CN117748407A - Under-voltage protection circuit and device - Google Patents

Abstract

The invention provides an undervoltage protection circuit and a device, which belong to the technical field of hot plug protection chips and comprise: the device comprises a reference module, a voltage sampling module and a comparison module; a reference module configured to generate a reference voltage in response to a voltage output from the power supply and output the reference voltage to the first input terminal; the voltage sampling module is used for sampling the voltage output by the power supply and outputting the sampled voltage to the second input end; and a comparison module configured to generate a low level signal for pulling down the level of the enable pin to cut off a power supply loop between the power supply and the load when the reference voltage is greater than the sampling voltage in response to the arrival of the reference voltage and the sampling voltage. The undervoltage protection circuit provided by the invention can effectively cut off a power supply loop when the voltage output by a power supply is undervoltage while the enabling pin of the hot plug protection chip is controlled by the time sequence signal, so that the load is protected from being damaged.

Description

Under-voltage protection circuit and device

Technical Field

The invention belongs to the technical field of hot plug protection chips, and particularly relates to an undervoltage protection circuit and device.

Background

In the power supply design of the server, an input protection circuit is usually added at a position close to the input port, so that when the power supply is abnormal, electronic components on the protection board are not damaged. At present, the common input protection circuit mainly comprises a hot plug protection chip, and the undervoltage protection pins and the enabling pins of most hot plug protection chips are multiplexed, and the multiplexed pins can be used as an input undervoltage protection function when sampling input voltage. However, in most cases, the output voltage controlled by the hot-plug protection chip has a time sequence requirement, the enabling pin of the hot-plug protection chip needs to be connected to the singlechip, and the singlechip controls the establishment of the output voltage by controlling the enabling pin of the hot-plug protection chip, but in such cases, the hot-plug protection chip does not have an input under-voltage protection function.

In addition, the level conversion chip on the server main board does not have an input undervoltage protection function, if the power supply of the server main board is abnormal, the power supply voltage is lower, the corresponding power supply current is increased, the loss on the power supply link is increased, and the level conversion chip can not work normally, so that the server is abnormal in work.

Disclosure of Invention

In view of the foregoing, embodiments of the present application provide an undervoltage protection circuit and apparatus to overcome or at least partially solve the foregoing problems.

In a first aspect of the present embodiment, an undervoltage protection circuit is provided, connected between a power supply and a hot plug protection chip, and includes: the device comprises a reference module, a voltage sampling module and a comparison module;

the input end of the reference module and the input end of the voltage sampling module are connected with the power supply, the output end of the reference module is connected with the first input end of the comparison module, the output end of the voltage sampling module is connected with the second input end of the comparison module, and the output end of the comparison module and the singlechip share an enabling pin of the hot plug protection chip;

the reference module is configured to respond to the voltage output by the power supply, generate a reference voltage and output the reference voltage to the first input end;

the voltage sampling module is used for sampling the voltage output by the power supply and outputting the sampled voltage to the second input end;

the comparison module is configured to respond to the arrival of the reference voltage and the sampling voltage and generate a low-level signal when the reference voltage is larger than the sampling voltage, wherein the low-level signal is used for pulling down the level of the enabling pin so as to cut off a power supply loop between the power supply and a load;

And when the reference voltage is smaller than the sampling voltage, generating a high-level signal, wherein the high-level signal is used for keeping the level of the enabling pin unchanged so as to maintain the current conduction state of the power supply loop.

Further, the reference module includes: a triode, a zener diode and a first resistor; wherein,

the base electrode of the triode is respectively connected with the negative electrode of the voltage stabilizing diode and one end of the first resistor, the collector electrode of the triode is respectively connected with the positive electrode of the power supply and the other end of the first resistor, and the emitter electrode of the triode is connected with the first input end of the comparison module; the positive electrode of the voltage stabilizing diode is connected with the negative electrode of the power supply.

Further, the reference module further includes: a first capacitor; one end of the first capacitor is connected with the emitter of the triode, and the other end of the first capacitor is connected with the negative electrode of the power supply.

Further, the voltage sampling module includes: the second resistor and the third resistor; one end of the second resistor is connected with the positive electrode of the power supply, the other end of the second resistor is connected with one end of the third resistor and the second input end of the comparison module respectively, and the other end of the third resistor is grounded.

Further, the voltage sampling module further includes: a second capacitor; the second capacitor is connected in parallel with two ends of the third resistor.

Further, the comparison module includes: a comparator; the positive electrode of the comparator is connected with the voltage sampling module, the negative electrode of the comparator is connected with the output end of the reference module, and the output end of the comparator is connected with the enabling pin of the hot plug protection chip and the singlechip.

Further, the comparison module further includes: a fourth resistor; one end of the fourth resistor is connected with the positive electrode of the comparator, and the other end of the fourth resistor is connected with the output end of the comparator.

Further, the method further comprises the following steps: a pull-up resistor and a pull-up power supply; one end of the pull-up resistor is connected with the pull-up power supply, and the other end of the pull-up resistor is respectively connected with the output end of the comparison module and the singlechip.

