Monolithic Power Systems Inc. EVHF500-30-P-00A

Overview

EVHF500-30-P-00A from Monolithic Power Systems is a fully assembled, tested evaluation board for the HF500GP-30 integrated flyback regulator IC. It implements a universal-input (85–265 VAC), isolated 12 V / 2.5 A (30 W) offline power supply using secondary-side regulation, PDIP8-7B-packaged controller with 700 V MOSFET, and built-in protections including brown-in/out, OLP, SCP, OTP, and VCC UVLO/OVP.

For engineers reviewing the EVHF500-30-P-00A datasheet, EVHF500-30-P-00A schematic, EVHF500-30-P-00A test results, or EVHF500-30-P-00A transformer design, this board enables rapid validation of HF500GP-30-based flyback topologies under real-world line/load/thermal conditions while meeting EN55022 conducted EMI limits.

Technical Context

The EVHF500-30-P-00A implements a fixed-frequency current-mode flyback converter with slope compensation, frequency jittering (to reduce EMI peaks), light-load frequency foldback down to f_OSC(min), and burst mode at very light load. It uses PC817A optocoupler and CJ431 shunt reference for precise secondary-side voltage feedback.

Primary-side protection includes programmable input brown-in/brown-out via resistor divider (R6/R7/R8), TIMER latch-off, and internal high-voltage startup current source. The board integrates EN55022-compliant EMI filtering (CX1, LM1, CY1), snubbers (R10/R11/C6/D2 on primary; R14/R15/C9 on secondary), and a custom EF25 transformer with 2.2 mH primary inductance and 150:16:22 turn ratio.

Key Specifications

Availability

EVHF500-30-P-00A is available at Aetrix Electronics and suitable for power supply development, SMPS validation, and compliance testing requiring stable component supply, pre-validated transformer design, and production-ready layout documentation.

Supply support for EVHF500-30-P-00A 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 power ICs, with expertise in DC/DC converters, LED drivers, motor drivers, and AC/DC controllers.

The HF500GP-30 product line targets low-power offline flyback applications-such as adapters, auxiliary supplies, and home appliance power stages-where integration of 700 V MOSFET and controller reduces BOM count and improves reliability.

FAQ

What is the purpose of the RT1 NTC thermistor on the EVHF500-30-P-00A board?

RT1 is a 2 D2-10 NTC thermistor placed in series with the AC input to limit inrush current during power-up. It reduces stress on the bridge rectifier (BD1) and bulk capacitor (C4), preventing fuse (F1) nuisance blowing and extending component lifetime under repeated cold-start conditions.

Can the output voltage be adjusted to 5 V or 15 V using this evaluation board?

Yes-the output voltage is set by the R19/R20/R21 resistor divider network feeding the FB pin of U1. Replacing R19 (38.3 kΩ) and R20 (10 kΩ) with appropriate values recalculates the feedback ratio to achieve 5 V or 15 V while maintaining stability; compensation network (C11/R21) may require minor tuning per application note AN-103.

Does the board support primary-side sensing instead of secondary-side regulation?

No-EVHF500-30-P-00A is configured exclusively for secondary-side control using U2 (PC817A) and U3 (CJ431). The HF500GP-30 IC does not integrate primary-side sensing circuitry; primary-sense variants (e.g., HF500-xx with different suffixes) require separate board designs and are not supported here.

What is the maximum ambient temperature at which the board delivers full 2.5 A output continuously?

Per thermal test data (Rev. 1.1, p.10), the board sustains 2.5 A at 12 V with 85 VAC input up to 45 °C ambient and with 265 VAC input up to 50 °C ambient, measured at the hottest point on the HF500GP-30 IC case. Forced airflow extends capability but is not required for rated operation.

Is the transformer (T1) available as a standalone part from MPS or Emei?

Yes-T1 is an Emei FX0469 custom transformer (spec sheet p.8–9). Emei provides samples upon request via www.emeigroup.com; MPS does not sell T1 separately, but the full winding diagram, turn ratio, core spec (EF25, PC40), and electrical isolation ratings are published for third-party replication.

How is overload protection (OLP) triggered and reset on this board?

OLP is triggered when sensed primary peak current exceeds the over-power compensated threshold; it initiates a programmable delay (set by R16 = 2 kΩ) before shutting down. Recovery is automatic after delay timeout if fault clears; no manual reset or power cycle is needed unless TIMER latch-off occurs due to sustained overload.