JP2002369500A - Boosting circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a small ripple-stable output voltage from a charge-pump type boosting circuit. SOLUTION: The boosting circuit 1A is provided with primary-side capacitors C1a and C1b and switching circuits SW1 and SW2, respectively connected to the capacitors C1a and C1b. The circuit 1A is constituted to control the switching of the switching circuits SW1 and SW2 by respectively sending drive clock signals ϕ1 and ϕ2 to the circuits SW1 and SW2, and while the primary- side capacitor C1a is being charged, to move charges from the other primary- side capacitor C1b to a secondary-side capacitor C2. While the capacitor C1b is being charged, the circuit 1A moves charges from the other primary-side capacitor C1a to the secondary-side capacitor C2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a technique for obtaining a stable output voltage with little ripple in a charge pump type booster circuit.

[0002]

2. Description of the Related Art The basic operation (pumping operation) of a charge pump type single-stage booster circuit is realized by two cycles of charging a primary-side capacitor and transferring charges from the primary-side capacitor to a secondary-side capacitor. That is, by alternately repeating the operation of charging the primary-side capacitor (or charge cycle) and the operation of transferring the accumulated charge of the capacitor to the secondary-side capacitor (or charge transfer cycle), the output from the secondary-side capacitor is repeated. The voltage is obtained.

[0003]

However, in the conventional circuit, since the secondary capacitor only discharges the externally connected load in the charging cycle of the primary capacitor, the output voltage is greatly reduced. On the other hand, in the charge transfer cycle from the primary-side capacitor to the secondary-side capacitor, the output voltage sharply rises, so that the output voltage greatly fluctuates between each cycle, and there is a problem in ripple characteristics.

Accordingly, an object of the present invention is to obtain a stable output voltage with small ripple in a charge pump type booster circuit.

[0005]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention comprises a plurality of primary-side capacitors, and switching circuits respectively connected to the primary-side capacitors.
A secondary capacitor, and while the charging of the primary capacitor connected to the switching circuit is performed by a certain switching circuit among the plurality of switching circuits, each of the plurality of switching circuits is separately connected to the other switching circuit. The charge transfer from the primary side capacitor to the secondary side capacitor is performed.

Therefore, according to the present invention, the charging cycle and the charge transfer cycle are reciprocally repeated with respect to a plurality of primary capacitors, so that a secondary battery is charged in a certain primary capacitor charging cycle. Since the charge transfer from the primary side capacitor is performed to the side capacitor, even if an external load is connected to the output terminal on the secondary side, the fluctuation of the output voltage between the charge cycle and the charge transfer cycle should be kept small. Thus, ripple can be reduced.

[0007]

FIG. 1 is an equivalent circuit diagram showing a basic configuration of the present invention.

In the booster circuit 1, pumping is performed between a plurality of primary-side capacitors C1a and C1b (in the figure, an example using two capacitors is shown for convenience of explanation) and one secondary-side capacitor C2. A plurality of switching circuits SW1 and SW2 are provided for performing exclusive control of the operation.

A switching circuit SW1 (simply indicated by a changeover switch in the figure) is connected to the primary-side capacitor C1a, and performs a charging operation from the current source I1 to the capacitor C1a in the first state. In the second state, the one-way switching element D1
(The element is indicated by a diode symbol in the figure. The element is arranged in the forward direction from the capacitor C1a to C2.) The state is switched so that charge transfer to the secondary-side capacitor C2 is performed. Done.

Similarly, a switching circuit SW2 (simply indicated by a changeover switch in the figure) is connected to the primary-side capacitor C1b, and in the first state, the current source I
2 to the capacitor C1b, and in the second state, a one-way switching element D2 (indicated by a diode symbol in the figure) from the capacitor C1b. The state is switched so that the electric charge is transferred to the secondary-side capacitor C2 via the power supply line.

[0013] While one of the switching circuits, for example, SW1 is in the first state and the primary-side capacitor C1a connected to the switching circuit is being charged, the other is not. Switching circuit, that is, primary side capacitor C connected to SW2
Charge transfer from 1b to the secondary-side capacitor C2 is performed. Conversely, while the switching circuit SW2 is in the first state and the primary capacitor C1b connected to the switching circuit is being charged, the primary capacitor C1a connected to the other switching circuit SW1 is charged. Charge transfer to the secondary capacitor C2 is performed. Each of the switching circuits SW1 and SW2 is supplied with a driving signal from a circuit (not shown) to perform switching control of each circuit, or the switching circuits are alternately switched by self-excited oscillation. You.

As described above, when the number of the primary side capacitors is two, each switching circuit is reciprocal (or contradictory).
The pumping operation is performed by alternately repeating the charging operation of each capacitor and the charge transfer from the primary side to the secondary side, so that the terminal voltage of the secondary side capacitor C2 is proportional to the accumulated charge amount. And a boosted output is obtained from the output terminal To connected to the capacitor C2.