Further, the method further comprises the following steps: a transient diode; wherein the reference module comprises: triode, zener diode, first resistance and first electric capacity, voltage sampling module includes: the second resistor, the third resistor and the second capacitor; wherein,

The positive electrode of the transient suppression diode is connected with the negative electrode of the power supply, and the negative electrode of the transient suppression diode is connected with the positive electrode of the power supply;

the base electrode of the triode is respectively connected with the negative electrode of the voltage stabilizing diode and one end of the first resistor, the collector electrode of the triode is respectively connected with the positive electrode of the power supply and the other end of the first resistor, and the emitter electrode of the triode is connected with the first input end of the comparison module; the positive electrode of the voltage stabilizing diode is connected with the negative electrode of the power supply, one end of the first capacitor is connected with the emitter of the triode, and the other end of the first capacitor is connected with the negative electrode of the power supply;

one end of the second resistor is connected with the positive electrode of the power supply, the other end of the second resistor is connected with one end of the third resistor and the second input end of the comparison module respectively, the other end of the third resistor is grounded, and the second capacitor is connected in parallel with the two ends of the third resistor.

In a second aspect of the embodiments of the present application, an under-voltage protection device is provided, where the under-voltage protection device includes an under-voltage protection circuit according to the first aspect of the embodiments of the present application.

The embodiment of the application provides an undervoltage protection circuit, which is connected between a power supply and a hot plug protection chip, and comprises: the device comprises a reference module, a voltage sampling module and a comparison module; the input end of the reference module and the input end of the voltage sampling module are connected with a power supply, the output end of the reference module is connected with the first input end of the comparison module, the output end of the voltage sampling module is connected with the second input end of the comparison module, and the output end of the comparison module shares an enabling pin of the hot plug protection chip with the singlechip; a reference module configured to generate a reference voltage in response to a voltage output from a power supply and output the reference voltage to a first input terminal; the voltage sampling module is used for sampling the voltage output by the power supply and outputting the sampled voltage to the second input end; a comparison module configured to generate a low level signal for pulling down the level of the enable pin to cut off a power supply loop between the power supply and the load when the reference voltage is greater than the sampling voltage in response to an arrival of the reference voltage and the sampling voltage; and when the reference voltage is smaller than the sampling voltage, generating a high-level signal, wherein the high-level signal is used for keeping the level of the enabling pin unchanged so as to maintain the current conduction state of the power supply loop.

The under-voltage protection circuit provided by the embodiment is connected between the power supply and the hot plug protection chip, the voltage output by the power supply can be sampled through the voltage sampling module in the under-voltage protection circuit, the sampled voltage is output to the second input end of the comparison module, and the reference voltage is generated to the first input end of the comparison module through the voltage output by the reference voltage response power supply.

Therefore, no matter whether the singlechip controls the enabling pin to conduct the power supply loop between the power supply and the load or not, when the low-level signal output by the comparison module acts on the enabling pin, the level of the enabling pin is pulled down so as to disconnect the power supply loop, so that the enabling pin of the hot plug protection chip can be controlled by a time sequence signal (controlled by the singlechip), and meanwhile, the power supply loop can be effectively cut off when the voltage output by the power supply is undervoltage, and the load (server) is protected from being damaged.

And under the condition that the enabling pin of the hot plug protection chip is being controlled by the time sequence signal, namely when the high-level signal output by the comparison module acts on the enabling pin, if the enabling pin of the hot plug protection chip is controlled by the time sequence signal to be turned off by the power supply loop at the moment, the current cut-off state of the power supply loop is not influenced by the high-level signal output by the comparison module.

In addition, the source of the reference voltage generated by the reference module is a power supply, so that the self-power supply of the comparison module is realized, and the dependence of the reference module on the standby power supply of the server is eliminated.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the description of the embodiments of the present application will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

FIG. 1 is a related art undervoltage protection circuit diagram provided by an embodiment of the present application;

FIG. 2 is a schematic diagram of an undervoltage protection circuit according to an embodiment of the present disclosure;

Fig. 3 is a schematic structural diagram of an undervoltage protection circuit according to an embodiment of the present disclosure;

FIG. 4 is a schematic diagram of an installation position of an undervoltage protection device according to an embodiment of the present disclosure;

description of the drawings:

100-a reference module; 200-a voltage sampling module; 300-a comparison module; 400-singlechip; 500-load; u1-hot plug protection chip; a U2-comparator; r1-a first resistor; r2-a second resistor; r3-a third resistor; r4-fourth resistor; r5-pull-up resistor; vin-power supply; vcc-pull-up power; q1-triode; d1-a zener transient diode; z1-zener diode; c1-a first capacitance; c2-a second capacitor C3-a third capacitor; c4-fourth capacitance; c5-fifth capacitance.

Detailed Description

Exemplary embodiments of the present application will be described in more detail below with reference to the accompanying drawings in the embodiments of the present application. While exemplary embodiments of the present application are shown in the drawings, it should be understood that the present application may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

Referring to fig. 1, fig. 1 is a schematic diagram of an undervoltage protection circuit according to the related art provided in an embodiment of the present application; the U1 in the figure 1 is a hot plug protection chip, wherein EN is an enabling pin, vin is an input end of the U1, the hot plug protection chip is connected with a power supply, the power supply is a direct-current voltage source of 12V, OUT is an output end of the U1, the power supply circuit between the power supply and the load is connected with a load (server), under normal conditions, the power supply is conducted by the U1, the power supply inputs voltage from the input end of the U1, the output end of the U1 is output to the load to supply power to the load, the enabling pin is connected with the output end of an under-voltage sampling circuit, the under-voltage sampling protection circuit in the figure 1 is formed by connecting a voltage dividing resistor R3 with a voltage dividing resistor R4 in series, one end of the voltage dividing resistor R3 in the under-voltage sampling protection circuit is connected with the power supply, and the other end of the voltage dividing resistor R3 is respectively connected with the voltage dividing resistor R4 and the enabling pin, and the other end of the voltage dividing resistor R4 is grounded.

