JPH04161072A - Low ripple power supply - Google Patents

Abstract

PURPOSE:To reduce the capacity of a high speed power supply by providing a low-pass filter for a current reference in a high speed power supply which can control the current thereby preventing an excessively high current from being fed to the side of a smoothing filter. CONSTITUTION:A low ripple power supply mainly comprises an AC bus 1, a transformer 2 for rectifier, a control rectifier 3, a DC reactor 4, a capacitor 5, an active filter 6, a constant current control circuit 11B in a high speed power supply unit 16, and the like. Cut-off frequency of a low-pass filter 17 is set lower than six times of the basic frequency of power supply f0 and ripple components, which are not required to be compensated for a current reference 54 in the high speed power supply unit 16, are eliminated. Ripple voltages having frequency higher than six times of the basic frequency f0 of power supply are sufficiently damped through a smoothing filter comprising the reactor 4 and the capacitor 5. Since high frequency ripple current does not flow through the capacitor 5 in the smoothing filter, the high speed power supply is prevented from increasing in capacity.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a low ripple power supply required in an accelerator coil power supply, a superconducting coil power supply 1 strong magnetic field coil power supply, and the like.

(Prior Art) In recent years, highly stable and low ripple power sources have been required as power sources for various physical experiments such as accelerators and coils for generating strong magnetic fields. These power supplies are generally required to have IXIG-' stability and ripple content. As a power source that satisfies these demands.

When the output voltage range is several tens of volts or less, a power source is used in which a ripple current control transistor is connected to the DC output side of the controlled rectifier. Such a power supply is called a transistor dropper type, and has very excellent characteristics in a low voltage and small capacity range. However, when the voltage exceeds 100V and the capacity exceeds several hundred kW, it becomes extremely uneconomical and impractical due to the capacity of the transistor.Therefore, a large-capacity, low-ripple power supply device is used, as shown in Figure 4. An active filter type low ripple power supply is used. The fourth WI is a block diagram of an active filter type low ripple power supply device. In Figure 4), 1 is the AC bus, and 2 is the rectifier transformer.

3 is a controlled rectifier that converts AC voltage into DC voltage.

4 is a DC reactor of a smoothing filter that mainly removes harmonic ripples, 5 is a capacitor that is also a smoothing filter, 6 is an active filter that removes ripples from the power supply fundamental frequency to high frequencies, 7 is a load, and 8 is a controlled rectifier 3 Potential transformer for detecting the firing angle reference, which controls the
15 is an auxiliary transformer that converts the output of the instrument transformer 8 into an electronic level voltage, 9 is a DC voltage detector that detects the output voltage of the control rectifier 3, and 11 is a DC reference signal 51 and a DC current detector 10. 12 is a constant current control circuit that inputs the difference between the detected DC current 5Z and controls the current to be constant; 12 is a minor loop that inputs the difference between the output of the constant current control circuit 11 and the output of the DC voltage detector 9; A constant voltage control circuit that controls the voltage at high speed, 13 is the output of the constant voltage control circuit 14 and the auxiliary transformer 1
A phase control circuit 9 determines the ignition phase and ignition timing from the output of 5, and 14 is a pulse amplifier.

In FIG. 4, if the controlled rectifier 3 is a three-phase full-wave rectifier circuit, the DC output side of the controlled rectifier has the highest high-frequency ripple voltage of a frequency (6fe) component six times the power supply fundamental frequency f. Others include ripple voltage at the same frequency as the power supply fundamental frequency full due to variations in the firing angle of the controlled rectifier, and ripple voltage at a frequency twice the power supply fundamental frequency (2f+) due to unbalance of the three correlations of AC voltage. Ripple voltage, etc. occurs.

Of these ripple voltages, six times the high frequency ripple voltage is attenuated by a smoothing filter composed of a DC reactor 4 and a capacitor 5, and the rest, including the ripple voltage of the fundamental wave, is attenuated by an active filter 6.

When trying to extend the ripple compensation of the active filter to the lower frequency side, the voltage-time product (Δ
V-t) increases, which causes problems such as the external dimensions of the reactor transformer becoming too large, making it impractical in terms of performance and economy.For this reason, conventional active filters mainly reduce the power supply fundamental frequency. It was designed to attenuate ripples in the twice the frequency range.

In other words, in a low ripple power supply using an active filter method, if the fluctuating frequency component is higher than the power supply fundamental frequency, it can be compensated by the active filter within the normal fluctuation value.
Furthermore, although the constant current control circuit 10 and the constant voltage control circuit 11 were able to compensate for very slow fluctuations in the voltage value, the ripple voltage cannot be sufficiently compensated for against voltage fluctuations in the range from about IHz to the power supply fundamental frequency. There was a problem that it could not be attenuated.

FIG. 3 shows a circuit for solving the above problem. In FIG. 3, the same elements as in FIG. 4 are designated by the same reference numerals, and their explanations will be omitted.

In FIG. 3, 16 is a high-speed power supply that performs current control at high speed to compensate for ripples and fluctuations, 54 is a current reference for the high-speed power supply 16, and 55 is a DC current detector 1.
Output current of high-speed power supply 16 detected at 0B, IIB
is a constant current control circuit of the high-speed power supply device 16. In FIG. 3, a constant current control circuit 11A that inputs the difference between a current value 52 detected by DC current detection @IOA and a DC current reference value 51 to control the current to a constant value, and a constant current control circuit 11
The constant voltage control circuit 12 inputs the difference between the output of A and the DC voltage value 53 detected by the DC voltage detection @ 9 and controls the voltage in a minor loop, compensating for slow fluctuations in AC voltage, etc. . A smoothing filter consisting of a capacitor S and a reactor 4 removes ripple voltage having a frequency equal to or higher than six times the power supply fundamental frequency f0 (6f). In FIG. 3, if a signal 54 representing the difference between a current reference 51 and an output current 52 of the controlled rectifier is supplied by a high-speed power supply device provided in parallel, a current equal to the reference will flow through the load.