It is easy to extend the above description to a circuit having three or more primary-side capacitors and a switching circuit connected to each of the capacitors. During charging of the connected primary-side capacitor, switching control may be performed so that charge transfer from the primary-side capacitor connected to each of the other switching circuits to the secondary-side capacitor is performed.

A multi-stage booster circuit may be constructed by combining a plurality of such booster circuits (for example, after a charging operation and a charge transfer are repeated between two or more capacitors, a final output stage may be used). It is needless to say that a larger output voltage can be obtained by a configuration for obtaining an output voltage from a capacitor.

FIG. 2 shows a primary capacitor and a CMOS.
(Complementary Metal Oxide Semiconductor) This is an example of a configuration of a single-stage booster circuit 1A having two switching circuits.

As shown in the figure, in this example, there are two primary-side capacitors C1a and C1b and one secondary-side capacitor C2, and switching circuits SW1 and SW2 for each primary-side capacitor are respectively provided. It has become.

The switching circuit SW1 for the primary side capacitor C1a includes a P-channel MOS transistor P
1 and an N-channel MOS transistor N1 are complementarily connected (complementary pair or complementary pair), the gates of the transistors are connected and shared, and a driving clock signal from a signal generator (not shown) (This is referred to as “φ1”).

A predetermined power supply voltage (this is referred to as "Vcc") is supplied to the source of the MOS transistor P1.
The drain of the transistor P1 is a MOS transistor N
1 and the source of the transistor N1 is grounded.

One end of a capacitor C1a is connected to a connection point between the transistors P1 and N1, and a diode D is connected to the other end of the capacitor C1a (refer to "point A" in the figure).
1a and D1b are connected. That is, the diode D
1a is connected to the point A, the cathode of the diode is connected to one end of the secondary-side capacitor C2,
Further, the cathode of the diode D1b is connected to the point A,
The anode of the diode is connected to the source of the transistor P1 so that the power supply voltage Vcc is supplied.

As for the switching circuit SW2 for the primary side capacitor C1b, the switching circuit S2
It has the same configuration as W1, and has a configuration in which a P-channel MOS transistor P2 and an N-channel MOS transistor N2 are complementarily connected. And
The gates of the transistors are connected to each other, and a driving clock signal from the signal generator (not shown) (the signal φ
1 is a clock signal having a phase opposite to that of
2 ". ) Is supplied.

The power supply voltage Vcc is supplied to the source of the MOS transistor P2, the drain of the transistor P2 is connected to the drain of the MOS transistor N2, and the source of the transistor N2 is grounded.

One end of a capacitor C1b is connected to a connection point between the transistors P2 and N2, and a diode D is connected to the other end of the capacitor C1b (see point "B" in the figure).
2a and D2b are connected. That is, the diode D
The anode of 2a is connected to point B, the cathode of the diode is connected to one end of the secondary capacitor C2,
Further, the cathode of the diode D2b is connected to the point B,
The anode of the diode is connected to the source of the transistor P2 so that the power supply voltage Vcc is supplied.

A power supply voltage Vcc is supplied to one end of the secondary-side capacitor C2, and the other end of the capacitor (“O” in FIG.
Point ". ) Are connected to respective cathodes of the diodes D1a and D2a, and as shown in FIG.
2 for each switching circuit and primary side capacitor,
The diodes have a symmetrical arrangement.

The output voltage of this circuit is obtained from an output terminal TOUT connected to point O.

FIG. 3 is a timing chart for explaining the operation of this circuit. The meaning of each symbol is as follows.

"Stat_C1a" = primary-side capacitor C1
“stat_C1b” indicates the distinction between the charge period and the charge transfer period for “a”. “stat_C1b” indicates the distinction between the charge period and the charge transfer period for the primary-side capacitor C1b. "OUT" = indicates an output voltage.

Note that "H" shown in FIG.
“L” indicates a low level, “2Vcc” indicates twice the power supply voltage Vcc, and “GND” indicates a ground level. Also, φ1 and φ2 are clock signals having an antiphase relationship with each other as described above (for example,
The output phase φ1 of the signal obtained from the clock signal generation circuit may be inverted so that the output phase φ2 of the opposite phase can be obtained by logical negation. ).

As can be seen, when the signal φ1 is at the L level, the charge transfer period (or charge transfer cycle) from the primary capacitor C1a to the secondary capacitor C2.
It is in. This is because the transistor P1 is on and the transistor N1 is off in the switching circuit SW1, and charge is transferred from the capacitor C1a to the capacitor C2 through the diode D1a.
Therefore, during this time, the potential V_A gradually decreases as time elapses.

On the other hand, since the signal φ2 is at the H level, the primary side capacitor C1b is in a charging period (or charging cycle). That is, the switching circuit SW2
The transistor P2 is in the off state and the transistor N
2 is in the ON state, the capacitor C1b is charged via the diode D2b. Therefore, during this time,
The potential V_B gradually increases with time.

