Power-off holding circuit applied to programmable controller and circuit board of power-off holding circuit

Abstract

The utility model discloses a power-off holding circuit applied to a programmable controller and a circuit board of the power-off holding circuit. The power-off holding circuit comprises an energy storage module, an output switch module, a first detection module and a second detection module, the input end of the energy storage module is connected with the output end of the system main power supply, and the output end is connected with the post-stage working circuit through the output switch module and is connected with the control end of the first detection module; the output end of the first detection module is connected with a post-stage working circuit through the output switch module and used for monitoring the voltage value of the energy storage module, and when the voltage value of the energy storage module is lower than a preset energy storage voltage value, the output switch module is controlled to disconnect the circuit connection between the energy storage module and the system main power supply. The output end of the second detection module is connected with the control end of the first detection module, the control end of the second detection module is connected with the post-stage working circuit, and the second detection module is used for monitoring the voltage value of the post-stage working circuit and controlling the first detection module to be in a closed state when the voltage value of the post-stage working circuit is lower than a preset working voltage value. And voltage jitter can be avoided.

Description

Technical Field

[0001] The utility model relates to the technical field of power supply circuits, in particular to a power-off holding circuit and a circuit board thereof applied to a programmable controller. Background Art

[0002] In order to meet the increasing demand for power supply stability of electronic equipment, the power supply circuit of current equipment will use large-capacity aluminum electrolytic capacitors or farad capacitors to store energy and provide power to the system when the power is off. Usually, the instantaneous current generated at the moment of power-on is large, and the power supply power requirement is high when charging the energy storage capacitor. In addition, the energy storage capacitor needs to be charged first, and the subsequent circuit will not start working until it is charged to a certain level. The power-on time of the subsequent circuit is slow and there is a certain delay.

[0003] Inevitably, the capacitor itself has a certain internal resistance, and the voltage drop is large when the current is high. When the load is turned off, the output voltage will increase, which will further cause the subsequent circuit to restart. When the current increases, the voltage will drop immediately. At this time, the subsequent circuit will cut off work and reduce the load. After the load is reduced, the capacitor output voltage increases, causing the subsequent circuit to restart. This repetition may cause system abnormalities.

[0004] Therefore, there is a need for a circuit that can control the subsequent working circuit to not restart repeatedly when the voltage fluctuates after power failure. Summary of the invention

[0005] The utility model provides a power-off holding circuit applied to a programmable controller, which can realize cutting off the current input of a subsequent circuit when the voltage shakes after power failure.

[0006] In order to solve the above technical problems, the utility model provides a power-off holding circuit applied to a programmable controller, comprising an energy storage module, an output switch module, a first detection module and a second detection module;

[0007] The input end of the energy storage module is connected to the output end of the system main power supply, the output end of the energy storage module is connected to the subsequent working circuit via the output switch module, and the output end of the energy storage module is also connected to the control end of the first detection module;

[0008] The output end of the first detection module is connected to the subsequent working circuit via the output switch module, and is used to monitor the voltage value of the energy storage module, and control the output switch module to disconnect the circuit connection between the energy storage module and the main power supply of the system when the voltage value of the energy storage module is lower than the preset energy storage voltage value;

[0009] The output end of the second detection module is connected to the control end of the first detection module, and the control end of the second detection module is connected to the subsequent working circuit, for monitoring the voltage value of the subsequent working circuit, and controlling the first detection module to be in a conduction state when the voltage value of the subsequent working circuit is lower than a preset working voltage value.

[0010] The utility model forms a power-off holding circuit applied to a programmable controller through the connection between an energy storage module, an output switch module, a first detection module and a second detection module. When the first detection module detects that the voltage of the energy storage module meets the set value, and the second detection module detects that the voltage at the output of the output switch module meets the set value, the output switch module is turned on, so that the energy storage module is powered by the output switch module. However, when any one of the detection voltages of the first detection module or the second detection module does not meet the set value, the output switch module cannot be triggered to open, and the energy storage module cannot be powered by the output switch module. The above method can control the circuit to not restart repeatedly when the voltage jitters, thereby avoiding voltage jitters.

[0011] As a preferred example, the input end of the energy storage module is connected to the output end of the system main power supply, specifically including:

[0012] The input end of the energy storage module is connected to the output end of the system main power supply through a current limiting module.

