JPH054589U - Power filter circuit - Google Patents

Abstract

(57) [Abstract] [Objective] The present invention relates to a power supply filter circuit, so that a small choke coil can be operated for an electronic circuit composed of a load that operates with a small current and a load that occasionally operates with a large current. An object is to provide an improved power supply filter circuit. [Configuration] In a power supply filter circuit in which a choke coil is connected in series and a capacitance is connected in parallel to an electronic circuit composed of a load that operates with a small current and a load that occasionally operates with a large current, the choke Connect a diode in parallel with the coil.

Description

[Detailed description of the device] [Industrial applications]

 The present invention relates to a power supply filter circuit for an electronic circuit composed of a load operating with a small current and a load sometimes operating with a large current.

[Prior Art]

 In general, an electronic device is separated from a power supply circuit that converts alternating current to direct current and the panels that configure each electronic circuit, and power is supplied by connecting with a power supply line between these. For this reason, noise is superimposed on the power supply line, and each electronic circuit incorporates a filter for eliminating noise. As shown in FIG. 2, the electronic circuit incorporated in the panel sometimes consists of a small current load 4 that operates with a small current and a large current load 5 that operates with a large current by occasionally turning on and off the current with a transistor 6. It may be configured. Even for a load configured in this way, conventionally, a power supply filter has been configured by a capacity 3 connected in parallel to the load and a choke coil 2 connected in series.

[Problems to be solved by the device]

 As mentioned above, the power supply filters for electronic circuits, which are composed of a load that operates with a small current and a load that occasionally operates with a large current, are designed with capacitors and choke coils in consideration of when a large current flows. .. Therefore, considering the operation when a large current flows, it is necessary to increase the diameter of the core of the choke coil and the coil, which causes a problem that the size of the filter becomes very large. It is an object of the present invention to provide a power supply filter circuit improved to operate with a small choke coil for an electronic circuit composed of a load that operates with a small current and a load that occasionally operates with a large current. To do.

[Means for Solving the Problems]

 Means adopted by the present invention to solve the above problems will be described. For an electronic circuit consisting of a load that operates with a small current and a load that occasionally operates with a large current, a choke coil is connected in series, and in parallel with the choke coil in a current filter circuit in which a capacitance is connected in parallel. Connect a diode to.

[Action]

 When the electronic circuit operates only with a load that operates with a small current, the current is small, so the voltage drop due to the DC resistance of the choke coil is less than the contact potential difference of the diode connected in parallel with the choke coil. , No current flows through the diode. When a load that operates with a large current of an electronic circuit is added, the current flowing through the choke coil becomes large and the voltage drop due to the choke coil becomes large. However, the diodes connected in parallel flow a current to the load, causing the voltage drop due to the choke coil to the contact potential difference of the diode, so that the supply voltage to the electronic circuit can be made almost constant. As described above, by connecting the diode in parallel with the choke coil connected in series with the electronic circuit, when a load operating with a large current of the electronic circuit operates, current flows through the diode, The voltage drop due to the choke coil can be suppressed below the contact potential difference of the diode, and the power supply filter can be made compact.

【Example】

 An embodiment of the present invention will be described with reference to FIG. In FIG. 1, the choke coil 2, the capacitor 3, the small current load 4, the large current load 5, and the transistor 6 are as described in FIG. Reference numeral 1 is a diode, which is connected in parallel with the choke coil 2 in the same direction as the current supplied to the load. Now, when the transistor 6 is off and only the small current load 4 is operating, the current flowing through the choke coil 2 is small, so the voltage drop caused by the resistance of the coil of the choke coil 2 is small, The contact potential difference of the diode 1 connected in parallel becomes less than that, and the choke coil 2 and the capacitor 3 form a filter to remove noise. When the transistor 6 is turned on, a current flows through the large-current load 5, so that a large current also flows through the choke coil 2 to increase the voltage drop. However, when the voltage drop exceeds the contact potential difference of the diode 1 connected in parallel, a current flows through the diode 1 to supply a current to the load, causing the voltage drop due to the choke coil 2 to reach the contact potential difference of the diode 1. It supplies the load with electric power of almost constant voltage.

[Effect of the device]

 As described above, according to the present invention, the following effects can be obtained. By connecting a diode in parallel with a choke coil connected in series with an electronic circuit, when a load that operates with a large current of the electronic circuit operates, a current flows through the diode and the voltage drop due to the choke coil occurs. Can be kept below the contact potential difference of the diode, and the power supply filter can be made compact.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is a configuration diagram of a conventional example.

[Explanation of symbols]

 1 diode 2 choke coil 3 capacity 4 small current load 5 large current load 6 transistor

Claims (1)

[Claims for utility model registration] [Claim 1] A choke coil is connected in series and a capacitance is connected in parallel to an electronic circuit composed of a load that operates with a small current and a load that occasionally operates with a large current. A power supply filter circuit in which a diode is connected in parallel with the choke coil in the connected power supply filter circuit.