JPH076709Y2 - Power supply - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a power supply device that detects a filter current and controls an output.

(Prior Art) In recent years, an increasing number of power supply devices are used to control the output of a device by detecting the amount of change in the phase and amplitude of the capacitor current of the output filter. For example, there is the invention of Japanese Patent Application No. 61-159412. In such a power supply device, conventionally, as shown in FIG. 2, the current flowing through the filter capacitor C ₁ is directly
It was detected by current transformer CT ₁ etc. In FIG. 2, 1, 1'denotes a power supply line, 2 a control circuit, and 3 an electronic circuit. In the case of such a current detection method, when the power supply device has a large capacity, the capacity of the capacitor C ₁ of the output filter also becomes large, so that the current of the capacitor C ₁ also becomes a large current and this current is directly detected. The current transformer CT ₁ has a drawback in that it has a large capacity and external dimensions.

(Problems to be solved by the invention) Generally, when the capacitor current detection signal is used as a control circuit signal, it is a minute voltage / current signal, so that the influence of noise generated when the switching element of the power supply device operates is affected. Easy to receive. This noise is generally easy to be thrown away in the wiring leading from the output end of the current detector (current transformer) of the capacitor to the electronic circuit of the control circuit.

In order to reduce the influence of noise, it is desirable to incorporate the current detector itself into an electronic circuit in the control circuit in order to shorten the wiring length of the current detector output. However, the conventional current detector has a problem that it cannot be arranged together with the electronic circuit because it is large in size.

In addition, since the current detector for generating the control signal, that is, the secondary side of the current transformer is generally a high impedance circuit,
The secondary side is easily affected by noise. On the contrary, the primary side of the current transformer is a low impedance circuit and is strong against noise.
Therefore, it is important to shorten the secondary wiring in order to increase the noise resistance. That is, when the current transformer is closer to the electronic circuit, the wiring on the secondary side becomes shorter, and it is possible to make it less susceptible to noise.

(Means for Solving Problems) The present invention has been proposed to solve the above-mentioned drawbacks, and provides a power supply device having a high-noise-resistant, small-capacity, small-sized and inexpensive current detector. With the goal.

In order to achieve the above object, the present invention provides a power supply device that uses a detection signal of a current flowing through a filter capacitor as a control signal of a control circuit, in parallel with the filter capacitor, a second capacitor having a smaller capacity than the filter capacitor. A gist of a device is a power supply device characterized in that a series circuit of a capacitor and a current transformer is connected and an output voltage from the current transformer is used as a control signal of the control circuit.

Next, an embodiment of the present invention will be described. Needless to say, the embodiment is merely an example, and various modifications and improvements can be made without departing from the spirit of the present invention.

FIG. 1 shows an embodiment of the present invention.

In the figure, 1,1 'is the power supply line, L ₁ is the inductance of the power supply line, C ₁ is the capacitor inserted between the power supply lines 1,1',
A filter is formed by the inductance L ₁ and the capacitor C ₁ . Reference numeral 2 is a control circuit in which a capacitor C ₂ and a current transformer CT ₂ are housed, and the capacitor C ₂ and the current transformer CT ₂ are connected in series and inserted in parallel with the capacitor C ₁ . The resistor R ₂ and the electronic circuit 3 are then connected in parallel to the current transformer CT ₂ .

The current i _c2 flowing through the capacitor C ₂ is Becomes Here, V _c2 represents the voltage across the capacitor C ₂ .
And n the winding ratio of the current transformer CT ₂ Here, the current transformer when the winding ratio of CT ₂ and n, current transformer CT ₂ of the secondary current is n minutes of first current i of i _{c2 cT2} flows.

Therefore, a voltage i _cT2-2 × R ₂ is generated across the resistor R ₂ , and this voltage is input to the electronic circuit 3 as a control signal, and the electronic circuit 3 controls the power supply device. Here, since the capacitor current detector is arranged in the control circuit 2 in the vicinity of the electronic circuit 3 (may be in the same printed circuit board), an electronic device that receives the capacitor current detection signal from the output end of the capacitor current detector, that is, the current transformer The wiring distance to the circuit 3 can be shortened sufficiently. Therefore, a stable control device that hardly picks up noise can be configured.

In the present invention, the capacitor for detecting the control current has a small capacity of about 1 μF, so that the capacitor and the current transformer for detecting the capacitor current can be mounted on the same printed circuit board as the electronic circuit. The secondary wiring of is also shortened,
It is resistant to noise.

For example, in the case of a 10 KVA output inverter, 1 μF is required for an AC filter capacitor of 1000 μF, and in the case of a 1 KW output converter, a DC filter capacitor may be 1 μF for 1000 μF, and a small one can be used. Further, the current transformer also has a small capacity and a small size corresponding to these capacitors.

(Effects of the Invention) As described above, the present invention is a power supply device that uses a detection signal of a current flowing through a filter capacitor as a control signal of a control circuit, and has a smaller capacity than the filter capacitor in parallel. By connecting the series circuit of the second capacitor and the current transformer and using the output voltage from the current transformer as the control signal of the control circuit, (a) a power supply device resistant to noise can be obtained.

(B) The current detector becomes smaller.

If the current detector is mounted on the printed circuit board, the same printed circuit board can be used for small to large capacity power supply devices.

(C) With the above, an economical low-cost power supply device can be obtained.

And so on.

[Brief description of drawings]

FIG. 1 shows an embodiment of the power supply device of the present invention, and FIG. 2 shows a conventional example. 1, 1 '... power supply line, 2 ... control circuit, 3 ... electronic circuit.

Claims (1)

[Scope of utility model registration request] 1. A power supply device using a detection signal of a current flowing through a filter capacitor as a control signal of a control circuit, wherein a second capacitor having a smaller capacity than the filter capacitor and a current transformer are provided in parallel with the filter capacitor. Power supply device characterized in that the output voltage from the current transformer is used as a control signal of the control circuit