A kind of intrinsically safe power supply protection circuit and method for improving the load capacity of intrinsically safe power supply

Abstract

The embodiments of this specification disclose an intrinsically safe power supply protection circuit and a method for improving the load capacity of an intrinsically safe power supply. The protection circuit includes: a filter module, a comparison control module, a current sampling circuit, a fast delay circuit, a fast protection switch unit, a slow delay circuit, and a slow protection switch unit; wherein the filter module is used to eliminate low-frequency harmonics and high-frequency harmonics formed after the load is connected; the comparison control module is used to provide a fast protection action comparison voltage and a slow protection action comparison voltage; the current sampling circuit is used to generate a differential amplified voltage difference for the output current of the intrinsically safe circuit; the fast delay circuit provides a current limiting delay and a current limiting holding time for delaying a short-circuit protection control signal; the slow delay circuit provides an overcurrent delay and an overcurrent holding time for delaying an overcurrent protection control signal.

Description

Technical Field

[0001] The present invention relates to the field of intrinsically safe power supplies, and in particular to an intrinsically safe power supply protection circuit and a method for improving the load capacity of an intrinsically safe power supply. Background Art

[0002] Intrinsically safe power supplies are referred to as "intrinsically safe power supplies" and are mainly used in environments containing explosive gases such as petroleum, chemical industry, and coal as power supply equipment for communications, monitoring, detection, and control systems. In order to prevent sparks generated by output overcurrent or load short circuit from igniting flammable and explosive gases, intrinsically safe power supplies must use protection circuits to limit the energy of sparks.

[0003] At present, the working modes of the energy-limiting protection circuit for achieving intrinsic safety performance of intrinsically safe power supply include: direct switch off mode, linear voltage regulation plus switch off mode and hierarchical protection mode. The existing energy-limiting protection circuit of intrinsically safe power supply has low output power and poor anti-interference ability due to limiting the spark energy.

[0004] Therefore, a method is needed to effectively solve the problem that the output power of the intrinsically safe power supply is low and the anti-interference ability is poor due to limiting the spark energy, and to improve the output power of the intrinsically safe power supply, so that the intrinsically safe power supply can be widely used. Summary of the invention

[0005] The embodiments of this specification provide an intrinsically safe power supply protection circuit and a method for improving the load capacity of an intrinsically safe power supply, which are used to solve the following technical problems: the existing energy-limiting protection circuits of intrinsically safe power supplies cannot effectively solve the output problem of the intrinsically safe power supply, and the output power of the intrinsically safe power supply is not high.

[0006] To solve the above technical problems, the embodiments of this specification are implemented as follows:

[0007] An intrinsically safe power supply protection circuit provided in an embodiment of the present specification includes:

[0008] Filter module, comparison control module, current sampling circuit, fast delay circuit, fast protection switch unit, slow delay circuit, slow protection switch unit;

[0009] in,

[0010] The filtering module is used to eliminate low-frequency harmonics and high-frequency harmonics generated after the load is connected;

[0011] The comparison control module is used to provide a fast protection action comparison voltage and a slow protection action comparison voltage;

[0012] The current sampling circuit is used to generate a differentially amplified voltage difference from the output current of the intrinsically safe circuit;

[0013] The fast delay circuit is used for current limiting delay and current limiting holding time;

[0014] The slow delay circuit is used for overcurrent delay and overcurrent holding time.

[0015] A method for improving the load capacity of an intrinsically safe power supply provided in an embodiment of this specification includes:

[0016] Determine the loop current consisting of the intrinsically safe power supply and any of the protection circuits described above;

[0017] When the loop current is greater than a preset short-circuit protection setting value, a protection action is generated based on the protection circuit;

[0018] Detecting the output current of the protection action;

[0019] If the output current of the protection action is greater than the preset overcurrent action value, the loop formed by the intrinsically safe power supply and the protection circuit is cut off;

[0020] If the output current of the protection action is not greater than the preset overcurrent action value, the loop composed of the intrinsically safe power supply and the protection circuit supplies power to the load normally.

[0021] At least one of the above technical solutions adopted in the embodiments of this specification can achieve the following beneficial effects: the protection circuit provided in the embodiments of this specification does not require a heat sink, is small in size, and is inexpensive and highly reliable. The method for improving the load capacity of an intrinsically safe power supply provided in the embodiments of this specification can significantly improve the output power of the intrinsically safe power supply, improve the anti-interference ability of the intrinsically safe power supply when the output is close to the rated rate, and avoid the restart phenomenon caused by the protection action when the load current is close to the rated output current due to small fluctuations in the current, and the intrinsically safe power supply has low power consumption and high efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of this specification or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this specification. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0023] Figure 1 A schematic diagram of an intrinsically safe power supply protection circuit provided in an embodiment of this specification;

[0024] Figure 2 The structural intention of an intrinsically safe power supply protection circuit provided in the embodiments of this specification;

[0025] Figure 3A schematic diagram of the delay protection provided in the embodiments of this specification;

[0026] Figure 4 A discharge schematic diagram provided for the embodiments of this specification;

[0027] Figure 5 The voltage waveforms and output current waveforms at various points during the overcurrent protection provided in the embodiments of this specification;

[0028] Figure 6 A schematic diagram of a method for improving the load capacity of an intrinsically safe power supply provided in an embodiment of this specification;

[0029] Figure 7 The short protection action waveform diagram provided in the embodiment of this specification when the current surge current duration is short;

[0030] Figure 8 This is a short-circuit protection action waveform diagram when a short-circuit fault persists provided in an embodiment of this specification. DETAILED DESCRIPTION

[0031] In order to enable those skilled in the art to better understand the technical solutions in this specification, the technical solutions in the embodiments of this specification will be clearly and completely described below in conjunction with the drawings in the embodiments of this specification. Obviously, the described embodiments are only part of the embodiments of this application, not all of them. Based on the embodiments of this specification, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of this application.

