JPS6318959A - Positive voltage/negative voltage converter circuit - Google Patents

Abstract

PURPOSE:To produce a low value as a negative voltage output value by produc ing the output of a rectangular wave oscillator from a MOSFET irrespective of 'H' or 'L' level of an oscillation waveform. CONSTITUTION:When the output of a rectangular wave oscillator 8 is an 'H' level, the charging current of the oscillator 8 flows through a capacitor 11 and a diode 12 to a ground. When the output of the oscillator 8 is inverted to an 'L' level, the connecting point of the capacitor 11 and the diode 12 becomes a negative potential. Thus, the diode 12 is turned OFF, a diode 13 is turned ON to start charging negative charge in a capacitor 14. This cycle is repeated to produce a negative voltage at the output voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a positive voltage-to-negative voltage conversion circuit that can be used when a negative voltage is required in a circuit device or the like to which only positive voltage is supplied.

Conventional technology In recent years, with the miniaturization and weight reduction of circuit devices, switching power supply circuits using coils and transformers are being used when creating a negative voltage from the supply voltage and the negative current capacity only needs to be as small as several tens of mÅ or less. Instead, a positive voltage-to-negative voltage conversion circuit mainly composed of diodes and capacitors is increasingly used.

A conventional positive voltage-negative voltage conversion circuit will be described below with reference to the drawings. 2 and 3 are block diagrams of conventional positive voltage-negative voltage conversion circuits.
In the figure, reference numeral 1 is a square wave oscillation circuit, which is composed of a square wave oscillation section 20 and two bipolar transistors forming an output stage. Both transistors 2a, 3? It is taken out from the emitter connection point of L. On the other hand, in Fig. 3,
The output of the square wave oscillation circuit 1 is taken out from the connection point between the emitter of the NPN transistor 2b and the collector of the MPN transistor 3b. One end of the first capacitor 4 is connected to the output of the square wave oscillation circuit 1, and a first diode 5 is connected between the other end and the ground, and the output terminal -v
A second diode e is connected between the Further, a second capacitor 7 is connected between the output terminal -vo and the ground.

The operation of the positive voltage-negative voltage conversion circuit configured as above will be explained with reference to FIG. 4.

4(?L) is the output voltage waveform of the square wave oscillation circuit 1, FIG. 4(b) is the voltage waveform at the connection point between the first capacitor 4 and the first diode 5, and FIG. (C) is the voltage waveform of the output voltage -vo.

First, when the output of the square wave oscillation circuit 1 is "H", the charging current of the square wave oscillation circuit 1 is the first capacitor 4,
It flows through the first diode 5 to ground. At this time, if the forward voltage drop of the diode is V, the first capacitor 4 is charged to V yaw VD, as shown in Fig. 4 ('b
), the potential at the connection point between the first capacitor 4 and the first diode 5 is V. Next, when the output of the square wave oscillation circuit 1 is inverted to "L" level vL, the connection point between the first capacitor 4 and the first diode 5 is as shown in FIG. 4(b).
As shown in , since the potential becomes negative as VD-(vH-vL), the first diode 5 is turned off and the second diode 6 is turned off.
is turned on, and charging of the second capacitor 7 with negative charge begins as shown in FIG. 4(C). Next, if the output of the square wave oscillation circuit 1 is inverted to the "H" level vH again, the first
Since the diode 5 is turned on, the potential at the connection point between the first capacitor 4 and the first diode 5 becomes V, and the second
Since the diode 6 is turned off, the negative charge charged in the second capacitor 7 is stored. By repeating the above cycle, a negative voltage is extracted as shown in FIG. 4(C). At this time, the output voltage is -v.

is the value shown in equation (1).

-v. =-(vH-vL-2V,) −・−・−・・
-. (1) However, when the output configuration of the square wave oscillation circuit is as shown in Figure 2, if the voltage drop in the term direction between the emitter and pace of the transistor is vBK, then V□ is the (2)
(2) cannot be lower than the voltage shown in equation (3).

vn = vcc −vBx ”・−
−0v−L=vs x・”
--(3) vCC" supply positive voltage Therefore, the output voltage -vo is -4o=-(V,.-2"/B!-2V, )z-(
Vo. -4V, )...(4) There was a problem in that a value higher than -VC6 by only 4V could be obtained.

Furthermore, the temperature coefficient of the output voltage -vo also has a relatively large value, as shown in equation (5).

2V0 2V.

−−= 4−z8 mv/'C・・・・・・・・・ (
2T 2T Also, the output configuration of the square wave oscillation circuit is shown in Fig. 3.
! -woT' respectively have values shown in the following formulas.

V=V −V HCCBE ・・・・・・・・・ (
6) VL=VCx(sat)z o −
--(7) Vox(sat): ) Emitter-collector saturation voltage of transistor 2V.

The output "force sense pressure -v" and its temperature coefficient -2T are not improved compared to equations (4) and (5), respectively.
The problem is that it shows a relatively high value.

Problems to be Solved by the Invention In the conventional circuit configurations shown in FIGS. 2 and 3, negative voltage output values of -v0° can only obtain values as high as 4vI and 3v, respectively. and their temperature coefficients are approximately 8 my/℃.

There was a problem in that it showed a relatively high value of about 61 nv/°C.

The present invention has been made in view of these points, and is a positive voltage-to-negative voltage conversion circuit that can obtain a much lower negative voltage output value than conventional circuits with a simple circuit configuration, and also has a small temperature coefficient. is intended to provide.

