Abstract: A power converter controller includes a control loop clock generator to generate a switching frequency signal responsive to a burst load threshold, a power signal, and a load signal. A switching frequency of the switching frequency signal is above a mechanical audio resonance range of an energy transfer element and above an audible noise frequency. A burst control circuit generates a burst on signal and a burst off signal in response to a feedback signal and a burst enable signal to operate the controller in a plurality of burst modes. A burst frequency of the burst on signal or the burst off signal is less than the mechanical audio resonance range. A request transmitter circuit generates a request signal responsive to the switching frequency signal, the burst on signal, and the burst off signal to control switching of a switching circuit.

Abstract: A controller for use in a power converter that is configured to operate in a plurality of modes including a first mode and a second mode includes a frequency monitor module coupled to measure a signal characteristic of a switch drive signal coupled to control switching of a switches block of the power converter. The frequency monitor module includes a memory coupled to store a measured signal characteristic of the switch drive signal measured during the first mode. The frequency monitor module is coupled to generate a clock signal in response to the measured signal characteristic stored in the memory. The switch drive signal is coupled to be generated in response to the clock signal during the second mode.

Abstract: A controller configured for use in a power converter includes a multiplexer that receives a startup clock signal and a request clock signal. The multiplexer selects the startup signal or the request clock signal to generate a clock signal. A startup clock generates the startup clock signal to control a switching frequency of a primary switching circuit during a startup condition. A request clock generates the request clock signal in response to a request signal to control the switching frequency of the primary switching circuit after the startup condition. A control circuit receives the clock signal to generate a drive signal control the switching frequency of the primary switching circuit. The control circuit selects the startup clock signal during the startup condition. The control circuit receives an indication in the request signal of an end of an undervoltage condition and then selects the request clock signal after the startup condition.

Abstract: A controller for use in a power converter includes a control loop clock generator that is coupled to generate a switching frequency signal in response to a sense signal representative of a characteristic of the power converter, a load signal responsive to an output load of the power converter, and a hard switch sense output. A hard switch sense circuit is coupled to generate the hard switch sense output in response to the switching frequency signal and a rectifier conduction signal that is representative of a polarity of an energy transfer element of the power converter. A request transmitter circuit is coupled to generate a request signal in response to the switching frequency signal to control switching of a switching circuit coupled to an input of the energy transfer element of the power converter.

Abstract: A controller for use in a power converter includes a power switch including a drain, a source, a control input, and a tap. The power switch includes a first transistor coupled to a second transistor, a drain of the first transistor is coupled to the drain of the power switch and the source of the first transistor is coupled to the tap. A tap sense circuit is coupled to the tap. A drive circuit is coupled to receive an indicator signal from the tap sense circuit. The indicator signal is indicative of a voltage at the tap or the current through the first transistor. The drive circuit is coupled to receive a feedback signal representative of an output quantity of the power converter. The drive circuit is coupled to generate a drive signal to control switching of the power switch in response to the indicator signal and the feedback signal.

Abstract: A power converter includes a front end stage having a power factor correction controller, an output stage with a DC/DC controller, and light load detection circuitry coupled to detect relatively low power consumption by a load on an output of the output stage. In response to the detection, the power factor correction controller in the front end stage is turned off.

Abstract: A controller for use in a power converter includes logic circuits to turn on and off a switch to regulate an output quantity. A first integrating capacitor is charged with a combination of a first current and a second current while the switch is turned on. The first current is proportional to a reset voltage and the second current is proportional to an input voltage. A reference generation circuit including a second integrating capacitor is charged with the first current during a previous switching cycle of the switch. The reference generation circuit generates a reference voltage in response to the second integrating capacitor. A comparator provides a stop signal to the logic circuits to turn off the switch in response to a comparison of a voltage across the first integrating capacitor with the reference voltage.

Abstract: A power converter includes a front end stage having a power factor correction controller, an output stage with a DC/DC controller, and light load detection circuitry coupled to detect relatively low power consumption by a load on an output of the output stage. In response to the detection, the power factor correction controller in the front end stage is turned off.

Abstract: An example power supply includes a first power converter, a second power converter, and a shared clamp reset circuit. The first power converter is adapted to convert an input to a first voltage output and includes a first diode and a first transformer having a first primary winding. The second power converter is adapted to convert the input to a second voltage output and includes a second diode and a second transformer having a second primary winding. The shared clamp reset circuit is included in the first power converter and is coupled to the cathode of the first diode. The shared clamp reset circuit also includes a clamp connection that is coupled to the cathode of the second diode. The shared clamp reset circuit is adapted to manage leakage inductance energy within the first transformer and within the second transformer.

Abstract: A controller for use in a power converter includes logic circuits to turn on and off a switch to regulate an output quantity. A first integrating capacitor is charged with a combination of a first current and a second current while the switch is turned on. The first current is proportional to a reset voltage and the second current is proportional to an input voltage. A reference generation circuit including a second integrating capacitor is charged with the first current during a previous switching cycle of the switch. The reference generation circuit generates a reference voltage in response to the second integrating capacitor. A comparator provides a stop signal to the logic circuits to turn off the switch in response to a comparison of a voltage across the first integrating capacitor with the reference voltage.

Abstract: A power supply control circuit includes a threshold detection circuit coupled to a first terminal to measure a signal at the first terminal during a duration of an initialization period after a fourth terminal has been charged to a supply threshold value. A regulator circuit is coupled between a second terminal and the fourth terminal to charge the fourth terminal to the supply threshold value during the initialization period of the power supply control circuit. A selection circuit is coupled to the threshold detection circuit to select a parameter/mode in response to the signal measured at the first terminal. The first terminal is further coupled to receive one or more additional signals during normal operation at times other than the initialization period to provide at least one additional function for the power supply control circuit after the initialization period is complete.

