JPH0715883A - Charger - Google Patents

Abstract

PURPOSE:To eliminate energy loss for causing an increase in heat generation of a saturable reactor as a result of loss of the reactor from unnecessary energy since energy to be transmitted from a primary side to a secondary side is increased larger than energy necessary for charging a secondary cell by controlling a charging circuit at the secondary side. CONSTITUTION:A switching element SW1 is normally controlled according to an output signal from an error amplifier 4 through a photocoupler 8, a control IC 7 to control a secondary side output of a transformer T1 thereby to charge a secondary cell 2 at a constant current. When an open voltage of the cell 2 is measured, a maximum reset current is supplied from a rest current supply circuit 6 to a saturable reactor 3 on the basis of a command of a secondary cell voltage measuring circuit 5, the reactor 3 is set to an unsaturated state thereby to eliminate a charging current, and an open voltage of the cell 2 is measured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging device for charging a secondary battery with a constant current, and more particularly to a charging device capable of satisfactorily measuring the open circuit voltage of the secondary battery.

[0002]

2. Description of the Related Art In the first prior art, a semiconductor switch is connected to the output of a charger and the semiconductor switch is turned on / off.
By doing so, the secondary battery was charged with a constant current. When detecting the battery voltage, turn off the semiconductor switch. In the second conventional technique, the secondary battery is charged with a constant current by controlling the element that switches the DC voltage on the primary side of the transformer. When the battery voltage is detected, the power transmission from the primary side to the secondary side is stopped by a signal for stopping the operation of the control unit or a signal for closing the output pulse. However, in the first conventional technique, when the charging current of the secondary battery is several A (rapid charging, etc.), a large current switch is required as a semiconductor switch. further,
Since the charging current of several amperes is cut off, a large loss occurs in the switch. As a result, the cost increase and reliability of the switch have been a problem. Further, in the second conventional technique, when the power supply from the primary side to the secondary side is stopped, the power supply voltage cannot be supplied to the secondary battery voltage measurement circuit, so the power supply to the secondary battery voltage measurement circuit is not possible. Since the voltage supply circuit must be provided again, there is a problem that the cost is increased and the shape of the charging device is increased. Therefore, the present applicant proposes a solution to these problems by Japanese Patent Application No. 4-100573.

Based on FIGS. 3 and 4, Japanese Patent Application No. 4-100
The outline of the technology of No. 573 will be described. Normally, the reset current supplied from the reset current supply circuit 6 to the saturable reactor 3 is controlled by the output signal of the error amplifier 4, and the saturable reactor 3 controls the charging current to charge the secondary battery 2 with a constant current. When the open circuit voltage of the secondary battery 2 is measured, the reset current supplied from the reset current supply circuit 6 to the saturable reactor 3 is maximized by the output signal of the secondary battery voltage measurement circuit 5, and the saturable reactor 3 is unsaturated. Put in a state. Secondary battery 2 with charging current cut off (open state)
Measure the open circuit voltage of.

[0004]

However, as shown in FIG. 3, since the charging circuit is controlled on the secondary side, the energy transferred from the primary side to the secondary side is generated by the secondary battery 2. There is a problem that the energy required to charge the saturable reactor 3 becomes larger than the energy required for charging, and the unnecessary energy causes a loss in the saturable reactor 3, resulting in large heat generation of the saturable reactor 3. That is, V1 in the figure is an applied voltage of the transformer T1, V2 is an output voltage of the transformer T1, V3 is a voltage required for charging the secondary battery 2, and VSR is not necessary for charging the secondary battery 2. This is the voltage applied to the required saturable actuator 3.

FIG. 4 is a diagram showing waveforms at various points in the circuit diagram of FIG. V1 in (a) is the rectifier D1
It is a voltage obtained by switching the voltage Vi rectified by the switching element SW1 and is an applied voltage of the transformer T1. V2 in (b) is the output voltage of the transformer T1, which is a voltage N2 / N1.V1 proportional to the winding ratio N1: N2 of the transformer T1. V3 in the shaded area in (c)
Is an energy part of the output voltage V2 of the transformer T1 necessary for charging. The hatched portion VSR in (d) is an energy portion unnecessary for charging, which is obtained by subtracting the energy portion required for charging from the output voltage V2 of the transformer T1.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a charging device which can effectively use the energy on the secondary side of a transformer to charge a secondary battery.

[0007]

In order to solve the above-mentioned problems, a charging device of the present invention is a charging device for charging a secondary battery with a constant current, wherein charging is performed by rectifying the secondary side of a transformer for constant current charging. Circuit, a saturable reactor that cuts off the charging current, a reset current supply circuit that supplies the reset current to the saturable reactor, an error amplification circuit that detects the charging current and amplifies the error, and a primary side DC voltage A switching element that performs switching, a control IC that controls the switching element, and a secondary battery voltage measurement circuit that measures the open-circuit voltage of the secondary battery are provided, and normally switching is performed via the control IC by the output signal of the error amplification circuit. The secondary output of the transformer is controlled by controlling the element so that the secondary battery is charged with a constant current. When measuring the open circuit voltage of the secondary battery, Based on a command voltage measurement circuit, it is characterized in that the saturable reactor by supplying a reset current from the reset current supply circuit so as not to flow the charging current by the unsaturated state.

