JPH07322525A - Power supply circuit - Google Patents

Abstract

(57) [Summary] [Object] The present invention provides a charger having a high power factor, a small number of parts used, and an extremely simple circuit configuration. According to the present invention, a DC-DC converter 13 for transforming a full-wave rectified wave obtained by a rectifying diode 12 into another full-wave rectified wave having different voltage levels, and a switching
Choke coil 1 when the transistor 14c is on
The current supplied from the DC-DC converter 13 accompanying the ON / OFF operation of the step-up active filter 14 that discharges the energy stored in the battery 4a to the battery 15 through the diode 14b during the OFF operation, and the ON / OFF operation of the switching transistor 14b. The current sensor 14d for detecting the current is controlled, and the phase of the current detected by the current sensor 14d is controlled to match the phase of the voltage of the full-wave rectified wave. At the same time, when the level of the detected current decreases, DC-
The control circuit 16 performs control to increase the transformation ratio in the DC converter 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply circuit, and more particularly to a power supply circuit for charging a large capacity battery mounted on an electric vehicle.

[0002]

2. Description of the Related Art Generally, a battery mounted on an electric vehicle requires a large capacity battery because it directly drives a motor. Therefore, a large charger is required to charge this battery. However, such a charger is usually used installed in a part of the vehicle body so that its output terminal is always directly connected to the electrode terminal of the battery. For this reason, it is desirable that the charger used for such purposes be small and lightweight.

Therefore, the charger used for such a purpose is an AC transformer system (so-called straight system) whose size and weight are large in the process of obtaining the DC required for charging the battery from the AC supplied from the commercial power source. ) Is not adopted, but a DC transformation method using a small and lightweight DC-DC converter (DC-DC converter) is adopted. further,
Since the battery is charged with a large current, switching loss is also important. In order to reduce this loss, the resonance type D
A C-DC converter is used.

The circuit configuration of a conventional charger using the resonance type DC-DC converter as described above will be described below with reference to FIG. In the circuit shown in the figure, for example, the AC voltage supplied from the commercial power source 1 of 200V is
For example, full-wave rectification is performed by the rectification diode 2 formed of a bridge or the like, and the full-wave rectification wave at this time is smoothed by the step-up active filter 3 located at the subsequent stage.
The active filter 3 is configured by connecting and arranging the choke coil 3a, the diode 3b, the electrolytic capacitor 3c, and the switching transistor 3d so that the active filter 3 forms a step-up type circuit.
In this circuit, a first current sensor 3e for detecting the current given from the rectifier circuit 2 in accordance with the on / off operation of the switching transistor 3d is inserted.

That is, the active filter 3
Basically releases the energy of the full-wave rectified wave stored in the choke coil 3a when the switching transistor 3d is turned on to the electrolytic capacitor 3c through the diode 3b when it is turned off. By repeating ON / OFF operation at high speed,
It is designed to obtain the required boosting action. In addition, at this time, the first control circuit 4 performs control to match the phase of the current supplied from the rectifier circuit 2 with the phase of the voltage of the full-wave rectified wave so that a sufficient smoothing action can be obtained in the active filter 3. By performing the operation on the switching transistor 3d, the power factor in the active filter 3 is improved. In other words, the first control circuit 4 changes the voltage of the full-wave rectified wave so that the level of the current detected by the first current sensor 3e always increases and decreases in accordance with the level of the voltage of the full-wave rectified wave. A pulse wave (PFM wave) frequency-modulated according to the level of the switching transistor 3
It is designed to be given to the base of d. As a result of the above, a DC voltage in which the AC component of the full-wave rectified wave is sufficiently smoothed can be obtained at the electrolytic capacitor 3c.

Next, the DC voltage obtained in the electrolytic capacitor 3c is given to the DC-DC converter 5 located in the subsequent stage, where the DC voltage (charging voltage) transformed into another different voltage level is It is applied to the battery 7 through the reverse current blocking diode 6. At this time, DC-D
The C converter 5 is adapted to always generate a DC voltage having a higher level than the terminal voltage at the time of charging the battery 7, and the control for this purpose is to detect a current (charging current) flowing in the battery 7. 2 current sensor 8,
This is performed by the second control circuit 9 that changes the level of the direct current generated by the DC-DC converter 5 according to the level of the detected current.

