CN213240401U - Load detection circuit and system - Google Patents
Load detection circuit and system Download PDFInfo
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- CN213240401U CN213240401U CN202022235586.3U CN202022235586U CN213240401U CN 213240401 U CN213240401 U CN 213240401U CN 202022235586 U CN202022235586 U CN 202022235586U CN 213240401 U CN213240401 U CN 213240401U
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Abstract
The application provides a load detection circuit and system, and relates to the field of load detection. The load detection circuit includes: the control end of the first switch unit is connected with the output end of the processor, and the input end of the first switch unit is connected with the anode of the first power supply through a load; the input end of the open circuit detection unit is connected with the input end of the first switch unit, and the output end of the open circuit detection unit is connected with the input end of the processor; the input end of the short-circuit detection unit is connected with the output end of the first switch unit, and the output end of the short-circuit detection unit is connected with the input end of the processor; a stream detection unit; the open circuit detection unit is used for outputting a corresponding open circuit detection signal to the processor according to the level signal of the input end of the first switch unit, and the short circuit detection unit is used for outputting a corresponding short circuit detection signal to the processor according to the level signal of the output end of the first switch unit. Through the arrangement, the accurate detection of the open circuit and the short circuit of the load can be realized, and the reliability of the detection is improved.
Description
Technical Field
The present application relates to the field of load detection, and in particular, to a load detection circuit and system.
Background
In the prior art, an LED load state detection circuit of a common constant voltage dimming power supply performs open circuit detection and short circuit detection through a voltage signal at an output terminal of a switching device. When the load is small (such as less than or equal to 5% of rated load), the voltage signal at the output end of the switching device is very low, the voltage signal is lower than the reference voltage of the voltage comparator (the reference voltage cannot be infinitely low because the comparator device has offset voltage characteristics), the output end of the voltage comparator does not have high-level output, the processor does not detect the high-level signal, the LED load is judged to be open by mistake, and when the load current is large, the current detection resistance loss is large, the temperature is increased, and the detection reliability of the load detection circuit is low.
SUMMERY OF THE UTILITY MODEL
It is an object of the present application to provide a load detection circuit and system that ameliorates the problems of the prior art.
The application provides a technical scheme:
in a first aspect, an embodiment of the present application provides a load detection circuit, including:
the control end of the first switch unit is connected with the output end of the processor, and the input end of the first switch unit is connected with the anode of the first power supply through a load;
the input end of the open circuit detection unit is connected with the input end of the first switch unit, the output end of the open circuit detection unit is connected with the input end of the processor, the anode of the open circuit detection unit is connected with the second power supply, and the cathode of the open circuit detection unit is grounded;
the input end of the short-circuit detection unit is connected with the output end of the first switch unit, the output end of the short-circuit detection unit is connected with the input end of the processor, the positive electrode of the short-circuit detection unit is connected with the third power supply, and the negative electrode of the short-circuit detection unit is grounded;
a current detection unit, wherein the first end of the current detection unit is connected with the output end of the first switch unit, and the second end of the current detection unit is connected with the negative electrode of the first power supply;
the open circuit detection unit is used for outputting a corresponding open circuit detection signal to the processor according to the level signal of the input end of the first switch unit, and the short circuit detection unit is used for outputting a corresponding short circuit detection signal to the processor according to the level signal of the output end of the first switch unit.
In an alternative embodiment, the open circuit detection unit includes:
and the non-inverting input end of the first voltage comparator is connected with the input end of the first switch unit, the inverting input end of the first voltage comparator is connected with a first preset signal source, the positive electrode of the first voltage comparator is connected with the second power supply, and the negative electrode of the first voltage comparator is grounded.
In an alternative embodiment, the short detection unit comprises:
and the inverting input end of the second voltage comparator is connected with the output end of the first switch unit, the non-inverting input end of the second voltage comparator is connected with a second preset signal source, the positive electrode of the second voltage comparator is connected with the third power supply, and the negative electrode of the second voltage comparator is grounded.
