CN201167229Y - Overload protection and power-off detection of multiple high-speed pulse output circuits - Google Patents

Abstract

The utility model provides a protection circuit for a high-speed pulse output circuit, comprising: a pulse output circuit, which generates a pulse signal under the control of a controller and outputs the pulse signal to the first end of the load; a detection circuit, connected to the second end of the load terminal and the two ends of the first power supply, for detecting the state of the load and the first power supply and outputting the detection signal to the controller; and the controller, connected to the pulse output circuit and the detection circuit, for responding to the detection signal from the detection circuit The output of the pulse signal of the pulse output circuit is enabled or disabled.

Description

Overload protection and power-off detection of multiple high-speed pulse output circuits

technical field

The utility model relates to a single-channel and multi-channel digital quantity pulse output device in an industrial control system, specifically referring to the load current and the output side 24V of the single-channel and multi-channel digital quantity pulse output circuit in the industrial control system. The status of the power supply is detected in real time and the output can be stopped in case of overload and power failure, so as to realize the protection of the output circuit.

Background technique

In the transistor pulse output module of the industrial control system, the transistor is often used in the interface circuit to drive the load, but when the load current exceeds the rated parameters of the transistor or the load is short-circuited to the power supply, the output transistor will be damaged due to excessive current and cause product failure , in order to avoid such failures, the user has to connect a fuse with an appropriate current in series in the load circuit to protect the output circuit.

FIG. 1 shows a typical circuit structure of multi-channel digital pulse output in the prior art.

In Figure 1, the output of the pulse is connected to a load and connected to the 24V power supply through insurance. When the output load is over-current or short-circuit fault occurs, the current flowing through the output transistor will increase rapidly. When it exceeds the rated value of the external fuse value, the fuse blows, thereby protecting the transistor from damage.

According to the above-mentioned Fig. 1, it can be seen that the circuit of the prior art has the following disadvantages: each output has to add a fuse, the application cost is high, and if the fuse is soldered to the printed board, the maintenance cost is higher. There is no feedback for load overcurrent or short circuit, and the CPU cannot detect this fault.

FIG. 2 shows the load circuit diagram in FIG. 1 . As shown in FIG. 2 , the circuit structures of load 1 to load N are the same. The entire circuit structure in Figure 2 is the internal circuit representing the load.

Utility model content

Additional aspects and advantages of the utility model will be set forth in part in the description which follows, and in part will be apparent from the description, or can be obtained by practice of the utility model.

Aiming at the problems mentioned above in the prior art circuit, the utility model is proposed. The utility model can realize the functions of overload and short circuit protection and power failure detection of the output side under the condition of 200KHz frequency output.

It is composed of pulse drive and detection control circuit. When overload, short circuit and power failure occurs, the circuit can cut off the physical connection with the external load in time without adding a fuse.

The invention provides a protection circuit for a high-speed pulse output circuit, comprising: a pulse output circuit, which generates a pulse signal under the control of a controller and outputs the pulse signal to the first end of the load; a detection circuit, connected to the second end of the load and the two ends of the first power supply, used to detect the state of the load and the first power supply and output the detection signal to the controller; and the controller, connected to the pulse output circuit and the detection circuit, for responding to the detection signal from the detection circuit Enables or disables the output of the pulse signal of the pulse output circuit.

According to the utility model, the circuit design is simple, and only a few resistors and small signal transistors are needed to realize power failure detection and multi-channel signal overload and short circuit protection, which is cheap and convenient for users to use.

Description of drawings

The above-mentioned and other objects, characteristics and advantages of the present invention will become clearer by describing preferred embodiments of the present invention in detail with reference to the accompanying drawings, wherein the same reference numerals designate units of the same structure, and wherein:

Fig. 1 shows the typical circuit structure of the multi-channel digital quantity pulse output of prior art;

Fig. 2 shows the load circuit diagram in Fig. 1;

Fig. 3 shows a circuit diagram of a multi-channel digital pulse output in an exemplary embodiment of the present invention.

Detailed ways

The utility model will be fully described below with reference to the accompanying drawings showing embodiments of the utility model. However, the invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, components are exaggerated for clarity.

Fig. 3 shows a circuit diagram of a multi-channel digital pulse output in an exemplary embodiment of the present invention.

