Abstract: Disclosed are a power-loss delay circuit and a detection control circuit thereof. The power-loss delay circuit and the corresponding detection control circuit are added onto a flyback circuit. When a product is working normally, an energy storage capacitor is charged, and when an input power supply of the product is cut off, the detection control circuit detects that an input voltage of the product drops to a set value and triggers the control circuit to drive a switch transistor to be turned on, so that the energy of an energy storage capacitor is released, thereby keeping the product working continuously for a period of time. The power-loss delay circuit and the detection control circuit thereof have no effect on the normal working state of the product. When the input power is cut off, capacitance stored in an external capacitor is introduced in time to keep the product working continuously.

Abstract: There is provided a to-be-protection circuit that is high in operation accuracy and that prevents overvoltage on a protected circuit. A protection circuit is configured to protect a to-be-protected circuit from overvoltage. The to-be-protected circuit is connected to an external output terminal. The protection circuit includes: a current path unit connected to the external output terminal and including at least one first element; a reference voltage generation unit which generates and outputs a reference voltage; and an amplifier circuit outputs a target voltage based on a difference between a first input voltage and a second input voltage. The amplifier circuit operates using the reference voltage as the first input voltage and using a feedback voltage based on the target voltage as the second input voltage, and outputs the target voltage to the current path unit.

Abstract: An active flyback converter is transitioned between a plurality of operational states based on a comparison of a control voltage signal to voltage thresholds and a count of a number of consecutive switching cycles during which a clamp switch is kept off. The plurality of operational states includes a run state, an idle state, a first burst state, and a second burst state. Each set of consecutive switching cycles of the first burst state includes a determined number of switching cycles during which signals are generated to turn the power switch on and off and to maintain an off state of the clamp switch, and a switching cycle in a determined position in the set of switching cycles during which signals are sequentially generated to turn the power switch on, turn the power switch off, turn the clamp switch on and turn the clamp switch off.

Abstract: A Dielectric Barrier Discharge system controller for controlling a fluid treatment by a Dielectric Barrier Discharge system is provided. Therein, the strength of an effect caused by a discharge created by the Dielectric Barrier Discharge system is monitored, and the generation of high-voltage pulses by the high-voltage pulse generator is controlled. The controlling of the generation of the high-voltage pulses is adapted based on the received sensor data.

Abstract: A power control device includes a mode setter configured to effect a change from a normal mode to a low-power mode upon detecting a light load in a burst operation, and a minimum on-period setter configured to, in response to a change to the low-power mode, change the minimum on-period of the switching transistor from a first minimum on-period to a second minimum on-period longer than the first minimum on-period.

Abstract: Disclosed is an asymmetric half-bridge flyback converter and a control method, including: in an initial switching cycle of the asymmetric half-bridge flyback converter, obtaining a pre-turnoff time of the second switch transistor, and controlling the second switch transistor to be turned off after a delay which lasts for a first time and starts at the pre-turnoff time of the second switch transistor; in a non-initial switching cycle of the asymmetric half-bridge flyback converter, obtaining a judgment result by judging whether the first switch transistor is operated with zero-voltage switching in a current switching cycle, and adjusting a length of the first time based on the judgment result. The present disclosure can realize zero-voltage switching of the asymmetric half-bridge flyback converter, and at the same time, satisfy a requirement for achieving more ideal dead-time setting under a wider range of input voltage and a wider range of output voltage.

Abstract: A sampling circuit for a switching power supply, can include: a first sampling circuit configured to acquire a first sampling signal of a current flowing through an inductor in the switching power supply; and a second sampling circuit configured to obtain a compensation signal with a same rising slope as the first sampling signal within a turn-off delay time of a power switch in the switching power supply, and to superimpose the compensation signal on the first sampling signal to generate a second sampling signal.

Abstract: The present invention provides a driving circuit for a switching transistor and a driving device including the same.

Abstract: A power supply control device that controls a switching element of a switching power supply apparatus which includes a transformer having a primary winding, a secondary winding, and an auxiliary winding, the switching element coupled to the primary winding, and a capacitor coupled to the auxiliary winding, includes: a power supply terminal coupled to one end of the capacitor; a switch and a resistor coupled in series between the power supply terminal and a ground; a first control circuit that controls the switch; and a second control circuit that controls the switching element, in which the first control circuit performs control to turn on the switch when a first voltage applied to the power supply terminal continuously exceeds a first reference voltage for a first time, and the second control circuit performs control to turn off the switching element when the first voltage exceeds a second reference voltage higher than the first reference voltage.

