JPH0530749A - Power supply device - Google Patents

Abstract

PURPOSE:To provide a power supply device which controls voltage with precision always, even when the ripple component of a detected voltage becomes smaller than a readable limit because of load variation. CONSTITUTION:The title power supply device is one which converts a voltage signal V1 obtained in a voltage detecting element into a digital signal with an A/D converter 14, and controls voltage applied to its load on the basis of the digital signal. And the power device has an amplifying means 17 which amplifies the output voltage V of the voltage detecting element and conveys it to the A/D converter 14, a ripple deviation detecting means 18 which takes out a ripple component of the output voltage V1 of the voltage detecting element and compares it with a target voltage value, and a counter 19 which does counting operation on the basis of the output of the ripple deviation detecting means 18. And the amplification factor in the amplifying means 17 varies in accordance with the count output of the counter 19.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device which stably holds a voltage or current applied to a load.

[0002]

2. Description of the Related Art As an example of the above power supply device, one shown in FIG. 3 is known. This apparatus uses the X-ray tube 1 as a load, and applies a predetermined voltage between the filament 2 and the target 3 in the X-ray tube 1.

A current supply circuit 10 is connected to the filament 2, and a current is supplied from the current supply circuit 10 to the filament 2. As a result, the filament 2 generates heat, and thermoelectrons are emitted from the filament 2. The thermoelectrons collide with the target 3 and X-rays are emitted from the target 3. The applied voltage applied between the filament 2 and the target 3 accelerates the thermoelectrons emitted toward the target 3.

In this power supply device, the commercial power supply 4 to X
Switching elements, for example, two SCRs 5 are provided in parallel with each other in a power supply path reaching the wire tube 1. A step-up transformer 6, a rectifier circuit 7, a smoothing circuit 8 and a voltage detector 9 are provided in this order in the subsequent stage of the SCR 5. The voltage detection unit 9 is configured by connecting two voltage dividing resistors R1 and R2 in series, and its output V1 is guided to the voltage control device 11. The voltage control device 11 includes a voltage detector 9
ON / OFF of the SCR 5 is controlled based on the output V1 of. By this control, the voltage applied between the filament 2 and the target 3 is stabilized.

Conventionally, the voltage control device 11 is, for example, as shown in FIG.
Was configured as shown in. That is, the voltage detector 9
The detected voltage V1 detected by is added to the reference voltage V2 having a polarity opposite to that of the detected voltage V1, and the result is amplified by the two differential amplifier circuits 12 and 13, and then is sent to the CPU 15 via the A / D converter 14. Send in. CPU15
The phase angle of the SCR 5 is controlled so that the addition result of the detection voltage V1 and the reference voltage V2 becomes zero. In this way, the voltage applied to the X-ray tube 1 is maintained at a constant voltage corresponding to the reference voltage V2.

[0006]

Generally, the detection voltage V1
Contains ripple components due to fluctuations in the commercial power supply 4 (FIG. 3), fluctuations in the current flowing through the filament 2 (FIG. 3), and the like. The CPU 15 sets O of the SCR 5 so that the difference between the plus component and the minus component of the ripple component becomes zero, that is, the plus component and the minus component become equal.
Control N, OFF. However, the ripple component has a small signal level when the tube current (current flowing through the filament 2) is small, that is, when the load is low, and has a large signal level when the tube current is large, that is, when the load is high. On the other hand, since the amplification factors of the differential amplifier circuits 12 and 13 are always constant, the input voltage of the A / D converter is
It is small at low loads and large at high loads. As a result, the input voltage of the A / D converter becomes too small when the load is low, the reading of the ripple component becomes insufficient, and the control by the CPU 15 cannot be performed accurately.

The present invention has been made in view of the above problems in the conventional power supply device, and can always perform accurate control even when a load change such as a change in tube current occurs. An object is to provide a power supply device.

