Introduction to over-zero detection, introduction to over-zero circuits

In power electronics, zero-point voltage detection (often referred to as zero crossing detection) is widely used. Through the detection circuit to track the AC voltage change process, in the AC voltage is "zero" moment output signal, using the signal we can do a lot of engineering applications.Over-zero detection is an electronic technique used to detect the zero point of an AC electrical signal. Zero crossing detection is commonly used in the fields of modulation, control, and protection.

---

Over-zero detection is the process of detecting a naturally occurring "over-zero" point in an AC cycle and generating a corresponding electrical signal output. This technique is commonly used in induction heating, choppers, and so on.

The over-zero detection circuit is actually a voltage comparator whose input signal is the source signal for over-zero detection. The principle is to rectify and filter the input signal and then compare it with a reference level. When the input signal passes through the zero point, the output signal will jump, this jump is the so-called over-zero point.

Many occasions need to carry out over-zero detection, such as in induction heating needs to detect the frequency and amplitude of the AC signal; chopper control needs to be processed on the input signal, in order to get the correct chopper output and so on.

Over-zero detection is the process of detecting a naturally occurring "over-zero" point in an AC cycle and generating a corresponding electrical signal output. This technique is commonly used in induction heating, choppers, and so on.

Over-zero detection is often used in high-power thyristor control circuits. If there is no control, the power supply voltage just reaches the maximum value when the circuit is cut off or turned on, the impact on the load is very large, high-power loads are more serious. Then the inductive loads or capacitive loads, due to the role of inductance and capacitance will produce instantaneous high pressure and high current, the same impact on the power supply interference is the same, around the normal operation of the load will be affected, contamination of the power supply network. So it is best to turn on and off the action in the power supply voltage value down to 0 or tend to 0.

Another important reason, zero-voltage triggered SCR opening can reduce the opening loss of the SCR. It allows the thyristor losses to be minimized, which can extend thyristor life.

Driving high-power AC devices commonly used bi-directional SCRs for power control, according to the different control methods over the zero control and phase shift control. Regardless of which control should be detected on the zero point, because the characteristics of the bidirectional thyristor is to the zero point of the AC, the thyristor will automatically shut down the output.