JP2767185B2 - Battery charge / discharge circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery charge / discharge circuit in which a normal operating voltage (input voltage of a charging circuit) is close to a voltage at the time of backup by a battery. The present invention relates to a battery charge / discharge circuit that can be charged without using a battery.

[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, indicate resistors, respectively.

During charging, a DC voltage from another device is applied between the + input / output terminal and the − input / output terminal, * ON is high impedance, the transistor Q2 is off, and the transistor Q3 is off. Under this state, the capacitor C2 is charged by the current output from the step-up / step-down converter 10, the current flows from the capacitor C2 to the battery E via the diode D2, and the battery E is charged. When 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 is turned on, a current flows through a closed loop of the battery E → the diode D3 → the load (not shown) → the transistor Q3 → the 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 amplifier circuit,
Reference numeral 7 denotes a photocoupler, C1 denotes a capacitor, D1 denotes a diode, Q1 denotes a transistor, and T denotes a transformer. The same reference numerals as those in FIG. 7 indicate the same components.

[0005] The upper end of the primary winding of the transformer T is connected to the + input / output terminal by a wire, 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 a negative input / output terminal via a line. The control circuit 3 supplies an on / off signal to the base of the transistor Q1, and adjusts the on / off time of the transistor Q1 according to a control signal sent from the error amplifier circuit 4 via the photocoupler 7. Control.

[0006] 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 amplifier circuit 4
It amplifies the difference between the voltage of the capacitor C2 and the set voltage value. 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 has been necessary to use a buck-boost converter as the charging circuit. In addition, 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. The present invention has been made in view of this point, and has an N-channel type M as a discharge switch.
It is an object of the present invention to provide a battery charge / discharge circuit that can use an OSFET transistor and that can be charged to an arbitrary charge voltage without using an insulating buck-boost converter.

[0008]

FIG. 1 is a diagram illustrating the principle of the present invention. The battery charging / discharging circuit according to claim 1, wherein the + input / output terminal, the − input / output terminal, the coil (L1) having a lower end connected to the − input / output terminal, one end connected to the + input / output terminal, and the other end connected to the + input / output terminal. Switching means (Q connected to the upper end of the coil (L1)
1) and control circuit to turn on / off the switching means (Q1)
(3) a negative voltage converter (20) having
The capacitor (C2) connected to the lower end of (L1) and the capacitor
A first diode (D1) disposed between the lower end of (C2) and the upper end of the coil (L1) and capable of flowing a current from the lower end of the capacitor (C2) toward the upper end of the coil (L1); ,-Battery (E) connected to the lower end of the capacitor (C2),
A second diode (C) disposed between the upper end of the capacitor (C2) and the + side of the battery (E) and capable of flowing current from the upper end of the capacitor (C2) toward the + side of the battery (E); D2) and a third diode disposed between the + side and the + input / output terminal of the battery (E) and capable of flowing a current from the + side of the battery (E) to the + input / output terminal.
(D3), a discharge N whose source is connected to the anode of the first diode (D1) and whose drain is connected to the -I / O terminal.
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).

The battery charging / discharging circuit according to claim 2 is the battery charging / discharging circuit according to claim 1, wherein the capacitor (C2)
A voltage error output circuit (4) that outputs a difference between the voltage between both ends and the voltage set value, and the control circuit (3) is a voltage error output circuit (4).
The on / off control of the switching means (Q1) is controlled with reference to the output of (1).

According to a third aspect of the present invention, in the battery charging / discharging circuit according to the first or second aspect,
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) turning on / off the switching means (Q1) by referring to an output of the current error output circuit. It is characterized by controlling.

According to a fourth aspect of the present invention, there is provided a battery charging / discharging circuit according to the first, second, or third aspect, wherein the value of the ON instruction signal (* ON) is set to a discharging N-channel MOSFET transistor (Q3 ), The control circuit (3) turns off the switching means (Q1).

[0012]

The operation of the battery charging / discharging circuit according to 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 capacitor C2 is charged by the energy stored in the coil L1, 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 no DC voltage is applied from another device between the + input / output terminal and the −input / output terminal, and that the MOSFET transistor Q3 is on. Under this condition, battery E → diode D3 → load (not shown)
→ Transistor Q3 → Current flows through the closed loop of battery E.

