Dual voltage hot swap module power control

#In many telecom and information technology applications, hot pluggable modules are desired. A hot pluggable module is an electronic module that provides any number of different functions, but which can be plugged into a system without removing power from the system. In other words, it can be inserted into a hot or powered receptacle that is designed to couple the module to the system.

#Modules for telecom applications may need to operate from either a +24 volt or −48 volt power supply provided at the receptacle and therefore need to correct the polarity of the supply. They should exhibit minimum power losses or heat dissipation, and should provide for dual voltage (24 and 48) start-up/shutdown threshold control. Such modules should also provide some form of start-up delay and should control or limit their inrush current. Further, the modules should hold up during supply drop-out; that is, block reverse current flow.

#Existing power input circuits for modules can be quite complex, yet do not provide all of these desired features.

#FIG. 1 is a simplified block diagram showing functional elements of a circuit for providing hot swapping of modules for dual supplies according to an example embodiment.

#FIG. 2 is a circuit diagram illustrating most of the circuit of FIG. 1 according to an example embodiment.

#FIG. 3 is a circuit diagram of a comparator for operating with the circuit of FIG. 2 according to an example embodiment.

#In the following description, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific embodiments which may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that structural, logical and electrical changes may be made without departing from the scope of the present invention. The following description of example embodiments is, therefore, not to be taken in a limited sense, and the scope of the present invention is defined by the appended claims.

#FIG. 1 is a block diagram showing functional elements of a circuit 100 for providing hot swapping of modules into dual supplies according to an example embodiment. In one embodiment, the hot swap circuit includes a rectifier 110 adapted to receive either positive voltage or a negative voltages of different absolute values at input 115. A voltage sensor 120 is coupled to the controller 125, which provides dual startup/shutdown voltage thresholds and controls inrush current limiting 130, to provide power to an output 135, which is normally a DC-DC converter 155 and a bulk energy storage capacitor 150. A detector 140, or comparator, detects input voltage drop-outs and shuts off the rectifier 110 to prevent reverse current flow.

#In one embodiment, the rectifier comprises a FET bridge that is adapted to receive input voltages of approximately 24 volts and −48 volts. Other voltages may also be received in further embodiment. In one embodiment, the detector 140 shuts off the FET bridge 110 as a function of detected reverse current flow or input voltage drop-out.