(Problems to be Solved by the Invention) However, in the circuit shown in FIG. 3, the impedance seen from the high-speed power supply device 16 is such that the load and the capacitor of the smoothing filter are in parallel. Therefore.

Even if the high-speed power supply device 16 tries to correct the ripple current of the load, it will also flow to the capacitor of the smoothing filter.
For example, when the load constant is 1 H-10 Ω and the filter capacitor is 5-F, the impedance at each frequency is calculated as shown in Table 1.

Table 1 (unit: Ω) As can be seen from Table 1, the higher the frequency, the smaller the impedance of the filter, and even if the high-speed power supply 16 tries to correct the load current ripple, almost no current flows to the load. It will flow into the filter capacitor.

Therefore, the high speed power supply 16 not only carries current to the load;
It must have the capacity for the current to the filter.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and provide a low-ripple power supply device that can obtain similar effects without unnecessarily increasing the current capacity of the high-speed power supply device.

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the above-mentioned objects, the present invention provides a transformer that transforms grid voltage into a desired AC voltage, a controlled rectifier that converts the output AC of this transformer into DC, and a controlled rectifier that converts the output AC of this transformer into DC. A smoothing filter that smoothes the DC output of a controlled rectifier, a load to which the DC voltage obtained through the smoothing filter is applied, and a high-speed power supply device that is provided separately from the controlled rectifier and can control the current flowing to the load at high speed. A low ripple power supply device comprising: a low-ripple power supply device characterized in that a low-pass filter is provided as a current reference of a current control circuit that controls the high-speed power supply device.

(Function) As mentioned above, by providing a low-pass filter in the current reference of the current control circuit that controls the high-speed power supply,
The ripple frequency compensated by the high-speed power supply is limited, and the high-frequency ripple current does not flow to the capacitor of the smoothing filter, thereby preventing an increase in the capacitance of the high-speed power supply.

(Embodiment) FIG. 1 shows a block diagram of an embodiment of the present invention. In FIG. 1, the same parts as in FIG. 3 are given the same reference numerals, and the explanation thereof will be omitted. In FIG. 1, reference numeral 17 provided at the current reference of the current control circuit 11B that controls the high-speed power supply device 16 is a low-pass filter that attenuates inputs above a certain frequency.

Ripple voltage at a frequency higher than six times the power supply fundamental frequency f (6f, ) is caused by reactor 4. capacitor 5
Since it is sufficiently attenuated by the smoothing filter made up of

Therefore, a low-pass filter 17 is provided in the current reference 54 of the high-speed power supply 16 to remove ripples that do not need to be compensated. The cutoff frequency of the low-pass filter 17 is set lower than a frequency (6f,) that is six times the power source fundamental frequency f0.

FIG. 2 is a block diagram showing another embodiment of the present invention.

FIG. 2 shows a circuit in which an active filter using a reactor transformer is added to the circuit of FIG. 1. In Fig. 2, the high frequency ripple voltage of the frequency (6f,) component which is six times the power supply fundamental frequency f0 is attenuated by a smoothing filter consisting of the DC reactor 4 and the capacitor 5, and the ripple voltage of the 6f, component from the fundamental wave is The voltage is attenuated by an active filter 6. A constant current control circuit 10 and a constant voltage control circuit 11 compensate for very slow voltage fluctuations. Then, the high-speed power supply device 16 compensates for voltage fluctuations in a band from about IHz to the power source fundamental frequency.

The low-pass filter 17 has a cutoff frequency around the power supply fundamental frequency, and the high-speed power supply 16 compensates only for voltage fluctuations in the band from approximately IHz to the power supply fundamental frequency 1, and reduces the capacity.

〔Effect of the invention〕

As explained above, the present invention prevents the high-speed power supply from flowing unnecessarily more current to the smoothing filter than to the load by providing a reduced pass filter in the current reference of the high-speed power supply that can control the current at high speed. This can be prevented and the capacity of the high-speed power supply device can be reduced.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention, FIG. 2 is a block diagram showing another embodiment of the present invention, and FIG. 3 is a block diagram showing another embodiment of the present invention. FIG. 4 is a configuration diagram of different conventional low ripple power supply devices. 1... AC bus, 2... Rectifier transformer, 3...
・・Control rectifier, 4・DC reactor, 5・
...Smoothing filter capacitor, 6...Active filter, 7...Load, 8
...Instrument transformer, 9...DC voltage detector, 1
0A, IOB...DC current detector, 11A, IIB・
・・Constant current control circuit. 12... Constant voltage control circuit, 13... Phase control circuit, 14... Pulse amplifier, 15... Auxiliary transformer, 16... High speed power supply device, 17... Reduced pass filter. 51... Current reference 552... Controlled rectifier output current, 53... Controlled rectifier output voltage, 54... Auxiliary current reference, 55... High speed power supply device output current. Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] A transformer that transforms the grid voltage into a desired AC voltage, a controlled rectifier that converts the output AC of this transformer into DC, a smoothing filter that smoothes the DC output of this controlled rectifier, and the AC voltage obtained through this smoothing filter. In a low ripple power supply device comprising a load to which a DC voltage is applied and a high-speed power supply device that is provided separately from the control rectifier and can control the current flowing to the load at high speed, the current of a current control circuit that controls the high-speed power supply device. A low ripple power supply device characterized by providing a low-pass filter as a reference.