As shown in Figure 3, the multi-channel digital pulse output circuit of the present invention includes: a pulse output circuit 110, which generates a pulse signal under the control of a controller and outputs the pulse signal to the first end of the load; a detection circuit 130, which is connected to The second end of the load and the two ends of the first power supply are used to detect the state of the load and the first power supply and output a detection signal to the controller; and the controller 120 is connected to the pulse output circuit and the detection circuit for responding to The detection signal of the detection circuit enables or disables the output of the pulse signal of the pulse output circuit.

As shown in FIG. 3 , the detection circuit 130 further includes a power detection circuit 131 for detecting power failure. The following will describe in conjunction with a specific circuit structure.

●Realization of pulse output

The pulse output circuit 110 includes: a frequency generator, an optocoupler 1 and a MOSFET T1. The frequency generator outputs the pulse signal to the load 1 through the optocoupler 1 through the MOSFET.

The frequency generator is composed of a piece of CPLD. It first receives the pulse output by the controller 120, and internally processes it to convert it into a frequency pulse of 1-200KHZ. The controller 120 decides whether to output the pulse to the optocoupler.

Take channel 1 as an example. Under normal circumstances, the output MOSFET T1 of channel 1 is not turned on, and the detection signal, that is, the output of optocoupler 2 is at 1 level. The internal 3.3V is turned on. At this time, as long as the frequency generator has a pulse output, the high-speed optocoupler 1 will output pulses to the load 1 through the MOSFET.

●Realization of overload and short circuit detection and protection

The maximum current value of the output circuit is limited to about 1A {(5V-Vgs)/2Ohm, Vgs=2.5～3V}.

The detection circuit 130 includes: a power detection circuit 131 , a resistor R1 , a transistor T2 and an optocoupler 2 . Resistor R1 is connected between the drain of T1 and ground. The base and emitter of T2 are connected to both ends of R1 , and the collector of T2 is connected to the power detection circuit 131 . The other end of the power detection circuit 131 is connected to the positive pole of the power supply. Both ends of the light emitting diode of the optocoupler 2 are connected to the emitter and collector of T2 , and the output end of the optocoupler 2 is connected to the controller 120 .

The controller 120 includes a processor and an AND circuit. The processor can be realized by, for example, an XCEL or a dedicated ASIC controller. The frequency generator determines whether to output the pulse to the frequency generator by detecting the command XCEL of the XCEL IO pin. Those skilled in the art should understand that the controller of the present invention is not limited to the processor and AND circuit disclosed here, and can also be realized by using other single-chip microcomputers with the same function.

When the output transistor T1 of channel 1 is turned on, the load current passes through T1 and resistor R1 to the ground. When the impedance of load 1 becomes smaller or the load is short-circuited, the current I1 flowing through R1 increases rapidly. When the current reaches or exceeds 0.35 When A, the voltage on the resistor R1 reaches or exceeds 0.7V, the transistor T2 is turned on and becomes 0 level, and the current flowing through the optocoupler 2 is bypassed to the ground, and the output of the optocoupler 2 becomes 0 level, by The 0-level detection signal is detected once by XCEL, and at the same time, the 0-level detection signal cuts off the power supply of the optocoupler 1 through the circuit, so that the output is turned off. This action makes the detection signal return to 1 state, until XCEL enables the output pulse again, waiting for the next overload or short circuit detection.

After XCEL detects four consecutive 0-level detection signals, it turns off all outputs. After XCEL detects four consecutive 0-level detection signals, XCEL generates a 0-level enable flag signal, and outputs the 0-level enable flag signal through the output terminal ②, thereby turning off all outputs

●Detection of 24V power failure

As shown in the figure, resistors R2, R3, R4, R5 and transistor T3 form a 24V power supply detection circuit 131. When the 24V power supply is powered off, the current flowing through the optocoupler 2 decreases to 0, and the output of the optocoupler 2 It also becomes 0 level, XCEL detects this 0 level detection signal, repeats the process as described above, after 4 times, XCEL judges that the IO side power supply is powered off (or there is a problem with the load) and uses the same overload and short circuit detection as above way to turn off the output.

●Detection and protection of multi-channel output

As shown in Figure 3, the overload or short circuit detection of all channels are connected together to form a NOR circuit through transistors T2 to Tn in an open-collector manner, any channel overload or short circuit will bypass the IF current of optocoupler 2 to ground, so that optocoupler 2 outputs a 0-level detection signal to XCEL, so that all channels realize overload detection and protection through optocoupler 2.

