Abstract: Techniques are disclosed to sense a current in a circuit. For instance, current sense circuit according to the teachings of the present invention includes a current sense resistor coupled to an input of the current sense circuit. The current sense resistor is coupled to receive a current to be sensed from the input of the current sense circuit. The current to be sensed is converted to a current sense voltage. A first PN junction diode is coupled to the current sense resistor. A light emitting diode (LED) is coupled to the first PN junction diode to provide a current sense threshold substantially proportional to a difference between a forward voltage drop of the LED and a forward voltage drop of the first PN junction diode. The first PN junction diode is coupled to be biased from the forward voltage drop of the LED. The LED is coupled to the current sense resistor to generate an output when the current sense voltage from the current sense resistor reaches the current sense threshold.

Abstract: A transformer having input and output windings. A sample transformer includes an input winding wound around a core. The input winding has a first end and a second end. An output winding is also wound around the core. The output winding has a first end and a second end. The input winding is capacitively coupled to the output winding to provide a transfer of energy from the input winding to the output winding. A balancing winding is also wound around the core. The balancing winding has a first end and a second end. The first end of the balancing winding is electrically coupled to the first end of the input winding. The second end of the balancing winding is uncoupled such that a dot polarity of the balancing winding is to oppose an electrostatic field to be generated by the input winding relative to the output winding.

Abstract: An energy transfer element having an energy transfer element input winding, an energy transfer element output winding and energy transfer element windings that reduce displacement currents. In one aspect, an energy transfer elements includes an energy transfer element core with first and second windings wound around the energy transfer element core. The first winding is capacitively coupled to the second winding. A third winding is wound around the energy transfer element core to generate a third winding electrostatic field to substantially cancel relative electrostatic fields generated by the first and second windings relative to the energy transfer element core to substantially reduce a capacitive displacement current between the first and second windings. Fourth and fifth windings are wound around the energy transfer element core between the first and second windings to substantially reduce the capacitive displacement current between the first and second windings.

Abstract: Various techniques directed to the digital control of a switching regulator are disclosed. In one aspect, a power supply regulator includes a compare circuit to be coupled to receive a feedback signal representative of an output level of a power supply. This causes a feedback state signal to be generated having a first feedback state that represents an output level of the power supply that is above a threshold level and a second feedback state that represents an output level of the power supply that is below the threshold level. An adjustment circuit is coupled to the compare circuit to adjust the feedback state signal in response to at least one of adjusting the threshold level or adjusting the feedback signal. The adjustment to the feedback state signal tends to cause the feedback state signal to revert from a state at the time of adjustment to a state immediately preceding the adjustment.

Abstract: Techniques are disclosed to control a power converter with multiple output voltages. One example regulated power converter includes a an energy transfer element coupled between a power converter input and first and second power converter outputs. A switch is coupled between the power converter input and the energy transfer element such that switching of the switch causes a first output voltage to be generated at the first power converter output and a second output voltage to be generated at the second power converter output. A current in the energy transfer element is coupled to increase when a voltage across the energy transfer element is a difference between an input voltage at the power converter input and the first output voltage. The current in the energy transfer element is coupled to decrease when the voltage across the energy transfer element is a sum of the first and second output voltages.

Abstract: A technique for extending the operating range of a flyforward converter to low input voltages. In one aspect, power converter includes a positive input supply rail and a negative input supply rail. A power converter input voltage is to be applied between the positive and negative input supply rails. A flyback energy transfer element having a flyback input winding and a forward energy transfer element having a forward input winding are also included. The flyback and forward input windings are coupled between the positive and negative input supply rails. Voltage control circuitry coupled to the forward energy transfer element is also included to reduce a voltage across the forward input winding, substantially to zero, when the power converter input voltage falls below a first threshold value.

Abstract: Methods and apparatuses to sense current and voltage in circuits with voltage drop. In one aspect of the invention, a circuit includes a transistor coupled to a voltage reference. A light emitting diode (LED) is coupled to be driven by the transistor in response to a voltage across an output of the circuit. A first diode is coupled to the LED. A first resistor coupled to the first diode and the LED. The LED is coupled to be driven in response to a voltage drop across the first diode and the first resistor to sense a first current directed through the first diode and the first resistor.

