JPH06165407A - Switching converter type charger - Google Patents

Abstract

PURPOSE:To obtain a compact and lightweight charger having high power factor and long life at a circumferential temperature within a specific temperature range. CONSTITUTION:A current type switching converter is constituted of a power source rectifier circuit forming a power system main circuit of a full-wave rectifier only, a pair of semiconductor switch 3, a reactor A, a push-pull transformer B and a rectifier 5. A secondary winding of the reactor A is connected to a battery 7 of load through the rectifier 5. Time ratio of the semiconductor switch 3 is normally within range of 50% to 75%, and the time ratio is so controlled that a charger input current is inproportion and followed to voltage of an alternating power source. Even if the time ratio reaches less than 50%, a secondary circuit of the reactor A is operated to have an abnormal voltage. The charger input current is a continuous current. For protecting the charger, a control power source of a switch is supplied from the battery 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly relates to a battery charger for an on-vehicle storage battery or the like, and more specifically, it converts a supply voltage from an AC power source (generally a commercial power source) into a battery voltage to obtain a constant current or a constant current. The present invention relates to the configuration and control of a power conversion unit for charging with voltage. The application of the present invention is not limited to charging a storage battery, and can be used as a constant current or constant voltage device of tens to hundreds of watts that does not require high accuracy.

[0002]

2. Description of the Related Art Conventionally, as a charger for an on-vehicle storage battery,
As illustrated in FIG. 5, the voltage of the AC power supply 1 is changed to the transformer 50.
There is a method of charging the storage battery 52 through the full-wave rectifier 51 after reducing the voltage to a required voltage by the method, a method of controlling the charging current using a thyristor, a triac, or the like.

As a method of making the charger lighter and smaller, there is a method using a switching power supply.

[0004]

In the former of those described in the prior art, the larger the capacity, the larger the size and weight of the transformer. Further, as shown in FIG. 6, the charging period in one cycle of the power supply voltage is 60
Is limited to a period in which the battery voltage exceeds the storage battery voltage 61. Such a peak current causes a decrease in power factor.

The input part of the latter switching power supply usually has a smoothing capacitor 71 as illustrated in FIG.
Uses electrolytic capacitors. Since the charging of the smoothing capacitor is limited to the period in which the power supply voltage exceeds the capacitor voltage, the power factor decreases as in the former case.

It is said that the electrolytic capacitor is susceptible to high temperatures and the life of the switching power supply is determined by the life of the electrolytic capacitor. Since the environment in which the charger is used may be relatively high at 60 to 70 ° C., it is necessary to use an electrolytic capacitor having a long life to endure this.

As a power factor improving measure for the switching power source, a power factor improving device whose main part is illustrated in FIG. 8 (for example, see CQ Publisher, Transistor Technology, September 1990 issue, separate volume) is provided in the preceding stage of the switching power source. Sometimes.
A semiconductor switch (hereinafter, referred to as a switch) 82 is opened and closed at a high frequency, and a switch closing time ratio (a closing time ratio in one cycle is set as follows, so that the waveform of the charging current to the smoothing capacitor 84 is proportional to that of the power supply voltage. It is what controls the duty ratio). Since this device also uses an electrolytic capacitor as a smoothing capacitor, the above consideration is necessary.

The circuit of the present invention is a non-energy regenerative current source converter shown in FIG. 9 (eg, Corona Harada et al.).
The basics of switching converters (see P37) are the basics. As will be described in detail later, in the configuration of FIG. 9, when the duty ratio of the switch is set to 50% or less by the overload protection operation or the like, the residual energy of the reactor or the transformer is not absorbed, and an abnormal voltage is generated to damage the switch or the like. . Further, as will be described later, since the circuit of the present invention does not have a smoothing capacitor and the output voltage of the rectification circuit changes greatly, it is necessary to control the duty ratio according to the full-wave rectification voltage.

The present invention has been made in view of the above problems of the prior art. The object of the present invention is to have a high power factor and withstand an environmental temperature of 60 to 70 ° C. for a long life. It also seeks to provide a lightweight, compact, charger.

[0010]

The structure of the present invention is made by paying attention to the fact that the storage battery is equivalent to a capacitor having a constant voltage and a large capacity. This will be described below with reference to FIGS. To achieve the above object, the charger according to the present invention includes a power supply rectifier circuit whose power system main circuit is only a full-wave rectifier, and a switching converter including a switch, a reactor, a transformer, and a rectifier. The reactor has a secondary winding, one terminal of which is connected to one electrode of a storage battery of a load and the other terminal of which is the other electrode of the storage battery via a rectifier. The transformer B is a push-pull type.

The sum of the voltage of the storage battery 7 and the forward voltage of the rectifiers (5, 6) is VO, the winding number ratio of the primary winding and the secondary winding of the transformer B is NT, and the maximum value of the AC power supply voltage is E. NT is determined so as to satisfy EMAX <NT × VO as MAX. The winding number ratio NR between the primary winding 8 and the secondary winding 10 of the reactor A is determined in consideration of the withstand voltage of the switch and EMAX.

