An H bridge is an electronic circuit that switches the polarity of a voltage applied to a load. These circuits are often used in robotics and other applications to allow DC motors to run forwards or backwards.[1]
Most DC-to-AC converters (power inverters),most AC/AC converters,the DC-to-DC push–pull converter,most motor controllers,and many other kinds of power electronics use H bridges.In particular, a bipolar stepper motor is almost invariably driven by a motor controller containing two H bridges.
3Construction
7External links
General[edit]
How to use MOSFET DRIVER IR2110. Compete circuit diagrams of H bridge are shown below. I have used IR2210 MOSFET gate driver circuit. In H bridge Two MOSFETS are used as High side MOSFETS and two used as a low side MOSFETS. IR2210 high and low side drivers outputs are used to drive these MOSFET. Circuit diagram of h bridge using IR2110.
Structure of an H bridge (highlighted in red)
H bridges are available as integrated circuits, or can be built from discrete components.[1]
The term H bridge is derived from the typical graphical representation of such a circuit. An H bridge is built with four switches (solid-state or mechanical). When the switches S1 and S4 (according to the first figure) are closed (and S2 and S3 are open) a positive voltage will be applied across the motor. By opening S1 and S4 switches and closing S2 and S3 switches, this voltage is reversed, allowing reverse operation of the motor.
Using the nomenclature above, the switches S1 and S2 should never be closed at the same time, as this would cause a short circuit on the input voltage source. The same applies to the switches S3 and S4. This condition is known as shoot-through.
Operation[edit]
The two basic states of an H bridge
The H-bridge arrangement is generally used to reverse the polarity/direction of the motor, but can also be used to 'brake' the motor, where the motor comes to a sudden stop, as the motor's terminals are shorted, or to let the motor 'free run' to a stop, as the motor is effectively disconnected from the circuit. The following table summarises operation, with S1-S4 corresponding to the diagram above.
S1
S2
S3
S4
Result
1
0
0
1
Motor moves right
0
1
1
0
Motor moves left
0
0
0
0
Motor coasts
1
0
0
0
0
1
0
0
0
0
1
0
0
0
0
1
0
1
0
1
Motor brakes
1
0
1
0
x
x
1
1
Short circuit
1
1
x
x
Construction[edit]
L298 dual H bridge motor driver
Relays[edit]
One way to build an H bridge is to use an array of relays from a relay board.[2]
A 'double pole double throw' (DPDT) relay can generally achieve the same electrical functionality as an H bridge (considering the usual function of the device). However a semiconductor-based H bridge would be preferable to the relay where a smaller physical size, high speed switching, or low driving voltage (or low driving power) is needed, or where the wearing out of mechanical parts is undesirable.
Another option is to have a DPDT relay to set the direction of current flow and a transistor to enable the current flow. This can extend the relay life, as the relay will be switched while the transistor is off and thereby there is no current flow. It also enables the use of PWM switching to control the current level.
N and P channel semiconductors[edit]
H bridge with N channel MOSFET's
A solid-state H bridge is typically constructed using opposite polarity devices, such as PNP bipolar junction transistors (BJT) or P-channel MOSFETs connected to the high voltage bus and NPN BJTs or N-channel MOSFETs connected to the low voltage bus.
N channel-only semiconductors[edit]
The most efficient MOSFET designs use N-channel MOSFETs on both the high side and low side because they typically have a third of the ON resistance of P-channel MOSFETs. This requires a more complex design since the gates of the high side MOSFETs must be driven positive with respect to the DC supply rail. Many integrated circuit MOSFET gate drivers include a charge pump within the device to achieve this.
Alternatively, a switched-mode power supply DC–DC converter can be used to provide isolated ('floating') supplies to the gate drive circuitry. A multiple-output flyback converter is well-suited to this application.
Another method for driving MOSFET-bridges is the use of a specialised transformer known as a GDT (gate drive transformer), which gives the isolated outputs for driving the upper FETs gates. The transformer core is usually a ferrite toroid, with 1:1 or 4:9 winding ratio. However, this method can only be used with high frequency signals. The design of the transformer is also very important, as the leakage inductance should be minimized, or cross conduction may occur. The outputs of the transformer are usually clamped by Zener diodes, because high voltage spikes could destroy the MOSFET gates.
Variants[edit]
A common variation of this circuit uses just the two transistors on one side of the load, similar to a class AB amplifier. Such a configuration is called a 'half bridge'.[3] The half bridge is used in some switched-mode power supplies that use synchronous rectifiers and in switching amplifiers. The half-H bridge type is commonly abbreviated to 'Half-H' to distinguish it from full ('Full-H') H bridges. Another common variation, adding a third 'leg' to the bridge, creates a three-phase inverter. The three-phase inverter is the core of any AC motor drive.
A further variation is the half-controlled bridge, where the low-side switching device on one side of the bridge, and the high-side switching device on the opposite side of the bridge, are each replaced with diodes. This eliminates the shoot-through failure mode, and is commonly used to drive variable or switched reluctance machines and actuators where bi-directional current flow is not required.