In an alternative embodiment, the streaming unit includes:
and the first end of the first resistor is connected with the output end of the first switch unit, and the second end of the first resistor is connected with the negative electrode of the first power supply.
In an optional embodiment, the open circuit detection unit further includes:
a second resistor, a first end of which is connected with the input end of the first switch unit, and a second end of which is connected with the non-inverting input end of the first voltage comparator;
a third resistor, a first end of which is connected with the second power supply and a second end of which is connected with the output end of the first voltage comparator;
and the anode of the first diode is connected with the output end of the first voltage comparator, and the cathode of the first diode is connected with the input end of the processor.
In an optional embodiment, the open circuit detection unit further includes:
a fourth resistor, a first end of which is connected with the cathode of the first diode and a second end of which is grounded;
and a first end of the first capacitor is connected with the cathode of the first diode, and a second end of the first capacitor is grounded.
In an optional embodiment, the short circuit detection unit further includes:
a fifth resistor, a first end of which is connected to the output end of the first switching unit and a second end of which is connected to the inverting input end of the second voltage comparator;
a first end of the second capacitor is connected with the second end of the fifth resistor, and a second end of the second capacitor is grounded;
and a first end of the sixth resistor is connected with the third power supply, and a second end of the sixth resistor is connected with the output end of the second voltage comparator.
In an optional embodiment, the short circuit detection unit further includes:
a first end of the seventh resistor is connected with the output end of the second voltage comparator, and a second end of the seventh resistor is grounded;
and the first end of the third capacitor is connected with the output end of the second voltage comparator, and the second end of the third capacitor is grounded.
In an alternative embodiment, the first switching unit includes:
and the grid electrode of the first MOS tube is connected with the output end of the processor, the drain electrode of the first MOS tube is connected with the anode of the first power supply through the load, and the source electrode of the first MOS tube is connected with the cathode of the first power supply through the current detection unit.
In a second aspect, an embodiment of the present application provides a load detection system, including:
a processor;
the load detection circuit of any one of the preceding embodiments;
the processor is connected with the load detection circuit and used for receiving the open-circuit detection signal and the short-circuit detection signal sent by the load detection circuit so as to detect the load.
The beneficial effects of the load detection circuit and the system that this application provided are: the open circuit detection unit and the short circuit detection unit are respectively connected with the input end and the output end of the first switch unit, so that the accurate detection of the open circuit and the short circuit of the load can be realized, the open circuit detection and the short circuit detection of the voltage signal at the output end of the switch device in the prior art are avoided, and the problems that when the load is very small, the processor does not detect a high-level signal, the LED load is misjudged to be open circuit, and when the load current is large, the current detection resistance loss is large, the temperature is high, and the reliability of the load detection is low are caused.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are required to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained from the drawings without inventive effort.
Fig. 1 is a schematic structural diagram of a load detection circuit provided in the prior art.
Fig. 2 is a schematic structural diagram of a load detection system according to an embodiment of the present application.
Fig. 3 is a schematic circuit diagram of a load detection system according to an embodiment of the present application.
Fig. 4 is a schematic structural diagram of a load detection circuit according to an embodiment of the present application.
Fig. 5 is a waveform diagram of a load detection circuit according to an embodiment of the present application.
Fig. 6 is another waveform diagram of a load detection circuit according to an embodiment of the present application.
Fig. 7 is another waveform diagram of a load detection circuit according to an embodiment of the present application.
Fig. 8 is another waveform diagram of a load detection circuit according to an embodiment of the present application.
Fig. 9 is another waveform diagram of a load detection circuit according to an embodiment of the present application.
Fig. 10 is another waveform diagram of a load detection circuit according to an embodiment of the present application.
Fig. 11 is another schematic structural diagram of a load detection circuit according to an embodiment of the present application.
