CN201213222Y - A rear-stage working circuit protection device for a dual-circuit power supply system - Google Patents

Abstract

The utility model discloses a protection device for a rear-stage working circuit of a dual-circuit power supply system, which comprises an on-off control circuit and a detection circuit, the on-off control circuit is located between the power supply and a power conversion circuit, and the detection circuit is connected to At the output end of the power conversion circuit, the working states of the two power supplies are detected respectively, and the detection results are compared and judged to output a state control signal, and the output end of the detection circuit is connected to the detection circuit of the on-off control circuit, When any one of the two power conversion circuits fails, the state control signal sent from the output terminal of the detection circuit controls the on-off control circuit to turn off the working power, thereby realizing the protection of the subsequent working circuit. The protection device for the latter stage working circuit of the utility model can detect the presence or absence of the output voltages of the two circuits, detect a large drop of the voltage, and the circuit is simple and reliable.

Description

A rear-stage working circuit protection device for a dual-circuit power supply system

technical field

The utility model relates to the power supply protection of medical electronic products, in particular to a rear-stage working circuit protection device of a dual-way power supply system.

Background technique

At present, for medical electronic products with high reliability requirements, such as X-ray machines, etc., in most cases, due to the different power supply methods of the working circuits of various parts of medical electronic products, if the power supply of the key part of the No output or a large drop in power supply voltage caused by faulty short circuit or damage may lead to damage to the working circuit of the subsequent stage or misoperation of the system. Therefore, when a power failure occurs in a key part, it is necessary to be able to detect and take action immediately, that is, to shut down the working power of the entire system or subsystem, so as to protect the subsequent circuit.

The existing power supply protection circuit usually only protects the circuit of a single working power supply, that is, a protection circuit is set between each power conversion circuit and the subsequent working circuit, as shown in Figure 1, and for systems with associated The circuits of different power supply parts cannot be detected and protected at the same time. On the other hand, when the existing power supply protection circuit protects the working circuit of the subsequent stage, a part of the power supply protection circuit does not have the function of saving the fault state, which is prone to repeated oscillations caused by the power-on again immediately after the entire system is powered off. Not only does it fail to protect the working circuit of the subsequent stage, but it is likely to cause damage to the working circuit of the subsequent stage. Another part of the power protection circuit uses disposable electronic components, such as fuses, which can directly cut off the working voltage of the subsequent circuit after the fuse is blown. Although the fault state is preserved, the fuse needs to be replaced frequently, which increases maintenance costs.

Utility model content

The purpose of this utility model is to provide a protection device for the rear-stage working circuit of a dual-circuit power supply system. When a power failure occurs in any of the two outputs of the power supply, the power-off protection of the rear-stage working circuit is performed, thereby preventing the subsequent stage from The working circuit is damaged or not working properly.

The technical scheme adopted by the utility model is that the rear-stage working circuit protection device of the dual-way power supply system includes an on-off control circuit and a detection circuit, and the on-off control circuit is located between the power supply and the power conversion circuit. The detection circuit is connected to the output end of the power conversion circuit, respectively detects the working states of the two power conversion circuits, and outputs a state control signal after comparing and judging the detection results. The output end of the detection circuit is connected with the on-off control circuit When any one of the two power conversion circuits fails, the state control signal sent by the output terminal of the detection circuit controls the on-off control circuit to turn off the power supply, thereby realizing the protection of the subsequent working circuit .

When the power supply adopts direct current, the detection circuit and the on-off control circuit are directly powered by the power supply; when the power supply adopts alternating current, the rear-stage working circuit protection device of the dual power supply system also The starting power supply is included, and the starting power supply is connected across the power supply to convert the AC voltage into a low-voltage DC working power supply to supply power for the detection circuit and the on-off control circuit.

By adopting the above-mentioned technical scheme, the utility model has at least the following advantages:

The rear working circuit protection device of the dual power supply system of the utility model adopts an optocoupler as a detection device for the output of each power conversion circuit. Since the optocoupler has an isolation function, it can simultaneously monitor two circuits that share a common ground or do not share a common ground. Detection can detect the presence or absence of two output voltages, and due to the introduction of the reference voltage module, the detection circuit can detect a large drop in voltage, and the control signal output according to the detection results can protect the working circuit of the subsequent stage. The circuit is simple and reliable. Because the optocoupler is used as the output of the circuit, the detectable voltage range is wide.

The protective device for the subsequent working circuit of the present invention has the function of maintaining the fault state, avoiding the repeated oscillation caused by the power-on again immediately after the whole system is powered off, so that the working circuit of the subsequent stage is not damaged. In addition, there is no response to interference signals such as burrs in the control signal, which enhances the stability of the system.