The specific operation principle of the under-voltage sampling protection circuit in fig. 1 will be described in detail as follows:

firstly, when an input voltage Vin is normally established, an enable pin EN samples the input voltage through a voltage dividing resistor R3 and a voltage dividing resistor R4, when the sampled voltage reaches above an enable threshold voltage, a MOSFET (Metal-Oxide-semiconductor field-Effect Transistor) inside U1 starts to be turned on, so that a power supply loop between a power supply and a load is turned on, and at the moment, an output voltage Vout starts to increase and finally is stabilized near the input voltage Vin. The set-up time of the output voltage Vout is related to the capacitance of the SS pin capacitor Css of U1.

When the input voltage Vin is reduced due to failure, the voltage sampled by the EN pin of U1 is also reduced, when the voltage sampled by the enable pin EN is lower than the enable threshold voltage, the MOSFET inside U1 is turned off, the power supply loop is disconnected, and the corresponding input voltage is the input under-voltage protection voltage.

Although the undervoltage protection circuit of U1 in fig. 1 can realize that when the input voltage is too low, the power supply loop is cut off to protect the load, in the practical application process, except that the enable pin EN is connected with the output end of the undervoltage protection circuit, because the output voltage controlled by the hot plug protection chip has a time sequence requirement, the enable pin EN is also connected with the singlechip, when the connection with the singlechip is performed, the connection with the undervoltage protection circuit is disconnected, when the singlechip outputs a high level to the enable pin EN, the MOSFET in the U1 is also turned on, then the power supply loop is still turned on, then the function of the undervoltage protection circuit is lost, and when the enable pin EN is connected with the output end of the undervoltage sampling protection circuit, the power supply loop can be cut off only when the input voltage is detected to be lower than the enable threshold voltage, namely, the power supply loop can be used as the undervoltage protection function only when the input voltage is sampled. However, in some applications requiring power-on time sequence, the singlechip is required to control the power-on time sequence of the output voltage of the hot plug protection chip by controlling the enable signal of the hot plug protection chip, and at this time, the hot plug protection chip does not have the function of input under-voltage protection, and cannot rapidly and effectively cut off the power supply loop when the input voltage is under-voltage abnormal.

Therefore, the present application proposes an undervoltage protection circuit and device to solve the above-mentioned problems, and ensure that when the enable pin EN of the hot plug protection chip is occupied by the high level signal output by the single chip microcomputer, the connection of the undervoltage sampling protection circuit is not disconnected, the undervoltage protection function of the hot plug protection chip is still maintained, and meanwhile, the low level signal output by the single chip microcomputer is not acted on the enable pin of the hot plug protection chip, and interference is generated when the hot plug protection chip is controlled.

Referring to fig. 2, fig. 2 is a schematic block diagram of an under-voltage protection circuit according to an embodiment of the present application, as can be seen from the drawing, the under-voltage protection circuit is connected between a power source Vin and a hot plug protection chip U1, and the under-voltage protection circuit includes: a reference module 100, a voltage sampling module 200, and a comparison module 300;

the connection relationship among the reference module 100, the voltage sampling module 200, the comparison module 300, the hot plug protection chip U1 and the power supply is as follows: the input end of the reference module 100 and the input end of the voltage sampling module 200 are connected with a power Vin, the output end of the reference module 100 is connected with the first input end of the comparison module 300, the output end of the voltage sampling module 200 is connected with the second input end of the comparison module 300, and the output end of the comparison module 300 and the singlechip 400 share an enabling pin of the hot plug protection chip U1.

The reference module 100, the voltage sampling module 200 and the comparison module 300 are respectively configured with the following functions: a reference module 100 configured to generate a reference voltage in response to a voltage output from the power Vin and output the reference voltage to a first input terminal; the voltage sampling module 200 is configured to sample a voltage output by the power Vin and output the sampled voltage to the second input terminal; a comparison module 300 configured to compare the reference voltage with the sampling voltage, and generate a low level signal for pulling down the level of the enable pin to cut off the power supply loop between the power Vin and the load 500 when the reference voltage is greater than the sampling voltage; and when the reference voltage is smaller than the sampling voltage, generating a high-level signal, wherein the high-level signal is used for keeping the level of the enabling pin unchanged so as to maintain the current conduction state of the power supply loop.

In this embodiment, the reference module 100 is a reference circuit that generates a stable reference voltage by performing a step-down process on the power output voltage, where the stable reference voltage is a voltage value corresponding to the reference voltage output by the reference circuit, which is maintained when the power output voltage is in an undervoltage state. Since the reference voltage is used to provide the voltage value representing that the voltage output by the power Vin is not in the under-voltage state to the comparison module 300, and further, since the reference module 100 needs to supply power to the comparison module 300, the value of the reference voltage can be reasonably selected according to the power supply voltage requirement of the comparison module 300, and if the power supply voltage requirement of the comparison module is 3.3V, the reference voltage can be set to be 3.3V.

