Diodes Incorporated AP3917DEV2

Overview

AP3917DEV2 from Diodes Incorporated is an evaluation board implementing a dual-output off-line AC/DC power solution using the AP3917D controller IC, delivering 18V/250mA (buck) and 5V/50mA (flyback) simultaneously from universal 85–264V_AC input. It integrates a 700V MOSFET, supports non-isolated buck and isolated flyback topologies on a shared two-winding transformer, and targets cost-sensitive home appliance auxiliary power.

For engineers reviewing the AP3917DEV2 datasheet, AP3917DEV2 pinout, AP3917DEV2 application, or AP3917DEV2 equivalent, this board serves as a validated reference design for dual-rail, low-standby-power AC/DC conversion in non-isolated consumer appliances - with measured efficiency up to 78.6% at 150V_AC, <100mW standby power at 230V_AC, and EN55032/FCC Class B EMI compliance.

Technical Context

The AP3917DEV2 implements a Fly-Buck topology where the AP3917D controller drives both buck and flyback outputs via a single EE10 transformer with 172-turn main winding (buck) and 64-turn auxiliary winding (flyback). Feedback is sampled only from the 18V buck output using resistive divider (R1/R2) and internal 2.5V reference, while the 5V rail is post-regulated by AS78L05 LDO after flyback rectification.

Input EMI filtering uses fusible resistor F1, bridge DB1, and LC network (L1, C1, C2); startup current is drawn from the DRAIN pin via capacitor C3; protection includes OTP (135–165°C), SCP, OLP, and OVD. The board operates across –20°C to +85°C ambient with no heatsink required under full load.

Key Specifications

Availability

AP3917DEV2 is available at Aetrix Electronics and suitable for home appliance auxiliary power, IoT device power supply, and AC fan control systems requiring stable component supply, rapid prototyping validation, and pre-verified EMI performance.

Supply support for AP3917DEV2 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, headquartered in Plano, Texas, with design centers across Asia and manufacturing in China, Taiwan, and the US.

The AP3917D product line delivers highly integrated, low-BOM-count AC/DC controllers for cost-driven home appliance power supplies - emphasizing ultra-low standby power, high light-load efficiency, and simplified transformer design.

FAQ

Is AP3917DEV2 isolated between its 18V and 5V outputs?

No. The 18V buck output shares ground with the primary-side circuitry and is non-isolated. The 5V flyback output is galvanically isolated from the primary side but referenced to the same system ground as the 18V rail - making both outputs common-ground and unsuitable for applications requiring reinforced isolation between rails.

Can AP3917DEV2 be modified to deliver higher 5V current?

Not without redesign. The 5V output is limited to 50mA by the flyback winding's turns ratio, diode D4 (ES1J), and post-regulator AS78L05 (rated 100mA max). Increasing current would require rewinding T1, upgrading D4 to a higher-current ultrafast diode, replacing U2 with a higher-current LDO or DC/DC, and revalidating thermal and regulation performance.

What safety certifications does AP3917DEV2 meet?

The board itself is not certified, but its design complies with EN55032 Class B conducted emissions and passes basic immunity tests (ESD ±8kV contact, ±15kV air; EFT 4kV; surge 1kV differential). It is intended for use in Class II (double-insulated) end equipment where final system-level safety certification (e.g., UL/IEC 62368-1) must be performed on the complete appliance.

Does AP3917DEV2 support adjustable output voltages?

Only the 18V output can be adjusted - by changing R1/R2 feedback divider values to set different V_FB = 2.5V thresholds. The 5V output is fixed by the AS78L05 LDO; altering it requires replacing U2 with a different fixed-voltage LDO or adding external feedback resistors if using an adjustable variant (not populated on EV2).