subject: Electric Power Supply Reliability Design - Switching Power Supply, Electric Reliability - Electrical [print this page] Abstract: The level of reliability of power supply, not only with the electrical design, but also with the components, structure, assembly, process, processing quality and other factors. Reliability is a design based on the actual engineering application, feedback should be obtained through a variety of experimental data to refine the design to further improve power supply reliability. Keywords: switching power supply deviations
1, switching power supply design steps
Electronic products, especially military power supply design is a systematic, not only to consider the design parameters of the power itself, but also the electrical design, electromagnetic compatibility design, thermal design, safety design, three anti-design and so on. for any even the slightest negligence may lead to the collapse of the entire power supply, so we should be fully aware of the importance of reliability design of power products.
2, Electric Power Supply Reliability Design
2.1 power supply options Centralized power supply system, the deviation between the output and transmission distance because the pressure difference caused by different lower quality of power supply, and application of a single power supply; when the power failure may cause the system to a standstill. Distributed power supply system for power supply units close to the load, improved dynamic response, power quality, transmission loss, high efficiency, energy saving, high reliability, easy to form N +1 redundant power supply system, expansion of power also relatively easy. So the distributed power supply system can meet the high reliability of equipment.
2.2 Topology selection Switching power supply commonly used single-ended forward, single-ended flyback, Double Forward, dual single-ended forward, Double Forward, push-pull, half bridge, all bridges in eight single-ended topology excited, single-ended flyback, dual single-ended forward, push-pull pressure switch tube twice the input voltage in more than a 60% drop if the amount of use, easy to switch selection. In the push-pull and full-bridge topology may be one-way partial magnetic saturation, so that switch is damaged, while the half-bridge circuits for automatic anti-unbalanced, and they would not have such problems. Dual half-bridge circuit of forward and only the power switch of the pressure maximum input voltage, even down by 60% the amount of use, selection switch easier. In high reliability engineering generally use two types of circuit topology .
2.3 Control Strategy Selection In the small power supply, the current-mode PWM control method is widely adopted, it is more voltage control type has the following advantages: by-cycle current limit, faster than the voltage mode control, will not switch over-current Ershi damage, greatly reduce the overload and short circuit protected; excellent Voltage regulation; quick transient response; loop stable, easy to compensation; ripple is much smaller than the voltage-controlled. Production practice shows that the current control type switching power supply 50W output ripple at about 25mV, much better than voltage-controlled. Hard-switching technique for switching losses limitations, 350kHz switching frequency is generally below the resonant soft-switching technology is the application of the principle of the device to switch at zero voltage or zero-current off state, to achieve zero switching losses, which can increase the switching frequency to MHz level, application of soft-switching technology that integrates converter PWM converter and the advantages of both resonant converter, close to the ideal characteristics, such as low switching losses, constant frequency control, appropriate storage component size, wide control range and load range, but the technology is mainly used in power supply, power supply is still on the small and medium technology-based PWM.
2.4 Selection of components Because the components will determine the reliability of power supply, so the choice of components is very important. Failure of components focused on four areas:
(1) manufacturing quality problems
Quality problems caused by the failure has nothing to do with the electrical stress.