[0013] This preferred example also connects the current limiting module, the system main power supply and the energy storage module so that the system main power supply charges the energy storage module through the current limiting module.

[0014] As a preferred example, the current limiting module includes a first fuse;

[0015] The first port of the first fuse is connected to the output end of the main power supply of the system;

[0016] The second port of the first fuse is connected to the input end of the energy storage module.

[0017] In this preferred example, a current limiting module is formed by a first fuse to prevent the circuit from being damaged due to excessive current in the circuit. When the current in the circuit is too large, the first fuse in the current limiting circuit is blown to cause a current short circuit to protect the rear end single circuit.

[0018] As a preferred example, the energy storage module includes any one of a capacitor energy storage module, a battery energy storage module and a lithium battery energy storage module.

[0019] In this preferred example, the energy storage module is composed of any one of a capacitor energy storage module, a battery energy storage module and a lithium battery energy storage module. When the system main power supply is supplied, the energy storage module is charged. When the system main power supply stops supplying power, the energy storage module supplies power to the outside.

[0020] As a preferred example, the output switch module includes a first triode and a first MOS tube;

[0021] The base of the first transistor is connected to the output end of the first detection module;

[0022] The source of the first MOS tube is connected to the output end of the energy storage module;

[0023] The collector of the first transistor is connected to the gate of the first MOS transistor.

[0024] As a preferred example, the output switch module further includes a first resistor, a second resistor, a third resistor and a fourth resistor;

[0025] The first port of the first resistor is connected to the source of the first MOS transistor, and the second port of the first resistor is connected to the base of the first transistor;

[0026] The first port of the second resistor is connected to the base of the first transistor, and the second port of the second resistor is connected to the emitter of the first transistor;

[0027] A first port of the third resistor is connected to the source of the first MOS transistor, a second port of the third resistor is connected to the gate of the first MOS transistor, and the second port of the third resistor is also connected to the first port of the fourth resistor;

[0028] A fourth resistor is further provided between the collector of the first triode and the gate of the first MOS tube.

[0029] In this preferred example, an output switch module is composed of a first transistor, a first MOS transistor, a first diode, a first resistor, a second resistor, a third resistor and a fourth resistor. When the voltages detected by the first detection module and the second detection module both meet the voltage setting values, the first MOS transistor and the first transistor are turned on so that the power supply current of the energy storage module passes through the output switch module to supply power to the subsequent stage.

[0030] As a preferred example, the output switch module is connected to the subsequent working circuit through a first diode.

[0031] In this preferred example, a first diode between the output switch module and the subsequent working circuit is used to prevent current backflow in the circuit.

[0032] As a preferred example, the first transistor is an NPN transistor; the first MOS transistor is a P-MOS transistor.

[0033] In this preferred example, NPN transistors are used as the second transistor, the third transistor and the first transistor. Initially, the second transistor and the third transistor are in a cut-off state due to the base voltage, because the base voltage has not yet reached the level that makes them conduct. When it is detected that the base voltages of the second transistor and the third transistor have reached the corresponding conduction level, they are turned on to allow current to pass through, and the second transistor and the third transistor conduct the first detection module and the second detection module, so that the base of the first transistor in the output switch module meets the corresponding conduction level, thereby turning on the first transistor. At the same time, current backflow is also prevented.

[0034] In this preferred example, by using a P-MOS tube as the first MOS tube, the first transistor is initially in a cut-off state due to the base voltage of the first transistor, because the base voltage of the first transistor has not yet reached the level for it to be turned on. When it is detected that the base voltage of the first transistor reaches the corresponding turn-on level, the first transistor is turned on to allow current to pass, so that the base of the first MOS tube meets the corresponding turn-on level, and further conduction is performed to open the output switch module, and the current of the energy storage module is transported to the subsequent working circuit. At the same time, current backflow is also prevented.

[0035] As a preferred example, the first detection module includes a second triode, a fifth resistor and a sixth resistor, specifically:

[0036] The base of the second transistor is connected to the second port of the fifth resistor, the base of the second transistor is also connected to the first port of the sixth resistor, the collector of the second transistor is connected to the second port of the first detection module, and the base of the second transistor is connected to the third port of the first detection module;

[0037] The first port of the fifth resistor is connected to the first port of the first detection module;

[0038] The first port of the sixth resistor is connected to the second port of the fifth resistor, and the second port of the sixth resistor is connected to the emitter of the second transistor.