Abstract: System and method for providing at least an output current to one or more light emitting diodes. The system includes a control component configured to receive at least a demagnetization signal, a sensed signal and a reference signal and to generate a control signal based on at least information associated with the demagnetization signal, the sensed signal and the reference signal, and a logic and driving component configured to receive at least the control signal and output a drive signal to a switch based on at least information associated with the control signal. The switch is connected to a first diode terminal of a diode and a first inductor terminal of an inductor. The diode further includes a second diode terminal, and the inductor further includes a second inductor terminal.

Abstract: A switch-mode power supply (SMPS), an SMPS system and a power supply method for an SMPS system are disclosed. The SMPS controller includes an output-voltage power supply unit, a built-in energy storage unit and a logic control unit. The output-voltage power supply unit is configured to charge the built-in energy storage unit using an output voltage from the SMPS system so that the built-in energy storage unit can provide an operating voltage for the logic control unit. The use of a stand-off energy storage capacitor can be dispensed with, and the use of the output voltage as a power supply is enabled. As a result, significant reductions in overall and standby power dissipation are achieved. In addition, the SMPS controller may further include a high-voltage power supply unit, which provides a hybrid power supply solution, together with the output-voltage power supply unit.

Abstract: Overload detection and protection for power switch circuits. For circuits with faster switching speed, fast fault detection and response to a detected overload condition may be desirable. Detection circuitry may monitor a voltage on the control terminal of one or more power switches. Based on empirical measurements, in an overload condition of a power switch circuit, e.g., a half-bridge circuit, the voltage at the control terminal may increase, and in some examples, increase to a magnitude that is greater than a supply voltage. A comparator may detect a voltage increase that exceeds a voltage magnitude threshold, output an indication to control circuitry for the power switch circuit, and the control circuitry may take action to protect the rest of the circuitry, such as reduce voltage or shut off the power switch circuit.

Abstract: A power converter system converts power from an input source for delivery to an active load. An input current surge at startup may be reduced by combining power converter switch resistance modulation with active load control. In another aspect, an input current surge at startup in an array of power converters may be reduced by periodically reconfiguring the array during the startup phase to accumulatively increase the output voltage up to a predetermined output voltage. A power converter may include a controller that provides an over-current signal to the load to reduce the load or advise of potential voltage perturbations.

Abstract: A method of operating a MEMS device includes generating a MEMS drive signal, and generating and modifying the MEMS drive signal based upon a control signal to produce a modified drive signal. The method further includes generating the control signal by determining when a feedback signal from the MEMS device is at its peak value, comparing the peak value to a desired value when the feedback signal is as its peak, and generating the control signal depending upon whether the peak value is at least equal to a desired value. The modification of the MEMS drive signal based upon the control signal to produce the modified drive signal includes skipping generation of a next pulse of the modified drive signal when the control signal indicates the peak value is at least equal to the desired value.

Abstract: A control circuit, system and method for switched-mode power supply are disclosed, the control circuit is for driving a first switch to convert an input voltage into an output voltage. The control circuit includes an on-time control unit, which receives a first signal characterizing switching frequency of first switch and a second signal characterizing current flowing through first switch and responsively generates a signal indicative of a turn-off instant for first switch. When a peak value of the current flowing through the first switch drops below a predefined value, the on-time control unit determines the turn-off instant for the first switch based on the first signal so that the switching frequency of the first switch is maintained at a target frequency. This design can effectively avoid the generation of audible noise, stabilize the output voltage against loading changes while maintaining desirable efficiency, and ensure operational safety of the switched-mode power supply.

Abstract: System controller and method for regulating a power converter. For example, the system controller includes a first controller terminal and a second controller terminal. The system controller is configured to receive an input signal at the first controller terminal and generate a drive signal at the second controller terminal based at least in part on the input signal to turn on or off a transistor in order to affect a current associated with a secondary winding of the power converter. Additionally, the system controller is further configured to determine whether the input signal remains larger than a first threshold for a first time period that is equal to or longer than a first predetermined duration.

Abstract: A power converter system converts power from an input source for delivery to an active load. An input current surge at startup may be reduced by combining power converter switch resistance modulation with active load control. In another aspect, an input current surge at startup in an array of power converters may be reduced by periodically reconfiguring the array during the startup phase to accumulatively increase the output voltage up to a predetermined output voltage. A power converter may include a controller that provides an over-current signal to the load to reduce the load or advise of potential voltage perturbations.

