Control circuit for a dc motor

Details Control circuit for a dc motor Control circuit for a dc motor

1999-06-02

2001-11-20

Nappi, Robert E. (Department: 2837)

Electricity: motor control systems

Closed loop speed control system for dc motor with commutator

Field control, or field and armature control, by digital or...

C318S287000

Reexamination Certificate

active

06321031

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a control circuit for a direct-current motor driven in a clocked manner, having an electrolytic capacitor connected in parallel and a free-wheeling diode.
BACKGROUND INFORMATION
Such a control circuit is assumed to be known. In such a known control circuit, in the connecting lead of the motor supply voltage there are inductances in the form of chokes on the positive and negative sides to smooth out the voltage waveform caused by the clocking and to reduce the spurious radiation. These chokes must be configured for relatively high currents and an associated power loss so that they have relatively large dimensions and are also correspondingly expensive.
SUMMARY OF THE INVENTION
The underlying object of the present invention is to provide a control circuit in which the spurious radiation can be effectively reduced with more favorable circuit-engineering measures.
First of all, provision is made for a choke to be connected between the positive motor supply voltage and the plus terminal of the electrolytic capacitor, and the free-wheeling diode is disposed with its cathode between the choke and the electrolytic capacitor, and with its anode on the negative side of the d.c. motor.
Secondly, provision is made for a choke to be connected between the negative motor supply voltage and the minus terminal of the electrolytic capacitor, and the free-wheeling diode is disposed with its anode between the choke and the electrolytic capacitor, and with its cathode on the positive side of the d.c. motor.
This arrangement of the choke in conjunction with the free-wheeling diode and the electrolytic capacitor has the benefit that it can be configured for only relatively low currents, e.g.,
6
A (unlike conventional chokes of
30
A), significantly smaller dimensions and a reduction in costs being obtained as a result.
If, in addition, a polarity reversal protection device is provided, then a circuit arrangement is advantageous which is designed such that an inversely operated n-channel power MosFet [MOSFET] is connected as a polarity reversal protection device between the choke and the positive supply voltage, or rather which is designed in the alternative, such that an inversely operated n-channel power MOSFET is connected as a polarity reversal protection device between the choke and the negative supply voltage.


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