STMicroelectronics STCH02TR

Overview

STCH02TR from STMicroelectronics is an offline quasi-resonant (QR) PWM controller IC designed for primary-side constant current (CC) regulation in ultra-low standby AC-DC flyback converters. It integrates a 650 V HV start-up circuit with zero power consumption, supports ZVS operation, delivers <10 mW standby power at 230 Vac, and operates up to 260 kHz with intelligent frequency jittering for EMI suppression - enabling compliance with stringent energy standards in compact smartphone and tablet adapters.

For engineers reviewing the STCH02TR datasheet, STCH02TR pinout, STCH02TR application, or STCH02TR equivalent, this device is selected for high-efficiency, mains-independent CC regulation without secondary-side sensing - requiring attention to ZCD timing, HV start-up sequencing, burst-mode threshold tuning, and OVP hysteresis configuration in adapter-level design.

Technical Context

The STCH02TR implements current-mode control with transformer demagnetization sensing via the ZCD pin to enable zero-voltage switching (ZVS) turn-on, using a programmable blanking time (3.8–24 µs) that scales with feedback voltage. Its internal 650 V HV start-up generator charges VDD autonomously until 13 V, then shuts down to eliminate static loss - reactivating only when VDD drops below 10 V, ensuring continuous operation during CC regulation when auxiliary winding voltage collapses.

It features dual-mode protection: hiccup-mode OCP triggered at 0.95–1.05 V on SENSE, and adjustable output overvoltage protection (OVP) with 2.375–2.625 V threshold sampled-and-held at ZCD end-of-demag. Line feedforward compensation (RFF = 60–80 Ω) enables mains-independent CC regulation by scaling peak current with rectified input voltage.

Key Specifications

Pinout & Package

STCH02TR is housed in an SO-8 package (8-pin, surface-mount, 150 °C/W junction-to-ambient thermal resistance), compliant with JEDEC MS-012AC and RoHS. Pin 2 is NC (not internally connected) for safety clearance; all ground returns must be routed to Pin 6 (GND) with minimal loop area.

Key Features

Applications

Equivalent & Alternatives

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

Compared with NCP1342 and ICE2QS03G, STCH02TR uniquely combines 650 V HV start-up, primary-side CC regulation, and <10 mW standby in one SO-8 package - reducing system BOM, improving cold-start robustness, and eliminating optocoupler aging concerns in long-life consumer adapters.

Availability

STCH02TR is available at Aetrix Electronics and suitable for smartphone charging adapters, tablet auxiliary supplies, camcorder AC-DC chargers, and IoT gateway standby rails requiring stable component supply, full production status since November 2016, and guaranteed lifecycle support through 2030.

Supply support for STCH02TR 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, designing and manufacturing microcontrollers, power ICs, sensors, and analog devices for automotive, industrial, and consumer markets.

The STCH02TR belongs to ST's STCH family of offline QR controllers engineered specifically for ultra-low standby, primary-side regulated AC-DC adapters - prioritizing integration, efficiency, and regulatory compliance over legacy discrete bias solutions.

FAQ

What is the minimum input voltage required to initiate HV start-up on STCH02TR?

The HV start-up circuit activates when the voltage on Pin 1 (HV) exceeds the HVSTART threshold of 40–60 V (typ. 50 V). This corresponds to ~57 V DC rectified input, achievable from ~40 V RMS AC - enabling reliable cold-start down to 85 Vac nominal input with sufficient bulk capacitor hold-up.

Can STCH02TR operate without an auxiliary winding for VDD supply?

Yes - the integrated 650 V HV start-up circuit can sustain VDD indefinitely by recharging the capacitor whenever voltage drops below 10 V. However, auxiliary winding is still required for normal operation above light load to avoid excessive HV generator duty cycle and thermal stress during extended CC regulation.

How does STCH02TR achieve mains-independent constant current regulation?

It uses voltage feedforward via the ZCD pin: the current sourced by ZCD during MOSFET conduction is proportional to input voltage, allowing internal scaling of the current-sense threshold. This compensates for variations in peak current caused by line voltage changes - maintaining ±5% CC accuracy from 85–265 Vac.

What protection features are implemented in autorestart mode?

STCH02TR implements autorestart for overvoltage protection (OVP), hiccup-mode overcurrent protection (OCP), and thermal shutdown. After fault detection, it halts switching, discharges VDD below 4.5 V, then restarts the HV start-up sequence - repeating until fault condition clears, preventing latch-up and enabling safe field recovery.