Abstract: Communicating fault conditions between primary-side and secondary-side controllers of a Universal Serial Bus Power Delivery (USB-PD) device is described. The primary-side controller receives a control signal from the secondary-side controller across a galvanic isolation barrier. The primary-side controller converts the control signal into a first pulse signal and applies the first pulse signal to control a primary-side switch. When the primary-side controller detects that a first fault condition has occurred, the primary-side controller communicates a first information signal about the first fault condition to the secondary-side controller across the galvanic isolation barrier. The first information signal is generated by converting the control signal into a second pulse signal having a different pulse width than the first pulse signal. The primary-side controller applies the second pulse signal to control the primary-side power switch.

Abstract: The present invention concerns a power converter including: a capacitor (CBUS) having first and second electrodes respectively coupled to first (E1) and second (E2) input terminals via a current-limiting element (R1, L1); at least one normally-on transistor (K1, K2, K3, K4, K5, K6); a circuit (170) for powering a circuit (CMD_K1, CMD_K2) for controlling the normally-on transistor; and a switch configurable to, in a first configuration, couple first (g) and second (h) input terminals of the power supply circuit (170) respectively to the first (E1) and second (E2) input terminals of the converter, upstream of the current-limiting element (R1, l1) and, in a second configuration, connect the first (g) and second (h) input terminals of the power supply circuit (170) respectively to the first and second electrodes of the capacitor, downstream of the current-limiting element (R1, L1).

Abstract: An embodiment DC to DC conversion circuit comprises a DC to DC converter and a regulation circuit. The regulation circuit comprises a comparator configured to detect, during a discharge phase of the DC to DC converter, an overshoot period during which an output voltage of the DC to DC converter exceeds a target voltage, and a timer configured to measure a duration of the overshoot period.

Abstract: A power supply circuit having a first capacitor, a transformer including a primary coil having a voltage of the first capacitor applied thereto, a secondary coil and an auxiliary coil, a second capacitor having a voltage from the auxiliary coil applied thereto, a transistor controlling an inductor current flowing through the primary coil, a control circuit outputting a first control signal when supply of the input voltage is unstopped, or is stopped yet a voltage of the second capacitor reaches a first level, and outputting a second control signal thereafter when the voltage of the second capacitor further reaches a second level, a first drive circuit outputting a first drive signal for switching control of the transistor in response to the first control signal, and a second drive circuit outputting a second drive signal for controlling on-resistance of the transistor to discharge the first capacitor, in response to the second control signal.

Abstract: In a transmission circuit, a first pulse signal with a first frequency and a second pulse signal with a second frequency are output according to a rising edge and a falling edge of a first input signal, respectively. When a second input signal indicates an active level, the second pulse signal is output according to the falling edge of the first input signal and the second frequency is changed to a third frequency. In a reception circuit, a first level of a first output signal is changed to a second level according to a first induced signal via a transformer, the second level of the first output signal is changed to the first level according to a second induced signal via the transformer, and a second output signal is changed to an active level when a frequency of the second induced signal has changed to the third frequency.

Abstract: A power supply receives AC power and generates a DC output voltage. The power supply may be divided into a primary section that converts AC power to a relatively high DC voltage. A secondary section converts this relatively high DC voltage into a well-regulated lower DC voltage. In an embodiment, the current and/or power supplied by the primary to the secondary side is used by the secondary side in a closed-loop feedback system to limit the current drawn by the secondary side to a configurable value.

Abstract: A power converter includes a power switch controlling current flow in the power converter and a variable capacitance coupled in parallel to the power switch. The variable capacitance is configured to add a frequency jitter to the power converter.

Abstract: A converter system (100) includes a transformer (102) having a primary side (104) and a secondary side (106), a first switch (114) with a first terminal (1151) coupled to the primary side (104) and a second terminal (1152) coupled to a voltage supply terminal, a second switch (116) coupled to the first terminal (1151) of the first switch (114), loop control circuitry (119), coupled to the secondary side (106), and configured to generate an offset signal based on an output voltage provided at the secondary side (106) and to generate a compensated signal by compensating the offset signal to a sensed signal being representative of a first current flowing through the primary side (104), and switch control circuitry (120), coupled to the loop control circuitry (119), and configured to operate the first and second switches (114, 116) based on the compensated signal.

