As the topic suggests, I would like to drive a proportional solenoid valve without using a flyback diode and looking for some industry experience/feedback.
First off, I'm using an off the shelf "smart" low side driver (ST Micro VNL5030J-E) which has the necessary avalanche rating for this to be possible without overheating and damaging the the device. For example, one of the valves that I might be driving would have specifications similar to:
Max current: 1.6A
Coil Resistance: 7.3 Ohms
Coil Inductance: 20 mH
If you look at Figure 15. Maximum demagnetization energy for the VNL5030J-E, these solenoid specifications fall below the maximum rated for the device.
I'd like to mention that I want to avoid the flyback diode for some very specific reasons and it makes life a lot easier. Either way, I'd like to investigate this option.
With that aside, I'm concerned about 2 things that I've identified during Spice simulation.
1) Following the MOSFET avalanche, there is some high frequency ringing as the MOSFET is turning off and the inductive energy has been exhausted. Is this representative in real life situation? Is there some sort of snubber circuit that I can use to minimize EMI?
2) When compared to using a flyback diode, the current profile during the off phase is significantly different. For instance, the flyback diode seems to follow a very similar discharge profile compared to the charge profile (both look like identical RC time constant type waveforms). With no diode, the discharge time is reduced significantly. I'm worried this will affect actual positioning of the valve. Has anyone successfully driven proportional valves like this, can you provide any experience?
Thanks for any insight.
First off, I'm using an off the shelf "smart" low side driver (ST Micro VNL5030J-E) which has the necessary avalanche rating for this to be possible without overheating and damaging the the device. For example, one of the valves that I might be driving would have specifications similar to:
Max current: 1.6A
Coil Resistance: 7.3 Ohms
Coil Inductance: 20 mH
If you look at Figure 15. Maximum demagnetization energy for the VNL5030J-E, these solenoid specifications fall below the maximum rated for the device.
I'd like to mention that I want to avoid the flyback diode for some very specific reasons and it makes life a lot easier. Either way, I'd like to investigate this option.
With that aside, I'm concerned about 2 things that I've identified during Spice simulation.
1) Following the MOSFET avalanche, there is some high frequency ringing as the MOSFET is turning off and the inductive energy has been exhausted. Is this representative in real life situation? Is there some sort of snubber circuit that I can use to minimize EMI?
2) When compared to using a flyback diode, the current profile during the off phase is significantly different. For instance, the flyback diode seems to follow a very similar discharge profile compared to the charge profile (both look like identical RC time constant type waveforms). With no diode, the discharge time is reduced significantly. I'm worried this will affect actual positioning of the valve. Has anyone successfully driven proportional valves like this, can you provide any experience?
Thanks for any insight.