JP2007082309A - Switching power supply circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a switching power supply circuit suppressed in spurious characteristics by partially changing an arrangement. <P>SOLUTION: The switching power supply circuit comprises a battery terminal connected with a battery as a power supply, and receives an output from the battery via a filter F1 having a capacitor C1 and a coil L1. The capacitor C1, the coil L1 and the remaining switching power supply circuit PWa are separated from one another in terms of a position, the capacitor C1 and the coil L1 are arranged so as to be close to the position of the battery terminal, the battery positive terminal, the battery negative terminal and the capacitor C1 are electrically connected to one another, one end of the coil L1 is electrically connected to the battery positive terminal, the battery positive terminal and the remaining part of the filter F1 are electrically connected to each other via the coil L1 and a wiring line A electrically connected to the other terminal of the coil L1, and the ground at the switching power supply circuit PWa is electrically connected to the battery negative terminal by a wiring line B disposed in parallel with the wiring line A. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a switching power supply circuit that is used in an electronic device including a VCO and a PLL circuit and suppresses occurrence of spurious.

Power is supplied to a main power supply circuit that supplies power to a main first load circuit that is susceptible to interference, such as a tuner, and a second load circuit that is less susceptible to interference, such as a computer used to control the first load circuit. A switching power supply circuit, and controlling the switching power supply circuit while the operation of the first load circuit is stopped, controlling the main power supply circuit to the operating state, and supplying power to the second load circuit from the main power supply circuit. When the operation of the first load circuit is stopped, the main power supply circuit is controlled to be in the operation stop state, and the switching power supply circuit is set in the operation state to supply power from the switching power supply circuit to the second load circuit. By controlling the power supply control circuit, the switching power supply circuit is not operated during the operation of the first load circuit, and noise generation from the switching power supply circuit is prevented. Are (for example, see Patent Document 1).
JP 2000-287385 A

  However, when the above power supply circuit is used, two types of power supplies, that is, a main power supply circuit and a switching power supply circuit are required, and there is a problem that the apparatus becomes large due to these two types of power supply circuits. However, it is not suitable for use in a wireless communication device.

  On the other hand, a switching power supply circuit PW such as DC / DC, as shown in FIG. 3, for example, connects a filter F1 including a coil L1 and capacitors C1 and C2 to an input line from a battery terminal, and outputs the output from the filter F1 to DC / DC. Switching is performed by a switching transistor Q1 that is on / off controlled by a DC control integrated circuit IC1, and a switching output is output via a smoothing circuit S1 including a diode D1, a coil L2, and a capacitor C3.

  In the switching power supply circuit PW shown in FIG. 3, a filter F1 is provided so that the switching noise does not affect the input line.

  However, in the case of an electronic device equipped with a PLL frequency synthesizer using a VCO or PLL circuit, for example, a wireless communication device, as shown in FIG. 4A, a reception block 1 and a transmission block 2 constituting the wireless communication device. , DSP (digital signal processor) 3, VCTCXO (temperature compensation crystal oscillator), PLL circuit, multiplier, loop filter, and a wireless communication apparatus including a PLL frequency synthesizer 4, a switching power supply circuit PW is a plane Specifically, they are arranged as shown in FIG. In FIG. 4A, the halftone dot portion indicates the ground, and reference numeral 5 indicates the antenna.

  Further, the planar arrangement in the switching power supply circuit PW is as shown in FIG. 4B, and a capacitor C1 constituting a part of the filter F1 by the wiring passing between the receiving block 1 and the PLL frequency synthesizer 4 In general, the coil L1 is electrically connected to the battery + terminal and the coil L1 is disposed near the VCO and PLL circuit. In this case, the load fluctuation of the switching power supply circuit PW appears as a spurious of the VCO output. .

  In the case of a high frequency such as the switching frequency of the switching power supply circuit PW, noise countermeasures can be taken by applying a magnetic shield to the switching power supply circuit PW. However, if the load fluctuation period is several tens of kHz or less, the thickness of the shield should be Even if the number of shields is increased or the shield material is changed to one having a high shielding effect at a low frequency, it is difficult to prevent switching noise with the magnetic shield.