Icon: 10-a load detection system; 100-a load detection circuit; 110-a first switching unit; 120-open circuit detection unit; 130-short circuit detection unit; 140-a streaming unit; 200-a processor; u1 — first voltage comparator; u2 — second voltage comparator; r1 — first resistance; r2 — second resistance; r3 — third resistance; r4-fourth resistor; r5-fifth resistor; r6-sixth resistance; r7 — seventh resistor; c1 — first capacitance; c2 — second capacitance; c3 — third capacitance; v1 — first power supply; v2 — second power supply; v3 — third power supply; q1-first MOS tube.
Detailed Description
In the prior art, fig. 1 shows a conventional LED load state detection circuit of a constant voltage dimming power supply, which can detect an open circuit and a short circuit of an LED load. A MOS tube Q2 and a current detection resistor R24 are connected in series in a circuit that a constant voltage power supply outputs to an LED load, and a PWM signal is controlled by an MCU to drive a Q2 switch to realize a dimming function. When the LED load is in normal work, load current flows through a current detection resistor R24, a pulsating voltage drop A is generated on R24, a pulsating voltage signal is filtered and converted into a direct current level B, and then the direct current level B is sent to the positive end of a comparator to be compared with reference voltages VREF1 and VREF2 of the negative end, at the moment, the level of a point B of VREF2 is more than that of VREF1, the high level signal is output at the point C of the output end, the point C signal is sent to an MCU as a load open circuit state detection signal to be detected, and the MCU detects the high level signal, so that the LED load is. When the load is in an open circuit, no current flows through the current detection resistor R24, the signal at the point C is in a low level, the MCU detects the low level signal within a certain settable short time, the LED load is judged to be in an open circuit, and a related instruction is sent to inform a user at the moment. If the load is in short circuit in operation, the current flowing through the current detection resistor R24 is very large, the level of the point B is greater than VREF2, a high-level signal is output at the point D, and the MCU detects the high-level signal of the point D within a certain settable short time, so that the LED load is judged to be in short circuit.
The main disadvantages of the above circuit are:
1. the load current generates power loss through R24, reduces power conversion efficiency, generates considerable heat to influence the temperature rise of the whole machine and reduces reliability.
2. When the load is light (such as ≦ 5% rated load), the voltage drop generated by the output current on R24 is very low, and the voltage signal at point B is very low, and unless the resistance of R24 is large enough (but when it is too large, the full load loss will be larger and the resistor may be burned), the voltage signal will be lower than the comparator reference voltage VREF1 (the reference voltage cannot be infinitely low because the comparator device itself has offset voltage characteristics), and at this time, no high level output is provided at point C, and the MCU does not detect a high level signal, which results in a false determination that the LED load is open.
In order to improve at least one of the above technical problems addressed by the present application, embodiments of the present application provide a load detection circuit and system, and the following describes a technical solution of the present application through possible implementations.
The defects of the above solutions are the results of the inventor after practice and careful study, and therefore, the discovery process of the above problems and the solution proposed by the present application to the above problems should be the contribution of the inventor to the present application in the process of the present application.
In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are some embodiments of the present application, but not all embodiments. The components of the embodiments of the present application, generally described and illustrated in the figures herein, can be arranged and designed in a wide variety of different configurations.
Thus, the following detailed description of the embodiments of the present application, presented in the accompanying drawings, is not intended to limit the scope of the claimed application, but is merely representative of selected embodiments of the application. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures. In the description of the present application, the terms "first," "second," "third," and the like are used solely to distinguish one from another and are not to be construed as indicating or implying relative importance.
In the description of the present application, it is further noted that, unless expressly stated or limited otherwise, the terms "disposed," "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present application can be understood in a specific case by those of ordinary skill in the art.
As shown in fig. 2, the present embodiment provides a load detection system 10 for performing load detection. The load detection system 10 may include, among other things, a load detection circuit 100 and a processor 200.
