Slow start circuit and daughter card

Abstract

The utility model provides a slow start circuit and a daughter card, and relates to the daughter card integrated circuit technology field, the circuit comprises a slow start sub-circuit, a thermal protection circuit, an overcurrent protection circuit and a switch circuit, the overcurrent protection circuit is connected with the slow start sub-circuit, the thermal protection circuit and the switch circuit, and the thermal protection circuit is connected with the switch circuit. The slow start sub-circuit is also connected with the thermal protection circuit and the switching circuit, and the thermal protection circuit is also connected with the switching circuit; the slow start sub-circuit is used for controlling the switch circuit to be slowly switched on based on the slowly increased capacitor charging voltage under the condition that the overcurrent protection circuit is connected with the backboard so as to realize slow start; the thermal protection circuit is used for controlling the switching circuit to be switched off slowly based on the increase of the heat of the switching circuit under the condition that the overcurrent protection circuit is connected with the backboard; the overcurrent protection circuit is used for generating a comparison control signal. According to the utility model, the slow start function, the thermal protection function and the over-current protection function of the daughter card can be considered.

Description

TECHNICAL FIELD

[0001] The utility model relates to the technical field of daughter card integrated circuit, especially relates to a slow start circuit and daughter card. BACKGROUND

[0002] In the frame equipment of multiple daughter cards such as video input and output daughter card of the control product, all require that the daughter card supports hot plug function. The power slow start circuit needs to be designed to realize the hot plug function of the daughter card, to prevent the large fluctuation of instantaneous voltage from causing the host computer to hang or the abnormal power-on of the daughter card when the daughter card is inserted. At the same time, when the daughter card power overflows or is short-circuited, the daughter card power should also be turned off in time to avoid the device from hanging due to the instantaneous pull-down of the host power.

[0003] In the prior art, a special slow start protection chip or a MOS (Metal-Oxide-Semiconductor Field-Effect Transistor) discrete device is generally used to realize the slow start function. However, the special slow start protection chip cannot realize the thermal protection function of the external MOS tube, and the MOS discrete device cannot realize the overcurrent protection function and the thermal protection function. Therefore, how to consider the slow start function, the thermal protection function and the overcurrent protection function of the daughter card is a problem to be solved at present. UTILITY MODEL CONTENTS

[0004] The utility model provides a slow start circuit and daughter card to solve the defects that the slow start function, the thermal protection function and the overcurrent protection function of the daughter card cannot be considered in the prior art.

[0005] The utility model provides a slow start circuit, which comprises a slow start subcircuit, a thermal protection circuit, an overcurrent protection circuit and a switching circuit, wherein:

[0006] The overcurrent protection circuit is connected with the slow start subcircuit, the thermal protection circuit and the switching circuit, the slow start subcircuit is also connected with the thermal protection circuit and the switching circuit, and the thermal protection circuit is also connected with the switching circuit;

[0007] The slow start subcircuit is used to control the slow conduction of the switching circuit based on the slow increase of the capacitor charging voltage when the overcurrent protection circuit is connected with the backboard, so as to realize slow start;

[0008] The thermal protection circuit is used to control the slow turn-off of the switching circuit based on the increase of the heat of the switching circuit when the overcurrent protection circuit is connected with the backboard;

[0009] The overcurrent protection circuit is used to generate a comparison control signal, and the comparison control signal is used to control the on-off state of the slow start subcircuit to control the on-off state of the switching circuit.

[0010] According to the slow start circuit provided by the utility model, the slow start sub-circuit comprises a capacitor C1, a resistor R1 and a triode Q1, wherein:

[0011] The first end of the capacitor C1 is connected with the second end of the overcurrent protection circuit, the first end of the thermal protection circuit and the first end of the switch circuit, the second end of the capacitor C1 is connected with the first end of the resistor R1, the second end of the thermal protection circuit and the second end of the switch circuit, the second end of the resistor R1 is connected with the collector of the triode Q1, the base of the triode Q1 is connected with the third end of the overcurrent protection circuit, and the emitter of the triode Q1 is grounded;

[0012] The base of the triode Q1 is used for receiving the comparison control signal generated by the overcurrent protection circuit, and the backboard is used for charging the capacitor C1;

[0013] The capacitor charging voltage slowly increasing at both ends of the capacitor C1 is used for slowly increasing the opening voltage of the switch circuit under the condition that the triode Q1 is turned on under the control of the comparison control signal, and the slowly increasing opening voltage is used for controlling the slow turn-on of the switch circuit.