[0007]

By the way, this type of charger is desired to be small in size and lightweight, as mentioned at the beginning. Therefore,
As long as the function as a charger is sufficiently ensured, it can be said that the number of components used in the circuit should be as small as possible. In particular, in this type of charger, the improvement of the power factor by the active filter 3 is an important factor for ensuring the function as the charger. While keeping
It is highly desired to reduce the number of parts used and simplify the circuit configuration.

The present invention has been made based on such a demand, and an object thereof is to provide a power supply circuit having a high power factor, a small number of parts used, and an extremely simple circuit configuration. It is in.

[0009]

The structure of the present invention has a rectifier circuit for full-wave rectifying an alternating current supplied from a commercial power source, and a full-wave rectified wave obtained by the rectifier circuit at another different voltage level. A DC-DC converter that transforms into a full-wave rectified wave,
A choke coil, a diode, and a switching element are included, and the energy of the full-wave rectified wave obtained by the DC-DC converter, which is stored in the choke coil when the switching element is on, is supplied to the diode when the off operation is performed. Through the active filter, a current sensor for detecting a current given to the battery through the active filter from the DC-DC converter in accordance with ON / OFF operation of the switching element, and detection by the current sensor The switching element is controlled to match the phase of the current with the phase of the voltage of the full-wave rectified wave obtained by the DC-DC converter, and at the same time, the switching of the DC-DC converter is performed according to the level of the output current. Consists of a control circuit that controls the frequency It has been.

[0010]

In the present invention, first, the alternating current supplied from the commercial power source is full-wave rectified by the rectifying circuit, and the full-wave rectification obtained by the rectifying circuit is performed by the DC-DC converter located at the subsequent stage of the rectifying circuit. The wave is transformed into another full-wave rectified wave having different voltage levels, and is further stored in the choke coil when the switching transistor is turned on by the step-up active filter located after the DC-DC converter. Full wave rectified wave energy is released to the battery through the diode during its off operation. Then, the current sensor causes the DC-DC to follow the ON / OFF operation of the switching transistor.
The current given to the battery from the converter through the active filter is detected, and the phase of the current detected by the current sensor is detected by the control circuit.
The switching transistor is controlled to match the phase of the full-wave rectified wave voltage obtained by the converter.

That is, according to the present invention, the power factor of the active filter is kept equal to that of the conventional one,
Moreover, some components that were required in the past (electrolytic capacitors, reverse current element diodes,
It is not necessary to use a first or second current sensor or the like).

[0012]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a power supply circuit according to an embodiment of the present invention. As shown in the figure, in the power supply circuit according to this embodiment, as in the conventional case, for example, the alternating current supplied from the 200-volt commercial power supply 11 firstly causes the rectifying diode 12 including a diode bridge or the like. It is designed to be full-wave rectified. In this power supply circuit, the full-wave rectified wave obtained by the rectifier diode 12 is transformed into another full-wave rectified wave having a different voltage level by the DC-DC converter 13 located at the subsequent stage, and The full-wave rectified wave obtained by the DC-DC converter 13 is smoothed by the step-up active filter 14 located at the subsequent stage.