In detail, the processor 200 is connected to the load detection circuit 100, and is configured to receive the open circuit detection signal and the short circuit detection signal sent by the load detection circuit 100 for load detection. Also, the processor 200 may control the load detection circuit 100 through the PWM drive control circuit after receiving the open detection signal and the short detection signal.
For the processor 200, it should be noted that the specific type of the processor 200 is not limited, and may be set according to the actual application requirement. For example, in one alternative example, processor 200 may include one or more processing cores (e.g., a single-core processor (S) or a multi-core processor (S)). Merely by way of example, Processor 200 may include a Central Processing Unit (CPU), an Application Specific Integrated Circuit (ASIC), an Application Specific Instruction Set Processor (ASIP), a Graphics Processing Unit (GPU), a Physical Processing Unit (PPU), a Digital Signal Processor (DSP), a Field Programmable Gate Array (FPGA), a Programmable Logic Device (PLD), a controller, a microcontroller Unit, a Reduced Instruction Set computer (Reduced Instruction Set computer) or a microprocessor, or the like, or any combination thereof.
For the load detection circuit 100, it should be noted that the specific structure of the load detection circuit 100 is not limited, and may be set according to the actual application requirement. For example, in an alternative example, in conjunction with fig. 3, the load detection circuit 100 may include a first switching unit 110, an open detection unit 120, a short detection unit 130, and a current detection unit 140.
In detail, the control terminal of the first switching unit 110 is connected to the output terminal of the processor 200, and the input terminal is connected to the positive electrode of the first power source V1 through a load. The open circuit detecting unit 120 has an input terminal connected to the input terminal of the first switching unit 110, an output terminal connected to the input terminal of the processor 200, an anode connected to the second power source V2, and a cathode grounded. The input terminal of the short-circuit detection unit 130 is connected to the output terminal of the first switch unit 110, the output terminal thereof is connected to the input terminal of the processor 200, the positive terminal thereof is connected to the third power supply V3, and the negative terminal thereof is grounded. The current detecting unit 140 has a first terminal connected to the output terminal of the first switching unit 110, and a second terminal connected to the negative terminal of the first power source V1.
The open circuit detecting unit 120 is configured to output a corresponding open circuit detecting signal to the processor 200 according to the level signal at the input end of the first switch unit 110, and the short circuit detecting unit 130 is configured to output a corresponding short circuit detecting signal to the processor 200 according to the level signal at the output end of the first switch unit 110.
Through the setting, open circuit detecting element and short circuit detecting element are connected with the input and the output of first switch element respectively, can realize opening a way the accurate detection with the short circuit to the load, have avoided among the prior art voltage signal through the switching device output to carry out open circuit and short circuit detection, have when the load is very little, the treater does not detect high level signal, misjudge the LED load and open a way to and the current detection resistance loss is big when load current is great, the temperature risees, the problem that the reliability of the load detection that leads to is low.
For the first power source V1, the second power source V2, and the third power source V3, it should be noted that the specific types of the first power source V1, the second power source V2, and the third power source V3 are not limited, and may be set according to the actual application requirements, and may be the same type or different types. In the embodiment of the present application, the first power source V1 is a constant voltage power source, and the load is an LED load.
For the first switch unit 110, it should be noted that the specific composition of the first switch unit 110 is not limited, and may be set according to the actual application requirement. For example, in an alternative example, the first switching unit 110 may include a first MOS transistor Q1, a gate of the first MOS transistor Q1 is connected to the output terminal of the processor 200, a drain of the first MOS transistor Q1 is connected to the positive pole of the first power source V1 through the load, and a source of the first MOS transistor Q1 is connected to the negative pole of the first power source V1 through the current detecting unit 140.