The operation of the battery charging / discharging circuits according to the second and third aspects will be described. Voltage error output circuit 4
Outputs the difference between the voltage of the capacitor C2 and the voltage set value. The control circuit 3 refers to this error and refers to the capacitor C
Switching means Q so that the voltage of
1 is turned on / off. On / off of the switching means Q1 can be controlled so that the current flowing into the battery E becomes 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. When the ON instruction signal * ON enters a predetermined state, the control circuit 3 turns the switching means Q1 OFF.

[0015]

FIG. 2 is a diagram showing an 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 negative input / output terminal is connected to the positive output of the negative voltage converter 20 via a line. The negative output of the negative voltage converter 20 is connected to the cathode of a diode D1, and the anode of the diode D1 is connected to a MOSFET transistor Q1.
3 sources. 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 resistors R1 and R2 are connected in series.
Is connected to the + input / output terminal, * ON is applied to the lower end of the resistor R2, and the junction of the resistors R1 and R2 is connected to the base of the transistor Q2. Transistor Q2
Is connected to the + input / output terminal, and the transistor Q
2 is connected to the upper end of a resistor R3.
The lower end is connected to the gate of the transistor Q3. The lower end of the resistor R3 is connected to the resistor R4, 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 + I / O terminal and the -I / O terminal and the transistor Q3 is off, the current from the negative voltage converter 20 passes through the capacitor C2 and the diode D1. To charge the capacitor C2. When the voltage of the capacitor C2 is higher than the voltage of the battery E, a current flows through a 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 is turned on, a current flows through a closed loop of the battery E → the diode D3 → the load (not shown) → the transistor Q3 → the 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 amplifier circuit, 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 indicate resistors, 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 from 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 amplification circuit 4
Amplifies the difference between the voltage of the capacitor C2 and the voltage set 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 a control signal from the error amplifier circuit 4.

When the transistor Q1 is turned on, a current flows through the path of the + 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, a current flows through a closed loop of the coil L1, the capacitor C2, the diode D1, and the coil L1 due to the energy stored in the coil L1, and the capacitor C2 is charged. When the voltage of the capacitor C2 is higher than the voltage of the battery E, a current flows through a closed loop of the capacitor C2 → the diode D2 → the battery E → the capacitor C2, and the battery E is charged.

The operation of the embodiment shown in FIG. 3 will be described. When a voltage V0 is applied between the + input / output terminal and the − input / output terminal while * ON is in a high impedance state, a voltage is applied to the coil L1 by the switching transistor Q1. When the transistor Q1 is turned off, a current flows through a path from 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 voltage of the capacitor C2 is obtained.
Is stabilized at the voltage set 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 lower than the voltage determined by the error amplifier circuit 4 and the control circuit 3,
Battery charging is performed by the current limitation determined by the control circuit 3, and the battery voltage is maintained at a stable voltage when the battery voltage increased with charging reaches a predetermined voltage. For example, such control is performed for a battery that is recommended to be charged at a constant voltage, such as a lead acid storage battery or a Li secondary battery, and has an upper limit of the charging current.

In order to discharge the battery E,
* Turn ON low. * When ON goes low,
The transistor Q2 is turned on, and the N-channel MOSFE
The T transistor Q3 is also turned on. At this time, if the transistor Q1 repeats on / off, the coil L1
Lower end → transistor Q3 → diode D1 → coil L
1 is formed, and an overcurrent flows through the closed loop. In order to prevent the occurrence of such an overcurrent, the control circuit 3 may be provided with a current limiting function. When * ON is at a low level, the control circuit 3 is stopped.
The transistor Q1 can be kept off.

FIG. 4 is a diagram showing the charging current / voltage characteristics of the embodiment of FIG. A battery generally has a maximum allowable charging current, and if the battery is charged with a charging current exceeding that value, the battery may be damaged due to a rise in temperature or the like, and the life of the battery may be deteriorated. This is avoided by limiting the current by the control circuit 3.

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 reduced life if charged beyond a specified voltage. If the voltage is lower than the voltage, the battery may be insufficiently charged.

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 also denotes a transistor, and R1 to R12 denote 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 comprising a capacitor C4 and a resistor R7 is connected to the base of the transistor Q1.
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, the lower end of the resistor R12 is connected to the coil L1.
Is connected to the lower end. 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 lower end of the capacitor C3 is also connected to the upper end of the resistor R10, 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.

The resistors R5 and R6 are connected to both ends of the capacitor C2.
Are connected, 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
431 can be constituted. The comparison circuit 4 calculates the difference between the voltage at the junction of the resistors R5 and R6 and the voltage set value, and outputs the difference.