[0032] In order to prevent the sparks generated when the output is overcurrent or the load is short-circuited from igniting flammable and explosive gases, the intrinsically safe power supply must use a protection circuit to limit the energy of the spark. In an intrinsically safe power supply, the higher the short-circuit current value, the greater the energy of the spark; the short-circuit current value is proportional to the product of the short-circuit protection time and the output voltage, that is, the higher the output voltage, the longer the short-circuit protection time and the greater the short-circuit current value. When the energy of the safety spark is constant, the higher the voltage, the shorter the short-circuit protection time must be, and the lower the voltage, the longer the allowable short-circuit protection time. Therefore, low-voltage and low-power intrinsically safe power supplies are easy to pass the spark test, while high-voltage and high-power intrinsically safe power supplies are not easy to pass the spark test. The intrinsically safe power supply must use a protection circuit to limit the energy of the spark.

[0033] In the prior art, the direct switch-off mode of the intrinsically safe power supply is that after an output overcurrent or load short-circuit fault occurs, the current detection circuit first detects the overcurrent or short-circuit signal, and then controls the switch circuit to change the switch tube (usually a MOS tube) in the switch circuit from the on state to the off state to perform short-circuit protection. This mode has the following shortcomings: First, in order to reduce the energy of the spark during a short circuit, the short-circuit protection action time needs to be as short as possible, which requires improving the sensitivity of the current detection circuit and reducing the short-circuit protection threshold. The reduction of the threshold will cause the output power to drop; second, the protection action is fast and easily interfered, resulting in false action, causing the subsequent load to be erroneously powered off, affecting the normal operation of the equipment; third, this protection circuit makes the power output of the intrinsically safe power supply small, which limits the application.

[0034] The linear voltage regulation plus switch shutdown mode of the intrinsically safe power supply is to connect an LDO linear three-terminal voltage regulator in series at the rear end of the non-safe output, and connect a control switch after the LDO voltage regulator to complete the protection function under the control of the current detection circuit. In this way, since the transistor of the three-terminal voltage regulator works in the linear region, the short-circuit current can be quickly limited when a short circuit occurs, so that the short-circuit current is significantly reduced. In order to limit the spark energy, the protection time of the back-stage switch protection circuit has sufficient margin. However, this method has many shortcomings: First, due to the series connection of the LDO voltage regulator, the LDO input and output voltage drops are large, which significantly increases the power consumption of the circuit; second, due to the need for heat dissipation, the power supply volume is increased; third, due to the influence of the rated current of the LDO circuit, the output power of the intrinsically safe power supply is relatively small, which limits its application.

[0035] The hierarchical protection method of the intrinsically safe power supply adopts two-stage series protection. The first stage is fast protection, that is, when the detection circuit detects that the loop current is several times greater than the rated output current of the intrinsically safe power supply, the switch circuit is quickly controlled to cut off the output loop; the other stage is overcurrent protection, that is, when the detection circuit detects that the loop current is greater than the rated output current of the intrinsically safe power supply, the switch circuit is controlled to cut off the output loop after a certain delay; although this method solves the anti-interference problem, it does not greatly improve the output power of the intrinsically safe power supply.

[0036] Based on this, the embodiments of this specification provide an intrinsically safe power supply protection circuit provided by the embodiments of this specification, such as Figure 1 As shown, the protection circuit includes:

[0037] Filter module 1, comparison control module 2, current sampling circuit 3, fast delay circuit 4', fast protection switch unit 4, slow delay circuit 5', slow protection switch unit 5;

[0038] in,

[0039] The filtering module is used to eliminate low-frequency harmonics and high-frequency harmonics generated after the load is connected;

[0040] The comparison control module is used to provide a fast protection action comparison voltage and a slow protection action comparison voltage;

[0041] The current sampling circuit is used to generate a differentially amplified voltage difference from the output current of the intrinsically safe circuit;

[0042] The fast delay circuit provides current limiting delay and current limiting holding time, which is used to delay the short circuit protection control signal;

[0043] The slow delay circuit provides overcurrent delay and overcurrent holding time, and is used to delay the overcurrent protection control signal.

[0044] In the embodiment of this specification, the filtering module includes: an electrolytic capacitor for eliminating low-frequency harmonics and a polypropylene capacitor for eliminating high-frequency harmonics. The electrolytic capacitor and the polypropylene capacitor are connected in parallel to both ends of the DC power input and the wire grounding terminal.

