The BT151-500R is an industry-standard, planar passivated Silicon Controlled Rectifier (SCR / Thyristor) encapsulated in a TO-220AB plastic power package. Designed for high thermal cycling performance and reliable bidirectional blocking, the BT151-500R delivers a repetitive peak off-state voltage rating of 500V, an RMS on-state current of 12A, high surge capability (up to 120A), and sensitive gate triggering. It is widely used in phase control, AC power regulation, capacitive discharge ignition (CDI), solid-state relays, and over-voltage crowbar protection circuits.

Specifications

• Brand / Manufacturer: WeEn Semiconductors / NXP / Philips / Industry Standard
• Part Number: BT151-500R
• Device Type: Silicon Controlled Rectifier (SCR / Thyristor)
• Repetitive Peak Off-State Voltage (V_DRM): 500V
• Repetitive Peak Reverse Voltage (V_RRM): 500V
• RMS On-State Current (I_T(RMS)): 12A (at T_mb ≤ 109°C)
• Average On-State Current (I_T(AV)): 7.5A (Half sine wave)
• Non-Repetitive Peak On-State Surge Current (I_TSM): 120A (at t = 10ms half-sine) / 132A (at t = 8.3ms)
• Gate Trigger Current (I_GT): 2mA (Typical) to 15mA (Maximum at T_j = 25°C, V_D = 12V)
• Gate Trigger Voltage (V_GT): 0.6V (Typical) to 1.5V (Maximum at T_j = 25°C)
• Holding Current (I_H): < 20mA>j = 25°C)
• Latching Current (I_L): < 40mA>j = 25°C)
• On-State Voltage Drop (V_T): < 1>T = 23A, T_j = 25°C)
• Critical Rate of Rise of Off-State Voltage (dV/dt): 50V/µs to 250V/µs
• Operating Junction Temperature: -40°C to +125°C
• Package / Case: TO-220AB (3-Pin Through-Hole: Pin 1: Cathode, Pin 2: Anode, Pin 3: Gate, Mounting Tab: Anode)

Features

• High Voltage Blocking (500V): Provides safe blocking voltage capability for 110V/230V AC mains line applications.
• High Current & Surge Robustness: Handles up to 12A continuous RMS current and 120A non-repetitive surge inrush currents.
• Planar Passivated Chip: Ensures high thermal stability, long-term reliability, and low reverse/off-state leakage currents.
• Sensitive Gate Triggering: Triggers reliably with gate currents as low as 2mA to 15mA, allowing easy drive from optocouplers and pulse transformers.
• Robust TO-220AB Thermal Package: Metal mounting tab provides direct low-resistance thermal contact to external heatsinks.

Common Applications

• Phase-Controlled AC Power Regulators: Speed control for universal AC motors, resistive heater controls, and light dimmers.
• Capacitive Discharge Ignition (CDI): Fast, high-energy pulse discharge for small engine ignition and strobe systems.
• Over-Voltage Crowbar Protection: Rapid shorting of DC power supply outputs to protect sensitive downstream loads during over-voltage faults.
• Battery Chargers & Rectifier Bridges: Controlled rectification stages in AC-DC battery chargers and welding power equipment.
• Solid-State AC/DC Relays & Static Switches: High-reliability contactless AC line switching without contact bounce or arcing.

Usage Tips

• Pinout Identification: Looking at the front marked face with pins pointing downward, the pinout is Pin 1: Cathode (K), Pin 2: Anode (A), and Pin 3: Gate (G). The metallic mounting tab is internally connected to the Anode (Pin 2).
• Heatsink Electrical Isolation: If mounting to a grounded metal chassis or heatsink, always use a silicone/mica thermal insulator and insulating shoulder washer to prevent short-circuiting the Anode rail.
• Gate Drive Current: Ensure the gate pulse provides at least 15mA to 30mA of drive current with a fast rise time to guarantee instantaneous and uniform latching across the silicon die.
• RC Snubber Protection: Place an RC snubber network (e.g., 0.1µF in series with 47Ω) across the Anode and Cathode when switching inductive loads to prevent false dV/dt triggering from line voltage transients.

Datasheet