JPH1014239A - Power supply voltage division rectifier circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a low DC voltage from an AC commercial power supply without requiring any transformer by combining diodes and capacitors, connecting the capacitors in series during one half cycle of AC voltage, in order to charge the capacitors, connecting the capacitors in parallel during the other half cycle of AC voltage in order to take out the charged voltage and then dividing and rectifying the AC voltage. SOLUTION: An AC commercial power supply is connected across a voltage division charging circuit (unit series circuit) and capacitors C1 -C5 are charged through respective diodes D1 , D4 , D7 , D10 , D13 during the positive half cycle of an AC voltage. A diode parallel correction circuit takes out the charged voltage of each capacitor C1 -C5 in the unit series circuit during the negative half cycle of the AC voltage. The diode parallel correction circuit comprises diodes D3 , D6 , D9 , D12 for connecting the negative potential side of the capacitors C1 -C5 in the unit series circuit with a COM line, during the negative half cycle of the AC voltage, and diodes D2 , D5 , D8 , D11 , D14 for connecting the positive potential side thereof with a voltage-take out section A.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply voltage dividing and rectifying circuit, and more particularly to a voltage dividing and rectifying circuit which divides and rectifies a commercial AC voltage into a DC voltage.

[0002]

2. Description of the Related Art Conventionally, there are roughly the following methods for obtaining a DC voltage lower than a commercial AC power supply. The AC of the commercial power supply voltage is converted into a low-voltage AC by a transformer and then rectified to DC. A low DC voltage is obtained by dividing the DC obtained by rectifying the AC of the commercial power supply voltage using a resistor. After converting the alternating current of the commercial power supply voltage to high frequency, it is converted to low voltage by a small transformer using ferrite and then rectified to obtain direct current. Etc.

However, these conventional techniques have the following problems. Transformers used in commercial AC power supplies use silicon steel, so they are heavy and large, and loss due to iron loss and copper loss is large. Then, for example, 100V
If a DC of 10 V is to be obtained from the AC, the loss due to the resistance reaches 90%, and the energy loss is extremely large. If the current is large, measures such as heat radiation are required.
Since the capacity of the capacitor can be small, the size can be reduced. However, the circuit becomes complicated,
Not only is it expensive, but it also has a large loss as a power supply that is always used.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has a simple circuit configuration without using a transformer and a power supply voltage divider capable of obtaining a DC low voltage from a commercial AC power supply. It is an object to provide a rectifier circuit.

[0005]

According to the power supply voltage dividing rectifier circuit of the present invention, a diode and a capacitor are combined to charge a capacitor in series in an AC half cycle and to divide the capacitor in a parallel connection in another half cycle. The AC voltage is divided and rectified simultaneously by extracting the voltage charged in the capacitor.

Further, a voltage division charging circuit in which a plurality of sets each including a diode and a capacitor for charging a capacitor in a forward direction via a diode during a positive half cycle of an AC is connected in series, And a diode group connected in parallel during the negative half cycle of AC to take out an output voltage. And a switching circuit for taking out as a DC voltage at the time of the negative half cycle.

According to the present invention, by applying an AC voltage to a circuit in which a set of a diode and a capacitor is connected in series, each capacitor is divided and charged in a positive half cycle of the AC. Then, a diode group acts so as to connect each capacitor in parallel in another negative half cycle, thereby taking out a divided voltage. In other words, the AC voltage can be divided into a plurality of capacitors without using a transformer, and the divided DC voltage can be efficiently taken out without a resistance loss by a simple circuit configuration.

[0008]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows a power supply voltage dividing rectifier circuit according to an embodiment of the present invention. This circuit is, for example, a voltage dividing rectifier circuit that divides a single-phase 100 V commercial AC power supply into five and obtains a DC low voltage of about 20 V or less. Five sets of unit series circuits of diodes and capacitors are connected in series to form a voltage division charging circuit. The unit series circuit, a diode D ₁ and capacitor C _1, diode D ₄ and the capacitor C _2, a series circuit composed of five sets of ... diode D ₁₃ and the capacitor C _5. By connecting a commercial AC power supply terminal to both ends of this voltage division charging circuit, each diode D ₁ , D ₄ , D ₇ ,
Each through D _10, D ₁₃ capacitors _{C 1, C 2, C 3} , C 4,
To charge the C _5. Each capacitor C ₁ , C ₂ , C ₃ , C ₄ , C ₅
, The commercial AC power supply voltage is divided into five equal parts by each capacitor.

