What are the principles of fiber laser cutting machine
Overview of the 6DC-DC converter of the fiber laser cutting machine. Through this CPU board failure maintenance and reference materials, the working principle, structure and application principle of the DC-DC converter in the electronic circuit are explained.
The DC-DC converter is a voltage converter that pulses the DC input voltage and outputs different DC voltage levels, commonly known as switching power supplies. DC-DC converters are divided into step-up type, step-down type and multi-level positive and negative voltage type. The DC-DC converter is composed of a control chip, an inductor, a diode, a field effect tube, and a capacitor. It is a schematic diagram of a typical inductive step-down DC-DC converter.
VIN is the input voltage, VOUT is the output voltage, V is the P-channel FET, L is the energy storage inductor, VD is the freewheeling diode, C is the filter capacitor, R1 and R2 are the voltage divider resistors, Take the partial pressure error feedback signal FB between R1 and R2. The FB signal is processed by the control circuit, and the FET trigger pulse is dynamically adjusted to stabilize the VOUT output voltage at the set value.
The basic working principle of the fiber laser cutting machine of the step-down DC/DC converter is that the field effect tube works in the on-off state under the control of the trigger pulse of the control circuit. When the FET is turned on, VIN modulates the output pulse voltage by the FET, and the energy storage inductor L and capacitor C form a loop. The charging current not only establishes a DC voltage at both ends of C, but also generates left and right sides on the energy storage inductor L. Negative back electromotive force; during the FET cut-off period, since the current in the energy storage inductor L cannot change suddenly, L generates right positive and left negative pulse voltages through self-inductance. Thus, the positive voltage at the right end of L→the filter capacitor C→the freewheeling diode VD→the left end of L constitutes a discharge circuit, the discharge current continues to establish a DC voltage across C, and the DC output voltage VOUT obtained at both ends of C supplies power to the load. Therefore, the output voltage generated by the step-down DC-DC converter is not only small in ripple, but also low inverse peak impulse voltage of the field effect tube. Its working principle is divided into two types according to pulse modulation mode. PFM (Pulse Frequency Modulation Method): In this method, when the pulse width is constant, the output voltage can be stabilized by changing the pulse output time. PWM (Pulse Width Modulation Method): In this method, the pulse frequency is constant, and the output voltage is stabilized by changing the pulse width. The PFM pulse modulation method has the advantage of low power consumption when the load is small. The PWM modulation method has high conversion efficiency and good output voltage ripple and noise. The PWM/PFM composite type implements PFM control when the load is light, and automatically switches to PWM control when the load is heavy.
After the theoretical study of the DC-DC converter, combined with the failure of the DC-DC converter, the possible cause of the failure is the reduced efficiency of the components.
(1) The thermal stability of the control chip decreases, which may cause the trigger pulse amplitude to be insufficient or gradually attenuate, resulting in a decrease or cut-off of the FET output.
(2) The performance of the modulation field effect tube is degraded, which directly causes the output to decrease or not to work.
(3) Decreased output capacitance or leakage,
will cause poor load capacity or no output. In the electrical maintenance of equipment, we must first understand the working principle and functional composition of the equipment system. In the absence of system data, we must carefully observe the failure process and analyze the current operating status of each functional part at the time of the failure, and use the troubleshooting method to divide the failure according to the failure phenomenon area. When repairing the circuit board, do not blindly replace the components that have not been diagnosed as damaged. As far as possible, survey and map the electrical schematic diagram of the faulty part, analyze the working principle, and make observation and analysis records. At the same time, pay attention to consulting related materials to replace a damaged component and learn to understand a circuit The function and design of the system can accumulate knowledge, enrich maintenance experience and improve the ability of analyzing and judging problems.