The voltage sampling module 200 is a sampling circuit that performs voltage division sampling on the voltage output from the power supply and outputs a sampled voltage that matches the operating range of the voltage sampling module. Since the sampled voltage is used for reflecting whether the voltage output by the current power supply Vin is in the voltage value of the under-voltage state, as can be seen from fig. 1, whether the voltage value output by the under-voltage sampling protection circuit in fig. 1 is larger than the enabling threshold value is compared to determine whether the voltage output by the power supply Vin is in the under-voltage state at this time, so that the sampled voltage obtained by the sampling circuit can be larger than the threshold voltage according to the fact that the sampled voltage is smaller than the threshold voltage when the voltage output by the power supply Vin is in the under-voltage state.

In addition, since the sampling circuit performs voltage division sampling on the voltage output by the power supply, the sampled voltage is reduced to be within the working range suitable for the sampling circuit, damage to the sampling circuit and generation of measurement errors can be avoided, and meanwhile, the situation that the voltage output by the power supply Vin is directly output to the comparison module 300, so that the comparison module 300 is damaged due to overlarge input voltage is avoided.

The comparing module 300 is a comparing circuit for comparing the sampled voltage output by the voltage sampling module 200 with the reference voltage output by the reference module 100, and the comparing module 300 is used for controlling whether the MOSFET inside the hot plug protection chip U1 is turned on or not by the comparing module 300 and the single chip 400 in the comparing process if the reference voltage is larger than the comparing voltage, and the output end of the comparing module 300 shares the enabling pin of the hot plug protection chip U1 with the single chip 400, so that the enabling pin of the hot plug protection chip U1 is controlled by the high level signal or the low level signal output by the output end of the comparing module 300, and the high level signal or the low level signal output by the single chip 400 is controlled by the comparing module 300 and the single chip 400, so that the on state of the power supply loop between the power Vin and the load 500 is controlled.

Therefore, when the single-chip microcomputer 400 controls the MOSFET inside the hot plug protection chip U1 to be turned on, the power supply loop is in a turned-on state, if the input voltage of the power Vin is reduced at this time, the sampling voltage collected by the voltage sampling module 200 is reduced, when the sampling voltage is output to the comparison module 300 for comparison, and is smaller than the reference voltage input to the comparison module 300, the comparison module 300 outputs a low-level signal to the enable pin of the hot plug protection chip U1 at this time, even if the power supply loop is turned on due to the high-level signal output by the single-chip microcomputer 400 at this time, the level of the enable pin is also pulled down when the low-level signal output by the comparison module 300 reaches the enable pin, and at this time, the MOSFET inside the hot plug protection chip U1 is turned off, thereby cutting off the power supply loop between the power Vin and the load 500.

In addition, when the comparison module 300 outputs a high level signal to the enable pin of the hot plug protection chip U1, if the power supply loop is in a conductive state, the level of the enable pin is kept unchanged. If the enable pin is at a low level due to the action of the single-chip microcomputer 400, the high level signal output by the comparison module 300 is pulled down by the low level signal output by the single-chip microcomputer 400 to maintain the current state of the power supply loop even if the high level signal acts on the enable pin.

The under-voltage protection circuit provided by the embodiment is connected between the power Vin and the hot plug protection chip U1, and can sample the voltage output by the power Vin through the voltage sampling module 200 in the under-voltage protection circuit and output the sampled voltage to the second input end of the comparison module 300, and generate the reference voltage to the first input end of the comparison module 300 through the voltage output by the reference voltage in response to the power Vin.

Therefore, whether the singlechip 400 controls the enable pin to conduct the power supply loop between the power Vin and the load 500 at this time, when the low-level signal output by the comparison module 300 acts on the enable pin, the level signal at the enable pin is pulled down to disconnect the power supply loop, so that the enable pin of the hot-plug protection chip U1 can be controlled by the timing signal (controlled by the singlechip 400), and meanwhile, the power supply loop can be effectively cut off when the voltage output by the power Vin is under-voltage, thereby protecting the load 500 (server) from being damaged.

And when the enabling pin of the hot plug protection chip U1 is controlled by the time sequence signal and the comparison module outputs a high-level signal to act on the enabling pin, the current conduction state of the power supply loop is not affected no matter whether the enabling pin of the hot plug protection chip U1 is controlled by the time sequence signal to be conducted or cut off by the power supply loop.

In addition, since the source of the reference voltage generated by the reference module 100 is the power Vin, self-power supply of the comparison module 300 is realized, and the reference module 100 is free from the dependence on the server standby power Vin.

In one embodiment, the reference module 100 includes: triode Q1, zener diode Z1 and first resistor R1; the base electrode of the triode Q1 is respectively connected with the negative electrode of the zener diode Z1 and one end of the first resistor R1, the collector electrode of the triode Q1 is respectively connected with the positive electrode of the power supply Vin and the other end of the first resistor R1, and the emitter electrode of the triode Q1 is connected with the first input end of the comparison module 300; the positive electrode of the voltage stabilizing diode Z1 is connected with the negative electrode of the power supply Vin.