Abstract: A switching circuit for use in a power converter includes a first active switch coupled between a first terminal of an input of the power converter and a first terminal of a primary winding of a transformer. A second active switch is coupled between a second terminal of the input and a second terminal of the primary winding. An output capacitance of the first active switch is greater than an output capacitance of the second active switch. A first passive switch is coupled between the second terminal of the primary winding and the first terminal of the input. A second passive switch is coupled between the second terminal of the input and the first terminal of the primary winding. A reverse recovery time of the first passive switch is greater than a reverse recovery time of the second passive switch.

Abstract: A power supply includes a forward converter having a first transformer coupled to an input of the power supply and to a first voltage output. The power supply also includes a separate flyback converter having a second transformer that is coupled to the input and to a second voltage output. A clamp reset circuit is coupled to the first transformer and to the second transformer. The clamp reset circuit includes a capacitor and a voltage limiting element. The voltage limiting element is coupled to prevent energy received at the capacitor from both the power converters from exceeding a threshold. The voltage limiting element limits a voltage on the capacitor.

Abstract: A saturation prevention circuit includes a first controlled current source, a second controlled current source, an integrating capacitor, and a comparator. The first controlled current source generates a first current that is proportional to an input voltage that is to be applied to a winding of a transformer. The second controlled current source generates a second current that is proportional to a reset voltage that is to be applied to the winding. The capacitor is charged with the first current while the input voltage is applied to the winding of the transformer and discharged with the second current while the reset voltage is applied to the winding. The comparator compares a voltage on the integrating capacitor with a first threshold and generates a first signal to immediately turn off the switch when the voltage on the integrating capacitor reaches the first threshold to limit a magnetic flux in the transformer.

Abstract: A power supply includes an energy transfer element coupled between an input and an output. A switch is coupled to an input of the energy transfer element. A threshold detection circuit includes in an integrated circuit coupled to measure a signal from a resistive external circuit coupled between fourth and first external terminals of the integrated circuit during an initialization period after the fourth external terminal has been charged to a supply threshold value. A regulator circuit is coupled between second and fourth external terminals of the integrated circuit. The regulator circuit is coupled to charge the fourth external terminal to the supply threshold value during the initialization period. A selection circuit is coupled to the threshold detection circuit to select a parameter/mode of the integrated circuit in response to the measured signal.

Abstract: A switching circuit for use in a power supply includes a first active switch coupled to a first terminal of a primary winding of a transformer. A second active switch is coupled to a second terminal of the primary winding of the transformer. An output capacitance of the first active switch is greater than an output capacitance of the second active switch. A first passive switch is coupled to the second active switch and to the second terminal of the primary winding. A second passive switch is coupled to the first active switch and to the first terminal of the primary winding. A reverse recovery time of the first passive switch is greater than a reverse recovery time of the second passive switch. A recovery circuit is coupled to receive a current from the first passive switch.

Abstract: An example power supply includes a first power converter, a second power converter, and a shared clamp reset circuit. The first power converter is adapted to convert an input to a first output and includes a first transformer having a first primary winding. The second power converter is also adapted to convert the input to a second output and includes a second transformer having a second primary winding. The second primary winding of the second transformer is not the first primary winding of the first transformer. The shared clamp reset circuit is coupled to the first primary winding of the first transformer and is coupled to the second primary winding of the second transformer to manage leakage inductance energy within the first transformer and within the second transformer.

Abstract: A power supply includes a first power converter having a first transformer coupled to an input of the power supply and to a first output of the power supply. A clamp reset circuit is coupled to the first transformer. The clamp reset circuit includes a capacitor coupled to the first power converter and a Zener diode coupled to the capacitor. A second power converter is coupled to the clamp reset circuit. The second power converter includes a second transformer coupled to the clamp circuit and to a second output of the power supply. The capacitor is coupled to store energy received from the first power converter and the second power converter. The Zener diode is coupled to prevent the energy received from the first power converter and the second power converter from exceeding a threshold. The Zener diode limits voltage on the capacitor.

Abstract: A saturation prevention circuit includes a first controlled current source, a second controlled current source, an integrating capacitor, and a comparator. The first controlled current source generates a first current that is proportional to an input voltage that is to be applied to a winding of a transformer. The second controlled current source generates a second current that is proportional to a reset voltage that is to be applied to the winding. The capacitor is charged with the first current while the input voltage is applied to the winding of the transformer and discharged with the second current while the reset voltage is applied to the winding. The comparator compares a voltage on the integrating capacitor with a first threshold and generates a first signal to immediately turn off the switch when the voltage on the integrating capacitor reaches the first threshold to limit a magnetic flux in the transformer.

Abstract: A power supply includes an energy transfer element coupled between an input and an output. A switch is coupled to an input of the energy transfer element. A threshold detection circuit includes in an integrated circuit coupled to measure a signal from a resistive external circuit coupled between fourth and first external terminals of the integrated circuit during an initialization period after the fourth external terminal has been charged to a supply threshold value. A regulator circuit is coupled between second and fourth external terminals of the integrated circuit. The regulator circuit is coupled to charge the fourth external terminal to the supply threshold value during the initialization period. A selection circuit is coupled to the threshold detection circuit to select a parameter/mode of the integrated circuit in response to the measured signal.