JPH077859A - Battery charging and discharging circuit - Google Patents

Abstract

PURPOSE:To provide a battery charging and discharging circuit which permits the use of an N-channel MOSFET transistor as a discharge switch and makes chargeable for an arbitrary charging voltage without using an insulation type step-up and step-down converter. CONSTITUTION:Assume that an external voltage be applied between + input & output terminal and-input & output terminal and a transistor Q3 be off. If a transistor Q1 turns on under that condition, energy is stored in a coil L1. If the transistor Q turns off, a capacitor C2 is charged by the energy stored in the coil L1 and a battery E is also charged. The control is possible in such a manner that the voltage of the capacitor C2 becomes constant and also a current flowing into the battery becomes constant. When the signal *ON is in a low level state, the transistor Q3 maintains ON state, a control circuit 3 stops its operation and the transistor Q1 maintains OFF state.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an insulation type step-up / down converter for an arbitrary charging voltage in a battery charging / discharging circuit in which the normal operating voltage (input voltage of the charging circuit) and the voltage at the time of backup by the battery are close. The present invention relates to a battery charging / discharging circuit that can be charged without using.

[0002]

2. Description of the Related Art FIG. 7 is a diagram showing a conventional example of a battery charge / discharge circuit. In the figure, 10 is a buck-boost converter (insulation type), C2 is a capacitor, D2 and D3 are diodes, E is a battery, Q2 is a transistor, and Q3 is an MO.
The SFET transistors R1 to R4 represent resistors, respectively.

During charging, a DC voltage from another device is applied between the + input / output terminal and the − input / output terminal, * ON has a high impedance, the transistor Q2 is off, and the transistor Q3 is also off. Under this state, the capacitor C2 is charged by the current output from the buck-boost converter 10, and the current flows from the capacitor C2 to the battery E via the diode D2, and the battery E is charged. If the DC voltage from another device is turned off,
* ON is set to low level, transistor Q2 turns on,
The transistor Q3 also turns on. When the transistor Q3 turns on, a current flows in a closed loop of the battery E → diode D3 → load (not shown) → transistor Q3 → battery E.

FIG. 8 is a diagram showing details of the conventional example of FIG. In the figure, 3 is a control circuit, 4 is an error amplification circuit,
7 is a photo coupler, C1 is a capacitor, D1 is a diode, Q1 is a transistor, and T is a transformer. The same reference numerals as in FIG. 7 indicate the same items.

The upper end of the primary winding of the transformer T is connected by a wire to the + input / output terminal, and the lower end of the primary winding is connected to the collector of the transistor Q1. The emitter of the transistor Q1 is connected to the-input / output terminal via the line. The control circuit 3 supplies an ON / OFF signal to the base of the transistor Q1, and controls the ON / OFF time of the transistor Q1 according to the control signal sent from the error amplification circuit 4 via the photo coupler 7. Control.

The upper end of the secondary winding of the transformer T is a diode D
1 and the cathode of the diode D1 is connected to the upper end of the capacitor C2 and the anode of the diode D2. The lower end of the secondary winding of the transformer T is connected to the lower end of the capacitor C2. The error amplification circuit 4 is
The difference between the voltage of the capacitor C2 and the voltage setting value is amplified. The output of the error amplification circuit 4 is sent to the control circuit 3 via the photo coupler 7.

[0007]

Conventionally, when the initial charging voltage is lower than the input voltage of the charging circuit and the voltage at the end of charging is higher than the input voltage of the charging circuit, it is necessary to use a buck-boost converter as the charging circuit. Further, when a power MOSFET transistor is used as a battery discharge switch, if an N-channel type, which is advantageous for ON resistance, is used, the GND level is different, so it is necessary to design it as an insulating type. The present invention was created in view of this point, and an N-channel M-type discharge switch is used.
An object of the present invention is to provide a battery charging / discharging circuit which can use an OSFET transistor and can be charged to an arbitrary charging voltage without using an insulating type buck-boost converter.