In this embodiment, referring to fig. 3, fig. 3 is a schematic structural diagram of an undervoltage protection circuit provided in this embodiment, and as can be seen from fig. 3, a reference module 100 includes: the triode Q1, the zener diode Z1 and the first resistor R1 have better linearity and temperature stability, so that the triode Q1 can output stable reference voltage to the first input end of the comparison module 300 by connecting the collector of the triode Q1 with the Positive electrode of the power Vin and the emitter of the triode Q1 with the first input end of the comparison module 300, in addition, as can be seen from FIG. 3, the triode Q1 is of the NPN (Negative-Positive-Negative) type, because of the conduction characteristic of the NPN triode Q1, the triode Q1 is conducted only when the voltage between the base and the emitter is Positive and exceeds a certain critical value (generally 0.6-0.7V), because one end of the first resistor R1 is connected with the base of the triode Q1, the other end of the first resistor R1 is connected with the collector of the triode Q1, in order to ensure the conduction of the triode Q1, the base of the triode Q1 is connected with a voltage stabilizing diode Z1, the Negative electrode of the voltage stabilizing diode Z1 is connected with the base of the triode Q1, and the Positive electrode of the voltage stabilizing diode Z1 is connected with the Negative electrode of the power supply Vin, when the power supply voltage input by the power supply Vin gradually rises to the working voltage of the voltage stabilizing diode Z1, the voltage stabilizing diode Z1 starts to have current flow through the two ends of the first resistor R1 to generate left, right and left Negative voltages, the emitter junction of the NPN triode Q1 is positively biased, the collector of the triode Q1 is reversely biased, the conduction condition of the NPN transistor is met, so that the reference voltage output by the emitter of the triode Q1 is a stable reference voltage, even when the voltage output by the power supply is in an undervoltage state, the voltage output by the emitter of the triode Q1 can be maintained to be a stable reference voltage.

In one embodiment, the reference module 100 further comprises: a first capacitor C1; one end of the first capacitor C1 is connected to the emitter of the triode Q1, and the other end of the first capacitor C1 is connected to the negative electrode of the power source Vin.

In this embodiment, with continued reference to fig. 3, the reference module 100 further includes: and a first capacitor C1, wherein one end of the first capacitor C1 is connected to the emitter of the triode Q1, and the other end of the first capacitor C1 is connected to the negative electrode of the power source Vin, so that the capacitor can filter the reference voltage output from the emitter to the first input end of the comparison module 300 according to the characteristic of the capacitor that prevents direct current from passing and allows alternating current to pass.

In addition, the reference module 100 may be another power module, for example: the buck power supply directly outputs a voltage value meeting the power supply voltage requirement of the comparison module 300 to the comparison module 300.

In one embodiment, the voltage sampling module 200 includes: the second resistor R2 and the third resistor R3; one end of the second resistor R2 is connected to the positive electrode of the power source Vin, the other end of the second resistor R2 is connected to one end of the third resistor R3 and the second input end of the comparison module 300, and the other end of the third resistor R3 is grounded.

In this embodiment, referring to fig. 3, the voltage sampling module 200 includes a second resistor R2 and a third resistor R3, where one end of the second resistor R2 is connected to the positive electrode of the power source Vin, the other end of the second resistor R2 is connected to one end of the third resistor R3 and the second input end of the comparison module 300, and the other end of the third resistor R3 is grounded, as shown in fig. 3, the second resistor R2 and the third resistor R3 are connected in series to form a voltage dividing circuit, so that the voltage output by the power source Vin can be divided, and the voltage output by the power source Vin can be reduced to be within a working range suitable for the sampling circuit by setting the resistance values of the second resistor R2 and the third resistor R3.

In one embodiment, the voltage sampling module 200 further comprises: a second capacitor C2; the second capacitor C2 is connected in parallel to two ends of the third resistor R3.

In this embodiment, referring to fig. 3, the voltage sampling module 200 further includes: the second capacitor C2 is connected in parallel to two ends of the third resistor R3, so that the second resistor R2 and the third resistor R3 form a sampling circuit, the collected sampling voltage is slower than the reference voltage generated by the reference module 100, and it is ensured that the reference voltage is stably input to the comparison module 300 when the comparison module 300 compares the sampling voltage, so that the comparison result output by the comparison module 300 is more accurate, and in addition, the second capacitor C2 can also filter the sampling voltage output by the sampling circuit to remove interference of noise.

In one embodiment, the comparison module 300 includes: a comparator U2; the positive electrode of the comparator U2 is connected with the voltage sampling module 200, the negative electrode of the comparator U2 is connected with the output end of the reference module 100, and the output end of the comparator U2 is connected with the enabling pin of the hot plug protection chip U1 and the singlechip 400.

In this embodiment, referring to fig. 3, the comparison module 300 is a comparator U2, and the comparator U2 includes a positive electrode and a negative electrode, where it is to be noted that the positive electrode and the negative electrode of the comparator U2 are both input to the comparator U2, and have no other physical meaning, and the positive electrode and the negative electrode only distinguish sources of two input voltages, and because the comparison module 300 and the singlechip 400 share an enable pin of the hot-plug protection chip U1, the output end of the comparator U2 needs to be connected with the enable pin of the hot-plug protection chip U1 and the singlechip 400.

