JPH0638530A - DC power supply with feedforward control function - Google Patents

Abstract

(57) [Summary] [Purpose] A DC power supply using a phase control element such as an SCR.
The purpose is to significantly reduce output fluctuations due to rapid fluctuations in AC input. [Structure] A monitor circuit 7 for monitoring an AC input voltage, a variation detection circuit 8 having a differentiating mechanism, and an addition circuit 9 for adding the variation detection circuit output and a feedback signal are provided. To enter. [Effect] The conventional feedback-only control cannot follow a rapid AC input fluctuation, but the addition of the feedforward circuit having the above configuration can significantly reduce an output fluctuation with respect to a rapid AC input change.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phase control type DC power supply using an SCR, a triac or the like, and more particularly to a DC power supply with a feedforward function which is effective in the field of semiconductor manufacturing equipment and the like which requires highly stable output. .

[0002]

2. Description of the Related Art FIG. 7 shows a conventional example. In the figure, the output of the phase controller 1 is input to the rectifier circuit 3 and output via the output monitor circuit 4. The output of the output monitor circuit 4 is input to the feedback control circuit 5, which outputs a feedback signal for controlling the output constant, and this signal is input to the phase controller 1 to control the output constant. A transformer 2 is used between the phase control unit 1 and the rectifier circuit 3 as needed for the purpose of insulation or voltage change.

Another conventional example is shown in FIG. The output of the phase control unit 1 is input to the rectifier circuit 3, and is output via the output stabilization circuit 6 and the output monitor circuit 4. The output of the output monitor circuit 4 is input to the output stabilization circuit 6, which stabilizes a small fluctuation and outputs a feedback signal of a large fluctuation. This feedback signal is input to the phase controller 1 to control large fluctuations. In addition,
The phase control unit 1 includes a portion for driving a phase control element such as an SCR or a triac based on the feedback signal and a phase control element.

Incidentally, as a device related to this kind, for example, Japanese Patent Laid-Open No. 2-131368 and USP 4,
809,150 publication.

[0005]

In the above-mentioned conventional apparatus, the phase control is performed by feedback. This feedback system usually does not respond within tens to hundreds of milliseconds. Therefore, if the AC input changes abruptly within several cycles, the control cannot follow and the output changes. When the load has a constant voltage property or a constant current property and constant current control or constant voltage control is performed, this variation is particularly remarkable. Recently, power factor adjustment and voltage adjustment of an AC supply line have been performed for the purpose of energy saving, and there are cases in which a sudden change in AC input occurs. In order to respond to this sudden change in AC voltage with conventional equipment, it is necessary to provide the rectifier circuit with a filter with a time constant equal to or greater than the response of the feedback system. Therefore, it was not practical.

An object of the present invention is to drastically reduce the output fluctuation with respect to the rapid fluctuation of the AC input in the AC input type DC power supply using the phase control element such as SCR.

[0007]

To achieve the above object, in an AC input type DC power supply, a monitor circuit for monitoring an AC voltage, a fluctuation detection circuit for detecting fluctuations in the monitor output, and this fluctuation detection circuit. An adder circuit is added to add the output of the feedback circuit output to the output of the feedback circuit. The output of the adder circuit is input to the phase control unit to control the phase, and the feedforward phase control is performed with respect to the fluctuation of the AC input voltage. is there. Note that the output of the fluctuation detection circuit sets the pole of the signal so that the phase of the phase controller decreases when the AC input increases, and the phase of the phase controller increases when the AC input decreases. To do. By adding this feedforward control, the output can be stabilized even when the AC input voltage changes suddenly within several cycles or less. Further, the fluctuation detecting circuit is provided with a mechanism for differentiating the monitor output signal, so that only a rapid fluctuation of the AC input voltage is detected.

[0008]

When the AC input fluctuates, it is monitored by the monitor circuit, the fluctuation detection circuit detects the fluctuation amount, and the addition circuit adds it to the feedback signal. Is decreased and the AC input is decreased, the phase of the phase controller is increased.

By setting the time constant of the differentiating mechanism built into the fluctuation detecting circuit to be smaller than the response time constant of the conventional feedback system, the feedforward mechanism mainly works for rapid changes in the AC input, The feed-forward mechanism mainly works for slow changes in AC input. Therefore, a stable output can be obtained regardless of whether the AC input changes quickly or slowly.

When the output fluctuation with respect to the AC input fluctuation has non-linearity due to the polarity of the fluctuation of the AC input, the phase angle of the phase controller, etc., the fluctuation detection circuit and the addition circuit are subjected to non-linear operation. Thus, a device with high output stability can be obtained.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to FIGS.
1 and 2 are block diagrams corresponding to FIGS. 7 and 8 of the above-mentioned conventional example. In both cases, the output fluctuation is reduced in response to a sudden change in the AC input. A fluctuation detection circuit 8 that detects fluctuations in the output of the monitor circuit 7 and an adder circuit 9 that adds the output of the fluctuation detection circuit 8 to the feedback circuit output are provided. Is controlled, and the phase control is performed by feedforward with respect to the fluctuation of the AC input voltage. It should be noted that the output of the fluctuation detection circuit 8 has a signal polarity such that the phase of the phase control unit 1 decreases when the AC input increases and the phase of the phase control unit 1 increases when the AC input decreases. Set the number. By adding this feedforward control, the output can be stabilized even when the AC input voltage changes suddenly for several cycles or less. Further, by providing the variation detection circuit 8 with a mechanism for differentiating the monitor output signal, it is possible to detect only the fast variation of the AC input voltage.