Commercial availability[edit]
There are many commercially available inexpensive single and dual H-bridge packages, of which the L293x series includes the most common ones. Few packages, like L9110,[4] have built-in flyback diodes for back EMF protection.
Operation as an inverter[edit]
A common use of the H bridge is an inverter. The arrangement is sometimes known as a single-phase bridge inverter.
The H bridge with a DC supply will generate a square wave voltage waveform across the load. For a purely inductive load, the current waveform would be a triangle wave, with its peak depending on the inductance, switching frequency, and input voltage.
See also[edit]
References[edit]
^ abAl Williams (2002). Microcontroller projects using the Basic Stamp (2nd ed.). Focal Press. p. 344. ISBN978-1-57820-101-3.
^'Relay H-bridge (Relay Motor controller)'. 11 December 2012.
^''The Half-bridge Circuit Revealed (2012)'.
^'wordpress.com'(PDF).
External links[edit]
Projects[edit]
H-bridge motor control with 4017 (in Turkish)
Retrieved from 'https://en.wikipedia.org/w/index.php?title=H_bridge&oldid=934490978'
A gate driver is a power amplifier that accepts a low-power input from a controller IC and produces a high-current drive input for the gate of a high-power transistor such as an IGBT or power MOSFET. Gate drivers can be provided either on-chip or as a discrete module. In essence, a gate driver consists of a level shifter in combination with an amplifier. A gate driver IC serves as the interface between control signals (digital or analog controllers) and power switches (IGBTs, MOSFETs, SiC MOSFETs, and GaN HEMTs). An integrated gate-driver solution reduces design complexity, development time, bill of materials (BOM), and board space while improving reliability over discretely-implemented gate-drive solutions.[1]
History[edit]
In 1989, International Rectifier (IR) introduced the first monolithic HVIC gate driver product, the high-voltage integrated circuit (HVIC) technology uses patented and proprietary monolithic structures integrating bipolar, CMOS, and lateral DMOS devices with breakdown voltages above 700 V and 1400 V for operating offset voltages of 600 V and 1200 V. [2] Later in 2015, International Rectifier (IR) was bought by Infineon Technologies.
Using this mixed-signal HVIC technology, both high-voltage level-shifting circuits and low-voltage analog and digital circuits can be implemented. With the ability to place high-voltage circuitry (in a ‘well’ formed by polysilicon rings) , that can ‘float’ 600 V or 1200 V, on the same silicon away from the rest of the low-voltage circuitry, high-side power MOSFETs or IGBTs exist in many popular off-line circuit topologies such as buck, synchronous boost, half-bridge, full-bridge and three-phase. The HVIC gate drivers with floating switches are well-suited for topologies requiring high-side, half-bridge, and three-phase configurations.[3]
Purpose[edit]
In contrast to bipolar transistors, MOSFETs do not require constant power input, as long as they are not being switched on or off. The isolated gate-electrode of the MOSFET forms a capacitor (gate capacitor), which must be charged or discharged each time the MOSFET is switched on or off. As a transistor requires a particular gate voltage in order to switch on, the gate capacitor must be charged to at least the required gate voltage for the transistor to be switched on. Similarly, to switch the transistor off, this charge must be dissipated, i.e. the gate capacitor must be discharged.
When a transistor is switched on or off, it does not immediately switch from a non-conducting to a conducting state; and may transiently support both a high voltage and conduct a high current. Consequently, when gate current is applied to a transistor to cause it to switch, a certain amount of heat is generated which can, in some cases, be enough to destroy the transistor. Therefore, it is necessary to keep the switching time as short as possible, so as to minimize switching loss. Typical switching times are in the range of microseconds. The switching time of a transistor is inversely proportional to the amount of current used to charge the gate. Therefore, switching currents are often required in the range of several hundred milliamperes, or even in the range of amperes. For typical gate voltages of approximately 10-15V, several watts of power may be required to drive the switch. When large currents are switched at high frequencies, e.g. in DC-to-DC converters or large electric motors, multiple transistors are sometimes provided in parallel, so as to provide sufficiently high switching currents and switching power.
The switching signal for a transistor is usually generated by a logic circuit or a microcontroller, which provides an output signal that typically is limited to a few milliamperes of current. Consequently, a transistor which is directly driven by such a signal would switch very slowly, with correspondingly high power loss. During switching, the gate capacitor of the transistor may draw current so quickly that it causes a current overdraw in the logic circuit or microcontroller, causing overheating which leads to permanent damage or even complete destruction of the chip. To prevent this from happening, a gate driver is provided between the microcontroller output signal and the power transistor.
Charge pumps are often used in H-Bridges in high side drivers for gate driving the high side n-channel power MOSFETs and IGBTs. These devices are used because of their good performance, but require a gate drive voltage a few volts above the power rail. When the centre of a half bridge goes low the capacitor is charged via a diode, and this charge is used to later drive the gate of the high side FET gate a few volts above the source or emitter pin's voltage so as to switch it on. This strategy works well provided the bridge is regularly switched and avoids the complexity of having to run a separate power supply and permits the more efficient n-channel devices to be used for both high and low switches.