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Home > Products > Discrete Semiconductor Products > Transistors > Bipolar (BJT) > Single Bipolar Transistors

STMicroelectronics BUL310

Name: BUL310
Brand: STMicroelectronics
SKU: BUL310
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BUL310

Manufacturer:: STMicroelectronics

Category:: Single Bipolar Transistors

Package:: TO-220-3

Datasheet:: BUL310.pdf

Description:: TRANS NPN 500V 5A TO-220

Quantity:: RFQ Add To RFQ list

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Inventory:2,893

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Product details

Overview

BUL310 from STMicroelectronics is a high-voltage fast-switching NPN power transistor designed for electronic ballasts and low-power flyback/forward SMPS. It features V_CEO = 500 V, I_C = 5 A continuous, P_tot = 75 W at T_c = 25 °C, t_f = 80 ns (typ.), and full characterization at 125 °C - enabling reliable operation in fluorescent lamp drivers.

For engineers reviewing the BUL310 datasheet, BUL310 pinout, BUL310 application, or BUL310 equivalent, key selection criteria include RBSOA robustness under inductive switching, dynamic parameter consistency across lots, V_CE(sat) stability at 2–3 A, and thermal resistance (R_thj-case = 1.65 °C/W) for TO-220 heatsink integration.

Technical Context

The BUL310 employs Multi Epitaxial Planar technology with cellular emitter and planar edge termination to simultaneously achieve high voltage blocking (V_CES = 1000 V) and fast switching (t_s = 1.2 µs, t_f = 80 ns). Its wide reverse-biased safe operating area (RBSOA) supports inductive load transients up to 250 V with L = 200 µH.

Characterized at T_j = 125 °C, it delivers stable h_FE ≥ 6 at I_C = 3 A and V_CE = 2.5 V, and V_CE(sat) ≤ 0.7 V at I_C = 2 A / I_B = 0.4 A - critical for efficiency in low-cost SMPS where base drive margin is constrained.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	500 V - Sustains 500 V collector-emitter voltage with zero base current, suitable for 230 VAC offline flyback primary switches.
I_C	5 A continuous - Supports up to 5 A DC collector current at T_c = 25 °C, enabling 30–40 W SMPS designs.
t_f	80 ns typ. - Fast fall time minimizes switching loss during turn-off in 20–100 kHz ballast and converter applications.
R_thj-case	1.65 °C/W - Enables direct mounting to heatsinks; junction-to-case thermal path allows T_j ≤ 150 °C at 45 W dissipation.
h_FE	6 min. @ I_C = 3 A - Ensures sufficient current gain for low-base-drive-cost circuits without active base control.
V_CE(sat)	0.7 V max. @ I_C = 2 A / I_B = 0.4 A - Limits conduction loss to <1.4 W, improving efficiency in thermally constrained ballasts.

Pinout & Package

Supplied in TO-220 package (standard 3-lead, insulated tab), with collector connected to the metal tab for direct heatsinking. Pin 1 = Emitter, Pin 2 = Base, Pin 3 = Collector (tab).

Pin/Terminal	Circuit Role	Design Meaning
Pin 1 (Emitter)	Current return path	Low-inductance connection point for emitter degeneration or current sensing; referenced to ground in common-emitter configurations.
Pin 2 (Base)	Control input	Receives TTL/CMOS-compatible drive; requires 0.4 A peak for full saturation at 2 A collector current.
Pin 3 (Collector / Tab)	Main power output	Electrically tied to metal tab - must be electrically isolated from heatsink unless circuit design permits common-collector topology.

Key Features

Feature	Design Value
Cellular Emitter Structure	Enables uniform current distribution and reduced localized heating during high-current switching pulses.
Planar Edge Termination	Improves voltage ruggedness and prevents premature edge breakdown at V_CES = 1000 V.
Full 125 °C Characterization	Guarantees parametric performance (h_FE, V_CE(sat), t_s) over full industrial temperature range without derating assumptions.
Low Lot-to-Lot Spread	Ensures consistent dynamic parameters (e.g., t_f ±15%, V_CE(sat) ±0.1 V) across production batches for BOM stability.

Applications

Fluorescent Lamp Electronic Ballast

Flyback SMPS (≤40 W)

Use Scenario: High-frequency (20–60 kHz) resonant inverter driving 36–40 W T8/T12 lamps with dimming and end-of-life protection.

IC Role / Device Role / Timing Role: Main switching transistor in half-bridge or single-ended topology; handles repetitive 500 V inductive flyback spikes.

Use Value: Wide RBSOA and 125 °C-rated t_f = 150 ns ensure survival during lamp ignition and filament open-circuit faults.

Use Scenario: Universal-input (85–265 VAC), isolated 24 V/1.5 A output adapter for consumer electronics.

IC Role / Device Role / Timing Role: Primary-side switch in discontinuous conduction mode (DCM); operates at 65 kHz with 50% duty cycle.

Use Value: Low V_CE(sat) (0.7 V) and fast t_f reduce total switching + conduction loss to <1.8 W, enabling >82% efficiency without forced air cooling.

Forward Converter (Low-Power)

DC-DC Boost Pre-regulator

Use Scenario: 12 V input, 48 V/0.8 A output telecom module requiring tight regulation and transient response.

IC Role / Device Role / Timing Role: Main switch in forward topology with reset winding; clamped to 500 V by snubber network.