[0014] According to the slow start circuit provided by the utility model, the thermal protection circuit comprises a negative temperature coefficient resistor, the first end of the negative temperature coefficient resistor serves as the first end of the thermal protection circuit, the second end of the negative temperature coefficient resistor serves as the second end of the thermal protection circuit, and the resistance value of the negative temperature coefficient resistor is negatively correlated with the heat of the switch circuit.

[0015] According to the slow start circuit provided by the utility model, the overcurrent protection circuit comprises a positive temperature coefficient resistor and a comparison circuit, wherein:

[0016] The first end of the positive temperature coefficient resistor is connected with the first end of the comparison circuit and serves as the first end of the overcurrent protection circuit, the second end of the positive temperature coefficient resistor is connected with the second end of the comparison circuit and serves as the second end of the overcurrent protection circuit, the third end of the comparison circuit serves as the third end of the overcurrent protection circuit, the fourth end of the comparison circuit is grounded and serves as the fourth end of the overcurrent protection circuit;

[0017] The resistance value of the positive temperature coefficient resistor is positively correlated with the current flowing therethrough, and the comparison circuit is used for generating the comparison control signal.

[0018] According to the slow start circuit provided by the utility model, the comparison circuit comprises a first voltage dividing circuit, a second voltage dividing circuit and a comparator, wherein:

[0019] The first end of the first voltage dividing circuit is the first end of the comparison circuit, the second end of the first voltage dividing circuit is connected to the negative input end of the comparator, the third end of the first voltage dividing circuit is connected to the third end of the second voltage dividing circuit, and is the fourth end of the comparison circuit;

[0020] The first end of the second voltage dividing circuit is the second end of the comparison circuit, the second end of the second voltage dividing circuit is connected to the positive input end of the comparator, and the output end of the comparator is the third end of the comparison circuit.

[0021] The first voltage dividing circuit is used for generating a reference voltage, the second voltage dividing circuit is used for generating a positive voltage after the positive temperature coefficient resistor, and the comparator is used for generating the comparison control signal based on a comparison result of the reference voltage and the positive voltage.

[0022] According to the slow start circuit, the first voltage dividing circuit comprises a resistor R2, a capacitor C2 and a voltage stabilizing tube Z1, wherein:

[0023] The capacitor C2 and the voltage stabilizing tube Z1 are connected in parallel, and are connected in series with the resistor R2 after being connected in parallel; and the voltage stabilizing tube Z1 is used for generating a reference voltage.

[0024] According to the slow start circuit, the second voltage dividing circuit comprises a resistor R3 and a resistor R4, and the resistor R3 and the resistor R4 are connected in series.

[0025] According to the slow start circuit, the switching circuit comprises a MOS tube Q2 and a resistor R5, the source of the MOS tube Q2 is the first end of the switching circuit, the gate of the MOS tube Q2 is connected to the first end of the resistor R5, the second end of the resistor R5 is the second end of the switching circuit, the drain of the MOS tube Q2 is connected to one end of a filter capacitor C3, and is the third end of the switching circuit, and the other end of the filter capacitor C3 is grounded.

[0026] According to the slow start circuit, the overcurrent protection circuit further comprises a TVS Z2, the first end of the TVS Z2 is connected to the first end of the positive temperature coefficient resistor, and the second end of the TVS Z2 is grounded.

[0027] The utility model also provides a daughter card which comprises the slow start circuit according to any one of the preceding embodiments.

[0028] The slow start circuit and the daughter card provided by the utility model, in the case of connecting the backboard with the overcurrent protection circuit, the power output end in the backboard slowly increases the capacitor charging voltage in the slow start sub-circuit, controls the slow conduction of the switch circuit, and realizes the slow start. BRIEF DESCRIPTION OF DRAWINGS

[0029] In order to more clearly illustrate the technical scheme in the utility model or the prior art, the following will briefly introduce the drawings needed to be used in the embodiment or the prior art description, and obviously, the following description of the drawings is some embodiments of the utility model, and for those skilled in the art, other drawings can also be obtained according to these drawings without creative labor.