Description of drawings

FIG. 1 is a schematic diagram of an existing protection circuit;

Fig. 2 is a block diagram of the first embodiment of the rear-stage working circuit protection device of the dual-circuit power supply system of the present invention;

Fig. 3 is the circuit schematic diagram of the first embodiment of the rear-stage working circuit protection device of the dual-circuit power supply system of the present invention;

Fig. 4 is a schematic diagram of the on-off control circuit in the first embodiment of the utility model;

5 is a block diagram of the second embodiment of the rear-stage working circuit protection device of the dual-circuit power supply system of the present invention;

Fig. 6 is the circuit principle diagram of the second embodiment of the rear-stage working circuit protection device of the dual-circuit power supply system of the present invention;

Fig. 7 is a schematic diagram of the on-off control circuit in the second embodiment of the utility model;

Fig. 8 is a circuit schematic diagram of the reference voltage module in the second embodiment of the present invention;

Fig. 9 is a schematic diagram of the on-off control circuit in the third embodiment of the present invention.

Detailed ways

In order to further explain the technical means and effects of the utility model to achieve the predetermined purpose, the following is a detailed description of the protection device for the post-stage working circuit of a dual-way power supply system proposed by the utility model in conjunction with the accompanying drawings and preferred embodiments. The description is as follows.

The block diagram of the first embodiment of the rear-stage working circuit protection device of the dual-circuit power supply system of the present invention is shown in Figure 2, which is divided into the following parts:

The starting power supply circuit is mainly for the dual power supply system using AC power supply, which converts the AC voltage into a DC voltage and provides it to the detection circuit and the on-off control circuit. For a dual-circuit power supply system using a DC power supply, the detection circuit and the on-off control circuit can directly use the power supply voltage.

The detection circuit is used to detect whether there is a fault in the output of the two power supplies, and output a state control signal, and can output a normal state control signal during initial power-on and normal operation. This part of the circuit can detect the two outputs with or without common ground, and can also detect two voltage signals in the same direction or reverse direction, and has a wide detection range for the two voltages.

The on-off control circuit is mainly used for the on-off control of the working voltage of the dual-way power supply system. After the detection circuit sends the control signal, the power supply can be automatically turned off. The on-off control circuit has the function of maintaining the fault state to prevent In the event of a fault, in order to protect the working circuit of the subsequent stage, the power is turned off immediately after the power is turned on again, resulting in repeated oscillation of the entire system.

The circuit principle of the first embodiment of the utility model is shown in Figure 3, the starting power supply Vs is connected across the power supply Vi, the detection circuit is composed of two power supply output circuits and a comparison circuit, and the first power supply output circuit includes a first optocoupler U1, the first resistor R1, the second resistor R2 and the first reference voltage module, the second power supply output circuit includes the second optocoupler U2, the third resistor R3, the fourth resistor R4 and the second reference voltage module, the comparison circuit It includes a third optocoupler U3, a fourth optocoupler U4, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7 and a light emitting diode D1.

The positive output terminal V1+ of the first power conversion circuit is connected to the positive terminal of the input side of the first optocoupler U1 through the first resistor R1, and the negative terminal of the input side of the first optocoupler U1 is connected to the positive terminal of the first reference voltage module. The negative terminal of a reference voltage module is connected to the negative output terminal V1- of the first power conversion circuit, the positive output terminal V2+ of the second power conversion circuit is connected to the positive terminal of the input side of the second optocoupler U2 through the third resistor R3, and the second The negative terminal of the input side of the optocoupler U2 is connected to the positive terminal of the second reference voltage module, and the negative terminal of the second reference voltage module is connected to the output negative terminal V2- of the second power conversion circuit.

The positive ends of the output sides of the first optocoupler U1 and the second optocoupler U2 are respectively connected to the starting power supply Vs through the first resistor R1 and the fourth resistor R4, and the negative ends of the output sides of the first optocoupler U1 and the second optocoupler U2 Connect to the GND end of the startup power supply Vs. The positive terminal on the output side of the first optocoupler U1 is connected to the positive terminal on the input side of the third optocoupler U3 and the negative terminal on the input side of the fourth optocoupler U4, and the positive terminal on the output side of the second optocoupler U2 is connected to the third optocoupler at the same time. The negative terminal on the input side of the coupler U3 and the positive terminal on the input side of the fourth optocoupler U4. The positive end of the output side of the third optocoupler U3 and the fourth optocoupler U4 are respectively connected to the starting power supply Vs through the fifth resistor R5 and the sixth resistor R6, while the positive end of the output side of the third optocoupler U3 and the fourth optocoupler U4 The positive terminals on the output side are connected, the detection circuit outputs the control signal CTR to the signal input terminal of the on-off control circuit, and the negative terminals on the output side of the third optocoupler U3 and the fourth optocoupler U4 are simultaneously connected to the GND terminal of the starting power supply Vs . The positive end of the light emitting diode D1 is connected to the start-up power supply Vs through the seventh resistor R7, and the negative end of the light emitting diode D1 is connected to the positive end of the output side of the fourth optocoupler U4, and is also connected to the signal input end of the on-off control circuit. The starting power supply Vs supplies power to the on-off control circuit.

