JPH027834A - Battery charger - Google Patents

Abstract

PURPOSE:To reduce the size of a battery charger, to improve the economical properties and to enable reduction of commutation loss by utilizing the bilateral on characteristic of a FET transistor. CONSTITUTION:When an AC input phi1 has positive polarity, the FET1 in its arm is biased nigatively and turned OFF, then FET2, FET3 are baised forwardly and tuned ON thus supplying generated current through a path of a diode D1 - a battery BAT - FET2, FET3. When the AC input PHI1 has negative polarity, the gate of the FET1 is biased positively and turned ON bilaterally thus making the charging current flow through a path of a diode D1 - a battery BAT-Fet2, FET3. When the AC input phi1 has negative polarity, the gate of the FET1 is biased positively and turned ON bilaterally thus making the charging current flow through a path of a diode D2 - the battery BAT-FET1, FET3. When the battery BAT is fully charged, it is detected through a control circuit CONT and a positive bias signal is provided. All FETs are turned ON and the AC input is shortcircuited through a path of a generating coil EXT-FET1, FET2 or FET3 thus maintaining the battery voltage at a predetermined level.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a charging device for a battery mounted on a vehicle such as a two-wheeled vehicle, and particularly provides a charging device that is compact and economical and reduces losses. Figure 1 is a conventional circuit diagram of this type, where M is a permanent magnet generator, ZXT is its generating coil, D1 to D4 are diodes forming a full-wave (bridge) rectifier, 3AT is a battery, and C0NT is a The battery voltage detection control circuits S CR+ and S CR2 are thyristors connected in parallel (in opposite directions) to diodes D3 and D4, respectively, and have gates connected to the control circuit C0NT. In this operation, the alternating current i generated by the permanent magnet power generation fiM is connected to the bridge diode D1 to
It is rectified by D4 and charged to BA].

Eventually, when IIAT becomes fully charged, the C0NT section detects the BAT terminal voltage and turns on the SCR.

Give an ignition signal to 5CR2. As a result, 5CR3CR
2 is in the "ON" state, and the generated current is short-circuited by 5CR2, as indicated by the dotted line 12, and charging to BAT is stopped. (At this time, permanent magnet generators have a large output impedance, so there is no problem even if the output is short-circuited.) This conventional device requires multiple anti-parallel circuits of diodes and thyristors in the main circuit. It has the disadvantage that it requires a large number of parts and rectification loss of the diode becomes a problem.

The present invention provides a charging device which eliminates such drawbacks, and which rectifies the AC output of a three-phase AC generator via a rectifier to charge a battery, and also detects the battery voltage and short-circuits the AC output. In the battery charging device for maintaining the battery voltage at a predetermined value, each arm forms a full-wave rectifier circuit consisting of a diode and a field effect transistor, and has a gate control circuit for the field effect transistor, and the gate Each control circuit is characterized by having a function of sending a negative bias signal (or positive bias signal) to the gate of the field effect transistor of the self-arm in synchronization with the input positive potential (or negative potential) of the self-arm. It is.

FIG. 2 is a circuit diagram of an embodiment of the present invention, in which the same symbols as in the conventional example indicate equivalent parts.
Instead of field effect transistor F ET'+ , F
A three-phase full-wave rectifier circuit is formed using ET2 and FET3. Then, the control circuit C0NT sends a negative bias signal to the gate of the field effect transistor of the own phase arm in synchronization with the input positive potential of each phase of the three-phase AC input, thereby performing full-wave rectification via the field effect transistor of the other arm. Form a circuit to charge the battery. That is, this operation will be explained using the operation waveforms of FIG. 3.As is well known, in three-phase AC, the human phase differs by 120 degrees. Therefore, when the control circuit C0NT detects the positive potential of the input phases φ1, φ2, and φ3, it sends the signals (a), (b), and (c) to the gates of the FETs and FET3, respectively (Fig. 3(a), (b) ) (c)) With this configuration, when the AC human power φ1 is positive, during this period (1, ~14), the self-arm FETI is negatively biased and remains off, and the pond FET2 or ~ button FET3 is turned off. By being forward biased and turned on, the generated current is transferred from the diode D1 to the battery BA T
The flow battery BAT is charged through the paths F ET 2 and F ET 3. On the other hand, when the polarity is reversed, FETI
The gate of is positively biased and turned on in both directions, and the charging current flows through diode D2 - battery BAT and F E
As a result of sending a positive bias signal (FIG. 3d) to each gate of FET 2 and FET3,
Both ETI to FET3 are in the on state and the power generation coil)Iy
E X “r” F E T H, F E T 2
In addition, each of the AC inputs is short-circuited in the FET3 path to maintain the battery voltage at a required value.

Figure 4 shows an example of the control circuit, and in the figure COMI
~C0M4 →-The open circuit COM1~CO traps and sends a positive bias signal to the gates G1 to G3 of the self-amp field effect transistors, respectively, when the respective input potentials are negative (-). Also, C0M4 is the battery voltage (fully charged)
The output (10 inputs) detected by resistors R, , J and the reference voltage K
are compared and the reference signal S is changed to obtain each FET,
~FET 3 is simultaneously positively biased.

As described above, according to the present invention, by utilizing the bidirectional ON characteristic of the field effect transistor, the conventional anti-parallel circuit of an SCR and a diode can be equivalently replaced with one field effect transistor, thereby making the circuit smaller and more economical. By utilizing the low on-resistance of field effect transistors, it is possible to reduce rectification loss compared to rectifier diodes, which has great practical effects.

[Brief explanation of the drawing]

FIG. 1 is a conventional circuit diagram, and FIGS. 2, 3, and 414 are circuit diagrams of an embodiment of the present invention, an operation explanatory diagram, and a wiring diagram of a control circuit. In the figure, M is the generator, EXT is the generator coil, D, ~D
3. Da, DC are diodes, SCR15CR2 are thyristors, C0NT is a control circuit, BAT is a battery, F
ETI, FET2, and FE'r3 are field effect transistors, and COMI to C0M4 are comparators.

Claims (2)

[Claims] (1) The AC output of the three-phase AC generator is rectified via a rectifier to charge the battery, and the battery voltage is detected and the AC output is short-circuited to maintain the battery voltage at a predetermined value. In the battery charging device, each arm forms a three-phase full-wave rectifier circuit consisting of a diode and a field effect transistor, and has a gate control circuit for the field effect transistor, and each gate control circuit has a positive input potential of its own arm. 1. A battery charging device characterized by having a function of sending a negative bias signal (or positive bias signal) to the gate of a field effect transistor of a self-arm in synchronization with (or negative potential). (2) Battery charging according to claim (1), characterized in that the control circuit is provided with a function of simultaneously sending a positive bias signal to each field effect transistor when the battery voltage detects a fully charged state. Device.