CN204462918U - A step-down circuit for switches - Google Patents

Abstract

The utility model relates to communication power supply field, particularly a kind of reduction voltage circuit of switch.For a reduction voltage circuit for switch, include input voltage filtering circuit, output voltage filtering circuit, described reduction voltage circuit also comprises: low-dropout linear voltage-regulating circuit, short-circuit protection circuit and output voltage feedback circuit; And low-dropout linear voltage-regulating circuit comprises low voltage difference voltage stabilizing chip and current-limiting resistance; Between the input end that short-circuit protection circuit is connected in low pressure difference linearity voltage stabilizing chip and output terminal, burn chip for preventing low pressure difference linearity voltage stabilizing chip short circuit; Output voltage feedback circuit adopts divider resistance, for controlling the stable of output voltage.This practical new described a kind of reduction voltage circuit for switch, have low in energy consumption, ripple is little and the simple feature of circuit structure.

Description

A step-down circuit for switches

technical field

The utility model relates to the field of communication power supplies, in particular to a step-down circuit for switches.

Background technique

Since the 1990s, with the continuous improvement of computer performance and the sharp increase in the amount of information exchanged, the traditional local area network has gradually exceeded its own load. Users of all ages make it widely cover the field of communication.

However, as the amount of data processed by the switch becomes larger and larger, the workload of the switch is also increasing. For this reason, the requirements of the switch for its own power supply are also constantly increasing. However, the existing switch step-down circuit uses the traditional switching power supply BUCK chip to reduce the voltage to a specific DC voltage for power supply. Although the switching power supply has high conversion efficiency and large supply current, due to the periodic switching operation, there will be There is a lot of loss; and its output voltage usually contains high-frequency ripples, and it will cause certain electromagnetic interference to the surrounding circuits; in this way, in the design of the switching power supply, it is necessary to sacrifice the power consumption and speed of the power supply to suppress the circuit Noise and ripple in the circuit, and the circuit design is complex.

Therefore, it is necessary to create a new voltage supply circuit for the switch, and further improve the defects of high power consumption, large ripple and complex circuit of the switch in the prior art.

Contents of the invention

In view of the deficiencies above, the purpose of this utility model is to design a step-down circuit for switches. The step-down circuit has the characteristics of low loss, low ripple and simple and reliable circuit.

The technical scheme that the utility model adopts is:

A step-down circuit for a switch, including an input voltage filter circuit and an output voltage filter circuit, the step-down circuit also includes: a low-dropout linear voltage regulator circuit, a short-circuit protection circuit, and an output voltage feedback circuit;

The low-dropout linear voltage regulator circuit includes a low-dropout voltage regulator chip and a current-limiting resistor;

The short-circuit protection circuit is connected in series between the input terminal and the output terminal of the low-dropout linear voltage regulator chip, and is used to prevent the low-dropout linear voltage regulator chip from being burned due to a short circuit; the output voltage feedback circuit adopts a voltage dividing resistor for control the stability of the output voltage.

Specifically, the low-dropout linear regulator chip includes an input terminal IN, an output terminal OUT, a POK terminal, a FB terminal, an EN terminal, and a GND terminal; the short-circuit protection circuit uses a diode, and the cathode of the diode is connected to the low-voltage The output terminal OUT of the differential linear regulator chip is connected, and the anode of the diode is connected with the input terminals IN and EN of the low dropout linear regulator chip.

Specifically, the output voltage feedback circuit includes a voltage dividing resistor 1, a voltage dividing resistor 2 and a capacitor, and the voltage dividing resistor 2 is connected in parallel with the capacitor and then connected in series with the voltage dividing resistor 1, and the feedback resistor 1 and the feedback resistor 2 The common connection end of the LDO is connected to the FB end of the low dropout linear voltage regulator chip.

Specifically, the input voltage filter circuit includes an electrolytic capacitor one and a ceramic chip capacitor one connected in parallel with each other.

Specifically, the output voltage filter circuit includes an electrolytic capacitor 2 and a ceramic capacitor 2 connected in parallel with each other.

The step-down circuit for switches described in the utility model adopts a low-dropout linear voltage regulator circuit instead of a traditional switching power supply BUCK circuit. The low-dropout linear voltage regulator chip is integrated with an error amplifier, a reference voltage, a voltage comparator, and an adjustment tube. Through the output voltage feedback circuit, the output voltage sampling is fed back to the FB terminal of the low-dropout linear voltage regulator chip. Compared with the reference voltage inside the chip, it is amplified by the error detector, so as to control the adjustment tube to adjust the output voltage. Instead of using the on-off of the switch tube in the traditional switching power supply to control the output voltage, there will be no large loss due to repeated on-off of the switch; and the voltage feedback network can monitor the output voltage of the step-down circuit of the switch in real time, and The reference voltage inside the chip is compared, and the output voltage is adjusted to reduce the ripple of the output voltage; and the step-down circuit of the switch is simple.

The above description is only an overview of the technical solutions of the present utility model. In order to better understand the technical means of the present utility model, it can be implemented according to the contents of the description, and in order to make the above-mentioned and other purposes, features and advantages of the present utility model better It is obvious and easy to understand. The preferred embodiments are specifically cited below, together with the accompanying drawings, and detailed descriptions are as follows.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings that need to be used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention , for those of ordinary skill in the art, other drawings can also be obtained according to these drawings on the premise of not paying creative labor.

FIG. 1 is a schematic diagram of a circuit structure of a step-down circuit for a switch according to the present invention.

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Based on the embodiments of the present utility model, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the scope of protection of the present utility model.

