CN215956266U

CN215956266U - DC power supply slow starting circuit with current limiting function

Info

Publication number: CN215956266U
Application number: CN202122294665.6U
Authority: CN
Inventors: 苏伟达; 李汪彪
Original assignee: Fujian Supwit Group Co ltd
Current assignee: Fujian Supwit Group Co ltd
Priority date: 2021-09-18
Filing date: 2021-09-18
Publication date: 2022-03-04
Anticipated expiration: 2031-09-18

Abstract

The utility model provides a direct-current power supply slow starting circuit with a current limiting function, which comprises a current detection unit 1, a comparison unit 2, a delay electrifying unit 3 and a switch unit 4, wherein a VIN end and a GND end are respectively an anode and a cathode of a power input end, a VOUT end and a GND1 end are respectively an anode and a cathode of a power output end, the input end of the delay electrifying unit is connected with the VIN end, the output end of the delay electrifying unit is connected with a same-phase end of the comparison unit, the current detection unit is respectively connected with the VIN end and the VOUT end, and the current detection unit is used for detecting current between the VIN end and the VOUT end and outputting detection voltage. The slow starting circuit formed by the current detection unit, the delayed power-on unit and the comparison unit can gradually increase output current during power-on, reduce current impact, realize accurate control of the maximum output current and improve the stability and reliability of the system.

Description

DC power supply slow starting circuit with current limiting function

Technical Field

The utility model relates to the field of a slow starting circuit of a direct-current power supply, in particular to a slow starting circuit of a direct-current power supply with a current limiting function.

Background

The DC power supply slow starting circuit can effectively reduce the impact of the circuit on a power supply when the circuit is powered on, avoid the abnormal work and even damage of other unit circuits in a system caused by serious voltage drop, and is a necessary component part particularly in communication equipment supporting hot plug, centralized power supply equipment and equipment or circuits needing midway starting work.

Therefore, domestic experts carry out deep research, and various types of power supply slow starting circuits are invented to meet the requirements of practical application. Document CN209001823U discloses a slow start circuit for power supply, which is composed of common components such as a resistor, a capacitor, and a switching tube, and has the advantage of low cost. Document CN101325411B discloses a dc power supply power-on slow start circuit, which adopts a switch protection circuit and a pre-charge circuit, and selects a resistance value, to solve the problems of easy damage of MOS transistors, hiccup phenomenon of the latter power supply, and unstable circuit reliability. Document CN101252309B discloses a dc power supply slow start control circuit, which achieves the purpose of slow start by making an insulated gate field effect transistor MOSFET as a transistor pass from a pinch-off region to an ohmic region through a constant current region, and adds a MOSFET gate charge fast discharge circuit, and the MOSFET is turned off quickly after power is turned off, so as to adapt to the environment of quick and frequent plugging. Document CN111355363A discloses a dc power supply slow start circuit, which can greatly improve the slow start time and effectively reduce the current impact by controlling a voltage regulator tube and a triode. Although the above documents have the advantages of low cost, simple circuit, and no need of software and hardware cooperation, if the conditions of overcurrent and short circuit occur, the slow start circuit may be damaged or the power supply of the system may be dragged down, and the stability and reliability of the system still need to be improved. Therefore, it is urgently needed to design a circuit which not only has a slow start function when power is on, but also has overcurrent and short-circuit protection.

SUMMERY OF THE UTILITY MODEL

Therefore, a dc power supply slow start circuit with a current-limiting function needs to be provided, so as to solve the problem that the existing slow start circuit cannot realize overcurrent and short-circuit protection.

In order to achieve the above object, the present invention provides a slow start circuit of a dc power supply with a current-limiting function, comprising a current detection unit, a comparison unit, a delay power-up unit and a switch unit, wherein a VIN terminal and a GND terminal are respectively an anode and a cathode of a power input terminal, a VOUT terminal and a GND1 terminal are respectively an anode and a cathode of a power output terminal, the input end of the delay power-on unit is connected with the VIN end, the output end of the delay power-on unit is connected with the in-phase end of the comparison unit, the current detection unit is respectively connected with the VIN end and the VOUT end, the current detection unit is used for detecting the current between the VIN end and the VOUT end and outputting detection voltage, the output end of the current detection unit is connected with the inverting end of the comparison unit, the output end of the comparison unit is connected with the input end of the switch unit, and the two output ends of the switch unit are respectively connected with a GND end and a GND1 end.

Further, the voltage conversion unit is further included, and the connection of the input end of the delay power-on unit to the VIN terminal specifically includes:

and the VIN end is connected with the input end of the voltage conversion unit, and the output end of the voltage conversion unit is connected with the input end of the time-delay electrifying unit.