[0008]

FIG. 1 is a diagram for explaining the principle of the present invention. The battery charge / discharge circuit according to claim 1 has a + input / output terminal, a − input / output terminal, a coil (L1) whose lower end is connected to the − input / output terminal, and one end connected to the + input / output terminal and the other end. Switching means (Q
1) and a control circuit that turns on / off the switching means (Q1)
A negative voltage converter (20) having (3) and a coil at the upper end
The capacitor (C2) connected to the lower end of (L1)
A first diode (D1) which is arranged between the lower end of (C2) and the upper end of the coil (L1) and allows a current to flow from the lower end of the capacitor (C2) to the upper end of the coil (L1); , -Side is the battery (E) connected to the lower end of the capacitor (C2),
A second diode (which is placed between the upper end of the capacitor (C2) and the + side of the battery (E) and allows a current to flow from the upper end of the capacitor (C2) toward the + side of the battery (E) ( D2) and a third diode that is arranged between the + side and + input / output terminal of the battery (E) and that allows a current to flow from the + side of the battery (E) to the + input / output terminal.
(D3) and the source is connected to the anode of the first diode (D1) and the drain is connected to the-input / output terminal for discharging N
Channel MOSFET transistor (Q3) and N-channel MOSFET for discharging according to the value of ON instruction signal (* ON)
Discharge control circuit that controls on / off of transistor (Q3)
(8) is provided.

A battery charging / discharging circuit according to a second aspect is the battery charging / discharging circuit according to the first aspect, in which a capacitor (C2) is provided.
It has a voltage error output circuit (4) that outputs the difference between the voltage across both ends and the voltage setting value, and the control circuit (3) has a voltage error output circuit (4).
The ON / OFF of the switching means (Q1) is controlled by referring to the output of the above.

A battery charging / discharging circuit according to claim 3 is the battery charging / discharging circuit according to claim 1 or 2.
It is equipped with a current error output circuit that outputs the error between the current flowing into the battery (E) and the current setting value, and the control circuit (3) refers to the output of the current error output circuit to turn on / off the switching means (Q1). It is characterized by controlling.

A battery charging / discharging circuit according to claim 4 is the battery charging / discharging circuit according to claim 1, 2 or 3, wherein the value of the ON instruction signal (* ON) is an N-channel MOSFET transistor (Q3) for discharging. ) Is instructed to be turned on, the control circuit (3) turns off the switching means (Q1).

[0012]

The operation of the battery charge / discharge circuit of claim 1 will be described. It is assumed that a DC voltage from another device is applied between the + input / output terminal and the − input / output terminal, and the MOSFET transistor Q3 is off. Under this state, when the switching means Q1 is turned on, a current flows through the coil L1 and energy is accumulated in the coil L1. When the switching means Q1 is turned off, the energy stored in the coil L1 charges the capacitor C2, and when the voltage of the battery E is lower than the voltage of the capacitor C2, the battery E is charged. It is assumed that the DC voltage from another device is not applied between the + input / output terminal and the − input / output terminal, and the MOSFET transistor Q3 is on. Under this condition, battery E → diode D3 → load (not shown)
→ Transistor Q3 → Current flows in the closed loop of battery E.

The operation of the battery charging / discharging circuit of claims 2 and 3 will be described. Voltage error output circuit 4
Outputs the difference between the voltage of the capacitor C2 and the voltage setting value. The control circuit 3 refers to this error and refers to the capacitor C
The switching means Q so that the voltage of 2 becomes the voltage setting value.
Controls on / off of 1. It is also possible to control on / off of the switching means Q1 so that the current flowing into the battery E has a constant value.

The operation of the battery charge / discharge circuit of claim 4 will be described. When the ON instruction signal * ON becomes a predetermined state (for example, low level), the transistor Q3 turns on. The control circuit 3 turns off the switching means Q1 when the on instruction signal * ON enters a predetermined state.

