Isolated digital input circuit and motor driver
By introducing a voltage divider control circuit and an optocoupler into the digital input circuit, the compatibility problem under different voltage environments is solved, self-adaptation and reverse connection protection are achieved, and the applicability and safety of the circuit are improved.
Patent Information
- Application Number
- CN202423281987.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-30
- Publication Date
- 2025-12-30
- Estimated Expiration
- 2034-12-30
AI Technical Summary
Existing digital input circuits lack compatibility with different input voltages, leading to limitations in use and potential risks of circuit damage.
An isolated digital input circuit was designed, employing a voltage divider control circuit and an optocoupler. The circuit provides operating voltage to the base and emitter of the transistor through a series diode functional circuit, thereby achieving voltage division of the digital signal. The optocoupler is used for signal isolation and output.
It achieves self-adaptation to different voltages, prevents damage from reverse connection, and improves the compatibility and reliability of the circuit.
Smart Images
Figure CN223744705U_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of digital input circuit technology, specifically to an isolated digital input circuit and a motor driver. Background Technology
[0002] In electronic devices, digital input circuits (DI circuits) and digital output circuits (DO circuits) are the most widely used circuits. The input voltages of digital input / output circuits commonly use 3.3V, 5V, 12V, and 24V. In practical applications, the voltage level of the input circuit is often determined by the input voltage value of the device's digital output circuit. This method lacks compatibility; if the output voltage changes, it cannot be used, thus significantly limiting its application. Therefore, it is necessary to design a digital input circuit that is compatible with different input voltages. Utility Model Content
[0003] The technical problem this application aims to solve is how to add an input electrical signal self-adaptation function to an isolated digital input circuit.
[0004] According to a first aspect, in one embodiment, an isolated digital input circuit is provided, including a voltage divider control circuit and an optocoupler U1;
[0005] The voltage divider control circuit includes a first resistor R10, a second resistor R11, a first transistor Q1, and a series diode functional circuit.
[0006] The first connection terminal of the first resistor R10 is connected to the base of the first transistor Q1, the second connection terminal of the first resistor R10 serves as the first input terminal of the digital signal, and the second connection terminal of the first resistor R10 is also connected to the first input terminal of the optocoupler U1.
[0007] The collector of the first transistor Q1 is connected to the second output terminal of the optocoupler U1;
[0008] The first connection terminal of the second resistor R11 is connected to the emitter of the first transistor Q1, and the second connection terminal of the second resistor R11 is connected to the series diode functional circuit.
[0009] The series diode functional circuit includes a first connection terminal, a second connection terminal, and a third connection terminal; the first connection terminal of the series diode functional circuit is connected to the base of the first transistor Q1, the second connection terminal of the series diode functional circuit is connected to the second connection terminal of the second resistor R11, and the third connection terminal of the series diode functional circuit is used as a second input terminal for digital signals.
[0010] The first and second input terminals of the digital signal are used as digital signal input terminals of the isolated digital input circuit, and the first and second output terminals of the optocoupler U1 are used as optocoupler control signal output terminals of the isolated digital input circuit.
[0011] The series diode functional circuit is unidirectional and is used to provide operating voltage to the base and emitter of the first transistor Q1 when a digital electrical signal is input to the isolated digital input circuit. This allows the digital signal input to the isolated digital input circuit to be divided by the first resistor R10 and the second resistor R12. The divided voltage signal obtained by the first resistor R10 is then output to the optocoupler U1 through the first input terminal and the second input terminal.
[0012] In one embodiment, the series diode functional circuit includes a second transistor Q2 and a third transistor Q3;
[0013] The collector of the second transistor Q2 is connected to the first connection terminal of the series diode functional circuit, and the emitter of the second transistor Q2 is connected to the collector of the third transistor Q3; the emitter of the third transistor Q3 is connected to the third connection terminal of the series diode functional circuit, and the base of the third transistor Q3 is connected to the second connection terminal of the series diode functional circuit.