[0039] In this preferred example, the voltage of the energy storage capacitor in the energy storage module is detected by the first detection module to determine the on / off of the output switch module.

[0040] As a preferred example, the second detection module includes a third triode, a seventh resistor and an eighth resistor, specifically:

[0041] The base of the third triode is connected to the first port of the seventh resistor, the base of the third triode is also connected to the first port of the eighth resistor, and the collector of the third triode is connected to the first port of the second detection module;

[0042] The second port of the seventh resistor is connected to the second port of the second detection module;

[0043] The first port of the eighth resistor is connected to the second port of the seventh resistor, the first port of the eighth resistor is also connected to the base of the third transistor, and the second port of the eighth resistor is also connected to the emitter of the third transistor.

[0044] The utility model also proposes a power-off holding circuit board applied to a programmable controller, comprising a power-off holding circuit applied to a programmable controller as described in the embodiment of the utility model.

[0045] The utility model forms a power-off holding circuit board applied to a programmable controller through a power-off holding circuit board applied to a programmable controller, and forms a power-off holding circuit applied to a programmable controller through the connection between an energy storage module, an output switch module, a first detection module, and a second detection module. When the first detection module detects that the voltage of the energy storage module meets the set value, and the second detection module detects that the voltage at the output of the output switch module meets the set value, the output switch module is turned on, so that the energy storage module is powered by the output switch module. However, when any one of the detection voltages of the first detection module or the second detection module does not meet the set value, the output switch module cannot be triggered to open, and the energy storage module cannot be powered by the output switch module. Through the above method, the circuit can be controlled not to restart repeatedly when the voltage jitters, thereby avoiding voltage jitters. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is a module diagram of a power-off holding circuit applied to a programmable controller in a certain embodiment provided by the utility model;

[0047] Figure 2 This is a complete module diagram of a power-off holding circuit applied to a programmable controller in a certain embodiment provided by the utility model.

[0048] Figure 3 The utility model provides a certain embodiment of a power-off holding circuit schematic diagram applied to a programmable controller. DETAILED DESCRIPTION

[0049] The following will be combined with the drawings in the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0050] Embodiment 1

[0051] See also Figure 1 and Figure 2 , the utility model provides a power-off holding circuit module diagram applied to a programmable controller, comprising an energy storage module 1, an output switch module 2, a first detection module 3 and a second detection module 4;

[0052] The input end of the energy storage module 1 is connected to the output end of the system main power supply 6, the output end of the energy storage module 1 is connected to the subsequent working circuit 7 via the output switch module 2, and the output end of the energy storage module 1 is also connected to the control end of the first detection module 3;

[0053] The output end of the first detection module 3 is connected to the subsequent working circuit 7 via the output switch module 2, and is used to monitor the voltage value of the energy storage module 1, and control the output switch module 2 to disconnect the circuit connection between the energy storage module 1 and the subsequent working circuit 7 when the voltage value of the energy storage module 1 is lower than the preset energy storage voltage value;

[0054] The output end of the second detection module 4 is connected to the control end of the first detection module 3, and the control end of the second detection module 4 is connected to the post-stage working circuit 7, for monitoring the voltage value of the post-stage working circuit 7, and controlling the first detection module 3 to be in a conduction state when the voltage value of the post-stage working circuit 7 is lower than a preset working voltage value.

[0055] The embodiment of the utility model forms a power-off holding circuit applied to a programmable controller through the connection between the energy storage module 1, the output switch module 2, the first detection module 3 and the second detection module 4. When the first detection module 3 detects that the voltage of the energy storage module 1 meets the set value, and the second detection module 4 detects that the voltage at the output of the output switch module 2 meets the set value, the output switch module 2 is turned on, so that the energy storage module 1 is powered by the output switch module 2. However, when any one of the detection voltages of the first detection module 3 or the second detection module 4 does not meet the set value, the output switch module cannot be triggered to open, and the energy storage module 1 cannot be powered by the output switch module 2. Through the above method, the circuit can be controlled not to restart repeatedly when the voltage jitters, thereby avoiding voltage jitters.

[0056] See also Figure 2 In the embodiment of the utility model, the input end of the energy storage module 1 is connected to the output end of the system main power supply 6, specifically including:

[0057] The input end of the energy storage module 1 is connected to the output end of the system main power supply 7 through the current limiting module 5 .

