Control circuit for a direct current motor

A control circuit for controlling an operation of a two-speed DC motor having three brushes, the two-speed DC motor having a first input and a second input and configured to operate at a first speed and a second speed different than the first speed, the two-speed DC motor powered by a battery, the control circuit comprising:

• a first speed switch unit disposed on a first communication line and configured to connect the battery to the first input;
• a second speed switch unit disposed on a second communication line and configured to connect the battery to the second input, the second speed switch unit including a first switch and a second switch, wherein a polarity of the first switch is the opposite of a polarity of the second switch;
• a braking switch unit connected to the second communication line and interposed between the second speed switch unit and the second input, the braking switch unit configured to connect the two-speed DC motor to a ground to stop an operation of the two-speed DC motor;
• a free-wheeling diode connected to the first communication line and in parallel with the two-speed DC motor, the free-wheeling diode configured to dissipate current through the second input of the two-speed DC motor;
• and
• a discharge diode disposed on the second communication line and interposed between the braking switch unit and the two-speed DC motor, the discharge diode configured to discharge a predetermined voltage to protect the braking switch unit from a voltage surge of the two-speed DC motor, wherein one of the braking switch unit and the discharge diode is further configured to dissipate current along the second communication line.

A control circuit operatively coupled to a motor control unit configured to generate control signals for operating a windshield wiper motor, the control signals including a low-speed command, a high-speed command, and a brake command, the windshield wiper motor powered by a battery, the windshield wiper motor having three brushes and configured to operate at a low speed when the low-speed command is transmitted, a high speed when the high-speed command is transmitted, and brake when the brake command is transmitted, the windshield wiper motor includes a first input for receiving the high-speed command and a second input for receiving the low-speed command and the brake command, the control circuit comprising:

• a first speed switch unit disposed on a first communication line and configured to connect the battery to the first input when the high-speed command is transmitted;
• a second speed switch unit disposed on a second communication line and configured to connect the battery to the second input when the low-speed command is transmitted, the second speed switch unit including a first switch and a second switch, wherein a polarity of the first switch is the opposite of a polarity of the second switch;
• a braking switch unit connected to the second communication line and interposed between the second speed switch unit and the second input, the braking switch unit configured to connect the windshield wiper motor to a ground upon receiving the brake command;
• a free-wheeling diode connected to the first communication line and in parallel with the windshield wiper motor, the free-wheeling diode configured to dissipate current through the second input of the windshield wiper motor;
• and
• a discharge diode disposed on the second communication line and interposed between the braking switch unit and the windshield wiper motor, the discharge diode configured to discharge current at a predetermined voltage to protect the braking switch unit from a larger surge voltage.