[0015]

FIG. 2 is a diagram showing the outline of the present invention. In the figure, 20 is a negative voltage converter, C2 is a capacitor,
D1 to D3 are diodes, E is a battery, Q2 is a transistor, Q3 is an N-channel MOSFET transistor, and R1 to R4 are resistors.

-The input / output terminals are at 0 potential (GND),
The-input / output terminal is connected to the + side output of the negative voltage converter 20 via a wire. The cathode of the diode D1 is connected to the negative output of the negative voltage converter 20, and the anode of the diode D1 is the MOSFET transistor Q.
3 connected to the source. The drain of the MOSFET transistor Q3 is connected to the-input / output terminal.

The resistors R1 and R2 are connected in series, and the resistor R1
Is connected to the + input / output terminal, * ON is applied to the lower end of the resistor R2, and the junction point of the resistors R1 and R2 is connected to the base of the transistor Q2. Transistor Q2
Of the transistor Q is connected to the + input / output terminal
The upper end of the resistor R3 is connected to the collector of 2 and the resistor R3
The gate of the transistor Q3 is connected to the lower end of the. A resistor R4 is connected to the lower end of the resistor R3, and the lower end of the resistor R4 is connected to the source of the transistor Q3.

The + output of the negative voltage converter 20 is connected to the upper end of the capacitor C2, and the lower end of the capacitor C2 is connected to the anode of the diode D1. The + output of the negative voltage converter 20 is also connected to the anode of the diode D2, the cathode of the diode D2 is connected to the + side of the battery E, and the − side of the battery E is connected to the anode of the diode D1. The cathode of the diode D2 is also connected to the anode of the diode D3, and the cathode of the diode D3 is connected to the + input / output terminal.

When a DC voltage from another device is applied between the + input / output terminal and the −input / output terminal and the transistor Q3 is off, the current from the negative voltage converter 20 passes through the capacitor C2 and the diode D1. And flows to charge the capacitor C2. When the voltage of the capacitor C2 is higher than the voltage of the battery E, current flows in the closed loop of the capacitor C2 → the battery E → the capacitor C2, and the battery E is charged.

When * ON goes low, the transistor Q2 turns on, a high level is applied to the gate of the transistor Q3, and the transistor Q3 turns on. When the transistor Q3 turns on, a current flows in a closed loop of the battery E → diode D3 → load (not shown) → transistor Q3 → battery E.

FIG. 3 is a diagram showing an outline of the first embodiment of the present invention. In the figure, 1 is the upper end of the coil L1, 2 is the lower end of the coil L1, 3 is a control circuit, 4 is an error amplification circuit, and C.
1 and C2 are capacitors, D1 to D3 are diodes,
E is a battery, L1 is a coil, Q1 and Q2 are transistors, Q3 is an N-channel MOSFET transistor,
R1 to R4 represent resistances, respectively.

The emitter of the transistor Q1 is connected to the + input / output terminal via a line, the collector of the transistor Q1 is connected to the upper end of the coil L1, and the base of the transistor Q1 is turned on / off by the control circuit 3. A signal is applied. The lower end of the coil L1 is connected to the upper end of the capacitor C2. The lower end of the capacitor C2 is connected to the anode of the diode D1, and the cathode of the diode D1 is connected to the upper end of the coil L1. Error amplifier circuit 4
Is for amplifying the difference between the voltage of the capacitor C2 and the voltage setting value. The output of the error amplification circuit 4 is sent to the control circuit 3. The control circuit 3 controls the on / off time of the transistor Q1 according to the control signal from the error amplification circuit 4.

When the transistor Q1 is turned on, a current flows through the path of + input / output terminal → transistor Q1 → coil L1 → −input / output terminal, and energy is accumulated in the coil L1. When the transistor Q1 is turned off, the energy stored in the coil L1 causes a current to flow in the closed loop of the coil L1, the capacitor C2, the diode D1, and the coil L1 to charge the capacitor C2. When the voltage of the capacitor C2 is higher than the voltage of the battery E, current flows through the closed loop of the capacitor C2 → diode D2 → battery E → capacitor C2, and the battery E is charged.