Abstract: A hysteresis voltage detection circuit includes a voltage stabilizing unit, a first power switch, a first voltage dividing resister, a second voltage dividing resister, a third voltage dividing resistor and a second power switch. The voltage stabilizing unit is coupled to an adjustable voltage source. When both the first power switch and the second power switch are turned on, the first voltage dividing resistor, the second voltage dividing resistor, and the third voltage dividing resistor divide the adjustable voltage source. When both the first power switch and the second power switch are turned off, the first voltage dividing resistor and the second voltage dividing resistor divide the adjustable voltage source.

Abstract: A power supply apparatus (10) suppressing a transient voltage is applied to an input voltage (50). The power supply apparatus (10) includes a power supply circuit (20), a feedback signal generation circuit (30) and a feedback signal control circuit (40). If the power supply circuit (20) stops receiving the input voltage (50), the feedback signal control circuit (40) controls the feedback signal generation circuit (30) to discharge so that the feedback signal generation circuit (30) controls the power supply circuit (20) to decrease an output voltage (60), so that when the power supply circuit (20) receives the input voltage (50) again, the power supply circuit (20) avoids generating an output overvoltage condition for the output voltage (60).

Abstract: A power supply circuit includes an inductor, a power transistor configured to control an inductor current flowing through the inductor, and an integrated circuit driving the power transistor. The integrated circuit includes a first terminal that receives a power supply voltage for operating the integrated circuit, generated according to a variation in the inductor current, a second terminal to which a control electrode of the power transistor is coupled, a first drive circuit configured to drive the power transistor via the second terminal during a first time period to turn on the power transistor, and a second drive circuit configured to drive the power transistor via the second terminal during a second time period to turn on the power transistor, the second time period including at least a part of the first time period, driving capability of the second drive circuit being lower than that of the first drive circuit.

Abstract: A method for improving the conversion efficiency of a CCM mode of a flyback resonant switch power supply, comprising: presetting a critical value Tset, calculating a time interval Ttap between adjacent zero points in the current connection time, outputting a shutdown signal at the zero points, and comparing the time interval Ttap with the preset critical value Tset; when Ttap>Tset, controlling the current shutdown time to be less than the shutdown time of the preceding cycle and outputting a start signal; when Ttap=0, controlling the current shutdown time to be greater than the shutdown time of the preceding cycle and outputting a start signal; and when 0<Ttap<=Tset, controlling the current shutdown time to be the same as the shutdown time of the preceding switch cycle and outputting a start signal.

Abstract: An embodiment DC to DC conversion circuit comprises a DC to DC converter and a regulation circuit. The regulation circuit comprises a comparator configured to detect, during a discharge phase of the DC to DC converter, an overshoot period during which an output voltage of the DC to DC converter exceeds a target voltage, and a timer configured to measure a duration of the overshoot period.

Abstract: A flyback converter having a transformer that includes a primary coil connected to the input terminal and a secondary coil, a semiconductor switch configured to switch current flow through the primary coil, a first measurement unit configured to measure the DC input voltage, and a second measurement unit configured to measure a voltage across the semiconductor switch. The flyback converter also includes a control unit having a synchronization terminal and configured to output a switching signal to the semiconductor switch with a constant frequency in accordance with a synchronization signal input to the synchronization terminal. In addition, the flyback converter includes a frequency adjustment unit configured to transmit a synchronization signal to the synchronization terminal based on the DC input voltage and the voltage measured by the second measurement unit such that the frequency of the switching signal output from the control unit becomes variable.

Abstract: System and method are provided for regulating a power converter. The system includes a signal processing component configured to receive a first input signal and a second input signal, process information associated with the first input signal and the second input signal, and output a drive signal to a switch based on at least information associated with the first input signal and the second input signal. The first input signal is associated with at least a feedback signal related to an output voltage of the power converter. The second input signal is associated with at least a primary current flowing through a primary winding of the power converter. The signal processing component is further configured to change a peak value of the primary current within a first predetermined range, and change the switching frequency of the power converter within a second predetermined range.

Abstract: A flyback converter control architecture is provided in which primary-only feedback techniques are used to ensure smooth startup and detection of fault conditions. During steady-state operation, secondary-side regulation is employed. In addition, current limits are monitored during steady-state operation using primary-only feedback techniques to obviate the need for a secondary-side current sense resistor.

Abstract: A method includes generating a gain transition signal in response to any one of an average value of a feedback signal, a slope of the feedback signal, a slope of an input signal of the power converter, a maximum value of the input signal, and a minimum value of the input signal, and generating a first gain control signal and a second gain control signal in response to the gain transition signal. A gain transition controller includes a transition signal generator generating the gain transition signal and a gain control signal generator generating the first gain control signal and the second gain control signal in response to the gain transition signal.