[0014] In one embodiment, the series diode functional circuit includes a first diode D10, a second diode D11, a third diode D12, and a fourth diode D13;
[0015] The anode of the first diode D10 is connected to the first terminal of the series diode functional circuit, and the cathode of the first diode D10 is connected to the anode of the second diode D11. The cathode of the second diode D11 is connected to the anode of the third diode D12. The cathode of the third diode D11 is connected to the anode of the fourth diode D13. The cathode of the fourth diode D13 is connected to the third terminal of the series diode functional circuit, and the anode of the fourth diode D13 is also connected to the second terminal of the series diode functional circuit.
[0016] In one embodiment, the voltage divider control circuit further includes a third resistor R12; the first connection terminal of the third resistor R12 is connected to the emitter of the first transistor Q1, and the second connection terminal of the third resistor R12 is connected to the electrode of the first transistor Q1.
[0017] In one embodiment, the isolated digital input circuit further includes an output connection circuit; the output connection circuit includes a fourth resistor R13 and a first capacitor C11;
[0018] The first connection terminal of the fourth resistor R13 is electrically connected to the second connection terminal of the first resistor R10, and the second connection terminal of the fourth resistor R13 is electrically connected to the collector of the first transistor Q1.
[0019] The first terminal of the first capacitor C11 is electrically connected to the second terminal of the first resistor R10, and the second terminal of the first capacitor C11 is electrically connected to the collector of the first transistor Q1.
[0020] In one embodiment, the isolated digital input circuit further includes an input connection circuit; the input connection circuit includes a fifth resistor R14; the first connection terminal and the second connection terminal of the fifth resistor R14 are respectively connected to the first input terminal and the second input terminal of the digital signal.
[0021] In one embodiment, the input connection circuit further includes a sixth resistor R15 and a seventh resistor R16;
[0022] The first connection terminal of the sixth resistor R15 is connected to the first input terminal of the digital signal, and the second connection terminal of the sixth resistor R15 is electrically connected to the second connection terminal of the first resistor R10.
[0023] The first connection terminal of the seventh resistor R16 is connected to the second input terminal of the digital signal, and the second connection terminal of the seventh resistor R16 is electrically connected to the third connection terminal of the series diode functional circuit.
[0024] In one embodiment, the input connection circuit further includes a second capacitor C12;
[0025] The first connection terminal of the second capacitor C12 is connected to the second connection terminal of the sixth resistor R15, and the second connection terminal of the second capacitor C12 is connected to the second connection terminal of the seventh resistor R16.
[0026] In one embodiment, the positive and negative output terminals of the control signal of the isolated digital input circuit are respectively connected to the positive and negative input terminals of the optocoupler U1 to output an optocoupler control signal to the optocoupler U1.
[0027] In one embodiment, the first transistor Q1 is an NPN transistor; the voltage value of the digital signal input to the isolated digital input circuit is not greater than 24 volts and not less than 5 volts.
[0028] According to a second aspect, in one embodiment, a motor driver is provided, including an isolated digital input circuit as described in the first aspect.
[0029] According to the isolated digital input circuit of the above embodiment, since the voltage divider control circuit is compatible with digital signal input of multiple voltage values, the isolated digital input circuit has the function of self-adaptation of input digital signal. Attached Figure Description
[0030] Figure 1 This is a circuit connection diagram of a digital input circuit in the prior art;
[0031] Figure 2 This is a circuit diagram of an optocoupler;
[0032] Figure 3 This is a schematic diagram of the circuit connection of the voltage divider control circuit in one embodiment;
[0033] Figure 4 This is a schematic diagram of the circuit connection of an isolated digital input circuit in one embodiment;
[0034] Figure 5 This is a schematic diagram of the circuit connection for an isolated digital input circuit in another embodiment. Detailed Implementation
[0035] The present application will now be described in further detail with reference to the accompanying drawings and specific embodiments. Similar elements in different embodiments are referred to by related similar element reference numerals. In the following embodiments, many details are described to facilitate a better understanding of the present application. However, those skilled in the art will readily recognize that some features may be omitted in different situations, or may be replaced by other elements, materials, or methods. In some cases, certain operations related to the present application are not shown or described in the specification. This is to avoid obscuring the core parts of the present application with excessive description. For those skilled in the art, detailed description of these related operations is not necessary; they can fully understand the related operations based on the description in the specification and general technical knowledge in the art.
