Switching power supply equipment
View Patent ↗A switching power supply equipment has a function to protect a power supply from abnormalities such as an output short-circuit. An output signal from an error amplification circuit to amplify a difference voltage between an output voltage and a predetermined voltage is input into a feedback terminal of an integrated circuit power supply control circuit, and a power transistor is controlled by a pulse-width control circuit base on the output signal. n addition, a comparator having a reference voltage and a series circuit of a capacitor and a resistor making operation of an overload protection circuit delay are connected to a connecting point of the error amplification circuit and the pulse-width control circuit. The overload protection circuit starts operation by an output of the comparator. The number of required terminals of the integrated circuit is decreased and also a package size of the integrated circuit is decreased in comparison to convention switching power supply equipment incorporating similar protection circuitry.
1. A switching power supply equipment comprising:
an error amplification circuit amplifying a difference voltage between an output voltage of the switching power supply equipment and a predetermined voltage, the error amplification circuit outputting an amplified output;
a switching control circuit coupled to the error amplification circuit, wherein operation of a switching element coupled to the switching control circuit is controlled by the switching control circuit based on the output of the error amplification circuit;
a comparator which compares a reference voltage with a voltage of a feedback terminal of the switching control circuit to which the output of the error amplification circuit is input;
a protection circuit coupled to an output of the comparator, wherein the protection circuit functions at a time of abnormality of the output voltage of the switching power supply equipment based on the output of the comparator;
a delay circuit for delaying operation of the protection circuit, wherein the delay circuit is connected to the feedback terminal and comprises a resistor and a capacitor in series, and wherein the feedback terminal is connected to a first voltage source through a first charging resistor; and
a diode between the feedback terminal and the first charging resistor wherein a cathode of the diode is connected to the feedback terminal and the feedback terminal is connected to a second voltage source through a first charging current source or a second charging resistor.
2. The switching power supply equipment according to claim 1 , wherein the switching control circuit is a pulse-width control circuit that controls a drive pulse width of the switching element.
3. The switching power supply equipment according to claim 1 , wherein one end of the capacitor is connected to the feedback terminal and one end of the resistor is connected to a ground potential.
4. The switching power supply equipment according to claim 1 , wherein one end of the resistor is connected to the feedback terminal and one end of the capacitor is connected to a ground potential.
5. A switching power supply equipment comprising:
an error amplification circuit amplifying a difference voltage between an output voltage of the switching power supply equipment and a predetermined voltage, the error amplification circuit outputting an amplified output;
a switching control circuit coupled to the error amplification circuit, wherein operation of a switching element coupled to the switching control circuit is controlled by the switching control circuit based on the output of the error amplification circuit;
a comparator which compares a reference voltage with a voltage of a feedback terminal of the switching control circuit to which the output of the error amplification circuit is input, wherein the comparator has a hysteresis characteristic;
a protection circuit coupled to an output of the comparator, wherein the protection circuit functions at a time of abnormality of the output voltage of the switching power supply equipment based on the output of the comparator;
a delay circuit for delaying operation of the protection circuit, wherein the delay circuit is connected to the feedback terminal and comprises a resistor and a capacitor in series, and wherein the feedback terminal is connected to a first voltage source through a first charging resistor;
a second charging current source and a first switching means which are provided in series between the feedback terminal and a voltage source;
a discharging current source and a second switching means which are provided in series between the feedback terminal and the ground potential;
a diode provided between the feedback terminal and the first charging resistor, wherein
a cathode of the diode is connected to the feedback terminal; and
a counter that counts the number of times that an output of the comparator is inverted,
wherein the capacitor is repeatedly charged and discharged due to the first switching means and the second switching means complementarily switching ON and OFF by the output of the comparator, and
wherein the protection circuit starts operation when counter counts to a predetermined number.
6. A switching power supply equipment comprising:
an error amplification circuit amplifying a difference voltage between an output voltage of the switching power supply equipment and a predetermined voltage, the error amplification circuit outputting an amplified output;
a switching control circuit coupled to the error amplification circuit, wherein operation of a switching element coupled to the switching control circuit is controlled by the switching control circuit based on the output of the error amplification circuit;
a comparator which compares a reference voltage with a voltage of a feedback terminal of the switching control circuit to which the output of the error amplification circuit is input, wherein the comparator has a hysteresis characteristic;
a protection circuit coupled to an output of the comparator, wherein the protection circuit functions at a time of abnormality of the output voltage of the switching power supply equipment based on the output of the comparator;
a delay circuit for delaying operation of the protection circuit, wherein the delay circuit is connected to the feedback terminal and comprises a resistor and a capacitor in series, and wherein the feedback terminal is connected to a first voltage source through a first charging resistor;
a third charging resistor and a first switching means which are provided in series between the feedback terminal and a voltage source;
a discharging resistor and a second switching means which are provided in series between the feedback terminal and the ground potential;
a diode provided between the feedback terminal and the first charging resistor, wherein a cathode of the diode is connected to the feedback terminal; and
a counter that counts the number of times that an output of the comparator is inverted;
wherein the capacitor is repeatedly charged and discharged due to the first switching means and the second switching means complementarily switching ON and OFF by the output of the comparator,
wherein the protection circuit starts operation when counter counts to a predetermined number.