Use Value: Stable h_FE ≥ 6 at 3 A ensures predictable base drive requirements across temperature, simplifying gate driver design.

Use Scenario: Input stage of LED driver accepting 12–24 VDC input, boosting to 40 V for constant-current string control.

IC Role / Device Role / Timing Role: Power switch in boost converter operating at 100 kHz; handles 5 A peak inductor current.

Use Value: RBSOA validated to 250 V × 5 A enables safe operation during output short-circuit recovery without secondary overvoltage stress.

Equivalent & Alternatives

The following parts are listed as comparable options for similar high-voltage NPN switching transistor applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
BU508A	V_CEO = 1000 V, I_C = 8 A, t_f = 200 ns - higher voltage rating but slower switching.	Better suited for line-frequency rectifier snubbers; less optimal for >50 kHz ballasts due to higher switching loss.	Choose when V_CE stress exceeds 500 V but switching frequency <30 kHz.
ST13007	V_CEO = 400 V, I_C = 8 A, t_f = 300 ns - lower voltage, higher current, significantly slower.	Targeted at cost-sensitive 115 VAC-only SMPS; not rated for 230 VAC flyback primary use.	Select only for 100–120 VAC input designs where V_CE peak <400 V and thermal margin >20 °C.

Compared with BU508A and ST13007, the BUL310 uniquely balances 500 V ruggedness, sub-100 ns switching, and 125 °C-rated SOA - making it the preferred choice for compact, thermally constrained 230 VAC fluorescent ballasts and universal-input flyback converters.

Availability

BUL310 is available at Aetrix Electronics and suitable for electronic ballasts for fluorescent lighting, flyback and forward single-transistor low-power converters, and DC-DC boost pre-regulators requiring stable component supply and long-lifecycle support.

Supply support for BUL310 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, designing and manufacturing analog, power, microcontroller, and sensor solutions for industrial, automotive, and consumer markets.

The BUL series was developed specifically for cost-sensitive, high-reliability lighting and low-power SMPS applications - emphasizing lot-to-lot consistency, RBSOA robustness, and high-temperature operational validation.

FAQ

Is BUL310 suitable for 230 VAC offline flyback converters?

Yes. With V_CEO = 500 V and validated RBSOA up to 250 V at 125 °C, the BUL310 safely handles reflected output voltage plus leakage spike in universal-input (85–265 VAC) flyback topologies. Its 80 ns t_f and 1.2 µs t_s minimize switching loss at 65 kHz, supporting >80% efficiency in 25–40 W designs without active snubbing.

What is the recommended heatsink interface for BUL310 in TO-220?

A mica washer + thermal grease or silicone pad (0.2 mm thick, k ≥ 1.5 W/m·K) is required between the insulated tab and aluminum heatsink. The R_thj-case = 1.65 °C/W assumes full tab contact; adding 0.5 °C/W interface resistance keeps T_j ≤ 135 °C at 40 W dissipation with a 2°C/W heatsink.

Does BUL310 support base drive from standard CMOS logic?

No. At I_C = 2 A, it requires I_B = 0.4 A for saturation - far exceeding CMOS output capability. A dedicated bipolar or MOSFET-based driver (e.g., ULN2003 or TC4420) is mandatory. Base resistor calculation must account for V_BE(sat) = 1.1 V at 2 A to avoid underdrive.

How does BUL310's RBSOA compare to BU208A in inductive switching?

BUL310's RBSOA extends to 250 V × 5 A at 125 °C with t_p ≤ 10 ms, while BU208A is only specified to 200 V × 3 A. This wider safe area enables reliable operation in fluorescent lamp ignition (high dI/dt, open-filament fault) and flyback transformer reset without secondary clamping diodes.

BUL310 Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: TO-220-3

Packaging:: Tube

Product Status:: Obsolete

Transistor Type:: NPN

Current - Collector (Ic) (Max):: 5 A

Voltage - Collector Emitter Breakdown (Max):: 500 V

Vce Saturation (Max) @ Ib, Ic:: 1.1V @ 600mA, 3A

Current - Collector Cutoff (Max):: 250µA

DC Current Gain (hFE) (Min) @ Ic, Vce:: 6 @ 3A, 2.5V

Power - Max:: 75 W

Frequency - Transition:: -

Operating Temperature:: 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: TO-220

BUL310 FAQ

1.How can I place an order for BUL310 through Aetrix?

Please submit a Request for Quotation (RFQ) for BUL310 on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.

2.Are the price and stock information for BUL310 reliable?

The price and inventory of BUL310 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BUL310 is usually 5 days.

3.What payment methods are accepted for BUL310?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BUL310 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BUL310?

BUL310 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BUL310 order is processed, you will receive an email with the shipment details and tracking number.

Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.

5.How can I obtain technical support or documentation for BUL310?

For technical support, including BUL310 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BUL310 requirements.

6.How does Aetrix verify that BUL310 is sourced from the original manufacturer or authorized distributors?

All BUL310 products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that BUL310 meets industry standards.

7.What is the process for return or replacement of BUL310?

All BUL310 units undergo pre-shipment inspection (PSI). If there is an issue with BUL310, returns or replacements are accepted under the following conditions:

1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.

2.The issue is reported within 90 days of delivery.

3.The BUL310 part is unused and in its original packaging.

Return procedure for BUL310:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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