[0058] In the embodiment of the utility model, the current limiting module 5 , the system main power supply 6 and the energy storage module 1 are connected so that the system main power supply 6 charges the energy storage module through the current limiting module 5 .

[0059] In an embodiment of the utility model, the current limiting module includes a first fuse;

[0060] The first port of the first fuse is connected to the output end of the main power supply of the system;

[0061] The second port of the first fuse is connected to the input end of the energy storage module.

[0062] The embodiment of the utility model forms a current limiting module through the first fuse to prevent the circuit from being damaged due to excessive current in the circuit. When the current in the circuit is too large, the first fuse in the current limiting circuit is blown to cause the current to short-circuit and protect the rear-end single circuit.

[0063] See also Figure 3 In an embodiment of the utility model, the energy storage module 1 includes any one of a capacitor energy storage module, a battery energy storage module and a lithium battery energy storage module.

[0064] The embodiment of the utility model forms an energy storage module 1 through any one of a capacitor energy storage module C47, a battery energy storage module C47 and a lithium battery energy storage module C47. When the system main power supply 6 supplies power, the energy storage module 1 is charged. When the system main power supply 6 stops supplying power, the energy storage module 1 supplies power to the outside.

[0065] See also Figure 3 In the embodiment of the utility model, the output switch module 2 includes a first transistor Q2 and a first MOS transistor Q1;

[0066] The base of the first transistor Q2 is connected to the output end of the first detection module 3;

[0067] The source of the first MOS tube Q1 is also connected to the output end of the energy storage module 1;

[0068] The collector of the first transistor Q2 is connected to the gate of the first MOS transistor Q1.

[0069] In the embodiment of the utility model, the output switch module further includes a first resistor R82, a second resistor R85, a third resistor R80 and a fourth resistor R81;

[0070] A first port of the first resistor R82 is connected to the source of the first MOS transistor Q1, and a second port of the first resistor R82 is connected to the base of the first transistor Q2;

[0071] A first port of the second resistor R85 is connected to the base of the first transistor Q2, and a second port of the second resistor R85 is connected to the emitter of the first transistor Q2;

[0072] A first port of the third resistor R80 is connected to the source of the first MOS transistor Q1, a second port of the third resistor R80 is connected to the gate of the first MOS transistor Q1, and the second port of the third resistor R80 is also connected to the first port of the fourth resistor R81;

[0073] A fourth resistor R81 is further provided between the collector of the first transistor Q2 and the gate of the first MOS transistor Q1 .

[0074] In the embodiment of the utility model, an output switch module is formed by a first transistor Q2, a first MOS transistor Q1, a first resistor R82, a second resistor R85, a third resistor R80 and a fourth resistor R81. When the voltages detected by the first detection module 3 and the second detection module 4 both meet the voltage setting values, the first MOS transistor Q1 and the first transistor Q2 are turned on so that the power supply current of the energy storage module 1 is supplied to the subsequent stage through the output switch module 2.

[0075] See also Figure 3 In the embodiment of the utility model, the output switch module 2 is connected to the subsequent working circuit 7 through the first diode D12.

[0076] In the embodiment of the utility model, the first diode D12 between the output switch module 2 and the subsequent working circuit 7 is used to prevent the current from flowing back in the circuit.

[0077] See also Figure 3 In the embodiment of the utility model, the first transistor Q2 is an NPN transistor; the first MOS transistor Q1 is a P-MOS transistor.

[0078] The embodiment of the utility model adopts NPN transistors as the second transistor Q3, the third transistor Q4 and the first transistor Q2. Initially, the second transistor Q3 and the third transistor Q4 are in a cut-off state due to the base voltage, because the base voltage has not yet reached the level that makes them conduct. When it is detected that the base voltage of the second transistor Q3 and the third transistor Q4 has reached the corresponding conduction level, conduction is performed to allow current to pass, and the second transistor Q3 and the third transistor Q4 conduct the first detection module and the second detection module, so that the base of the first transistor Q2 in the output switch module meets the corresponding conduction level, thereby conducting the first transistor Q2. At the same time, current backflow is also prevented.

