Activation of a synchronous rectifier

Abstract

A rectifier bridge circuit is described for rectifying the phase voltage generated by a generator, including a positive half-bridge having multiple rectifier elements and a negative half-bridge having multiple rectifier elements. The rectifier elements each have a controllable switch having a diode connected in parallel. A control circuit is provided for switching the switches on and off. The switch-on time t switch on setpoint and/or the switch-off time t switch off setpoint of the switch is/are computed based on a characteristic map or a mathematical function.

What is claimed is: 
     
         1 . A rectifier bridge circuit for rectifying the phase voltage generated by a generator, including a positive half-bridge having multiple rectifier elements and a negative half-bridge having multiple rectifier elements, the rectifier elements each having a controllable switch having a diode connected in parallel, and a control circuit being provided for switching the switches on and off, wherein the switch-on time t switch on setpoint  and/or the switch-off time t switch off setpoint  of the switch is/are computed based on a characteristic map or a mathematical function. 
     
     
         2 . The rectifier bridge circuit as recited in  claim 1 , wherein the characteristic map or the mathematical function has as input parameters the generator rotational speed ng, or the generator rotational speed ng and the excitation current IE, or the generator rotational speed ng and the excitation current IE and the generator voltage UG, or the generator rotational speed ng and the excitation current IE and the rotational angle phi of the rotor. 
     
     
         3 . The rectifier bridge circuit as recited in  claim 1 , wherein the characteristic map or the mathematical function has as input parameters the generator rotational speed ng and the ratio of the switched-on duration to the theoretical maximum switched-on duration (commutation time). 
     
     
         4 . The rectifier bridge circuit as recited in  claim 2  or  3 , wherein the characteristic map or the mathematical function has as additional input parameters the change in the generator rotational speed ng, or the change in the generator rotational speed ng and the change in the excitation current IE, or the change in the generator rotational speed ng and the change in the excitation current IE and the change in the generator voltage UG, or the change in the generator rotational speed ng and the change in the excitation current IE and the change in the rotational angle phi of the rotor. 
     
     
         5 . The rectifier bridge circuit as recited in  claim 1 ,  2 ,  3 , or  4 , wherein the value t switch on  which is computed from the characteristic map or the mathematical function is used within the scope of a control. 
     
     
         6 . The rectifier bridge circuit as recited in  claim 1 ,  2 ,  3 , or  4 , wherein a controller is present which adjusts t switch off  based on t switch off setpoint  and t switch off actual . 
     
     
         7 . The rectifier bridge circuit as recited in one of the preceding claims, wherein the controller controls more rapidly at a low rotational speed and/or small excitation currents. 
     
     
         8 . The rectifier bridge circuit as recited in one of the preceding claims, wherein the controller-based switch-on time is set to zero when the switch-on time of the switch exceeds the commutation time. 
     
     
         9 . The rectifier bridge circuit as recited in one of the preceding claims, wherein the derivative action within the characteristic maps or the mathematical function is greater for smaller excitation currents and/or lower rotational speeds. 
     
     
         10 . The rectifier bridge circuit as recited in one of the preceding claims, wherein the switch-on time of a switch is ascertained using a comparator. 
     
     
         11 . The rectifier bridge circuit as recited in  claim 10 , wherein the diode forward voltage is used as the input variable for the comparator, and the switch is controlled at 0.7 V forward voltage, preferably 0.35 V diode forward voltage. 
     
     
         12 . The rectifier bridge circuit as recited in one of preceding  claims 1  through  5 , wherein a regulation minimizes the switched-off duration t switch off  to a value t switch off min . 
     
     
         13 . The rectifier bridge circuit as recited in  claim 12 , wherein the controller-based switch-on time is set to a value t switch on setpoint  based on the characteristic map or the mathematical function when the switch-on time of the switch exceeds the commutation time, the derivative action defining the percentage ratio of t switch off setpoint  to the total commutation time.