In one embodiment, the comparison module 300 further comprises: a fourth resistor R4; one end of the fourth resistor R4 is connected to the positive electrode of the comparator U2, and the other end of the fourth resistor R4 is connected to the output end of the comparator U2.

In this embodiment, referring to fig. 3, the comparing module 300 further includes a fourth resistor R4, since one end of the fourth resistor R4 is connected to the positive electrode of the comparator U2, and the other end of the fourth resistor R4 is connected to the output end of the comparator U2, the comparator U2 is used to invert the output signal by comparing the level of the positive and negative input ends, and due to the addition of the fourth resistor R4, when the output signal of the comparator U2 is changed from high level to low level, the corresponding power supply voltage is smaller than the corresponding power supply voltage when the low level is changed from low level to high level, and at this time, a voltage hysteresis design is realized, so that when the comparator U2 compares the reference voltage with the sampling voltage, it can effectively prevent the input undervoltage from being mistakenly protected when the power supply Vin has small fluctuation, and the power supply loop is cut off.

In one embodiment, the undervoltage protection circuit further comprises: pull-up resistor R5 and pull-up power supply Vcc; one end of the pull-up resistor R5 is connected to the pull-up power Vcc, and the other end of the pull-up resistor R5 is connected to the output end of the comparison module 300 and the single chip 400, respectively.

In this embodiment, referring to fig. 3, the undervoltage protection circuit in this embodiment further includes a pull-up resistor R5 and a pull-up power supply Vcc, and since the comparator U2 only determines the magnitudes of the sampling voltage and the reference voltage, the output signal needs to be pulled up to the pull-up power supply Vcc through the pull-up resistor R5 because the output of the comparator U2 is an open-drain output. Therefore, when the sampling voltage is greater than the reference voltage, for the comparator U2, the output transistor is turned off, and since one end of the pull-up resistor R5 is connected to the pull-up power supply Vcc, and the other end of the pull-up resistor R5 is connected to the output end of the comparison module 300 and the singlechip 400, the voltage output by the pull-up power supply Vcc will pass through the pull-up resistor R5 to the enable pin, i.e. the output end of the comparator U2 outputs a high-level signal to the enable pin of the hot plug chip.

When the sampling voltage is smaller than the reference voltage, for the comparator U2, the output transistor is turned on to output a low level, and at this time, the voltage output by the pull-up power supply Vcc will be pulled down by the low level signal output by the comparator U2 through the pull-up resistor R5 to the comparator U2, that is, the output end of the comparator U2 outputs the low level signal to the enable pin of the hot plug chip, and at this time, even if the singlechip 400 outputs the high level signal to the enable pin, the low level signal output by the comparator U2 will be pulled down.

In one embodiment, the undervoltage protection circuit further comprises: a transient suppression diode; wherein the reference module 100 includes: triode Q1, zener diode Z1, first resistance R1 and first electric capacity C1, voltage sampling module 200 includes: the second resistor R2, the third resistor R3 and the second capacitor C2; the positive electrode of the transient suppression diode is connected with the negative electrode of the power supply Vin, and the negative electrode of the transient suppression diode is connected with the positive electrode of the power supply Vin; the base electrode of the triode Q1 is respectively connected with the negative electrode of the voltage stabilizing diode Z1 and one end of the first resistor R1, the collector electrode of the triode Q1 is respectively connected with the positive electrode of the power supply Vin and the other end of the first resistor R1, and the emitter electrode of the triode Q1 is connected with the first input end of the comparison module 300; the positive electrode of the voltage stabilizing diode Z1 is connected with the negative electrode of the power supply Vin, one end of the first capacitor C1 is connected with the emitter of the triode Q1, and the other end of the first capacitor C1 is connected with the negative electrode of the power supply Vin; one end of the second resistor R2 is connected with the positive electrode of the power Vin, the other end of the second resistor R2 is connected with one end of the third resistor R3 and the second input end of the comparison module 300, the other end of the third resistor R3 is grounded, and the second capacitor C2 is connected in parallel with two ends of the third resistor R3.

In this embodiment, the undervoltage protection circuit further includes a transient suppression diode, an anode of the transient suppression diode is connected to a cathode of the power source Vin, and a cathode of the transient suppression diode is connected to an anode of the power source Vin, and the transient direct-current diode is used for stabilizing the output voltage of the power source Vin, so as to avoid breakdown of the hot plug protection chip U1 caused by overlarge voltage (i.e., peak voltage of the power source Vin) output by the power source Vin, and each electronic component in the undervoltage protection circuit.