Further, the voltage conversion unit is an LDO regulator U2.

Further, the current detection unit comprises a current detection amplifier U1, a resistor R5 and a resistor R1, two ends of the resistor R1 are respectively connected with the VIN end and the VOUT end, two input ends of the current detection amplifier U1 are respectively connected with two ends of the resistor R1, an output end of the current detection amplifier U1 is connected with one end of the resistor R5 and the inverting end of the comparison unit, and the other end of the resistor R5 is connected with the GND end.

Further, the comparing unit is an operational amplifier U3.

Further, the delay power-on unit comprises a resistor R3, a resistor R6, a potentiometer RP1 and a capacitor C4, one end of the resistor R3 is connected to the VIN end, the other end of the resistor R3 is connected to one end of the potentiometer RP1, the other end of the potentiometer RP1 is connected to one end of the resistor R6, the middle end of the potentiometer RP1 is connected to one end of the capacitor C4 and the same-phase end of the comparison unit, and the other end of the capacitor C4 and the other end of the resistor R6 are connected to the GND end.

Further, the switch unit is an N-channel field effect transistor Q1, and a gate of the N-channel field effect transistor Q1 is connected with the output end of the comparison unit; the source electrode of the N-channel field effect transistor Q1 is connected with the GND end; the drain of the N-channel field effect transistor Q1 is connected with the GND1 end.

Further, the device also comprises a voltage stabilizing diode D2, wherein the anode of the voltage stabilizing diode D2 is connected with the GND1 end, and the cathode of the voltage stabilizing diode D2 is connected with the gate of the N-channel field effect transistor Q1.

Furthermore, the N-channel FET Q1 further comprises a resistor R4, a capacitor C3 and a capacitor C5, two ends of the capacitor C5 are respectively connected with the gate and the source of the N-channel FET Q1, one end of the resistor R4 and one end of the capacitor C3 are connected with the output end of the comparison unit, and the other end of the resistor R4 and the other end of the capacitor C3 are connected with the gate of the N-channel FET Q1.

Further, the device also comprises a diode D1, wherein the cathode of the diode D1 is connected with the output end of the comparison unit, and the anode of the diode D1 is connected with the gate of the N-channel field effect transistor Q1.

The technical scheme is different from the prior art, the slow starting circuit consisting of the current detection unit, the delayed power-on unit and the comparison unit can gradually increase output current during power-on, reduce current impact, realize accurate control of the maximum output current, detect the magnitude of the current output current in real time, and perform quick response, so that device damage caused by overcurrent or short circuit of a load is prevented, the protection is more perfect, and the stability and reliability of the system can be improved.

Drawings

Fig. 1 is a circuit diagram of the present invention.

Description of reference numerals:

1. a current detection unit;

2. a comparison unit;

3. a delay power-on unit;

4. a switch unit;

5. a voltage conversion unit.

Detailed Description

To explain technical contents, structural features, and objects and effects of the technical solutions in detail, the following detailed description is given with reference to the accompanying drawings in conjunction with the embodiments.

Referring to fig. 1, the present embodiment provides a slow start circuit of a dc power supply with a current-limiting function, which includes a current detection unit 1, a comparison unit 2, a delay power-up unit 3 and a switch unit 4, wherein a VIN terminal and a GND terminal are a positive electrode and a negative electrode of a power input terminal, respectively, a VOUT terminal and a GND1 terminal are a positive electrode and a negative electrode of a power output terminal, the input end of the delay power-on unit is connected with the VIN end, the output end of the delay power-on unit is connected with the in-phase end of the comparison unit, the current detection unit is respectively connected with the VIN end and the VOUT end, the current detection unit is used for detecting the current between the VIN end and the VOUT end and outputting detection voltage, the output end of the current detection unit is connected with the inverting end of the comparison unit, the output end of the comparison unit is connected with the input end of the switch unit, and the two output ends of the switch unit are respectively connected with a GND end and a GND1 end.

When the delay electrifying unit works, after the VIN end is electrified, the voltage can be output from the output end after a period of time. The comparing unit may output a high voltage when the voltage of the non-inverting terminal is greater than that of the inverting terminal, thereby driving the switching unit to be turned on so that the GND terminal is conducted with the GND1 terminal. Therefore, the slow starting circuit consisting of the current detection unit, the delayed power-on unit and the comparison unit can not only gradually increase the output current and reduce the current impact during the power-on period, but also realize the accurate control of the maximum output current, detect the magnitude of the current output current in real time and make a quick response, prevent the damage of devices caused by overcurrent or short circuit of a load, ensure the protection to be more perfect and improve the stability and the reliability of the system.