When a DC voltage is applied from another device between the + input / output terminal and the −input / output terminal while * ON is in a high impedance state, a current flows to the base of the transistor Q1 and the transistor Q1 is turned on. I do. When the transistor Q1 is turned on, a current flows through the coil L1 and the coil L1
1 generates an upward voltage, and the coil L2 also generates an upward voltage. By the upward voltage generated in the coil L2,
The turning on of the transistor Q1 is accelerated. At the same time,
The capacitor C3 is also charged.

When the voltage of the capacitor C3 becomes higher than the threshold, the transistor Q4 turns on and the transistor Q1 turns off. When the transistor Q1 is turned off, the coil L
1 generates a downward voltage, and also generates a downward voltage in the coil L2. The capacitor C2 is charged by the downward voltage generated in the coil L1. Also, the coil L
2 causes the capacitor C3 to be charged in the opposite direction, thereby turning off the 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
Maintain the off state.

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 R13.
Reference numeral 18 indicates a resistor, and ZD indicates a Zener diode. The same reference numerals as those in FIG. 5 indicate the same components.

In the embodiment shown in FIG. 6, the battery is charged at a constant current. Constant current charging is recommended for NiCd batteries and NiMH batteries. Resistance R
The upper end of the resistor 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. The cathode and resistance R of the Zener diode ZD
17, a series circuit of resistors R13 and R14 is connected. 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
The voltage at the junction 6 is input to the negative input terminal of the comparison circuit 6. The voltage at the junction of the resistors R15 and R16 corresponds to the current set value. The output of the comparison circuit 6 represents an error between the charging current value for the battery E and the current set value. The on / off time of the transistor Q1 is controlled by the current error.

When a DC voltage is applied between the + input / output terminal and the −input / output terminal while * ON is in a high impedance state, the transistor Q1 is turned on / off and the capacitor C2 is charged. You. The difference between the value of the current flowing into the battery E from the capacitor C2 and the current set value is output from the comparison circuit 6, and the difference is used as the value of the capacitor C
2 are controlled.

[0043]

As is clear from the above description, according to the present invention, it is not necessary to use an insulated type buck-boost converter, so that the number of winding circuits of the inductance component is small and it can be realized at low cost. By being able to be configured as a non-insulated 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 the battery is not charged via the transformer, the conversion efficiency can be increased, the power consumption and heat generation required for charging can be reduced, and the size can be reduced. And other remarkable effects. It is obvious that the charging voltage correction and the charging current correction can be performed depending on the temperature. Further, the constant voltage control and the constant current control can be performed simultaneously.

[Brief description of the 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 charging current / voltage characteristics 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 amplifier circuit C1 and C2 Capacitor D1 to D3 Diode E Battery L1 Coil R1 to R4 Resistance Q1 and Q2 transistor Q3 N-channel MOSFET transistor

Claims (4)

(57) [Claims] 1. A coil (L1) having a + input / output terminal, a − input / output terminal, a lower end connected to the − input / output terminal, and one end connected to the + input / output terminal and the other end connected to the 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 and off a capacitor (C2) having an upper end connected to a lower end of the coil (L1)
A first diode (C) disposed between the lower end of the capacitor (C2) and the upper end of the coil (L1) and capable of flowing a current from the lower end of the capacitor (C2) toward the upper end of the coil (L1). D1)
And the battery connected on the negative side to the lower end of the capacitor (C2)
(E) and between the upper end of the capacitor (C2) and the + side of the battery (E), and allow current to flow from the upper end of the capacitor (C2) toward the + side of the battery (E). The second diode (D2) is disposed between the + side and the + input / output terminal of the battery (E), and allows 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) having a source connected to the anode of the first diode (D1) and a drain connected to the -input / output terminal; ON) N channel M for discharge according to the value of
A discharge control circuit (8) for controlling ON / OFF of the OSFET transistor (Q3). 2. A voltage error output circuit (4) for outputting a difference between a voltage between both ends of a capacitor (C2) and a voltage set value, wherein a control circuit (3) refers to an output of the voltage error output circuit (4). 2. The battery charging / discharging circuit according to claim 1, wherein the switching means controls the on / off of the switching means. A current error output circuit for outputting an error between a current flowing into the battery (E) and a current set value, wherein the control circuit (3) refers to an output of the current error output circuit and switches the switching means (Q1). 3. The battery charging / discharging circuit according to claim 1, wherein 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 turning on of the discharging N-channel MOSFET transistor (Q3). The battery charging / discharging circuit according to claim 1, 2 or 3.