[0008]

In order to achieve the above object, the power supply device according to the present invention digitally converts the voltage signal (V1) obtained by the voltage detection unit (9) by an A / D converter (14). In a power supply device that converts the signal into a signal and controls the voltage applied to the load (1) based on the digital signal, the output voltage (V1) of the voltage detection unit (9) is amplified to A
Amplification means (17) for transmitting to the / D converter (14),
A ripple deviation detection means (18) for extracting a ripple component of the output voltage (V1) of the voltage detection section (9) and comparing it with a target voltage value, and a counting operation based on the output of the ripple deviation detection means (18). It has a counter (19) for performing, and is characterized in that the voltage amplification factor in the amplifying means (17) changes according to the count output of the counter (19).

[0009]

When the ripple component deviates from the target voltage value, the counter counts by the number corresponding to the deviation amount. The amplification means changes its voltage amplification factor according to the count value of the counter. Therefore, when the ripple component is smaller than the target voltage value, the voltage amplification factor of the amplifying means is increased, and the greatly amplified ripple component is sent to the A / D converter. As a result, even when the signal level of the ripple component becomes low when the load is low, the ripple component can be accurately read by the A / D converter.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the essential parts of an embodiment of a power supply device according to the present invention. This embodiment is also used as the internal circuit configuration of the voltage control device 11 of the power supply device shown in FIG. 1, as in the conventional example shown in FIG. The embodiment of FIG. 1 differs from the conventional example shown in FIG. 2 in that the latter-stage differential amplifier circuit 1 of FIG.
Instead of 3, the amplifier unit 16 surrounded by a chain line is provided.

The amplifier unit 16 includes an amplifying device 17 arranged in front of the A / D converter 14 and an amplifying device 17.
It has a ripple deviation detecting device 18 which uses the output of the above as an input signal, and a counter 19 which performs a counting operation based on the output of the ripple deviation detecting device 18.

The amplifying device 17 has a differential amplifying circuit 20 and a feedback resistor R3 of the differential amplifying circuit 20 which outputs D as an analog output.
And / A converter 21. b0 to b7 are D
Eight input ports provided in the / A converter 21.

The ripple deviation detecting device 18 has a coupling capacitor 22, an AC coupling circuit 23, a full-wave rectification circuit 24, a peak hold circuit 25, a window comparator 26, and a gate circuit 31. .

The window comparator 26 has an upper limit amplifier 29 and a lower limit amplifier 30. The window comparator is used in three different cases: the signal from the peak hold circuit 25 (peak hold signal) is lower than the lower limit, between the lower limit and the upper limit, and higher than the upper limit. Different signals are sent from 26 to the gate circuit 31.

The gate circuit 31 outputs an up signal to the counter 19 when the peak hold signal is lower than the lower limit, outputs a down signal to the counter 19 when the peak hold signal is higher than the upper limit, and between the two limits. In some cases, an oscillation prohibition signal for prohibiting oscillation of the oscillator 27 is output to the oscillator 27.

The counter 19 operates in accordance with the clock pulse from the oscillator 27 while the up signal or the down signal is being sent to the input port of the D / A converter 21.
The digital output signals of the bit ports b0 to b7 are incremented or decremented by 1, respectively.

The operation of the power supply device having the above structure will be described below. The detection voltage V1 of the voltage detection unit 9 in FIG. 3 is added to the reference voltage V2 (reverse polarity of the output voltage V1) in FIG. The detection voltage V1 contains a ripple component, and the result of addition appears as a signal in a form in which the ripple component is superimposed on the DC component.

The added signal has its phase inverted by the differential amplifier circuit 12, is amplified by the amplifier circuit 28 and the amplifier circuit 20, and is sent to the A / D converter 14. The signal appearing at the output of the amplifier circuit 20 is the ripple deviation detecting device 18
The ripple component is extracted by the coupling capacitor 22 and the AC coupling circuit 23, and full-wave rectified by the full-wave rectification circuit 24. After that, the peak voltage is taken out by the peak hold circuit 25, and the peak signal is sent to the window comparator 26.

