JPH07123714A - Power unit having charging function - Google Patents

Abstract

PURPOSE:To provide an inexpensive power unit which has a charging function and can secure sufficiently high output voltage accuracy and charge current accuracy. CONSTITUTION:When power supply is turned on, the voltage led out from the secondary winding NS of a transformer T is rectified and smoothed by means of a diode D10 and a capacitor C9 and an output voltage V0 is outputted. When the voltage V0 is outputted, the voltage V0 is made constant by controlling the current flowing to a transistor Q1 and making the voltage at a capacitor C8 constant. When a battery is connected to output terminals P3 and P4, the primary-side frequency becomes lower and a frequency-to-voltage converting circuit constituted of resistors R14 and R15 and capacitors C4 and C5 converts the frequency into a voltage. An operational amplifier A1 compares the voltage with a reference voltage and, when the voltage is higher than the reference voltage, the output of the amplifier A1 turns off transistors Q5 and Q2. Thus the current control is switched to constant-current control.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device with a charging function that can be used not only as a power supply for electronic equipment but also as a charger.

[0002]

2. Description of the Related Art As shown in FIG. 2, a conventional power supply device with a charging function includes a rectifier circuit 21 for rectifying a commercial power supply, a primary winding N _P , a secondary winding N _S and a control winding N _b. Having a transformer 22, a primary winding N _P , a control winding, and a drive circuit 23
, An oscillating circuit 25 including a transistor 24, a rectifying / smoothing circuit 26 including a diode D and a capacitor C and connected to the secondary winding N _S , and an output current detection resistor 27.
An output terminal unit 28 having a mechanism switch for switching between a charging function and a power supply function, a mode switching unit 29, a constant voltage circuit, a constant current circuit 30, and a signal corresponding to the selection of the charging function or the power supply function. Drive circuit 2 from the secondary side to the primary side
A photo coupler 31 that feeds back to 3 is provided. In this device, when a battery is loaded as a load, the mechanical switch is turned on by mounting the battery, and the ON signal of this switch causes the mode switching unit 29, the constant voltage, and the constant current circuit 3 to operate.
0, the drive circuit 23 is controlled via the photo coupler 31 so that a predetermined constant current output suitable for charging can be obtained.

[0003]

Since the above-mentioned conventional power supply device with a charging function switches the charging function and the power supply function by the mechanical switch on the secondary side, in addition to the mechanical switch, a photo coupler, There is a problem that the device is complicated and expensive because it requires an output detection resistor and the like. This invention
It was made paying attention to the above problems, it is cheap,
It is an object of the present invention to provide a power supply device with a charging function that can sufficiently secure output voltage accuracy and charging current accuracy.

[0004]

A power supply device with a charging function according to the present invention includes a transformer having a primary winding, a secondary winding and a control winding, and the primary winding and the control winding. An oscillating circuit that oscillates at a frequency corresponding to the load output, and a first rectifying / smoothing circuit that rectifies and smoothes the signal derived to the secondary winding and outputs DC power from an output terminal. Rectifying the voltage at one end of the control winding.
A second rectifying / smoothing circuit for smoothing and a constant voltage control circuit for controlling the output voltage of the second rectifying / smoothing circuit to have a constant value when the load of the output terminal is a load other than a battery. And a frequency / voltage conversion circuit that receives a signal from the oscillation circuit and converts it into a voltage corresponding to an oscillation frequency, and compares the output voltage of the frequency / voltage conversion circuit with a predetermined reference voltage to perform the frequency / voltage conversion. When the output voltage of the circuit is high, a comparator that outputs a signal of a first level different from that when it is low and a current flowing through the load in response to the change of the output of the comparator to the signal of the first level And a constant current control circuit for controlling the constant current.

In this power supply device with a charging function, when the power is turned on, the voltage led to the secondary winding of the transformer is converted into a DC voltage by the rectifying / smoothing circuit, and the constant voltage control circuit on the primary side is supplied. Under the control of, a constant power supply voltage is output from the output terminal. When a battery is connected to the output terminal, the frequency of the oscillation circuit changes according to the load output, and the output of the frequency / voltage conversion circuit exceeds the reference voltage, which causes the output of the comparator to change. With the current control circuit,
It is automatically switched so that a proper charging current flows through the load, that is, the battery.