[0030] Figure 1 It is one of the structure schematic diagrams of the slow start circuit provided by the prior art.

[0031] Figure 2 It is the second structure schematic diagram of the slow start circuit provided by the prior art.

[0032] Figure 3 It is the structure schematic diagram of the slow start circuit provided by the embodiment of the utility model.

[0033] Figure 4 It is the connection schematic diagram of the slow start sub-circuit provided by the embodiment of the utility model.

[0034] Figure 5 It is one of the schematic diagrams of parameter change provided by the embodiment of the utility model.

[0035] Figure 6 It is the second schematic diagram of parameter change provided by the embodiment of the utility model.

[0036] Figure 7 It is the connection schematic diagram of the overcurrent protection circuit provided by the embodiment of the utility model.

[0037] Figure 8 It is the third schematic diagram of parameter change provided by the embodiment of the utility model.

[0038] Figure 9 It is the circuit schematic diagram of the overcurrent protection circuit provided by the embodiment of the utility model.

[0039] REFERENCE SIGNS:

[0040] 110: overcurrent protection circuit; 111: comparison circuit; 1111: first voltage dividing circuit; 1112: second voltage dividing circuit; 120: thermal protection circuit; 130: soft start sub-circuit; 140: switching circuit; 200: backplane. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical scheme and advantages of the utility model more clear, the technical scheme in the utility model will be described clearly and completely below in combination with the drawings in the utility model. Obviously, the described embodiments are part of the embodiments of the utility model, rather than all the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the utility model.

[0042] In the prior art, Figure 1 is one of the structure diagrams of the soft start circuit provided by the prior art, as shown in Figure 1 In the soft start circuit composed of the special soft start protection chip, after the daughter card is inserted into the backplane, the special soft start protection chip can control the gate voltage, slowly turn on the external MOS (Metal-Oxide-Semiconductor Field-Effect Transistor) tube P1, make the daughter card output end slowly output, and realize the effect of soft start. At the same time, the overcurrent protection function is integrated in the special soft start protection chip, which can judge whether the daughter card overflows through the current size of the MOS tube P1, and realize the overcurrent protection of the daughter card. However, the special soft start protection chip cannot realize the thermal protection function of the MOS tube P1, and the cost of the special soft start protection chip is relatively high.

[0043] In addition, Figure 2 is the second structure diagram of the soft start circuit provided by the prior art, as shown in Figure 2 In the soft start circuit composed of discrete devices, after the daughter card is inserted into the backplane, due to the instantaneous charging of the capacitor C1, the gate-source voltage VGS of the MOS tube P2 gradually increases, the MOS tube P2 is slowly turned on, and the power supply hot plug function of the daughter card is realized. At the same time, when the daughter card overflows, the fuse can realize the short circuit protection of the daughter card and the host. However, the overcurrent protection function and the thermal protection function of the MOS tube P2 cannot be realized.

[0044] In view of the problem that the prior art cannot consider the soft start function, the thermal protection function and the overcurrent protection function, the utility model embodiment provides a soft start circuit, Figure 3 is the structure diagram of the soft start circuit provided by the utility model embodiment, as shown in Figure 3As shown, the soft start circuit includes a soft starter circuit 130, a thermal protection circuit 120, an overcurrent protection circuit 110 and a switch circuit 140.

[0045] The overcurrent protection circuit 110 is connected to the soft starter circuit 130, the thermal protection circuit 120 and the switch circuit 140, the soft starter circuit 130 is further connected to the thermal protection circuit 120 and the switch circuit 140, and the thermal protection circuit 120 is further connected to the switch circuit 140.

[0046] The soft starter circuit 130 is configured to control the switch circuit 140 to slowly turn on based on a slowly increasing capacitor charging voltage, so as to achieve soft start, when the overcurrent protection circuit 110 is connected to the backboard 200.

[0047] The thermal protection circuit 120 is configured to control the switch circuit 140 to slowly turn off based on an increase in heat of the switch circuit 140, when the overcurrent protection circuit 110 is connected to the backboard 200.

