DAC signal conversion circuit of DC motor

Abstract

The utility model discloses a DAC signal conversion circuit of a DC motor, and belongs to the technical field of motor driving. The circuit comprises a power supply voltage conversion module, an integration unit, a voltage follower module and an analog voltage output module. The output end of the power supply voltage conversion module is connected with the input end of the integration unit, the output end of the integration unit is connected with the input end of the voltage follower module, and the output end of the voltage follower module is connected with the input end of the analog voltage output module; and the voltage follower module is used for isolating the output end of the integration unit from the input end of the analog voltage output module. The DAC signal conversion circuit of the DC motor provided by the utility model realizes an efficient and accurate conversion process from a PWM signal to an analog voltage signal, significantly improves the level conversion and response speed, can flexibly control the output amplitude and stability of the analog voltage signal, has the advantages of simple structure, low cost, high reliability, etc. The method can be widely applied to various fields.

Description

TECHNICAL FIELD

[0001] The utility model relates to a DAC signal conversion circuit of direct current motor belongs to motor drive technical field. BACKGROUND

[0002] At present, common motor driver control mode mainly includes PWM (pulse width modulation) control mode and analog voltage signal interface control two categories, PWM technology is a kind of widely used voltage regulation and control technology, through the pulse width of signal, the precision control of voltage amplitude can be realized, its precision is generally as high as 0.15 ‰, however, PWM technology is not enough convenient in the data acquisition of output voltage.Compared with this, using analog voltage signal output can more directly and simply carry out data acquisition, because analog signal is continuous change voltage or current, can be directly read and recorded through analog-digital converter (ADC) and other equipment.In order to combine the high precision of PWM control and the convenience of analog signal acquisition, there are two main methods of controlling analog voltage output in the market.

[0003] The first method depends on the combination of microcontroller (MCU) and digital-to-analog converter (DAC). The MCU obtains the duty cycle of its PWM, and then transmits this information to the DAC chip. The DAC chip accurately adjusts its analog output voltage according to the received duty cycle information, thereby realizing the conversion from PWM signal to analog voltage signal. Although this method has relatively high hardware cost, it can achieve high control precision and flexibility.

[0004] Another more economical method is to realize conversion through passive pure circuit. The circuit is usually composed of a PWM wave generation unit, two integral units and an analog voltage output unit. Both integral units use RC filter circuits composed of resistors R and capacitors C to convert the duty cycle of PWM signals into corresponding analog voltages through integral action. However, in actual application, researchers found that the load connected to the analog voltage output end would negatively affect the accuracy of the second integral unit, causing the output voltage to deviate from the expected value.

[0005] In the existing technology, when using the DAC (digital-to-analog converter) chip to generate analog voltage, not only the cost burden is high, but also the valuable hardware resources are consumed, and the complexity of circuit design is increased. In addition, this scheme often faces the dual challenges of limited precision and insufficient stability, which constitutes a not small obstacle in actual application. On the other hand, relying on microprocessor to control DAC chip to output analog voltage not only has a complicated operation process, but also greatly increases the risk of microprocessor damage, and is extremely inconvenient in subsequent maintenance or replacement steps.

[0006] In comparison, the passive pure circuit scheme is used to generate analog voltage, which can significantly improve the accuracy level of the output, while greatly reducing the overall cost of the circuit design, showing significant advantages. It is worth noting that the current mainstream DAC conversion circuit only supports the adjustment of the load driving voltage in the range of 0~5V in the design, and once the driving voltage required by the load exceeds this threshold, the load capacity will be significantly reduced, which limits its application range. Utility model content

[0007] The technical problems to be solved by the utility model are to overcome the deficiencies of the prior art, provide a DAC signal conversion circuit of a direct current motor, realize an efficient and accurate conversion process from a PWM signal to an analog voltage signal, significantly improve the level conversion and response speed, can flexibly control the output amplitude and stability of the analog voltage signal, meet the needs of different application occasions, have the advantages of simple structure, low cost, high reliability, etc., and can be widely applied in various fields.

[0008] In order to solve the above technical problems, the technical scheme of the utility model is:

[0009] The utility model provides a DAC signal conversion circuit of a direct current motor, which comprises a power voltage conversion module, an integral unit, a voltage follower module and an analog voltage output module.

[0010] The input end of the power voltage conversion module is used for receiving a PWM signal, the output end of the power voltage conversion module is connected with the input end of the integral unit, the output end of the integral unit is connected with the input end of the voltage follower module, and the output end of the voltage follower module is connected with the input end of the analog voltage output module.

