Patent ID: 6119046
Filing Date: 2000-09-12
Classification: H02M,H02P

Abstract:
A method for controlling a chopper driver coupled between a voltage source (V1) and a load (L1) having an inductive component;wherein the chopper driver includes:a bridge circuit having diagonals and branches and further comprisinga first bridge diagonal of the bridge circuit having therein the voltage source,a second bridge diagonal of the bridge circuit having therein the electrical load, andsemiconductors (T1-T4) being disposed in the branches;the semiconductors being switchable on and off by a control signal (B), so as to make an actual current (I.sub.ist) flow in either of two directions through the load;emitter-collector paths of the semiconductors being bridged by free-wheeling arms further comprising recovery diodes (D1-D4) for protection against overvoltage;the recovery diodes permitting either one of a slow current decay mode including a very slow decay of magnetic energy of the load and the actual current, and a fast current decay mode including a rapid decay of the magnetic energy of the load and the actual current, through switching off of individual semiconductors in the bridge branches;the method comprising:providing a device (R.sub.-- mess) for measuring the actual current (I.sub.ist) flowing through the load, the device being connected in series with the load;providing a comparator for making a determination, over a course of each chopper period, whether the measured actual current has attained a predetermined nominal current value (I.sub.soll)selecting between the slow current decay mode and the fast current decay mode as a function of the determination; the step of selecting further comprising:during a magnetization phase, switching on semiconductors, through which the current direction is switched, depending on a desired current flux direction through the load and allowing the actual current to increase until it has attained the nominal current value; and,in a subsequent demagnetization phase, switching into either the slow current decay mode or the fast current decay mode according to a comparison made shortly before, during, or shortly after a last semiconductor switch-on, such that the fast current decay mode is selected if the actual current was higher than the nominal current value, and the slow current decay mode is selected if the actual current value was lower than the nominal current value.