The principle of the on-off control circuit in the first embodiment of the utility model is shown in Figure 4. The on-off control circuit adopts a triode, and the on-off control circuit includes a switch module and a fault state maintenance module. The switch module adopts an on-off control transistor VD3, and the fault state maintenance module includes a first transistor VD1, a second transistor VD2, a first current limiting resistor r1, a second current limiting resistor r2, a third current limiting resistor Resistor r3 and capacitor C.

The control signal CTR is input to the collector of the first transistor VD1, the base of the second transistor VD2 and the base of the on-off control transistor VD3 through the first current limiting resistor r1, and the base of the first transistor VD1 The collector of the second transistor VD2 is connected to the collector of the second transistor VD2 through the second current limiting resistor r2, the collector of the second transistor VD2 is grounded through the series branch composed of the third current limiting resistor r3 and the capacitor C, and the first transistor The emitter of VD1 is also grounded. The collector of the on-off control transistor VD3 is connected to the supply voltage Vi, and the emitter of the on-off control transistor VD3 is connected to the input terminal Vout of the power conversion circuit. The pull-up voltage Vcc of the second transistor VD2 is provided by the startup power supply Vs.

In the reference voltage module in the first embodiment of the present utility model, both the first reference voltage module and the second reference voltage module use a Zener tube to provide a reference voltage, and the negative pole of the Zener tube is connected to the negative terminal of the input side of the first optocoupler U1 , the positive pole of the Zener tube is connected to the output negative terminal of the power conversion circuit.

When the power is initially turned on, the first optocoupler U1, the second optocoupler U2, the third optocoupler U3, and the fourth optocoupler U4 are cut off, the control signal CTR sent by the detection circuit is at high level, and the second triode VD2 The base is at a high level, the second transistor VD2 is in the off state, and the capacitor C cannot be charged at this time, the base of the first transistor VD1 is at a low level, the first transistor VD1 is in the off state, and the on-off The base voltage of the control transistor VD3 is always high level, so the on-off control transistor VD3 is turned on, that is, the on-off control circuit is in the conduction state, and the power supply in the dual power supply system provides working voltage for the subsequent working circuit.

When both the first power conversion circuit and the second power conversion circuit are working normally, the first optocoupler U1 and the second optocoupler U2 are turned on, the third optocoupler U3 and the fourth optocoupler U4 are turned off, and the control signal CTR sent by the detection circuit It is always high level, the on-off control circuit is in the conduction state, and the power supply in the dual power supply system provides working voltage for the subsequent working circuit.

When a fault occurs, the first power conversion circuit has no output or the voltage drops sharply, the first optocoupler U1 and the fourth optocoupler U4 are cut off, the second optocoupler U2 and the third optocoupler U3 are turned on, and the control sent by the detection circuit The signal CTR is at low level, the LED D1 lights up, and the on-off control transistor VD3 is cut off, that is, the on-off control circuit is in the off state, and the power supply in the dual power supply system stops supplying power to the subsequent working circuit. The second transistor VD2 is turned on. At this time, the pull-up voltage of the second transistor VD2 charges the capacitor C through the third current limiting resistor r3. When the voltage on the capacitor C reaches a certain value, the first transistor VD1 conducts At this time, the base voltage of the on-off control transistor VD3 is always clamped at a low level, and the fault state is locked. At this time, even if the control signal CTR suddenly changes to a high level because the system is immediately powered on again, the on-off control circuit cannot be turned on, so it will not cause damage to the working circuit of the subsequent stage.

