Abstract: A timing circuit of a controller generates a clock signal having a switching period for use by a pulse width modulation (PWM) circuit to control a switch of a power supply. The switching period of the clock signal is based on a charging time plus a discharging time of a capacitor included in the timing circuit. A first current source charges the capacitor while the timing circuit is in a normal charging mode. A second current source charges the capacitor while the timing circuit is in an alternative charging mode that is when the on time of the switch exceeds a threshold time. The current provided by the second current source is less than the current provided by the first current source such that the switching period of the clock signal is increased in response to the timing circuit entering the alternative charging mode.

Abstract: In one aspect, a power supply includes an energy transfer element, a switch, a feedback circuit, a comparator, a state machine, and a control circuit. The feedback circuit generates a feedback signal representative of an output level of the power supply. The comparator provides a feedback state signal having a first feedback state that represents the output level of the power supply being above a threshold level and a second feedback state that represents the output level being below the threshold level. The state machine selectively modulates a first signal in response to the feedback state signal, where the first signal is the feedback signal or the threshold value signal. The control circuit is coupled to control switching of the switch to regulate the output level of the power supply in response to the feedback state signal.

Abstract: A power converter controller includes a drive circuit coupled to control switching of a power switch coupled to an energy transfer element and an input of the power converter. An output voltage sensor including first and second pulse sampler circuits is coupled to capture first and second peak voltages, respectively, that are representative of a second peak of a ringing voltage of a feedback signal representative of an output of the power converter. The first pulse sampler circuit is coupled to capture the first peak voltage at a first time in the feedback signal. The second pulse sampler circuit is coupled to capture the second peak voltage at a second time in the feedback signal. The drive circuit is coupled to receive a change signal from the output voltage sensor in response to the first and second peak voltages.

Abstract: An example power supply regulator includes an energy transfer element, a switch, and a controller. The controller includes a switch signal generator, a modulation circuit, and a multi-cycle modulator circuit. The modulation circuit modulates the period of a modulation switching signal when an equivalent switching frequency is greater than a reference frequency and fixes the switching period when the equivalent switching frequency is less than the reference frequency. The multi-cycle modulator circuit enables the switch signal generator to provide a switch signal uninterrupted if the equivalent switching frequency is greater than the reference frequency and disables the switch signal generator for a first time period and then enables the switch signal generator for a second time period when the equivalent frequency is less than the reference frequency. The multi-cycle modulator circuit varies the first time period to regulate the output.

Abstract: A timing circuit of a controller generates a clock signal having a switching period for use by a pulse width modulation (PWM) circuit to control a switch of a power supply. The switching period of the clock signal is based on a charging time plus a discharging time of a capacitor included in the timing circuit. A first current source charges the capacitor while the timing circuit is in a normal charging mode. A second current source charges the capacitor while the timing circuit is in an alternative charging mode that is when the on time of the switch exceeds a threshold time. The current provided by the second current source is less than the current provided by the first current source such that the switching period of the clock signal is increased in response to the timing circuit entering the alternative charging mode.

Abstract: An example integrated circuit controller for use in a switching power supply includes a pulse width modulation (PWM) circuit and a timing circuit. The PWM circuit controls a switch to regulate an output of the power supply in response to a switch current flowing through the switch and in response to a clock signal having a switching period. The timing circuit provides the clock signal and increases the switching period in response to an on time of the switch exceeding a threshold time.

Abstract: A power converter includes a current controller coupled to an energy transfer element to selectively enable a first, second or third current in the current controller. The first current is substantially zero, the second current is greater than the third current, and the third current is greater than the first current. The third current only partially discharges a capacitance coupled to the energy transfer element and the current controller. A control circuit is to be coupled to the current controller to selectively enable the first, second or third current in the current controller. A first feedback circuit is coupled to generate a first feedback signal while the first current is enabled by the current controller after a full discharge pulse. A second feedback circuit is coupled to generate a second feedback signal while the first current is enabled in the controller after a partial discharge pulse.

Abstract: A power converter includes a power switch, an energy storage element, a driver, a first calculator, and a second calculator. The first calculator coupled to determine an end of an on time of a power switch of the power converter by integrating an input current to output an on time signal representative of the end of the on time of the power switch. The second calculator coupled to determine an end of an off time of the power switch by integrating a difference between an input voltage and an output voltage to output an off time signal representative of the end of the off time of the power switch. The driver controls the power switch such that an input current of the power converter is substantially proportional to an input voltage of the power converter in response to the on time signal and the off time signal.

Abstract: An example method includes controlling a duty ratio of a switch to regulate an output of a forward power converter and storing a first voltage. The first voltage is equal to an input voltage of the forward power converter when the input voltage is at a steady-state value. The method also includes resetting a transformer of the forward power converter when the switch is in an OFF state by setting a voltage across a primary winding of the transformer to the stored first voltage in response to a drop in the input voltage to below the steady-state value. Further included in the method is increasing the duty cycle of the switch to greater than fifty (50) percent in response to the drop in the input voltage to maintain regulation at the output of the forward power converter.

Abstract: An example controller for use in a power supply regulator includes a switch signal generator, a modulation circuit, and a multi-cycle modulator circuit. The modulation circuit modulates the period of a modulation switching signal when an equivalent switching frequency is greater than a reference frequency and fixes the switching period when the equivalent switching frequency is less than the reference frequency. The multi-cycle modulator circuit enables the switch signal generator to provide a switch signal uninterrupted if the equivalent switching frequency is greater than the reference frequency and disables the switch signal generator for a first time period and then enables the switch signal generator for a second time period when the equivalent frequency is less than the reference frequency. The multi-cycle modulator circuit varies the first time period to regulate the output.

