Bridge​ stack principle

Bridge stack principle

As a power component, Bridge stack is very widely used in various power supply equipment. Its internal Bridge is mainly composed of four diodes to convert the input AC voltage into the output DC voltage.

　　In each duty cycle of the Bridge stack, only two diodes operate at the same time, and the alternating current is converted into a unidirectional DC pulsation voltage through the unidirectional function of the diode. An anatomy of commonly used low-power Bridge reactors shows that the full-wave Bridge reactor has a plastic package structure (most low-power bridge stacks are in this packaging form). The four main heat-generating components in the Bridge, the diodes, are divided into two groups and placed on the pin copper plate of the DC output. There are two connecting copper plates between the DC output pin copper plates, which are connected to the input pins (AC input wires) respectively, forming the full-wave bridge stack with four external connection pins that we see in the appearance. Since this series of Bridge stacks are made of plastic package structure, the above-mentioned diodes, pin copper plates, connecting copper plates, and connecting wires are filled with epoxy resin, a skeleton filling material that acts as insulation and heat conduction. However, the thermal conductivity of epoxy resin is relatively low (generally 0.35 °CW/m, 2.5 °CW/m), so the knot-shell thermal resistance of the bridge stack is generally relatively large (usually 1.0~10 °C/W).