Self-Oscillating Half Bridge Module

This is an automotive-grade self-oscillation 50% duty cycle half-bridge module built using the AUIR2085S chip from Infineon. The project consists of 2 x N-channel MOSFETs, and the module provides a primary side control solution to enable Half-Bridge DC-bus converters. The module is a self-oscillating half-bridge driver with 50% duty cycle ideally suited for 10V – 15V half-bridge DC-bus converters.   The board is also suitable for push-pull converters. Each channel frequency is equal to f_OSC, which can be set by selecting RT (R2+PR1) & CT-(C7), Dead-time can be controlled through proper selection of C_T range from 50ns to 200ns. Internal soft-start increases the pulse width during power-up and maintains pulse width matching for the high and low outputs throughout the start-up cycle. Typically, the soft-start duty cycle varies beginning from 5-10% ramping up to about 50% over 1000 cycles.  The AUIR2085S initiates a soft start at power up and after every overcurrent condition. Undervoltage lockout prevents operation if V_CC is less than 7.5V.

Features

• Power Supply 10V to 14V DC
• Integrated 50% duty cycle oscillator and half-bridge driver
• Adjustable switching frequency 84Khz to 260Khz
• Undervoltage lockout prevents operation if VCC is less than 7.5V.
• +/- 1A drive current capability optimized for low-charge MOSFETs
• Adjustable dead-time 50ns – 200ns (Read Data Sheet for More Info)
• High and low side pulse width matching to +/- 25ns
• Adjustable overcurrent protection (Shunt Resistor Value)
• Over Current Shut Down Threshold 300mV
• Over Current Shutdown Delay 200nS
• Turn-on Rise Time 40nS
• Turn-off Fall Time 20nS
• Undervoltage lockout and internal soft start
• PCB Dimensions 40.16 x 21.27 mm

Push-Pull Converter Application

The components like transistors Q1, Q2, the external transformer, and the capacitors C4, C5, C9, and C10 make up a so-called single-ended, push-pull converter. This converter operates the potential-isolating transformer with an alternating voltage in which both half-oscillations are used for energy transmission.

Frequency Adjust

A Trimmer potentiometer is provided to adjust the frequency from 84Khz to 200Khz. The module supports higher frequencies up to 500Khz, read the datasheet of the AUIR2185S chip to learn more about frequency and dead time adjustment. For 500Khz Output C_T should be 100pF and R_T 10kΩ.

Applications

• DC-DC Converters, Push-Pull Drivers
• High Voltage Converters
• HEV Auxiliary Converter
• Battery Management Converters

The recommended range of timing resistors R_T is between 10kΩ and 100kΩ and the range of timing capacitor C_T is between 47pF and 470pF. Timing resistor values less than 10kΩ should be avoided. The value of the timing capacitor determines the amount of dead time between the two output drivers: the lower the C_T, the shorter the dead time, and vice versa. It is not recommended to use a timing capacitor below 47pF, for best performance keep the timing components physically as close as possible to the AUIR2085S. Separated ground and VCC traces to the timing components are encouraged.

Connections

• CN1: Pin 1 Output 2, Pin 2 Output 1 (for Push-Pull)
• CN2: Pin 1 VCC, Pin 2 GND
• PR1: Oscillator Adjust
• D1: Power LED

Schematic

Parts List

Connections

Block Diagram

Typical Application

Frequency Diagram

Gerber View

Photos

Video

AUIR2085S Datasheet

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