As for the stream checking unit 140, it should be noted that the specific composition of the stream checking unit 140 is not limited, and may be set according to the actual application requirement. For example, in an alternative example, the current detecting unit 140 may include a first resistor R1, a first terminal of the first resistor R1 is connected to the output terminal of the first switching unit 110, and a second terminal is connected to the negative terminal of the first power source V1.
For the open circuit detecting unit 120, it should be noted that the specific composition of the open circuit detecting unit 120 is not limited, and may be set according to the actual application requirement. For example, in an alternative example, the open circuit detecting unit 120 may include a first voltage comparator U1, a non-inverting input terminal of the first voltage comparator U1 is connected to the input terminal of the first switching unit 110, an inverting input terminal thereof is connected to the first preset signal source, an anode thereof is connected to the second power source V2, and a cathode thereof is grounded.
Further, in the embodiment of the present application, the open circuit detecting unit 120 may further include a second resistor R2, a third resistor R3, and a first diode D1. In detail, a first terminal of the second resistor R2 is connected to the input terminal of the first switching unit 110, and a second terminal thereof is connected to the non-inverting input terminal of the first voltage comparator U1, so as to limit the current of the signal inputted from the non-inverting input terminal of the first voltage comparator U1. The third resistor R3 has a first terminal connected to the second power source V2 and a second terminal connected to the output terminal of the first voltage comparator U1, so as to pull up the signal output from the output terminal of the first voltage comparator U1. The anode of the first diode D1 is connected to the output of the first voltage comparator U1, and the cathode is connected to the input of the processor 200 to rectify the signal output from the output of the first voltage comparator U1.
Further, in order to divide and filter the rectified signal at the output terminal of the first voltage comparator U1, the open circuit detecting unit 120 may further include a fourth resistor R4 and a first capacitor C1. In detail, a first end of the fourth resistor R4 is connected to the cathode of the first diode D1, and a second end thereof is grounded, so as to divide the rectified signal at the output end of the first voltage comparator U1. The first end of the first capacitor C1 is connected to the cathode of the first diode D1, and the second end is grounded, so as to filter the signal divided by the output terminal of the first voltage comparator U1.
For the short-circuit detection unit 130, it should be noted that the specific composition of the short-circuit detection unit 130 is not limited, and may be set according to the actual application requirement. For example, in an alternative example, the short detection unit 130 may include a second voltage comparator U2, an inverting input terminal of the second voltage comparator U2 is connected to the output terminal of the first switching unit 110, a non-inverting input terminal thereof is connected to the second preset signal source, an anode thereof is connected to the third power source V3, and a cathode thereof is grounded.
Further, in the embodiment of the present application, the short detection unit 130 may further include a fifth resistor R5, a second capacitor C2, and a sixth resistor R6. In detail, a first end of the fifth resistor R5 is connected to the output end of the first switch unit 110, a second end of the fifth resistor R5 is connected to the inverting input end of the second voltage comparator U2, a first end of the second capacitor C2 is connected to the second end of the fifth resistor R5, the second end of the second capacitor C3526 is grounded, and the fifth resistor R5 and the second capacitor C2 filter a signal output from the output end of the first switch unit 110. The sixth resistor R6 has a first terminal connected to the third power source V3 and a second terminal connected to the output terminal of the second voltage comparator U2, so as to pull up the signal output from the output terminal of the second voltage comparator U2.
Further, in order to divide and filter the signal pulled up by the output terminal of the second voltage comparator U2, the short circuit detection unit 130 may further include a seventh resistor R7 and a third capacitor C3. In detail, a first end of the seventh resistor R7 is connected to the output end of the second voltage comparator U2, and a second end thereof is grounded, so as to divide the signal pulled up by the output end of the second voltage comparator U2. The first end of the third capacitor C3 is connected to the output end of the second voltage comparator U2, and the second end is grounded, so as to filter the signal divided by the output end of the second voltage comparator U2.