[0036] Furthermore, the features, operations, or characteristics described in the specification can be combined in any suitable manner to form various embodiments. At the same time, the steps or actions in the method description can be rearranged or adjusted in a manner obvious to those skilled in the art. Therefore, the various orders in the specification and drawings are only for the clear description of a particular embodiment and do not imply a necessary order, unless otherwise stated that a particular order must be followed.
[0037] The serial numbers assigned to components in this document, such as "first" and "second," are used only to distinguish the described objects and have no sequential or technical meaning. The terms "connection" and "linkage" used in this application, unless otherwise specified, include both direct and indirect connections (linkages).
[0038] Please refer to Figure 1 and Figure 2 These are circuit connection diagrams of a digital input circuit and a circuit diagram of an optocoupler in the prior art, respectively. The digital input circuit includes a negative input connection terminal PUL-, a first positive connection terminal PUL_A, a second positive connection terminal PUL_B, a first output connection terminal A, a second output connection terminal K, resistors R1 and R2, a diode D1, and a capacitor C1. The negative input connection terminal PUL- is used for grounding. The first positive connection terminal PUL_A and the second positive connection terminal PUL_B are used for input of at least two different voltage values among 3.3V, 5V, 12V, and 24V. The resistance values of resistors R1 and R2 are adapted to the voltage values input to the first positive connection terminal PUL_A and the second positive connection terminal PUL_B, respectively. Diode D1 is used to prevent reverse connection of the input voltage, and capacitor C1 is used for filtering. Output terminal A and output terminal K are respectively connected to the positive and negative input terminals of optocoupler U1. The positive and negative output terminals of optocoupler U1 are connected to coupling terminal B and coupling terminal L. Coupling terminal B and coupling terminal L are used to connect to the coupling output circuit to achieve isolation control of the optocoupler. Figure 2 As shown, the coupled output circuit includes capacitor C2 and resistor R3.
[0039] like Figure 1 The digital input circuit shown uses resistor circuits (resistors R1 and R2) to accommodate different input voltages. Depending on the input voltage value, the voltage signal input terminals (first positive connection terminal PUL_A or second positive connection terminal PUL_B) must be manually adjusted. Different input voltages require different current-limiting resistors (resistors R1 or R2). Incorrect use will cause the optocoupler U1 in the input circuit to fail to respond to external input (insufficient current) or damage the optocoupler U1 (excessive current). Furthermore, the above digital input circuit lacks reverse connection protection. When the external input voltage is reversed, diode D1 may be damaged, rendering the entire digital input circuit unusable. Example
[0040] Please refer to Figure 3This is a schematic diagram of the circuit connection of a voltage divider control circuit in one embodiment. The isolated digital input circuit includes an optocoupler U1 and a voltage divider control circuit 10. The voltage divider control circuit 10 includes a first resistor R10, a second resistor R11, a first transistor Q1, and a series diode functional circuit 11. The first terminal of the first resistor R10 is connected to the base of the first transistor Q1, and the second terminal of the first resistor R10 serves as the first input terminal of the digital signal. The second terminal of the first resistor R10 is also connected to the first input terminal of the optocoupler U1. The collector of the first transistor Q1 is connected to the second input terminal of the optocoupler U1. The first terminal of the second resistor R11 is connected to the emitter of the first transistor Q1, and the second terminal of the second resistor R11 is connected to the series diode functional circuit 11. The series diode functional circuit 11 includes a first connection terminal, a second connection terminal, and a third connection terminal. The first connection terminal of the series diode functional circuit 11 is connected to the base of the first transistor Q1, the second connection terminal of the series diode functional circuit 11 is connected to the second connection terminal of the second resistor R11, and the third connection terminal of the series diode functional circuit 11 serves as the second input terminal for the digital signal. The first and second input terminals of the digital signal are used as digital signal input terminals for the isolated digital input circuit, and the first and second output terminals of the optocoupler U1 are used as optocoupler control signal output terminals for the isolated digital input circuit. The series diode functional circuit 11 is unidirectional and provides operating voltage to the base and emitter of the first transistor Q1 when a digital signal is input to the isolated digital input circuit. This voltage is used to divide the digital signal input to the isolated digital input circuit through the first resistor R10 and the second resistor R12, and the divided voltage signal obtained by the first resistor R10 is output to the optocoupler U1 through the first and second input connection terminals. In one embodiment, the first transistor Q1 is an NPN transistor. In one embodiment, the voltage value of the digital signal input to the isolated digital input circuit is not greater than 24 volts and not less than 5 volts.