[0045] In an embodiment of the present specification, the comparison control module provides the current sampling circuit with two-level control signals of fast and slow current protection, and the two-level control signals of fast and slow current protection include: the overcurrent protection control signal and the short-circuit protection control signal, the short-circuit protection control signal is a fast protection control signal, and the overcurrent protection control signal is a slow protection control signal.

[0046] In the embodiment of this specification, the current sampling circuit is used to generate a differential amplified voltage difference of the output current of the intrinsically safe circuit, specifically including:

[0047] The current sampling circuit forms a voltage drop at both ends of a sampling resistor using the output current of the intrinsically safe circuit, differentially amplifies the voltage drop, and generates the fast and slow current protection two-level control signals through the comparison control module.

[0048] In the embodiment of this specification, the overcurrent delay time of the slow protection switch unit is:

[0049] Tq=T2+T3

[0050] in:

[0051] Tq is the overcurrent delay time of the slow protection switch unit;

[0052] T2 is the current limiting delay time of the fast protection switch unit;

[0053] T3 is the current limiting holding time.

[0054] In the embodiment of this specification, the fast protection switch unit of the protection circuit contains a current limiting element, and the current limiting element is a power resistor;

[0055] The resistance value of the power resistor is:

[0056] R=Uo / K*Iq(1.1 <K<1.3);

[0057] in,

[0058] Uo is the intrinsically safe output voltage;

[0059] Iq is the current limiting action value;

[0060] K is the correlation coefficient;

[0061] R is the resistance value of the power resistor.

[0062] In the embodiment of the present specification, the current limiting action value is a preset multiple of the overcurrent action value, and both the current limiting action value and the overcurrent action value can be adjusted by the comparison controller.

[0063] In the embodiment of this specification, the fast delay circuit and the slow delay circuit have the same delay circuit structure.

[0064] It should be noted that the function of the power resistor is to limit the current, so the power resistor is also called the current limiting resistor, and the resistance value R of the power resistor is also called the current limiting resistor value.

[0065] In order to further understand the protection circuit provided by the embodiments of this specification, the following will be described in conjunction with the structural schematic diagram of the intrinsically safe power supply protection circuit.

[0066] Figure 2 The structural intention of an intrinsically safe power protection circuit provided in the embodiments of this specification is as follows: Figure 2 As shown, the filter module 1 is composed of an electrolytic capacitor C1 and a CBB (polypropylene) capacitor C2. C1 and C2 are connected in parallel to both ends of the DC power supply Uin (input) and GND (grounding terminal of the wire, representing the ground wire or 0 line); it is mainly used for filtering to eliminate low-frequency and high-frequency harmonics formed after the load is connected. C1 eliminates low-frequency harmonics and C2 eliminates high-frequency harmonics.

[0067] The comparison control module 2 is composed of several resistors, a capacitor, a voltage-stabilizing diode and a voltage detection chip. In one embodiment of the present specification, the comparison control module 2 is composed of resistors R1, R2, R3, R4, R5, capacitor C4, voltage-stabilizing diode Z1 and voltage detection chip CN303; resistors R1, R2, capacitor C4 and voltage-stabilizing diode Z1 form a voltage-dividing circuit connected to the DC power supply Uin and GND, and output a 6V voltage at R2 to provide a working voltage for the voltage detection chip CN303; resistors R3, R4 and R5 are connected in series to form a voltage-dividing circuit connected to the DC power supply GND and the output end of the current sampling circuit 3, and the comparison control module 2 is passed through resistors R3, R4 and R5. Through two comparison voltages, namely: the voltage between R4 and R5 is the fast protection action comparison voltage, and the voltage between R3 and R4 is the slow protection action comparison voltage; wherein the integrated circuit CN303 is a dual-channel voltage detection chip, comprising two comparators A2, A3, a 1.211V high-precision reference voltage source and a hysteresis control circuit; the integrated circuit CN303 is powered by a voltage divider circuit composed of resistors R1, R2, capacitor C4, and Zener diode Z1, and the output end of the current sampling circuit 3 provides a comparison voltage to the voltage divider through resistors R3, R4, and R5 to complete the two-level control signals of fast and slow current protection.

[0068] The current sampling circuit 3 is composed of a sampling resistor, C3 and a current sampling chip INA199A2DCKT. The sampling resistor can be Rshunt (shunt resistor)

[0069] One end of the sampling resistor is connected to the positive output terminal Uin of the DC power supply, and the other end is connected to the positive output terminal Uo (output voltage value) of the intrinsic safety circuit; one end Uin of the sampling resistor is connected to the positive input terminal of the differential signal of INA199, and one end Uo of the sampling resistor is connected to the negative input terminal of the differential signal of INA199DCKT; the power input terminal V+ of INA199A2DCKT is connected to the DC power supply Uin, the negative power supply GND of INA199A2DCKT is connected to the reference voltage REF terminal and connected to the DC power supply GND, and the differential amplifier output terminal Vout of INA199A2CKTD is connected to one end of the resistor R5 of the comparison control module 2 (not the common terminal R5 of R4);

[0070] In order to further understand the current sampling circuit, the working principle of the current sampling circuit is briefly introduced below: the output current passes through the sampling resistor, forming a voltage drop across the sampling resistor, which is differentially amplified by INA199A2DCKT and compared by comparison control module 2 to generate a protection control signal.

