SLVAFE7 September   2022 LM51551

 

  1.   Abstract
  2.   Trademarks
  3. 1Introduction
    1. 1.1 Design Specification and Key Challenges
  4. 2High-Voltage Power Supply Design Using SEPIC
    1. 2.1 TI HV Supply Architecture Using SEPIC Topology
    2. 2.2 Switching Frequency Shift
    3. 2.3 Voltage Control by External Signal
  5. 3Test Result
    1. 3.1 Efficiency and Power Consumption (100 kHz vs 250 kHz)
    2. 3.2 Linearity of Output Voltages vs VBIAS
    3. 3.3 Output Ripple Measurement
    4. 3.4 Load Transient Test
    5. 3.5 Overload Protection
    6. 3.6 Thermal Image
  6. 4Summary
  7. 5References

1.1 Design Specification and Key Challenges

Table 1-1 summarizes the design specifications of a high-voltage power supply for an ultrasound smart probe.

Table 1-1 Design Specification of High-Voltage Power Supply
Characteristic Specification
Input voltage 12 V
Output voltage Bipolar (from 15 V to 75 V at 10 mA and –15 V to –75 V at –10 mA), total maximum output power 1.5 W
Peak efficiency 88%
Switching frequency 250 kHz
Size (length × width) 15 mm × 45 mm (single layer)
Height < 5 mm
Output voltage regulation 2%
Voltage symmetry with equal load on both rails 1%
Output ripple 0.1% of the output voltage
Synchronization to external clock frequency No
Adjustable output voltage Yes

An ultrasound smart probe has strict requirements on the size, power consumption, and thermal performance to make the device convenient to use. The key design challenges are as follows:

  • Bipolar output rail (from 15 V to 75 V at 10 mA and –15 V to –75 V at –10 mA), with deviation of the output rail with ±2%
  • Programmable switching frequency from 250 kHz at normal operation to 100 kHz at standby mode
  • Adjustable output voltage linearly controlled by external voltage signal