The operation of the embodiment shown in FIG. 3 will be described. When the voltage V0 is applied between the + input / output terminal and the −input / output terminal under the condition that * ON is high impedance, the voltage is applied to the coil L1 by the switching transistor Q1. When the transistor Q1 is turned off, a current flows through the path of the upper end of the coil L1, the capacitor C2, the diode D1 and the lower end of the coil L1, and the capacitor C2 is charged.

The error between the voltage setting value and the voltage V1 of the capacitor C2 is obtained by the error amplifying circuit 4, and this voltage error is fed back to the control circuit 3, and the capacitor C2 is fed back.
Voltage V1 is stabilized at the voltage setting value. Capacitor C
Voltage from the second voltage V1 minus the forward voltage V _F of the diode D2 is applied to the battery E, the charging of the battery E is performed.

When the voltage of the battery E is equal to or lower than the voltage determined by the error amplification circuit 4 and the control circuit 3,
The battery is charged by the current limitation determined by the control circuit 3, and is maintained at a stable voltage when the battery voltage increased with charging reaches a predetermined voltage. Such control is performed for a battery for which constant voltage charging is recommended, such as a lead acid storage battery or a Li secondary battery, and the upper limit of the charging current is specified.

When it is desired to discharge the battery E,
* Set ON to low level. * When ON becomes low level,
Transistor Q2 is turned on and N-channel MOSFE
The T transistor Q3 is also turned on. At this time, if the transistor Q1 is repeatedly turned on / off, the coil L1
Bottom end of → transistor Q3 → diode D1 → coil L
A closed loop reaching the upper end of 1 is formed, and an overcurrent flows in this closed loop. In order to prevent the occurrence of such an overcurrent, the control circuit 3 can be provided with a current limiting function, and the control circuit 3 is stopped when * ON is at a low level,
It is also possible to keep the transistor Q1 off.

FIG. 4 is a diagram showing the charging current / voltage characteristics of the embodiment of FIG. The maximum allowable charging current is generally specified for the battery, and if the charging current exceeds the maximum value, the battery may be damaged due to temperature rise or the life may be deteriorated. The current limitation by the control circuit 3 avoids this.

Batteries that are recommended to be charged by constant voltage charging, such as lead acid storage batteries and Li secondary batteries, may be damaged or have a limited life if they are charged above the specified voltage. If the voltage is less than the voltage, the charge may be insufficient, so the voltage is maintained at the voltage determined by the control circuit 4.

FIG. 5 is a diagram showing details of the first embodiment of the present invention. In the figure, 5 is a comparison circuit, C1 to C4.
Is a capacitor, D1 to D6 are diodes, E is a battery, L1 and L2 are coils, Q1 and Q2 are transistors, Q3 is an N-channel MOSFET transistor, Q
4 is a transistor, and R1 to R12 are resistors.

The coil L1 and the coil L2 are wound on the same magnetic core. The emitter of the transistor Q1 is connected to the + input / output terminal, and the collector of the transistor Q1 is connected to the upper end of the coil L1. A parallel circuit including a capacitor C4 and a resistor R7 is connected to the base of the transistor Q1, and the left end of the parallel circuit is the transistor Q4.
Connected to the collector.

The emitter of the transistor Q4 is connected to the + input / output terminal, and the collector of the transistor Q4 has a resistor R.
12 is connected to the upper end, and the lower end of the resistor R12 is connected to the coil L1.
Is attached to the lower end of. The upper end of the capacitor C3 is connected to the + input / output terminal, and the lower end of the capacitor C3 is connected to the base of the transistor Q4.

The upper end of the coil L2 is connected to the + input / output terminal, and the lower end of the coil L2 is connected to the right end of the resistor R8. The left end of the resistor R8 is connected to the cathode of the diode D6, and the anode of the diode D6 is connected to the collector of the transistor Q4. The collector of the transistor Q4 is also connected to the anode of the diode D5, and the cathode of the diode D5 is connected to the emitter of the transistor Q4.

