Among the circuit design, the full bridge is very important. When the four diodes in the bridge rectifier circuit are packaged together, the full bridge circuit is constituted, and the full bridge circuit is actually the H-bridge circuit we often say. This article will mainly introduce the working principle of H-bridge motor drive, and conduct comprehensive analysis from counterclockwise and clockwise needles.
Figure 1 H Bridge Motor Drive Circuit
Figure 1 shows a typical DC motor control circuit. The circuit has been named "H Bridge Drive Circuit" because its shape is like a letter H. 4 triodes constitute the 4 vertical legs of H, while the motor is the horizontal bar (Note: Figure 1) is only a schematic diagram, not a complete circuit diagram, wherein the drive circuit of the triode is not drawn.
As shown in the figure above, the H bridge motor drive circuit includes four triodes and a motor. To operate the motor, you must turn on a pair of triodes on the diagonal. According to the conduction of different triode pairs, the current may flow from left to right or from right to left to left the motor to control the steering of the motor.
To operate the motor, a pair of triodes on the diagonal must be turned on. For example, as shown in FIG. 2, when the Q1 tube and the Q4 tube are turned on, the current passes from the left to the left to the right from the left to right from the power supply positive electrode, and then returns to the power supply negative electrode. According to the current arrow in the figure, the flow of the flow direction will drive the motor clockwise.
Figure 2 H-bridge circuit drive motor clockwise
When the triodes Q1 and Q4 are turned on, the current will flow from the left to right, so that the drive motor is rotated in a specific direction (the arrow around the motor indicates the clockwise direction).
Figure 3 H-bridge circuit drive motor counterclockwise rotation
Figure 3 shows the other pair of triodes Q2 and Q3 on which the current will flow from the right to left.
When the triodes Q2 and Q3 are turned on, the current flows from the right to left through the motor, so that the motor is rotated in the other direction (the arrow around the motor is expressed as a counterclockwise direction).
Enable control and direction logic
When driving the motor, it is important to ensure that the triodes on the H bridge do not turn on at the same time. If the triodes Q1 and Q2 are turned on simultaneously, the current will be directly returned to the negative electrode from the positive electrode through the two triodes. At this time, there is no other load in the circuit except for the triode, the current on the circuit may reach the maximum (this current is only limited by power supply performance), even burn-critical triodes.
Figure 4 has an H-bridge circuit that enables control and direction logic
Based on the above reasons, the switch of the triode is usually controlled in the actual drive circuit. Figure 4 shows the improved circuit based on this consideration, which increases four and two non-doors based on the basic H-bridge circuit. 4 with a "enable" on the door, so that the switch of the entire circuit can be controlled with this signal. Two non-gates can provide one-to-side legs on the h-bridge to be turned on. (Like the previous schematic, Figure 4 is not a complete circuit diagram, especially in the figure, and the door and triode are directly connected to normal.)
With the above method, the operation of the motor requires only three signal controls: two direction signals and a enable signal. If the DIR-L signal is 0, the DIR-R signal is 1, and the enable signal is 1, then the triodes Q1 and Q4 are turned on, and the current flows from the left to right through the motor (as shown in Figure 5); if DIR-L The signal becomes 1, and the DIR-R signal becomes 0, and the Q2 and Q3 will turn on, and the current flows through the motor.
Figure 5 enables the use of signals and directional signals
When actually use, it is very troublesome to make H bridges with discrete parts. It is good to have many packaging H-bridge integrated circuits on the market, which can be used on the power supply, motor and control signals, in the rated voltage and It is very convenient and reliable in the current. For example, common L293D, L298N, TA7257P, SN754410, and the like.
The H-bridge circuit is often applied to the inverter circuit and DC motor circuit, where we only explain the application principle of the H-bridge circuit in the DC motor. I hope that you can fully grasp the basis of all the basic knowledge of the full bridge circuit, which is not only the fast design of the design can also help us consolidate the basics. , Reading the full text, the technology area
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