Means for Solving the Problems In order to solve the above problems, the present invention provides a square wave oscillation circuit, a first co/capacitor having one end connected to the output end of the square wave oscillation circuit,
a first diode connected between the other end of the first capacitor and a ground; a first diode connected between the first capacitor and the first ground;
a second diode connected between the connection point of the diode and the output terminal, and a second capacitor connected between the output terminal and ground, and the output circuit of the square wave oscillation circuit is connected to a PMO3FET and an NMO3FET. This is the complementary structure of .

Effect: With the above-described configuration, the present invention extracts the output of the square wave oscillation circuit from the MO3FIET regardless of the "H" level or "L" level of the oscillation waveform, so the negative voltage output value is lower than that of the conventional circuit. In addition, it is possible to obtain an output with an improved temperature coefficient of negative output voltage.

EXAMPLES Hereinafter, examples of the present invention will be described with reference to the drawings.

FIG. 1 shows a configuration diagram of a positive voltage-negative voltage conversion circuit in one embodiment of the present invention. In FIG. 1, 8 is a square wave oscillation circuit, which includes a square wave oscillation section 21 and a PMO3FET 9 that constitutes an output stage.

It is composed of 10 NMo3FETs. One end of a first capacitor 11 is connected to the output of the square wave oscillation circuit 8, a first diode 12 is connected between the other end and the ground, and a second diode is connected between the output terminal -vo and the other end. diode 1
Connect 3. Further, a second capacitor 14 is connected between the output terminal -vo and the ground.

The operation of the positive voltage-negative voltage conversion circuit of this embodiment configured as described above will be explained below.

First, when the output of the square wave oscillation circuit 8 is at "H" level V, the charging current of the square wave oscillation circuit 8 is transferred to the first capacitor 11.
, flows through the first diode 12 to ground. At this time, the first capacitor 11 is charged to VH-V, and the potential at the connection point between the first capacitor 11 and the first diode 12 becomes V. Next, when the output of the square wave oscillation circuit 8 is inverted to the L level vL, the connection point between the first capacitor 11 and the first diode 12 becomes V, = (V
□-V, ), so the first diode 12
is turned off, the second diode 13 is turned on, and charging of the second capacitor 14 with negative charge begins. Next, when the output of the square wave oscillation circuit 8 is inverted to the "H" level vH again, the first diode 12 is turned on, so that the potential at the connection point between the first capacitor 11 and the first diode 12 becomes V . As a result, the second diode 13 turns off, so
The negative charge charged in the second capacitor 14 is stored. By repeating the above cycle, a negative voltage is extracted as the output voltage, and its value becomes the value shown in equation (1).

At this time, the on-resistance of P and NMo5FETs 9 and 10 is adjusted to the charging/discharging current to the first capacitor 11 of R0n1. Then, vl (and vL) have the values shown in equations (10) and (11), respectively.

vH=v,. −■.・Ron...
・・・・・・ (100VL=IC-Ron, ・・・・・・
...(11) By the way, the charging/discharging current I0 to the first capacitor 11 is such that the output of the square wave oscillation circuit 8 varies from v8 to vL.
When the voltage changes from vL to v8, the current flows transiently, but becomes zero when the first capacitor 11 is sufficiently discharged. Therefore, after the first capacitor 11 is sufficiently charged and discharged, the equations (10) and (11) are
The values are shown in equation (12) and equation (13), respectively.

V□=vcc・・・・・・・・・
・ (12) vL=o ・・・・
...... (13) Therefore, the output voltage -vo is -v0=-(vo.-2v,) ......
(14) In addition, a lower value can be extracted as the output voltage than the value shown in equation (4) or equation (8) shown in the conventional example.

In addition, the temperature coefficient of the output voltage is:
2T, and the formula (5) shown in the conventional example or the formula (9)
) It is possible to obtain a temperature coefficient of the output voltage that is smaller than the value shown in the equation.

Effects of the Invention As is clear from the above explanation, the present invention outputs the output of the square wave oscillation circuit to the "H" level of the oscillation waveform.

・Since it is taken out from the MOSFET regardless of the L level, the extremely simple circuit configuration allows it to be used as a negative voltage output.
It is possible to obtain a lower value than the conventional circuit, and it is also possible to obtain an improved temperature coefficient of the output negative voltage.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a positive voltage to negative voltage conversion circuit according to an embodiment of the present invention, FIGS. 2 and 3 are block diagrams of a conventional positive voltage to negative voltage conversion circuit, and FIG. 4 is a block diagram of a positive voltage to negative voltage conversion circuit. FIG. 3 is an operation waveform diagram of the negative voltage conversion circuit. 8... Square wave oscillation circuit, 9... PMO
3FET. 10...NMO3FET, 11.14...
... Capacitor, 12.13 ... Diode, 21 ... Square wave transmitter. Name of agent: Patent attorney Toshio Nakao and 1 other person8-
Is it a single sword-shaped circuit? ---PMO5FET 10-NMO5FET //, /4-1-Coactive

Claims (1)

[Claims] a square wave oscillation circuit, a first capacitor having one end connected to its output terminal, a first diode connected between the other end of the first capacitor and ground, the first capacitor and the first capacitor; a second diode connected between the connection point of the diode and the output terminal, and a second capacitor connected between the output terminal and ground, and the output circuit of the square wave oscillation circuit is connected to a PMOSFET. NMOSFE
A positive voltage-negative voltage conversion circuit with a complementary structure of T.