Also because the reference module 100 includes: triode Q1, zener diode Z1, first resistance R1 and first electric capacity C1, voltage sampling module 200 includes: the base electrode of the triode Q1 is respectively connected with the cathode of the voltage stabilizing diode Z1 and one end of the first resistor R1, the collector electrode of the triode Q1 is respectively connected with the anode of the power Vin and the other end of the first resistor R1, and the emitter electrode of the triode Q1 is connected with the first input end of the comparison module 300; the positive electrode of the voltage stabilizing diode Z1 is connected with the negative electrode of the power supply Vin, one end of the first capacitor C1 is connected with the emitter of the triode Q1, and the other end of the first capacitor C1 is connected with the negative electrode of the power supply Vin; one end of the second resistor R2 is connected with the positive electrode of the power source Vin, the other end of the second resistor R2 is connected with one end of the third resistor R3 and the second input end of the comparison module 300 respectively, the other end of the third resistor R3 is grounded, and the second capacitor C2 is connected in parallel with the two ends of the third resistor R3. In the process of using the undervoltage protection circuit, the voltage output by the power Vin can be ensured to be stable, the reference voltage output by the reference module 100 can be ensured to be stable, the sampling voltage output by the voltage sampling module 200 can be ensured to be stable, so that the comparison module 300 can more accurately judge the sizes of the reference voltage and the sampling voltage, and finally, an accurate high-level signal or low-level signal is output to act on the enabling pin.

As an example, referring to fig. 3, it will be understood from fig. 3 that the reference module 100 is formed by a first resistor R1, a triode Q1, a zener diode Z1 and a first capacitor C1; the voltage sampling module 200 is formed by a second resistor R2, a third resistor R3 and a second capacitor C2; the comparator U2 and the fourth resistor R4 form the comparison module 300, and include the power supply Vcc and the pull-up resistor R5, so as to describe in detail the use process of the undervoltage protection circuit of the present embodiment:

the reference voltage is Vref, the sampling voltage is Vin_sample, U1 is a hot plug protection chip, U2 is a comparator, and EN is an enabling pin of the hot plug protection chip.

The SS pin of the U1 is connected to the third capacitor C3, the other end of the third capacitor C3 is connected to the negative electrode of the power supply, the Vcc pin of the U1 is connected to the fourth capacitor C4, the other end of the fourth capacitor C4 is connected to the negative electrode of the power supply, the Vout pin of the U1 is connected to the fifth capacitor C5, and the other end of the fifth capacitor C5 is connected to the negative electrode of the power supply.

Therefore, when the power supply voltage Vin gradually rises to the working voltage of the zener diode Z1, a current starts to flow through Z1, a voltage of positive left and negative right is generated at two ends of the resistor R4, the emitter junction of the NPN transistor Q1 is forward biased, the collector of the NPN transistor Q1 is reverse biased, the conduction condition of the NPN transistor is satisfied, Q1 starts to work, and the emitter starts to output the voltage Vref, vref as the power supply voltage and the reference voltage of the comparator U2; because of the capacitor C1, the rising speed of the sampling voltage vin_sample is slower than the voltage Vref, and the output signal of the comparator U1 is at a low level, i.e., the EN signal of the comparator U2 is at a low level. Vin continues to rise, the internal voltage source Vcc of the hot plug protection chip U2 is established, and U1 has no output voltage because the EN signal of U1 is at a low level. When Vin rises to the second resistor R2 and the third resistor R3 to obtain the sampling voltage vin_sample > Vref, the open-drain structure at the output end of the comparator U1 releases the EN signal, and the EN pin of the U2 is also connected to the singlechip, so that the singlechip can pull the EN signal down before the singlechip controls the output voltage of the U2 to be established, and the U1 has no output voltage.

According to the power-on time sequence requirement, when the output voltage of the U1 is built, the singlechip controls the EN signal of the U1 to be released, the EN signal is pulled up by the voltage Vcc, the hot plug protection chip U1 is enabled to enable the internal MOSFET to be conducted, the output voltage Vout of the U1 is built, and the rising time of the Vout is related to the capacitance value of the third capacitor C3; the above process is a process of normally establishing an output voltage for the input protection circuit. When the power voltage Vin is lower due to abnormal conditions and the sampling voltage vin_sample is less than Vref, the comparator U2 outputs a low-level signal, namely the EN signal of U1 is pulled down, the MOSFET in U1 is cut off, and the power supply loop is disconnected, so that the purpose of input under-voltage protection is achieved.

In addition, the input undervoltage detection circuit adopts a voltage hysteresis design, namely a fourth resistor, the fourth resistor is connected in parallel between the positive electrode and the output end of the comparator U2, and when the output of the comparator U2 is turned from low to high, the calculation formula of the corresponding sampling voltage vin_sample_rise is as follows:

when the comparator U2 output toggles from high to low, the corresponding sampling voltage vin_sample_fall is calculated as follows:

therefore, after the power supply voltage of the power supply Vin is established, a certain margin is reserved for voltage fluctuation output by the power supply Vin, and under-voltage protection is not triggered by mistake when the voltage output by the power supply Vin fluctuates, so that a power supply loop is disconnected.

Based on the same inventive concept, the present embodiment also provides an under-voltage protection device, which includes the under-voltage protection circuit as in the above embodiment.

Referring to fig. 4, fig. 4 is a schematic diagram of an installation position of an undervoltage protection device provided in an embodiment of the present application, which may be specifically installed on a server motherboard and connected to a power connector and a hot plug protection chip, so that input undervoltage protection to the hot plug chip may be implemented, thereby implementing input protection to a load.

In this specification, each embodiment is described in a progressive manner, and each embodiment is mainly described by differences from other embodiments, and identical and similar parts between the embodiments are all enough to be referred to each other.

