With the development of power electronics technology and new permanent magnet materials, DC motors , with their good linear characteristics and excellent control performance, have been widely used in most fields of variable speed motion control and closed-loop servo control systems (such as robots, precision machine tools, automotive electronics, home appliances and industrial processes).
Currently, digital control of DC motors has become a mainstream trend, and most high-performance motor control algorithms are implemented through main control chips. With the emergence of high-speed, multi-functional digital signal processors (DSPs), more complex motor control strategies have become possible. This paper presents an H-bridge drive control design for a DC motor using the TMS320F28335 as the main control chip, the IRF530 as the driver chip, and the IR2110 as the drive control chip. This control achieves excellent results and has high practical value.
1. DC motor drive principle
There are many ways to drive DC motors. Ready-made driver chips include 33886, L298N, and TB6539, all of which are based on the H-bridge principle. For designing high-power drives, it's necessary to build an H-bridge driver from discrete components. The H-bridge driver circuit can easily achieve four-quadrant operation of the motor, and its principle topology is shown in Figure 1. The four switching transistors in the H-bridge driver circuit operate in switching states: K1 and K4 form one group, and K2 and K3 form another. The two groups of switching transistors operate in complementary states. When K1 and K4 are on and K2 and K3 are off, a forward voltage is applied across the motor to achieve forward rotation; when K2 and K3 are on and K1 and K4 are off, a reverse voltage is applied across the motor to achieve reverse rotation. In actual control, the motor can switch between the four quadrants. The four diodes D1~D4 in the circuit are freewheeling diodes used to protect the switching elements.
2. Hardware Circuit Design
The overall idea of the hardware circuit design is to control the forward and reverse rotation of the motor by using PWM waves to control the on and off of switches K1, K4, K2, and K3 in Figure 1. By changing the duty cycle of the PWM waves, the motor receives different voltages, thereby controlling the speed of the motor.
2.1 Selection of Switching Components
Switching elements can be selected from bipolar transistors or field-effect transistors. Since power MOSFETs are voltage-controlled devices, they feature high input impedance, fast switching speed, and no secondary breakdown, meeting the requirements for high-speed switching. In this design, all four switches use IRF530 N-channel enhancement-mode power MOSFETs from IR, with a drain current of 14A and the ability to withstand a single-pulse current of 49A. The maximum voltage is 100V, and the on-resistance is no greater than 0.16Ω, meeting the driving requirements.
2.2 Selection of MOSFET gate driver device
IR offers a variety of bridge driver integrated circuit chips, with the IR2110 being a typical example. This chip is a monolithic integrated driver module for dual-channel, gate-driven, high-voltage, high-speed power devices. Due to its highly integrated level-shifting technology, it greatly simplifies the control requirements of the power devices on the logic circuit, while simultaneously improving the reliability of the driver circuit. In particular, the use of an external bootstrap capacitor for the upper transistor significantly reduces the number of power supplies required compared to other IC drivers. This design uses the IR2110 from IR as the driver chip.
The IR2110 operates at frequencies up to 500kHz, with a logic power supply voltage range of 5V to 15V. Its floating power supply uses a bootstrap circuit, and the maximum power drive voltage can reach 500V. It allows for a ±5V offset between the logic circuit reference ground and the power circuit reference ground. Both its logic and power terminals can operate using a single 15V power supply, simplifying the design. A typical application circuit diagram of the IR2110 is shown in Figure 2.
In Figure 2, C1, C3, and C4 are capacitors between the power supply and ground, respectively. Their function is to prevent large voltage fluctuations by utilizing the energy stored in the capacitor. Generally, they are chosen from 10μF to 100μF depending on the specific situation (10μF is used in this design). R1 and R2 are both 1kΩ. C2 is the bootstrap capacitor. VCC charges C2 through D1, C2, the load, and T2 to ensure that when T2 is off and T1 is on, the gate of transistor T1 is driven by sufficient energy stored in C2. The bootstrap capacitor is generally 1.0μF, but the specific value depends on the PWM frequency. For lower frequencies, a larger capacitor is used; for higher frequencies, a smaller capacitor is used. This design uses a 1.0μF electrolytic capacitor. It should be noted that if the bootstrap capacitor value is inappropriate, it will result in failure to bootstrap. For specific capacitance calculations, please refer to the references.
In Figure 2, D1 is a protection diode. Its function is to prevent high voltage from entering the VCC terminal and damaging the driver chip when T1 is conducting. D1 should be a fast recovery diode with low on-resistance to reduce charging time, such as 1N4148, FR series, or MUR series. This design uses 1N4148.
2.3 Selection of Switching Frequency
The frequency of the PWM wave will affect whether the motor can output maximum torque and the smoothness of the torque. Here, we mainly consider the maximum torque. To obtain the maximum output torque, the direction of the rotor magnetic poles must be known, that is, the position of the rotor must be determined. This can be temporarily disregarded for the small DC motor in this design. In order to avoid the motor emitting relatively large noise, the frequency of the PWM wave should be kept outside the sound wave range as much as possible. On the other hand, due to the inductive nature of the motor windings, the higher the frequency, the greater the inductive reactance, and the higher the frequency, the smaller the motor torque [9]. After analysis and comparison, the motor frequency finally determined in this paper is 250Hz. Although there is some low-frequency noise, the output torque effect is very good.