Abstract: An energy transfer element having windings. In one aspect, the energy transfer element includes a first winding wound around a core, the first winding has a first end and a second end. A second winding is wound around the core. The second winding has a first end and a second end. The first winding is capacitively coupled to the second winding to provide a transfer of energy from the first winding to the second winding. A third winding is wound around the core. The third winding has a first end and a second end. The first end of the third winding is electrically coupled to the first end of the second winding. The second end of the third winding is uncoupled such that an influence of an electrostatic field to be produced by the first and second windings relative to the core are to be cancelled by an electrostatic field to be created by the third winding.

Abstract: Various techniques directed to the digital control of a switching regulator are disclosed. In one aspect, a method for regulating an output level at a power converter output includes receiving a feedback signal representative of the output level at the power converter output. In response to a state of the power converter, at least one of the feedback signal or a threshold level is adjusted. A feedback state signal is generated having a first feedback state that represents that the output level is above the threshold level and a second feedback state that represents that the output level is below the threshold level. A duty cycle signal that cycles is generated. In response to a control signal, energy from a power converter input is enabled or disabled to flow to the power converter output. The control signal is responsive to the duty cycle signal and to a change between the first and second feedback states. The control signal is also responsive to a change between the first and second feedback states.

Abstract: A circuit that provides a method and apparatus to actively balance capacitor leakage current from series stacked capacitors and disconnects itself when stacked capacitors are configured for doubler operation. In one embodiment, the active circuit includes high voltage low current transistors, such as for example a PNP bipolar transistor and an NPN bipolar transistor, that are configured in a sink-source voltage follower arrangement with the bases of the transistors connected to a voltage divider network and referenced to a fraction of a DC input voltage with a very high impedance, low dissipative resistor divider network. In one embodiment, the emitters of the PNP and NPN transistors are both tied to the connection point between capacitors in the stack and provide an active sink-source drive, which maintains the voltage at this point to be bounded by the input reference voltages of sink-source followers.

Abstract: Techniques are disclosed to sense a current in a circuit. For instance, current sense circuit according to the teachings of the present invention includes a current sense resistor coupled to an input of the current sense circuit. The current sense resistor is coupled to receive a current to be sensed from the input of the current sense circuit. The current to be sensed is converted to a current sense voltage. A first PN junction diode is coupled to the current sense resistor. A light emitting diode (LED) is coupled to the first PN junction diode to provide a current sense threshold substantially proportional to a difference between a forward voltage drop of the LED and a forward voltage drop of the first PN junction diode. The first PN junction diode is coupled to be biased from the forward voltage drop of the LED. The LED is coupled to the current sense resistor to generate an output when the current sense voltage from the current sense resistor reaches the current sense threshold.

Abstract: A technique for extending the operating range of a flyforward converter to low input voltages. In one aspect, power converter includes a positive input supply rail and a negative input supply rail. A power converter input voltage is to be applied between the positive and negative input supply rails. A flyback energy transfer element having a first input winding and a forward energy transfer element having a forward input winding are also included. The flyback and forward input windings are coupled between the positive and negative input supply rails. Voltage control circuitry coupled to the forward energy transfer element is also included to reduce a voltage across the forward input winding, substantially to zero, when the power converter input voltage falls below a first threshold value.

Abstract: A reduced cost voltage regulation circuit for switched mode power supplies. In one example, a current sense circuit includes a current sense terminal of a voltage regulation circuit. A voltage difference between the current sense terminal and a voltage reference terminal of the voltage regulation circuit is substantially fixed when a first current to be sensed by the current sense circuit at the current sense terminal is substantially equal to a first current sense threshold. A power transistor is also included and is coupled to the current sense circuit and coupled between a power supply input terminal of the voltage regulation circuit and a power supply output terminal of the voltage regulation circuit. The power transistor is coupled to be switched in response to the first current to be sensed by the current sense circuit at the current sense terminal to control a transfer of energy from the input of the power supply to the output of the power supply to regulate an output voltage of the power supply.

