JPH04162560A - Charge pump circuit - Google Patents

Abstract

PURPOSE:To provide a circuit capable of producing desired output voltage with an irreducible minimum consumption current by installing a feedback parts for modulating switching frequency of the input in to a charge pump circuit according to the degree of the load, and by installing a VCO which receives the output of the feedback part as voltage control signal and outputs the switching signals for the charge pump circuit. CONSTITUTION:There are provided with a charge pump circuit 1 for charging a capacitor by switching pulses and for stepping up or down DC voltage, feedback parts 2 and 3 for modulating switching frequency of the input into the charge pump circuit 1 and a VCO (Voltage Control Oscillator) 4 which receives the outputs of the feedback parts 2, 3 as voltage control signals and outputs the switching signals for the charge pump circuit 1. In details, the above- mentioned feedback parts 2 and 3 have a voltage dividing circuit 2 and an error amplifier 3. The voltage dividing circuit 2 divides voltage of the output of the charge pump circuit 1. The error amplifier 3 compares the output of the voltage dividing circuit 2 with a reference voltage and outputs the voltage control signal to the VCO4.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a charge pump circuit, and particularly to a charge pump circuit built into a semiconductor integrated circuit (hereinafter abbreviated as IC) by optimizing current consumption.

[Conventional technology]

As shown in Figure 5, the conventional charge pump circuit has an odd number of inverters connected, a ring oscillator 50 that feeds back the last stage to the first stage for self-oscillation, and uses the output of the ring oscillator 50 as a switching signal. a charge pump circuit 51 that switches a capacitor charging circuit;
It has a clamp circuit 52 that clamps an excessively boosted voltage output from the charge pump circuit. The charge pump circuit shown in FIG. 5 utilizes the inherent delay time of inverters, connects an odd number of inverters, and forms a positive feedback loop to form an oscillation circuit. The oscillation frequency of this ring oscillator 50 is roughly expressed as f in equation (1), where tdiNV is the sum of the rise delay time and fall delay time of each inverter, and n is the number of connected inverters. (txn)
-(1-lNV) Regarding the internal circuit of the 6-charge pump circuit to be calculated, are there various circuit examples? For example, FIG. The clamp circuit shown in this example has been boosted to a high voltage in advance to obtain the desired output voltage.
A clamp circuit works to suppress excess voltage.

Another conventional example is shown in FIG. This example has a constant voltage circuit 60 and a charge pump circuit 61 which uses the constant voltage circuit output Vr8f as a reference voltage and boosts the voltage by m times to obtain an output voltage of m×ref. This example is widely put into practical use as a power source for driving liquid crystals of ICs for watches and ICs for calculators.

[Problem to be solved by the invention]

In the conventional example shown in Fig. 5, the oscillation frequency of the ring oscillator is fixed at the stage when the configuration circuit is determined, and the current consumption of the ring oscillator is large regardless of the load of the charge pump circuit output. It was a hindrance. Furthermore, there is a clamp circuit in the output section, and the desired output voltage is determined by the setting accuracy of the clamp pressure.
Increasing precision by incorporating C had the disadvantage of increasing costs.

In the conventional example shown in FIG. 6, the output voltage is m
Since the output voltage can be determined as It was getting worse.

An object of the present invention is to provide a charge bond 1 circuit that obtains a desired output voltage with the minimum necessary current consumption.

[Means to solve the problem]

In order to achieve the above object, the charge pump circuit according to the present invention switches pulses to charge a capacitor and step up or step down a DC voltage, depending on the degree of load on the charge pump circuit. A feedback section that modulates the switching frequency of the charge pump circuit input, and a V that uses the output of the feedback section as a voltage control signal and outputs the switching signal of the charge pump.
CO (Voltage Controlled 0sc
illustrator).

The feedback section also includes a voltage divider circuit and an error amplifier, the voltage divider circuit divides the charge pump circuit output, and the error amplifier compares the voltage divider circuit output with a reference voltage, V
It outputs a voltage control signal for CO.

[Effect]

A feedback section is provided that modulates the switching frequency of the input to the charge pump circuit depending on the degree of load on the charge pump circuit. The feedback section consists of a voltage divider circuit and an error amplifier, and the switching frequency of the charge pump circuit is adjusted to the optimum frequency depending on the degree of load.
0scillator) is added to the ring oscillator function.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

In the figure, the solid line side shows a charge pump circuit 1 that charges a capacitor by switching, a voltage divider circuit 2 that divides the output of the charge pump circuit 1, and an error caused by comparing the output of the voltage divider circuit 2 with a reference voltage. An error amplifier 3 that amplifies the voltage, and a VCO (1) that uses the output of the error amplifier 3 as a control voltage and outputs a switching signal for the charge pump circuit (1).
VoltageControlled 0skillt
or) 4. Further, 5 indicates the load.