Further, the voltage conversion unit 5 is further included, and the connection of the input end of the delay power-on unit to the VIN end specifically includes: and the VIN end is connected with the input end of the voltage conversion unit, and the output end of the voltage conversion unit is connected with the input end of the time-delay electrifying unit. The voltage stabilizing can be realized through the voltage conversion unit, the stable operation of the circuit is ensured, and the output end of the voltage conversion unit can be connected to the power supply end of the comparison unit. The capacitors C1 and C2 are power filter capacitors.

In a preferred embodiment, the voltage conversion unit is an LDO regulator U2.

As a preferred embodiment, the current detection unit includes a current detection amplifier U1, a resistor R5, and a resistor R1, two ends of the resistor R1 are respectively connected to the VIN terminal and the VOUT terminal, two input ends of the current detection amplifier U1 are respectively connected to two ends of the resistor R1, an output end of the current detection amplifier U1 is connected to one end of the resistor R5 and the inverting terminal of the comparison unit, and the other end of the resistor R5 is connected to the GND terminal. When the output current is small, the current output from the pin 3 by the current detection amplifier U1 is small, the voltage generated on the R5 is small, at this time, the in-phase end of the comparison unit (operational amplifier U3) is higher than the anti-phase end, the output is high level, and the switching unit (the gate of the field effect transistor Q1) obtains enough voltage to be completely switched on after being pulled up by the R2. When the output current is larger than the set current, the current output from the pin 3 by the current detection amplifier U1 is larger, the voltage generated on the resistor R5 is larger, at this time, the in-phase end of the operational amplifier U3 is lower than the anti-phase end, the output is low level, the grid of the field effect transistor Q1 is pulled low, the field effect transistor is in a temporary off state at this time, the output current is not switched on again until the output current is smaller than the set value, and the output of the operational amplifier U3 is changed into high level, so that the function of limiting the output current is realized. The resistor R1 is used as a sampling resistor and works in cooperation with the current sense amplifier U1, and the resistance value is usually selected milliohms.

As a preferred embodiment, the comparison unit is an operational amplifier U3.

As a preferred embodiment, the delay power-on unit includes a resistor R3, a resistor R6, a potentiometer RP1, and a capacitor C4, one end of the resistor R3 is connected to a VIN terminal, the other end of the resistor R3 is connected to one end of the potentiometer RP1, the other end of the potentiometer RP1 is connected to one end of the resistor R6, the middle end of the potentiometer RP1 is connected to one end of the capacitor C4 and the same-phase terminal of the comparison unit, and the other end of the capacitor C4 and the other end of the resistor R6 are connected to a GND terminal. In this embodiment, the power-on slow start function and the time duration are mainly composed of R3, RP1, R6, and C4, when power is turned on, the voltage of VIN or the voltage output by the voltage regulator U2 charges C4 through R3 and RP1, so that the voltage on C4 gradually rises, the voltage output by the operational amplifier U3 follows the rise, the gate-source voltage applied to the switching unit (N-channel fet Q1) gradually increases, and at this time, the switching unit (fet) can be equivalent to a variable resistor, so that the output current gradually increases, thereby preventing the impact of current, and particularly when the output terminal VOUT and GND1 are connected in parallel to a large-capacity capacitor, the effect is more obvious. By increasing or decreasing the capacity of C4, the time to soft start may be changed. Adjusting RP1 sets the output maximum current. In the embodiment having regulator U2 as the reference voltage, the set value is protected from the power supply voltage value within a certain range.

As a preferred embodiment, the switch unit is an N-channel fet Q1, and the gate of the N-channel fet Q1 is connected to the output terminal of the comparison unit; the source electrode of the N-channel field effect transistor Q1 is connected with the GND end; the drain of the N-channel field effect transistor Q1 is connected with the GND1 end. When the output of the comparison unit is low level, the grid of the field effect transistor Q1 is pulled low, and the field effect transistor processes a temporary closing state until the output current is less than a set value. When the output of the comparison unit becomes high level, the N-channel field effect transistor Q1 can be conducted again, so that the function of limiting the output current is realized.

Further, the device also comprises a voltage stabilizing diode D2, wherein the anode of the voltage stabilizing diode D2 is connected with the GND1 end, and the cathode of the voltage stabilizing diode D2 is connected with the gate of the N-channel field effect transistor Q1. The voltage stabilizing diode D2 is used for protecting the grid of the field effect transistor Q1 and preventing overvoltage breakdown.

Furthermore, the N-channel FET Q1 further comprises a resistor R4, a capacitor C3 and a capacitor C5, two ends of the capacitor C5 are respectively connected with the gate and the source of the N-channel FET Q1, one end of the resistor R4 and one end of the capacitor C3 are connected with the output end of the comparison unit, and the other end of the resistor R4 and the other end of the capacitor C3 are connected with the gate of the N-channel FET Q1. The self-excitation of the field effect transistor Q1 is prevented through the resistor R4, the capacitor C3 and the capacitor C5 in the circuit.

