01 H-bridge circuit foundation
1 Introduction
You may have appreciated the line-offline information to build H-bridge circuits, after all, these circuits are relatively simple. However, some data describes the H-bridge circuit is relatively precise, but some are a little bit. When you actually use the bridge circuit, you will be aware that many circuit features do not have clearly explained in the network information. The following information is from the "H-bridge circuit foundation" [1] The content of the network article, the author writes in the process of "UM-H Bridge" circuit, is full of principles and applications of H-bridge circuits Passionate introduction.
▲ UM-H bridge circuit module made by the article
Although the author tries to avoid more in-depth theories such as H-bridge circuit, motor control principle, it is desirable to be familiar with the characteristics of basic electronic components (such as resistance, capacitance, inductor, circuit network principles, etc.). I understand that he has been simplified and passed through the legend, the table is combed.
2. Basic structure
H-bridge circuit and complex are like Chinese Chinese characters "" Japanese "" word, if it removes the upper and lower power supplies and the bottom line, the circuit structure is similar to the English letters "" H "". The upper and lower sides of the circuit have been placed in the power transistor "" " "Electronic Switch", load (usually power devices: such as motor), in the middle of the left and right electronic switches. The circuit network structure is the same as "Whell Power Bridge" [2]. Two group switches are called two ** half bridges.
**
▲ H-bridge circuit basic structure
Power electronic switches (Q1, Q2, Q3, Q4) typically use a bipolar power triode, or a field effect (FET) transistor. The insulated gate bipolar transistor (IGBT) is used in special high pressure situations. Four parallel diodes (D1, D2, D3, D4) are often referred to as clamping diodes, usually using Schottky diodes. Many power MOS managers are also integrated with internal reverse conducting diodes. The power supply is connected to the power supply to the H-bridge circuit.
The four power switches can be controlled by the drive circuit or closed. There should be some kinds of switching status combinations of the four power tubes in nature, but only several of these different combinations can be truly safe for load power control.
The bridge circuit can control a lot of loads, but usually use the pulse width modulation (PWM) drive waveform to perform efficient control of DC motor, bipolar step motor or the like.
02 working mode
Static working state
The following shows the different drive power mode of the four power switches of the bridge circuit to the load provided for the load provided.
For example, in the lower right (Q1, Q4) transistor closed, the upper right upper left (Q3, Q4) transistor is disconnected, and a left right-negative supply voltage (Ignore the conduction voltage of the transistor) is applied to the load. The motor is forward.
▲ H-bridge circuit drive motor forward voltage
The following figure is the opposite case, and the power supply voltage of the opposite model is applied to the motor load by the turning on the ones of Q3, Q2, Q1, Q4. The motor is reversed.
▲ H-bridge circuit drive motor reverse voltage
There are also some combination modes that do not supply power to the motor. For example, when the four crystal switches are disconnected, the motor load is equivalent to the duration of both ends. If the motor is moving at this time, the kinetic energy of its rotor will gradually consume under the friction, and the motor is slowly stopped.
The two cases shown in the figure below: the two transistors of the upper half of the H-bridge circuit are closed, and the corresponding two transistors are disconnected. At this time, the two ends of the motor are actually shorted together. The motor is 0 in both ends of the motor. If the motor is moving at this time, the kinetic energy of the rotor will form brake current in the external short-circuit bridge circuit circuit by the resulting reverse electromotive (EMF), and the electric machine is quickly braked.
▲ The voltage of the motor is forced to be compressed by the bridge circuit.
There are also some combinations that need to be resolutely avoided. For example, the above-described two transistors are simultaneously turned on when the upper and lower transistors on the side of the H-bridge circuit (simultaneous disconnection is allowed), and the power supply will form a short circuit loop through these two transistors. The huge short-circuit currents will be burn these two transistors without polite.
▲ H-bridge circuit straight
The short circuit of the same side bridge is sometimes the control signal is not good (there is no feet time), sometimes the power device is not strong enough (the pressure is not being broken enough). However, due to the relationship to the life and death of the H-bridge circuit, it is necessary to avoid it.
2. Control two PWM modes of the motor
The most occasive occasion of the bridge circuit is to control motor movements (such as Tesla Electric Vehicle Drive Circuits). The motor load can be described in series using resistor Rm, inductance LM, and inductive electromotive force VG. The rotational torque required for the motor movement is generated by the armature current flowing through the series circuit, and the armature current is generated by a voltage applied to the series circuit.
Since the motor itself has an energy storage inertial link (including the inertia of the mechanical energy storage component rotor), the effect of the torque is generated when using a high frequency pulse voltage (PWM) acts on both ends of the motor. It is actually determined by the average value of the pulse voltage.
▲ Equivalent model of motor
In order to generate different poles of the drive motor, the voltage of different amplitudes, the control motor PWM waveform has two working modes:
Polarity-Magnitude Drive, also known as a single pole drive mode: the signal of the drive motor has a pulse signal for controlling the direction of the H-bridge output polarity and the control of the PWM duty cycle; PWM When the duty cycle is 0, the output voltage is 0.