[0071] The fast protection switch unit 4 is composed of resistors R8, R9, R10, R11, a power resistor R12, a voltage stabilizing diode Z2 and NMOS tubes G1, G2 and G3; wherein the MOS tube G1 and the fast delay circuit 4' constitute a driving circuit for the fast switch MOS tubes G2 and G3; the MOS tubes G2 and G3 are dual-element design schemes adopted by the protection switch unit according to the intrinsic safety requirements; R9, R10, R11, the voltage stabilizing diode Z2, the MOS tubes G2 and G3 constitute a switch circuit, and the voltage stabilizing diode Z2 is used to limit the voltage applied between the gate and source of R10, R11 and the MOS tubes G2 and G3 to prevent the driving voltage from exceeding the limit voltage between the gate and source of the MOS tubes G2 and G3 and burning the MOS tubes; the power resistor R12 is a current limiting resistor used to limit the current of the protected circuit when the fast switch is disconnected.

[0072] The fast delay circuit 4' is composed of resistors R6, R7, a switch diode D1, and a capacitor C5, and is used to delay the Kq short-circuit protection control signal, and is also the driving circuit of the MOS tube G1;

[0073] The slow protection switch unit 5 is composed of resistors R15, R16, R17, R18, a voltage stabilizing diode Z3 and NMOS tubes G4, G5 and G6; wherein the MOS tube G4 and the slow delay circuit 5' constitute the driving circuit of the fast switching MOS tubes G5 and G6; the resistors R13, R14, the switching diode D2 and the capacitor C6 constitute the driving circuit of the MOS tube G4; the MOS tubes G5 and G6 are dual-element design schemes adopted by the protection switch unit according to the intrinsic safety requirements; R16, R17, R18, the voltage stabilizing diode Z3, the MOS tubes G5 and G6 constitute the switching circuit, and the voltage stabilizing diode Z3 is used to limit the voltage applied between the gate and source of R16, R17 and the MOS tubes G5 and G6 to prevent the driving voltage from exceeding the limit voltage between the gate and source of the MOS tubes G5 and G6 and burning the MOS tubes;

[0074] The slow delay circuit 5 ′ is composed of resistors R13 , R14 , a switch diode D2 , and a capacitor C6 , and is used to delay the Ks short-circuit protection control signal, and is also a driving circuit for the MOS tube G4 .

[0075] In order to further understand the protection circuit provided by the embodiments of this specification, the working principle of the protection circuit will be described in detail below.

[0076] (1) Current sampling and signal conditioning

[0077] When the output terminals Uo and Un are short-circuited, a short-circuit current flows from Uin to Uo through the sampling resistor Rshunt, generating a voltage drop across the sampling resistor Rshunt (10mΩ2W). The voltage drop is amplified by the current amplifier INA199A2DCKT (amplification ratio 100V / V), and the signal Vout is sent to the next stage for comparison;

[0078] (2) Generation of fault protection action signal

[0079] When the loop current is greater than the current action value Ie (the set value is about 1.5A in the figure), the voltage at point A is higher than 1.211V, and comparator A2 outputs a high level, that is, Ks is a high level; this action value Ie is the overcurrent protection action value (referred to as the overcurrent action value).

[0080] When the loop current is greater than the current action value Iq (the action value is about 6A in the figure), the voltage at point B is higher than 1.211V, and comparator A3 outputs a high level; this action value Iq is the fast current limiting protection action value (referred to as the current limiting action value).

[0081] The current limiting action value and the overcurrent action value can be adjusted by adjusting the resistance values ​​of R3, R4, and R5. Therefore, the current limiting action value and the overcurrent action value can be adjusted according to the specific application scenario.

[0082] (3) Overcurrent delay and overcurrent holding time (slow delay circuit 5')

[0083] Overcurrent protection delay principle diagram as shown below Figure 3 As shown in (b), generally R14 is about 10K-30K, R13 is 100K-1M ohm, and C6 is between a few nanofarads and a few microfarads. When Ks is at a high level, C6 and the source-drain capacitance Cgs of MOS tube G4 are charged through R14 and D2. Since R14 is much smaller than R13, the charging speed basically depends on the values ​​of R14, C6 and Cgs. When the voltage across C6 is higher than the turn-on voltage of MOS tube G4, MOS tube G4 is turned on; MOS tubes G5 and G6 act to disconnect the circuit, and the overcurrent fault disappears. In this way, from the occurrence of the overcurrent fault to the action of MOS tubes G5 and G6 to disconnect the circuit, a delay period is required. This period of time is the overcurrent protection delay time (referred to as overcurrent delay), and the length of the overcurrent protection delay time is set by R14 and C6.

[0084] When the overcurrent fault is removed, Ks is at a low level, and diode D2 is cut off. At this time, C6 and Cgs discharge through R13. Figure 4(b), since R13 is much larger than R14, the conduction time of MOS tube G4 will last for a long time. When the voltage across C6 and Cgs is lower than the turn-on voltage of MOS tube G4, MOS tube G4 is disconnected, the drain of MOS tubes G5 and G6 is high, MOS tubes G5 and G6 are turned on, and the loop works normally. If the overcurrent fault is truly relieved at this time, the circuit works normally; if the overcurrent fault is not relieved, the above process is repeated to form hiccup protection; from the release of the overcurrent action control signal to the end of the overcurrent action, the duration of the overcurrent action (the duration of the MOS tubes G5 and G6 being disconnected) is the overcurrent action holding time (hereinafter referred to as the overcurrent holding time); the overcurrent action holding time can be set by R13 and C6.

