US3267301A - Direct current polarity control circuit - Google Patents

Description

a 3,267,301 P tented August 16, 1966 3,267,301 DIRECT CURRENT POLARITY CONTROL CIRCUIT Roy G. Gignac, Roselle, Ill., assignor to Electronic Components Corporation, Addison, 111., a corporation of Illinois Filed Dec. 16, 1963, Ser. No. 330,892 2 Claims. (Cl. 307-127) This invention relates to a circuit for ensuring a consistent polarity across a pair of load terminals for random positioning of a D.C. voltage source across a pair of direct current input terminals.

Direct current polarity control circuits performing the function above described are well known in the art. They generally include a relay and a rectifier in series across :a pair of direct current input terminals, the rectifier effecting energization of the relay for a first relative polarity across the input terminals and eilecting the de-energization of the relay for the opposite relative polarity across said input terminals. The relay is generally provided with double pole, double throw contacts which nor.- mally ensure the proper polarity across the load terminals for the energized and de-energized conditions of the relay respectively, since these conditions of the relay are normally tied in directly with the polarity of the voltage applied to the input terminals. However, this circuit suffers from one important disadvantage which is that failure of the relay to operate in the normal manner due to an open circuit in the relay coil or the like can cause -a voltage of improper polarity to appear across the load terminals, which could seriously damage the load connected to these terminals.

The present invention overcomes this disadvantage by ensuring a proper polarity across the load terminal when the relay is in proper operating condition, and the com plete disconnection of the input voltage from the load terminals in case the relay is not operating. In such case, the load is protected against the presence of a voltage condition across the load terminals which is of an improper relative polarity.

Another important advantage of the invention is that it not only has the functional advantage referred to, but it also results in a substantial reduction in cost of the circuit involved. For example, a cost reduction as much as fifteen percent (15%) can be achieved by utilizing the circuit of the present invention in low current circuits.

The accompanying drawing is a circuit diagram i1lustrating one example of the invention.

An exemplary direct current polarity control circuit of the present invention is identified in the drawing by reference numeral 2. The circuit is arranged to form an integral unit with an input plug connector 4 insertable into a suitable wall or other outlet socket 5 having socket terminals 5a and 5b connected to a suitable source of direct current voltage. The socket terminal 5a is permanently connected to the positive terminal of the voltage source and the socket terminal 5b is permanently connected to the negative terminal. The plug connector 4 has plug terminals 4a and 4b which constitute input terminals to the circuit 2. The circuit 2 has load terminals 6a and 6b across which input terminals 8a and 8b of a suitable load device 8 is connected. It is assumed that the load device is one wherein the input terminal 8a must be positive with respect to the input terminal 8b either to ensure proper operation of the load device 8 or to protect the same from damage and that the plug connector 4 can be inserted into the socket 5 in either one of two positions so that plug connector terminal 4a may be either positive or negative with respect to the plug connector terminal 4b. The direct current polarity control circuit 2 ensures that the load terminal 6a is positive with respect to the load terminal 6b independently of whether plug connector terminal 4a is in contact with socket terminal 5a or 5b.

A bus L1 is connected to plug connector terminal 4a through an on-ofi switch 13 and a bus L2 in connected to the plug connector terminal 4b. A series circuit including a rectifier 12 and the coil of a relay R1 are connected in series between the busses L1 and L2. The anode 12a of the rectifier 12 is connected to the upper end of the relay coil and the cathode 12b of the rectifier 12 is connected to the bus L1. Thus, whenever the bus L1 is positive with respect to the bus L2, the rectifier 12 will block the flow of direct current to the relay coil so that the relay R1 will-remain in a de-energized state. When the bus L1 is negative with respect to the bus L2, the rectifier 12 will conduct direct current to the relay coil to energize the same.

Relay R1 has a movable contact R1-1 which, in the de-energized state of the relay, contacts a stationary contact R1-2 connected by a conductor 15 to the bus L1. In the energized state of the relay R1, the movable contact R1-1 is connected to a stationary contact R1-3 connected by a conductor 17 to the bus L2.

