High-voltage power unit and mass spectrometer using the power unit

摘要

An excessive overshoot preventing unit (16) is connected to a loop in which a command voltage Vf according to a difference between: a voltage obtained by dividing an output voltage Vout as a high voltage; and a control voltage V cont set from the outside is obtained and fed back to each of drive circuits (3 and 5) of a positive voltage generating unit (2) and a negative voltage generating unit (4). The excessive overshoot preventing unit (16) clamps the command voltage Vf at a voltage value according to the control voltage Vcont. An overshoot that occurs in the voltage generating unit (2 or 4) at the time of polarity switching mainly depends on a circuit constant, and hence the amount of overshoot is excessive in the case of a low-voltage output even if the amount of overshoot is optimal in the case of a rated output. To deal with this, in this power unit, the overshoot of the command voltage Vf in suppressed by the excessive overshoot preventing unit (16), and hence the output voltage can be promptly settled to a target voltage even in the case of a low-voltage output.

主权项

1. A high-voltage power unit for selectively outputting a high voltage having a positive or negative polarity, the high-voltage power unit comprising:
a positive voltage generating unit for generating a positive high voltage; a negative voltage generating unit for generating a negative high voltage; a first load unit connected between a pair of output terminals of the positive voltage generating unit; and a second load unit connected between a pair of output terminals of the negative voltage generating unit, wherein one of the pair of output terminals of the positive voltage generating unit is connected to one of the pair of output terminals of the negative voltage generating unit to connect the two voltage generating units in series, any of another of the pair of output terminals of the positive voltage generating unit and another of the pair of output terminals of the negative voltage generating unit is defined as a reference side, while a high-voltage output whose polarity is switched is taken out from the another terminal defined as the reference side, and the high-voltage power unit further comprises:
a) a controlling unit for controlling a voltage generated by each of the positive voltage generating unit and the negative voltage generating unit, through feedback control based on a detection voltage obtained by dividing the high-voltage output, the controlling unit sending a command voltage to each of the positive voltage generating unit and the negative voltage generating unit such that the output voltage of one of the two voltage generating units changes from a first predetermined voltage to zero while simultaneously the output voltage of another of the two voltage generating units changes from zero to subside on a second predetermined voltage after an overshoot, at a time of switching the polarity of the high-voltage output between positive and negative; andb) a voltage limiting unit for limiting a value of the command voltage to suppress the overshoot, the voltage limiting unit being provided between: the controlling unit; and the positive voltage generating unit and the negative voltage generating unit, whereinthe controlling unit includes an error amplifier for obtaining a difference between a control voltage and the detection voltage, the control voltage being set from an outside for setting a voltage value of a high-voltage output desired to be taken out, andthe voltage limiting unit clamps a voltage at an output of the error amplifier using a Zener diode connected to the output of the error amplifier.