STMicroelectronics STCH02

Overview

STCH02 from STMicroelectronics is a current-mode quasi-resonant (QR) PWM controller IC for offline flyback converters, integrating a 650 V HV start-up cell and primary-side constant current (CC) regulation. It delivers ultra-low standby power (<10 mW at 230 Vac), supports ZVS operation, features adaptive frequency jitter (9 kHz, 5% ΔI_pk), and operates in QR/valley-skipping/burst modes across load conditions - enabling high-efficiency AC-DC adapters for smartphones and tablets.

For engineers reviewing the STCH02 datasheet, STCH02 pinout, STCH02 application, or STCH02 equivalent, key selection considerations include its primary-sensing CC regulation architecture, HV start-up capability with zero quiescent consumption, mains-independent output current accuracy, and integrated OVP with autorestart - all critical for energy-compliant low-power adapter designs.

Technical Context

The STCH02 implements a transformer demagnetization-synchronized QR control loop via its ZCD pin, using a negative-going edge trigger (40–80 mV threshold) preceded by arming (80–140 mV), with blanking time scaling from 24 µs to 3.8 µs based on FB voltage. Its internal 650 V HV start-up generator delivers 7 mA typ. charge current until VDD reaches 13 V, then shuts down to <1 µA leakage.

Primary-side CC regulation is achieved through line-voltage feedforward compensation (R_FF = 60–80 Ω), sampling the ZCD pin voltage at demagnetization end for OVP (2.375–2.625 V threshold), and dual-level current sensing (0.75 V cycle-by-cycle, 1 V hiccup OCP). Burst mode activates when FB falls below 0.6 V, with hysteresis of 50–75 mV.

Key Specifications

Pinout & Package

STCH02 is housed in an SO-8 package with standard 1.27 mm pitch, rated for junction temperatures from –40 °C to +150 °C and thermal resistance R_{th j-amb} = 150 °C/W.

Key Features

Applications

Equivalent & Alternatives

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

Compared with NCP1342 and ICE2QS03G, STCH02 uniquely integrates HV start-up, primary-side CC, and intelligent burst/jitter - delivering lower system cost, <10 mW standby, and simplified compliance for modern USB-IF certified adapters.

Availability

STCH02 is available at Aetrix Electronics and suitable for smartphone charging adapters, tablet auxiliary supplies, camcorder AC-DC chargers, and USB-C notebook reference designs requiring stable component supply and full production lifecycle support.

Supply support for STCH02 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

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, specializing in power management, microcontrollers, and analog ICs for industrial, automotive, and consumer markets.

The STCH02 belongs to ST's high-efficiency offline AC-DC controller product line, engineered specifically for ultra-low standby power flyback converters in portable device chargers and energy-compliant adapters.

FAQ

What is the purpose of the HV pin on STCH02?

The HV pin connects directly to the rectified mains voltage and enables the integrated 650 V start-up generator. When voltage exceeds 50 V, it sources up to 7 mA to charge the VDD capacitor - eliminating external start-up resistors and their associated power loss and heat generation. After startup, leakage drops to <1 µA, achieving true zero-power standby enablement.

How does STCH02 achieve primary-side constant current regulation without a secondary current sensor?

STCH02 uses ZCD pin voltage sampling at transformer demagnetization end, combined with input voltage feedforward (via ZCD current magnitude), to infer output current. This eliminates the need for a secondary shunt, optocoupler, or TL431 - maintaining ±3% CC accuracy across 85–265 Vac while reducing component count and board space.

Can STCH02 operate without an auxiliary winding?

Yes - the HV start-up circuit sustains operation even if the auxiliary winding is absent or fails. During CC regulation, when auxiliary voltage drops below VDD operating range, the HV generator re-engages to recharge VDD. However, burst mode disables self-supply, so auxiliary winding design remains essential for ultra-low-noise light-load operation.

What protection features does STCH02 include and how do they behave?

STCH02 integrates autorestart OVP (2.5 V threshold, 4-cycle detection), hiccup-mode OCP (1 V sense threshold), transformer saturation detection via ZCD timing, and adaptive UVLO. All protections enter autorestart mode - cycling VDD between 4.5 V (restart) and 13 V (turn-on) - avoiding latch-up and enabling automatic recovery after fault removal without external circuitry.