[0011] The voltage follower module is used for isolating the output end of the integral unit and the input end of the analog voltage output module, and the analog voltage output module is used for outputting an analog voltage signal converted by the PWM signal.

[0012] Further, the power voltage conversion module comprises a first voltage conversion module and a second voltage conversion module.

[0013] The input end of the first voltage conversion module is used for receiving a PWM signal, and the output end of the first voltage conversion module is connected with the input end of the second voltage conversion module.

[0014] The output end of the second voltage conversion module is connected with the input end of the integral unit.

[0015] Further, the integral unit comprises a first integral unit and a second integral unit.

[0016] The input end of the first integration unit is connected with the output end of the second voltage conversion module, and the output end of the first integration unit is connected with the input end of the second integration unit.

[0017] The output end of the second integration unit is connected with the input end of the voltage follower module.

[0018] Further, the first voltage conversion module comprises a triode Q1, a resistor R1, a resistor R2, a resistor R3 and an input constant voltage source V1.

[0019] The base of the triode Q1 receives a PWM signal through the resistor R1, and the base of the triode Q1 is grounded through the resistor R2.

[0020] The emitter of the triode Q1 is grounded.

[0021] The collector of the triode Q1 is connected with the positive pole of the input constant voltage source V1 through the resistor R3.

[0022] The negative pole of the input constant voltage source V1 is grounded.

[0023] Further, the second voltage conversion module comprises a triode Q2, a resistor R4, a resistor R5, a resistor R6 and a resistor R7.

[0024] The base of the triode Q2 is connected with the collector of the triode Q1 through the resistor R6, and the base of the triode Q2 is grounded through the resistor R7.

[0025] The emitter of the triode Q2 is grounded.

[0026] The collector of the triode Q2 is connected with the positive pole of the input constant voltage source V1 through the resistor R4 and the resistor R5, and the resistor R4 and the resistor R5 are connected in parallel.

[0027] Further, the first integration unit comprises a resistor R8 and a capacitor C1, one end of the resistor R8 is connected with the collector of the triode Q2, and the other end of the resistor R8 is grounded through the capacitor C1.

[0028] Further, the second integration unit comprises a resistor R9 and a capacitor C2, one end of the resistor R9 is connected with the resistor R8, and the other end of the resistor R9 is grounded through the capacitor C2.

[0029] Further, the voltage follower module comprises an operational amplifier U1 and an input constant voltage source V2.

[0030] The positive input end of the operational amplifier U1 is connected with the other end of the resistor R9, and the negative input end of the operational amplifier U1 is connected with the output end of the operational amplifier U1.

[0031] The positive input end of the operational amplifier U1 is connected with the positive pole of the input constant voltage source V2, the negative input end of the operational amplifier U1 is grounded, and the negative pole of the input constant voltage source V2 is grounded.

[0032] The output end of the operational amplifier U1 is connected with the input end of the analog voltage output module, and the output end of the operational amplifier U1 outputs an analog voltage.

[0033] Further, the analog voltage output module comprises a resistor R10, one end of the resistor R10 is connected with the output end of the operational amplifier U1, and the other end of the resistor R10 is grounded.

[0034] Further, the value of the input constant voltage source V2 is set to be greater than or equal to the voltage at the output end of the operational amplifier U1.

[0035] By adopting the technical scheme, the utility model discloses a triode boost and controls output analog voltage through PWM duty ratio, realizes the efficient and accurate conversion process of PWM signal to analog voltage signal, significantly improves level conversion and response speed, can flexibly control the output amplitude and stability of analog voltage signal, realizes high-precision, low-ripple output, effectively reduces the cost, and is suitable for various application scenarios. By increasing the voltage follower, the ability of the output analog voltage to carry a load can be effectively enhanced, the problem of insufficient driving capacity of a high-voltage load in the traditional scheme is solved, and the output end of the integral unit and the input end of the analog voltage output module are isolated by using the voltage follower, so that the output analog voltage is not affected by load changes, the quality of the analog voltage output is improved, the accuracy and stability of the whole circuit are improved, and a more reliable basis is provided for subsequent data acquisition and processing. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 It is a principle block diagram of the DAC signal conversion circuit of the direct current motor of the utility model;

[0037] Figure 2 It is a circuit principle diagram of the DAC signal conversion circuit of the direct current motor of the utility model;

[0038] Figure 3 It is a circuit principle diagram of the DAC signal conversion circuit (not containing voltage follower) of the direct current motor of the utility model;