Example 1:

As shown in Figure 1, a step-down circuit for switches includes an input voltage filter circuit 1, a low dropout linear voltage regulator circuit 2, a short circuit protection circuit 3, an output voltage feedback circuit 4 and an output voltage filter circuit 5; The low-dropout linear voltage regulator circuit 2 includes a low-dropout voltage regulator chip U1 and a current limiting resistor R1; the low-dropout linear voltage regulator chip U1 includes an input terminal IN, an output terminal OUT, a POK terminal, a FB terminal, an EN terminal and GND terminal; one end of the current-limiting resistor R1 is connected to the IN terminal of the low-dropout voltage regulator chip U1, and the other end of R1 is connected to the POK terminal of the low-dropout voltage regulator chip U1. After the input voltage Vin passes through the current-limiting resistor R1, it is a low-dropout voltage The voltage regulator chip U1 provides a certain bias current.

The short-circuit protection circuit 3 adopts a diode D1, and the cathode of the diode D1 is connected to the output terminal OUT of the low-dropout linear voltage regulator chip U1, and the anode of the diode D1 is connected to the input terminal IN of the low-dropout linear voltage regulator chip U1. The terminal is connected to the EN terminal; it is used to prevent the low-dropout linear voltage regulator chip from being short-circuited and burning the chip.

The output voltage feedback circuit 4 includes a voltage dividing resistor R2, a voltage dividing resistor R3 and a filter capacitor C3, and the voltage dividing resistor R3 is connected in parallel with the filter capacitor C3 and then connected in series with the voltage dividing resistor R2, and The common connection terminal of the feedback resistor 1 R2 and the feedback resistor 2 R3 is connected to the FB terminal of the low dropout linear voltage regulator chip, and the other end of the feedback resistor 1 R2 is connected to the output terminal OUT of the low dropout linear voltage regulator chip U1, and the feedback resistor Both R3 and the other end of the filter capacitor C3 are connected to the GND end of the low-dropout linear regulator chip U1 , that is, grounded. A closed-loop feedback circuit is formed to control the stability of the output voltage.

The input voltage filter circuit includes an electrolytic capacitor C1 and a ceramic capacitor C2 connected in parallel, and the output voltage filter circuit includes an electrolytic capacitor C5 and a ceramic capacitor C4 connected in parallel. The electrolytic capacitor is used to filter low-frequency ripple in the voltage, and the ceramic chip capacitor is used to filter high-frequency noise in the voltage.

The positive input terminal Vin+ of the input voltage filter circuit 1 is electrically connected to the IN terminal of the low-dropout linear voltage regulator chip U1, and the negative input terminal Vin- of the input voltage filter circuit 1 is connected to the GND terminal of the low-dropout linear voltage regulator chip U1; The positive output terminal Vout+ of the output voltage filter circuit 5 is connected to the OUT terminal of the low-dropout linear voltage regulator chip U1, and the negative output terminal Vout- of the output filter circuit 5 is connected to the GND terminal of the low-dropout linear voltage regulator chip U1.

The specific working process of the step-down circuit for the switch is: after the input voltage is filtered by the input voltage filter circuit 1 to filter the low-frequency ripple and high-frequency noise generated by the previous stage, it is input to the low-dropout linear voltage stabilizing circuit 2, and the low-voltage After the differential linear voltage regulator circuit 2 steps down the voltage and outputs it through the OUT terminal of the low-dropout linear voltage regulator chip U1, a part of the voltage is input to the load of the subsequent stage through the output voltage filter circuit 5, and the other part is supplied by the voltage dividing resistor R2 and The voltage dividing resistor 2 R3 divides and samples the voltage, and feeds back to the FB terminal of the low dropout linear voltage regulator chip U1, and the filter capacitor C3 filters out the high frequency components in the sampling voltage. When there is a deviation between the feedback voltage at both ends of the voltage dividing resistor R3 and the theoretical value of the output voltage, the feedback voltage is compared with the internal reference voltage of the low-dropout linear voltage regulator chip U1, and the differential amplification is performed through the error amplifier to generate an output regulation voltage for control adjustment The current of the tube makes the entire step-down circuit form a stable negative feedback state, thereby ensuring that the output voltage is stable at the specified value.

The implementation methods described above do not constitute a limitation to the scope of protection of the technical solution. Any modifications, equivalent replacements and improvements made within the spirit and principles of the above implementation methods shall be included in the protection scope of the technical solution.

Claims (3)

1. A step-down circuit for a switch, comprising an input voltage filter circuit and an output voltage filter circuit, characterized in that: it also includes a low-dropout linear voltage regulator chip, a short circuit protection circuit and an output voltage feedback circuit, Low-dropout linear regulator chip, including input terminal IN, output terminal OUT, POK terminal, FB terminal, EN terminal and GND terminal; The short-circuit protection circuit includes a diode, and the cathode of the diode is connected to the output terminal OUT of the low-dropout linear voltage regulator chip, and the anode of the diode is connected to the input terminal IN and EN of the low-dropout linear voltage regulator chip for Prevent the low dropout linear voltage regulator chip from being burned due to short circuit; The output voltage feedback circuit includes a voltage dividing resistor 1, a voltage dividing resistor 2 and a capacitor, and the voltage dividing resistor 2 is connected in parallel with the capacitor and then connected in series with the voltage dividing resistor 1, and the common connection between the feedback resistor 1 and the feedback resistor 2 The terminal is connected with the FB terminal of the low dropout linear regulator chip. 2 . The step-down circuit for a switch according to claim 1 , wherein the voltage filtering circuit comprises an electrolytic capacitor 1 and a ceramic capacitor 1 , and the electrolytic capacitor 1 and ceramic capacitor 1 are connected in parallel with each other. 3 . 3. A step-down circuit for a switch according to claim 1, characterized in that: said output voltage filter circuit comprises electrolytic capacitor two and ceramic capacitor two, said electrolytic capacitor two and ceramic capacitor two mutually in parallel.