[0079] The embodiment of the utility model adopts a P-MOS tube as the first MOS tube Q1, which is initially in a cut-off state due to the base voltage of the first transistor Q2, because the base voltage of the first transistor Q2 has not yet reached the level for it to be turned on. When it is detected that the base voltage of the first transistor Q2 reaches the corresponding turn-on level, the first transistor Q2 is turned on to allow current to pass, so that the base of the first MOS tube Q1 meets the corresponding turn-on level, and further turns on to open the output switch module, and transports the current of the energy storage module to the subsequent working circuit 7. At the same time, current backflow is also prevented.

[0080] See also Figure 3 In the embodiment of the utility model, the first detection module 3 includes a second transistor Q3, a fifth resistor R84 and a sixth resistor R86, specifically:

[0081] The base of the second transistor Q3 is connected to the second port of the fifth resistor R84, the base of the second transistor Q3 is also connected to the first port of the sixth resistor R86, the collector of the second transistor Q3 is connected to the second port of the first detection module 3, and the base of the second transistor Q3 is connected to the third port of the first detection module 3;

[0082] The first port of the fifth resistor R84 is connected to the first port of the first detection module 3;

[0083] A first port of the sixth resistor R86 is connected to a second port of the fifth resistor R84 , and a second port of the sixth resistor R86 is connected to an emitter of the second transistor Q3 .

[0084] In the embodiment of the utility model, the voltage of the energy storage capacitor C47 in the energy storage module 1 is detected by the first detection module 3 to determine whether the output switch module 2 is turned on or off.

[0085] See also Figure 3 In the embodiment of the utility model, the second detection module 4 includes a third transistor Q4, a seventh resistor R83 and an eighth resistor R87, specifically:

[0086] The base of the third transistor Q4 is connected to the first port of the seventh resistor R83, the base of the third transistor Q4 is also connected to the first port of the eighth resistor R87, and the collector of the third transistor Q4 is connected to the first port of the second detection module 4;

[0087] The second port of the seventh resistor R83 is connected to the second port of the second detection module 4;

[0088] The first port of the eighth resistor R87 is connected to the second port of the seventh resistor R83, the first port of the eighth resistor R87 is also connected to the base of the third transistor Q4, and the second port of the eighth resistor R87 is also connected to the emitter of the third transistor Q4.

[0089] The utility model also proposes a power-off holding circuit board applied to a programmable controller, comprising a power-off holding circuit applied to a programmable controller as described in the embodiment of the utility model.

[0090] The utility model forms a power-off holding circuit board applied to a programmable controller through a power-off holding circuit board applied to a programmable controller, and forms a power-off holding circuit applied to a programmable controller through the connection between an energy storage module 1, an output switch module 2, a first detection module 3, and a second detection module 4. When the first detection module 3 detects that the voltage of the energy storage module 1 meets the set value, and the second detection module 4 detects that the voltage at the output of the output switch module 2 meets the set value, the output switch module 2 is turned on, so that the energy storage module 1 is powered by the output switch module 2. However, when any one of the detection voltages of the first detection module 3 or the second detection module 4 does not meet the set value, the output switch module 2 cannot be triggered to open, and the energy storage module 1 cannot be powered by the output switch module 2. Through the above method, the circuit can be controlled not to restart repeatedly when the voltage jitters, thereby avoiding voltage jitters.

[0091] Embodiment 2

[0092] See also Figure 3 , when the circuit is powered on normally, the main power supply directly supplies power to the working circuit, providing stable voltage and current.

[0093] When the forward voltage through D3 and D11 reaches the threshold, current will be conducted. The current limiting circuit composed of D3 and D11 limits the current passing through to protect the energy storage element from being damaged due to excessive charging current, ensuring that the charging process proceeds slowly, and preventing current backflow when the main power supply is cut off and the energy storage module 1 is used to supply power.

[0094] The fuse F2 in the energy storage module 1 performs secondary current limiting on the current. When the current passing through it exceeds its rated value, it will disconnect to protect the circuit from overcurrent damage. The energy storage capacitor C47 is slowly charged by the current flowing through it, so that the voltage of the energy storage capacitor C47 rises until it reaches the rated voltage of the energy storage capacitor C47, reducing the impact on the main power supply and may provide current smoothing or decoupling function at the initial stage of circuit startup.

