High-Voltage Buck Converter Reference Design for E-Motorcycle BMS Applications

Description

This non-isolated buck converter provides a fixed output of 12 V at 400 mA for BMS applications. It operates over an input voltage range of 50 V_DC–150 V_DC after a start-up greater than 40 V. Operating in Discontinuous Conduction Mode (DCM), this converter utilizes the UCC28730 controller, which is referenced to the switch node. It offers high efficiency and low cost in a compact form factor.

Figure 1-1 Board Photos, Top and Bottom Views.

1 Test Prerequisites

1.1 Voltage and Current Requirements

Table 1-1 Voltage and Current Requirements

Parameter	Specifications
Input voltage range	50 V - 150 V, after > 40 V start-up
Output voltage and current	12V ±3%, 400 mA maximum
Switching frequency	Variable, 83 kHz max
Isolation	No
Controller features	Valley switching, frequency dithering, internal 700-V start-up switch, overcurrent and overvoltage protection

1.2 Required Equipment

Resistive load (resistor decade box), 5 W minimum
Power supply, adjustable, 0 V–200 V and 0.25 A minimum
Oscilloscope and probes
Digital multimeter

2 Testing and Results

2.1 Thermal Images

This thermal image shows the operating temperature of the top side of the board with 120 V_DC input and 12 V at 400-mA output at room temperature and no air flow.

Figure 2-1 Top-Side Thermal Image, 120-V_DC Input, 12 V at 400-mA Output

This thermal image shows the operating temperature of the bottom side of the board with 120-V_DC input and 12 V at 400-mA output at room temperature and no air flow.

Figure 2-2 Bottom-Side Thermal Image, 120-V_DC Input, 12 V at 400-mA Output.

2.2 Efficiency and Power Dissipation Graphs

The following figure displays the efficiency and power dissipation of the converter at input voltages of 60 V_DC, 90 V_DC, 120 V_DC, and 150 V_DC.

Figure 2-3 PMP22557 Efficiency, V_OUT = 12 V.

2.3 Efficiency and Power Dissipation Data

Efficiency data is shown in the following tables.

Figure 2-4 Efficiency Data for V_IN = 60 V, 90 V

Figure 2-5 Efficiency Data for V_IN = 120 V, 150 V.

2.4 Voltage Regulation

The following graph displays the measured output voltage at input voltages of 50 V_DC and 150 V_DC.

Figure 2-6 PMP22557 Voltage Regulation