D. c. flasher

Claim 2

A D.C. Flasher circuit for connection in series into a series connected circuit path of electrical conduction including a load and a source of D.C. potential to cause alternate opening and closing of the circuiT path; the flasher circuit having first and second connectors for connecting the flasher in series connection only into said circuit path of electrical conduction, said connectors defining the only means for electrical connection of said flasher circuit into said circuit path of electrical conduction, output transistor means having a current conduction path connected in series between the connectors, means connected with the output transistor means for controlling the output transistor means to cause conduction and nonconduction of the output transistor means, timing circuit means connected with the controlling means for timing the rate of conduction and nonconduction of the output transistor means, circuit voltage supply means for deriving a stabilized voltage from voltage present across the connectors when the output transistor means is nonconductive, and means connected with the voltage supply means for establishing a substantially stable voltage of a predetermined value between circuit points in the flasher circuit to provide transistor operating potentials independent of ground, whereby the flasher circuit is operable upon connection between two ungrounded points in the path of electrical conduction to the exclusion of any other electrical connection.

Claim 3

The flasher circuit according to claim 1 wherein the means for stabilizing is a diode-capacitor combination having a capacitor connected to establish a voltage across the circuit and a diode connected to supply the capacitor from one of said connectors and to block capacitor discharge by conduction of the output transistor means.

Claim 4

The flasher circuit according to claim 2 wherein said means for establishing a substantially stable voltage of a predetermined value includes at least one voltage establishing semiconductor means for fixing a transistor bias reference voltage.

Claim 5

The flasher circuit according to claim 3 wherein the timing circuit means is a transistor multivibrator and a transistor current amplifier supplying the multivibrator, the voltage establishing semiconductor means is a Zener diode connected to and establishing base drive for the transistor current amplifier.

Claim 6

The flasher circuit according to claim 1 further including means for detecting an overcurrent when the output transistor means conducts, and means responsive to the overcurrent detecting means for reducing the conduction of the output transistor means.

Claim 7

The flasher circuit according to claim 5 further including means for detecting a voltage increase across the conducting output transistor means when the current through the output transistor means is reduced by the conduction reducing means, and means connected with said means for detecting a voltage increase for halting conduction by the output transistor means.

Claim 8

A D.C. flasher circuit for connection to a circuit including a D.C. potential source and a load; the flasher circuit having an output transistor means alternately for conducting and blocking load current between two connectors, means connected with the output transistor means for controlling the output transistor means to cause conduction and nonconduction of the output transistor means, overcurrent sensing means for sensing the current during the conducting periods, first control means connected with the overcurrent sensing means to alter a bias applied to the output transistor means to reduce conduction of the output transistor means in response to overcurrents, means for detecting a voltage increase across the conducting output transistor means when the current through the output transistor means is reduced by the first control means, and a second control means connected with the increased voltage detecting means to stop conduction by the output transistor means in response to detected voltage increase.

Claim 9

A D.C. flasher circuit for connection to a circuit including a D.C. potential source and a load; the flasher circuit having an output transistor means alternately for conducting and blocking load current between two connectors, means connected with the output transistor means for controlling the output transistor means to cause conduction and nonconduction of the output transistor means, overcurrent sensing means for sensing the current during the conducting periods, first control means connected with the overcurrent sensing means to alter a bias applied to the output transistor means to reduce conduction of the output transistor means in response to overcurrents, means for detecting a voltage increase across the conducting output transistor means when the current through the output transistor means is reduced by the first control means, and a second control means connected with the increased voltage detecting means to stop conduction by the output transistor means in response to detected voltage increase.

Claim 10

The flasher circuit according to claim 7 wherein the overcurrent sensing means is a very low resistance resistor, and the conduction reducing first control means is a current control transistor circuit haviNg voltage sensitive bias connections connected across the sensing resistor for reducing a bias to the output transistor means in response to an increase in the voltage across the sensing resistor.

