H-Bridge Motor Controller Power Supply Circuit – Reference Design

The TN90002 reference design from Nexperia is a full bridge dc-dc converter allowing operation of a brushed dc motor (48V max, 12V min, 5A max). The control circuit operates with input voltages from 12- to 48-V for motors up to 250W.

The key feature of this design is that all electronic functions are designed with automotive qualified Nexperia discretes, MOSFETs and logic components (cost-effective, no microcontroller or software needed).

In addition, this H-bridge motor controller PCB allows the user to choose between three Nexperia MOSFET package options (LFPAK33, LFPAK56D or LFPAK56).

Design Features

• A switch selects the motor rotation direction.
• Jumpers select one of 3 switching frequencies: 7.8kHz, 15.6kHz or 31.3kHz.
• Two tactile push buttons allow the duty cycle (motor speed) to be increased or decreased. There are 8 steps from 0 to 100% duty cycle. A current limitation protection avoids over current in the motor and MOSFETs (set at approximately 6.5A).

Subsystems overview

1. Power Supply
   1. Accepts 12V to 48V dc input
   2. Transient overvoltage protection
   3. Reverse polarity protection
   4. Buck converter (12V)
   5. Linear regulator (5V) for logic devices
2. Clock and duty cycle generator
   1. 4MHz crystal oscillator and frequency divider to create 3 different switching frequencies
   2. Duty cycle sets by push button inputs to select the duty cycle (0% to 100%)
   3. 5kHz output is used to supply the charge pump on the driving circuitry block
3. PWM
   1. Reset function to activate other function when VCC 5V supply is stable
   2. Dead-time function and PWM enable (over current protection disabling)
   3. Level shifter
   4. Direction selection
4. Driver circuit
   1. High-side and low-side drivers to drive 4 MOSFETs of the full bridge
   2. Charge pump to supply the high-side MOSFETs
5. H-bridge
   1. Reservoir and decoupling capacitors
   2. Snubber on the left MOSFETs (switching MOSFETs)
   3. Jumper to connect the selected MOSFETs
   4. Gate drive resistors
   5. Low-side current measurement
6. Overcurrent detection
   1. Comparator, with voltage reference setting current limit
   2. PWM reset function reactivating PWM if fault disappears