In this figure, for convenience of explanation, the forward voltage drop (VF) of each diode is neglected, so that the capacitors C1a and C1b are charged and their terminal voltages become Vcc.
Note that the capacitor C2 is charged to 2Vcc (= 2 × Vcc) by the charge transfer of C1a and C1b charged in the previous cycle.

Next, when the signal φ1 becomes H level, the operation shifts to the charging period of the primary side capacitor C1a. That is,
Since the transistor P1 is turned off and the transistor N1 is turned on in the switching circuit SW1, the capacitor C1a is charged via the diode D1b.

On the other hand, since the signal φ2 is at the L level, the period shifts to the period of charge transfer from the primary capacitor C1b to the secondary capacitor C2. That is, in the switching circuit SW2, the transistor P2 is turned on, and the transistor N2 is turned on.
Is in the OFF state, charge is transferred from the capacitor C1b to the capacitor C2 through the diode D2a.

As described above, the first circuit including the primary-side capacitor C1a and the switching circuit SW1 and the second circuit including the primary-side capacitor C1b and the switching circuit SW2 reciprocate the charge cycle and the charge transfer cycle. By alternately repeating, the secondary side capacitor C2
Output voltage OUT 端子 2Vcc from the output terminal TOU
By suppressing the voltage fluctuation in each cycle with respect to the externally connected load connected to T, an output voltage OUT with small ripple can be obtained.

Accordingly, the following various advantages can be obtained.

A high-precision voltage with small ripple can be obtained with the simple circuit configuration as described above.

It is effective in suppressing the voltage fluctuation with respect to the transient load characteristics.

According to the configuration of FIG. 2, a CMOS IC
(Integrated circuit) A booster circuit can be easily constructed in the (integrated circuit), and is suitable for low power consumption.

The capacity of the secondary-side capacitor can be reduced, which is advantageous in terms of cost reduction, mounting space, and mounting area.

In the examples shown in FIGS. 2 and 3, the primary capacitors C1a and C1b have the same capacitance, and
Both the H level period and the L level period of the signals φ1 and φ2 have the same length (duty cycle 50%), but the present invention is not limited to this. Of course, various embodiments without departing from the gist of the present invention, such as changing the duty cycle of the driving signal to the circuit according to the capacitance ratio of the capacitor, are included in the technical scope of the present invention. .

[0040]

As is apparent from the above description, according to the first aspect of the present invention, in the charging cycle of a certain primary capacitor, the charge from the other primary capacitor is stored in the secondary capacitor. Since the transfer is performed, even if an external load is connected to the output terminal on the secondary side, the fluctuation of the output voltage between the charge cycle and the charge transfer cycle can be suppressed small, and compared with the conventional circuit configuration. Excellent ripple characteristics.

According to the second aspect of the present invention, a circuit having a first primary-side capacitor and a switching circuit and a circuit having a second primary-side capacitor and a switching circuit are provided. An output voltage with little fluctuation can be obtained by a simple circuit configuration in which charge transfer cycles are performed reciprocally, which is advantageous in terms of cost and mounting area.

According to the third and fourth aspects of the invention,
A larger output voltage can be obtained by configuring a multi-stage booster circuit by combining a plurality of booster circuits.

[Brief description of the drawings]

FIG. 1 is an equivalent circuit diagram showing a basic configuration of a booster circuit according to the present invention.

FIG. 2 is a diagram for explaining an example of a circuit configuration together with FIG. 3, and FIG. 2 is a circuit diagram.

FIG. 3 is a timing chart for explaining the operation of the circuit.

[Explanation of symbols]

1, 1A: booster circuit, C1a, C1b: primary side capacitor, SW1, SW2: switching circuit, C2: secondary side capacitor, C1a: first primary side capacitor, SW1
... First switching circuit, C1b ... Second primary side capacitor, SW2 ... Second switching circuit

Claims (4)

[Claims] 1. A charge pump type booster circuit comprising a plurality of primary side capacitors, a switching circuit separately connected to each of the capacitors, and a secondary side capacitor, wherein: While the charging of the primary-side capacitor connected to the switching circuit is performed by a certain switching circuit, the charge transfer from the primary-side capacitors respectively connected to the other switching circuits to the secondary-side capacitor is performed. A booster circuit characterized by the above-mentioned. 2. The booster circuit according to claim 1, wherein the first and second primary capacitors, a first switching circuit connected to the first primary capacitor, and a second primary capacitor. A second switching circuit connected thereto, during the charging of the first primary-side capacitor, charge is transferred from the second primary-side capacitor to the secondary-side capacitor, and the second primary-side capacitor is charged. During charging, the first switching circuit and the second switching circuit operate reciprocally with each other so that charge transfer from the first primary-side capacitor to the secondary-side capacitor is performed. circuit. 3. A booster circuit comprising a plurality of booster circuits according to claim 1 to constitute a multi-stage booster circuit. 4. A booster circuit comprising a plurality of booster circuits according to claim 2 combined to form a multi-stage booster circuit.