▲ polarity-amplitude drive mode bridge circuit output and load voltage current waveform
Interlock phase drive mode, also known as a bipolar drive mode: the bridge circuit is driven by polar opposite PWM signals. When the PWM duty cycle is 50%, the output average voltage is 0.
▲ Interlock phase drive mode The output of the bridge circuit and the voltage current waveform of the load
In a single pole (polar-amplitude) drive mode, the H-bridge circuit only has only two transistors to do high-frequency switching operations, and the circuit loss is small. However, due to the existence of the resistance in the loop, it is no longer a linear relationship between the motor current and the PWM waveform. It can be found that the circuit experiment results in the analysis of the "Analysis of the Magnet Drive Inverse Sepreofable Strip Team" [3].
In the bipolar (interlock phase) drive mode, four power transistors need to do high-frequency switching operations at the same time, and the circuit losses are relatively large. However, the current output of the circuit control load is a linear relationship.
The figure below gives the current circuit in the bipolar drive mode and the forward current and the reverse period. Since the two processes are only the opposite of the polar, the voltage is the same, so the average current of the motor and the duty cycle of the PWM have a linear proportional relationship.
▲ The motor is turned on and reversing the loop in the bipolar PWM drive
The bipolar PWM mode can also allow the motor to operate in a four-term limit (forward operation, forward power generation, reverse operation, reverse power generation), which is more efficient when driving high power motors.
The original author gives the relationship between the current and PWM duty cycle of the motor load in two PWM mode in "Sign-Magnitude Drive" [4] and "Lock Anti-Phase Drive" blog. In order to unwound the general readers of this article, there is no longer to reference a lot of conclusions here. Interested students can derive themselves, or see the original text.
03 power supply
The power supply of the bridge circuit usually has a large capacity energy storage capacitor to stabilize the supply voltage, and the bridge circuit is referred to as a voltage working mode. Correspondingly, there is also a bridge circuit that is larger capacity wave inductance on the voltage source line. At this time, it is usually used to perform inverter power supply, referred to as a current mode of operation.
The energy storage capacitors of the bridge circuit need to be considered:
Does it need to be able to live in a back current generated by HOLD?
Can the circuit tolerate how much voltage fluctuations?
What is the switching frequency of the bridge circuit?
▲ H-bridge circuit with filter capacitor
The figure below shows the working current waveform of the bridge circuit in the PWM phase period of the bridge circuit due to the inductance in the motor. It can be seen that in some cases, the bridge circuit will reverse the power supply into the current.
▲ Motor current and bridge circuit operating current waveform
If there is no current feedback control for the motor load, the parallel capacitance of the bridge circuit needs to be taken, in order to mitigate fluctuations caused by the surge current from the motor during sudden acceleration and deceleration. The figure below gives the bridge circuit capacitance and the power supply to provide a working current.
▲ Bridge circuit parallel capacitor is powered by the bridge circuit together
The original author got up his bridge circuit trilogy in the three songs of the road also discussed the current waveform and analysis formula under the "Transition Process", "Brake Process", "Steady State State" under the Bridge Circuit. In particular, there are two different states of "dynamic brakes" corresponding to the motor in the braking process, and the "power generation brake" is specifically affecting the impact of power supply.
04 after
Although we cannot confirm all the conclusions of the original author, the formula is correct. But seeing his clear discourse, vivid illustration, detailed formula analysis reflects that from a principle and some control details of the links that need to design a small motor H-bridge circuit drive project, the principle and some control details of the part of the Siqiao circuit work, And finally summarize into a blog post. You can experience the joy of his inner intellectual growth.
Maybe everyone will have this joy. Record, express this harvest joy may continue to motivate you to move forward. More importantly, these records may inspire your new ideas when you encounter new questions in your future.
Reference
[1]
"H-bridge circuit foundation": http://modularcircuits.tantosonline.com/blog/articles/h-bridge-secrets/h-bridges-the-basics/
[2]
"Wheight Bridge": https://baike.baidu.com/Item/%E6%83% A0%E6%96 %AF%E9%80%9A%E7%94%B5%E6%A1%A5// 11019183? Freish =% E7% 94% B5% E6% A1% A5 & fromID = 6424787 & fr = aladdin
[3]
"Analysis of the magnet drive reverse continuation stream of string resistance": https://zhuoqing.blog.csdn.net/Article/details/107540914
[4]
"Sign-Magnitude Drive": http://modularcircuits.tantosonline.com/blog/articles/h-bridge-secrets/sign-magnitude-drive/
Original title: H-bridge circuit
Article Source: [WeChat public number: FPGA Getting Started] Welcome to add attention! Please indicate the source of the article. , Read the full article, original title: H-bridge circuit
Article Source: [Micro Signal: xiaojiaoyafpga, WeChat public number: e-wood] Welcome to add attention! Please indicate the source of the article.
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