[0039] Figure 4 It is the voltage output waveform when D=20% of the utility model not containing voltage follower;

[0040] Figure 5 It is the voltage output waveform when D=20% of the utility model containing voltage follower;

[0041] Figure 6 The voltage output waveform when the voltage follower D=40% is included in the utility model;

[0042] Figure 7 The voltage output waveform when the voltage follower D=60% is included in the utility model;

[0043] Figure 8 The voltage output waveform when the voltage follower D=80% is included in the utility model;

[0044] Figure 9 The PWM initial signal waveform (D=20%) of the utility model;

[0045] Figure 10 The collector end waveform (D=20%) of the triode Q2 of the utility model. DETAILED DESCRIPTION

[0046] In order to make the content of the utility model more easily be clearly understood, the utility model is further explained in detail below according to specific embodiments and in conjunction with the drawings.

[0047] As Figure 1 The DAC signal conversion circuit of the direct current motor provided by the embodiment includes a power voltage conversion module, an integration unit, a voltage follower module and an analog voltage output module.

[0048] The input end of the power voltage conversion module is used for receiving a PWM signal, the output end of the power voltage conversion module is connected with the input end of the integration unit, the output end of the integration unit is connected with the input end of the voltage follower module, and the output end of the voltage follower module is connected with the input end of the analog voltage output module.

[0049] The voltage follower module is used for isolating the output end of the integration unit and the input end of the analog voltage output module, and the analog voltage output module is used for outputting an analog voltage signal converted by the PWM signal.

[0050] As Figure 1 The power voltage conversion module of the embodiment includes a first voltage conversion module and a second voltage conversion module.

[0051] The input end of the first voltage conversion module is used for receiving a PWM signal, and the output end of the first voltage conversion module is connected with the input end of the second voltage conversion module.

[0052] The output end of the second voltage conversion module is connected with the input end of the integration unit.

[0053] As Figure 1 The integration unit of the embodiment includes a first integration unit and a second integration unit.

[0054] The input end of the first integration unit is connected with the output end of the second voltage conversion module, and the output end of the first integration unit is connected with the input end of the second integration unit.

[0055] The output end of the second integration unit is connected with the input end of the voltage follower module.

[0056] As shown in Figure 2 The first voltage conversion module of the embodiment includes an NPN triode Q1, a resistor R1, a resistor R2, a resistor R3 and an input constant voltage source V1.

[0057] The base of the NPN triode Q1 receives a PWM signal through the resistor R1, and the base of the NPN triode Q1 is grounded through the resistor R2.

[0058] The emitter of the NPN triode Q1 is grounded.

[0059] The collector of the NPN triode Q1 is connected with the positive pole of the input constant voltage source V1 through the resistor R3, and the NPN triode Q1 and the resistor R3 constitute a NOT gate circuit.

[0060] The negative pole of the input constant voltage source V1 is grounded.

[0061] As shown in Figure 2 The second voltage conversion module of the embodiment includes an NPN triode Q2, a resistor R4, a resistor R5, a resistor R6 and a resistor R7.

[0062] The base of the NPN triode Q2 is connected with the collector of the NPN triode Q1 through the resistor R6, and the base of the NPN triode Q2 is grounded through the resistor R7.

[0063] The emitter of the NPN triode Q2 is grounded.

[0064] The collector of the NPN triode Q2 is connected with the positive pole of the input constant voltage source V1 through the resistor R4 and the resistor R5, the resistor R4 and the resistor R5 are connected in parallel, and the NPN triode Q2 and the resistor R4 and the resistor R5 constitute a NOT gate circuit.

[0065] As shown in Figure 2 The first integration unit of the embodiment includes a resistor R8 and a capacitor C1, one end of the resistor R8 is connected with the collector of the NPN triode Q2, and the other end of the resistor R8 is grounded through the capacitor C1.

[0066] As shown in Figure 2 The second integration unit of the embodiment includes a resistor R9 and a capacitor C2, one end of the resistor R9 is connected with the resistor R8, and the other end of the resistor R9 is grounded through the capacitor C2.

[0067] In this embodiment, the equivalent resistance of the parallel connection of resistors R4 and R5 is much smaller than the value of resistors R8 and R9, otherwise the resistance of resistors R4 and R5 will affect the size of the integral voltage output, here resistors R4 and R5 are set to 2K, and resistors R8 and R9 are set to 20K. When the value of input constant voltage source V1 is relatively high, the triode Q2 is in a saturated conduction state, at this time the power that resistors R4 and R5 need to bear is relatively large, therefore two resistors are needed to share the power. Capacitors C1 and C2 are set to 10nF, a too small capacitance value will cause a relatively large ripple in the output, and a too large capacitance value will cause a relatively long rise time of the output voltage.

