The core of electro-hydraulic proportional control is to control current. The current from the analog control power output stage to the proportional valve coil is continuous, and the power device has a large power consumption, so it needs to install a cooling device. The PWM control power output stage is a switching structure with low power consumption. PWM signal contains the pulsation of the same frequency, no need to add a flutter signal, anti-interference and anti-pollution ability, short lag time, high repetition accuracy; Because of the use of numerical control, it is convenient to connect with the computer and can realize program control.

The proportional electromagnet can generate the corresponding electromagnetic force according to the size of the current, so that it can be controlled proportionally.

Using advanced controllable PWM technology, variable switching voltage is generated on the output circuit, so that the power amplifier tube is only in a saturated on-off state, so the power is low, no heat sink is needed, which can improve the power amplifier output switching voltage U and shorten the time of current rise, so that the output response is accelerated, and improve the anti-interference ability, on the other hand, the power amplifier voltage U is added to the proportional electromagnet On the coil, due to the inductance effect on the coil, its current I becomes the DC current of superimposed AC signal with small amplitude charge and discharge fluctuations, which plays a flutter and can effectively reduce friction, reduce hysteresis and dead zone phenomenon, and improve the sensitivity of the electromagnet. The effect of the flutter depends on the frequency and amplitude of the current fluctuation. The effect is obvious when the frequency is low and the amplitude is large, but when the frequency is too low and the amplitude is too large, the system will be unstable. The square wave frequency is usually selected in the range of 1.2 ~ 2 times the undamped natural frequency of the electromagnetic core.