Overview
When designing hardware for low-to-medium power AC control, engineers often face a practical challenge: traditional through-hole TRIACs consume significant PCB space. As more products adopt SMT (Surface Mount Technology) processes, factors such as component packaging, PCB layout, and production efficiency must be considered holistically.
To address these needs, Semiware has introduced the BT136S-600. This is a 600V/4A four-quadrant SMD TRIAC housed in the industry-standard TO-252 (D-PAK) package. It is suitable for circuits involving AC load switching, phase control, and the control of low-to-medium power motors, heating elements, and lighting systems.
Key specifications of the BT136S-600 include:
- 600V repetitive peak off-state voltage
- 4A on-state RMS current
- 25A non-repetitive peak on-state current
- Maximum junction temperature of 125°C
- Chip manufactured using planar passivation technology, making it ideal for AC control applications requiring high voltage withstand capability and long-term operational reliability
I. Four-Quadrant Triggering Offers Greater Design Flexibility for AC Control Circuits
In practical TRIAC circuit designs, gate triggering conditions are a critical parameter during component selection.
Because AC voltage alternates between positive and negative half-cycles, various polarity combinations arise between the TRIAC's MT1, MT2, and Gate terminals. A four-quadrant TRIAC can operate across all four triggering quadrants, providing engineers with greater flexibility in designing gate drive circuits for various AC control applications.
The BT136S-600 supports four-quadrant triggering. For applications such as dimming, AC power regulation, and other scenarios requiring periodic TRIAC triggering, engineers can select the optimal gate drive method based on the specific circuit requirements, rather than being restricted to a single triggering polarity.
It should be noted that the specific gate drive current must still be determined based on the IGT parameters listed in the datasheet, the triggering quadrant, and the actual operating temperature to ensure reliable triggering across the entire operating range.
II. 600V / 4A: Suitable for a Wide Range of Common Low-to-Medium Power AC Loads
The BT136S-600 features a rated on-state RMS current of 4A and a repetitive peak off-state voltage of 600V.
For low-to-medium power AC control boards, these specifications accommodate many common types of loads, such as:
- Small fans and AC motors
- Water pumps and small actuators
- Heaters and temperature control equipment
- Lighting fixtures and dimming circuits
- Small appliances (e.g., coffee machines, electric heating devices)
- General-purpose AC static switches
When selecting components, one should not rely solely on the load's rated power. For inductive loads—such as motors and transformers—it is also necessary to consider starting current, commutation, and voltage transients generated during turn-off.
III. TO-252 Package: Optimized for SMT Production
Compared to traditional through-hole packages, the BT136S-600 utilizes the TO-252 surface-mount package. This reduces PCB footprint and is better suited for automated placement and mass production.
During actual PCB design, the continuous operating current must be evaluated by considering ambient temperature, load type, device power dissipation, and PCB thermal dissipation conditions.
Engineering Tip: For continuous high-current operation, verify the temperature rise based on the actual PCB copper area and thermal dissipation conditions, and apply derating design principles by referencing the thermal parameters in the datasheet.
For inductive loads, if issues such as false triggering, abnormal turn-off, or waveform irregularities arise during testing, further analysis of load commutation and voltage transients is required; consider adding protection networks, such as an RC snubber, based on the specific application conditions.
IV. BT136S-600 Applications
① Phase Control in Home Appliances
The TRIAC is a common component in AC dimming and power control circuits.
The BT136S-600 can be used for incandescent lamp dimming, fan speed control, and heating power control in small appliances. By controlling the TRIAC's trigger timing, the conduction angle within the AC half-cycle can be adjusted, thereby regulating the average power delivered to the load.
For non-purely resistive loads such as LED lighting, characteristics such as TRIAC triggering, holding current, and EMI performance must be further verified in conjunction with the specific drive circuitry.
② Small AC Motor Control
TRIACs can be used to control the switching or speed of fans, pumps, and other small AC motors.
Unlike mechanical relays, TRIACs have no mechanical contacts, making them suitable for applications requiring frequent switching. However, as motors are inductive loads, significant transients occur during startup and shutdown; therefore, practical designs must evaluate dv/dt, commutation, and inrush current based on load characteristics.
③ General-Purpose AC Static Switching
Within its rated operating range, the BT136S-600 can also serve as a static switch for various low-to-medium power AC loads, such as:
- AC-side control for auxiliary power supplies
- Small fans and pumps
- Solenoid valves
- Small actuators
- Other AC loads requiring frequent switching
In specific applications, appropriate protection and drive circuits should be selected based on load current, inrush current, and operating temperature.
V. Four-Quadrant TRIAC Selection Guide
① Operating Voltage
The 600V VDRM/VRRM rating provides a wide blocking voltage range for AC applications; however, if the circuit is subject to grid surges or transient voltages caused by load switching, an evaluation based on actual waveforms is required.
② Gate Trigger Current
Determine the IGT based on the specific triggering quadrant used, and ensure the gate drive circuit maintains sufficient triggering margin across various temperatures and operating conditions.
③ Load Surge
Significant surge currents may occur during the startup of motors, lighting fixtures, and certain power supply loads. The BT136S-600 has an ITSM of 25A (20ms); this parameter can be used to evaluate short-duration, non-repetitive surges but must not be treated as a continuous operating current.
④ Thermal Design
When the operating current approaches the rated value, particular attention must be paid to the TRIAC's on-state power dissipation and the PCB's heat dissipation capability. It is recommended to conduct temperature rise tests on the final design using the actual PCB and under maximum ambient temperature conditions.
For datasheets, product specifications, and related information, please visit the product page: https://en.semiware.com/4q-triacs/bt136s-600/
If you are working on designs involving AC dimming, motor control, heating control, or AC static switching, please contact Semiware for samples and technical support.
