Abstract: An LED driver includes at least two interlocked closed feedback loops. One feedback loop controls the duty cycle of the on/off times of a switch connected in series to the LED string, and the other feedback loop controls the duty cycle of the on/off times of a power switch in the switching power converter that provides a DC voltage applied to the LED string. The LED driver of the present invention achieves fast control of the LED brightness and current sharing among multiple LED strings simultaneously in a power-efficient and cost-efficient manner.

Abstract: A controller integrated circuit (IC) for controlling a power converter uses its input voltage pin with a plurality of functions, including receiving an input voltage to the power converter, charging an external startup capacitor through charging circuitry coupled internally to the input voltage pin, and also receiving a test signal for programming a programmable resistance in an input voltage scale down circuitry coupled to the input voltage pin. Use of the input voltage pin with a plurality of functions reduces the number of pins required in the controller IC, thereby reducing the cost of manufacturing the controller IC.

Abstract: A switch controller compensates the total on-time delay of the switch in a switching power converter. The intended on-time of the switching transistor for the present switching cycle is reduced by the time difference between the actual on-time and the intended on-time of the switching transistor in the previous switching cycle in the switching power converter. The total delay of the switch in the switching power converter, including propagation delay, switch turn-on delay, and switch turn-off delay, can be compensated in real time, cycle by cycle.

Abstract: An LED lamp is provided in which the output light intensity of the LEDs in the LED lamp is adjusted based on the input voltage to the LED lamp. A dimmer control unit detects a type of dimmer switch during a configuration process. Using the detected dimmer type, the dimmer control unit generates control signals appropriate for the detected dimmer type to provide regulated current to the LEDs and to achieve the desired dimming effect. The LED lamp can be a direct replacement of conventional incandescent lamps in typical wiring configurations found in residential and commercial building lighting applications that use conventional dimmer switches.

Abstract: In a switching power converter, PWM mode and PFM mode are separated into two independent control sections with the control voltage range in each control section determined independently. Each of the PWM and PFM modulation modes cannot operate continuously beyond its boundaries, thereby forming a control gap between the two control sections within which no continuous operation is allowed. In order to supply a load condition within the control gap, the power supply operates at the two boundaries of the control gap. Transition between PWM and PFM modes occurs fast, with low output voltage ripple. No limitation needs to be imposed on the control voltage range in each of the PWM and PFM control sections, because the control parameters in the PWM and PFM control sections need not be matched to one another, due to separation of the PWM and PFM modes by the control gap.

Abstract: A switching power converter detects low load conditions based on the ratio of a first peak current value for peak current switching in constant voltage regulation mode to a second peak current value for peak current switching in constant current regulation mode. The power supply load is considered to have a low load if the ratio is lower than a predetermined threshold. Once a low load condition is detected, the switching frequency of the switching power converter is reduced to a level that minimizes switching loss in the power converter. In addition, the switching power converter also adjusts the switching frequency according to the sensed input line voltage. An offset is added to the switching period to reduce the switching frequency of the switching power converter, as the input line voltage is increased.

Abstract: A switching power converter comprises a transformer (110), a switch (108) coupled to the transformer (110), and a switch controller (200) coupled to the switch (108) for generating a switch drive signal (207) to turn on or off the switch (108). The drive current of the switch drive signal (207) is adjusted dynamically according to line or load conditions within a switching cycle and/or over a plurality of switching cycles. The magnitude of the drive current can be dynamically adjusted within a switching cycle and/or over a plurality of switching cycles, in addition to the pulse widths or pulse frequencies of the drive current.

Abstract: In a switching power converter, no-load condition is detected based on a variety of parameters including the output current, primary current, transformer reset time, and switching period. Once the no-load condition is detected, the switching power converter enters stand-by mode, in which the reference voltage corresponding to the target regulated output voltage of the switching power converter is lowered to a low stand-by value or the switching power converter is shut down for a predetermined duration. As a result, power loss during the stand-by mode of the switching power converter can be reduced significantly.

Abstract: A switch controller compensates the total on-time delay of the switch in a switching power converter. The intended on-time of the switching transistor for the present switching cycle is reduced by the time difference between the actual on-time and the intended on-time of the switching transistor in the previous switching cycle in the switching power converter. The total delay of the switch in the switching power converter, including propagation delay, switch turn-on delay, and switch turn-off delay, can be compensated in real time, cycle by cycle.

Abstract: Adaptive multi-mode digital control schemes that improve the light-load efficiency (and thus the overall average efficiency) in switch-mode power converters without causing performance issues such as audible noises or excessive voltage ripples. Embodiments include a switch-mode power converter that reduces current in the power converter using a second pulse-width-modulation (PWM) mode before reaching switching frequencies that generate audible noises. As the load across the output of the power converter is reduced, the power converter transitions from a first PWM mode in high load conditions to a first pulse-frequency-modulation (PFM) mode, then to a second PWM mode, and finally to a second PFM mode. During the second PFM mode, the switching frequency is dropped to audible frequency levels. Current in the power converter, however, is reduced in the second PWM mode before transitioning to the second PFM mode.

