JPH0646535A - Charger - Google Patents

Abstract

PURPOSE:To improve harmonic distortion in a capacitor input type rectifier circuit by employing a switching power supply at a power converting section of a boosting charger. CONSTITUTION:The charger comprises an AC input rectifier D1, a switch SW1 performing high frequency switching of rectified pulsating current, a transformer T1 transmitting the pulsating primary power to the secondary, rectifying/ smoothing circuits D2, D3, C1, CO for rectifying/smoothing the secondary power to produce DC current for charging a battery, a charge control circuit 3 producing a charging current control command, a current detecting circuit 2, and a circuit 1 for controlling the switch SW1 with a predetermined frequency and pulse width. Furthermore, full-wave rectified pulsating AC input waveform is subjected to high frequency switching with a pulse width limited by a current detecting circuit 2 thus widening the conduction angle of input current, suppressing harmonic distortion, and improving power factor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery charger which charges a battery with a charging current of 1 C or more, in which harmonic distortion is reduced and the power factor is improved.

[0002]

2. Description of the Related Art An example of the prior art will be described with reference to FIG. In the figure, D1 is a full-wave rectifier for full-wave rectifying the AC input, C2 is a smoothing capacitor, SW1 is a switch for switching the rectified waveform, T1 is a transformer, D
2, D3 are rectifier diodes on the secondary side of the transformer T1, C
Reference numeral 1 is a smoothing capacitor, CH is a choke, and 4 is a battery. Reference numeral 1 is a control circuit for PWM controlling the switch SW1. Reference numeral 5 is a high-frequency filter circuit, 3 is a charge control circuit, which issues a control command for the charge flow to the control circuit 1 and detects the voltage of the battery 4. Reference numeral 2 is a current detection circuit, which detects a charging flow.

The DC voltage on the primary side, which is obtained by rectifying the AC input by the rectifier 1 and smoothed by the smoothing capacitor C2, is used in the control circuit 1.
Switch SW1 with the frequency and pulse width set by
Is pulsed by and transmitted to the secondary side through the transformer T1. On the secondary side, this waveform is rectified by a rectifier diode D2,
The battery 4 is charged by the charging flow that is DC-converted by D3, the choke CH, and the smoothing capacitor C1. The charging flow is controlled by the control circuit 1 controlling the switch SW1 based on commands from the charging control circuit 3 and the current detection circuit 2.

[0004]

However, in the charger in the conventional example, since the AC input rectifier circuit is a capacitor input, as shown in FIG. 4, the waveform of the rectified voltage V _IN contains ripples. On the other hand, the pulse ratio is greatly improved, but the input current I _IN has a narrow conduction angle and a large peak value, resulting in a pulse-like waveform with high harmonic distortion and a low power factor of, for example, 0.6 to 0.7. To do. Therefore, there is a problem that the larger the charger, the greater the adverse effect on other electronic devices and the power system.

The present invention has been made in view of the above circumstances, and provides a charger with reduced harmonic distortion and improved power factor without adversely affecting other electronic devices and power systems. The purpose is to provide.

[0006]

In order to solve the above problems, the battery charger of the present invention is a battery charger that charges a battery with a charging current of 1 C or more and controls charging by detecting the battery voltage. A rectifier for full-wave rectifying the AC input waveform, a switch for switching the rectified pulsating flow at a high frequency, a transformer for transmitting the primary side power pulsed by the switch to the secondary side, and a rectifier for the secondary side power. A rectifying / smoothing circuit that produces a DC current that smoothes and charges the battery, a charge control circuit that detects the battery voltage and issues a control command for the charge flow, a current detection circuit that detects the current, and the switch A control circuit for controlling the frequency and the pulse width is provided, and the pulsating flow of the full-wave rectified AC input waveform is switched at a high frequency to widen the conduction angle of the input current to reduce the harmonic distortion and reduce the power factor. Improved It has a feature to the door.