The lower end of the capacitor C3 is connected to the upper end of the resistor R9, and the lower end of the resistor R9 is connected to the right end of the resistor R8. The upper end of the resistor R10 is also connected to the lower end of the capacitor C3, and the lower end of the resistor R10 is connected to the output of the comparison circuit 5. The upper end of the resistor R11 is connected to the + input / output terminal, and the lower end of the resistor R11 is connected to the lower end of the resistor R10. The anode of the diode D4 is also connected to the lower end of the capacitor C3, and the cathode of the diode D4 is connected to * ON.

Resistors R5 and R6 are provided at both ends of the capacitor C2.
Connected in series, and the voltage at the junction of the resistors R5 and R6 is input to the comparison circuit 5. The comparison circuit 5 is, for example, TL.
It can be configured by an IC called 431. The comparison circuit 4 calculates the difference between the voltage at the junction between the resistors R5 and R6 and the voltage setting value, and outputs the difference.

When a direct current voltage from another device is applied between the + input / output terminal and the-input / output terminal under the condition that * ON is high impedance, a current flows through the base of the transistor Q1 and the transistor Q1 is turned on. To do. When the transistor Q1 turns on, a current flows through the coil L1 and the coil L1
An upward voltage is generated at 1 and an upward voltage is also generated at the coil L2. By the upward voltage generated in the coil L2,
The turn-on of the transistor Q1 is accelerated. At the same time,
The capacitor C3 is also charged.

When the voltage of the capacitor C3 exceeds the threshold value, the transistor Q4 turns on and the transistor Q1 turns off. When the transistor Q1 is turned off, the coil L
A downward voltage is generated at 1 and a downward voltage is also generated at the coil L2. The downward voltage generated in the coil L1 charges the capacitor C2. Also, the coil L
The downward voltage appearing at 2 charges capacitor C3 in the opposite direction, which turns off transistor Q4. When the transistor Q4 is turned off, the transistor Q1 is turned on, and the same operation is repeated thereafter.

The base voltage of the transistor Q4 is controlled by the output of the comparison circuit 5. That is, the on time of the transistor Q1 is controlled by the voltage error output from the comparison circuit 5. * When ON goes low, transistor Q4 remains on and transistor Q1
Remains off.

FIG. 6 is a diagram showing details of the second embodiment of the present invention. In the figure, 6 is a comparison circuit, R13 to R
Reference numeral 18 indicates a resistor, and ZD indicates a zener diode. The same reference numerals as those in FIG. 5 indicate the same items.

In the embodiment shown in FIG. 6, the battery is charged with a constant current. Constant current charging is recommended for NiCd batteries and NiMH batteries. Resistance R
The upper end of 18 is connected to the + input / output terminal, the lower end of the resistor R18 is connected to the cathode of the Zener diode ZD, and the anode of the Zener diode ZD is connected to the anode of the diode D2. The right end of the resistor R17 is connected to the anode of the diode D2, and the left end of the resistor R17 is connected to the lower end of the coil L1.

A series circuit of resistors R15 and R16 is connected between the cathode and anode of the Zener diode ZD. Zener diode ZD cathode and resistance R
A series circuit of resistors R13 and R14 is connected between the left ends of 17. The voltage at the junction of the resistors R13 and R14 is input to the + input terminal of the comparison circuit 6, and the resistors R15 and R1 are connected.
The voltage at the junction point of 6 is input to the-input terminal of the comparison circuit 6. The voltage at the junction of the resistors R15 and R16 corresponds to the current setting value. The output of the comparison circuit 6 represents the error between the charging current value for the battery E and the current setting value. This current error controls the on / off time of the transistor Q1.