It should be noted that specific resistance values of the first resistor R1, the second resistor R2, the third resistor R3, the fourth resistor R4, the fifth resistor R5, the sixth resistor R6, and the seventh resistor R7 are not limited, and may be set according to actual application requirements. For example, in an alternative example, the first resistor R1 may have a resistance of 0.005 Ω, the second resistor R2 may have a resistance of 2k Ω, the third resistor R3 may have a resistance of 1k Ω, the fourth resistor R4 may have a resistance of 4.7k Ω, the fifth resistor R5 may have a resistance of 1k Ω, the sixth resistor R6 may have a resistance of 1k Ω, and the seventh resistor R7 may have a resistance of 4.7k Ω.
It should be noted that specific capacitance values of the first capacitor C1, the second capacitor C2, and the third capacitor C3 are not limited, and may be set according to practical application requirements. For example, in an alternative example, the capacitance value of the first capacitor C1 may be 0.1 μ F, the capacitance value of the second capacitor C2 may be 220pF, and the capacitance value of the third capacitor C3 may be 100 pF.
The load detection circuit provided by the embodiment of the application can accurately detect whether the LED load is open-circuited or short-circuited, and can realize accurate detection in the whole load range. Referring to fig. 4, a first MOS transistor Q1 and a first resistor R1 for current detection are connected in series in a constant voltage power supply output to the LED load loop, and a PWM signal is output through MCU control (point a) to drive Q1, so as to adjust its on-duty ratio to implement a dimming function. When Q1 is turned on, an on-state equivalent impedance RDS1 exists between the drain and the source, and the size of the RDS1 depends on the MOS transistor parameter selection. When Q1 is turned off, there is an off-state equivalent resistance RDS2 between the drain and the source, because only leakage current flows between the drain and the source of Q1, the resistance value of RDS2 is very large. Then there is an equivalent impedance at the drain-source (DS pole) whether Q1 is on or off, which can be referred to as a drain-source equivalent impedance RDS (hereinafter abbreviated as RDS). As can be seen from fig. 4, the RDS and the first resistor R1 are connected in series, and during normal operation, as long as a load current flows through the RDS and R1, voltage drop signals (point B and point E) always exist at both ends of the RDS and R1. Therefore, whether the LED load is open or short can be determined by detecting the voltage drop across the equivalent impedances RDS and R1, so as to implement the load status detection function.
As shown in fig. 4, when detecting the open circuit of the load, the circuit has the following two operation modes during the actual operation:
1. when the load is full load, the duty ratio is 100%, namely Q1 is always conducted, and only the RDS1 of the drain-source on-state equivalent impedance participates in the work. The RDS1 and the R1 are connected in series to form a detection resistor, and because the load current is large when the load is fully loaded, a continuous voltage drop signal can be generated at point B by the small resistance values of the on-state impedance RDS and the R1, and the amplitude of the signal is larger than a first preset signal source Vref1 (which can be set according to the actual application requirement, for example, can be a reference voltage of 50 mV), so that the sampling requirement can be met, and a specific working waveform diagram is shown in fig. 5.
2. When the load is not fully loaded, the PWM duty ratio is defined to be between 0.1% and 100% (not including 100%), and at this time, Q1 always works in the on-off state, so the equivalent impedances RDS1 and RDS2 both participate in the work, and are respectively connected in series with R1 to form a detection resistor, and then a pulsating high-level signal is generated at point B, and a specific working waveform diagram is shown in fig. 6.
The two working modes can generate a high-level voltage signal (a continuous or pulsating high-level signal) at a point B, the voltage signal passes through R2 and then is sent to a pin3 of a first voltage comparator U1 to be compared with a reference voltage Vref1, when an input signal of the pin3 is higher than Vref1, because a pull-up resistor R3 is connected to a point C at an output end of U1, a direct-current high-level signal or a square wave pulsating signal is output by a point C at the end C, the signal is rectified by D1, subjected to voltage division by R4 and filtered by C1 and converted into a high-level direct-current signal (a point D) to be detected, and the MCU judges that an LED load is normal when the high-level signal is detected.