Abstract: Techniques are provided for avoiding an avalanche breakdown voltage across a synchronous rectification (SR) switch on the secondary side of an isolated switched-mode power converter operating in a low-power mode, e.g., a burst mode, during which a load of the power converter draws negligible current. This is accomplished via use of a two-level switch driver for controlling a power switch on the primary side of the power converter. The two-level switch driver is configured to source low current levels to a control terminal (e.g., gate) of the power switch during burst-mode operation. This low current reduces the slope of the rising edge of voltage pulses on the primary and secondary sides of the power converter which, in turn, limits the peak of the voltage ringing across the SR switch. By limiting the voltage in this manner, the SR switch avoids entering avalanche breakdown.

Abstract: A system for regulating an output of a switched mode power supply circuit is configured to provide electric power to a load. The system may include a filter circuit. The filter circuit may be configured to suppress ripple signals at the power output. The system may include a feedback sense circuit including at least one feedback input end and at least one feedback output end. The feedback sense circuit may be configured for generating a feedback signal based on an output ripple signal at a filter input end and a DC regulation signal at a filter output end. The at least one feedback output end may be configured to be electrically coupled to the switched mode power supply circuit. Further, a switching of the switched mode power supply circuit may be based on the feedback signal.

Abstract: A switching power supply device includes: a rectifier circuit to which an AC input voltage is input; an input smoothing circuit smoothing a DC input voltage output from the rectifier circuit; a power converter circuit converting the DC input voltage and outputs an output voltage; an overvoltage detection circuit generating an input overvoltage detection signal which is activated when the DC input voltage is higher than a first reference voltage level; and a discharge circuit discharging stored charge stored in the input smoothing circuit. The power converter circuit includes a switching element. Switching of the switching element is stopped and discharging of the stored charge is started, with activation of the input overvoltage detection signal serving as a trigger, and when the input overvoltage detection signal is subsequently inactivated, the discharging is stopped and the switching of the switching element is resumed.

Abstract: A clock generation circuit, which generates an output clock using an external clock as a target clock, includes a circuit arranged to change the output clock to high level in synchronization with an up edge of the target clock, circuits arranged to generate first and second ramp voltages with a period of interval between neighboring up edges of the target clock, and a circuit arranged to hold a comparison voltage corresponding to a second ramp voltage when an up edge of the target clock occurs. The level of the output clock is changed from high level to low level based on a comparison result between the first ramp voltage and the comparison voltage.

Abstract: A switching power supply device has both a turn-on timing modulation function and a turn-off timing modulation function, performs the turn-off timing modulation in a PFM control region and the turn-on timing modulation in a PWM control region, and further continues at least one of the modulations even after the PFM control and the PWM control are switched from one to the other, to achieve a stable operation of the switching power supply device at the control switching boundary without significantly decreasing the modulation effect of frequency jitter control.

Abstract: A rectifying element is connected to an auxiliary winding. The shut-down circuit receives a bias voltage output from the rectifying element. A shut-down circuit stops supply of power to a power supply terminal of the power supply control IC when the bias voltage is less than a set voltage. A power supply control IC controls a ratio of on-time to a switching cycle of the switching element, based on a current sensing voltage generated at a current sense resistor. The power supply control IC causes the switching operation of the switching element to stop when a voltage at the power supply terminal decreases to a stop voltage or less.

Abstract: An electrical circuit for charging a secondary battery that comprises a dc-converter and an output connector that can be connected to the positive terminal of the secondary battery for applying a charging current to the secondary battery. The dc-converter has a voltage feedback connector for sensing a feedback voltage, wherein the dc-converter is adapted to regulate the output voltage by adjusting the output current at the output connector depending on the sensed feedback voltage and a feedback-sub-circuit connected to the output connector and to the voltage feedback connector of the dc-converter.

Abstract: Voltage converter controllers, voltage converters and methods are discussed regarding the adjustment of an on-time of an auxiliary switch of a voltage converter. First and second voltages are measured before a primary switch of the voltage converter is turned on and while the primary switch is turned on, and the on-time is adjusted based on the voltages.