[0048] The overcurrent protection circuit 110 is configured to generate a comparison control signal for controlling the on-off state of the soft starter circuit 130, so as to control the on-off state of the switch circuit 140.

[0049] Specifically, the soft start circuit is integrated in the daughter card, and after the daughter card is inserted into the backboard 200, the first end of the overcurrent protection circuit 110 is connected to the power output end of the backboard 200. The overcurrent protection circuit 110 is used to generate a comparison control signal, and the level state of the comparison control signal is used to represent whether the daughter card is overcurrent. For example, when the comparison control signal is a high-level signal, it indicates that the daughter card is not overcurrent, and when the comparison control signal is a low-level signal, it indicates that the daughter card is overcurrent. Through the level state of the comparison control signal, the on-off state of the soft start sub-circuit 130 can be controlled. For example, when the comparison control signal is a high-level signal, the soft start sub-circuit 130 can be controlled to be turned on, and when the comparison control signal is a low-level signal, the soft start sub-circuit 130 can be controlled to be turned off. When the comparison control signal controls the soft start sub-circuit 130 to be turned on, the power input end of the backboard 200 slowly increases the capacitor charging voltage in the soft start sub-circuit 130, so that the turn-on voltage in the switching circuit 140 slowly increases, and the switching circuit 140 slowly turns on along with the slow increase of the turn-on voltage, realizes the soft start, and the power output end of the backboard 200 realizes slow output. After the switching circuit 140 is turned on, if the current flowing through the switching circuit 140 is large or the environmental temperature is too high, along with the gradual accumulation of heat in the switching circuit 140, the thermal protection circuit 120 can control the turn-on voltage in the switching circuit 140 to gradually decrease, control the switching circuit 140 to slowly turn off, avoid damage of the switching circuit 140 due to overheating, and realize thermal protection. In the case that the soft start sub-circuit 130 is in the turned-on state, the power output end in the backboard 200 slowly increases the capacitor charging voltage in the soft start sub-circuit 130, controls the switching circuit 140 to slowly turn on, and realizes the soft start. At the same time, along with the increase of heat in the switching circuit 140, the thermal protection circuit 120 can gradually control the switching circuit 140 to slowly turn off, to avoid damage of the switching circuit 140 due to overheating. When the daughter card is overcurrent, the overcurrent protection circuit 110 controls the soft start sub-circuit 130 to be turned off, decreases the turn-on voltage of the switching circuit 140, and then controls the switching circuit 140 to be turned off, to realize overcurrent protection. Based on this, the embodiments of the present application can take into account the soft start function, the thermal protection function and the overcurrent protection function of the daughter card, and the circuit cost is relatively low.

[0050] Optionally, the power output end of the backboard 200 can output direct current, and the output voltage can be 12V or 24V, etc., and the embodiments of the present application do not limit this.

[0051] Further, Figure 4 is a connection diagram of the soft start sub-circuit 130 provided by the embodiments of the present application, as shown in the figure, Figure 4 The soft start sub-circuit 130 includes a capacitor C1, a resistor R1 and a triode Q1.

[0052] The first end of the capacitor C1 is connected to the second end of the overcurrent protection circuit 110, the first end of the thermal protection circuit 120 and the first end of the switch circuit 140, the second end of the capacitor C1 is connected to the first end of the resistor R1, the second end of the thermal protection circuit 120 and the second end of the switch circuit 140, the second end of the resistor R1 is connected to the collector of the triode Q1, the base of the triode Q1 is connected to the third end of the overcurrent protection circuit 110, and the emitter of the triode Q1 is grounded.

[0053] The base of the triode Q1 is used to receive the comparison control signal generated by the overcurrent protection circuit 110, and the backboard 200 is used to charge the capacitor C1.

[0054] The slowly increasing capacitor charging voltage across the capacitor C1 is used to slowly increase the turn-on voltage of the switch circuit 140 when the triode Q1 is turned on under the control of the comparison control signal, and the slowly increasing turn-on voltage is used to control the slow turn-on of the switch circuit 140.