[0041] In one embodiment, the series diode functional circuit 11 includes a first diode D10, a second diode D11, a third diode D12, and a fourth diode D13. The anode of the first diode D10 is connected to the first connection terminal of the series diode functional circuit 11, and the cathode of the first diode D10 is connected to the anode of the second diode D11. The cathode of the second diode D11 is connected to the anode of the third diode D12, and the cathode of the third diode D11 is connected to the anode of the fourth diode D13. The cathode of the fourth diode D13 is connected to the third connection terminal of the series diode functional circuit 11, and the anode of the fourth diode D13 is also connected to the second connection terminal of the series diode functional circuit 11.
[0042] Please refer to Figure 4The diagram illustrates the circuit connection of an isolated digital input circuit in one embodiment. In one embodiment, the series diode functional circuit 11 includes a second transistor Q2 and a third transistor Q3. The collector of the second transistor Q2 is connected to the first connection terminal of the series diode functional circuit 11, and the emitter of the second transistor Q2 is connected to the collector of the third transistor Q3. The emitter of the third transistor Q3 is connected to the third connection terminal of the series diode functional circuit, and the base of the third transistor Q3 is connected to the second connection terminal of the series diode functional circuit 11.
[0043] Please refer to Figure 5 The diagram below shows the circuit connection of the isolated digital input circuit in another embodiment. In one embodiment, the voltage divider control circuit further includes a third resistor R12. The first terminal of the third resistor R12 is connected to the emitter of the first transistor Q1, and the second terminal of the third resistor R12 is connected to the electrode of the first transistor Q1.
[0044] like Figure 4 As shown, in one embodiment, the isolated digital input circuit further includes an output connection circuit 20 and an input connection circuit 30. The output connection circuit 20 includes a fourth resistor R13 and a first capacitor C11. The first terminal of the fourth resistor R13 is electrically connected to the second terminal of the first resistor R10, and the second terminal of the fourth resistor R13 is electrically connected to the collector of the first transistor Q1. The first terminal of the first capacitor C11 is electrically connected to the second terminal of the first resistor R10, and the second terminal of the first capacitor C11 is electrically connected to the collector of the first transistor Q1. The input connection circuit 30 includes a fifth resistor R14, the first terminal of which is connected to the first input terminal of the digital signal, and the second terminal of which is connected to the second input terminal of the digital signal, respectively. In one embodiment, the input connection circuit 30 further includes a sixth resistor R15 and a seventh resistor R16. The first terminal of the sixth resistor R15 is connected to the first input terminal of the digital signal, and the second terminal of the sixth resistor R15 is electrically connected to the second terminal of the first resistor R10. The first terminal of the seventh resistor R16 is connected to the second input terminal of the digital signal, and the second terminal of the seventh resistor R16 is electrically connected to the third terminal of the series diode functional circuit. In one embodiment, the input connection circuit 30 further includes a second capacitor C12. The first terminal of the second capacitor C12 is connected to the second terminal of the sixth resistor R15, and the second terminal of the second capacitor C12 is connected to the second terminal of the seventh resistor R16.
[0045] In one embodiment of this application, a motor driver is also disclosed, including the isolated digital input circuit described above.
[0046] The isolated digital input circuit disclosed in this application includes an optocoupler and a voltage divider control circuit composed of two resistors, a transistor, and a series diode functional circuit. One end of the first resistor is connected to the base of the transistor, and the other end is used for digital signal input and connected to the first input terminal of the optocoupler. The second input terminal of the optocoupler is connected to the collector of the transistor. The second resistor is connected between the emitter of the transistor and the series diode functional circuit. The series diode functional circuit is connected to the base of the transistor and one end of the second resistor, respectively. When a digital signal is input to the isolated digital input circuit, it provides operating voltage to the base and emitter of the transistor to divide the digital signal through the first and second resistors, and outputs the divided voltage signal obtained by the first resistor to the optocoupler. Since the voltage divider control circuit is compatible with digital signals of multiple voltage values, the isolated digital input circuit has an input signal self-adaptation function.