[0006]

The present invention will be described in more detail with reference to the following examples.
Explained. FIG. 1 is a battery charger showing an embodiment of the present invention.
It is a circuit diagram of a power supply device with a function. In FIG. 1, the input terminal P
₁, P₂Is a terminal for inputting the input voltage VI.
Output terminal P₃, P_FourIs the terminal for connecting the load
Is. When used, output terminal P ₃, P_FourHas a battery
Or electronic device is connected.

The transformer T has a primary winding N_PAnd secondary winding
N_SAnd control winding N_BIt has and. Primary winding N_Pof
Input terminal P at one end₁, And the other end is of NPN type.
Langista Q₁Connected to the collector. Primary winding
N_PEnd of transistor Q and transistor Q ₁Resistance R between the bases of₁But
Connected, transistor Q₁Emitter and input terminal P ₂
Resistance R between (reference line of power supply)₂Are connected.
Also transistor Q₁Between the base and emitter of
De D₁Are connected.

The emitter of the transistor Q ₁ is connected to the collector of an NPN type transistor Q ₂ via resistors R ₃ and R ₄ , the emitter of the transistor Q ₂ is connected to a power supply reference line V _G , and the transistor Q ₂ is further connected. The base of ₂ is connected to the power supply reference line V _G via a resistor R ₅ . The connection point between the resistors R ₃ and R ₄ is connected to the base of the NPN type transistor Q ₃ , and the resistor R ₆ and the resistor R ₆ are connected between the base of the transistor Q _{2 and} the base of the transistor Q _3.
7 is connected. Further, the collector of the transistor Q ₃ is connected to the base of the transistor Q ₁ , and the emitter is connected to the power supply reference line V _G.

A PNP transistor Q ₄ is connected in antiparallel to the transistor Q ₃ . That is, the emitter of the transistor Q ₄ is connected to the collector of the transistor Q ₃ , and the collector of the transistor Q ₄ is connected to the transistor Q ₃
Connected to the emitter. Capacitor C ₁ is connected between the base and emitter of the transistor Q _4, also the base of the transistor Q ₄ are resistors R _8, is connected to the output terminal of the operational amplifier A ₂ via the diode D _2.

A capacitor C ₂ and a diode D _{3 are provided} between the base of the transistor Q ₁ (collector of the transistor Q ₃ and emitter of the transistor Q ₄ ) and one end of the control winding N _B.
Is connected in parallel to the circuit in which the resistor R ₉ is connected in series. The same end of the control winding N _B is connected to the emitter of a PNP transistor Q ₅ via a diode D ₄ , a resistor R ₁₀ is connected between the base and emitter of this transistor Q ₅ , and a collector is a resistor R _6. ,
It is connected to the connection point of R ₇ . The other end of the control winding N _B is connected to the input terminal P ₂ and constitutes a power supply reference line V _G.

Diode D_FourThe anode of the PNP type
Transistor Q₇Connected to the emitter of
Anti-R₁₃Via the operational amplifier (comparator) A₁Non of
It is connected to the inverting input terminal. This operational amplifier A₁of
The non-inverting input terminal is the power supply reference line V_GBetween Zena
-Diode ZD₁While diode D is connected ₆
Through NPN transistor Q₆Connect to the collector
This transistor Q₆The emitter of the
V_GIt is connected to the.

One end of the control winding N _B is connected to the anode of the diode D ₈ via the resistor R ₁₄ , while being connected to one end of the capacitor C ₄ . The other end of the capacitor C ₄ is connected to the power supply reference line V _G , the cathode of the diode D ₈ is connected to the inverting input terminal of the operational amplifier A ₁ , and the parallel circuit of the resistor R ₁₅ and the capacitor C ₅ is connected. , The power supply reference line V _G. The resistors R ₁₄ , R ₁₅ , capacitors C ₄ , C ₅ , and diode D _{8 form} a frequency / voltage conversion circuit.

