JPH10225109A - Positive/negative voltage output dc-dc converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a positive/negative voltage output DC-DC converter with a fewer number of components. SOLUTION: Based on the frequency signal S60 from a converter control part 60, a transistor 43 switches a coil 42 and a ground G on and off with high frequency. The switching of the transistor 43 gives a diode 44 a voltage V1 which oscillates in a positive region. Then, the voltage V1, changed into a constant voltage by the rectification with the diode 44 and filtering with a capacitor 45, is outputted as a positive DC output voltage Vout1 from an output terminal OUT1. A capacitor 48, whose one end is connected to the collector of the transistor 43, outputs from the other end a voltage V2 which oscillates in a negative region. This voltage V2, changed into a constant voltage by the rectification with the diode 50 and filtering with a capacitor 51, is outputted as a negative DC output voltage Vout2 from an output terminal OUT2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positive / negative voltage output DC-DC converter for generating and outputting positive and negative DC output voltages from a DC input voltage (hereinafter simply referred to as DC-DC converter).

[0002]

2. Description of the Related Art Conventionally, techniques in such a field include:
For example, there is one described in the following literature. Literature; "1994 Linear Data Book" 3 (199
4), Linear Technology P.4-442 FIG. 2 is a circuit diagram of a conventional DC-DC converter.
This DC-DC converter converts a DC input voltage Vin applied to an input terminal IN into a positive DC output voltage Vout.
1 to generate a negative DC output voltage Vout2 and output it from two output terminals OUT1 and OUT2. A capacitor 1 connected between the input terminal IN and the ground G
And two coils 2, 3 whose one ends are connected in parallel to the input terminal IN.

[0005] The other end of the coil 2 is connected to the collector of the transistor 5 and the anode of the diode 5. The emitter of the transistor 3 is connected to the ground G. One electrode of a smoothing capacitor 6 is connected to the cathode of the diode 5. The connection node N between the diode 5 and the capacitor 6 is connected to the output terminal OUT1. The other electrode of the capacitor 6 is connected to the ground G. The cathode of this diode and the ground G
Are connected in parallel with the capacitor 6. On the other hand, the other end of the coil 3 is connected to the collector of the transistor 9, the anode of the diode 10, and one electrode of the capacitor 11. The emitter of the transistor 9 is connected to the ground G.
Two series resistors 12 and 13 are connected between the cathode of the diode 10 and the ground G. The other electrode of the capacitor 11 is connected to the anode of the diode 14 and the cathode of the diode d15. The cathode of the diode 14 is connected to the ground G. A smoothing capacitor 16 is connected between the anode of the diode 15 and the ground G, and the anode of the diode 15 is connected to the output terminal OUT.

A control unit 20 is connected to a connection node N1 between the resistors 7 and 8, and a control unit 30 is connected to a connection node N2 between the resistors 12 and 13. Control unit 20
Is the voltage of the connection node N1 of the resistors 7 and 8 and the reference voltage Vr
And an error amplifier 21 for amplifying the error
An oscillator 22, a PWM (Pulse width Modulation) controller 23 provided on the output side of the amplifier 21 and the oscillator 22, and a driver 24 for driving an output signal of the controller 23 and supplying the output signal to the base of the transistor 4. Have. Similarly, the control unit 30 controls the resistors 12, 1
3, an error amplifier 31 for comparing the voltage of the connection node N2 with the reference voltage Vr and amplifying the error, and an oscillator 32
A PWM controller 33 provided on the output side of the amplifier 31 and the oscillator 32; and a driver 34 for driving an output signal of the controller 33 and supplying the output signal to the base of the transistor 9.

In this DC-DC converter, the error amplifier 21 amplifies the difference between the reference voltage VR and the voltage at the connection node N 1, and supplies the error amplified signal S 1 to the PWM controller 23. The error amplifier 31 amplifies the difference between the reference voltage VR and the voltage of the connection node N2, and generates an error amplified signal S
2 is given to the PWM controller 33. Each of the PWM controllers 23 and 33 generates a square wave signal whose frequency is the same as the oscillation frequency of the oscillators 22 and 32 and whose pulse width changes according to the signals S1 and S2.
4, 34 drive the respective square wave signals and control signals S3, S4
Generate These control signals S3 and S4 are applied to the bases of transistors 4 and 9. Each transistor 4, 9
Performs high-frequency switching by the control signals S3 and S4, respectively. The DC input voltage Vin applied to the input terminal IN is applied to the collector of the transistor 4 via the coil 2. By the switching of the transistor 4,
Diode 5 is converted into voltage Va that oscillates in the positive region.
To the anode. The voltage Va is smoothed by the rectification of the diode 5 and the charging of the capacitor 6, and a positive constant voltage having a voltage value of Vout1 is generated. This constant voltage is output from the output terminal OUT1 as a positive DC output voltage. The DC input voltage Vin is supplied to the collector of the transistor 9 via the coil 3. Voltage V oscillating in the positive region due to switching of transistor 9
b. This voltage Vb is converted to a voltage Vc oscillating in a negative region via the capacitor 11. Voltage Vc
Is smoothed by the rectification of the diode 15 and the discharge of the capacitor 16, and a negative constant voltage having a voltage value of Vout2 is generated. This constant voltage is output from the output terminal OUT2 as a negative DC output voltage.