A diode parallel connection circuit is provided for extracting voltages charged in the capacitors C ₁ , C ₂ , C ₃ , C ₄ and C ₅ of the unit series circuit during the negative half cycle of the alternating current. . This circuit sets the negative potential side of the capacitor of each unit series circuit to COM during the negative half cycle of the AC voltage.
Diodes D ₃ , D ₆ , D ₉ , D ₁ connected to (common) line
₂ and diodes D ₂ , D ₅ , D ₈ , D which connect the positive potential side of the capacitor of each unit series circuit to a common voltage extraction section A.
And a _11, D ₁₄ Prefecture.

[0011] Diodes _{D 3, D 6, D 9} , D 12 , respectively during the negative half cycle of the AC become forward biased, it becomes conductive. Accordingly, although there is a forward voltage drop of the diode, if this voltage drop is ignored, the negative potential side of the capacitors C ₂ , C ₃ , C ₄ , and C _{5 is} the negative potential side of the capacitor C ₁ , that is, COM ( Common) line. Then, the diode D ₁₃ are cut off as a result becomes reverse biased during the negative half cycle of the AC. Therefore, since each of the capacitors C ₁ , C ₂ , C ₃ , C ₄ , C ₅ is charged to a positive voltage, the diodes D ₂ , D ₅ , D _5
8, D _11, D ₁₄ becomes forward biased, neglecting the forward voltage drop of the diode, which is in a state of being connected in parallel to a common voltage extraction section A.

The switching circuit cuts off the output side during the positive half cycle of the alternating current and the capacitors C ₁ , C ₂ , C ₃ , C ₄ ,
Charge the C _5, to connect the negative of the capacitor C ₁ during a _{half-cycle, C 2, C 3, C} 4, the voltage charged to C ₅ of the AC output side. This switching circuit comprises transistors Q ₁ ,
It is composed of a circuit in which resistors R ₁ , R ₂ and R ₃ are connected to Q ₂ as shown. That is, during the positive half cycle of the alternating current,
The positive voltage divided by the resistors R ₁ and R ₂ is applied to the transistor Q ₂
Is applied to the base, the transistor Q ₂ is turned on. Thus, the transistor Q ₁ is turned off to cut off the voltage extraction portion A of the diode parallel-connected circuit side from the output side. During the negative cycle of the AC, the negative voltage divided by the resistors R _1, R ₂ is applied to the base of the transistor Q _2, the transistor Q ₂ is turned off. Thus, the transistor Q ₁ is turned on to connect the voltage extraction portion A of the diode parallel-connected circuit side to the output side.

The capacitor C ₀ is for smoothing the DC output, and the resistance R _L is a load resistance. Diode D ₀ of which is incorporated to prevent the charge transistor protection and Q ₂ are charged to the C ₀ in a state of ON flows back through the Q _1, Q _2.

Next, the operation of the voltage dividing rectifier circuit will be described. When a positive half-cycle alternating current with an effective value of 100 V is applied to this circuit, the diodes D ₁ , D ₄ ,
D _7, D _10, D ₁₃ and the capacitor _{C 1, C 2, C 3} , C 4, C 5
100 × √2 at the peak value in the voltage division charging circuit
A voltage of V is applied. Accordingly, each capacitor is charged with a voltage of V ₀ = (√2 × 100/5) −V _D. Here, V ₀ is a voltage at no load, and V _0
D indicates the amount of forward voltage drop by the diode (about 0.6 V when using a silicon diode). Next, when the negative half cycle AC of this circuit is applied, the capacitors C ₁ ,
Diodes D ₁ , D ₄ , D ₇ , D ₁₀ , D ₁₃ connected in series with C ₂ , C ₃ , C ₄ , C ₅ block the current and capacitors C ₁ , C ₂ , C ₃ , C ₄ The diodes D ₃ , D ₆ , D ₉ , and D ₁₂ connected in parallel with each other are in the forward direction, and the negative potential sides of the respective capacitors C ₂ , C ₃ , C ₄ , and C ₅ are set to substantially the common potential.

Therefore, each of the capacitors C ₁ , C ₂ ,
Diodes D ₂ , D ₄ are connected from the terminals on the positive potential side of C ₃ , C ₄ , C _5.
5 , D ₈ , D ₁₁ , D ₁₄
So that the capacitor voltage V ₀ which per piece is taken out in parallel. However, during the positive half cycle of the alternating current, the positive half-wave rectified voltage of the power supply is applied to the voltage extracting point A, so that a direct current low voltage cannot be extracted as it is. Therefore, the above-described switching circuit capable of extracting a current only during the negative half cycle is used.