The switching frequency of the switches (3, 4) is selected to be sufficiently larger than that of the AC power supply. The open / close frequency of the switches (3, 4) is constant, and the switches (3, 4) are opened / closed with a phase difference of 180 ° as shown in C and D of FIG. In addition, duty ratio is usually 50%
It is in the range of up to 75%, and the closing periods of both switches partially overlap.

The generator of the reference current wave 40, that is, the generator of the sine wave full wave whose average value is proportional to the rated output current of the charger and which has the same frequency and synchronized with the AC power supply, and the primary winding 8 of the reactor A A control system is configured by current (hereinafter referred to as primary current) detection means and means for comparing the reference current wave with the primary current to control the duty ratio of the switch, and the primary current follows the reference current wave. Specific examples will be described in the Examples section.

The DC power supply for the control system is supplied from the storage battery 7.

The switching frequency of the switches (3, 4) may not be made constant, but the frequency may be controlled in accordance with the change of the power supply voltage so that the amplitude of the magnetic flux of the transformer B becomes constant.

[0016]

First, the case of normal operation in which the duty ratio is in the range of 50% to 75% will be described. In this case, any one of the switches (3, 4) is closed at any time point, so that the primary current is continuously flowing. While the switches (3, 4) are both closed, the transformer B is in a short-circuit state, the entire voltage is applied to the primary winding 8 of the reactor A, and energy is stored in the reactor. During this period, the secondary winding 10 of the reactor A (hereinafter,
No current flows in the secondary winding) because it is blocked by the rectifier 9.

The state of the transformer B will be supplementarily described. The rate of current increase for each is the same, though the current flowing through the switch that closed earlier is greater than that of the other.
Since the magnetic fluxes caused by the respective currents are set in opposite directions, the increased magnetic flux components are canceled out, and the transformer magnetic flux becomes constant and no induced voltage is generated.

When either of the switches is opened, the primary voltage of the transformer during charging is higher than the power supply voltage as described above, so that the pressure of the primary winding 8 of the reactor A has the opposite polarity, and the sum of the primary voltage and the power supply voltage. It affects the primary winding of the transformer. The charging operation for the storage battery 7 is in one of the following two modes depending on the magnitude of the power supply voltage at that time.

One is a region where the magnitude E of the power supply voltage is small, that is, E + NR × VO <NT × VO, and the energy of the reactor is discharged to the storage battery through the secondary winding. When the voltage of the primary winding 8 of the reactor becomes NR × VO corresponding to the charging voltage of the storage battery, it is clamped to that value, and the sum with the power supply voltage, that is, the voltage applied to the primary winding of the transformer B is necessary to charge the storage battery. The voltage does not reach NT × VO.

The other one is a region where the magnitude E of the power supply voltage is large, that is, E + NR × VO> NT × VO, and the energy of the reactor is discharged to the storage battery via the transformer B. When the voltage applied to the primary winding of the transformer B reaches a voltage NT × VO sufficient to charge the storage battery, the transformer primary voltage is clamped to that value, and the voltage of the primary winding 8 of the reactor A is a voltage sufficient to charge the storage battery. NR x VO
Does not reach

The energy thus stored in the reactor is discharged to the storage battery through the secondary winding in the region where the power supply voltage E is small and through the transformer in the region where E is large. Although the output voltage of the full-wave rectifier 2 changes significantly with time, the reactor has the above-described function, so that the charging operation is performed over almost the entire period of the power supply voltage.

Next, the duty ratio described in the section of the prior art is 5
A case in which it is 0% or less, that is, when both the switches 3 and 4 are open will be described. Switch 3 with the reactor energized,
Even when 4 is opened and the voltage across the primary winding of the reactor rises, NR × VO is the upper limit as described above, and the energy of the reactor is discharged to the storage battery via the secondary winding, causing an abnormality. No voltage is generated.

By controlling the duty ratios of the switches (3, 4) described above, the waveform of the primary current is in phase with the output voltage of the full-wave rectifier 2 and the magnitude thereof is proportional thereto.

If the DC power supply for the control circuit of the switches (3, 4) is supplied from the storage battery 7, the switches (3, 4) are turned on even if the power of the charger is turned on without connecting the storage battery to the charger. ) Is interlocked. When the power is turned on with the storage battery unconnected and the switches (3, 4) operate,
The energy accumulated in the reactor is not absorbed and an abnormal voltage is generated, which damages the switches.

[0024]

EXAMPLES Examples will be described with reference to FIGS. The configuration and operation of FIG. 1 have already been described, and a supplementary explanation such as numerical examples will be given here. AC power source 1 is a commercial power source of 100V,
The voltage of the storage battery 7 is 24V, the forward voltage of the rectifier (5, 6, 9) is 1V, the reactor NR is 2, and the transformer NT is 6
Then, the charging current to the storage battery is supplied from the secondary winding of the reactor when the output voltage of the full-wave rectifier 2 is in the range of 0 to 100V, and from the transformer in the range of 100V to 141V. If the cable from the charger to the storage battery is long, it is advisable to connect a capacitor in parallel with the storage battery immediately after the rectifier (5, 6, 9).