[0055] Specifically, at the initial moment when the daughter card is inserted into the backboard 200, the turn-on voltage of the switch circuit 140 approaches 0V, so that the switch circuit 140 is in an off state, and at this time the output end of the daughter card has no output. Then, with the comparison control signal output by the overcurrent protection circuit 110 as a high level signal, the slow start sub-circuit 130 is controlled to be turned on. That is, the comparison control signal as a high level signal increases the base voltage of the triode Q1, thereby controlling the triode Q1 to be turned on, and further realizing the turn-on of the slow start sub-circuit 130, that is, the turn-on of the path composed of the capacitor C1, the resistor R1 and the triode Q1. After the slow start sub-circuit 130 is turned on, the power output end of the backboard 200 charges the capacitor C1, and the resistor R1 performs voltage division. With the slow increase of the capacitor charging voltage across the capacitor C1, the turn-on voltage in the switch circuit 140 slowly increases, and the switch circuit 140 slowly turns on with the slow increase of the turn-on voltage, realizing slow start, and finally realizing the slow output of the power output end of the backboard 200.

[0056] Further, as shown in Figure 4 The switch circuit 140 includes a MOS tube Q2 and a resistor R5, the source of the MOS tube Q2 serves as the first end of the switch circuit 140, the gate of the MOS tube Q2 is connected to the first end of the resistor R5, the second end of the resistor R5 serves as the second end of the switch circuit 140, the drain of the MOS tube Q2 is connected to one end of a filter capacitor C3 and serves as the third end of the switch circuit 140, and the other end of the filter capacitor C3 is grounded.

[0057] Specifically, the turn-on voltage of the switch circuit 140 refers to the gate-source voltage VGS of the MOS tube Q2, that is, the voltage difference between the gate voltage and the source voltage of the MOS tube Q2. The drain of the MOS tube Q2 serves as the output end of the sub-card. Figure 5 is one of the schematic diagrams of parameter changes provided by the embodiment of the utility model, as shown in the figure, Figure 5 After the over-current protection circuit 110 controls the slow start sub-circuit 130 to turn on, the gate-source voltage VGS of the MOS tube Q2 gradually increases with the slow increase of the capacitor charging voltage at both ends of the capacitor C1, so as to control the slow turn-on of the MOS tube Q2, realize the slow turn-on of the switch circuit 140, and then realize the gradual increase of the output voltage. After the switch circuit 140 turns on, the filter capacitor C3 filters the output voltage DC12V of the power output end of the backboard 200.

[0058] It should be noted that in the embodiment of the utility model, the gate-source voltage VGS of the MOS tube Q2 is negative with the slow increase of the source voltage of the MOS tube Q2. The gate-source voltage VGS of the MOS tube Q2 is inversely increased, that is, the gate-source voltage VGS of the MOS tube Q2 gradually deviates from 0V.

[0059] Further, as shown in the figure, Figure 4 The heat protection circuit 120 includes a negative temperature coefficient resistor RT1, the first end of the negative temperature coefficient resistor RT1 serves as the first end of the heat protection circuit 120, the second end of the negative temperature coefficient resistor RT1 serves as the second end of the heat protection circuit 120, and the resistance value of the negative temperature coefficient resistor RT1 is negatively correlated with the heat of the switch circuit 140.

[0060] Specifically, the heat of the switch circuit 140 refers to the accumulated heat of the MOS tube Q2. The negative temperature coefficient resistor RT1 is a thermistor, and the resistance value of the negative temperature coefficient resistor RT1 decreases with the increase of the perceived heat. Figure 6 is the second schematic diagram of parameter changes provided by the embodiment of the utility model, as shown in the figure, Figure 6 After the switch circuit 140 turns on, the output end of the sub-card maintains output. If the current flowing through the switch circuit 140 is large or the environmental temperature is too high, the heat of the MOS tube Q2 gradually increases. The negative temperature coefficient resistor RT1 is arranged near the MOS tube Q2, and the resistance value of the negative temperature coefficient resistor RT1 gradually decreases with the gradual increase of the heat of the MOS tube Q2. The gate-source voltage VGS of the MOS tube Q2 also gradually decreases in the opposite direction, that is, the gate-source voltage VGS of the MOS tube Q2 gradually approaches 0V. The MOS tube Q2 gradually turns off, and the output end of the sub-card also gradually turns off.

