| 摘要 |
Overload protection circuitry for an electric motor (4) driving circuit (3) has a first current detection arrangement (r4, 10h, 10i, 10l) for detecting a maximum permissible current flowing to the driving circuit (3). The circuitry is such that when a maximum permissible current is detected current delivery operation of the driving circuit (3) is terminated (for example through comparator 10i, flip-flop 10l closing AND gates 94g to 94l to turn off current delivery transistors Q1 to Q6). The circuitry also has a second current detection arrangement (r1, r2, r3, 10a, 10d) for detecting a preselected overcurrent value flowing from the drving circuit (3). The circuitry is such that when the preselected overcurrent value is detected current delivery from the driving circuit is limited (for example through comparator 10a, resetting flip-flops 93a, 93b and through AND gates 94a, 94b to turn off current delivery transistors Q1 and Q2 which are then repeatedly turned back on and off by pulse generator 96, setting flip-flops 93a, 93b to pass a limited current).
<??>The result is that when a momentary surge of input current to the driving circuit occurs the driving circuit is closed down to prevent damage. When the motor (4) is overloaded, however, current continues to pass to the motor (4) but is limited so as not to cause damage. |
