Introduction to the Power Pole Board

The HiRel Power Pole board has five major sub-circuit areas that are labeled in Fig. 1. (Areas labeled in Fig. 1 are approximate.) The first area (red) includes the primary side which has filter capacitors, a current sensor, and connectors labeled "V1" and "COM," which can connect to a DC voltage source or load. Fig. 2 shows a zoom in at the first area with labeled components.

The second area (yellow) includes the secondary side, which has filter capacitors, a current sensor, and connectors labeled "V2" and "COM," which connect to a DC voltage source or the load shown as a planar power resistor. Fig. 3 shows a zoom in at the second area with labeled components. Either the first or second area can be used to connect to a DC voltage source, e.g. DC power supply, while the other connects to a load. Note that when the second area is connected to a source, the load resistor can be unsoldered from the board or left without having impact on the converter's operation as it would be directly fed from the DC voltage source.

The third area (green) is the power-pole area, where two MOSFETs and two diodes are connected. The first "leg" includes an upper MOSFET and a lower diode, while the second "leg" includes an upper diode and a lower MOSFET. The actual components of the upper MOSFET and diode are mounted on the same heat sink in the green rectangle of Fig. 1 on the top left side, while the lower MOSFET and diode are mounted on the same heat sink on the bottom left side in the green rectangle in Fig. 1. A zoom-in view on that area is shown in Fig. 4. The other small green rectangle includes gate drivers that take a low-power switching pulse, e.g. pulse-width-modulated signal, and convert it to the appropriate voltage levels that can turn the MOSFETs on and off.

The fourth area (blue) has four connecting points where a daughter board that includes a magnetic component can be mounted. Two boards are used with this board for the DC/DC converter experiments: the first board is the BB board, shown in Fig. 5, which includes an approximate 100 µH inductor; and the second board is the flyback board, shown in Fig. 6, which includes a flyback coupled inductor or transformer along with its R-C-Diode snubber circuit. The snubber circuit helps provide a path for the stored energy of the primary transformer side in one of the flyback converter's operating modes.

The fifth area includes low-power electronics that generate switching pulses to the MOSFETs, and provide protection to the board including over-current and over-voltage protection. A separate DC power supply is connected to the bottom left of the board, next to switch "S90" which turns on power to all of the low-power circuits so that the high-power side, i.e. areas 1-4, can function properly. The external DC power supply and its connector that plugs in to the Power Pole board are shown in Fig. 7 and 8, respectively.

Figure 1: HiRel Power Pole Board with Five Major Areas Please click here to view a larger version of this figure.

Figure 2: Zoom-in of Area 1.

Figure 3: Zoom-in of Area 2.

Figure 4: Zoom-in of Area 3.

Figure 5: BB Board.

Figure 6: Flyback Board.

Figure 7: External power supply for the low-power electronics.

Figure 8: External power supply connector.

A PWM pulse is expected to be seen on the oscilloscope screen. The duty cycle is a major control variable for DC/DC converter as it adjusts the period during which a MOSFET or any other semiconductor actively-controlled switch is on. All input-output voltage relationships of DC/DC converters rely on the value of this duty ratio, along with some other variable in some converter topologies.

The switching frequency is critical in component selection as the maximum operating frequency of components varies by component type and design. Higher switching frequencies typically yield smaller voltage and current ripples but require larger capacitors and inductors.

DC/DC converters are very common in DC power supplies used to charge electronics, and to supply power to many other electronic circuits. For example, any motor drive will require some smaller DC power supplies to power its low-power electronics, protection circuits, and high-power gate drives. Computer processors and other peripherals and accessories require very well-regulated DC voltages that are provided by DC power supplies. Renewable energy systems, e.g. solar photovoltaic panels, require DC/DC converters to regulate the DC output voltage of the panels, since solar irradiance and ambient temperature vary causing variation in the solar panel's voltage and current outputs. Many more industrial, transportation, military, and other applications use DC/DC converters instead of linear regulators due to their high efficiency, high performance, and excellent regulation.