In addition, due to the existence of the capacitor charging time, there is no response to interference signals such as burrs in the control signal CTR, and the stability of the system is enhanced. When the system is working normally, the control signal CTR is always at a high level. At this time, if the interference signal on the space or the line enters the system, since the energy of the interference signal is generally small, the interference generation time is relatively short, so in the line control signal CTR There may be a negative pulse interference signal, causing the control signal CTR to drop from high level to low level in a short time, but it quickly returns to high level. At this time, due to the existence of the capacitor charging time, the control signal CTR becomes When it is low level, the second transistor VD2 starts to conduct and charge the capacitor C, but when the capacitor voltage is not charged enough to make the first transistor VD1 conduct, the control signal CTR changes from low level to high Level, the second triode VD2 cuts off, at this time the on-off control circuit has no protection action, and this interference signal can be ignored, thereby enhancing the stability and reliability of the system.

Similarly, when the second power conversion circuit has no output or the voltage drops sharply, the second optocoupler U2 and the third optocoupler U3 are turned off, the first optocoupler U1 and the fourth optocoupler U4 are turned on, and the control signal sent by the detection circuit When CTR is at low level, the on-off control circuit is in a disconnected state and remains in a fault state, and the light-emitting diode D1 is lit.

The block diagram of the second embodiment of the rear-stage working circuit protection device of the dual-circuit power supply system of the present invention is shown in Figure 5, which is divided into the following parts:

The detection circuit is used to detect whether there is a fault in the output of the two power supplies, and output a state control signal, and can output a normal state control signal during initial power-on and normal operation. This part of the circuit can detect the two outputs with or without common ground, and can also detect two voltage signals in the same direction or reverse direction, and has a wide detection range for the two voltages.

The on-off control circuit is mainly used for the on-off control of the working voltage of the dual-way power supply system. After the detection circuit sends the control signal, the power supply can be automatically turned off. The on-off control circuit has the function of maintaining the fault state to prevent In the event of a fault, in order to protect the working circuit of the subsequent stage, the power is turned off immediately after the power is turned on again, resulting in repeated oscillation of the entire system.

For a dual-circuit power supply system using a DC power supply, the detection circuit and the on-off control circuit can directly use the power supply voltage.

The circuit principle of the second embodiment of the utility model is shown in Figure 6. The detection circuit is composed of two power output circuits and a comparison circuit. The first power output circuit includes a first optocoupler U1, a first resistor R1, and a second resistor R2. and the first reference voltage module, the second power supply output circuit includes a second optocoupler U2, a third resistor R3, a fourth resistor R4 and a second reference voltage module, and the comparison circuit includes a third optocoupler U3, a fourth optocoupler U4, the fifth resistor R5, the sixth resistor R6, the seventh resistor R7 and the light emitting diode D1.

The positive output terminal V1+ of the first power conversion circuit is connected to the positive terminal of the input side of the first optocoupler U1 through the first resistor R1, and the negative terminal of the input side of the first optocoupler U1 is connected to the positive terminal of the first reference voltage module. The negative terminal of a reference voltage module is connected to the negative output terminal V1- of the first power conversion circuit, the positive output terminal V2+ of the second power conversion circuit is connected to the positive terminal of the input side of the second optocoupler U2 through the third resistor R3, and the second The negative terminal of the input side of the optocoupler U2 is connected to the positive terminal of the second reference voltage module, and the negative terminal of the second reference voltage module is connected to the output negative terminal V2- of the second power conversion circuit.

The positive ends of the output sides of the first optocoupler U1 and the second optocoupler U2 are respectively connected to the power supply Vi through the first resistor R1 and the fourth resistor R4, and the negative ends of the output sides of the first optocoupler U1 and the second optocoupler U2 Connect to the GND terminal of the power supply Vi. The positive terminal on the output side of the first optocoupler U1 is connected to the positive terminal on the input side of the third optocoupler U3 and the negative terminal on the input side of the fourth optocoupler U4, and the positive terminal on the output side of the second optocoupler U2 is connected to the third optocoupler at the same time. The negative terminal on the input side of the coupler U3 and the positive terminal on the input side of the fourth optocoupler U4. The positive end of the output side of the third optocoupler U3 and the fourth optocoupler U4 are respectively connected to the power supply Vi through the fifth resistor R5 and the sixth resistor R6, while the positive end of the output side of the third optocoupler U3 and the fourth optocoupler U4 The positive terminals on the output side are connected, the detection circuit outputs the control signal CTR to the signal input terminal of the on-off control circuit, and the negative terminals on the output side of the third optocoupler U3 and the fourth optocoupler U4 are simultaneously connected to the GND terminal of the power supply Vi . The positive end of the light-emitting diode D1 is connected to the power supply Vi through the seventh resistor R7, the negative end of the light-emitting diode D1 is connected to the signal input end of the on-off control circuit, and simultaneously connected to the positive end of the output side of the fourth optocoupler U4. The power supply Vi supplies power to the on-off control circuit.