The base of the transistor Q ₆ is connected to the power supply reference line V _G via the resistor R ₁₉ and is also connected to the collector of the PNP type transistor Q ₇ via the resistor R ₂₀ . The output terminal of the operational amplifier A ₁ is connected to one end of the parallel circuit of the diode D ₇ and the resistor R ₁₆ , the capacitor C ₆ is connected between the other end of the parallel circuit and the cathode of the diode D ₄ , and the other end of the parallel circuit. Is connected to the base of the transistor Q ₇ via the Zener diode ZD ₂ and the resistor R ₁₇ . A resistor R ₁₆ , a diode D ₇ and a capacitor C _{6 form} a timer circuit. A resistor R ₁₈ is connected between the base and emitter of the transistor Q ₇ , and the collector is connected to the power source reference line V _G via the resistor R _21.
On the other hand, it is connected to the base of the transistor Q ₅ via the diode D ₉ and the resistor R ₁₁ . A resistor R ₂₂ is connected between the cathode of the diode D ₉ and the power supply reference line V _G.

Control winding N_BAt one end of the diode D_Five
Is connected to this diode D_FiveAnode and power reference
Line V_GCapacitor C in between₈Is connected to this dio
Mode D_FiveAnd capacitor C₈Connection point and control winding N_Bof
Resistance R between the ends₁₂, R₂₆Series circuit is connected, both resistors
The connection point of is the transistor Q₃Connected to the base of
It Also the capacitor C₈In parallel with each of the resistors R_{twenty three}When
Resistance R_{twenty four}, And resistance R ₂₆And Zener diode ZD₃of
The series circuit is connected and the resistance R_{twenty three}And resistance R_{twenty four}Connection point is
Peamplifier A₂To the inverting input terminal of the resistor R_{twenty five}And Zenada
Iodo ZD₃Is the operational amplifier A₂Non-inverting input of
It is connected to the terminal. In addition, operational amplifier A₂Inversion of
Between the output terminal and output terminal, capacitor C₇Are connected. Two
Next winding N _SEnd and output terminal P₃For rectification
De D_TenConnected to the output terminal P₃, P_FourSmooth between
Capacitor C₉Are connected.

Next, the operation of the embodiment apparatus configured as described above will be described. In the embodiment apparatus of FIG. 1, when the power is turned on, it operates as a power supply unit having the output current-output voltage characteristic shown in A of FIG. 3 regardless of the presence or absence of a load. In this case, operational amplifier A ₂ , resistors R ₂₃ , R ₂₄ , R
_{In the} constant voltage circuit composed of the first circuit 1 including the zener diode ZD ₃ and the transistor Q ₄ , the terminal voltage of the capacitor C ₈ is kept constant by controlling the base current of the transistor Q ₁ . Output terminals P ₃ , P ₄
As a result, a constant output voltage V ₀ is output.

In the apparatus of this embodiment, the transformer T 1
The number of turns of the control winding N _B on the secondary side is n _B , the number of turns of the secondary winding N _S is n _S , the voltage drop of the diode D ₅ is V _F5 , the voltage drop of the diode D ₁₀ is V _F10 , and the capacitor C _{8 is} if the voltage across the V _C, the output voltage V ₀ is expressed by _{V 0 = (n S / n} B) (V C + V F5) -V F10. As is clear from this equation, if the voltage V _C is kept constant, the output voltage V ₀ can be kept constant.

Next, the operation when a battery is connected as a load will be described. In this case, since the output current depends on the terminal voltage of the battery, it is set to an output current value corresponding to the terminal voltage on the output voltage-output current characteristic of A of FIG. The load power at this time is applied from the control winding N _B to a filter composed of a resistor R ₁₄ and a capacitor C ₄ , converted into a level signal corresponding to the frequency, and further, a diode D ₈ , a resistor R ₁₅ , and a capacitor C ₅ Then, it is rectified and smoothed and converted into a DC voltage, that is, converted into a voltage according to the load power in this frequency / voltage conversion unit, and applied to the inverting input terminal of the operational amplifier A ₁ .