C and D in FIG. 2 are when the duty ratio is 75%,
At this time, the ratio of the charging period becomes maximum. The switching frequency is, for example, 100 kHz. F is the time chart of the storage battery charging current and G is the time chart of the primary current, but for the sake of clarity, it shows the case where the power supply voltage is constant, that is, the duty ratio is constant. This corresponds to the case of FIG. FIG. 4 is a schematic diagram of the primary current in the case of the present invention, which will be described later.

FIG. 3 is a block diagram of an essential part of the duty ratio control system of the switch. Full wave rectifier 2, reference current wave generator 30
Other than that, only one side of the push-pull is shown.

The reference current wave generator 30 is assumed to take out the output voltage of the full-wave rectifier 2 via a photocoupler (not shown), for example. If the voltage fluctuation of the output cannot be ignored, it will be compensated.

The primary current is detected via the current transformer 31.
The charging current of the storage battery 7 may be detected and used instead of the primary current.

H is a known switching power supply IC.
The difference between the output voltage of the reference current wave generator 30 and the detected voltage of the current transformer 31 is amplified by the comparison unit 32, and the pulse width, that is, the duty ratio is controlled by the pulse width control unit 33.

Reference numeral 41 in FIG. 4 is a schematic diagram of the primary current obtained by the above control, and the component of the same frequency as the AC power source has the same shape as the reference current wave 40. The duty ratio changes depending on the magnitude of the power supply voltage and the rate of increase.

[0031]

Since the present invention is configured as described above, it has the following effects.

In the battery charger according to the first aspect of the present invention, due to the action of the reactor, the charging operation is performed during the entire period except when the power supply voltage becomes zero. Since the primary current is continuous, the switching noise generated from the charger is small. Since the reactor has a secondary winding and is connected to the storage battery of the load, the abnormal voltage does not occur in the charger even when the duty ratio of the switch becomes 50% or less due to overload protection operation or the like. Long life because there is no rectifying capacitor. Since it is a high frequency switching converter, it is lightweight and compact.

In the charger of claim 2, the primary current is in phase with the AC power supply, and the magnitude of the current is proportional to that of the power supply voltage, so the power factor of the charger is good.

In the battery charger of the third aspect, since the DC power supply for the control system of the switch is supplied from the storage battery of the load, the switch is interlocked even if the charging source is turned on without connecting the storage battery to the charger, Do not damage the switch etc.

[Brief description of drawings]

FIG. 1 is a power system main circuit diagram of a charger.

FIG. 2 is a time chart of a main part of a main circuit.

FIG. 3 is a block diagram of an essential part of a ratio control system for opening / closing a semiconductor switch.

FIG. 4 is a schematic diagram of a reference current wave and a primary current.

FIG. 5 is a circuit diagram showing a conventional example of a charger.

FIG. 6 is a diagram showing an example of a conventional charging current.

FIG. 7 is a block diagram showing an example of a main part of a switching power supply.

FIG. 8 is a block diagram showing an example of a main part of a power factor correction device.

FIG. 9 is a circuit diagram showing a main part of a non-energy regenerative current source converter.

[Explanation of symbols]

A, 81, 93 Reactor B, J, 50 Transformer C Time chart of semiconductor switch 3 D Time chart of semiconductor switch F Time chart of charging current G Time chart of reactor primary winding current H Switching power supply IC 1 AC power supply 2, 51, 70, 80 Full-wave rectifier 3, 4, 82, 91, 92 Semiconductor switch 5, 6, 9, 9, 83, 94, 95 Rectifier 7, 52, 73, 86 Storage battery 8 Primary winding 10 Secondary winding 20 Closed Period 21 Open period 22 Charging current 23 Switch 3, 4 Reactor primary winding current when closed simultaneously 24 Switch 3, 4 Reactor primary winding current when either is open 30 Reference current wave generator 31 Current transformer 32 Comparison section 33 Pulse width control unit 40 Reference current wave 41 Reactor primary winding current 42, 60 Power supply voltage 50 Transformer 61 Storage Battery voltage 62 Charging current 71, 84 Smoothing capacitor 72, 85 Power converter 90 DC power supply 96 Capacitor 97 Load

Claims (3)

[Claims] 1. A power system main circuit comprises a full-wave rectifier (2), a semiconductor switch (3, 4), a reactor (A), a transformer (B), and a rectifier (5, 6). A switching converter type charger having a secondary winding (10), one end of which is connected to a load storage battery (7) via a rectifier (9). 2. The switching ratio of the semiconductor switches (3, 4) is controlled so that the current in the primary winding (8) of the reactor (A) is proportional to the output voltage of the full-wave rectifier (2). Switching converter charger. 3. The switching converter type charger according to claim 1, wherein the DC power supply for the control system of the semiconductor switches (3, 4) is supplied from the storage battery (7).