Here, the active filter 14 used in the power supply circuit of this embodiment has a choke coil 14a, a diode 14b, and a choke coil 14a so that the active filter 14 forms a step-up circuit.
And the switching transistor 14c are connected and arranged. In addition, this active filter 14
Does not include the electrolytic capacitor (3c) that has been conventionally used, but the battery 15 is directly connected to the output terminal thereof. This is because the battery 15 itself has a large capacitance component with respect to the reverse voltage, and therefore it is not necessary to dare to perform smoothing by using an electrolytic capacitor. Therefore, in the active filter 14, the switching transistor 14c
Stored in the choke coil 14a during the on-operation of the
The energy of the full-wave rectified wave obtained by the C-DC converter 13 is directly discharged to the battery 15 through the diode 14b during the off operation, and by repeating this on / off operation at high speed, the required boosting action can be obtained. It is designed to be used. Then, in the circuit of the active filter 14, the switching transistor 14c
A current sensor 14d for detecting a current given to the battery 15 from the DC-DC converter 13 through the active filter 14 in accordance with the ON / OFF operation of is inserted, and particularly in the power supply circuit of the present embodiment,
Based on the current detected by this single current sensor 14d,
Operation and active in the DC-DC converter 13
The operation of the filter 14 depends on the single control circuit 16
(The structure is equivalent to a combination of the conventional first control circuit (4) and the conventional second control circuit (9)).

That is, the control circuit 16 controls the switching of the active filter 14 so that the phase of the current detected by the current sensor 14d matches the phase of the voltage of the full-wave rectified wave obtained by the DC-DC converter 13. This is done for the transistor 14c. That is, in the control circuit 16, when the active filter 14 is controlled, the level of the current detected by the current sensor 14d always follows the voltage level of the full-wave rectified wave obtained by the DC-DC converter 13. A pulse wave (PFM wave) that is frequency-modulated according to the level of the voltage of the full-wave rectified wave so as to increase or decrease is applied to the base of the switching transistor 14c. The power factor at 14 is improved.

Here, considering the individual parts necessary for constructing the above-described power supply circuit in comparison with the individual parts used in the conventional power supply circuit, first, the conventional charger will be described. In this charger, the electrolytic capacitor (3c) used in the active filter (3) in
It becomes unnecessary for the above reasons. Further, the reverse current element diode (6) used conventionally has the function of the active filter 1 in the charger of this embodiment.
It is unnecessary because it is applied to the diode 14b of No. 4. Further, the first current sensor (3
e) and the second current sensor (8) act as a DC-DC filter for the active filter 14 in the charger of this embodiment.
Since the converter 13 is located in the latter stage, it is possible to combine the functions thereof into the single current sensor 14d. That is, the number of parts used in the charger of the present embodiment is three smaller than that of the conventional one, and as a result, the power filter 14 has the same power factor as that of the conventional one, but the circuit configuration is small. An extremely simple charger can be obtained.

[0016]

As described above in detail, according to the present invention, the power factor of the active filter is kept equal to that of the conventional one and, moreover, it has been required in the past to construct the circuit. Some components (electrolytic capacitor, reverse current element diode, first or second current sensor, etc.)
Since it is no longer necessary to use, the number of parts used is reduced and the circuit configuration is extremely simplified. As a result, not only is the size and weight further reduced, but
At the same time, the manufacturing cost can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a power supply circuit according to an embodiment.

FIG. 2 is a block diagram showing a configuration of a conventional power supply circuit.

[Explanation of symbols]

 11 Commercial Power Supply 12 Rectifier Diode 13 DC-DC Converter 14 Active Filter 14a Choke Coil 14b Flywheel Diode 14c Switching Transistor 14d Current Sensor 15 Battery 16 Control Circuit

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H02M 7/217 9180-5H

Claims (2)

[Claims] 1. A rectifier circuit for rectifying an alternating current supplied from a commercial power source, a DC-DC converter for transforming a rectified wave obtained by the rectifier circuit into another rectified wave having different voltage levels, and a choke coil. , A diode and a switching element, and the energy of the rectified wave obtained by the DC-DC converter, which is stored in the choke coil when the switching element is on, is discharged to the battery through the diode when the off operation is performed. An active filter, and the D
A current sensor for detecting a current given to the battery from the C-DC converter through the active filter, and a phase of a current detected by the current sensor is matched with a phase of a rectified wave voltage obtained by the DC-DC converter. A power supply circuit, comprising: a control circuit that controls the switching element and, at the same time, controls the switching frequency of the DC-DC converter according to the level of the output current. 2. The power supply circuit according to claim 1, wherein a battery is connected as a load.