The principle of the on-off control circuit in the second embodiment of the utility model is shown in Fig. 7. The on-off control circuit adopts the relay mode, and the relay mode can be applied to the working voltage of DC input or AC input. The on-off control circuit includes a switch module and a fault state holding module. The switch module adopts a normally closed electromagnetic relay, and the fault state holding module includes a first triode VD1, a second triode VD2, a first current limiting resistor r1, a second current limiting resistor r2, a third current limiting resistor Resistor r3 and capacitor C.

The control signal CTR is input to the collector of the first transistor VD1, the base of the second transistor VD2 and the relay through the first current limiting resistor r1. The other end of the relay is connected to the pull-up voltage Vcc, and the contacts in the relay are connected to the supply voltage Vi and the input terminal Vout of the power conversion circuit. The base of the first transistor VD1 is connected to the collector of the second transistor VD2 through the second current limiting resistor r2, and the collector of the second transistor VD2 is connected in series with the capacitor C through the third current limiting resistor r3 The branch is grounded, and the emitter of the first triode VD1 is also grounded. The pull-up voltage Vcc of the second transistor VD2 is provided by the startup power supply Vs.

The circuit principle of the reference voltage module in the second embodiment of the utility model is shown in Figure 8, the first reference voltage module and the second reference voltage module both use the TL431 chip module to provide a stable reference voltage, the first voltage dividing resistor Z1 and The second voltage dividing resistor Z2 is connected in parallel with the TL431 chip after being connected in series, and the reference terminal of the TL431 chip is connected between the first voltage dividing resistor Z1 and the second voltage dividing resistor Z2. In the first embodiment, the reference voltage module is realized by using a Zener tube alone, and the Zener tube can only make the stable voltage a fixed value, which is subject to certain restrictions in use. In the second embodiment, the reference voltage circuit composed of a TL431 chip module is used. The voltage regulation value can be adjusted through the first voltage dividing resistor Z1 and the second voltage dividing resistor Z2. The maximum regulated voltage value of the TL431 chip is 36V. For the case where a higher voltage is required, the reference voltage module can be cascaded.

When the power is initially turned on, the first optocoupler U1, the second optocoupler U2, the third optocoupler U3, and the fourth optocoupler U4 are cut off, the control signal CTR sent by the detection circuit is at high level, and the second triode VD2 The base is at a high level, the second transistor VD2 is in the cut-off state, and the capacitor C cannot be charged at this time, the base of the first transistor VD1 is at a low level, and the first transistor VD1 is in the cut-off state, at this time the relay If there is no current flowing in the coil of the relay, the contacts in the relay are always in the normally closed state, that is, the on-off control circuit is in the on-state, and the power supply in the dual power supply system provides working voltage for the subsequent working circuit.

When both the first power conversion circuit and the second power conversion circuit are working normally, the first optocoupler U1 and the second optocoupler U2 are turned on, the third optocoupler U3 and the fourth optocoupler U4 are turned off, and the control signal CTR sent by the detection circuit It is always high level. At this time, there is no current flowing in the coil of the relay, then the contacts in the relay are always in the normally closed state, the on-off control circuit is in the on-state, and the power supply in the dual power supply system is the post-stage The working circuit provides working voltage.

When a fault occurs, the first power conversion circuit has no output or the voltage drops sharply, the first optocoupler U1 and the fourth optocoupler U4 are cut off, the second optocoupler U2 and the third optocoupler U3 are turned on, and the control sent by the detection circuit The signal CTR is at low level, the light-emitting diode D1 lights up, the coil in the relay has current flowing, the contact in the relay is cut off, that is, the on-off control circuit is in the disconnected state, and the power supply in the dual power supply system Stop supplying power to the working circuit of the subsequent stage. At this time, the second triode VD2 is turned on. At this time, the pull-up voltage of the second triode VD2 charges the capacitor C through the third current limiting resistor R3. When the voltage on the capacitor C reaches When a certain value is reached, the first triode VD1 is turned on, and at this time, the voltage at the input terminal of the relay is always clamped at a low level, and the fault state is locked. At this time, even if the control signal CTR suddenly changes to a high level because the system is immediately powered on again, the on-off control circuit cannot be turned on, so it will not cause damage to the working circuit of the subsequent stage. In addition, due to the existence of the capacitor charging time, interference signals such as burrs in the control signal CTR can be ignored, thereby enhancing the stability and reliability of the system.

