Abstract: The DC switching power supply protection system, protection system design  principles and machine protection measures, an analysis of switching power supply in the range of protected characteristics and its design methodology,introduced a number of practical protection circuit。83938

Keywords: switching power  supply protection  circuit system design 

1、Introduction     

  DC switching regulator used in the price of more expensive high-power switching devices, the control circuit is also more complex, In addition, the load switching regulators are generally used a large number of highly integrated electronic systems installed devices。 Transistors and integrated device tolerance electricity, less heat shocks。 Switching Regulators therefore should take into account the protection of voltage regulators and load their own safety。 Many different types of circuit protection, polarity protection, introduced here, the program protection, over-current protection, over-voltage protection, under-voltage protection and over-temperature protection circuit。 Usually chosen to be some combination of protection, constitutes a complete protection system。

2、polarity protection 

  DC switching regulator input are generally not regulated DC power supply。 Operating errors or accidents as a result of the situation will take its wrong polarity, switching power supply will be damaged。 Polarity protection purposes, is to make the switching regulator only when the correct polarity is not connected to DC power supply regulator to work at。 Connecting a single device can achieve power polarity protection。 Since the diode D to flow through switching regulator input total current, this circuit applied in a low-power switching regulator more suitable。 Power in the larger occasion, while the polarity protection circuit as a procedure to protect a link, save the power required for polarity protection diodes, power consumption will be reduced。 In order to easy to operate, make it easier to identify the correct polarity or not, collect the next light。 

3、procedures to protect 

  Switching power supply circuit is rather complicated, basically can be pided into low-power and high-power part of the control part of the switch。 Switch is a high-power transistors, for the protection of the transistor switch is turned on or off power safety, we must first modulator, amplifier and other low-power control circuit。 To this end, the boot to ensure the correct procedures。 Switching Regulators generally take the input of a small inductor, the input filter capacitor。 Moment in the boot, filter capacitor will flow a lot of surge current, the surge current can be several times more than the normal input current。 Such a large surge current may contact the general power switch or relay contact melting, and the input fuse fuse。 In addition, the capacitor surge current will damage to shorten the life span of premature damage。 To this end, the boot should be access to a current limiting resistor, through the current limiting resistor to capacitor charging。 In order not to make the current limiting resistor excessive power consumption, thus affecting the normal switching regulator, and the transient process in the boot after a short period then automatically relays it to DC power supply directly to the switching regulator power supply。 This circuit switching regulator called a "soft start" circuit。

  Switching regulator control circuit of the logic components required or op-amp auxiliary power supply。 To this end, the auxiliary power supply must be in the switch circuit。 This control circuit can be used to ensure the boot。 Normal boot process is: to identify the polarity of input power, voltage protection procedures → boot → auxiliary power supply circuit and through current limiting resistor R of the switching regulator input capacitor C → charge modulation switching regulator circuit, → short-circuit current limiting resistor stability switching regulator。