Disclosed are various embodiments of voltage protectors that include a first voltage clamping device configured to clamp a voltage of an input power applied to an electrical load, and a second voltage clamping device configured to clamp the voltage applied to the electrical load. A series inductance separates the first and second voltage clamping devices. Also, a switching element is employed to selectively establish a direct coupling of the input power to the electrical load, where a circuit is employed to control the operation of the switching element.

Voltage surge and overvoltage protection

A circuit card is disclosed of the type for connection to a system by means of connector pins on the card. The circuit card includes a soft power switch for reducing the power transient effects of inserting the card by gradually coupling the circuit load on the card to the system power supply voltage. Connector pins of various extensions are used to initiate events in the coupling of the circuit load to the power supply voltage. The card further includes logic which causes the circuit load to be gradually decoupled from the power supply upon removal of the card from the system.

Circuit card with soft power switch

A battery-powered DC to DC converter is adjustable in response to the condition of the battery so that an optimum compromise is made between the performance of the battery and the performance of the converter in an application such as charging an electronic strobe flash unit capacitor. The converter includes a transformer (12) having primary (14) and secondary (16) windings, and a switch (18) in series with the primary winding and the battery, for interrupting battery current through the primary winding, to cause current to flow through the secondary winding. A voltage-sensing circuit (30), coupled to the battery, senses the battery open-circuit voltage and the battery load voltage. When the battery load voltage decreases below a predetermined percentage of the battery open-circuit voltage, a control circuit (32) coupled to the voltage-sensing circuit and the switch (18), causes the switch (18) to interrupt current flow in the primary winding (14). The energy drawn from the battery is varied in direct proportion to the battery open-circuit voltage and in inverse proportion to the battery internal resistance so that the load that the converter places on the battery is functionally related to battery condition.

A dc to dc converter adjustable dynamically to battery condition

A current limiting circuit for limiting current surges caused by device turn-on and by input line voltage surges. The circuit has a current sensor for sensing current surges and causing the current to be routed through a current limiting device, such as a resistor. The current sensing circuit senses both over current and normal current conditions and resets the current limiting switch as appropriate. The use of a current sensor as opposed to a sensor for turn-on conditions or voltage levels provides actual control of the current thereby protecting the electrical device during the first application of power and from AC line voltage surges.

Current limiting device

Current inrush limiting apparatus is disclosed including a power supply circuit (32) which regulates the transmission of power from a source (12) to a load (14). A soft start control (36) controls the power supply to prevent excessive current inrush to the load by causing it to apply power to the load gradually when the power first comes on. A dropout timer (38) monitors the power signal and rapidly resets the soft start control circuit if a power dropout exceeds a predetermined minimum duration. This ensures that excessive current inrush also does not occur following brief power dropouts.

Current inrush limiting apparatus

A converter circuit includes an inrush current limit circuit to limit the initial transient surge of inrush current to a power supply upon the initial application of voltage to the power supply input. After the initial start-up transient inrush current surge, the inrush current limit circuit is switched out of the input signal path to reduce power dissipation during normal steady state operation of the circuit. If the input voltage magnitude decreases significantly at any time, the inrush current limit circuit is reset to limit any further current surges.

Inrush current limit circuit with reset response to lowered input voltage

The duty cycle of the switching transistor in a DC to DC converter is controlled by an astable multivibrator whose alternate switching states are respectively responsive to the line and load voltages. Feedback of the output voltage to control the duration of one state of the multivibrator is obtained from the primary of the converter output transformer whose magnetic energy level is not allowed to fully dissipate in any one operating cycle. A balancing circuit arrangement is utilized to minimize variations in the base drive signal of the switching transistor and to prevent it from saturating to eliminate variations in the duration of the conducting state of the transistor due to charge storage.

Dc to dc converter including switching device having its on and off times independently controlled by the line and load voltages, respectively

A blocking oscillator includes a pulse width control circuit which diverts base current from the base drive of the blocking oscillator transistor. This permits the blocking oscillator transistor to turn off and establish a predetermined pulse width independently of its β characteristic and the supply voltage energizing the blocking oscillator.

Roman Ostapiak

Papers

Inrush current limit circuit with reset response to lowered input voltage

Dc to dc converter including switching device having its on and off times independently controlled by the line and load voltages, respectively

Pulse width stabilized blocking oscillator