[0085] (4) Current limiting delay and current limiting holding time (fast delay circuit 4')

[0086] The current limiting protection delay principle diagram is as follows Figure 3 As shown in (a), generally R6 is about 10K-30K, R7 is 100K-1M ohm, and C5 is between a few nanofarads and a few microfarads. When Ks is at a high level, C5 and the source-drain capacitance Cgs of MOS tube G1 are charged through R6 and D1. Since R6 is much smaller than R7, the charging speed basically depends on the values ​​of R6, C5 and Cgs. When the voltage across C5 is higher than the turn-on voltage of MOS tube G1, MOS tube G1 is turned on; MOS tubes G2 and G3 are activated to disconnect the circuit, and the output circuit is limited by R12. In this way, from the occurrence of the output circuit short-circuit fault to the activation and disconnection of MOS tubes G2 and G3, there is a delay period, which is the current limiting protection delay time (referred to as current limiting delay). The length of the current limiting delay time is set by R6 and C5.

[0087] When the output circuit is limited by R12, Kp is at a low level, and diode D1 is cut off. At this time, C5 and Cgs discharge through R7. Figure 4 (a), since R7 is much larger than R6, the conduction time of MOS tube G1 will last for a long time. When the voltage across C5 and Cgs is lower than the turn-on voltage of MOS tube G1, MOS tube G1 is disconnected, the drain of MOS tubes G2 and G3 is high, MOS tubes G2 and G3 are turned on, and the loop works normally. If the short circuit fault is truly relieved at this time, the circuit works normally; if the short circuit fault is not relieved, the above process is repeated to form hiccup protection; from the release of the current limiting protection action control signal to the end of the current limiting protection action, the duration of the current limiting protection action (the duration of the MOS tubes G2 and G3 being disconnected) is the duration of the overcurrent protection action (current limiting holding time); the current limiting holding time can be set by R13 and C6.

[0088] (5) Overcurrent protection principle

[0089] When the load current exceeds the overcurrent action value Ie( Figure 2When the medium action value is 1.5A), the voltage across the sampling resistor Rshunt exceeds 1.211V at point A after being amplified by INA199A2DCKT, and the comparator A2 outputs a high level, Ks is a high level, and after being delayed by the slow delay circuit 5', Ks drives the MOS tubes G5 and G6 in the slow protection switch unit 5 to disconnect the loop, and the protection is activated.

[0090] The overcurrent fault current is small, and the protection action delay time is long. Since the current is small, the impact energy is also small, which will not cause damage to the power supply. However, the sharp pulses and high-frequency interference under the condition that the load current is close to the set current are filtered, which is beneficial to anti-interference;

[0091] During overcurrent protection, the voltage at point B is much lower than 1.211V, which will not trigger the MOS tube in the fast protection switch unit protection;

[0092] Figure 5 The overcurrent protection is the voltage waveform at each point and the output current waveform. The overcurrent action value in the figure is Ie, and the fast delay circuit 4' and the fast protection switch unit 4 do not act; in the figure, the T2 period In is the load current in the loop, which is greater than Ie, and overcurrent protection occurs; the T1 period The loop works normally and the load current is less than Ie.

[0093] (6) Current limiting protection principle

[0094] When a short circuit fault occurs, the voltage across the sampling resistor Rshunt is amplified by INA199A2DCKT, and the voltage at points A and B exceeds 1.211V. Comparators A2 and A3 both output high levels, and Kq and Ks are high levels. After Kq is delayed by the fast delay circuit 4', it drives the MOS tubes G2 and G3 in the fast protection switch unit 4 to disconnect the loop; after Ks is delayed by the slow delay circuit 5', it drives the MOS tubes G5 and G6 in the slow protection switch unit 5 to disconnect the loop;

[0095] During a short-circuit fault, the current is relatively large, and the current limiting delay is as short as possible to avoid damage to the power supply; therefore, the fast delay circuit 4' has a very short delay, and the fast protection switch unit 4 is disconnected in a relatively short time; at the same time, the comparator A2 also outputs a high level, and the slow delay circuit 5' is also delayed, but the delay time is greater than the delay time of the fast delay circuit 4', so the slow protection switch unit 5 is in the on state; since the R12 power resistor is connected in parallel to the switch in the fast protection switch unit 4, the loop current at this time flows back to the power supply GND terminal after being limited by the resistor R12, and the loop current is less than Uo / R12, which limits the energy released by the short-circuit Uo and Un on the short-circuit side;

[0096] If the short-circuit fault disappears quickly, the slow delay circuit 5' and the slow protection switch unit 5 do not have time to act. Before the current limiting holding time of the fast delay circuit 4' and the fast protection switch unit 4 ends, the entire loop is in a closed state due to the existence of R12; due to the current limiting effect of R12, the short-circuit voltage and short-circuit current between Uo and Un are reduced, that is, the active energy is reduced; at the same time, during the current limiting holding time period and the period when the short-circuit fault disappears, R12 also has a freewheeling effect to keep providing energy to the load side, ensuring that the load will not stop due to a long-term power failure or restart due to interference;

[0097] If the short-circuit fault persists, the slow delay circuit 5' and the slow protection switch unit 5 will be activated for overcurrent protection, completely cutting off the circuit. After the overcurrent holding time of the slow delay circuit 5' ends, the slow protection switch unit 5 will be closed and the circuit will work normally. If the short-circuit fault is not relieved, the above process will be repeated to form hiccup protection.