The circuit of the invention is completed by a pair of rectifiers 19 and 21. The cathode 21a of the rectifier 21 is connected to the bus L2 and the anode 21b thereof is connected to the load terminals 6b. Thus, when the relay R1 is de-energized due to the fact that the bus L1 is positive with respect to the bus L2, the path of current flow between the busses includes stationary contact R1-2 connected to bus L1, movable contact R1- 1, load terminal 6a, the load device 8, load terminal 6b and rectifier 21 connected to bus 12. In such case, the load terminal 611 is positive with respect to load terminal 6b.

The cathode 19a of rectifier 19 is connected to the bus L1 and the anode 1% thereof is connected to the load terminal 6b. When the bus L1 is positive with respect to the bus L2, which is the condition when the relay R1 is de-energized, the rectifier 19 is in a non-conductive state because the cathode 19a thereof is positive with re spect to its anode 19b.

When the bus 11 is negative with respect to the bus L2, so that the rectifier 12 will conduct current to energize the relay R1, movable contacts R11 will separate from the stationary contact R1-2 and make contact with the stationary contact R1-3. Then, the path of current flow between the busses L1 and L2 can be traced through the conductive rectifier 19 connected to the bus L1, load terminal 6b, load device 8, load terminal 6a, movable contact R1-1 and stationary contact R1-3 connected to bus L2. In this case also, the load terminal 6a is positive with respect to the load terminal 6b. When the bus L1 is negative with respect to the bus L2, the rectifier 21 is in a non-conductive state because its cathode 21a is then positive with respect to its anode 21b.

One of the main advantages of the invention, as above indicated, is the reliability of the circuit in the event the relay R1 should fail to operate. Thus, if the coil of the relay R1 were to be open circuited, since the relay R1 cannot be energized when the bus L1 is negative with respect to the bus L2, movable contact R1-1 of the relay Rl remains in contact with its stationary contact R1-2 but then will not result in the feeding of the positive voltage on the plug connector terminal 4b to the load terminal 6b which could damage the load device -8 because the rectifier 21, as above indicated, will then be in a nonconductive state because the cathode 21a is positive with respect to the anode 21b and there is no other path for this positive voltage to reach load terminal 6b. Similarly, if for some reason movable contact R1-1 should be come stuck to the stationary contact R1-3 when the relay 'R1 is energized, the subsequent de-energization of the relay will not result in a voltage of improper polarity on the load terminals because the rectifier 19 will block conti-nuity between load terminal 6b and the then positive bus L1.

As above indicated, in' addition to the functional'advantage of the circuit just explained, utilization of the rectifiers 19 and 21 results in a substantial reduction in the cost of the circuit in comparison to a circuit of the type heretofore utilized where the relay R1 was provided with two sets of movable and stationary contacts.

I claim:

1. A direct current polarity control circuit connected between a first and a second direct current input terminal across which a direct current voltage source is to be connected in a random fashion, so that the input terminals may have either one of two relative polarities, and a first and a second load terminal across which a direct current voltage is to be applied having a consistent relative polarity, said circuit comprising: a relay and a first rectifier connected in series across said input terminals for effooting the energizing for said relay when said input terminals have a first relative polarity and the de-energizing of said relay when said terminals have the opposite polarity, said relay having a movable contact connected to said first load terminal and a first and a second stationary contact respectively connected to said first and second input terminals, said movable contact being connected to said first stationary contact when said relay is de-energized and to said second stationary contact when said relay is energized, a second rectifier connected between said second load terminal and said second input terminal for coupling the direct current input voltage to said load terminals when the relay is de-energized, and for decoupli-ng the input voltage from the load terminals when said input terminals have said first relative polarity, and a third rectifier connected between said second load terminal and said first input terminal for coupling the voltage of said input terminals to said load terminals when said relay is energized and for decoupling the input voltage from said load terminals when the voltage across said input terminals has said opposite polarity.