When the tube current of the filament 2 (FIG. 3) is small, the level of the signal appearing at the output of the final stage amplifier circuit 20 of FIG. 1 becomes small. Considering the case where this signal level is lower than the lower limit of the window comparator 26,
An up signal appears at the output terminal of the gate circuit 31, and the counter 19 receiving the up signal starts counting,
The D / A converter 21 is incremented.

When the 8-bit input ports b0 to b7 of the DA converter 21 are incremented by 1, the value of the feedback resistor R3, which is an analog output, gradually increases correspondingly. As a result, the voltage amplification factor of the final stage amplifier circuit 20 becomes high, and the voltage signal appearing at the output of the amplifier circuit 20 is also amplified. This amplification processing is performed until the signal level falls within the optimum input voltage range of the A / D converter 14.
That is, the operation is continuously performed until the output of the peak hold circuit 25 falls between the upper limit and the lower limit of the comparator 26.

When the output signal level of the amplifier circuit 20 falls within the optimum input voltage range of the A / D converter 14, accurate digital conversion is performed by the A / D converter 14, and based on the digital output signal, the CPU 15 (see FIG. 2). ) Accurately controls SCR5.

When the output signal level of the final stage amplifier circuit 20 is higher than the allowable limit value, the down signal is output from the gate circuit 31 and the counter 19 causes the D / A converter 2 to operate.
Decrement 1. As a result, the final stage amplifier circuit 2
The output signal level of 0 is lowered and the level is A / D.
It can be lowered to the optimum input voltage range of the converter 14.

The output signal level of the final stage amplifier circuit 20 is
If it is already within the optimum input voltage range of the A / D converter 14, an oscillation stop signal is sent from the gate circuit 31 to the oscillation circuit 27, and the counting process by the counter 19 is stopped. As a result, the D / A converter 2
The value of the feedback resistor R3 in 1 is not changed, and the output signal level of the amplifier circuit 20 is maintained as it is.

As described above, the SCR 5 can always be accurately controlled even when the ripple component is lower than the allowable limit and the load is low, or when the ripple component is higher than the allowable limit.

[0025]

According to the present invention, when the ripple component deviates from the target voltage value due to load fluctuation or the like, the voltage amplification factor of the amplifying means (amplifying circuit 20) changes, and the output of the amplifying means, that is, A / The input voltage of the D converter (14) is compensated so as to fall within the optimum input voltage range of the A / D converter. Therefore, the detected voltage can always be read accurately even when there is a load change, and thus the applied voltage can always be controlled accurately.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a main part of an embodiment of a power supply device according to the present invention.

FIG. 2 is a circuit diagram showing a main part of an example of a conventional power supply device.

3 is a circuit diagram showing an example of the overall configuration of a power supply device in which the circuit of FIG. 1 is used.

[Explanation of symbols]

9 Voltage detector 14 A / D
Converter 17 Amplification device 18 Ripple deviation detection device 19 Counter 20 Differential amplification circuit 21 D / A converter 23 AC coupling circuit 24 Full-wave rectification circuit 25 Peak hold circuit 26 Window comparator V1 Detection voltage V2 Reference voltage

Claims (2)

[Claims] 1. The voltage signal obtained by the voltage detection unit is A / D
In a power supply device that converts a digital signal by a converter and controls a voltage applied to a load based on the digital signal, an amplifier that amplifies the output voltage of the voltage detection unit and transmits it to the A / D converter, and a voltage detection unit It has a ripple deviation detecting means for extracting a ripple component of the output voltage and comparing it with a target voltage value, and a counter for performing a counting operation based on the output of the ripple deviation detecting means. Is a power supply device characterized by changing according to the count output of the counter. 2. The amplifier means comprises an amplifier circuit formed by connecting an input resistor and a feedback resistor to an operational amplifier, and a D / A which uses the counter output as a digital input and the feedback resistor of the amplifier circuit as an analog output. The power supply device according to claim 1, comprising a converter.