Introduction to Half-bridge driver chip
The half-bridge driver chip is a core component of power semiconductor drive circuits, primarily used to drive two power switching transistors connected in series in a half-bridge topology, typically MOSFETs or IGBTs. This chip controls the time-sharing conduction of the two transistors to achieve power regulation and energy transfer to the downstream load, making it an indispensable key chip in power electronic devices such as switching power supplies, motor drives, and inverters.
Technical Challenges of Half-Bridge Driver Chips
The inherent characteristics of the half-bridge topology necessitate addressing two major technical challenges for Half-bridge driver chip: First, the floating ground driving problem of the upper arm power transistor-the source (emitter) potential of the upper arm switch dynamically changes with the conduction and cutoff of the lower arm, making direct fixed-potential power supply impossible. Therefore, most half-bridge drivers integrate bootstrap diodes, which, together with external bootstrap capacitors, provide a floating power supply for the upper arm drive circuit. For high-voltage applications, some half-bridge drivers also integrate charge pumps or support isolated power supply to adapt to different application requirements. Secondly, there's the issue of shoot-through protection for the upper and lower bridge arms. If both switching transistors conduct simultaneously, it will cause a direct short circuit in the power supply, damaging the devices. Therefore, qualified half-bridge drivers all have built-in dead-time control logic and integrate overcurrent protection, overtemperature protection, and undervoltage lockout functions to prevent short-circuit faults at the hardware level and improve system reliability.
Classification of Half-Bridge Driver Chips
Based on the differences in power supply and control logic, half-bridge driver chips can be divided into two categories: independent half-bridge drivers and integrated control half-bridge drivers. Independent half-bridge drivers integrate only two drive channels and protection logic, requiring an external PWM controller to input two complementary drive signals. They have strong adaptability and can be paired with different main control chips, flexibly applied to various customized circuits. Integrated control half-bridge drivers integrate PWM generation and feedback regulation functions inside the chip, simplifying peripheral circuit design and are mostly used in standardized, low-cost, small-to-medium power applications. Based on their withstand voltage ratings, low-voltage half-bridge drivers are primarily designed for low-voltage applications below 100V, commonly found in low-voltage servo motor drives, USB-PD fast charging circuits, and low-voltage DC-DC converters. Medium- and high-voltage half-bridge drivers, on the other hand, can withstand hundreds or even thousands of volts, making them suitable for high-voltage applications such as industrial inverters, new energy vehicle power supplies, and frequency converters.
Specific model number of the half-bridge driver chip
The UCC27302A is a robust gate driver designed to drive two N-channel MOSFETs in a half-bridge or synchronous buck configuration with an absolute maximum bootstrap voltage of 120V. Its 3.7A peak source and 4.5A peak sink current capability allows the UCC27302A to drive large power MOSFETs with minimized switching losses during the transition through the Miller Plateau. The switching node (HS pin) can handle negative transient voltage, which allows the high-side channel to be protected from inherent negative voltages caused by parasitic inductance and stray capacitance.
The inputs are independent of supply voltage and are able to withstand -10V and +20V absolute maximum ratings. The low-side and high-side gate drivers are matched to 4ns between the turn on and turn off of each other and are controlled throught the LI and HI input pins respectively. However, the input interlock logic will turn both driver outputs low whenever both LI and HI inputs are high at the same time. An on-chip 120V rated bootstrap diode eliminates the need to add discrete bootstrap diodes. Undervoltage lockout (UVLO) is provided for both the high-side and the low-side drivers which provides symmetric turn on and turn off behavior and forces the outputs low if the drive voltage is below the specified threshold.
Half-bridge driver chip parameters
|
Bootstrap supply voltage (max) (V) |
120 |
|
Power switch |
MOSFET |
|
Input supply voltage (min) (V) |
7 |
|
Input supply voltage (max) (V) |
17 |
|
Operating temperature range (°C) |
-40 to 150 |
|
Undervoltage lockout (typ) (V) |
5 |
|
Rating |
Catalog |
|
Propagation delay time (µs) |
0.02 |
|
Rise time (ns) |
7.2 |
|
Fall time (ns) |
5.5 |
|
Iq (mA) |
0.001 |
|
Input threshold |
TTL |
|
Channel input logic |
TTL |
|
Switch node voltage (V) |
-20 |
|
Features |
Enable, Integrated bootstrap diode, Interlock, Negative Voltage Handling on Input |
|
Driver configuration |
Dual, Noninverting, TTL compatible |
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