For more concrete explanation, the embodiment shown in FIG. 2 will be explained.

FIG. 2 is an example specifically showing the internal circuit of the configuration shown in FIG. As an example of the charge pump circuit 1, a double voltage booster circuit, which has been proven in the past, is used. That is, the output voltage V. This is an example in which =2XVoo is obtained. here,
The double voltage booster circuit consists of MOS)-transistors T1 to T8.
, C, and C2, and the operation thereof is already a well-known technology and will be omitted here, but the charge pump circuit 1 is provided with a triple voltage booster circuit 30 shown in FIG. 3 or a triple voltage booster circuit 30 shown in FIG. /2x booster circuit 40 may be replaced as is.

The voltage divider circuit 2 has resistors r, t and a capacitor C, and the output V of the charge pump circuit 1. r / (r
+r2). That is, the output V of the voltage division diagram 2 is: "V, = fr2/ (r1+r2)) ・Vo...
It can be calculated as (2). The error amplifier 3 uses the reference voltage ■
,. , is connected to the non-inverting input, and the output V of the voltage dividing circuit 2 is connected to the inverting input via the resistor r3. When negative feedback is applied between the differential amplifier output and the inverting input using a resistor r4, the output VC of the error amplifier 3 can be expressed by equation (3).

vo=vref-(r4/r3)(vl-vref)・
...(3) That is, vc, which is the voltage control input of the VCO 4, is the output V of the voltage divider circuit 2 and the reference voltage V, with the reference voltage Vref as the center.
The difference (v, -v) of r4/ref
+ refr Amplified three times to obtain a voltage with reversed polarity. The circuit configuration of VCO4 has MOS transistors T9 to T22, a modified ring oscillator circuit, and an inverter load transistor T10'T.
12'''14°T and the gate voltage of T16 are voltage controlled and connected to the output V of the error term width amplifier 3.

By doing the above, the output V of the error amplifier 3.

As the oscillation frequency increases, the load current characteristic of the inverter of the ring oscillator increases, and the oscillation frequency increases.As the oscillation frequency increases, the switching speed of the charge pump circuit 1 also increases, and the output V of the charge pump circuit 1 increases. It also becomes more expensive. As a result, the output V of the voltage divider circuit 2 also increases,
According to equation (3), feedback is applied that the output VC of the error amplifier 3 is lowered, and automatic control is activated.

Putting together equations (2) and (3), the output V of the error amplifier is
. and the charge pump circuit output Vo, v =
V − (r / r ) ([r2/c
ref 4 3(r+r)
] ・V V , et l...The relational expression (4) holds true.

Also, the load current of each inverter of the ring oscillator is I = 1/2 β (V - V
)...(5)L
cT (β is MOS) - conduction coefficient of transistor), and in this example where five inverters are connected, including the inverter for waveform amplification, 6×■
The current consumption of the ring oscillator can be calculated as , and the output V as a charge pump circuit.

It is configured to operate with the minimum current consumption to obtain the desired results.

〔Effect of the invention〕

As explained above, the present invention provides a ring oscillator with vC
o configuration, the desired output voltage V can be achieved. It is possible to realize a charge pump circuit with the minimum current consumption necessary to obtain the above, and is an extremely effective means of incorporating the IC.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing one embodiment of the present invention, and FIG.
The detailed internal circuit diagram of the configuration shown in Fig. 1 is shown in Fig. 3.
Figure 4 shows a 1/2 voltage booster circuit of the charge pump circuit shown in Figure 1, and Figure 5 shows a conventional charge pump circuit. FIG. 6 is a diagram showing a conventional circuit for charge pumping a reference voltage. 1...Charge pump circuit 2...Voltage divider circuit 3...Error amplifier 4...
・VCO5...load T ~T22...MO3I-ransistor C~C3...
・Capacitors r1 to r4...Resistance 4, /no Figure 2 50
Figure 6 of 5

Claims (2)

[Claims] (1) In a charge pump circuit that charges a capacitor by switching pulses to step up or step down a DC voltage, a feedback section that modulates the switching frequency of the input to the charge pump circuit depending on the degree of load on the charge pump circuit;
A VCO (Voltage Co., Ltd.) uses the output of the feedback section as a voltage control signal and outputs a charge pump switching signal.
What is claimed is: 1. A charge pump circuit comprising: (2) The feedback section includes a voltage dividing circuit and an error amplifier, the voltage dividing circuit divides the charge pump circuit output, and the error amplifier compares the voltage dividing circuit output with a reference voltage. S,V
2. The charge pump circuit according to claim 1, wherein the charge pump circuit outputs a voltage control signal for CO.