Further, different embodiments will be described in detail.

The first embodiment is shown in FIGS. Transformer 7
After performing insulation voltage conversion by -1, double-wave rectification is performed by the diode bridge 7-2, and two sets of sample hold circuits 7
-3 and 7-4. Then, the timing generator 7-5 outputs sampling signals 7-S2 and 7 for alternately sampling every half cycle of the AC input.
-S3 is generated to generate two sets of sample hold circuits 7-3.
And 7-4. Sample and hold circuit 7-3
And 7-4, the peak of the voltage is alternately sampled and held every half cycle, and the signal is alternately output by the analog switch 7-6 that switches every half cycle. A minute noise for a short period of time when the analog switch 7-6 is switched is removed by the filter including the resistor R1 and the capacitor C1. Next, the differential amplifier 8-1 and the capacitor C
2. Only the fluctuation of the AC input is output by the differentiating circuit constituted by the resistor R2. The output of the fluctuation detection circuit 8 is input to the adder 9, added with the feedback signal FB, and then input to the phase control unit 1. The adder 9 includes a differential amplifier 9-1 and a plurality of resistors. Resistance R
2. The time constant of the differentiating mechanism in the fluctuation detecting circuit 8 determined by the capacitor C2 is set shorter than the time constant of the feedback system, and the fluctuation detecting circuit output is generated only for the rapid change of the AC input fluctuation. I will let you.

FIG. 5 shows a second embodiment. When the time constant of the feedback system differs depending on the polarity of the AC input fluctuation, the differential detection circuit 8 has a differential mechanism of the differential amplifier 8-3, the capacitor C4, and the resistor R4 that works against a positive voltage fluctuation, and a negative mechanism. A more stable output can be obtained by providing a differentiating mechanism having two different time constants, that is, the differential amplifier 8-2 that works against the voltage fluctuation of 1, the differentiating mechanism of the capacitor C3, and the resistor R3.

FIG. 6 shows a third embodiment. If it is better to non-linearly determine the output of the fluctuation detection circuit 8 according to the polarity and magnitude of the AC input fluctuation and the value of the feedback signal FB due to the reason that the load has non-linearity, the differential amplifier 8− The output of the fluctuation detection circuit 8 including the capacitor 1, the capacitor C2 and the resistor R2 is converted into a digital value by the analog-digital converter 9-1, and the feedback signal FB is used.
Is also converted into a digital amount by the analog-to-digital converter 9-2, and these two digital amounts are input to the read-only memory 9-3 to perform non-linear operation, and the read-only memory 9-
The output of 3 is converted into an analog amount by the digital-analog converter 9-4, and then input to the phase control unit 1. Although FIG. 6 describes the case where the calculation is performed digitally, the same function can be performed by analog calculation by using an analog multiplier, an analog adder, a non-linear amplifier, or the like.

[0016]

According to the present invention, the fluctuation of the AC input is detected, added to the feedback signal and input to the phase control circuit, and the time constant of the differentiation mechanism incorporated in the fluctuation detection circuit is fed back to the conventional feedback. By setting it shorter than the time constant of the response of the system, there is an effect that the output fluctuation with respect to the rapid change of the AC input can be greatly reduced without impairing the stability of the output with respect to the conventional slow change.

[Brief description of drawings]

FIG. 1 is a block diagram showing an example of a phase control type DC power supply of the present invention.

FIG. 2 is a block diagram showing another example of the phase control type DC power supply of the present invention.

FIG. 3 is a block diagram of a first embodiment of the present invention.

FIG. 4 is an explanatory diagram showing an adder circuit according to a first embodiment of the present invention.

FIG. 5 is an explanatory diagram showing a second embodiment of the present invention.

FIG. 6 is an explanatory diagram showing a third embodiment of the present invention.

FIG. 7 is a block diagram of a conventional phase control type DC power supply.

FIG. 8 is another block diagram of a conventional phase control type DC power supply.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Phase control part, 2 ... Transformer, 3 ... Rectifier circuit, 4 ... Output monitor circuit, 5 ... Feedback control circuit, 6 ... Output stabilization circuit, 7 ... Monitor circuit, 8 ... Fluctuation detection circuit, 9 ... Addition circuit .

Claims (2)

[Claims] 1. An AC input type DC power supply having a phase control element and a phase control section having the drive circuit, a rectifier circuit, an output monitor circuit, and a feedback circuit for adding a signal to the phase control section based on the output and the set value. A monitor circuit that monitors the input voltage, a fluctuation detection circuit that detects fluctuations in the output of this monitor circuit, and an addition circuit that adds the output of this fluctuation detection circuit and the output of the feedback circuit are provided. DC power supply with feedforward control function, which is applied to the control unit. 2. A phase control unit having a phase control element and this drive circuit, a rectifier circuit, an output monitor circuit, an output stabilizer circuit for making the output constant by the output monitor circuit output and a set value, and the output stabilizer circuit. In an AC input multi-stage control DC power supply having a feedback circuit that applies a signal to a phase control unit based on an output value, a monitor circuit that monitors an AC input voltage, a fluctuation detection circuit that detects fluctuations in the output of the monitor circuit, and A DC power supply with a feedforward control function, comprising an adder circuit for adding the output of the fluctuation detection circuit to the output of the feedback circuit, and applying the output of the adder circuit to a phase controller.