DC Servo Drive Power Supply Design
The DC-DC converter design for the core, to achieve +60 V/20A 220V electricity to power conversion. Power supply design using power factor correction technology to improve the active power; particular power supply design of the computer control interface, and servo system synchronization and timing control to achieve the power to ensure a relatively low voltage of +60 V power output lag. Using multiple measures and twisted pair output filter, thus effectively reducing the output voltage ripple and improve the quality of power output; have the best self-protection and monitoring detection, enhanced security and reliability of power supply.
Power Design
System Structure
220V AC voltage obtained by rectifying and filtering the DC voltage of 320V or so, add to the power module input. Single DC-DC module is generally the maximum output voltage +48 V, +60 V DC to get the output voltage, the module must be obtained in series. Design uses two PH600S280-28DC-DC module (raised to +30 V output), through the series by +60 V output voltage, shown in Figure 1.
DC Servo Drive Power Supply Design
Figure 1 modules in series
Fast recovery diode D1, D2 for the series in the way of protection devices require D1, D2 reverse voltage rating greater than twice the power output voltage and current power supply is greater than twice the rated output current, voltage drop is the wizard should be small. Because it is constituted by two power modules in series power supply system, in a limited package to complete the design has some problems, some of the program modules in series to complete the design using two packages, namely the design of two independent 30V supply, then the external series constitute a +60 V power supply system. This design through rational allocation of space, power up and down in the lid of the installation of a DC-DC module, a cooling means of a metal shell, compact design and installation of technology to the entire power system packaged in a smaller space, so that the power supply size, weight greatly reduced cross-sectional area of only 6 × 9 英寸 2, achieved a small volume of high-power integrated power system design.
Power factor correction measures
Switching power supply bridge rectifier, a large capacitor filter circuit so that the overall performance of the capacitive load, so that 220V AC input current and voltage phase to differ, resulting in low power factor, active power down and produce high harmonic pollution power must therefore be taken Power Factor Correction (PFC) measures. Based on cost control, and application convenience of circuit size and other factors to consider, we use the passive power factor correction measures. Passive PFC simple structure, the overall load characteristics for the power performance of a large capacitor in the filter before the series with a parameter of appropriate power inductors, where the ring used 10mH/8A core inductor. Force balance the overall load characteristics of power supply to ensure power factor of not less than 0.8. Passive PFC inductor and other passive components used, reliable and low cost, and without the need to modify the original electrical design, is the method commonly used PFC.
Design features and key technologies
Computer control and monitoring interfaces
Computer control (Figure 2) functions to ensure that only the computer power supply +60 V/20A send enable signal, servo system of the state, start out, usually no output power. This power supply and servo system synchronization approach, the power consumption, low heat, flexible control and a series of advantages. In a series of power system equipment, power supply, +60 V/20A maximum power consumption, but the minimum heat, temperature minimum, fully proved that the power supply control interface design in the superiority of using the computer.
DC Servo Drive Power Supply Design
Figure 2 Computer Control Interface
Internal power supply provides +60 V for the PC testing interface for real-time detection of binary mode, shown in Figure 3. +60 V input voltage as the test drive optocoupler, optocoupler output as a test port and the computer digital I / O port connections. Under normal circumstances test port is low, once the +60 V output disappear or substantially reduce, optocoupler's output level from low to high transition occurs, provided to the computer I / O port.
DC Servo Drive Power Supply Design
Figure 3 Detection of Interface Computer
Power sequence control
DC motor control system power-on timing problems exist, in general, faster power voltage, while the control circuit voltage level after power control of the establishment will take some time. Without such a power sequence control, the system's instantaneous power, high speed than the low voltage power, control, the establishment level is lagging behind, resulting in the instantaneous power control servo system, motor control appear short rotation particularly in the way bipolar control. The traditional solution through the establishment of high and low voltage power switch to manually control the timing, or the design of electrical control system timing control circuit, this will increase the complexity of the circuit, causing the circuit reliability while reducing costs. In the motor drive power source to solve this problem, a simple and effective measures, the working principle is: CNT-side for the end module enable control, can control the working status of the module, as the output voltage control switch. Optocoupler to control the CNT usually end state. Only increase a coupler, you can solve the power-timing problems. Shown in Figure 2, coupler input terminus of motor control circuit controls the operating voltage +5 V, +60 V power output that will inevitably lag behind the voltage +5 V, achieved the power sequence control, a fundamental solution to the problems mentioned above.
Power protection and electromagnetic compatibility measures
Module has over current, over voltage, thermal protection, using an external potentiometer can be rated output voltage within ± 10% adjustment. In power system design, we rectified high voltage 220V input, +60 V output and other key parts of the use TVS surge absorber and surge transient voltage suppression protection measures for the impact, the way to bypass the protection of the power absorption system, while reducing electromagnetic interference and improve power system reliability and life expectancy.
We experimentally measured +60 V output voltage ripple in 800mV ~ 1000mV, obviously too large. Adjustments in the power system through the terminal and the output capacitor with polyester filter, power-house methods using twisted pair wiring filtering measures, ultimately makes the +60 V power supply output ripple control 200mV ~ 400mV, met +60 V/20A power supply ripple voltage ≤ 600mV application requirements.
Conclusion
DC servo drive dedicated power supply, has not only the traditional sense of switching power supply, it is directly involved in the control of DC motor, its unique computer interface timing control and power control for DC motor drive system in particular, relatively traditional Universal power supply has a clear technological advantage, the technical features of its multi-line motor-driven power system development. The Power Supply has been officially put into use successfully in celestial navigation equipment, a model, functional and practical, easy to control, stable and reliable.