In order to solve the above-mentioned problems, another charging device of the present invention is the charging device, wherein a first constant current control circuit including a control IC and a switching element, and a reset current supply circuit can be used. A control circuit switching switch for switching between a second constant current control circuit composed of a saturation reactor and a second constant current control circuit is provided, and the second constant current control is performed based on a command from the secondary battery voltage measurement circuit issued according to the charging voltage. When the circuit is switched, the saturable reactor is characterized by interrupting and controlling the charging current and securing the power source of the secondary battery voltage measuring circuit.

[0009]

In general, the control IC is controlled by the output signal from the error amplification circuit which detects the charging current and amplifies the error. The control IC controls the secondary side output of the transformer by controlling the switching element that switches the primary side DC voltage to charge the secondary battery with a constant current. When measuring the open circuit voltage of the secondary battery, a reset current is supplied from the reset current supply circuit to the saturable reactor based on a command from the secondary battery voltage measurement circuit. With the maximum reset current, the saturable reactor is put into an unsaturated state so that the charging current does not flow, and the open circuit voltage of the secondary battery is measured. If the charging voltage is low,
Since the saturable reactor PWM-controls the secondary side output pulse to charge the secondary battery with a constant current, the power supply voltage of the secondary battery voltage measuring circuit can be secured.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIG. In the figure, 3 is a saturable reactor, which interrupts the secondary side output by a reset current from a reset current supply circuit 6 described later. The reset current supply circuit 6 is a circuit that supplies a reset current to the saturable reactor 3,
Transistor Q1, resistors R2, R3, R4 diode D
It is composed of 6. Due to the base current of the transistor Q1, the controlled reset current flows in the order of emitter → collector → diode D6 → saturable reactor of the transistor Q1. The error amplification circuit is composed of a detection resistor R1, a reference voltage E, and an error amplifier 4, and outputs an output signal to the control IC 7 via the photocoupler 8 to control I
C7 controls the switching element SW1 that switches the primary side voltage to control the secondary side output. The secondary battery voltage measuring circuit 5 operates with the DC voltage Vcc converted into DC by the rectifying diode D4 and the smoothing capacitor C3 on the tertiary winding side of the transformer T1. The voltage measurement point of the secondary battery 2 is point a in the figure.

A rectifier diode D converts the alternating current from the AC power source 1.
1. DC is converted by the smoothing capacitor C1. The DC voltage is pulsed by the switching element SW1 at the frequency and pulse width set by the control IC 7, and is transmitted to the secondary side via the transformer T1. On the secondary side, this waveform is converted into a direct current by the rectifying diode D2, the commutation diode D3, the choke CH, and the smoothing capacitor C2, and the secondary battery 2 is charged. This charging current is detected by the detection resistor R1, the error from the reference voltage E is amplified by the error amplifier 4, this output signal is fed back to the control IC 7 by the photocoupler 8, and the control IC 7 switches the primary side voltage. The switching element SW1 is controlled to control the secondary side output. At this time, the reset current is not passed through the saturable reactor 3 by keeping the switch SW2 in the OFF state. Therefore, the saturable reactor 3 is in a saturated state. That is, the circuit configuration is in the same state as the forward converter, and only the necessary energy is transmitted from the primary side to the secondary side.

Next, the open circuit voltage of the secondary battery 2 is measured by the transistor Q at a cycle determined by the secondary battery voltage measuring circuit 5.
This is performed by turning on / off the switch SW2 between the resistor R3 connected to the base of No. 1 and the ground. Switch S
When W2 is turned on, the maximum reset current flows through the saturable reactor 3, the saturable reactor 3 becomes unsaturated, and the charging current is cut off. The open circuit voltage of the secondary battery 2 is read by the secondary battery voltage measuring circuit 5 in accordance with the ON timing of the switch SW2. When the reading of the open circuit voltage of the secondary battery 2 is completed, the switch SW2 is turned off again by the secondary battery voltage measuring circuit 5 to charge the secondary battery 2. Therefore, the supply voltage Vcc of the secondary battery voltage measuring circuit 5 is stable without fluctuation.

Next, a second embodiment of the present invention will be described with reference to FIG. By adding the control circuit switching switch SW3 for switching the constant current control circuit to the circuit of the first embodiment, the secondary battery voltage measuring circuit can be used even when the low charging voltage, that is, the primary-side on-duty becomes extremely small. It is possible to supply a stable power supply voltage Vcc to the power supply circuit 5. As a result, even when the short-circuited secondary battery 2 is connected to the charger, the secondary battery voltage measuring circuit 5 can be operated, so that the charger can be controlled.