[0047] The isolated digital input circuit disclosed in this application controls the optocoupler current using simple electronic components such as resistors, capacitors, and transistors. It also achieves reverse connection protection, external pull-up optimization, transistor heat dissipation optimization, and interference immunity optimization. It is suitable for driver input circuits, such as pulse, direction, and enable inputs. To facilitate understanding of the working principle and operation mode of the isolated digital input circuit disclosed in this application, specific embodiments are described below, including:
[0048] like Figure 4 As shown, the first resistor R10, the first transistor Q1, the second transistor Q2, the third transistor Q3, and the second resistor R11 set the optocoupler output current. According to the transistor's conduction characteristics, the base theoretically conducts at a voltage 0.7V higher than the emitter. The voltage is set via a diode. BE The total voltage across the transistor's base-emitter voltage and the second resistor R11 is 1.5V, therefore the voltage drop across the second resistor R11 is 0.8V, and the current flowing through it is 9mA. The current flowing through the second resistor R11 is the same as the current flowing through the optocoupler and the starting resistor (the fourth resistor R13) (the transistor's base current is small and can be ignored). This current ensures the optocoupler can conduct effectively without being damaged by overheating. It also increases the starting voltage. Considering 0.1mA as the diode's maximum conduction current, at 25℃, the diode voltage drop is 0.4*4=1.6V (if...). Figure 5 As shown (equivalent to four diodes connected in series), the voltage drop across the first resistor R10 is approximately 0.7V, and the maximum forward voltage is set to 2.3V. It should be noted that operation under these conditions is not recommended; this description is for extreme value estimation only. The third transistor Q3 has reverse connection protection, and its reverse withstand voltage is 30V, which is sufficient for everyday needs. For higher withstand voltage requirements, adjustments can be made accordingly.
[0049] The fifth resistor R14 can provide a pull-up resistor for external single-ended signals. For example, in some PLC open-drain output application scenarios, when the PLC has no pull-up resistor, if the PLC internal transistor is set to turn off, the output will be placed in floating mode. At this time, the signal has no driving capability, which does not meet the plug-and-play goal of this solution. Therefore, in one embodiment, the fifth resistor R14 is added.
[0050] The third resistor R12 is used for current shunting to reduce the heat generation of the first transistor Q3. Considering the current settings, the current flowing through the second resistor R11 is 9mA, and the typical high-speed optocoupler voltage is 1 to 1.4 volts. Taking 1.4 volts as an example, and considering the current flowing through the diode is approximately 3mA, the voltage drop across the sixth resistor R15 and the seventh resistor R16 is approximately 0.6V. Assuming a single-transistor voltage drop of the third transistor Q3 is 0.4V, the collector-emitter voltage drop of the first transistor Q1 is 24 - 0.6 - 1.4 - 0.4 - 0.6 = 21V. With the third resistor R12 (4KΩ), the current flowing through the first transistor Q1 is 9 - 21 / 4 = 3.75mA, and the estimated power is 21 * 0.00375 = 0.07875W. Without the third resistor R12, the current flowing through the first transistor Q1 is 9mA, and the estimated power is 21 * 0.009 = 0.189W. The rated power of the first transistor Q1 is 0.225W. It is generally designed at 70% of its rated power, and it is recommended that the power not exceed 0.1575W, otherwise the heat generation will be serious. Adding the third resistor R12 can meet the requirements.
[0051] The first resistor R10 increases the startup current of the optocoupler. The sixth resistor R15 and the seventh resistor R16 in the input connection circuit, the fourth resistor R13 in the output connection circuit, and the first capacitor C11 are used for input filtering of the optocoupler to enhance the overall anti-interference capability of the compatibility circuit.
[0052] The following describes the operating state of the isolated digital input circuit disclosed in this application when input electrical signals of different voltage values are input:
[0053] (1) When the voltage of the input electrical signal is 5V.