  For example, when the signal processing in the DSP 3 that is the load of the switching power supply circuit PW is concentrated and when the signal processing is not so concentrated, the load current of the switching power supply circuit PW is repeated. As shown in FIG. 6, the case of 55.6 mA and the case of 34.0 mA are repeated at a cycle of 2, 4 kHz as shown in FIG. 6, and the output voltage waveform of the switching power supply circuit PW at that time is as shown in FIG. This state is also referred to as a load fluctuation of 2.4 kHz. At this time, spurious is generated in the output of the VCO circuit as shown by attaching A of level −50, 46 dB at a frequency position 2.4 kHz away from the center frequency as shown in FIG.

  In order to solve these problems, if the planar arrangement is changed so that the switching power supply circuit PW is not arranged near the VCO and PLL circuit, there is a restriction in arranging each block, or a space is secured. There is a problem that it is necessary to change the place where it is not necessary to change the location.

  An object of the present invention is to provide a switching power supply circuit in which spurious is suppressed by changing the arrangement partially without substantially changing the entire planar arrangement.

  A switching power supply circuit according to the present invention includes a battery terminal to which a battery as a power supply is connected, and receives the output from the battery via a filter having an input capacitor and a coil. In the switching power supply circuit, the input capacitor and the coil And the rest of the switching power supply circuit are separated from each other, the input capacitor and the coil are arranged close to the battery terminal position, and the input capacitor is electrically connected to the battery + terminal and the battery-terminal. Then, one terminal of a coil is electrically connected to the battery + terminal, and the battery + terminal and the filter are connected via the first wiring line and the coil electrically connected to the other terminal of the coil. And the remaining part of the switching power supply circuit The second wiring line ground at the portion provided in parallel to the first wiring line Battery - is characterized in that so as to be electrically connected to the terminal.

  According to the switching power supply circuit according to the present invention, the input capacitor and the coil constituting a part of the filter and the remaining switching power supply circuit are separated in position, and the input capacitor and the coil approach the battery terminal position. Be placed. Further, an input capacitor is electrically connected to the battery + terminal and the battery-terminal, a first terminal of the coil is electrically connected to the battery + terminal, and a first terminal is electrically connected to the other terminal of the coil. The battery + terminal and the remaining portion of the filter are electrically connected via the wiring line and the coil, and the ground in the remaining portion of the switching power supply circuit is provided in parallel with the first wiring line. It is electrically connected to the battery terminal by a wiring line.

  Therefore, the distance between the coil L1 and the switching transistor Q1 becomes long, and switching noise and load fluctuations between them may become spurious. However, the influence of the magnetic flux change generated in the coil is larger than the influence of the magnetic flux change generated in the loop of the first wiring line and the second wiring line, and the remaining part of the switching power supply circuit is affected by the switching noise. Even if it is provided in the vicinity of a portion that is easily received, spurious can be suppressed because the distance between the coil and the remaining portion of the switching power supply circuit is increased. This is particularly effective for low frequency load fluctuations that are difficult to remove.

  Hereinafter, a switching power supply circuit according to the present invention will be described according to an embodiment.

  FIG. 1 is a schematic diagram showing a planar arrangement when the switching power supply circuit PWa according to the embodiment of the present invention is mounted on the wireless communication device shown in FIG.

  The switching power supply circuit according to the embodiment of the present invention is electrically identical in configuration to the switching power supply circuit PW shown in FIG. 1 (a) and 1 (b), the same components as those in FIGS. 4 (a) and 4 (b) are denoted by the same reference numerals. A battery as a power source of the switching power supply circuit is connected to the battery + terminal and the battery − terminal.

  On the other hand, in the switching power supply circuit according to the embodiment of the present invention, the switching power supply circuit PW is made up of the rest of the filter F1 except for the input capacitor C1 and the coil L1, and the input capacitor C1 and the coil L1. The switching power supply circuit part PWa (also referred to as switching power supply circuit PWa) is divided into parts and separated, and the input capacitor C1 and the coil L1 are arranged close to the battery terminal.

