SNVA991 October   2022 LM5123-Q1

 

  1.   How to Design a Boost Converter Using LM5123
  2.   Trademarks
  3. 1Design Example
  4. 2Calculations and Component Selection
    1. 2.1  Switching Frequency
    2. 2.2  Initial Inductor Calculation
    3. 2.3  Current Sense Resistor Selection
    4. 2.4  Inductor Selection
    5. 2.5  Output Capacitor Selection
    6. 2.6  Input Capacitor Selection
    7. 2.7  Feedback Resistor Selection
    8. 2.8  UVLO Resistor Selection
    9. 2.9  Soft-Start Capacitor Selection
    10. 2.10 Control Loop Compensation
      1. 2.10.1 Crossover Frequency (fcross) Selection
      2. 2.10.2 RCOMP Selection
      3. 2.10.3 CCOMP Selection
      4. 2.10.4 CHF Selection
    11. 2.11 MOSFET selection
  5. 3Implementation Results
  6. 4Small Signal Frequency Modeling
    1. 4.1 Boost Regulator Modulator Modeling
    2. 4.2 Compensation Modeling
    3. 4.3 Open Loop Modeling
  7. 5Resources

1 Design Example

Figure 1-1 Typical Application

This design example produces a variable load voltage boost. Applications such as Class H audio amplifiers, and LED drivers require a variable output voltage from a boost regulator to greatly improve the system efficiency. The load voltage range for this design is 24 V to 33 V and provides a maximum power of 200 W from a standard 12 V automotive battery. The output voltage is adjusted using the TRK pin of the device. The detailed parameters are presented in Table 1-1 and the component selection is discussed in Section 2.

Table 1-1 Design Parameters
PARAMETER Test Conditions MIN TYP MAX UNIT
INPUT VOLTAGE CHARACTERISITCS
Input Voltage Range Operation 8 14 18 V
Input UVLO levels Turn-off 5.2 V
Turn-on 6.2 V
OUTPUT CHARACTERISITCS
Load Voltage VTRK = 400 mV (VLOADmin) 24 V
VTRK = 583 mV (VLOADmax) 35 V
POUTmax VSUPPLY= 8 V to 18 V 200 W W
SYSTEM CHARACTERISITCS
fSW 440 kHz