[0098] To sum up, if an overcurrent fault occurs in the circuit, under the activation of the overcurrent signal Ks, the slow delay circuit 5' and the slow protection switch unit 5 cooperate to form hiccup overcurrent protection until the overcurrent fault disappears; if a continuous short circuit fault occurs in the circuit, the fast delay circuit 4' and the fast protection switch unit 4 as well as the slow delay circuit 5' and the slow protection switch unit 5 all generate protection actions, the fast delay circuit 4' and the fast protection switch unit 4 complete the current limiting protection action, and the slow delay circuit 5' and the slow protection switch unit 5 complete the circuit cutting action, forming hiccup short circuit protection until the short circuit fault disappears; if interference or a short circuit fault of extremely short duration occurs in the circuit, only the fast delay circuit 4' and the fast protection switch unit 4 generate current limiting protection action, which will not cause a large impact on the load side, thereby improving the power supply reliability.

[0099] The protection circuit provided in the embodiments of this specification does not require a heat sink, is small in size, and is low in price and highly reliable.

[0100] In practical applications, the protection circuit provided in the embodiments of this specification can be used in scenarios where load capacity is to be improved. The protection circuit can form a loop with a power supply, a DC power supply, etc. to achieve the purpose of improving load capacity.

[0101] The embodiments of this specification provide a method for applying a protection circuit to an intrinsically safe power supply, and specifically, provide a method for improving the load capacity of an intrinsically safe power supply, such as Figure 6 As shown, the method includes:

[0102] Step S601: determining the loop current formed by the intrinsically safe power supply and the protection circuit;

[0103] Step S603: When the loop current is greater than a preset short-circuit protection setting value, a protection action is generated based on the protection circuit;

[0104] Step S605: Detecting the output current of the protection action;

[0105] Step S607: if the output current of the protection action is greater than the preset overcurrent action value, cutting off the loop formed by the intrinsically safe power supply and the protection circuit;

[0106] If the output current of the protection action is not greater than the preset overcurrent action value, the loop composed of the intrinsically safe power supply and the protection circuit supplies power to the load normally.

[0107] In the embodiment of this specification, the protection circuit includes:

[0108] Filter module, comparison control module, current sampling circuit, fast delay circuit, fast protection switch unit, slow delay circuit, slow protection switch unit;

[0109] in,

[0110] The filtering module is used to eliminate low-frequency harmonics and high-frequency harmonics generated after the load is connected;

[0111] The comparison control module is used to provide a fast protection action comparison voltage and a slow protection action comparison voltage;

[0112] The current sampling circuit is used to generate a differentially amplified voltage difference from the output current of the intrinsically safe circuit;

[0113] The fast delay circuit provides current limiting delay and current limiting holding time, which is used to delay the short circuit protection control signal;

[0114] The slow delay circuit provides overcurrent delay and overcurrent holding time, and is used to delay the overcurrent protection control signal.

[0115] In the embodiment of this specification, the filtering module includes: an electrolytic capacitor for eliminating low-frequency harmonics and a polypropylene capacitor for eliminating high-frequency harmonics. The electrolytic capacitor and the polypropylene capacitor are connected in parallel to both ends of the DC power input and the wire grounding terminal.

[0116] In an embodiment of the present specification, the comparison control module provides the current sampling circuit with two-level control signals of fast and slow current protection, and the two-level control signals of fast and slow current protection include: the overcurrent protection control signal and the short-circuit protection control signal, the short-circuit protection control signal is a fast protection control signal, and the overcurrent protection control signal is a slow protection control signal.

[0117] In the embodiment of this specification, the current sampling circuit is used to generate a differential amplified voltage difference of the output current of the intrinsically safe circuit, specifically including:

[0118] The current sampling circuit forms a voltage drop at both ends of a sampling resistor using the output current of the intrinsically safe circuit, differentially amplifies the voltage drop, and generates the fast and slow current protection two-level control signals through the comparison control module.

[0119] In the embodiment of this specification, the overcurrent delay time of the slow protection switch unit is:

[0120] Tq=T2+T3

[0121] in:

[0122] Tq is the overcurrent delay time of the slow protection switch unit;

[0123] T2 is the current limiting delay time of the fast protection switch unit;

[0124] T3 is the current limiting holding time.

[0125] In the embodiment of this specification, the fast protection switch unit of the protection circuit contains a current limiting element, and the current limiting element is a power resistor;

[0126] The resistance value of the power resistor is:

[0127] R=Uo / K*Iq(1.1 <K<1.3);

[0128] in,

[0129] Uo is the intrinsically safe output voltage;

[0130] Iq is the current limiting action value;

[0131] K is the correlation coefficient;

[0132] R is the resistance value of the power resistor.