Abstract: A power conversion device includes a primary side rectifier, a main converter, a secondary side rectifier, a secondary side feedback controller, a PWM controller, and a driving compensator. The primary side rectifier is configured to generate a first voltage. The main converter includes a power transistor and is configured to adjust the first voltage to generate a second voltage according to a control signal. The secondary side rectifier is configured to generate an output voltage according to the second voltage. The secondary side feedback controller is configured to generate a feedback signal according to the output voltage. The PWM controller is configured to generate a PWM signal according to the feedback signal. The driving compensator includes a driving resistor circuit. The PWM signal outputs the control signal through the driving resistor circuit, and the driving compensator adjusts a resistance value of the driving resistor circuit according to the first voltage.

Abstract: A sample-and-hold circuit includes a first voltage generation unit, a second voltage generation unit, a stabilization capacitor. The first voltage generation unit generates a first voltage according to a first predetermined delay time and a voltage corresponding to an auxiliary winding of a power converter. The second voltage generation unit generates a second voltage according to K multiple of a discharge time of a secondary side of the power converter during a previous period of the power converter and the voltage, wherein K<1. When a sum of the K multiple of the discharge time and a second predetermined delay time leads a first valley of the voltage corresponding to a current period of the power converter, the second voltage generation unit outputs the second voltage. When the sum lags the first valley, the first voltage generation unit outputs the first voltage.

Abstract: A control arrangement is disclosed for a switch mode power supply (SMPS), the SMPS comprising an opto-coupler configured to transfer, from a secondary side to a primary side of the switch mode power supply by means of an LED current, a control signal indicative of an error between an amplifier-reference-signal and an amplifier-sensed-signal indicative of an actual value of an output parameter, the control arrangement comprising: an error amplifier configured to integrate the error to determine the LED current; and a feedback loop configured to adjust the magnitude of the LED current by modifying the amplifier-reference-signal or the amplifier-sensed-signal in order to reduce the error. A SMPS comprising such a control arrangement, and a corresponding method is also disclosed.

Abstract: Provided is a power control apparatus for sub-modules in an MMC, which controls stable supply of power to sub-modules in MMC connected to an HVDC system and a STATCOM. The power control apparatus has at least one first resistor connected between P and N buses of MMC; a second resistor connected in series with the first resistor; a switch connected in series with the second resistor; a third resistor connected in parallel with the second resistor and the switch which are connected in series; a Zener diode connected in parallel with the third resistor; and a DC/DC converter connected between both ends of the Zener diode and configured to convert voltage across both ends of the Zener diode into low voltage, and supply the low voltage to the sub-modules, wherein a magnitude of current flowing through the Zener diode is controlled depending on ON/OFF switching of the switch.

Abstract: The proposed variant devices are intended for producing a highly stable constant voltage in a wide range of output voltages. A highly stable constant voltage is produced by generating a control signal which adjusts the relative pulse duration as a constant voltage is converted into a pulse voltage, taking into account a constant voltage setpoint value in the load, while also stabilizing a constant current and reducing the pulse components in the constant current through the use of negative feedback.

Abstract: In some examples, a control circuit is configured to control a transistor, and the control circuit includes a leading-edge detection unit configured to detect a time interval that corresponds to a leading-edge current spike through the transistor, wherein the time interval is independent of temperature. In some examples, the control circuit also includes a blanking unit configured to prevent the control circuit from turning off the transistor during the time interval.

Abstract: Apparatus and associated methods relate to continuously providing power to a load throughout an interruption of a power source. While the power source is providing power, a converter is exciting a primary winding of a transformer. A load winding of the transformer delivers power to a load connected thereto, and a holdup winding provides power to a holdup circuit, which stores energy for use when the power source is interrupted. A turns ratio of the holdup winding to the primary winding is greater than one so that the energy stored by the holdup circuit is at a voltage that is greater than or equal to the voltage used for exciting the primary windings. If the voltage used for exciting the primary windings falls below a predetermined threshold, a one-shot controls the transfer of energy stored in the holdup circuit to a storage capacitor supplying current to the primary windings.

Abstract: In one form, a switched mode power supply controller with frequency foldback includes a pulse width modulator responsive to a clock signal to generate a drive signal having a pulse width that varies in response to a feedback signal, and a variable frequency oscillator having a first input for receiving the feedback signal, a control input for receiving a programmable control signal defining a foldback starting frequency, a foldback ending frequency, a foldback starting voltage, and a foldback ending voltage, and an output for providing the clock signal having a variable frequency that varies over a range between the foldback starting frequency and the foldback ending frequency as the feedback signal varies between the foldback starting voltage and the foldback ending voltage, respectively. In another form, a switched mode power converter uses such a switched mode power supply controller with an inductive element, switch, and feedback circuit.