[0054] The optocoupler needs to meet the requirement of a startup voltage of 2.3V. The current loop starts from the input positive voltage signal PUL+. It passes through the sixth resistor R15 in sequence, with a voltage drop of 0.41V, and then through the first resistor R10, the fourth resistor R13, and the optocoupler U1. At this time, the common terminal voltage of the optocoupler U1 with the first resistor R10 and the fourth resistor R13 is 4.59V.
[0055] a) Considering the first current path: first resistor R10 → second transistor Q2 → third transistor Q3 → seventh resistor R16. After the second transistor Q2 is turned on, the actual voltage drop of a single transistor is 0.53V. After the third transistor Q3 is turned on, the actual voltage drop of a single transistor is 0.23V and 0.32V (the voltage drop differs due to the difference in current). At this time, the voltage drop of the first resistor R10 is 2.56V, and the current in the current path is 2.56 / 7.5 = 0.34mA.
[0056] b) Considering the second current path: fourth resistor R13 + optocoupler U1 → first transistor Q3 + third resistor R12 → second resistor R11 → third transistor Q3 → seventh resistor R16. The base voltage of the transistor is 2.03V, and the measured Vbe = 0.66V (base-emitter voltage drop), Vce = 1.89V. The transistor is operating in amplification mode. At this time, the voltage across the second resistor R11 is measured to be 0.63V, and the calculated current is 0.63 / 82 = 0.00768A = 7.68 mA (the base current of the transistor is small and not considered here). The measured forward voltage of optocoupler U1 and the voltage across the fourth resistor R13 are 1.34V. Therefore, the current across the fourth resistor R13 is 1.34 / 1 = 1.34mA. The forward current of optocoupler U1 at this time is 7.68 - 1.34 = 6.34mA.
[0057] (2) When the voltage of the input electrical signal is 24V.
[0058] The starting voltage requirement of 2.3V must be met. The current loop starts from the input positive voltage signal PUL+, passes through the sixth resistor R15, and has a voltage drop of 0.735V. After passing through the sixth resistor R15, the main current path is through the first resistor R10, the fourth resistor R13, and the optocoupler U1. At this time, the common terminal voltage of the optocoupler with the first resistor R10 and the fourth resistor R13 is 23.265V.
[0059] a) Considering the path from resistor R10 to transistor Q2, then to transistor Q1, and finally to resistor R16, the actual voltage drop across transistor Q2 after it turns on is 0.63V. The actual voltage drops across transistor Q3 after it turns on are 0.275V and 0.335V respectively. At this point, the voltage drop across resistor R10 is 20.66V, and the current in the current path is 20.66 / 7.5 = 2.755mA. The power consumption of resistor R10 is calculated as 20.66 * 20.66 / 7.5K = 56.9mW. 56.8 / 125 * 100% = 45.5% (the rated power of resistor R10 is 0.125W), which meets the power requirements.
[0060] b) Considering the second current path: fourth resistor R13 + optocoupler U1 → first transistor Q1 + third resistor R12 → second resistor R11 → third transistor Q3 → seventh resistor R16. The base voltage of the transistor is 2.605V, and the measured Vbe = 0.585V (base-emitter voltage drop), Vce = 19.9V. The transistor is operating in amplification mode. At this time, the voltage across the second resistor R11 is measured to be 0.955V, and the calculated current is 0.955 / 82 = 0.01164A = 11.64 mA (the base current of the transistor is small and not considered here). The measured forward voltage of optocoupler U1 and the voltage across the fourth resistor R13 are 1.34V. Therefore, the current flowing through the fourth resistor R13 is 1.34 / 1 = 1.34mA, and the forward current of the optocoupler is 11.64 - 1.34 = 10.3mA. Furthermore, the current Ice of the first transistor Q1 is calculated to be 11.64 - 19.9 / 3.9 = 6.54mA (the third resistor R12 is chosen here as 3.9K). The power estimate (ignoring base current) is 19.9 * 6.54 = 130.164mW, 130.164 / 225 * 100% = 57.8%, which meets the power requirement. The power of the third resistor R12 is calculated to be 19.9 * 19.9 / 3.9 = 101.54mW. A 0.25W resistor is chosen for R12, and 101.54 / 250 * 100% = 40.6%, which meets the power requirement.
[0061] (3) The voltage value of the input electrical signal is 0V.