[0068] As shown in Figure 2 , the voltage follower module of this embodiment includes an operational amplifier U1 and an input constant voltage source V2;

[0069] The positive input end of the operational amplifier U1 is connected to the other end of resistor R9, and the negative input end of the operational amplifier U1 is connected to the output end of the operational amplifier U1.

[0070] The positive input end of the power supply of the operational amplifier U1 is connected to the positive pole of the input constant voltage source V2, the negative input end of the power supply of the operational amplifier U1 is grounded, and the negative pole of the input constant voltage source V2 is grounded.

[0071] The output end of the operational amplifier U1 is connected to the input end of the analog voltage output module, and the output end of the operational amplifier U1 outputs an analog voltage.

[0072] In this embodiment, the operational amplifier U1 adopts LM124, and the power voltage of the voltage follower module cannot be lower than the maximum voltage of the output, that is, the value of the input constant voltage source V2 should be set to be greater than or equal to the voltage at the output end of the operational amplifier U1, if the value of the input constant voltage source V2 is less than the voltage at the output end of the operational amplifier U1, the output analog voltage value will be affected, here the value of the input constant voltage source V2 is set to 12V.

[0073] As shown in Figure 2 , the analog voltage output module of this embodiment includes a load resistor R10, one end of the load resistor R10 is connected to the output end of the operational amplifier U1, and the other end of the load resistor R10 is grounded.

[0074] As shown in Figure 3 , if the voltage follower module is not included in the DAC signal conversion circuit, when the PWM duty ratio D=20% and the input constant voltage source V1=12V, the calculated analog output voltage value V out should be V1×D=2.4V, as shown in Figure 4 , the test of the analog output voltage V out when D=20% without the voltage follower is 485.5mV≠2.4V.

[0075] If the DAC signal conversion circuit contains a voltage follower module, as shown in Figure 5 When the PWM signal duty cycle D=20%, input constant voltage source V1=12V, the test analog output voltage V out =2.47V; as shown in Figure 6 When the PWM signal duty cycle D=40%, input constant voltage source V1=12V, the test analog output voltage V out =4.8V; as shown in Figure 7 When the PWM signal duty cycle D=60%, input constant voltage source V1=12V, the test analog output voltage V out =7.2V; as shown in Figure 8 When the PWM signal duty cycle D=80%, input constant voltage source V1=12V, the test analog output voltage V out =9.6V.

[0076] After adding an operational amplifier as a voltage follower, the analog voltage of the output signal will not be affected by the load because the impedance of the operational amplifier is much larger than the connected load, and from the output waveform, it can be seen that the analog output voltage of the DAC signal conversion circuit has a fast response time of 2ms and a small ripple.

[0077] The working principle of the utility model is as follows:

[0078] When adjusting the motor, as shown in Figure 9 The PWM port sends a signal with a duty cycle of D, which saturates and turns on the triode Q1 through resistors R1 and R2, and obtains a PWM waveform opposite to the initial PWM signal at the collector of the triode Q1, and through the secondary conversion of resistors R6 and R7 and the triode Q2, obtains a waveform at the collector of the triode Q2 which is the same as the initial PWM signal, but the voltage amplitude will be larger, as shown in Figure 10 The voltage amplitude is close to the value of the input constant voltage source V1, and by using the charging and discharging principle of RC, the analog voltage is obtained after integration of resistors R8 and capacitor C1, and resistors R9 and capacitor C2, and the output analog voltage value is about DxV1.

[0079] The utility model discloses utilize triode boost and through PWM duty factor control output analog voltage, realized the efficient and accurate conversion process of PWM signal to analog voltage signal, significantly promoted level conversion and response speed, can flexibly control the output amplitude and stability of analog voltage signal, realized high accuracy, low ripple output, effectively reduced the cost, can be widely used in robot, AGV dolly, industrial control, sound system etc. field. Through increasing voltage follower, can effectively enhance the ability of output analog voltage with load, solved the problem of insufficient driving ability of high voltage load in traditional scheme, simultaneously using voltage follower to the output end of integral unit and the input end of analog voltage output module is isolated, can ensure that output analog voltage is not influenced by load change, improved the quality of analog voltage output, improved the accuracy and stability of whole circuit, provided more reliable foundation for subsequent data acquisition and processing.