[0133] In the embodiment of the present specification, the current limiting action value is a preset multiple of the overcurrent action value, and both the current limiting action value and the overcurrent action value can be adjusted by the comparison controller.

[0134] In the embodiment of this specification, the fast delay circuit and the slow delay circuit have the same delay circuit structure.

[0135] In combination with a specific embodiment, when an overcurrent fault occurs in the circuit of the intrinsically safe power supply, the current sampling circuit and the comparison control module generate an overcurrent protection signal, and the overcurrent protection signal drives the slow delay circuit and the slow switch unit to form a hiccup overcurrent protection until the overcurrent fault disappears;

[0136] When a continuous short-circuit fault occurs in the circuit of the intrinsically safe power supply, the current sampling circuit and the comparison control module generate an overcurrent protection signal and a short-circuit protection signal, and the short-circuit protection signal drives the fast delay circuit and the fast protection switch unit as well as the slow delay circuit and the slow protection switch unit to generate protection actions, the fast delay circuit and the fast protection switch unit complete the current limiting protection action, and the overcurrent protection signal drives the slow delay circuit and the slow protection switch unit to complete the circuit cutting action, thereby forming short-circuit protection during hiccups until the short-circuit fault disappears;

[0137] When interference or a short-time short-circuit fault occurs in the circuit of the intrinsically safe power supply, the current sampling circuit and the comparison control circuit generate a short-circuit protection signal, and the short-circuit protection signal drives the fast delay circuit and the fast protection switch unit to generate a current limiting protection action.

[0138] In order to further understand the method for improving the load capacity of an intrinsically safe power supply provided in the embodiments of this specification, it will be described in detail below in conjunction with the waveform diagram.

[0139] Figure 7 This is a waveform diagram of the short protection action when the current surge current duration is short provided in the embodiment of this specification. Figure 7 As shown, Im is the short-circuit impact current, Ip is the current limiting action value, Is is the current limiting current value, Ie is the overcurrent action value, In is the normal output current ( <Ie)。

[0140] From top to bottom in the figure are the intrinsically safe power supply output current waveform, the fast protection control signal Kq waveform, the fast switch unit C point voltage waveform, the slow protection control signal Ks waveform, and the slow switch unit D point voltage waveform;

[0141] Stage T1 is the normal working state of the intrinsically safe power supply. At this time, the output current of the intrinsically safe power supply is In, which is less than the rated current Ie of the intrinsically safe power supply, Kq and Ks are at low levels, points C and D are at high levels, and the intrinsically safe power supply supplies power to the load normally;

[0142] T2 short-circuit current limiting protection delay time. When a short-circuit fault or a large current shock occurs at the output of the intrinsically safe power supply (assuming the current is Im>Ip), Kq and Kp are high level, the fast delay circuit 4' starts to delay for T2 period, and the slow delay circuit 5' starts to delay for Tq period (Tq=T2+T3), during which point C and point D are still high level;

[0143] The T3 stage is the current limiting duration. When the quick delay circuit 4' finishes delaying, the output at point C is at a low level, disconnecting the loop. The duration of the low level at point C is the current limiting protection (limiting the current to Is < Ip) duration; the slow (overcurrent) protection control signal Ks remains at a high level during the T2 and T3 time periods until the end of the T3 stage; the output at point D is at a high level during the T2 and T3 time periods until the end of the T3 stage.

[0144] The T4 stage is the recovery stage. If the short - circuit fault or large - current impact duration is less than Tq, then after T3 ends, the loop current returns to In, Kq is still at a low level, and the output at point C is at a high level,解除限流保护; simultaneously, since the delay time of the quick delay circuit 4' is equal to Tq, point D is still at a high level, and the loop is in a normal closed state. However, since the short - circuit fault or large - current impact has been removed, the loop resumes normal power supply.

[0145] Figure 8 This is the short - circuit protection action waveform diagram when a short - circuit fault persists provided by the embodiment of this specification. As Figure 8 shown, the working principles of the T1, T2, and T3 stages are the same as Figure 7 those described above and will not be elaborated here. However, in the T4 stage, if the short - circuit fault or large - current impact persists, then point D becomes at a low level, and this circuit is in a short - circuit protection state, with the output current being zero, and the protection duration being T4; the T5 time period is the same as the T2 time period, which is the over - current protection action delay stage. After the short - circuit protection lasts for T4 time, point D becomes at a high level again due to the end of the protection action delay, and the output loop is connected; since point C is also at a high level, there is no current - limiting measure in the loop, and the loop current returns to the impact current value Im. The subsequent process is like Figure 8 the T2, T3, and T4 in

[0146] Adopting the method for improving the load capacity of the intrinsically safe power supply provided by the embodiment of this specification can significantly improve the output power of the intrinsically safe power supply, improve the anti - interference ability of the intrinsically safe power supply when approaching the rated output, avoid the restart phenomenon caused by the protection action due to small fluctuations in current when the load current is close to the rated output current, and the intrinsically safe power supply has low power consumption and high efficiency.

[0147] The above describes specific embodiments of this specification. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps recited in the claims can be performed in a different order than in the embodiments and still achieve the desired result. Additionally, the processes depicted in the figures do not necessarily require the specific order or sequential order shown to achieve the desired result. In certain embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0148] Each embodiment in this specification is described in a progressive manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the device, electronic device, and non-volatile computer storage medium embodiments, since they are basically similar to the method embodiments, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiments.

