Current Controlled Driver for 24V DC Solenoid
Created: Aug 02, 2016
No description available.
Circuit breakers, relays and other devices, which protect a whole circuit from drawing excessive current that can damage electronic device are categorize as overcurrent protection devices. These protective devices use electromechanical solenoids for their operation. Solenoid coils are rated to operate from 12-V to 24-V DC and 110-V to 230-V AC systems with a power consumption ranging from 8 to 20W. A solenoid that is operating with a nominal current of 30% (steady state) consistently raises the temperature in the coil to higher power dissipation. This reference design provides a solution to control the solenoid current using DRV110, a PWM current controller for solenoids, as well as monitor the proper operation of the plunger in valves using pulse width modulation-based (PWM) controllers along with a Back-EMF sensing circuit.
The operation of the reference design starts by applying input voltage or through a digital input signal (EN) pin. When the solenoid is starting to energize, DRV110 allows current to ramp up to the peak value IPEAK and regulates it at the peak value for the time tKEEP, to ensure correct operation. The current then is reduced to IHOLD in order to avoid thermal problems and to reduce power dissipation. The pin J4 is the input for 24V DC supply, which is followed by a fuse, and a metal oxide varistor for surge protection. The L1 and C5 form the power filter, while D6 is used for reverse polarity protection. The OUT pin of DRV110 sends the gate pulses to the external MOSFET. The header J3 is the connector for solenoid terminals and Q4 is the power-switching device. The resistors connected to pin PEAK and HOLD set the peak and hold current together, C7 is the capacitor that sets the duration of peak current. The capacitor C7 will be shorted by Q2 until the plunger has moved to its intended position, after which C7 can charge thereby transitioning from peak current to hold current. The sensing IC TLV271IDBVR detects the back-emf that is being produced. The difference between the peak and the valley of the solenoid current is due to back-emf remains constant despite of changing temperature, thus this difference is used as threshold to detect the movement of the plunger of the solenoid valve. The detection of the valley point is interpreted by the sensing circuit as the end of the movement of the plunger.
The DRV110 is primarily used in applications that involved electromechanical drivers like solenoids, valves, and relays. By using this IC, power dissipation can be minimized and thus results to power wise utilization.