[0062] Because the required starting voltage of 2.3V is not met, the transistor is cut off, and the optocoupler, the second transistor Q2, and the third transistor Q3 cannot conduct, so the circuit does not work.
[0063] (4) Input signal reversed.
[0064] Based on the characteristics of the diode's PN junction, the circuit cannot form a loop at this time. The reverse voltage of the third transistor, Q3, is selected to be 30V, therefore it can provide normal protection under normal application conditions (5 to 24V) and will not be damaged.
[0065] Based on the above, the isolated digital input circuit disclosed in this application is compatible with the input of digital signals with multiple voltage values. It utilizes the amplification characteristics of the first transistor Q1, and under the condition of increasing the bias voltage based on the series diode functional circuit, it controls the current flowing through the second resistor R11, indirectly controlling the current flowing through the optocoupler within a reasonable range. This achieves an isolated digital input circuit compatible with 5 to 24V voltage input. At the same time, it uses the third transistor Q3 to form a reverse connection protection circuit. When the power supply is reversed, a current loop cannot be formed, thereby protecting the optocoupler U1.
[0066] The above description uses specific examples to illustrate this utility model, which are only for the purpose of helping to understand this application and are not intended to limit this application. For those skilled in the art to which this application pertains, based on the concept of this application, several simple deductions, modifications, or substitutions can be made.
Claims
1. An isolated digital input circuit, characterized by, The voltage dividing control circuit and the optoelectronic coupler U1 are included. The voltage dividing control circuit includes a first resistor R10, a second resistor R11, a first triode Q1 and a series diode function circuit. The first connection end of the first resistor R10 is connected with the base of the first triode Q1, and the second connection end is used as the first input end of the digital signal. The second connection end of the second resistor R11 is connected with the series diode function circuit. The series diode function circuit includes a first connection end, a second connection end and a third connection end. The series diode function circuit includes a second triode Q2 and a third triode Q3.
2. The isolated digital input circuit of claim 1, wherein, The series diode function circuit includes a first diode D10, a second diode D11, a third diode D12 and a fourth diode D13. The series diode function circuit includes a first diode D10, a second diode D11, a third diode D12 and a fourth diode D13.
3. The isolated digital input circuit of claim 1, wherein, The series diode function circuit includes a first diode D10, a second diode D11, a third diode D12 and a fourth diode D13. The series diode function circuit includes a first diode D10, a second diode D11, a third diode D12 and a fourth diode D13.
4. The isolated digital input circuit of claim 1, wherein, The voltage dividing control circuit further includes a third resistor R12.
5. The isolated digital input circuit of claim 1, wherein, The output connection circuit includes a fourth resistor R13 and a first capacitor C11. The first connection end of the fourth resistor R13 is electrically connected with the second connection end of the first resistor R10, and the second connection end of the fourth resistor R13 is electrically connected with the collector of the first triode Q1. The first connection end of the first capacitor C11 is electrically connected with the second connection end of the first resistor R10, and the second connection end of the first capacitor C11 is electrically connected with the collector of the first triode Q1.
6. The isolated digital input circuit of claim 1, wherein, The input connection circuit further comprises a fifth resistor R14, a sixth resistor R15 and a seventh resistor R16.
7. The isolated digital input circuit of claim 6, wherein, The first connection end of the sixth resistor R15 is connected with the first input end of the digital signal, and the second connection end of the sixth resistor R15 is electrically connected with the second connection end of the first resistor R10. The first connection end of the seventh resistor R16 is connected with the second input end of the digital signal, and the second connection end of the seventh resistor R16 is electrically connected with the third connection end of the series diode function circuit. The input connection circuit further comprises a second capacitor C12.
8. The isolated digital input circuit of claim 7, wherein, The first connection end of the second capacitor C12 is connected with the second connection end of the sixth resistor R15, and the second connection end of the second capacitor C12 is connected with the second connection end of the seventh resistor R16. The first triode Q1 is an NPN type triode, and / or the voltage value of the digital signal input into the isolation digital input circuit is not greater than 24 volts and not less than 5 volts.
9. The isolated digital input circuit of claim 1, wherein, The isolation digital input circuit comprises the isolation digital input circuit according to any one of claims 1 to 9.
10. An electric motor drive, characterized by