Similarly, when the second power conversion circuit has no output or the voltage drops sharply, the second optocoupler U2 and the third optocoupler U3 are turned off, the first optocoupler U1 and the fourth optocoupler U4 are turned on, and the control signal sent by the detection circuit When CTR is at low level, the on-off control circuit is in a disconnected state and remains in a fault state, and the light-emitting diode D1 is lit.

The circuit principle of the third embodiment of the utility model is roughly the same as that of the second embodiment, except that the on-off control circuit in the third embodiment adopts the MOSFET mode, as shown in Figure 9, the on-off control circuit includes a switch module and a fault state preservation module. The switch module adopts N-channel field effect transistor n-MOS, and the fault state holding module includes a first transistor VD1, a second transistor VD2, a first current limiting resistor r1, a second current limiting resistor r2, a second current limiting resistor Three current limiting resistor r3 and capacitor C.

The control signal CTR is input to the collector of the first transistor VD1, the base of the second transistor VD2 and the gate of the field effect transistor n-MOS through the first current limiting resistor r1, and the base of the first transistor VD1 The pole is connected to the collector of the second triode VD2 through the second current limiting resistor r2, the collector of the second triode VD2 is grounded through the series branch composed of the third current limiting resistor r3 and the capacitor C, and the first triode The emitter of the tube VD1 is also grounded. The drain of the field effect transistor n-MOS is connected to the supply voltage Vi, and the source of the field effect transistor n-MOS is connected to the input terminal Vout of the power conversion circuit. The pull-up voltage Vcc of the second transistor VD2 is provided by the startup power supply Vs.

When the power is initially turned on, the first optocoupler U1, the second optocoupler U2, the third optocoupler U3, and the fourth optocoupler U4 are cut off, the control signal CTR sent by the detection circuit is at high level, and the second triode VD2 The base is at a high level, the second transistor VD2 is in the cut-off state, and the capacitor C cannot be charged at this time, the base of the first transistor VD1 is at a low level, the first transistor VD1 is in the cut-off state, and the field effect The gate voltage of the transistor n-MOS is always high level, and there is a turn-on voltage between the gate and drain of the field effect transistor n-MOS, so the drain and source of the field effect transistor n-MOS are turned on, that is, on The off control circuit is in the conduction state, and the power supply in the dual power supply system provides working voltage for the subsequent working circuit.

When both the first power conversion circuit and the second power conversion circuit are working normally, the first optocoupler U1 and the second optocoupler U2 are turned on, the third optocoupler U3 and the fourth optocoupler U4 are turned off, and the control signal CTR sent by the detection circuit It is always high level, the on-off control circuit is in the conduction state, and the power supply in the dual power supply system provides working voltage for the subsequent working circuit.

When a fault occurs, the first power conversion circuit has no output or the voltage drops sharply, the first optocoupler U1 and the fourth optocoupler U4 are cut off, the second optocoupler U2 and the third optocoupler U3 are turned on, and the control sent by the detection circuit The signal CTR is low level, the light-emitting diode D1 lights up, and there is no turn-on voltage between the gate and drain of the field effect transistor n-MOS, so the drain and source of the field effect transistor n-MOS are cut off, that is, on-off control The circuit is in the disconnected state, and the power supply in the dual power supply system stops supplying power to the subsequent working circuit. At this time, the second triode VD2 is turned on, and the pull-up voltage Vcc of the second triode VD2 passes through the third The current-limiting resistor r3 charges the capacitor C. When the voltage on the capacitor C reaches a certain value, the first triode VD1 is turned on. At this time, the gate voltage of the field effect transistor n-MOS is always clamped at a low level, and the failure Status is locked. At this time, even if the control signal CTR suddenly changes to a high level because the system is immediately powered on again, the on-off control circuit cannot be turned on, so it will not cause damage to the working circuit of the subsequent stage.

In addition, due to the existence of the capacitor charging time, there is no response to interference signals such as burrs in the control signal CTR, and the stability of the system is enhanced. When the system is working normally, the control signal CTR is always at a high level. At this time, if the interference signal on the space or the line enters the system, since the energy of the interference signal is generally small, the interference generation time is relatively short, so in the line control signal CTR There may be a negative pulse interference signal, causing the control signal CTR to drop from high level to low level in a short time, but it quickly returns to high level. At this time, due to the existence of the capacitor charging time, the control signal CTR becomes When it is low level, the second transistor VD2 starts to conduct and charge the capacitor C, but when the capacitor voltage is not charged enough to make the first transistor VD1 conduct, the control signal CTR changes from low level to high Level, the second triode VD2 cuts off, at this time the on-off control circuit has no protection action, and this interference signal can be ignored, thus enhancing the stability and reliability of the system.

