| 摘要 |
1. A constant current source with a pulse generator (IG) which produces a pulse signal (IS) of predetermined frequency and circuit means producing a constant direct current of a value dependent upon the pulse signal (IS), characterised in that the pulse generator (IG) is preceded by a calculating circuit (RS) into which is fed the desired current value of the constant current source and which establishes, from this current value, a frequency of the pulse signal (IS) dependent upon the desired current value ; a counter circuit (ZS) is connected to the output of the pulse generator (IG) and periodically counts the pulses of the pulse signal (IS) from a minimum value to a given maximum value where : the counting value occurs at a first output (16) ; and a short pulse ("0") occurs at a second output (18) during the change from the maximum value to the minimum value of the counting circuit (ZS) ; and a switching arrangement (SI) the first input (17) of which is connected via a digital/analogue converter (DA) to the first output (16) and whose switching input (19) is connected to a second output (18) of the counting circuit (ZS) ; and whose output (23) leads via a filter circuit (C3, R3) to the output (25) of the constant current source ; where the charge balance of the capacitor (C3) is dependent upon the voltage conducted via a recharging capacitor (C1) from the first input (17) ; and the recharging capacitor (C1) is reset via a diode switch (D1, S) during the short pulse ("0") which occurs at the second input (19). |