[0095] When the main power supply is powered on, as the voltage across the energy storage capacitor C47 gradually rises, the transistor Q3 of the first detection module 3 constantly monitors the voltage of the energy storage capacitor C47. At the same time, the transistor Q4 of the second detection module 4 detects whether the voltage of the subsequent working circuit 7 reaches the specified voltage threshold.

[0096] When the voltage across the energy storage capacitor C47 does not meet the specified voltage threshold, the transistor Q3 of the first detection module 3 is turned off; when the voltage across the energy storage capacitor C47 meets the specified voltage threshold, the transistor Q3 of the first detection module 3 is turned on. The specified voltage threshold is set by the resistors R84 and R86 in the first detection module 3.

[0097] When the voltage of the subsequent working circuit 7 does not reach the specified voltage threshold, the transistor Q4 of the second detection module 4 is turned off; when the voltage of the subsequent working circuit 7 reaches the specified voltage threshold, the transistor Q4 of the second detection module 4 is turned on. The specified voltage threshold is set by the resistors R83 and R87 in the second detection module 4.

[0098] Since the transistor Q3 in the first detection module 3 is cut off, the collector voltage of the transistor Q3 is associated with the voltage of the energy storage capacitor C47, and further the base voltage of the transistor Q2 in the output switch module 2 connected thereto is associated with the voltage of the energy storage capacitor C47. When the voltage of the energy storage capacitor C47 increases so that the base voltage of the transistor Q2 increases to the voltage threshold set by R82 and R85 in the output switch module, the transistor Q2 is turned on, and further the collector voltage of the transistor Q2 is reduced, and the gate voltage of the PMOS tube Q1 connected thereto is reduced. When the gate voltage of the PMOS tube Q1 is reduced to the voltage threshold set by R80 and R81, the PMOS tube Q1 is turned on, so that the energy storage capacitor C47 in the energy storage module can supply power to the subsequent working circuit 7 through the output switch module.

[0099] When the main power supply is powered off, the subsequent working circuit 7 is continuously powered by the energy storage capacitor C47 in the energy storage module 1. When the voltage across the energy storage capacitor C47 drops to a certain threshold, the base monitoring voltage of the transistor Q3 in the first detection module 3 is lower than the trigger conduction voltage, so that the transistor Q3 is turned off, and the base voltage of the transistor Q2 in the output switch module 2 is further reduced, and the transistor Q2 is turned off. At this time, the collector voltage of the transistor Q2 increases, so that the gate voltage of the PMOS tube Q1 also increases and increases until the PMOS tube Q1 is turned off, so that the energy storage module 1 cannot supply power to the subsequent working circuit 7. At this time, the transistor Q4 in the second voltage detection unit module 4 detects that the voltage of the subsequent working circuit 7 is still in a low voltage state, that is, the base of the transistor Q4 is a low voltage, and the transistor Q4 is turned off.

[0100] When the output switch is closed, the output voltage of the energy storage capacitor C47 in the energy storage module 1 will increase due to the reduced load, and the transistor Q3 in the first detection module 3 will detect that the voltage of the energy storage capacitor C47 has reached a short-term increase to the set threshold, which will turn on the transistor Q3, but the subsequent working circuit connected to the base of the transistor Q4 is at a low level, so the transistor Q4 is turned off, and then the energy storage capacitor will discharge through the transistor Q3, resulting in insufficient base voltage of the transistor Q2, causing the transistor Q2 to be turned off, and then causing the transistor Q1 to be turned off, so that the output switch module cannot be triggered to open, thereby avoiding the voltage jitter problem.

[0101] The utility model proposes a power-off holding circuit and a circuit board thereof applied to a programmable controller, and forms a power-off holding circuit applied to a programmable controller through the connection between an energy storage module, an output switch module, a first detection module, and a second detection module. When the second transistor of the first detection module detects that the voltage of the energy storage module meets the set value, and the third transistor of the second detection module detects that the voltage at the output of the output switch module meets the set value, the output switch module is turned on, so that the energy storage module is powered by the output switch module. However, when any one of the detection voltages of the first detection module or the second detection module does not meet the set value, the output switch module cannot be triggered to open, and the energy storage module cannot be powered by the output switch module. The above method can control the circuit to not restart repeatedly when the voltage jitters, thereby avoiding voltage jitters.

[0102] The above is a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several improvements and modifications without departing from the principle of the present invention. These improvements and modifications are also considered to be within the protection scope of the present invention.