[0061] Further, Figure 7is a connection diagram of the overcurrent protection circuit 110 provided by the embodiment of the utility model, as shown in the drawing, Figure 7 The overcurrent protection circuit 110 includes a positive temperature coefficient resistance RT2 and a comparison circuit 111, wherein:

[0062] The first end of the positive temperature coefficient resistance RT2 is connected with the first end of the comparison circuit 111, and serves as the first end of the overcurrent protection circuit 110; the second end of the positive temperature coefficient resistance RT2 is connected with the second end of the comparison circuit 111, and serves as the second end of the overcurrent protection circuit 110; the third end of the comparison circuit 111 serves as the third end of the overcurrent protection circuit 110; and the fourth end of the comparison circuit 111 is grounded and serves as the fourth end of the overcurrent protection circuit 110.

[0063] The resistance value of the positive temperature coefficient resistance RT2 is positively correlated with the current flowing therethrough; and the comparison circuit 111 is used for generating the comparison control signal.

[0064] It should be noted that the positive temperature coefficient resistance RT2 is a thermistor, and the resistance value of the positive temperature coefficient resistance RT2 increases with the increase of the perceived heat.

[0065] Further, the comparison circuit 111 includes a first voltage dividing circuit 1111, a second voltage dividing circuit 1112 and a comparator, wherein:

[0066] The first end of the first voltage dividing circuit 1111 serves as the first end of the comparison circuit 111; the second end of the first voltage dividing circuit 1111 is connected with the negative input end of the comparator; and the third end of the first voltage dividing circuit 1111 is connected with the third end of the second voltage dividing circuit 1112 and serves as the fourth end of the comparison circuit 111.

[0067] The first end of the second voltage dividing circuit 1112 serves as the second end of the comparison circuit 111; the second end of the second voltage dividing circuit 1112 is connected with the positive input end of the comparator; and the output end of the comparator serves as the third end of the comparison circuit 111.

[0068] The first voltage dividing circuit 1111 is used for generating a reference voltage; the second voltage dividing circuit 1112 is used for generating a positive voltage division after the positive temperature coefficient resistance RT2; and the comparator is used for generating the comparison control signal based on the comparison result of the reference voltage and the positive voltage division.

[0069] It should be noted that the characteristics of the comparator are that when the voltage at the positive input end is higher than the voltage at the negative input end, the comparator outputs a high level signal; otherwise, when the voltage at the positive input end is lower than the voltage at the negative input end, the comparator outputs a low level signal.

[0070] Specifically, at the initial moment when the daughter card is inserted into the back panel 200, the current flowing through the positive temperature coefficient resistor RT2 is small, and the resistance of the positive temperature coefficient resistor RT2 is small. That is, the voltage drop across the positive temperature coefficient resistor RT2 is small, which makes the voltage drop across the second voltage divider circuit 1112 larger. Consequently, the positive voltage drop in the second voltage divider circuit 1112 is greater than the reference voltage in the first voltage divider circuit 1111. Based on the characteristics of the comparator, the positive voltage at the positive input terminal of the comparator is greater than the reference voltage at the negative input terminal. At this time, the comparator outputs a high-level signal, which can control the transistor Q1 in the soft-start sub-circuit 130 to turn on, thereby controlling the soft-start sub-circuit 130 to turn on. Figure 8 This is the third schematic diagram of parameter changes provided in this embodiment of the utility model, as shown below. Figure 8 As shown, after the switching circuit 140 is turned on, if the current flowing through the positive temperature coefficient resistor RT2 is large, the resistance of the positive temperature coefficient resistor RT2 will gradually increase, thereby gradually increasing the voltage division across the positive temperature coefficient resistor RT2, and causing the voltage division across the second voltage divider circuit 1112 to gradually decrease. When the positive voltage division in the second voltage divider circuit 1112 decreases to less than the reference voltage in the first voltage divider circuit 1111, the comparator outputs a low-level control signal. This low-level signal can control the transistor Q1 in the soft-start sub-circuit 130 to turn off. At the same time, the gate-source voltage VGS of the MOSFET Q2 in the switching circuit 140 gradually decreases to 0V, thereby controlling the MOSFET Q2 to turn off, and the power output terminal of the backplane 200 stops outputting, realizing the overcurrent protection of the daughter card.

