DC-to-DC converter operating in a discontinuous mode.

摘要

A converter employs a comparator (C3) sensing the current through an output diode (D), for generating a confirmation signal of an OFF state of the switch (M1) until the discharge current of the inductor (L) toward the user circuit and the external filter capacitance (C) has become null, thus ensuring the operation in a discontinuous mode under any condition. A turn-off signal of the switch (M1) is provided by another comparator (C2) which, instead of the voltage on a sensing resistance connected in series with the switch, may sense the voltage across the switch (M1) itself. This latter embodiment is particularly suited in case of an output MOS transistor and the circuit comprises means for masking for a preset period of time the turn-off signal produced by said comparator (C2), in order to allow a predefined turn-on phase of the switch. Enabling of the turn-on of the switch (M1) is conventionally provided by a dedicated (third) comparator (C1) of the output voltage. The circuit does not require the use of an error amplifier, for the compensation of which special complex integratable circuits or alternatively access to the output node of the error amplifier through a dedicated pin may be needed. <IMAGE>