H-bridge Driver

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Robots need electric motors, and electric motors need motor drivers.

So far I have made a number of prototype drivers for motorized elements that never came to fruition. I made a 8 channel Mini DC motor driver for electronic bolts that would have locked matinace pannels. I also made a crude BLDC prototype for a screw based pannel lock. Ultimately those were abandoned since our mechanical department could not figure out an reliable and cheap electric panel locking mechanism.

Driving Thermoelectric Peltier Coolers

Initially this H-Bridge was designed specifically to drive TEC loads. The only TEC drivers I could find for sale were expensive scietific devices where a precisely temperature controlled surface was needed.

Proper Thermoelectric Peltier cooler driving requires polarity swapping and a constant current supply with low ripple. These coolers generate a lot heat (from resistance inside the cooler) as well and moving heat from one side to the other. There is a sweet spot between generating to much heat, and pumping the most thermal energy.

Because of this, using PWM is not as good as a constant voltage, since the on time is generating a lot of heat even if the average is the correct sweet spot voltage. So a Large LC Filter is placed at the output. Due to the Rining a LC tak circute creates, a large voltage over shoot can occur if the output is switched on to quickly/ It was difficult to meet the spec of 10% worst case ripple, and prevent to uch overshoot. Ulitmutly a software solution was used to limit the slew rate inorder to prevent the large voltage overshoot problem. Firmware modification should not never the PWM slew rate limit unless the load can handle large overshoots.

Control Levels

There are many what I call "control levels" that set PWM, or Constant Voltage, or Constant Current or more.

PWM: Controls the Pules Width of the output and has a maximum slew rate to prevent the LC output filter from overshoot and ringing.

Constant Voltage (Output):Read the two output voltages and A and B and gets the difference, B-A=Output Voltage.

Constant Voltage (Input): Reads the input voltage value (say 24.5V) and then in order to set 12V on the output, it sets the PWM to %48.9. This can be a better choice than CV(output) because complex capacitive and inductive loads will not effect the H-Bridge Control loop leading which could lead to catastrophic unstability. On the other hand, high currents on the output will cause the Output voltage to droop in this mode.

Constant Value This can be a PI Loop that takes any setpoint value IE. RPM, Temp, position, and tries to go to it.

Constant Current Passive: (CCP needs Load Resistance value given to it, then it djust does the math once and sets the voltage

  • PWM
    • Constant Voltage Passive
      • Constant Current Active
        • Constant Value
      • Constant Current Passive
        • Constant Value
    • Constant Voltage Active
        • Constant Value
      • Constant Current Active
        • Constant Value
      • Constant Current Passive