SLUAAH0 February   2022 UCC14130-Q1 , UCC14131-Q1 , UCC14140-Q1 , UCC14141-Q1 , UCC14240-Q1 , UCC14241-Q1 , UCC14340-Q1 , UCC14341-Q1 , UCC15240-Q1 , UCC15241-Q1

 

  1.   Trademarks
  2. 1 Introduction
    1. 1.1 Pin Configuration and Functions
  3. 2 Three-Phase Traction Inverter
  4. 3 Gate Drive Bias Requirements
    1. 3.1 Gate Drive Bias Architectures
    2. 3.2 IGBT vs. SiC
    3. 3.3 Determining Required Bias Supply Power
    4. 3.4 Input Voltage Requirements
    5. 3.5 Output Voltage Requirements
  5. 4 Single Positive Isolated Output Voltage
  6. 5 Dual Positive and Negative Output Voltages
  7. 6 Dual Positive Output Voltages
  8. 7 Capacitor Selection
  9. 8 RLIM Current Limit Resistor
    1. 8.1 RLIM Functional Description
    2. 8.2 RLIM Dual Output Configuration
      1. 8.2.1 CVEE Above Nominal Value CVDD Below Nominal Value
      2. 8.2.2 CVEE Below Nominal Value CVDD Above Nominal Value
      3. 8.2.3 Gate Driver Quiescent Current: IQ_VEE > IQ_VDD
      4. 8.2.4 Gate Driver Quiescent Current: IQ_VEE < IQ_VDD
      5. 8.2.5 CVEE Above Nominal Value CVDD Below Nominal Value: IQ_VEE > IQ_VDD
      6. 8.2.6 CVEE Below Nominal Value CVDD Above Nominal Value: IQ_VEE < IQ_VDD
    3. 8.3 RLIM Single Output Configuration
  10. 9 UCC14240-Q1 Excel Design Calculator Tool
  11. 10Thermal Considerations
    1. 10.1 Thermal Resistance
    2. 10.2 Junction-to-Top Thermal Characterization Parameter
    3. 10.3 Thermal Measurement and TJ Calculation Example
  12. 11Enable (ENA) and Power Good (/PG)
  13. 12PCB Layout Considerations
  14. 13Reference Design Example
  15. 14Summary
  16. 15References

3.4 Input Voltage Requirements

UCC14240-Q1 requires a 24-V nominal, DC input voltage within the range of 21 V<VIN<27 V. The 12-V HEV, EV battery is the primary source for generating 24 V and since both reside on the LV side, a non-isolated, DC-DC converter can be used to provide the 24-V needed. The min/max voltage range for most 12-V, EV batteries is typically between 6 V<VBAT<28 V, but can reach as high as 40 V. General purpose PWM controllers from the UCC280x-Q1 family are a good choice because of their wide selection of 12-V compatible UVLO options. These PWMs are automotive temperature rated, AEC-Q100 qualified controllers, available in either 50% or 100% max duty cycle and come in standard 8-pin SOIC packages. A flyback converter compatible with UC14240-Q1 would need to source a minimum of 7.5 W (3x UCC14240-Q1) for high-side only, in a semi-distributed architecture or 15 W for a fully distributed bias architecture.

Designing a pre-regulator capable of sourcing enough current to meet the start-up demand of up to six UCC14240-Q1 bias regulators turning on simultaneously is paramount. Depending on the voltage range of the 12-V battery, a suitable pre-regulator topology could be a boost, SEPIC, flyback or pushpull DC-DC converter. The following recommendations should be taken into consideration:

  • Boost, SEPIC or flyback topologies are voltage sources interfacing to the UCC14240-Q1 input voltage. Depending on the total bias power and primary start-up current, it is important to assure enough output capacitance is present on the pre-regulator to assure reliable start-up.
  • When operating in continuous conduction mode (CCM) the boost, SEPIC and flyback topologies each have a right- half plane zero (RHPZ) as part of their control loop plant. The minimum RHPZ frequency will force a low crossover frequency to assure loop stability. The low crossover frequency will result in poor dynamic response during start-up which can cause the output voltage to undershoot below the UCC14240-Q1 minimum input. This can cause a chattering start-up or even a failed start-up due to insufficient UCC14240-Q1 input voltage, when there is not enough energy storage capacitance on the pre-regulator output. Alternatively, it helps to design these converter topologies to operate as current mode control (CMC) in discontinuous conduction mode (DCM). This will mitigate the effect of the RHPZ and allow higher crossover frequency, better loop stability and improved dynamic response during start-up.
  • If the duty cycle of the boost, SEPIC or flyback, operating in CCM, CMC is much higher than 50%, a large amount of slope compensation could be required to prevent subharmonic oscillation. During light-load start-up, the control will appear as voltage mode control (VMC) but the compensation will be for CMC. This problem is eliminated when operating in DCM, CMC, since no slope compensation is required.
  • The push-pull, pre-regulator is different compared to the boost, SEPIC or flyback. The push-pull is a buck derived topology that includes an output inductor making it appear as a current source to the UCC14240-Q1 input. The push-pull is well suited for low input voltage operation, such as 12-V and this topology does not have a RHPZ to contend with so the control loop crossover can be much higher comparatively.
  • Whichever topology is used, it is recommended to allow the pre-regulator output to reach full regulation before the UCC14240-Q1 (or multiple UCC14240-Q1) tries to start.