[0006]

However, the conventional DC-DC converter has the following problems.
The DC-DC converter has a large number of circuit components, which not only increases the cost, but also has a problem that integration is difficult and a substrate mounting area increases.

[0007]

In order to solve the above-mentioned problems, the present invention generates positive and negative DC output voltages from a DC input voltage supplied from an input terminal, and generates the generated positive and negative DC output voltages. In a DC-DC converter that outputs an output voltage from a first output terminal and a second output terminal,
It has the following configuration. That is, the DC-DC of the present invention
The converter has one end connected to the input terminal and generates a current having an integrated waveform with respect to an applied voltage.The other end of the coil is connected to the other end of the coil based on a given frequency signal. A switching element that turns on and off a voltage that oscillates in a positive region by intermittently passing a DC input voltage, a first diode for rectification having an anode connected to the switching element, First
And a first capacitor that generates the positive DC output voltage by smoothing the voltage of the cathode of the diode and supplies the same to the first output terminal. Furthermore, this DC-
The DC converter includes a second diode for rectification having a cathode connected to the ground, a connection between the switching element and an anode of the second diode, and a connection to an anode of the second diode. A second capacitor for outputting a voltage oscillating in a negative region from a node, a third diode for rectification having a cathode connected to the connection node, and a smoothing of a voltage at an anode of the third diode. A third capacitor that generates the negative DC output voltage and supplies the negative DC output voltage to the second output terminal.

According to the present invention, DC-DC
Since the converter is configured, a DC input voltage is input to the input terminal, but is converted by the switching element into a voltage that oscillates in a positive region. The voltage oscillating in the positive region is rectified by the first diode and smoothed by the first capacitor to generate a positive DC output voltage.
On the other hand, a voltage oscillating in a negative region is generated by the second diode and the second capacitor. The voltage oscillating in this negative region is rectified by the second diode and smoothed by the third capacitor to generate a negative DC output voltage.
Therefore, the above problem can be solved.

[0009]

FIG. 1 is a circuit diagram of a DC-DC converter showing an embodiment of the present invention. This DC-DC
The converter generates a positive DC output voltage from the DC input voltage Vin applied to the input terminal IN and outputs it from the first output terminal OUT1, and generates a negative DC output voltage to generate a second output terminal. It has a function of outputting from OUT2, and includes a capacitor 41 connected between the input terminal IN and the ground G, and a coil 42 having one end connected to the input terminal IN. At the other end of the coil 42,
The collector of the transistor 43 which is a switching element is connected. The emitter of the transistor 43 is connected to the ground G. The collector of the transistor 43 is connected to the anode of a first diode 44 for rectification, and the cathode of the diode 44 is connected to one electrode of a first capacitor 45 for smoothing. A connection node N11 between the capacitor 45 and the diode 44 is connected to the output terminal OUT1, and a series resistor 46,
47 is connected to the ground G.

[0010] The collector of the transistor 43 is further connected to one electrode of a second capacitor 48. The other electrode of the capacitor 48 is connected to the anode of the second diode 49 for rectification and the cathode of the third diode 50 for rectification.
The cathode of the diode 49 is connected to the ground G. One electrode of a third smoothing capacitor 51 is connected to the anode of the diode 50. The other electrode of the capacitor 51 is connected to the ground G.
The connection node N12 between the capacitor 51 and the diode 50 is connected to the output terminal OUT2. A resistor 46 connected in series between the node N11 and the ground G
The connection node N13 between the resistor 47 and the resistor 47 is connected to the converter control unit 60. Converter control unit 60 includes:
An error amplifier 61 amplifies the difference between the reference voltage Vr and the voltage at the node N13, and an oscillator 62. The output sides of the error amplifier 61 and the oscillator 62 are connected to the input side of the PWM controller 63.
Is connected to the driver 64. Driver 6
4 is connected to the base of the transistor 43.