[0080] The above-described specific embodiments further illustrate the technical problems, technical solutions and beneficial effects solved by the utility model, and it should be understood that the above-described specific embodiments are merely examples of the utility model and are not intended to limit the utility model. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the utility model should be included in the protection scope of the utility model.

Claims

1. A DAC signal conversion circuit for a DC motor, characterized in that, It includes a power-to-voltage conversion module, an integrator unit, a voltage follower module, and an analog voltage output module; The input terminal of the power supply voltage conversion module is used to receive PWM signals. The output terminal of the power supply voltage conversion module is connected to the input terminal of the integrator unit. The output terminal of the integrator unit is connected to the input terminal of the voltage follower module. The output terminal of the voltage follower module is connected to the input terminal of the analog voltage output module. The voltage follower module is used to isolate the output of the integrator unit and the input of the analog voltage output module. The analog voltage output module is used to output the analog voltage signal converted from the PWM signal.

2. The DAC signal conversion circuit for a DC motor according to claim 1, characterized in that, The power supply voltage conversion module includes a first voltage conversion module and a second voltage conversion module; The input terminal of the first voltage conversion module is used to receive PWM signals, and the output terminal of the first voltage conversion module is connected to the input terminal of the second voltage conversion module. The output of the second voltage conversion module is connected to the input of the integration unit.

3. The DAC signal conversion circuit for a DC motor according to claim 2, characterized in that, The integration unit includes a first integration unit and a second integration unit; The input terminal of the first integration unit is connected to the output terminal of the second voltage conversion module, and the output terminal of the first integration unit is connected to the input terminal of the second integration unit. The output of the second integrator unit is connected to the input of the voltage follower module.

4. The DAC signal conversion circuit for a DC motor according to claim 3, characterized in that, The first voltage conversion module includes a transistor Q1, resistors R1, R2, and R3, and an input constant voltage source V1; The base of transistor Q1 receives the PWM signal through resistor R1, and the base of transistor Q1 is grounded through resistor R2; The emitter of transistor Q1 is grounded; The collector of the transistor Q1 is connected to the positive terminal of the input constant voltage source V1 through resistor R3; The negative terminal of the input constant voltage source V1 is grounded.

5. The DAC signal conversion circuit for a DC motor according to claim 4, characterized in that, The second voltage conversion module includes transistor Q2, resistors R4, R5, R6, and R7; The base of transistor Q2 is connected to the collector of transistor Q1 through resistor R6, and the base of transistor Q2 is grounded through resistor R7. The emitter of transistor Q2 is grounded; The collector of the transistor Q2 is connected to the positive terminal of the input constant voltage source V1 through resistors R4 and R5, and resistors R4 and R5 are connected in parallel.

6. The DAC signal conversion circuit for a DC motor according to claim 5, characterized in that, The first integration unit includes a resistor R8 and a capacitor C1. One end of the resistor R8 is connected to the collector of the transistor Q2, and the other end of the resistor R8 is grounded through the capacitor C1.

7. The DAC signal conversion circuit for a DC motor according to claim 6, characterized in that, The second integration unit includes a resistor R9 and a capacitor C2. One end of the resistor R9 is connected to a resistor R8, and the other end of the resistor R9 is grounded through the capacitor C2.

8. The DAC signal conversion circuit for a DC motor according to claim 7, characterized in that, The voltage follower module includes an operational amplifier U1 and an input constant voltage source V2; The positive input terminal of the operational amplifier U1 is connected to the other end of the resistor R9, and the negative input terminal of the operational amplifier U1 is connected to the output terminal of the operational amplifier U1. The positive input terminal of the operational amplifier U1 is connected to the positive terminal of the input constant voltage source V2, the negative input terminal of the operational amplifier U1 is grounded, and the negative terminal of the input constant voltage source V2 is grounded. The output terminal of the operational amplifier U1 is connected to the input terminal of the analog voltage output module, and the output terminal of the operational amplifier U1 outputs an analog voltage.

9. The DAC signal conversion circuit for a DC motor according to claim 8, characterized in that, The analog voltage output module includes a resistor R10, one end of which is connected to the output terminal of the operational amplifier U1, and the other end of which is grounded.

10. The DAC signal conversion circuit for a DC motor according to claim 9, characterized in that, The value of the input constant voltage source V2 is set to be greater than or equal to the output voltage of the operational amplifier U1.

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