Abstract: An overcurrent protection apparatus (50) and method for switch-mode power supplies (10) immediately clamps the peak power supply current when a sensed current magnitude exceeds a threshold current magnitude, reduces the threshold current magnitude if the overcurrent condition persists, and automatically attempts a restart of the power supply (10) to normal operation.

Abstract: An overcurrent protection apparatus (50) and method for switch-mode power supplies (10) immediately clamps the peak power supply current when a sensed current magnitude exceeds a threshold current magnitude, reduces the threshold current magnitude if the overcurrent condition persists, and automatically attempts a restart of the power supply (10) to normal operation.

Abstract: A method and circuit for reducing the leading edge spike in a current sense signal. The current sense signal is a measure of the current through a switched power device controlled by a switching regulator controller. The slew rate of the current sense signal is limited to prevent the slew rate from exceeding a predetermined maximum. The limited slew rate signal is provided to the switching regulator controller. A transconductance amplifier may be used to limit the slew rate of the current sense signal. A capacitor at the output of the transconductance amplifier contributes to controlling the maximum slew rate of the amplifier. The capacitor is charged by the current output of the amplifier to provide a voltage signal for use in place of the original current sense signal. A switch may be provided for selecting between the slew rate limited current sense signal and the original current sense signal.

Abstract: A method for making a planar magnetic device is presented. The magnetic device has generally spirally-directed planar coils supported on plural substrates. The plural substrates are stacked so as to have their respective outer peripheries connected to termination pads which are laterally spaced from the termination pads of other coils, as viewed in a direction perpendicular to the planar coils. The inner termini of at least two of the coils may be interconnected by a plated via to constitute a single winding on plural planes. An exposed portion of the termination pads resides alongside vertical edges of the magnetic device and is electrically connected to a vertical plating which form pin-less terminations of the magnetic device. The magnetic device may include a beveled portion for orientation of the device in a circuit. A method of manufacturing the magnetic device is also disclosed.

Abstract: A programmable delay circuit employs a comparator to control an output driver. The comparator compares a ramp signal to an error control signal derived from an error amplifier or in the alternative to a disable signal. The output of the comparator is latched on until a reset signal is received. The reset signal is produced when the ramp signal is discharged below a predetermined level. The programmable delay circuit is useful in a secondary side post regulator to control a totem pole driver. The totem pole driver in turn controls a switching device coupled to a voltage on a secondary winding.

Abstract: A programmable delay circuit employs a comparator to control an output driver. The comparator compares a ramp signal with a disable signal or an error control signal derived from an error amplifier. The comparator latches the output on until a reset signal is received. The reset signal is produced when the ramp signal is discharged below a predetermined level. The programmable delay circuit is useful in a secondary side post regulator to control a grounded totem pole driver. The totem pole driver in turn controls a switching device coupled to a voltage on a secondary winding.

Abstract: A sleep switch connected to a ramp pin, an undervoltage lockout circuit and a hysteretic differential comparator for use in the undervoltage lockout circuit are disclosed. An integrated circuit has a comparator that receives a voltage from the ramp pin which it compares with a control voltage. The sleep switch connected to the ramp pin is activated when the ramp pin is below a predetermined voltage threshold at which point it puts the integrated circuit into a low power consumption sleep mode. The undervoltage lockout circuit includes a detection leg connected between the supply terminal and ground. A current supply is enabled when the voltage across a resistive portion of a detection leg rises above a first threshold. A differential comparator is responsive to the detection voltage for enabling the current supply. The differential comparator may include three transistors arranged to provide first and second detection thresholds so as to establish a hysteresis.

Abstract: A totem pole driver with cross conductive protection and default low impedance state output employs a totem pole output formed by top and bottom output transistors. A first circuit path switches the bottom output transistor on or off in response to a switching signal. A second circuit path, slower than the first circuit path, switches the top output transistor on in response to the switching signal after the bottom output transistor is switched off. A third circuit path switches the top output transistor off in response to a sync signal known to lead the switching signal. An emergency voltage supply is made available to hold the bottom output transistor on and the top output transistor off if the regulated circuit voltage is lost.

Abstract: A switching voltage controller with improved rejection of supply voltage transients, wherein the switching of the voltage controller is controlled by sensing the current through an inductor to provide a current sense signal proportional to the sensed current and comparing the current sense signal voltage to the voltage of a peak signal and the voltage of a valley signal. An error amplifier provides a control signal proportional to the voltage difference between the output voltage of the voltage controller and a reference voltage source. The switching voltage controller provides for improved rejection of transients in the supply voltage by forcing the valley signal to be a first voltage differential .DELTA.' volts below the control signal and the peak signal to be a second voltage differential .DELTA." volts above the control signal, where .DELTA." and .DELTA.' are functions of the supply voltage to the voltage controller such that the rate of change of .DELTA." and .DELTA.

Abstract: A method and circuit for reducing the leading edge spike in a current sense signal. The current sense signal is a measure of the current through a switched power device controlled by a switching regulator controller. The slew rate of the current sense signal is limited to prevent the slew rate from exceeding a predetermined maximum. The limited slew rate signal is provided to the switching regulator controller. A transconductance amplifier may be used to limit the slew rate of the current sense signal. A capacitor at the output of the transconductance amplifier contributes to controlling the maximum slew rate of the amplifier. The capacitor is charged by the current output of the amplifier to provide a voltage signal for use in place of the original current sense signal. A switch may be provided for selecting between the slew rate limited current sense signal and the original current sense signal.