Claim 11

The flasher circuit according to claim 8 wherein the overcurrent sensing means comprises means for establishing a substantially stable voltage including a Zener diode connected with a circuit path across the flasher circuit, and one of said voltage sensitive bias connections is a control transistor base driven connection connected into a circuit path extending from one terminal of the Zener diode to an end of the sensing resistor.

Claim 12

The flasher circuit according to claim 7 wherein the increased voltage detecting means includes a voltage sampling Zener diode and a turn off control transistor, the Zener diode being connected in a circuit branch extending across the flasher circuit, the Zener diode being ordinarily biased to below its rated voltage, whereby increased voltage across the flasher circuit raises the voltage across the Zener diode, the control transistor having its base drive connected with the circuit path of the Zener diode to conduct and turn off the output transistor means after the rated Zener diode voltage is established.

Claim 13

The flasher circuit according to claim 10 further including a capacitor connected between said circuit branch including the Zener diode and a further point of connection in the flasher circuit, the capacitor initially diverting current to prevent immediate biasing into conduction of the turn off control transistor, thereby providing a slight time delay permitting initial overcurrents and voltage increases to diminish before the output transistor means is turned off.

Claim 14

The flasher circuit according to claim 8 whereby the first control means comprises a first control transistor connected with at least one further control transistor, the further control transistor being connected to control the conduction of the output transistor means, one of the first and further control transistors being an NPN transistor and the remaining of the two control transistors being a PNP transistor to reduce temperature dependence of the combined transistor characteristics.

Claim 15

A D.C. lamp flasher of the type including at least one output transistor for connection with an incandescent lamp circuit having a D.C. potential source and at least one lamp, and for alternately conducting and blocking conduction of current to the lamp; the lamp flasher including current sensitive and voltage sensitive protective means, the flasher including at least one output transistor connected alternately to conduct and to block current from one connector to another, means connected with the output transistor for controlling the output transistor to cause the conduction and nonconduction of the output transistor, a sensing resistor in series with the output transistor for providing a voltage drop indicative of the current through the output transistor, a first current control transistor connected with the sensing resistor and changing conductance in response to changes in the voltage across the sensing resistor, additional control transistor means connected with the first current control transistor and operatively connected with the output transistor to reduce base drive to the output transistor and to oppose increased conduction thereby when the current sensing resistor voltage increases, means for sampling the voltage across the output transistor to detect increased voltage thereacross resulting from decreased conduction in the output transistor, a turn off control transistor biased by the voltage sampling means and connected with said additional control transistor means to turn off the output transistor, and means for imparting a short time delay to the bias applied to the turn off control transistor to delay the turn off sufficiently to allow transient and incandescent lamp start up currents to be controlled by the current sensitive proteCtive means of the circuit.

Claim 16

A D.C. lamp flasher of the type including at least one output transistor for connection with an incandescent lamp circuit having a D.C. potential source and at least one lamp, and for alternately conducting and blocking conduction of current to the lamp; the lamp flasher including current sensitive and voltage sensitive protective means, the flasher including at least one output transistor connected alternately to conduct and to block current from one connector to another, means connected with the output transistor for controlling the output transistor to cause the conduction and nonconduction of the output transistor, a sensing resistor in series with the output transistor for providing a voltage drop indicative of the current through the output transistor, a first current control transistor connected with the sensing resistor and changing conductance in response to changes in the voltage across the sensing resistor, additional control transistor means connected with the first current control transistor and operatively connected with the output transistor to reduce base drive to the output transistor and to oppose increased conduction thereby when the current sensing resistor voltage increases, means for sampling the voltage across the output transistor to detect increased voltage thereacross resulting from decreased conduction in the output transistor, a turn off control transistor biased by the voltage sampling means and connected with said additional control transistor means to turn off the output transistor, and means for imparting a short time delay to the bias applied to the turn off control transistor to delay the turn off sufficiently to allow transient and incandescent lamp start up currents to be controlled by the current sensitive proteCtive means of the circuit.