Abstract: Methods and apparatuses to sense current and voltage in circuits with voltage drop. In one aspect of the invention, a sense circuit includes a first diode, a first resistor and a light emitting diode (LED). The first resistor is coupled to the first diode. The first current is to be directed through the first diode and the first resistor. A first voltage being the sum of the voltages is developed across the first resistor and the first diode. The LED is coupled to the first diode and the first resistor such that the first voltage is to be applied across the LED to sense the first current. The first current is separate from a current flowing through the LED.

Abstract: A method of transferring energy is disclosed. In one aspect, a method includes transferring energy from a first winding wound around a transformer core to a second winding wound around the transformer core. The first and second windings capacitively coupled to electrical earth. The method further includes generating a third winding electrostatic field with a third winding wound around the transformer core and coupled to the first winding. A fourth winding electrostatic field is generated with a fourth winding wound around the transformer core and coupled to the second winding. The method also includes substantially reducing a capacitive displacement current between the first and second windings with the third and fourth electrostatic fields.

Abstract: A circuit that provides a method and apparatus to actively balance capacitor leakage current from series stacked capacitors and disconnects itself when stacked capacitors are configured for doubler operation. In one embodiment, the active circuit includes high voltage low current transistors, such as for example a PNP bipolar transistor and an NPN bipolar transistor, that are configured in a sink-source voltage follower arrangement with the bases of the transistors connected to a voltage divider network and referenced to a fraction of a DC input voltage with a very high impedance, low dissipative resistor divider network. In one embodiment, the emitters of the PNP and NPN transistors are both tied to the connection point between capacitors in the stack and provide an active sink-source drive, which maintains the voltage at this point to be bounded by the input reference voltages of sink-source followers.

Abstract: Techniques to compensate for parameter variations in a feedback circuit are disclosed. In one embodiment, a regulator circuit includes an energy source coupled to output a generated current in response to a control current. A feedback resistor is coupled to an output of the regulator circuit. The feedback resistor is coupled to conduct a feedback current responsive to the output of the regulator circuit. A current amplifier is coupled to the feedback resistor to generate the control current in response to the feedback current. A compensation network is coupled to the current amplifier to adjust the control current in response to an extrinsic parameter of the regulator circuit. The compensation network includes a transistor and first, second and third resistors. The first resistor is coupled between the feedback resistor and a collector of the transistor. The second resistor coupled between the collector and the base of the transistor.

Abstract: An energy transfer element having an energy transfer element input winding and an energy transfer element output winding. In one aspect, the energy transfer element input winding is capacitively coupled to the energy transfer element output winding. The energy transfer element is capacitively coupled to electrical earth. One or more additional windings are introduced as part of the energy transfer element The one or more additional windings substantially reduce capacitive displacement current between the energy transfer element input winding and energy transfer element output winding by balancing the relative electrostatic fields generated between these windings and/or between the energy transfer element and electrical earth by canceling the electrostatic fields generated by all windings within the energy transfer element relative to electrical earth through the selection of the physical position and number of turns in the additional windings.

Abstract: Dissipative clamping apparatuses and methods for electrical circuits. In one aspect of the invention, In one aspect of the invention, a method includes switching a power supply input on an energy transfer element, regulating a power supply output by switching the power supply input on the energy transfer element, clamping a voltage on the energy transfer element to a clamp voltage and varying the clamp voltage in response to the power supply input. In another aspect, an electrical circuit includes a dissipative clamp circuit coupled to an input of the electrical circuit. An inductive element is coupled between the dissipative clamp circuit and an output of the electrical circuit. A switch is coupled in series with the inductive element.

Abstract: A technique for extending the operating range of a flyforward converter to low input voltages. In one aspect, power converter includes a positive input supply rail and a negative input supply rail. A power converter input voltage is to be applied between the positive and negative input supply rails. A flyback energy transfer element having a flyback input winding and a forward energy transfer element having a forward input winding are also included. The flyback and forward input windings are coupled between the positive and negative input supply rails. Voltage control circuitry coupled to the forward energy transfer element is also included to reduce a voltage across the forward input winding, substantially to zero, when the power converter input voltage falls below a first threshold value.