Similarly, when the second power conversion circuit has no output or the voltage drops sharply, the second optocoupler U2 and the third optocoupler U3 are turned off, the first optocoupler U1 and the fourth optocoupler U4 are turned on, and the control signal sent by the detection circuit When CTR is at low level, the on-off control circuit is in a disconnected state and remains in a fault state, and the light-emitting diode D1 is lit.

Through the description of the specific implementation mode, the technical means and effects of the utility model to achieve the intended purpose can be understood more deeply and specifically, but the accompanying drawings are only for reference and description, and are not used to explain the utility model. new restrictions.

Claims (10)

1. A post-stage working circuit protection device for a dual power supply system, characterized in that it includes an on-off control circuit and a detection circuit; The detection circuit is connected to the output terminals of the two power conversion circuits, respectively detects the working states of the two power conversion circuits, and outputs corresponding control signals to the on-off control circuit according to the detection results; The on-off control circuit is connected between the power supply and the two power conversion circuits, and controls the on-off relationship between the power supply and the two power conversion circuits according to the control signal output by the detection circuit; During initial power-on and normal operation, the detection circuit outputs a control signal in a normal state, and the on-off control circuit connects the power supply and the two power conversion circuits; when any one of the two power conversion circuits fails, the The detection circuit outputs a control signal of a fault state, and the on-off control circuit shuts off the connection between the power supply and the two power conversion circuits. 2. The rear-stage working circuit protection device of the dual power supply system according to claim 1, wherein the power supply adopts direct current, and the detection circuit and the on-off control circuit are directly powered by the power supply; The detection circuit includes a first power output circuit, a second power output circuit and a comparison circuit, and the first power output circuit includes a first resistor (R1), a second resistor (R2), a first optocoupler (U1) and a first reference voltage module, the second power supply output circuit includes a third resistor (R3), a fourth resistor (R4), a second optocoupler (U2) and a second reference voltage module, and the comparison circuit includes a third Optocoupler (U3), fourth optocoupler (U4), fifth resistor (R5), sixth resistor (R6), seventh resistor (R7) and light-emitting diode (D1); The positive output terminal (V1+) of the first power conversion circuit is connected to the positive terminal of the input side of the first optocoupler (U1) through the first resistor (R1), and the negative terminal of the input side of the first optocoupler (U1) is connected to the first The positive terminal of the reference voltage module, the negative terminal of the first reference voltage module is connected to the negative output terminal (V1-) of the first power conversion circuit, and the positive output terminal (V2+) of the second power conversion circuit is connected to the third resistor (R3) To the positive terminal of the input side of the second optocoupler (U2), the negative terminal of the input side of the second optocoupler (U2) is connected to the positive terminal of the second reference voltage module, and the negative terminal of the second reference voltage module is connected to the second power conversion The output negative terminal of the circuit (V2-); The positive terminals on the output side of the first optocoupler (U1) and the second optocoupler (U2) are respectively connected to the power supply (Vi) through the first resistor (R2) and the fourth resistor (R4). The first optocoupler (U1) And the negative end of the output side of the second optocoupler (U2) is connected to the GND end of the power supply (Vi); the positive end of the output side of the first optocoupler (U1) is connected to the input side of the third optocoupler (U3) at the same time The positive terminal and the negative terminal on the input side of the fourth optocoupler (U4), and the positive terminal on the output side of the second optocoupler (U2) are simultaneously connected to the negative terminal on the input side of the third optocoupler (U3) and the fourth optocoupler (U4) The positive end of the input side; the positive end of the output side of the third optocoupler (U3) and the fourth optocoupler (U4) are respectively connected to the power supply (Vi) through the fifth resistor (R5) and the sixth resistor (R6), while The positive end of the output side of the third optocoupler (U3) is connected to the positive end of the output side of the fourth optocoupler (U4), and the negative end of the output side of the third optocoupler (U3) and the fourth optocoupler (U4) are connected at the same time Connect to the GND terminal of the power supply (Vi); the positive terminal of the light-emitting diode (D1) is connected to the power supply (Vi) through the seventh resistor (R7), and the negative terminal of the light-emitting diode (D1) is connected to the on-off control circuit signal input. 3. The rear-stage working circuit protection device of the dual power supply system according to claim 1, wherein the power supply adopts alternating current, and the power supply of the detection circuit and the on-off control circuit is provided by the starting power supply ( Vs) is provided after converting the AC voltage into a low-voltage DC power supply, and the starting power supply (Vs) is connected across the power supply. 