Although a simple circuit for this purpose is constituted by the _two transistors Q ₁ and Q ₂ , any other structure may be used as long as it has the function described above. In actual use, the transistor Q ₁ is turned off during the positive half cycle of the AC, and the capacitors C ₁ , C ₂ , C ₃ , C
_4, C ₅ is charged, the transistor Q ₁ is turned on during the negative half cycle of the AC, the capacitors C _1, C _2,
C ₃ , C ₄ , and C ₅ are connected in parallel, and the voltage extracting unit A is connected to the output side. Strictly, it is necessary to consider the voltage drop due to the diode and the voltage drop due to the current load.

The following table shows actually measured data indicating the relationship among various load resistances R _L , DC output, ripple magnitude, etc. when the smoothing capacitor C ₀ is 50 μF. FIG. 2 is a diagram illustrating a relationship between an output current, an output voltage, and a ripple voltage with respect to various capacitance values of a smoothing capacitor.

(C0 = 50 μF) ───────────────────────────────── Load R _L DC output Ripple AC input ─ ──────────────────────────────── [Ω] [V] [mA] [V _P - _P ] [V] ───────────────────────────────── ∞ 24.5 1m * 96.0 56k 23.5 0.4 80m 96.2 22k 22.4 1.0 0.2 ** 94.6 10k 21.7 2.2 0.4 ** 94.6 4.7k 20.5 4.4 0.9 94.7 2.2k 18.4 8.4 1.7 94.2 1.0k 15.0 15.0 3.1 94.3 820 13.9 17.0 3.5 94.4 680 12.9 19.0 3.9 94.0 560 11.8 21.1 4.3 94.2 ────────── ─────────────────────── * Drift about 1mV * Drift about 20mV

From this figure and the table, it can be seen that when the load resistance is reduced, that is, when the load current is increased, the output voltage is reduced and the ripple is increased, but when the load current is increased, the capacitors C _{0 to} C ₅ are reduced. It is preferable to increase the capacitance value according to the current.

Note that, when using this circuit,
Since the 00V line is directly connected to the common line, care must be taken to prevent electric shock. If this circuit is incorporated into a small device such as a mobile phone, the device can be provided with a charging circuit with almost no increase in weight. in this case,
If you choose to use the device by disconnecting it from the outlet, you will not have to worry about electric shock. In addition, if a radio receiver capable of automatically receiving an earthquake warning or the like or a power supply that keeps the television always on is used, the current consumption can be extremely reduced, which is an energy saving measure.

The voltage division charging circuit of the above-described embodiment is obtained by dividing AC 100 V by five capacitors, but this is for the sake of illustrating the principle of the present invention. For example, it is a matter of course that a DC voltage of about +10 V can be obtained using ten capacitors, and the number of divisions should be appropriately changed according to the application. Here, when the number of divisions is increased, the influence of the forward voltage drop due to the common connection diodes D ₃ , D ₆ , D ₉ , and D ₁₂ increases. The diode D ₃ as shown in FIG. 3 in order to reduce the influence,
D ₆ , D ₉ and D ₁₂ are preferably connected in parallel. In the case of FIG. 2, a withstand voltage for preventing a positive half cycle is required for each diode.

[0022]

As described above, according to the power supply voltage dividing rectifier circuit of the present invention, a low-voltage DC power supply can be obtained from a commercial AC power supply without using a transformer. In particular, it is effective for a small load current, and can achieve a small and light weight and high conversion efficiency with a simple circuit configuration.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a power supply voltage division rectifier circuit according to an embodiment of the present invention.

FIG. 2 is a diagram showing output characteristics of the circuit.

FIG. 3 is a circuit diagram of a power supply voltage division rectifier circuit according to another embodiment of the present invention.

[Explanation of symbols]

_{C 1, C 2, C 3} , C 4, C 5 voltage dividing capacitor _{D 3, D 6, D 9} , D 12 common connection diode _{D 2, D 5, D 8} , D 11, D 14 voltage extraction unit connected Diode A Voltage extractor Q ₁ , Q ₂ Switching circuit transistor C ₀ Smoothing capacitor D ₀ Backflow prevention diode _RL Load resistance

Claims (2)

[Claims] 1. Combining a diode and a capacitor to charge a capacitor by series connection in a half cycle of an alternating current and taking out a voltage charged in the capacitor divided in a parallel connection in another half cycle to obtain an alternating current A power supply voltage division rectifier circuit, which divides and rectifies a voltage at the same time. 2. A voltage division charging circuit comprising: a plurality of sets each including a diode and a capacitor for charging a capacitor in a forward direction via a diode during a positive half cycle of an alternating current; And a diode group connected in parallel during the negative half cycle of AC to take out an output voltage. And a switching circuit for taking out as a DC voltage during a negative half cycle of the power supply voltage dividing rectifier circuit.