2.4 Controller Selection
Currently, there are several ways to generate PWM waves. They can be generated using dedicated PWM wave generation chips or by microcontrollers (such as microcontrollers, ARM processors, DSPs, FPGAs, etc.). This paper selects the TI TMS320F28335 DSP as the microcontroller, which is the core component of the entire control system, and its performance largely determines the stability of the entire hardware system. The TMS320F28335 is a 32-bit floating-point DSP with a working frequency of 150MHz and 12 PWM outputs, 6 of which are high-precision PWM wave channels, making it very suitable for motor control.
2.5 Overall Design of Drive Control Circuit
Based on the selection of the above key components, the drive control hardware circuit diagram shown in Figure 3 is designed.
The PWM wave is generated by the DSP's PWM function and then sent to the optocoupler TLP521 through a 180-ohm resistor R5. Since the PWM wave frequency in this design is not high, a standard optocoupler TLP521 is sufficient.
In Figure 3, the "NOT gate" and "NAND gate" are not only required for logic control, but also play a role in shaping the output waveform signal of the optocoupler.
T1~T4 are driven by an H-bridge consisting of four IRF530 chips to control the motor M. The gate drive of the IRF530 is accomplished by two IR2110 chips. The HIN of one IR2110 chip and the LIN of the other chip are connected together. A PWM control signal is used to drive the upper and lower bridge arm MOSFETs of the motor.
The SD pins of the two IR2110 chips are connected together and controlled by the GPIO9 pin of the DSP through the optocoupler G8. The chips work normally when GPIO9 is low.
When the DSP's GPIO8 pin is high, the output of gate G4 is valid, and the motor rotates forward; otherwise, the output of gate G3 is valid, and the motor rotates in reverse. Therefore, the forward and reverse rotation of the motor can be easily controlled by the DSP's GPIO8.
In addition, as can be seen from Figure 3, the positive pulse output by the DSP is also a positive pulse when it is transmitted to the control terminal of the IR2110. Therefore, the speed of the DC motor can be directly controlled by the magnitude of the PWM wave duty cycle.
3. Circuit testing
Based on the above design, a PWM wave is generated by the DSP, input to the IR2110 through the logic circuit, thereby controlling the on/off state of the IRF530. Adjusting the duty cycle of the PWM wave can control the speed of the motor.
The duty cycle controls the motor speed. In the circuit, C1 and C6 are 10μF, C2-C5 are 1μF, D1-D6 are 1N4148 diodes, R1-R4 are 1kΩ, R5 is 180Ω, R6 is 10kΩ, the inverter is 74LS04, the NAND gate is 74LS00, the logic voltage is +5V, the gate drive voltage is +12V, and the motor voltage is +5V. All three power supplies share a common ground, but the DSP power supply is isolated. A motor with model number RN260-CN38-18130 was tested with a PWM wave frequency of 250Hz and a duty cycle of 50%. The oscilloscope used for testing was an Antex ADS1102C.
Figure 4 shows the signal after passing through a NAND gate and an inverter, which is also the control signal of the IR2110. It can be seen that after the signal passes through the gate circuit, not only is the interference greatly reduced, but the waveform is also more regular and flat.
The gate-source voltage of the lower bridge arm is easy to control, but the gate-source voltage of the upper bridge arm is formed by the bootstrap circuit. This is because when the upper bridge arm is turned on, the source voltage is basically equal to the power supply voltage of the drive motor. In order for the MOSFET of the upper bridge arm to continue to conduct, the gate voltage must rise along with the source voltage. No matter what the source voltage is, the gate-source voltage must remain unchanged. This makes the gate voltage fluctuate with the source voltage.
Figure 5(a) shows the source-to-ground voltage signal of the upper bridge arm, and Figure 5(b) shows the gate-to-ground voltage signal of the upper bridge arm. It can be seen that the source voltage changes with the PWM wave, with an average voltage fluctuation of 4.6V; while the gate voltage fluctuates accordingly with the source voltage, with a peak-to-peak value of 17.6V, which is approximately 13V relative to the source voltage, ultimately making the gate-source voltage a stable value.
Overall test results show that the DC motor operates smoothly and is precisely controlled, meeting the design requirements.
This paper presents the complete design of H-bridge drive control for a DC motor. The IRF530 power MOSFET chip is used as the switching element, and the IR2110 is used as the gate drive control for the MOSFET. A DSP generates a PWM signal, which is then sent to the IR2110 via optocouplers and logic control. The upper bridge arm drive voltage is successfully float-controlled, allowing for convenient start-stop and forward/reverse control. The motor runs smoothly and well, achieving the design objectives. The drive control circuit presented in this paper is also suitable for other similar applications and has significant practical reference value.