When a direct current voltage from another device is applied between the + input / output terminal and the-input / output terminal under the condition that * ON is high impedance, the transistor Q1 is turned on / off and the capacitor C2 is charged. It The difference between the value of the current flowing into the battery E from the capacitor C2 and the current setting value is output from the comparison circuit 6, and this difference results in the capacitor C2.
The voltage of 2 is controlled.

[0043]

As is apparent from the above description, according to the present invention, since it is not necessary to use the insulation type buck-boost converter, the number of winding circuits of the inductance component is small and the cost can be realized. By being able to be configured as a non-insulating type, it is not necessary to use an insulating device such as a photocoupler for feedback, and it can be realized at low cost. Since charging is not performed via the transformer, conversion efficiency can be increased, power consumption and heat generation required for charging can be suppressed to be small, and size can be reduced. And so on. It is obvious that the charge voltage and the charge current can be corrected depending on the temperature. It is also possible to carry out the constant voltage control and the constant current control at the same time.

[Brief description of drawings]

FIG. 1 is a diagram illustrating the principle of the present invention.

FIG. 2 is a diagram showing an outline of the present invention.

FIG. 3 is a diagram showing an outline of a first embodiment of the present invention.

FIG. 4 is a diagram showing a charging current / voltage characteristic of the embodiment of FIG.

FIG. 5 is a diagram showing details of the first embodiment of the present invention.

FIG. 6 is a diagram showing details of a second embodiment of the present invention.

FIG. 7 is a diagram showing an outline of a conventional example.

FIG. 8 is a diagram showing details of a conventional example.

[Explanation of symbols]

1 Upper end of coil L1 2 Lower end of coil L1 3 Control circuit 4 Error amplification circuit C1 and C2 Capacitor D1 to D3 Diode E Battery L1 Coil R1 to R4 Resistor Q1 and Q2 Transistor Q3 N channel MOSFET transistor

Claims (4)

[Claims] 1. A + input / output terminal, a − input / output terminal, a coil (L1) having a lower end connected to the − input / output terminal, and one end connected to the + input / output terminal and the other end having a coil (L1). Switching means (Q1) connected to the upper end and switching means (Q1)
A negative voltage converter (20) having a control circuit (3) for turning on / off a capacitor, and a capacitor (C2) whose upper end is connected to the lower end of the coil (L1)
And a first diode (which is arranged between the lower end of the capacitor (C2) and the upper end of the coil (L1) and allows a current to flow from the lower end of the capacitor (C2) toward the upper end of the coil (L1) ( D1)
A battery with the negative side connected to the bottom of the capacitor (C2).
(E) is placed between the upper end of the capacitor (C2) and the + side of the battery (E), and it is possible to flow current from the upper end of the capacitor (C2) toward the + side of the battery (E). It is arranged between the second diode (D2) and the + side of the battery (E) and the + input / output terminal, and allows a current to flow from the + side of the battery (E) to the + input / output terminal. A third diode (D3), a discharge N-channel MOSFET transistor (Q3) whose source is connected to the anode of the first diode (D1) and whose drain is connected to the-I / O terminal, and an ON instruction signal (* N channel M for discharge according to the value of (ON)
A battery charge / discharge circuit, comprising: a discharge control circuit (8) for controlling on / off of an OSFET transistor (Q3). 2. A voltage error output circuit (4) for outputting the difference between the voltage across the capacitor (C2) and the voltage setting value is provided, and the control circuit (3) refers to the output of the voltage error output circuit (4). The battery charging / discharging circuit according to claim 1, wherein the switching means (Q1) is controlled to be turned on / off. 3. A current error output circuit for outputting an error between a current flowing into the battery (E) and a current set value, and a control circuit (3) refers to an output of the current error output circuit to perform switching means (Q1). 3. The battery charging / discharging circuit according to claim 1, wherein the on / off of the battery is controlled. 4. The control circuit (3) turns off the switching means (Q1) when the value of the ON instruction signal (* ON) indicates the ON state of the discharging N-channel MOSFET transistor (Q3). The battery charging / discharging circuit according to claim 1, 2, or 3.