As shown in fig. 7 (duty ratio is 100%), and fig. 8 (duty ratio is less than 100%), if the LED load is open at time t1, and no current flows through Q1 and R1 in both of the above two operating modes, there is no voltage drop across RDS and R1, no high-level voltage signal at point B, the input signal of pin3 is lower than Vref1, and the low level is output at point C, which finally results in that the voltage at point D gradually drops to 0V at time t 2. That is to say, if the MUC does not detect a high level signal within a certain settable short time, it determines that the LED load is open, and at this time, it sends out a related instruction to notify the user, so as to implement the function of detecting and alarming the load open. The specific values at the time t1 and the time t2 are not limited, and can be set according to actual application requirements.
When the load short circuit detection is performed, the specific mode is as follows:
as shown in fig. 4, in normal operation (no matter what operation mode), by selecting R1 with a smaller resistance, the voltage drop generated by the load current flowing through both ends of the load current is smaller (point E), and this voltage is filtered by R5 and C2, and a smaller dc level signal is generated at point F, and is smaller than the second predetermined signal source Vref2 (which may be set according to the actual application requirement, for example, may be a reference voltage of 50 mV) at the non-inverting input terminal of the second voltage comparator U2. Therefore, a high level signal is always output at the output end G point of the U2, the high level signal is sent to the MCU for detection, and the MCU judges that the LED load is normal when detecting the high level signal. If the load is short-circuited at a certain time, the voltage drop generated by the short-circuit current flowing through the two ends of R1 increases instantaneously (point E), the voltage is filtered by R5 and C2, the dc level signal at point F increases instantaneously and is greater than the reference voltage Vref2, the comparator is triggered to act, the voltage at point G is pulled down instantaneously, the MCU detects the low level signal (or falling edge signal), the PWM driving signal is pulled down in time, and Q1 is turned off to protect the circuit device, and the specific waveform diagram can be as shown in fig. 9 (waveform during normal operation) and fig. 10 (waveform during short-circuit).
Further, in the application of multi-output constant voltage PWM dimming, whether each path of LED load is open-circuited or short-circuited can be conveniently detected, and the specific scheme is as follows: in the application of multi-path PWM dimming output, the positive terminal of the constant voltage source output is shared, the negative terminal is output through the PWM dimming control circuit, and each path of output is added as long as the LED load detection circuit module identical to the single-path output circuit is added, so that each path of output can be detected and controlled independently without mutual influence, and fig. 11 is an example of a schematic diagram of the application of the two-path output.
To sum up, load detection circuitry and system that this application embodiment provided, open circuit detecting element and short circuit detecting element are connected with the input and the output of first switch element respectively, can realize opening a way with the accurate detection of short circuit to the load, have avoided carrying out open circuit detection and short circuit detection through the voltage signal of switching device output among the prior art, have when the load is very little, the treater does not detect high level signal, misjudge that the LED load is opened a way to and it is big to detect the current resistance loss when load current is great, the temperature rise, the problem that the reliability of load detection that leads to is low.
The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.
Claims (10)
1. A load detection circuit, comprising:
the control end of the first switch unit is connected with the output end of the processor, and the input end of the first switch unit is connected with the anode of the first power supply through a load;
the input end of the open circuit detection unit is connected with the input end of the first switch unit, the output end of the open circuit detection unit is connected with the input end of the processor, the anode of the open circuit detection unit is connected with the second power supply, and the cathode of the open circuit detection unit is grounded;
the input end of the short-circuit detection unit is connected with the output end of the first switch unit, the output end of the short-circuit detection unit is connected with the input end of the processor, the positive electrode of the short-circuit detection unit is connected with the third power supply, and the negative electrode of the short-circuit detection unit is grounded;
a current detection unit, wherein the first end of the current detection unit is connected with the output end of the first switch unit, and the second end of the current detection unit is connected with the negative electrode of the first power supply;
the open circuit detection unit is used for outputting a corresponding open circuit detection signal to the processor according to the level signal of the input end of the first switch unit, and the short circuit detection unit is used for outputting a corresponding short circuit detection signal to the processor according to the level signal of the output end of the first switch unit.
