When using the Si9986, as with using any motor driver, a snubber circuit is required to reduce electromagnetic noise in the system.

It is a great solution for controlling a small DC motor using a PWM signal from a microcontroller. The Si9986 IC from Vishay is an H-bridge motor driver circuit with built-in shoot-through protection as well as logic translation circuitry (Q5A and Q5B in the diagram above). The easiest way to implement a shoot-through prevention circuit is to use an integrated circuit (IC) that has shoot-through protection built-in. To overcome this problem additional circuitry must be added to ensure Q3 turns completely off before Q1 starts to turn on. This causes efficiency to plummet and introduces heating problems in the transistors. For a brief period, both Q1 and Q3 are partially on allowing current to flow from the supply to the ground. For example, when the PWMA input signal switches from high to low, Q1 turns on and Q3 turns off. While using PWM is simple, it introduces a problem called shoot-through which occurs when current flows directly from the power supply to the ground when the transistors are being switched. For example, if the motor supply is 12V, the motor can be driven at 6V by applying a 50% duty cycle where half the time 12V is applied, and half the time 0V is applied as shown by the green signal in the plot below. PWM works by rapidly turning the motor on and off. Most microcontrollers have dedicated PWM hardware, but an output compare timer can also generate a PWM signal. PWM is a simple way to vary the voltage applied to the motor. Our How Microcontrollers Work post illustrates how to use NMOS and PMOS transistors to build logic gates such as NOT, AND, OR, etc. Most logic gates are designed using NMOS and PMOS in a complementary way. In the logic world, this is known as CMOS circuitry. The H-bridge uses NMOS and PMOS resistors in a complementary fashion. The motor direction can be reversed by toggling PWMA and PWMB. The circuit works by setting PWMB to logic zero (Q2 on Q4 off) and then setting PWMA to logic high (Q1 off Q3 on). A typical H-bridge circuit with logic scaling circuitry is shown above.Įach side of the H-bridge has two transistors with the gates tied together resulting in complementary operation–Q3 is always off when Q1 is on and vice versa. To maximize efficiency, the transistors are driven at a higher voltage than the microcontroller. Several design challenges include preventing shoot-through, implementingĪ snubber circuit, as well as open and closed loop (such as PID) controlĪn H-bridge circuit consists of four transistors (usually two PMOS’s and two NMOS’s). With pulse-width modulation (PWM) from a microcontroller to vary Bi-directional motor control can be done using an H-bridge circuit

Pid controller labview