Further, the device also comprises a diode D1, wherein the cathode of the diode D1 is connected with the output end of the comparison unit, and the anode of the diode D1 is connected with the gate of the N-channel field effect transistor Q1. The diode D1 is used to let the output of the operational amplifier U3 output no current when high.

It should be noted that, although the above embodiments have been described herein, the utility model is not limited thereto. Therefore, based on the innovative concepts of the present invention, the technical solutions of the present invention can be directly or indirectly applied to other related technical fields by making changes and modifications to the embodiments described herein, or by using equivalent structures or equivalent processes performed in the content of the present specification and the attached drawings, which are included in the scope of the present patent.

Claims

1. The utility model provides a DC power supply slowly starts circuit with current-limiting function which characterized in that: including current detection unit, comparing element, time delay power on unit and switch element, VIN end and GND end are power input end positive pole and negative pole respectively, and VOUT end and GND1 end are power output end positive pole and negative pole respectively, VIN end is connected to the input of power on unit on the time delay, the output of power on unit is connected on the time delay the homophase end of comparing element, current detection unit is connected with VIN end and VOUT end respectively, current detection unit is used for detecting the electric current between VIN end and the VOUT end and exports detection voltage, current detection unit's output with comparing element's inverting terminal is connected, comparing element's output with switch element's input is connected, GND end and GND1 end are connected respectively to two output of switch element.

2. The slow start circuit of dc power supply with current limiting function as claimed in claim 1, wherein: the power supply circuit further comprises a voltage conversion unit, wherein the input end of the delay power-on unit is connected with the VIN end, and the voltage conversion unit specifically comprises the following steps:

3. The slow start circuit of dc power supply with current limiting function as claimed in claim 2, wherein: the voltage conversion unit is an LDO regulator U2.

4. The slow start circuit of dc power supply with current limiting function as claimed in claim 1, wherein: the current detection unit comprises a current detection amplifier U1, a resistor R5 and a resistor R1, wherein two ends of the resistor R1 are respectively connected with a VIN end and a VOUT end, two input ends of the current detection amplifier U1 are respectively connected with two ends of the resistor R1, an output end of the current detection amplifier U1 is connected with one end of the resistor R5 and an inverting end of the comparison unit, and the other end of the resistor R5 is connected with a GND end.

5. The slow start circuit of dc power supply with current limiting function as claimed in claim 1, wherein: the comparing unit is an operational amplifier U3.

6. The slow start circuit of dc power supply with current limiting function as claimed in claim 1, wherein: the delay power-on unit comprises a resistor R3, a resistor R6, a potentiometer RP1 and a capacitor C4, wherein one end of the resistor R3 is connected with a VIN end, the other end of the resistor R3 is connected with one end of the potentiometer RP1, the other end of the potentiometer RP1 is connected with one end of the resistor R6, the middle end of the potentiometer RP1 is connected with one end of the capacitor C4 and the same-phase end of the comparison unit, and the other end of the capacitor C4 and the other end of the resistor R6 are connected with a GND end.

7. The slow start circuit of dc power supply with current limiting function as claimed in claim 1, wherein: the switch unit is an N-channel field effect transistor Q1, and the grid electrode of the N-channel field effect transistor Q1 is connected with the output end of the comparison unit; the source electrode of the N-channel field effect transistor Q1 is connected with the GND end; the drain of the N-channel field effect transistor Q1 is connected with the GND1 end.

8. The slow start circuit of dc power supply with current limiting function as claimed in claim 7, wherein: the high-voltage power supply further comprises a voltage stabilizing diode D2, wherein the anode of the voltage stabilizing diode D2 is connected with the GND1 end, and the cathode of the voltage stabilizing diode D2 is connected with the grid electrode of the N-channel field effect transistor Q1.

9. The slow start circuit of dc power supply with current limiting function as claimed in claim 7, wherein: the N-channel FET Q1 circuit further comprises a resistor R4, a capacitor C3 and a capacitor C5, two ends of the capacitor C5 are respectively connected with the gate and the source of the N-channel FET Q1, one end of the resistor R4 and one end of the capacitor C3 are connected with the output end of the comparison unit, and the other end of the resistor R4 and the other end of the capacitor C3 are connected with the gate of the N-channel FET Q1.

10. The slow start circuit of dc power supply with current limiting function as claimed in claim 7, wherein: the comparator further comprises a diode D1, wherein the cathode of the diode D1 is connected with the output end of the comparison unit, and the anode of the diode D1 is connected with the gate of the N-channel field effect transistor Q1.