The circuit design of the utility model is simple, and only a few resistors and small-signal transistors are needed to realize power failure detection and multi-channel signal overload and short-circuit protection.

Although the present invention has been described with reference to certain preferred embodiments thereof, those skilled in the art will appreciate that modifications may be made thereto without departing from the spirit and scope of the present invention as defined by the appended claims. Various modifications of form and detail.

Claims (17)

1. A protection circuit for a high-speed pulse output circuit, comprising: A pulse output circuit generates a pulse signal under the control of the controller and outputs the pulse signal to the first end of the load; A detection circuit, connected to the second end of the load and the two ends of the first power supply, for detecting the state of the load and the first power supply and outputting a detection signal to the controller; and The controller, connected to the pulse output circuit and the detection circuit, is used to enable or disable the output of the pulse signal of the pulse output circuit in response to the detection signal from the detection circuit. 2. The protection circuit as claimed in claim 1, wherein the pulse output circuit comprises: A frequency generator, connected to the controller, converts the pulse output by the controller into a pulse signal with a predetermined frequency; The first optocoupler is connected to the frequency generator and the controller, and outputs a pulse signal to the load through the first transistor in response to the second detection signal from the controller; and The first transistor has a gate connected to the first optocoupler and a source connected to the first terminal of the load, and is used for outputting the pulse signal to the load. 3. The protection circuit of claim 2, wherein the detection circuit comprises: a first resistor connected to the drain of the first transistor and ground; a second transistor having a base connected to the first resistor, and an emitter connected to ground; The second optocoupler, the two ends of the light-emitting diode of the second optocoupler are respectively connected to the collector of the second transistor and the ground, and have an output terminal connected to the controller. 4. The protection circuit according to claim 3, when the impedance of the load becomes smaller or the load is short-circuited, the second transistor is turned on to bypass the current flowing through the second optocoupler to ground, and the second optocoupler connects the first The detection signal is output to the controller. 5. The protection circuit according to claim 4, wherein said detection circuit further comprises a power detection circuit comprising a second resistor, a third resistor, a fourth resistor, a fifth resistor and a third resistor transistor, the first end of the second resistor is connected to the second end of the load, the second end of the second resistor is connected to the first end of the third resistor, and the second end of the third resistor is connected to the third transistor the collector of the third transistor, the base of the third transistor is connected to the second power supply through the fifth resistor, and the emitter of the third transistor is connected to the node between the collector of the second transistor and the second optocoupler through the fourth resistor. 6. The protection circuit according to claim 5, when the first power supply is powered off, the second optocoupler outputs the first detection signal to the controller. 7. The protection circuit of claim 6, the controller disables the output of the pulse signal of the pulse output circuit in response to the first detection signal from the second photocoupler. 8. The protection circuit as claimed in claim 7, wherein the controller comprises a processor and an AND circuit, and the AND circuit receives the enable flag signal output by the processor and the detection signal output by the second optocoupler, The output terminal of the AND circuit is connected with the first optocoupler to turn on or off the first optocoupler. 9. The protection circuit according to claim 8, the detection signal output by the second optocoupler is also output to the processor. 10. The protection circuit according to claim 9, when the first detection signal output by the second optocoupler is turned off, the first transistor is turned off, and the detection signal output by the second optocoupler returns to an active state. 11. The protection circuit according to claim 10, when the processor detects four consecutive first detection signals from the second optocoupler, the processor sets the enable flag signal to 0, thereby cutting off all pulse signals Output. 12. The protection circuit according to claim 11, wherein the first power supply is 24V, and the second power supply is 5V. 13. The protection circuit of claim 12, wherein the first detection signal is a detection signal having a level 0, and the second detection signal is a detection signal having a level 1. 14. The protection circuit of claim 13, wherein the first resistor is 2 ohms. 15. The protection circuit of claim 14, wherein the first transistor is a MOSFET. 16. The protection circuit of claim 15, the high-speed pulse output circuit may include multiple outputs. 17. The protection circuit as claimed in claim 16, said multi-channel high-speed pulse output circuit further comprising a plurality of second transistors, a plurality of first transistors and a plurality of first resistors, and a plurality of second transistors are open-collector are connected together to form a NOR circuit, and the first resistor of the previous stage is connected to the source of the first transistor of the next stage.

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