[0007]

In the charger of the present invention having the above structure, no capacitor is used for smoothing the pulsating current after rectifying the AC input. For this reason, the AC input waveform and the waveform after rectification are substantially the same, the conduction angle of the AC input current is significantly wider than the conduction angle of the capacitor input type rectifier circuit, and harmonic distortion is reduced. The power factor of this charger is improved.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. In the figure, the elements denoted by the same reference numerals as those in FIG. 3 indicate the same elements, and the description thereof will be omitted. The rectifying / smoothing circuit that rectifies / smooths the secondary power to generate a direct current for charging the battery is composed of rectifying diodes D2, D3,
It is composed of a choke CH and a smoothing capacitor C1. The difference between the conventional example and the embodiment of the present invention is that the smoothing capacitor C2 for smoothing the pulsating current after rectifying the AC input is not used. In the figure, V _BATT is the voltage of the battery 4, _VL is the voltage drop of the choke CH, and V _D is the voltage drop of the rectifier D2. V _IN is a rectified voltage, and I _IN and I _IN 'are input currents. These voltages,
The electric current will be described later with reference to FIG.

In the case of a direct-current power source using an ordinary converter, it is necessary to use a capacitor input to make a direct current with a small amount of ripple after rectification. This is because the stable energy needs to be sent to the secondary side even when the DC output voltage is stabilized and a momentary interruption occurs in the AC input waveform, so the energy is stored in the capacitor. On the other hand, in the case of the charger, it is not necessary to take into consideration the instantaneous interruption of the charging flow for charging the battery.

Next, the conduction angle of the input current will be described with reference to FIG. Assuming that the transformer ratio of the transformer T1 is N, the threshold voltage V _IN of the rectified voltage V _IN at the time when a charging flow flows.
_A becomes V _A = N · V _IN > V _BATT + V _D + V _L. An input current I _IN that flows when the rectified voltage V _{IN is} higher than the voltage V _A ,
As shown in the figure, the conduction angle of I _IN 'is significantly wider than the conduction angle of the capacitor input type rectifier circuit, the harmonic distortion is reduced, and as a result, the power factor of this charger is improved.

[0011]

As described above, the battery charger according to the present invention has a rectifier for full-wave rectifying an AC input waveform, a switch for switching the rectified pulsating flow at a high frequency, and a primary side pulsed by the switch. A transformer that transmits electric power to the secondary side, a rectifying / smoothing circuit that rectifies and smoothes the secondary electric power to create a direct current that charges the battery, and a charging that detects the battery voltage and issues a control command for charging double current. A control circuit, a current detection circuit that detects a current, and a control circuit that controls the switch with a specified frequency and pulse width, and input by switching the pulsating current of a full-wave rectified AC input waveform at a high frequency Widening the current flow angle to reduce harmonic distortion,
Since the power factor has been improved, there is no reduction in power factor due to the use of this charger, and it will not adversely affect other electronic devices and power systems.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a charger with improved power factor according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of an input current according to an embodiment of the present invention.

FIG. 3 is a circuit diagram of a charger in a conventional example.

FIG. 4 is an explanatory diagram of an input current in a conventional example.

[Explanation of symbols]

 C1, C2 Smoothing capacitor CH Choke D1 Rectifier D2, D3 Rectifier diode SW1 switch T1 Transformer 1 Control circuit 2 Current detection circuit 3 Charge control circuit 4 Battery 5 High frequency filter circuit

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical indication H02M 7/21 Z 9180-5H

Claims (1)

[Claims] 1. A charger that charges a battery with a charging current of 1 C or more and controls charging by detecting the battery voltage, and a rectifier for full-wave rectifying an AC input waveform and a rectified pulsating current at high frequency. A switch for switching, a transformer for transmitting the primary side power pulsed by the switch to the secondary side, a rectifying / smoothing circuit for rectifying / smoothing the secondary side power to generate a direct current for charging the battery, and a battery A full-wave rectified circuit provided with a charge control circuit that detects a voltage and issues a control command for a charge flow, a current detection circuit that detects a current, and a control circuit that controls the switch with a specified frequency and pulse width. A charger characterized in that the pulsating current of the AC input waveform is switched at a high frequency to widen the conduction angle of the input current, reduce harmonic distortion, and improve the power factor.