Stmicroelectronics S.r.l.

Sgs-thomson Microelectronics S.r.l.

Mauro Fagnani

Claudio Adragna

Albino Pidutti

Giuseppe Gattavari

Ugo Moriconi

Francesco Pulvirenti

Gregorio Bontempo

Paolo Sandri

Bruno Ferrario

Vincenzo Bartolo

Roberto Quaglino

A device corrects the power factor in forced switching power supplies and includes a converter and a control device to obtain a regulated voltage on an output terminal. The control device comprises an error amplifier having an inverting terminal (Vout) and a non-inverting terminal receiving a reference voltage. The device includes first and second resistances coupled in series with a conduction element positioned between the first resistance and the inverting terminal of the error amplifier and a fault detector suitable for detecting the electrical connection of the conduction element with the output terminal and suitable for detecting an output signal of the second resistance. The fault detector is suitable for supplying a malfunction signal upon detecting an electric disconnection of the conduction element from the output terminal or when the output signal of the second resistance tends to zero.

Fault detection for loss of feedback in forced switching power supplies

Herein described is a control device of a device for the correction of the power factor in forced switching power supplies; said device for the correction of the power factor comprises a converter and said control device is coupled to the converter to obtain from an alternating input line voltage a regulated output voltage. The control device comprises generating means associated to a capacitor for generating a signal representative of the root-mean-square value of the alternating line voltage; the generating means are associated to means for discharging said capacitor. The control device comprises further means for discharging the capacitor suitable for discharging said capacitor when the signal representative of the root-mean-square value of the alternating line voltage goes below a given value.

Control device for power factor correction device in forced switching power supplies

A circuit for reducing the variations of auto-supply voltage of a control circuit of a switching power supply, where the control circuit supplies an activation or deactivation signal of a power transistor, includes an auto-supply voltage generator, a controlled switch capable of selectively connecting the generator to the control circuit, and a driving circuit of the controlled switch that supplies a closing signal of the controlled switch after a predefined delay of time starting from the deactivation command.

Circuit for reducing the variations of auto-supply voltage of a control circuit of a switching power supply

Fault detection for loss of feeback in forced switching power supplies with power factor correction

A bootstrap circuit for switching power supplies (SMPS), a switching power supply including a bootstrap circuit, and an integrated circuit of a switching power supply, are provided. The bootstrap circuit () for switching power supplies includes a first supply voltage (Vin) coming from a first terminal and a second supply voltage (Vcc) coming from a second terminal and a third terminal (). The bootstrap circuit includes: a first current path between the first terminal and the third terminal (); a second current path between the first terminal and the second terminal; a third current path between the second terminal and the third terminal (); and a two-way voltage regulator (M, Dz, R, R) placed along the second current path.

Starting circuit for switching power supplies

A device for power factor correction in a forced switching power supply unit is provided. The device includes a converter and a control device coupled to the converter so as to obtain from an input alternating mains voltage a direct regulated voltage on the output terminal. The converter includes a power transistor, and the control device includes an error amplifier having its inverting terminal coupled to a first signal that is proportional to the regulated voltage and its non-inverting terminal coupled to a reference voltage. A drive circuit of the power transistor is coupled to the output terminal of the error amplifier. The control device also includes a circuit for generating a current signal that is representative of the effective input voltage. The current signal is coupled to the inverting terminal of the error amplifier to vary the regulated voltage in reply to variations in the effective input voltage.

Device for power factor correction in forced switching power supply units

A circuit is provided for controlling a minimum operating voltage of an integrated control circuit of a switching power supply. The circuit includes at least one switch for switching the minimum operating voltage from a first voltage value to a second voltage value under conditions of low or null load of the switching power supply, and for switching the minimum operating voltage from the second voltage value to the first voltage value if the load of the switching power supply is greater than a predetermined load and the supply voltage is greater than the first voltage value. The minimum operating voltage can assume at least the first voltage value and the second voltage value, and the first voltage value is greater than the second voltage value. Also provided is a method for controlling a minimum operating voltage of an integrated control circuit of a switching power supply.

