12/29/2022 0 Comments Optical isolator ic 10kv![]() ![]() This can switch the gate on and off when not intended, damaging the MOSFETs. However, a problem can occur when large transient gate-drive currents flowing in the inductive coils cause ringing. Pulse transformer half-bridge gate driver. In this application, pulse transformers have the advantage of not requiring isolated power supplies to drive the secondary side MOSFETs. #Optical isolator ic 10kv driver#Here, the gate driver differentially drives the primary of the pulse transformer the two secondary windings drive each gate of a half bridge. A gate-driver IC can be used to deliver the high currents needed for charging the capacitive MOSFET gates. In Figure 3, a pulse transformer is used it can operate at the speeds often needed for half-bridge gate-driver applications (up to 1 MHz). Their lower propagation delays and more accurate timing can provide a speed advantage over optocouplers. Next, consider circuits where the galvanic isolation is provided by transformer coupling. To run an optocoupler near its maximum speed, the LED current must be increased to more than 10 mA, consuming more power and reducing the optocoupler’s lifetime and reliability-especially in the high-temperature environments common in solar inverter and power supply applications. The optocoupler’s response speed is limited by the capacitance of the primary side light-emitting diode (LED) while driving the output to speeds up to 1 MHz, it will also be limited by its propagation delay (500 ns max) and slow rise and fall times (100 ns max). ![]() Dual optocoupler half-bridge gate driver. Allowing for this mismatch will increase the required dead time between switching one channel off and turning the other channel on, reducing efficiency. Note also that the optocouplers are manufactured separately, even if two are packaged together, limiting the ability to match the two channels. The gate-driver circuit is often included in the same package as the optocoupler, so two separate optocoupler-gate-driver ICs are commonly required to complete the isolated half bridge-increasing the physical solution size. #Optical isolator ic 10kv drivers#Optocoupler Gate DriverĪnother approach, shown in Figure 2, avoids the problems of high-side to low-side interactions by using two optocouplers and two gate drivers to establish galvanic isolation between the outputs. ![]() When this happens, the high-side driver can latch up and become permanently damaged. Parasitic inductance in the circuit can cause the output voltage, V S, to go below ground during a low-side switching event. Another concern is that high-voltage gate drivers do not have galvanic isolation instead, they rely on the IC’s junction isolation to separate the high-side drive voltage from the low-side drive voltage. A potential drawback of this circuit is that the single isolated input channel relies on the high-voltage driver circuit for the needed channel-to-channel timing match, as well as the required dead time. High-voltage half-bridge gate driver.Īs shown, a conventional approach to implementing this function uses an optocoupler for isolation, followed by a high-voltage gate-driver IC. For accuracy and efficiency, the high- and low-side drivers need very closely matched timing characteristics in order to reduce the dead time when one switch of the half bridge turns off before the second switch turns on. The drivers must have low output impedance, to reduce conduction losses, and fast switching-to reduce switching losses. This article will discuss details of these design concepts to illustrate the ability of isolated half-bridge gate driver ICs to provide high performance in a small package.Ī basic half-bridge driver with optocoupler isolation, shown in Figure 1, controls output power by driving the gates of high- and low-side N-channel MOSFETs (or IGBTs) with signals of opposite polarity. Many applications, ranging from isolated dc-to-dc power supply modules that call for high power density and efficiency, to solar inverters, where high isolation voltage and long-term reliability are critical, use isolated half-bridge gate drivers to control large amounts of power. Implementing an Isolated Half-Bridge Gate Driver ![]()
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