Embodiments of the invention are described with reference to flowchart illustrations and/or block diagrams of circuits, devices, and/or embodiments of the invention. It will be understood that each flowchart and/or block of the flowchart illustrations and/or block diagrams, and combinations of flowcharts and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing terminal device to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing terminal device, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.

While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. It is therefore intended that the following claims be interpreted as including the preferred embodiment and all such alterations and modifications as fall within the scope of the embodiments of the invention.

Finally, it is further noted that relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or terminal that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or terminal. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article or terminal device comprising the element.

The above description of the undervoltage protection circuit and the device provided by the invention applies specific examples to illustrate the principle and the implementation of the invention, and the above examples are only used for helping to understand the method and the core idea of the invention; meanwhile, as those skilled in the art will have variations in the specific embodiments and application scope in accordance with the ideas of the present invention, the present description should not be construed as limiting the present invention in view of the above.

Claims (10)

1. An undervoltage protection circuit connected between a power supply and a hot plug protection chip, comprising: the device comprises a reference module, a voltage sampling module and a comparison module;

the input end of the reference module and the input end of the voltage sampling module are connected with the power supply, the output end of the reference module is connected with the first input end of the comparison module, the output end of the voltage sampling module is connected with the second input end of the comparison module, and the output end of the comparison module and the singlechip share an enabling pin of the hot plug protection chip;

the reference module is configured to respond to the voltage output by the power supply, generate a reference voltage and output the reference voltage to the first input end;

The voltage sampling module is used for sampling the voltage output by the power supply and outputting the sampled voltage to the second input end;

the comparison module is configured to respond to the arrival of the reference voltage and the sampling voltage and generate a low-level signal when the reference voltage is larger than the sampling voltage, wherein the low-level signal is used for pulling down the level of the enabling pin so as to cut off a power supply loop between the power supply and a load;

and when the reference voltage is smaller than the sampling voltage, generating a high-level signal, wherein the high-level signal is used for keeping the level of the enabling pin unchanged so as to maintain the current conduction state of the power supply loop.

2. The undervoltage protection circuit of claim 1, wherein the reference module comprises: a triode, a zener diode and a first resistor; wherein,

the base electrode of the triode is respectively connected with the negative electrode of the voltage stabilizing diode and one end of the first resistor, the collector electrode of the triode is respectively connected with the positive electrode of the power supply and the other end of the first resistor, and the emitter electrode of the triode is connected with the first input end of the comparison module; the positive electrode of the voltage stabilizing diode is connected with the negative electrode of the power supply.

3. The undervoltage protection circuit of claim 2, wherein the reference module further comprises: a first capacitor; one end of the first capacitor is connected with the emitter of the triode, and the other end of the first capacitor is connected with the negative electrode of the power supply.

4. The undervoltage protection circuit of claim 1, wherein the voltage sampling module comprises: the second resistor and the third resistor; one end of the second resistor is connected with the positive electrode of the power supply, the other end of the second resistor is connected with one end of the third resistor and the second input end of the comparison module respectively, and the other end of the third resistor is grounded.

5. The undervoltage protection circuit of claim 4, wherein the voltage sampling module further comprises: a second capacitor; the second capacitor is connected in parallel with two ends of the third resistor.

6. The undervoltage protection circuit of claim 1, wherein the comparison module comprises: a comparator; the positive electrode of the comparator is connected with the voltage sampling module, the negative electrode of the comparator is connected with the output end of the reference module, and the output end of the comparator is connected with the enabling pin of the hot plug protection chip and the singlechip.

7. The undervoltage protection circuit of claim 6, wherein the comparison module further comprises: a fourth resistor; one end of the fourth resistor is connected with the positive electrode of the comparator, and the other end of the fourth resistor is connected with the output end of the comparator.

8. The undervoltage protection circuit of claim 1, further comprising: a pull-up resistor and a pull-up power supply; one end of the pull-up resistor is connected with the pull-up power supply, and the other end of the pull-up resistor is respectively connected with the output end of the comparison module and the singlechip.

9. The undervoltage protection circuit of claim 1, further comprising: a transient diode; wherein the reference module comprises: triode, zener diode, first resistance and first electric capacity, voltage sampling module includes: the second resistor, the third resistor and the second capacitor; wherein,

the positive electrode of the transient suppression diode is connected with the negative electrode of the power supply, and the negative electrode of the transient suppression diode is connected with the positive electrode of the power supply;

the base electrode of the triode is respectively connected with the negative electrode of the voltage stabilizing diode and one end of the first resistor, the collector electrode of the triode is respectively connected with the positive electrode of the power supply and the other end of the first resistor, and the emitter electrode of the triode is connected with the first input end of the comparison module; the positive electrode of the voltage stabilizing diode is connected with the negative electrode of the power supply, one end of the first capacitor is connected with the emitter of the triode, and the other end of the first capacitor is connected with the negative electrode of the power supply;

One end of the second resistor is connected with the positive electrode of the power supply, the other end of the second resistor is connected with one end of the third resistor and the second input end of the comparison module respectively, the other end of the third resistor is grounded, and the second capacitor is connected in parallel with the two ends of the third resistor.

10. An undervoltage protection device comprising an undervoltage protection circuit as claimed in any one of claims 1 to 9.