer integration and PCB-level thermal management.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar PWM controller applications.

Compared with NCP1342DR2G and ICE2QS03G, the AP3128S-13 uniquely combines QR+CCM adaptability, HV pin self-start, and DEM-based secondary protection - enabling single-chip, opto-free designs meeting latest energy standards and acoustic requirements.

Availability

AP3128S-13 is available at Aetrix Electronics and suitable for cell phone chargers, PD3.0 PPS adapters, and Set-Top Box power supplies requiring stable component supply, long-term lifecycle support, and RoHS-compliant manufacturing.

Supply support for AP3128S-13 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

Diodes Incorporated is a global manufacturer of discrete semiconductors and analog ICs, specializing in power management, signal integrity, and protection solutions for consumer, computing, and industrial markets.

The AP3128 belongs to Diodes' Green Mode PWM Controller product line, engineered specifically for high-efficiency, low-standby-power offline flyback converters targeting USB-C PD, STB, and auxiliary power applications.

FAQ

What is the purpose of the HV pin on the AP3128S-13?

The HV pin accepts up to 700 V DC and provides initial startup current to charge the VCC capacitor directly from the rectified AC line. This eliminates the need for an external high-voltage startup resistor, reducing power loss and component count in flyback designs. During normal operation, the HV pin draws negligible current.

How does the DEM pin enable secondary-side protection without opto-coupler feedback?

The DEM pin monitors the voltage across the VCC winding during MOSFET off-time. Since this winding's waveform is proportional to the output voltage, the AP3128S-13 compares the divided DEM voltage against internal SOVP (3.2 V) and SUVP (0.4 V) thresholds. When exceeded, it triggers auto-recovery shutdown - providing accurate secondary protection using only primary-side components.

Can the AP3128S-13 operate in continuous conduction mode (CCM) at high line voltage?

No - CCM mode is only activated at low line voltage and heavy load, when QR frequency drops below 80 kHz. At high line voltage, the controller remains in QR mode (valley 1 or 2 switching) to maintain ZVS and minimize switching loss. This behavior is inherent to its multi-mode architecture and cannot be forced into CCM at high line.

What is the function of the NC pin (Pin 7) and how should it be handled on the PCB?

Pin 7 is a no-connect terminal with no internal bond wire or circuitry. It must remain unconnected on the PCB - neither routed nor tied to ground or any other net. Solder mask should fully cover the pad to prevent accidental shorting, and the footprint must match Diodes' SO-8 (Type A1) mechanical drawing to ensure mechanical compatibility.