2. A direct current polarity control circuit having a connector with a first and a second input terminal which can be randomly removably connected in either of two ways to a mating connector coupled to a source of dir ect current voltage, so that said input terminals may have either one of two relative polarities, and a first and a second load terminal across which a direct current voltage is to be applied having a consistent relative polarity, said circuit comprising: a relay and a first rectifier connected in series across said input terminals for effecting the energizing for said relay when said input terminals have a first relative polarity and the de-energizing of said relay when said terminals have the opposite polarity, said relay having a movable contact connected to said first load terminal and a first and a second stationary contact respectively connected to said first and second input terminals, said movable contact being connected to said first stationary contact when said relay is de-energized and to said second stationary contact whenv said relay is energized, a second rectifier connected between said second load terminal and said second input terminal for coupling the direct current input voltage to said load terminals when the relay is de-energized, for decoupling the input voltage from the load terminals from said load terminals when said input terminals have said first relative polarity, and a third rectifier connected between said second load terminal and said first input terminal for coupling the voltage of said input terminals to said load terminals when said relay is energized and for decoupling the input voltage from said load terminals when the voltage across said input terminals has said opposite polarity.

No references cited.

ORIS L. RADER, Primary Examiner. W. SHOOP, Assistant Examiner.

Claims (1)

1. A DIRECT CURRENT POLARITY CONTROL CIRCUIT CONNECTED BETWEEN A FIRST AND A SECOND DIRECT CURRENT INPUT TERMINAL ACROSS WHICH A DIRECT CURRENT VOLTAGE SOURCE IS TO BE CONNECTED IN A RANDOM FASHION, SO THAT THE INPUT TERMINALS MAY BE EITHER ONE OF TWO RELATIVE POLARITIES, AND A FIRST AND A SECOND LOAD TERMINAL ACROSS WHICH A DIRECT CURRENT VOLTAGE IS TO BE APPLIED HAVING A CONSISTENT RELATIVE POLARITY, SAID CIRCUIT COMPRISING: A RELAY AND A FIRST RECTIFIER CONNECTED IN SERIES ACROSS SAID INPUT TERMINALS FOR EFFECTING THE ENERGIZING FOR SAID RELAY WHEN SAID INPUT TERMINALS HAVE A FIRST RELATIVE POLARITY AND THE DE-ENERGIZING OF SAID RELAY WHEN SAID TERMINALS HAVE THE OPPOSITE POLARITY, SAID RELAY HAVING A MOVABLE CONTACT CONNECTED TO SAID FIRST LOAD TERMINAL AND A FIRST AND SECOND STATIONARY CONTACT RESPECTIVELY CONNECTED TO SAID FIRST AND SECOND INPUT TERMINALS, SAID MOVABLE CONTACT BEING CONNECTED TO SAID FIRST STATIONARY CONTACT WHEN SAID RELAY IS DE-ENERGIZED AND TO SAID SECOND STATIONARY CONTACT WHEN SAID RELAY IS ENERGIZED, A SECOND RECTIFIER CONNECTED BETWEEN SAID SECOND LOAD TERMINAL AND SAID SECOND INPUT TERMINAL FOR COUPLING THE DIRECT CURRENT INPUT VOLTAGE TO SAID LOAD TERMINALS WHEN THE RELAY IS DE-ENERGIZED, AND FOR DECOUPLING THE INPUT VOLTAGE FROM THE LOAD TERMINALS WHEN SAID INPUT TERMINALS HAVE SAID FIRST RELATIVE POLARITY, AND A THIRD RECTIFIER CONNECTED BETWEEN SAID SECOND LOAD TERMINAL AND SAID FIRST INPUT TERMINAL FOR COUPLING THE VOLTAGE OF SAID INPUT TERMINALS TO SAID LOAD TERMINALS WHEN SAID RELAY IS ENERGIZIED AND FOR DECOUPLING THE INPUT VOLTAGE FROM SAID LOAD TERMINALS WHEN THE VOLTAGE ACROSS SAID INPUT TERMINALS HAS SAID OPPOSITE POLARITY.

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