  Further, the input capacitor C1 is electrically connected to the battery + terminal and the battery-terminal, and one terminal of the coil L1 is electrically connected to the battery + terminal, and the wiring line A is connected to the other terminal of the coil L1. The battery + terminal and a part of the filter F1 are connected via the coil L1 and the wiring line A, the capacitor C2 disposed in the switching power supply circuit PWa is connected, and the switching transistor Q1 is connected. Then, the ground of the switching power supply circuit PWa is connected to the ground (battery terminal) of the capacitor C1 through the wiring line B parallel to the wiring line A.

  As shown in FIG. 1A, the switching power supply circuit PWa thus configured is arranged at the same position as the switching power supply circuit PW, and the battery terminals are arranged with the wiring lines A and B parallel to each other. Between the receiving block 1 and the PLL frequency synthesizer 4 from the arrangement position of the switching power supply circuit PWa to the arrangement position of the switching power supply circuit PWa.

  By doing so, the distance between the coil L1 and the switching transistor Q1 becomes long, and there is a possibility that switching noise and load fluctuations between them become spurious.

  However, noise sneak into the VCO and PLL circuit of the PLL frequency synthesizer 4 is small, and spurious is suppressed. This is because the influence of the magnetic flux change generated in the coil L1 is larger than the influence of the magnetic flux change generated in the loop of the wiring lines A and B. Thus, spurious can be suppressed even if the switching power supply circuit PWa is provided near the VCO or the PLL circuit. This is particularly effective for low frequency load fluctuations that are difficult to remove.

  In the switching power supply circuit PWa when the load fluctuation is 2.4 kHz, if the output waveform of the VCO in the switching power supply circuit PWa is shown corresponding to FIG. 5, the frequency is 2.4 kHz away from the center frequency of the VCO circuit as shown in FIG. 2. The spurious shown with B at level -73.52 dB occurs at the position. A comparison of FIG. 2 and FIG. 5 shows an improvement of about 23 dB. The load fluctuation waveform in this case is the same as in FIG. In addition, since only the positions of the input capacitor C1 and the coil L1 constituting part of the filter F1 are moved to the battery terminal side, the effect of removing the switching noise to the battery side can be maintained. Further, the magnetic shield can be simplified, and the weight and space can be saved.

It is a schematic diagram which shows the planar arrangement | positioning at the time of mounting the switching power supply circuit concerning one Embodiment of this invention in a radio | wireless communication apparatus. It is an output waveform diagram of the VCO circuit when the switching power supply circuit according to the embodiment of the present invention is mounted on a wireless communication device. It is a circuit diagram of a switching power supply circuit. It is a schematic diagram which shows the planar arrangement | positioning at the time of mounting the conventional switching power supply circuit in a radio | wireless communication apparatus. It is the conventional output waveform figure of VCO at the time of mounting a switching power supply circuit in a radio | wireless communication apparatus. It is a wave form diagram which shows the load fluctuation | variation of a switching power supply circuit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Reception block 2 Transmission block 3 Digital signal processor 4 PLL frequency synthesizer C1, C2 and C3 Capacitor L1 and L2 Coil Q1 Switching transistor IC1 DC / DC control integrated circuit D1 Diode F1 Filter S1 Smoothing circuit PW and PWa Switching power supply circuit

Claims (1)

In a switching power supply circuit having a battery terminal to which a battery as a power supply is connected and receiving an output from the battery via a filter having an input capacitor and a coil, the input capacitor and the coil and the remaining switching power supply circuit portion And the input capacitor and the coil are disposed close to the battery terminal position, the input capacitor is electrically connected to the battery + terminal and the battery-terminal, and the coil is connected to the battery + terminal. One terminal is electrically connected, and the battery + terminal and the remaining part of the filter are electrically connected via the first wiring line electrically connected to the other terminal of the coil and the coil. And connect the ground in the remaining portion of the switching power supply circuit to the first wiring line. Switching power supply circuit is characterized in that so as to be electrically connected to the terminal - the battery by the second wiring lines provided in parallel to the.

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