1. Application Background

Switching power supplies can overheat under abnormal conditions, risking damage or fire, particularly in high-power devices over 100W and outdoor LED applications. Overheat protection is critical, especially in environments with poor heat dissipation, such as mining lamps.

2. Protection Principle

The thermal protector is a mechanical passive component placed in the control loop. It uses a bimetallic strip to sense temperature changes, deforming to disconnect the circuit. This shifts resistance from 50 mΩ to infinity, signaling the IC or MCU to turn off the main current via a MOSFET or other components. When temperatures normalize, the switch resets, allowing current to flow again.

3. Installation Position

• Near Power Tube: Attach the switch with a heat shrink sleeve to the power tube, which has the highest heating temperature (ideally below 130?).
• Transformer: Place near the transformer coil to monitor temperature changes.
• PCB Board: Use a switch with pins to insert into the PCB, sensing ambient temperature.
• Heat Sink: Attach to the heat sink surface using thermal silicone or fit into a slot for direct contact.
• Chassis Inner Wall: Secure with a metal bracket.

4. Type Selection

• Volume:

  • Larger model: BW-BCP (1573.5mm)
  • Smaller model: BW-ECP (125.52.4mm), typically used in ultra-thin power supplies.

• Current:

  • BW-BCP rated at 5A
  • BW-ECP rated at 2A, both suitable for signal currents.

• Protection Temperature: Range of 85? to 130?, adjustable in 5? increments. Choose higher temperatures (115? - 125?) near power tubes and lower (85? - 90?) for external surfaces.

• Contact Switch Form:

  • Normally Closed: Contacts are closed at initial state, open upon reaching protection temperature.
  • Normally Open: Contacts are open at initial state, close upon reaching protection temperature.

  Models: Normally Closed - BW-BCP and BW-ECP; Normally Open - BW-BOP and BW-EOP.

This thermal protector ensures reliable operation and safety for high-power applications, preventing overheating incidents effectively.