[0071] Furthermore, Figure 9 This is a circuit diagram of the overcurrent protection circuit 110 provided in this embodiment of the present invention, as shown below. Figure 9 As shown, the first voltage divider circuit 1111 includes a resistor R2, a capacitor C2, and a Zener diode Z1, wherein:

[0072] The capacitor C2 is connected in parallel with the Zener diode Z1, and after being connected in parallel, it is connected in series with the resistor R2; the Zener diode Z1 is used to generate a reference voltage.

[0073] Specifically, in the first voltage divider circuit 1111, the connection point of resistor R2 and capacitor C2 is connected to the negative input terminal of the comparator. That is, the voltage divider formed by resistor R2 and capacitor C2 generates a reference voltage, which can be the voltage across capacitor C2. It should be noted that since a Zener diode Z1 is connected in parallel across capacitor C2, the voltage across capacitor C2 is equal to the voltage across Zener diode Z1. Zener diode Z1 can maintain a constant voltage level through its own regulation, thereby stabilizing the voltage across capacitor C2, i.e., generating a stable reference voltage.

[0074] It should be noted that the voltage value of the reference voltage can be set by selecting different device parameters of the voltage stabilizing tube, and the reference voltage can be set to 5V, and the embodiments of the present application do not limit this.

[0075] Further, as shown in Figure 9 The second voltage dividing circuit 1112 includes resistors R3 and R4, and the resistors R3 and R4 are connected in series.

[0076] Specifically, the connection point of the resistors R3 and R4 in the second voltage dividing circuit 1112 is connected to the positive input terminal of the comparator, that is, the resistors R3 and R4 generate a positive voltage after dividing the voltage across the second voltage dividing circuit 1112.

[0077] Further, as shown in Figure 9 The overcurrent protection circuit 110 further includes a TVS (Transient Voltage Suppressor) Z2, a first end of the TVS Z2 is connected to a first end of the positive temperature coefficient resistor RT2, and a second end of the TVS Z2 is grounded.

[0078] Specifically, when the subcard is overvoltage, the TVS Z2 can quickly conduct and guide the excess voltage to the ground, avoiding damage to sensitive devices and semiconductor elements in the slow start circuit.

[0079] The slow start circuit provided by the embodiments of the present application, in the case of connecting the backboard to the overcurrent protection circuit, the power output end in the backboard slowly increases the capacitor charging voltage in the slow start subcircuit, controls the slow conduction of the switching circuit, and realizes the slow start. At the same time, with the increase of the heat of the switching circuit, the thermal protection circuit can gradually control the slow turn-off of the switching circuit, avoiding damage caused by overheating of the switching circuit. When the subcard is overcurrent, the overcurrent protection circuit controls the turn-off of the slow start subcircuit, and then controls the turn-off of the switching circuit, realizing the overcurrent protection.

[0080] The embodiments of the present application also provide a board card, which comprises the slow start circuit according to any one of the above.

[0081] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, but not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement to part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A soft-start circuit, characterized in that, include: The circuit includes a soft-start sub-circuit, a thermal protection circuit, an overcurrent protection circuit, and a switching circuit, among which: The overcurrent protection circuit is connected to the soft start sub-circuit, the thermal protection circuit, and the switching circuit. The soft start sub-circuit is also connected to the thermal protection circuit and the switching circuit. The thermal protection circuit is also connected to the switching circuit. The soft-start sub-circuit is used to control the switching circuit to slowly turn on based on the slowly increasing capacitor charging voltage when the overcurrent protection circuit is connected to the backplane, thereby achieving a soft start. The thermal protection circuit is used to control the switching circuit to slowly turn off based on the increase in heat of the switching circuit when the overcurrent protection circuit is connected to the backplane. The overcurrent protection circuit is used to generate a comparison control signal, which is used to control the on / off state of the soft-start sub-circuit, thereby controlling the on / off state of the switching circuit.

