High Voltage Converter: 90 V from 1.5 V Schematic Circuit Diagram
The circuit shows one way of obtaining a voltage of 90 V from a 1.5 V battery supply. The LT1073 switching regulator from Linear Technology (www.linear-tech.com) operates in boost mode and can work with an input voltage as low as 1.0 V. The switching transistor, which is hidden behind connections SW1 and SW2, briefly takes one end of choke L1 to the ground. A magnetic field builds up in the choke, which collapses when the transistor stops conducting: this produces a current in diode D1 which charges C3. The diode cascade comprising D1, D2, D3, C2, C3, and C4 multiplies the output voltage of the regulator by four, the pumping of C2 causing the voltage developed across C4 via C3, D2, and D3 to rise. Finally, the regulator control loop is closed via the potential divider (10 MΩ and 24 kΩ).
These resistors should be 1 % tolerance metal film types. With the given component values, fast diodes with a reverse voltage of 200 V (for example type MUR120 from On Semiconductor www.onsemi.com) and a choke such as the Coilcraft DO1608C-154 (www.coilcraft.com) an output voltage of 90 V will be obtained. The output of the circuit can deliver a few milliamps of current.
The LT1073 is a versatile micropower DC/DC converter. The device requires only three external components to deliver a fixed output of 5V or 12V. The very low minimum supply voltage of 1V allows the use of the LT1073 in applications where the primary power source is a single cell. An on-chip auxiliary gain block can function as a low-battery detector or linear post-regulator.
Features
- No Design Required
- Operates at Supply Voltages From 1.0V to 30V
- Consumes Only 95µA Supply Current
- Works in Step-Up or Step-Down Mode
- Only Three External Off-the-Shelf Components Required
- Low-Battery Detector Comparator On-Chip
- User-Adjustable Current Limit
- Internal 1A Power Switch
- Fixed or Adjustable Output Voltage Versions
- Space-Saving 8-Pin MiniDIP or SO8 Package