To explain the operation, the constant current control circuit is switched according to the charging voltage. When the charging voltage is large (when the on-duty has a width capable of supplying a stable power supply voltage to the secondary battery voltage measuring circuit), the control circuit switching switch SW3 is turned on so as to perform PWM control on the primary side.
The circuit configuration at this time is the same as in FIG. Next, when the charging voltage is small (when the on-duty is within a range in which a stable power supply voltage cannot be supplied to the secondary battery voltage measurement circuit), the secondary circuit PWM control by the saturable reactor 3 is performed to switch the control circuit. Turn on the switch SW3. As a result, it becomes possible to secure the power supply voltage Vcc sufficient to operate the secondary battery voltage measuring circuit 5.

[0015]

As described above, the charging device of the present invention has a charging circuit for rectifying the secondary side of a transformer for constant current charging, a saturable reactor for interrupting the charging current, and a saturable reactor for resetting. A reset current supply circuit that supplies a current, an error amplification circuit that detects a charging current and amplifies the error, a switching element that switches the primary side DC voltage, and a control IC that controls the switching element
And a secondary battery voltage measuring circuit for measuring the open circuit voltage of the secondary battery. Normally, the secondary side output of the transformer is controlled by controlling the switching element via the control IC by the output signal of the error amplification circuit. When the rechargeable battery is controlled to be charged with a constant current and the open-circuit voltage of the rechargeable battery is measured, the reset current is supplied from the reset current supply circuit based on the command from the rechargeable battery voltage measurement circuit to make it saturable. Since the charging current is prevented from flowing by setting the reactor into an unsaturated state, the charging device according to the present invention is provided with a control IC and a switching element in the charging device. A control circuit switching switch for switching between the constant current control circuit 1 and the second constant current control circuit including the reset current supply circuit and the saturable reactor is provided. When switching to the second constant current control circuit based on a command from the secondary battery voltage measurement circuit that is issued according to the electric voltage, the saturable reactor cuts off and controls the charging current, and at the same time, the secondary battery Since the power supply for the voltage measurement circuit is secured, the charging current is cut off using a saturable reactor, and constant current charging is controlled on the primary side,
We try not to send unnecessary energy to the secondary side.
This can prevent unnecessary energy from being lost to the saturable reactor. Further, when the charging voltage is low, the secondary side PWM control by the saturable reactor is performed, whereby it is possible to secure a power supply voltage sufficient to operate the secondary battery voltage measurement circuit.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a charging device according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram of a charging device according to a second embodiment of the present invention.

FIG. 3 is a circuit diagram of a charging device in a conventional example.

FIG. 4 is a diagram showing waveforms at various points in the circuit diagram of FIG.

[Explanation of symbols]

C1 to C3 capacitor CH output choke D1 to D6 diode E reference voltage Q1 transistor R1 to R4 resistance SW1 to SW3 switch T1 transformer V1 T1 applied voltage V2 T1 output voltage V3 energy required for charging VSR energy not required for charging (saturable reactor) Waveform on both ends) Vcc Power supply for secondary battery voltage measurement circuit 1 AC power supply 2 Secondary battery 3 Saturable reactor 4 Error amplifier 5 Secondary battery voltage measurement circuit 6 Reset current supply circuit 7 Control IC 8 Photo coupler

Claims (2)

[Claims] 1. A charging device for charging a secondary battery with constant current, a charging circuit for rectifying the secondary side of a transformer for constant current charging, a saturable reactor for interrupting charging current, and resetting to saturable reactor. A reset current supply circuit that supplies a current, an error amplification circuit that detects a charging current and amplifies the error, a switching element that switches the primary side DC voltage, a control IC that controls the switching element, and a secondary battery And a secondary battery voltage measuring circuit for measuring the open circuit voltage of the transformer. Normally, the secondary side output of the transformer is controlled by controlling the switching element via the control IC by the output signal of the error amplifying circuit. When the rechargeable battery is charged with a constant current and the open circuit voltage of the rechargeable battery is measured, the reset current supply circuit must A charging device characterized in that a charging current is prevented from flowing by supplying a reset current to an unsaturated state of a saturable reactor. 2. A first constant current control circuit including the control IC and the switching element, and a second constant current control circuit including the reset current supply circuit and the saturable reactor.
When a switch for switching the control circuit for switching between the constant current control circuit and the constant current control circuit is provided, and the switch is switched to the second constant current control circuit based on a command from the secondary battery voltage measurement circuit issued according to the charging voltage, The charging device according to claim 1, wherein the saturable reactor cuts off and controls a charging current and secures a power source for a secondary battery voltage measuring circuit.