Circuit for controlling the minimum operating voltage of switching power supply

A device is described for the correction of the power factor in power supply units with forced switching operating in transition mode. Said device comprises a converter and a control device coupled with said converter so as to obtain a regulated voltage on the output terminal from an alternating network input voltage. The converter comprises a power transistor whilst the control device comprises a pilot circuit suitable for determining the switch-on time and the switch-off time of the power transistor. The control device furthermore comprises control means coupled with said pilot circuit and with said converter and capable of prolonging the switch-on time of the power transistor at the instants of time wherein the alternating network voltage substantially takes on the value zero.

Device for the correction of the power factor in power supply units with forced switching operating in transition mode

A device for the correction of the power factor in power supply units with forced switching operating in transition mode is described. The device comprises a converter and a control device coupled to said converter so as to obtain from an alternating network input voltage a regulated output voltage on the output terminal. The converter comprises a power transistor and the control device comprises a pilot circuit suitable for determining the period of switched-on time and the period of switched-off time of said power transistor and control means coupled to said pilot circuits and with said converter and which are capable of prolonging said period of switched-on time of the power transistor at the instants of time in which the alternating network voltage substantially assumes the value zero.

The power supply device includes a DC-DC converter circuit having a power switch and a driving stage. The driving stage has a compensation terminal on which a compensation voltage is present, and which receives a biasing current. The driving stage includes a control circuit having an output terminal connected to a control terminal of the power switch and disconnection-detecting circuitry connected to the compensation terminal and generating a signal for permanent turning-off of the power switch when the biasing current drops below a current-threshold value. The driving stage moreover includes over-voltage detecting circuitry connected to the compensation terminal and generating a signal for temporary turning-off of the power switch when the compensation voltage exceeds a voltage-threshold value.

Switching mode power supply device with detection of malfunctioning

A self-disabling and self-recovering converter includes a transformer connected to a power source and has an auxiliary winding for providing a self-supply voltage after start-up, and an integrated circuit having circuitry and a plurality of pins connected thereto. The converter also includes at least one external line and a sensor connected thereto for an electrical or physical quantity to be monitored. The at least one external line is biased through a first pin with the self-supply voltage, and is functionally coupled to a second pin when a threshold is surpassed. A sectionable voltage clamp chain is connected between the auxiliary winding and a voltage reference. A self-recovery circuit having a first input is connected to the auxiliary winding and a second input is connected through the second pin to the at least one external line. An output of the self-recovery circuit is connected to the sectionable voltage clamp chain for sectioning a portion thereof to the voltage reference for self-supplying the integrated circuit.

Self-recovering disabling system for converter

The power output of a static DC--DC converter employing a current mode PWM controller is controlled upon the varying of the switching frequency, by detecting the sawtooth signal produced by the local oscillator generating a DC signal with an amplitude inversely proportional to the frequency. The power output is controlled by alternatively clamping the output voltage of the error amplifier of the PWM controller at a voltage proportional to the amplitude of the DC signal, or by offsetting the signal present on the current sensing resistor by a voltage corresponding to the difference between a constant voltage and the DC signal.

Control of the output power of a DC-DC converter upon varying the

A circuit for regulating the charging time of the output node of an amplifier at start up. The output node commonly comprises an external soft-start capacitor charged by a current delivered by a pull-up transistor of a push-pull output stage of the amplifier, through a decoupling diode that is functionally connected between the output node of the amplifier and a terminal of the external soft-start capacitor. The present application provides a current mirror feed back circuit capable of mirroring the charge current of the external soft-start capacitor onto the driving node of the pull-up transistor of the output stage of the amplifier. The regulating circuit permits use of an external capacitance of extremely small size. Upon the reaching of a fully charged condition by the external capacitor, the control circuit self-isolates and does not influence in any way the normal operation of the amplifier.

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Nerviano, Italy

Mauro Fagnani