FIG. 3 is a voltage waveform diagram in FIG.
The operation of the DC-DC converter will be described with reference to FIG. Here, the input DC voltage Vin and the output voltages Vout1 and Vout2 are | Vin | <| Vout
1 | = | Vout2 |, and the on-state transistor 4
Assuming that the collector-emitter saturation voltage of No. 3 and the forward voltage between the anode and cathode of each diode are 0, FIG.
The operation of is described below. In this DC-DC converter, the error amplifier 61 in the converter control unit 60 amplifies the difference between the reference voltage VR and the voltage of the connection node N13, and supplies the error amplified signal S61 to the PWM controller 63. The oscillator 62 generates a triangular wave frequency signal to
This is given to the controller 63. PWM controller 63
Generates a square wave signal whose frequency is the same as the oscillation frequency of the oscillator 62 and whose pulse width changes in accordance with the signal S61. The driver 64 drives the square wave signal and supplies the square wave signal to the base of the transistor 43 as a frequency signal S60.

When the DC input voltage Vin is input from the input terminal IN, the DC input voltage Vin is supplied to the collector of the transistor 43 via the coil 42. On the other hand, the transistor 43 to which the signal S60 has been applied turns on the signal S60.
, The capacitor 41 and the coil 42 store and release energy, and the coil 42 flows a current obtained by integrating the applied voltage. In a period in which the transistor 43 shown by T1 in FIG. 3 is off, the voltage V2 output from the collector of the transistor 43 has a voltage value of Vout1 volt, and the capacitor 4
The voltage V2 on the electrode on the connection node N12 side of No. 8 becomes 0 volt. At this time, the capacitor 48 is charged with Vout1 volt. Subsequently, a section indicated by T2 in FIG. When transistor 43 turns on, voltage V1 drops to 0 volts. In the section T1, the capacitor 48 is connected to Vout
Since the battery is charged to 1 volt and the diode 49 is off, the voltage V2 also drops and Vout2 (= −V
out1) volts. Such an operation is repeated, and the voltage V1 oscillates in a positive region and the voltage V2 oscillates in a negative region. Rectification by diode 44 and capacitor 4
By the smoothing of 5, a constant DC positive DC output voltage is generated and output from the output terminal OUT1. The rectification by the diode 50 and the smoothing of the capacitor 46 generate a constant DC negative DC output voltage, which is output from the output terminal OUT2. Resistance 4
6, 47 divide the positive DC output voltage,
From the voltage corresponding to the positive DC output voltage,
Return to 1.

As described above, in this embodiment, the voltage V1 oscillating in the positive region and the voltage V2 oscillating in the negative region are generated by utilizing the high-frequency switching of the transistor 43. As compared with FIG.
, One transistor, one diode, two resistors
And the converter control unit is reduced by one, and the DC-D
Cost reduction by reducing the number of components in the C converter, reduction of the substrate mounting area, and the like can be realized. Note that the present invention is not limited to the above embodiment, and various modifications are possible. For example, in FIG. 1, the switching element is configured by the NPN transistor 43, but may be configured by a PNP transistor or another switching element.

[0014]

As described above in detail, according to the present invention, a coil for generating a current having an integral waveform with respect to an applied voltage, and a voltage oscillating in a positive region by intermittently passing an input DC voltage. , A first diode and a first capacitor, a second diode for rectification, a second capacitor for outputting a voltage oscillating in a negative region, a third diode and a third capacitor. With the capacitor of D
Since the C-DC converter is configured, a reduction in cost due to a decrease in the number of components, a reduction in the board mounting area, and the like can be realized.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a DC-DC converter showing an embodiment of the present invention.

FIG. 2 is a circuit diagram of a conventional DC-DC converter.

FIG. 3 is a voltage waveform diagram in FIG.

[Explanation of symbols]

 42 coil 43 transistor (switching element) 44 first diode 45 first capacitor 48 second capacitor 49 second diode 50 third diode 51 third capacitor 60 converter control unit IN input terminal OUT1 first output Terminal OUT2 Second output terminal

Claims (1)

[Claims] 1. A positive and negative DC output voltage is generated from a DC input voltage applied to an input terminal, and the generated positive and negative DC output voltages are respectively output from a first output terminal and a second output terminal. In a positive / negative voltage output DC-DC converter for outputting, one end is connected to the input terminal, and a coil that generates a current having an integral waveform with respect to an applied voltage; A switching element that turns on and off the other end of the coil and ground based on the current and outputs a voltage that intermittently passes a DC input voltage and oscillates in a positive region; and a rectifier having an anode connected to the switching element. A first diode for generating a positive direct current output voltage by smoothing the voltage of the cathode of the first diode and applying the same to the first output terminal A second diode for rectification having a cathode connected to the ground; a second diode for rectification connected between the switching element and an anode of the second diode; and a negative node from a connection node between the second diode and the anode of the second diode. A second capacitor that outputs a voltage that oscillates in a region, a third diode for rectification having a cathode connected to the connection node, and smoothing the voltage of the anode of the third diode to perform the negative operation. And a third capacitor for generating a DC output voltage and supplying the DC output voltage to the second output terminal.