4. The protection device for the subsequent working circuit of the dual power supply system according to claim 3, wherein the detection circuit includes a first power output circuit, a second power output circuit and a comparison circuit, and the first A power output circuit includes a first resistor (R1), a second resistor (R2), a first optocoupler (U1) and a first reference voltage module, and the second power output circuit includes a third resistor (R3), a fourth A resistor (R4), a second optocoupler (U2) and a second reference voltage module, the comparison circuit includes a third optocoupler (U3), a fourth optocoupler (U4), a fifth resistor (R5), a sixth resistor (R6), the seventh resistor (R7) and light emitting diode (D1); The positive output terminal (V1+) of the first power conversion circuit is connected to the positive terminal of the input side of the first optocoupler (U1) through the first resistor (R1), and the negative terminal of the input side of the first optocoupler (U1) is connected to the first The positive terminal of the reference voltage module, the negative terminal of the first reference voltage module is connected to the negative output terminal (V1-) of the first power conversion circuit, and the positive output terminal (V2+) of the second power conversion circuit is connected to the third resistor (R3) To the positive terminal of the input side of the second optocoupler (U2), the negative terminal of the input side of the second optocoupler (U2) is connected to the positive terminal of the second reference voltage module, and the negative terminal of the second reference voltage module is connected to the second power conversion The output negative terminal of the circuit (V2-); The positive terminals on the output side of the first optocoupler (U1) and the second optocoupler (U2) are respectively connected to the starting power supply (Vs) through the first resistor (R2) and the fourth resistor (R4). The first optocoupler (U1) And the negative end of the output side of the second optocoupler (U2) is connected to the GND end of the startup power supply (Vs); the positive end of the output side of the first optocoupler (U1) is connected to the input side of the third optocoupler (U3) at the same time The positive terminal and the negative terminal on the input side of the fourth optocoupler (U4), and the positive terminal on the output side of the second optocoupler (U2) are simultaneously connected to the negative terminal on the input side of the third optocoupler (U3) and the fourth optocoupler (U4) The positive end of the input side; the positive end of the output side of the third optocoupler (U3) and the fourth optocoupler (U4) are respectively connected to the starting power supply (Vs) through the fifth resistor (R5) and the sixth resistor (R6), and at the same time The positive end of the output side of the third optocoupler (U3) is connected to the positive end of the output side of the fourth optocoupler (U4), and the negative end of the output side of the third optocoupler (U3) and the fourth optocoupler (U4) are connected at the same time Connect to the GND terminal of the starting power supply (Vs); the positive terminal of the light-emitting diode (D1) is connected to the starting power supply (Vs) through the seventh resistor (R7), and the negative terminal of the light-emitting diode (D1) is connected to the on-off control circuit signal input. 5. The protection device for the subsequent working circuit of the dual power supply system according to claim 2, wherein the reference voltage module uses a voltage regulator tube or a TL431 chip module to provide the reference voltage. 6. The protective device for the subsequent working circuit of the dual power supply system according to claim 4, wherein the reference voltage module uses a Zener tube or a TL431 chip module to provide the reference voltage. 7. The protection device for the post-stage working circuit of the dual power supply system according to any one of claims 1 to 6, wherein the on-off control circuit includes a switch module and a fault state maintenance module; The fault state holding module includes a first triode (VD1), a second triode (VD2), a first current limiting resistor (r1), a second current limiting resistor (r2), a third current limiting resistor (r3 ) and capacitance (C), the first current limiting resistor (r1) is connected to the collector of the first triode (VD1), the base of the second triode (VD2) and the on-off The base of the control transistor (VD3) is connected, the base of the first transistor (VD1) is connected to the collector of the second transistor (VD2) through the second current limiting resistor (r2), The collector of the second triode (VD2) is grounded through the series branch composed of the third current limiting resistor (r3) and the capacitor (C), and the emitter of the first triode (VD1) The pole is also grounded, the collector of the on-off control transistor (VD3) is connected to the supply voltage (Vi), and the emitter of the on-off control transistor (VD3) is connected to the input terminal (Vout) of the power conversion circuit. 8. The protection device for the subsequent working circuit of the dual power supply system according to claim 7, characterized in that the switch module adopts an on-off triode (VD3). 9. The protection device for the subsequent working circuit of the dual-circuit power supply system according to claim 7, wherein the switch module adopts a normally closed electromagnetic relay. 10. The protection device for the subsequent working circuit of the dual power supply system according to claim 7, characterized in that the switching module adopts a field effect transistor (MOSFET).

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