[0149] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.

[0150] Each embodiment in this specification is described in a progressive manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment.

[0151] The above is only an embodiment of this specification and is not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.

Claims

1. An intrinsically safe power supply protection circuit, characterized in that: The protection circuit comprises: Filter module, comparison control module, current sampling circuit, fast delay circuit, fast protection switch unit, slow delay circuit, slow protection switch unit; in, The filtering module is used to eliminate low-frequency harmonics and high-frequency harmonics generated after the load is connected; The comparison control module is used to provide a fast protection action comparison voltage and a slow protection action comparison voltage; The current sampling circuit is used to generate a differentially amplified voltage difference for the output current of the intrinsically safe circuit, specifically including: the current sampling circuit forms a voltage drop at both ends of the sampling resistor for the output current of the intrinsically safe circuit, differentially amplifies the voltage drop, and generates the fast and slow current protection two-level control signals through the comparison control module, wherein the fast protection control signal is a short-circuit protection control signal, and the slow protection control signal is an overcurrent protection control signal, specifically including: when an overcurrent fault occurs in the circuit of the intrinsically safe power supply, the current sampling circuit and the comparison control module generate an overcurrent protection signal, and the overcurrent protection signal drives the slow delay circuit and the slow protection switch unit to form a hiccup overcurrent protection until the overcurrent fault disappears; when a continuous short-circuit fault occurs in the circuit of the intrinsically safe power supply, the The current sampling circuit and the comparison control module generate an overcurrent protection signal and a short-circuit protection signal, and the short-circuit protection signal drives the fast delay circuit and the fast protection switch unit as well as the slow delay circuit and the slow protection switch unit to generate protection actions, and the fast delay circuit and the fast protection switch unit complete the current limiting protection action, and the overcurrent protection signal drives the slow delay circuit and the slow protection switch unit to complete the circuit cutting action, forming short-circuit protection during hiccups until the short-circuit fault disappears; when interference or a short-term short-circuit fault occurs in the circuit of the intrinsically safe power supply, the current sampling circuit and the comparison control module generate a short-circuit protection signal, and the short-circuit protection signal drives the fast delay circuit and the fast protection switch unit to generate a current limiting protection action; The fast delay circuit provides current limiting delay and current limiting holding time, which is used to delay the short circuit protection control signal; The slow delay circuit provides overcurrent delay and overcurrent holding time, which is used to delay the overcurrent protection control signal. The overcurrent delay time of the slow protection switch unit is: Tq=T2+T3 in: Tq is the overcurrent delay time of the slow protection switch unit; T2 is the current limiting delay time of the fast protection switch unit; T3 is the current limiting holding time.

2. The protection circuit according to claim 1, characterized in that: The filtering module comprises: an electrolytic capacitor for eliminating low-frequency harmonics and a polypropylene capacitor for eliminating high-frequency harmonics. The electrolytic capacitor and the polypropylene capacitor are connected in parallel to both ends of the input of the DC power supply and the grounding end of the wire.

3. The protection circuit according to claim 1, characterized in that: The fast protection switch unit of the protection circuit contains a current limiting element, and the current limiting element is a power resistor; The resistance value of the power resistor is: R=Uo / K*Iq(1.1 <K<1.3); in, Uo is the intrinsically safe output voltage; Iq is the current limiting action value; K is the correlation coefficient; R is the resistance value of the power resistor.

4. The protection circuit according to claim 3, characterized in that: The current limiting action value is a preset multiple of the overcurrent action value, and both the current limiting action value and the overcurrent action value can be adjusted by the comparison control module.

5. The protection circuit according to claim 1, characterized in that: The fast delay circuit and the slow delay circuit have the same delay circuit structure.

6. A method for improving the load capacity of an intrinsically safe power supply, characterized in that: The method comprises: Determine the loop current consisting of the intrinsically safe power supply and any of the protection circuits described above; When the loop current is greater than a preset short-circuit protection setting value, a protection action is generated based on the protection circuit; Detecting the output current of the protection action; If the output current of the protection action is greater than the preset overcurrent action value, the loop formed by the intrinsically safe power supply and the protection circuit is cut off; If the output current of the protection action is not greater than the preset overcurrent action value, the loop composed of the intrinsically safe power supply and the protection circuit supplies power to the load normally.

7. The method according to claim 6, characterized in that When the loop current is greater than the preset short-circuit protection setting value, a protection action is generated based on the protection circuit, specifically including: When the loop current is greater than the preset short-circuit protection setting value, and the loop current is greater than the overcurrent action value, then after the slow delay circuit of the protection circuit, the slow protection switch unit of the protection circuit is driven to disconnect the loop, generating an overcurrent protection action; When the loop current is greater than the preset short-circuit protection setting value, and the loop current is greater than the current limiting action value, then after the fast delay circuit of the protection circuit, the fast protection switch unit of the protection circuit is driven to disconnect the loop; and after the slow delay circuit of the protection circuit, the slow protection switch unit of the protection circuit is driven to disconnect the loop, generating a current limiting protection action.

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