2. The load detection circuit of claim 1, wherein the open circuit detection unit comprises:
and the non-inverting input end of the first voltage comparator is connected with the input end of the first switch unit, the inverting input end of the first voltage comparator is connected with a first preset signal source, the positive electrode of the first voltage comparator is connected with the second power supply, and the negative electrode of the first voltage comparator is grounded.
3. The load detection circuit of claim 1, wherein the short detection unit comprises:
and the inverting input end of the second voltage comparator is connected with the output end of the first switch unit, the non-inverting input end of the second voltage comparator is connected with a second preset signal source, the positive electrode of the second voltage comparator is connected with the third power supply, and the negative electrode of the second voltage comparator is grounded.
4. The load detection circuit of claim 1, wherein the current sensing unit comprises:
and the first end of the first resistor is connected with the output end of the first switch unit, and the second end of the first resistor is connected with the negative electrode of the first power supply.
5. The load detection circuit of claim 2, wherein the open circuit detection unit further comprises:
a second resistor, a first end of which is connected with the input end of the first switch unit, and a second end of which is connected with the non-inverting input end of the first voltage comparator;
a third resistor, a first end of which is connected with the second power supply and a second end of which is connected with the output end of the first voltage comparator;
and the anode of the first diode is connected with the output end of the first voltage comparator, and the cathode of the first diode is connected with the input end of the processor.
6. The load detection circuit of claim 5, wherein the open circuit detection unit further comprises:
a fourth resistor, a first end of which is connected with the cathode of the first diode and a second end of which is grounded;
and a first end of the first capacitor is connected with the cathode of the first diode, and a second end of the first capacitor is grounded.
7. The load detection circuit of claim 3, wherein the short detection unit further comprises:
a fifth resistor, a first end of which is connected to the output end of the first switching unit and a second end of which is connected to the inverting input end of the second voltage comparator;
a first end of the second capacitor is connected with the second end of the fifth resistor, and a second end of the second capacitor is grounded;
and a first end of the sixth resistor is connected with the third power supply, and a second end of the sixth resistor is connected with the output end of the second voltage comparator.
8. The load detection circuit of claim 7, wherein the short detection unit further comprises:
a first end of the seventh resistor is connected with the output end of the second voltage comparator, and a second end of the seventh resistor is grounded;
and the first end of the third capacitor is connected with the output end of the second voltage comparator, and the second end of the third capacitor is grounded.
9. The load detection circuit of claim 1, wherein the first switching unit comprises:
and the grid electrode of the first MOS tube is connected with the output end of the processor, the drain electrode of the first MOS tube is connected with the anode of the first power supply through the load, and the source electrode of the first MOS tube is connected with the cathode of the first power supply through the current detection unit.
10. A load detection system, comprising:
a processor;
the load detection circuit of any of claims 1-9;
the processor is connected with the load detection circuit and used for receiving the open-circuit detection signal and the short-circuit detection signal sent by the load detection circuit so as to detect the load.
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| CN202022235586.3U CN213240401U (en) | 2020-10-09 | 2020-10-09 | Load detection circuit and system |
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| CN202022235586.3U CN213240401U (en) | 2020-10-09 | 2020-10-09 | Load detection circuit and system |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN114488993A (en) * | 2021-12-20 | 2022-05-13 | 上海华兴数字科技有限公司 | Circuit state detection device and method |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN114488993A (en) * | 2021-12-20 | 2022-05-13 | 上海华兴数字科技有限公司 | Circuit state detection device and method |
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