2. The soft-start circuit according to claim 1, characterized in that, The soft-start sub-circuit includes capacitor C1, resistor R1, and transistor Q1, wherein: The first terminal of capacitor C1 is connected to the second terminal of the overcurrent protection circuit, the first terminal of the thermal protection circuit, and the first terminal of the switching circuit. The second terminal of capacitor C1 is connected to the first terminal of resistor R1, the second terminal of the thermal protection circuit, and the second terminal of the switching circuit. The second terminal of resistor R1 is connected to the collector of transistor Q1. The base of transistor Q1 is connected to the third terminal of the overcurrent protection circuit. The emitter of transistor Q1 is grounded. The base of transistor Q1 is used to receive the comparison control signal generated by the overcurrent protection circuit; the backplate is used to charge capacitor C1. The capacitor charging voltage that slowly increases across capacitor C1 is used to slowly increase the turn-on voltage of the switching circuit when the transistor Q1 is turned on by the comparison control signal. The slowly increasing turn-on voltage is used to control the switching circuit to turn on slowly.

3. The soft-start circuit according to claim 1, characterized in that, The thermal protection circuit includes a negative temperature coefficient resistor. The first end of the negative temperature coefficient resistor serves as the first end of the thermal protection circuit, and the second end of the negative temperature coefficient resistor serves as the second end of the thermal protection circuit. The resistance value of the negative temperature coefficient resistor is negatively correlated with the heat of the switching circuit.

4. The soft-start circuit according to claim 1, characterized in that, The overcurrent protection circuit includes a positive temperature coefficient resistor and a comparator circuit, wherein: The first end of the positive temperature coefficient resistor is connected to the first end of the comparator circuit and serves as the first end of the overcurrent protection circuit. The second end of the positive temperature coefficient resistor is connected to the second end of the comparator circuit and serves as the second end of the overcurrent protection circuit. The third end of the comparator circuit serves as the third end of the overcurrent protection circuit. The fourth end of the comparator circuit is grounded and serves as the fourth end of the overcurrent protection circuit. The resistance value of the positive temperature coefficient resistor is positively correlated with the current flowing through it; the comparison circuit is used to generate the comparison control signal.

5. The soft-start circuit according to claim 4, characterized in that, The comparison circuit includes a first voltage divider circuit, a second voltage divider circuit, and a comparator, wherein: The first terminal of the first voltage divider circuit serves as the first terminal of the comparator circuit, the second terminal of the first voltage divider circuit is connected to the negative input terminal of the comparator, and the third terminal of the first voltage divider circuit is connected to the third terminal of the second voltage divider circuit and serves as the fourth terminal of the comparator circuit. The first terminal of the second voltage divider circuit serves as the second terminal of the comparator circuit, the second terminal of the second voltage divider circuit is connected to the positive input terminal of the comparator, and the output terminal of the comparator serves as the third terminal of the comparator circuit. The first voltage divider circuit is used to generate a reference voltage, the second voltage divider circuit is used to generate a positive voltage divider after the positive temperature coefficient resistor, and the comparator is used to generate a comparison control signal based on the comparison result of the reference voltage and the positive voltage divider.

6. The soft-start circuit according to claim 5, characterized in that, The first voltage divider circuit includes a resistor R2, a capacitor C2, and a Zener diode Z1, wherein: The capacitor C2 is connected in parallel with the Zener diode Z1, and after being connected in parallel, it is connected in series with the resistor R2; the Zener diode Z1 is used to generate a reference voltage.

7. The soft-start circuit according to claim 5, characterized in that, The second voltage divider circuit includes resistors R3 and R4, which are connected in series.

8. The soft-start circuit according to any one of claims 2-7, characterized in that, The switching circuit includes a MOSFET Q2 and a resistor R5. The source of the MOSFET Q2 serves as the first terminal of the switching circuit. The gate of the MOSFET Q2 is connected to the first terminal of the resistor R5. The second terminal of the resistor R5 serves as the second terminal of the switching circuit. The drain of the MOSFET Q2 is connected to one end of a filter capacitor C3 and serves as the third terminal of the switching circuit. The other end of the filter capacitor C3 is grounded.

9. The soft-start circuit according to any one of claims 4-7, characterized in that, The overcurrent protection circuit also includes a TVS Z2, the first end of which is connected to the first end of the positive temperature coefficient resistor, and the second end of the TVS Z2 is grounded.

10. A daughter card, characterized in that, Includes the soft-start circuit as described in any one of claims 1-9.

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