Abstract: An improved valley-mode switching (VMS) scheme and circuitry for implementing the improved VMS switching scheme in a switch-mode power converter are disclosed. For a given switching cycle, a desired switch turn-on time is determined based on a pulse width modulation, pulse frequency modulation, or other suitable power converter control scheme. Also, one or more times corresponding to local minimums (valleys) are predicted for the voltage across a power switch of the switching power converter. The power switch is turned on at a valley immediately subsequent or otherwise subsequent to the desired switch time determined according to the power converter control scheme. Thus, the improved VMS scheme enables low-voltage switch operation to reduce switching loss and EMI noise without restricting the control scheme of the power converter.

Abstract: A controller of an AC/DC flyback switching power supply uses adaptive digital control approaches to control the switching operation of a BJT power switch based on primary-side feedback to regulate the secondary-side constant output voltage and output current, without using the input line voltage. Switching-cycle by switching-cycle peak current control and limit are achieved based on the sensed primary-side current rather than the input line voltage in both constant-voltage and constant-current modes, operating in PWM, PFM and/or combinations of a plurality of PWM and PFM modes. The controller IC does not need a separate pin and ADC circuitry for sensing the input line voltage.

Abstract: A switch controller compensates the total on-time delay of the switch in a switching power converter. The intended on-time of the switching transistor for the present switching cycle is reduced by the time difference between the actual on-time and the intended on-time of the switching transistor in the previous switching cycle in the switching power converter. The total delay of the switch in the switching power converter, including propagation delay, switch turn-on delay, and switch turn-off delay, can be compensated in real time, cycle by cycle.

Abstract: An LED driver includes at least two interlocked closed feedback loops. One feedback loop controls the duty cycle of the on/off times of a switch connected in series to the LED string, and the other feedback loop controls the duty cycle of the on/off times of a power switch in the switching power converter that provides a DC voltage applied to the LED string. The LED driver of the present invention achieves fast control of the LED brightness and current sharing among multiple LED strings simultaneously in a power-efficient and cost-efficient manner.

Abstract: A power converter includes a switch controller generating a pulse signal controlling a switch to emulate peak current mode control. The switch controller generates a control voltage from a representation of an output voltage of the power converter and a reference voltage. Based on the control voltage and a representation of an input voltage of the power converter, the switch controller determines a peak current in that switching cycle. If the peak current detected exceeds a maximum peak current, an on-time of the pulse signal in the next switching cycle is decreased. The power converter also provides short circuit or overload protection by increasing an off-time of the pulse signal until the off-time exceeds a transformer reset time of a transformer. If the switch period increased to prevent short circuit or overload exceeds a limit, the pulse signal is shut off immediately.

Abstract: A power converter delivers electrical power from an electrical power source to a load according to a plurality of operation modes, where at least one of the operation modes is a peak current switching mode. Under the peak current switching mode, a switch controller controls the switch in the power converter to be kept on until the current through the switch reaches a peak current value corresponding to a given phase of the input voltage signal to the power converter. The peak current values have a reference shape, which may be a trapezoidal. The power converter may have any topology, such as a flyback-type power converter or a boost-type power converter.

Abstract: A power converter delivers electrical power from an electrical power source to a load according to a plurality of operation modes, where at least one of the operation modes is a peak current switching mode. Under the peak current switching mode, a switch controller controls the switch in the power converter to be kept on until the current through the switch reaches a peak current value corresponding to a given phase of the input voltage signal to the power converter. The peak current values have a reference shape, which may be a trapezoidal. The power converter may have any topology, such as a flyback-type power converter or a boost-type power converter.

Abstract: A modification of a control loop of a primary side sensing power control system that uses a different and unique relationship to accomplish the constant current control while attenuating the affects of a ripple voltage.

Abstract: A hybrid constant current control system that uses both pulse width modulation (PWM) and pulse frequency modulation (PFM) control. When transitioning from constant voltage mode to constant current mode the present invention can continue to control using PWM. Thereafter, when the voltage has dropped, the present invention smoothly transitions to PFM mode. The point of transition is based upon the switching frequency and the lowest rated voltage of operation. The system and method avoids very short (narrow) Ton times which ensures accurate constant current (CC) control with bipolar junction transistor (BJT) devices. The present invention also avoids acoustic noise because the switching frequency is maintained at a high enough level to avoid such acoustic noise even when the energy transferred through the transformer is still substantial and the output voltage is not too low.

Abstract: A primary side sensing power control system and method for constant current control that utilizes a relationship that involves the measured reset-time from the previous cycle to determine the primary side peak current and off-time for the next cycle. This control mechanism does not need the knowledge of input voltage or magnetizing inductance. Therefore, it removes the sensitivities of input voltage and magnetizing inductance to the output current limit. Furthermore, it uses a time measurement instead of a voltage measurement for the current calculation which in many cases is easier to perform.