Claims

1. A power-off holding circuit applied to a programmable controller, characterized in that: It includes an energy storage module, an output switch module, a first detection module and a second detection module; The input end of the energy storage module is connected to the output end of the system main power supply, the output end of the energy storage module is connected to the subsequent working circuit via the output switch module, and the output end of the energy storage module is also connected to the control end of the first detection module; The output end of the first detection module is connected to the subsequent working circuit via the output switch module, and is used to monitor the voltage value of the energy storage module, and control the output switch module to disconnect the circuit connection between the energy storage module and the subsequent working circuit when the voltage value of the energy storage module is lower than the preset energy storage voltage value; The output end of the second detection module is connected to the control end of the first detection module, and the control end of the second detection module is connected to the subsequent working circuit, for monitoring the voltage value of the subsequent working circuit, and controlling the first detection module to be in a conduction state when the voltage value of the subsequent working circuit is lower than a preset working voltage value.

2. A power-off holding circuit for a programmable controller according to claim 1, characterized in that: The input end of the energy storage module is connected to the output end of the system main power supply, specifically including: The input end of the energy storage module is connected to the output end of the system main power supply through a current limiting module.

3. A power-off holding circuit applied to a programmable controller according to claim 2, characterized in that: The current limiting module includes a first fuse; The first port of the first fuse is connected to the output end of the main power supply of the system; The second port of the first fuse is connected to the input end of the energy storage module.

4. A power-off holding circuit for a programmable controller according to claim 1, characterized in that: The energy storage module includes any one of a capacitor energy storage module, a battery energy storage module and a lithium battery energy storage module.

5. A power-off holding circuit for a programmable controller according to claim 1, characterized in that: The output switch module includes a first triode and a first MOS tube; The base of the first transistor is connected to the output end of the first detection module; The source of the first MOS tube is connected to the output end of the energy storage module; The collector of the first transistor is connected to the gate of the first MOS transistor.

6. A power-off holding circuit for a programmable controller according to claim 5, characterized in that: The output switch module further includes a first resistor, a second resistor, a third resistor and a fourth resistor; The first port of the first resistor is connected to the source of the first MOS transistor, and the second port of the first resistor is connected to the base of the first transistor; The first port of the second resistor is connected to the base of the first transistor, and the second port of the second resistor is connected to the emitter of the first transistor; A first port of the third resistor is connected to the source of the first MOS transistor, a second port of the third resistor is connected to the gate of the first MOS transistor, and the second port of the third resistor is also connected to the first port of the fourth resistor; A fourth resistor is further provided between the collector of the first triode and the gate of the first MOS tube.

7. A power-off holding circuit for a programmable controller according to claim 5, characterized in that: The output switch module is connected to the subsequent working circuit via a first diode.

8. The power-off holding circuit applied to a programmable controller according to claim 5, characterized in that: The first transistor is an NPN transistor; the first MOS transistor is a P-MOS transistor.

9. A power-off holding circuit for a programmable controller according to claim 1, characterized in that: The first detection module includes a second triode, a fifth resistor and a sixth resistor, specifically: The base of the second transistor is connected to the second port of the fifth resistor, the base of the second transistor is also connected to the first port of the sixth resistor, the collector of the second transistor is connected to the second port of the first detection module, and the base of the second transistor is connected to the third port of the first detection module; The first port of the fifth resistor is connected to the first port of the first detection module; The first port of the sixth resistor is connected to the second port of the fifth resistor, and the second port of the sixth resistor is connected to the emitter of the second transistor.

10. A power-off holding circuit for a programmable controller according to claim 1, characterized in that: The second detection module includes a third triode, a seventh resistor and an eighth resistor, specifically: The base of the third triode is connected to the first port of the seventh resistor, the base of the third triode is also connected to the first port of the eighth resistor, and the collector of the third triode is connected to the first port of the second detection module; The second port of the seventh resistor is connected to the second port of the second detection module; The first port of the eighth resistor is connected to the second port of the seventh resistor, the first port of the eighth resistor is also connected to the base of the third transistor, and the second port of the eighth resistor is also connected to the emitter of the third transistor.

11. A power-off retention circuit board applied to a programmable controller, characterized in that: It comprises a power-off holding circuit applied to a programmable controller as described in any one of claims 1 to 10.

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