Abstract: An example integrated circuit controller includes a pulse width modulation (PWM) circuit and a timing circuit. The PWM circuit controls a switch to regulate an output of a power supply in response to a switch current flowing through the switch and in response to a clock signal having a switching period. The timing circuit provides the clock signal and includes a timing capacitor where the switching period of the clock signal is equal to a charging time that the timing capacitor charges to an upper reference voltage plus a discharging time that the timing capacitor discharges to a lower reference voltage. The timing circuit increases the charging time of the timing capacitor by decreasing a rate at which the timing capacitor is charged to increase the switching period of the clock signal if an on time of the switch is greater than or equal to a threshold time.

Abstract: A reset voltage circuit for a forward power converter includes a reset capacitor and a memory capacitor. The reset capacitor is to be coupled to recycle energy from a primary winding of a transformer to an input bulk capacitor during a resetting of the transformer. The memory capacitor is to be coupled to store a first voltage equal to an input voltage of the power converter when the input voltage is at a steady-state value. The memory capacitor is further to set a voltage across the primary winding during the resetting of the transformer to a magnitude greater than or equal to the first voltage when the input voltage of the forward power converter drops below the steady-state value.

Abstract: Methods and apparatuses are disclosed for sampling a feedback signal representative of an output of a power converter using a pre-biased filter capacitor. The pre-biased filter capacitor provides accurate sampling of the feedback signal during various load conditions. The pre-biased filter may be pre-charged to a pre-bias voltage that is below the regulated voltage of the feedback signal to reduce the amount of time required to charge the pre-biased filter capacitor to the regulated voltage of the feedback signal.

Abstract: An example integrated circuit controller for use in a switching power supply includes a pulse width modulation (PWM) circuit and a timing circuit. The PWM circuit controls a switch to regulate an output of the power supply in response to a switch current flowing through the switch and in response to a clock signal having a switching period. The timing circuit provides the clock signal and increases the switching period in response to an on time of the switch exceeding a threshold time.

Abstract: An example integrated circuit controller includes a pulse width modulation (PWM) circuit and a timing circuit. The PWM circuit controls a switch to regulate an output of a power supply in response to a switch current flowing through the switch and in response to a clock signal having a switching period. The timing circuit provides the clock signal and includes a timing capacitor where the switching period of the clock signal is equal to a charging time that the timing capacitor charges to an upper reference voltage plus a discharging time that the timing capacitor discharges to a lower reference voltage. The timing circuit increases the charging time of the timing capacitor by decreasing a rate at which the timing capacitor is charged to increase the switching period of the clock signal if an on time of the switch is greater than or equal to a threshold time.

Abstract: A controller for use in a power converter includes a control circuit to be coupled to a current controller coupled to an energy transfer element. A first, second or third current is enabled in the current controller in response to the control circuit. The first current is substantially zero, the second current is greater than the third current, and the third current is greater than the first current. The third current only partially discharges a capacitance coupled to a terminal coupled between the energy transfer element and the current controller. A first feedback circuit coupled to the control circuit generates a first feedback signal after a full discharge pulse of current through the current controller. A second feedback circuit coupled to the control circuit generates a second feedback signal after a partial discharge pulse of current through the current controller.

Abstract: An output voltage sensor for use in a power converter controller includes a first pulse sampler circuit coupled to receive a feedback signal representative of an output of a power converter. The first pulse sampler circuit is coupled to capture a first peak voltage representative of a second peak of a ringing voltage of the feedback signal at a first time in the feedback signal. A second pulse sampler circuit is coupled to receive the feedback signal representative of the output of the power converter. The second pulse sampler circuit is coupled to capture a second peak voltage representative of the second peak of the ringing voltage of the feedback signal at a second time in the feedback signal. The output voltage sensor is coupled to output a change signal to a drive circuit of the power converter controller in response to the first and second peak voltages.

Abstract: In one aspect, a power converter includes a power switch, an energy storage element, a driver, a first calculator, and a second calculator. The first calculator coupled to determine an end of an on time of a power switch of the power converter by integrating an input current to output an on time signal representative of the end of the on time of the power switch. The second calculator coupled to determine an end of an off time of the power switch by integrating a difference between an input voltage and an output voltage to output an off time signal representative of the end of the off time of the power switch. The driver controls the power switch such that an input current of the power converter is substantially proportional to an input voltage of the power converter in response to the on time signal and the off time signal.

Abstract: An example controller for use in a power supply regulator includes a switch signal generator, a modulation circuit, and a multi-cycle modulator circuit. The modulation circuit modulates the period of a modulation switching signal when an equivalent switching frequency is greater than a reference frequency and fixes the switching period when the equivalent switching frequency is less than the reference frequency. The multi-cycle modulator circuit enables the switch signal generator to provide a switch signal uninterrupted if the equivalent switching frequency is greater than the reference frequency and disables the switch signal generator for a first time period and then enables the switch signal generator for a second time period when the equivalent frequency is less than the reference frequency. The multi-cycle modulator circuit varies the first time period to regulate the output.

Abstract: In one aspect, a power supply includes an energy transfer element, a switch, a feedback circuit, a comparator, a state machine, and a control circuit. The feedback circuit generates a feedback signal representative of an output level of the power supply. The comparator provides a feedback state signal having a first feedback state that represents the output level of the power supply being above a threshold level and a second feedback state that represents the output level being below the threshold level. The state machine selectively modulates a first signal in response to the feedback state signal, where the first signal is the feedback signal or the threshold value signal. The control circuit is coupled to control switching of the switch to regulate the output level of the power supply in response to the feedback state signal.