Microelectromechanical system (MEMS) devices often require high DC-bias voltages (40V to 100V) at low current (< 1mA), but the available supply voltage may be < 12V. A DC-DC converter that combines inductive and capacitive step-up circuitry (
Figure 1) achieves the high voltage without need for a costly transformer.
Figure 1. A high-voltage DC-DC converter (U1) converts a typical 5V input to 36V, and a 2-stage charge pump boosts that voltage to more than 100V.
U1 is a step-up DC-DC converter capable of output voltages to +36V, and a 2-stage charge-pump converter (D2-D5 and C1-C4) nearly triples the U1 output. The R1/R2 divider provides feedback for regulating the circuit's output voltage. Use these equations to calculate the resistor values:

For lower output voltages (< 70V), remove D4, D5, C3, and C4 to produce a single-stage charge pump. Similarly, you can add another stage to produce voltages higher than 100V. An optional post filter (R3 and C5) reduces the output ripple to < 10mV
P-P.
Figure 2 illustrates the variation of output voltage with output current.
Figure 2. The output voltage in Figure 1 is well regulated for load currents up to 0.7mA.
A similar version of this article appeared in the August 18, 2002 issue of
EET magazine.
© , Maxim Integrated Products, Inc.
|
このウェブサイトのコンテンツは米国および各国の著作権法によって保護されています。コンテンツの複製を希望される場合は
お問い合わせください。.
APP 1751:
アプリケーションノート
1751,
AN1751,
AN 1751,
APP1751,
Appnote1751,
Appnote 1751
|
maxim_web:en/products/power,maxim_web:en/products/power/switching-regulators/step-up-switching-reg,maxim_web:en/products/power/charge-pumps
maxim_web:en/products/power,maxim_web:en/products/power/switching-regulators/step-up-switching-reg,maxim_web:en/products/power/charge-pumps