On the other hand, the non-inverting input terminal of the operational amplifier is
Resistance R₁₃And Zener diode ZD ₁Basis determined by
A quasi voltage is applied. The reference voltage value at this time is shown in FIG.
When set to a, the voltage applied to the inverting input terminal is
Since it is higher than the quasi voltage, operational amplifier A₁Output is inverted
Resistance R₁₆And capacitor C₆Time constant circuit composed of
Is started to charge and the capacitor C₆The (-) side potential of
The second circuit 2 is operated when the time below the fixed value has passed.
The output of the transistor Q_FiveTurn off. You
That is, transistor Q₇Turn on the diode D₉
Signal from the transistor Q_FiveGiven to
Transistor Q_FiveTurn off. This off
Than transistor Q₂Also turn off.

When the transistor Q ₂ is turned off, the terminal voltage generated at both ends of the current detection resistor R ₂ is divided by the resistors R ₃ and R ₄ and added to the base of the transistor Q ₃ . It is applied directly through the resistor R ₃ and the transistor Q ₃ is driven to switch to the output current-output voltage shown by B in FIG. When the characteristic shown in B of FIG. 3 is within the current value range required for charging the battery, switching as a charger is automatically completed.

At this time, the transistor Q₇Oh
Transistor Q₆The base potential of the
Dista Q₆Is turned on, the diode D₆Drop of
Is the reference voltage, and the output current is less than the set value in Fig. 3b.
If it is not a value, operational amplifier A ₁Initial inverted output of
Can not be returned to the conditions of. That is, operational amplifier A
₁Has a hysteresis characteristic.

When switching from the battery charging function to the power source of the electronic device, the batteries connected to the output terminals P ₃ and P ₄ may be removed. When removed to the battery, the output current becomes 0,
The value becomes equal to or less than the set value b in FIG. 3, and the output of the operational amplifier A ₁ is returned to the initial condition. As a result, the transistor Q ₅ ,
Q ₂ is turned on, a resistor R _3, the base voltage in divided form with R _4, transistor Q ₃ is operated, the output characteristic of A in FIG. 3 - is returned to the output current characteristics. Therefore, the switching as the power supply device is completed.

[0022]

According to the present invention, the oscillation frequency on the primary side changes according to the change of the load, this frequency is converted into voltage, and the power supply function and the charging function are automatically changed according to the change of the frequency. Since it is switched to, there is no need for mechanical switches, photocouplers, etc. as in the past, it is cheap and
A power supply device with a charging function that can secure a highly accurate output voltage and charging current can be obtained.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a power supply device with a charging function showing an embodiment of the present invention.

FIG. 2 is a circuit block diagram showing a conventional power supply device with a charging function.

FIG. 3 is an output current-output voltage characteristic diagram for explaining the power supply / charge switching operation of the apparatus of the embodiment.

[Explanation of symbols]

T transformer N _P primary winding N _S secondary winding N _b control winding D ₁₀ diode C ₄ , C ₅ , C ₈ capacitor R ₁₄ , R ₁₅ resistance A ₁ , A ₂ operational amplifier Q ₁ , Q ₂ , Q ₅ transistor

Claims (3)

[Claims] 1. A transformer having a primary winding, a secondary winding, and a control winding, an oscillating circuit including the primary winding and the control winding, and oscillating at a frequency according to a load output, A power supply device with a charging function, comprising: a first rectifying / smoothing circuit that rectifies and smoothes a signal derived to a secondary winding, and outputs DC power from an output terminal. A second rectifying / smoothing circuit for rectifying / smoothing the voltage, and controlling the output voltage of the second rectifying / smoothing circuit to be a constant value when the load of the output terminal is a load other than a battery. A constant voltage control circuit, a frequency / voltage conversion circuit that receives a signal from the oscillation circuit and converts it into a voltage according to an oscillation frequency, compares an output voltage of the frequency / voltage conversion circuit with a predetermined reference voltage, If the output voltage of the frequency / voltage conversion circuit is high, And a constant current for controlling the current flowing through the load to be constant in response to a change in the output of the comparator to the signal of the first level. A power supply device with a charging function, comprising a control circuit. 2. A power supply device with a charging function according to claim 1, wherein the change in the first level signal output from the comparator is output to the constant current control circuit via a predetermined timer means. . 3. The power supply device with a charging function according to claim 1, further comprising a circuit for changing the reference voltage to a low value in response to the output of the comparator in response to the first level signal.