JP2006020426A - Dc/dc converter circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the size and cost of a DC/DC converter of a type that outputs a plurality of voltages, and to improve the conversion efficiency of energy. <P>SOLUTION: This DC/DC converter circuit comprises a voltage variable circuit connected in series with a coil and a switching element that controls the energy discharge of the coil; a plurality of output circuits that are connected between the coil and the switching element and have output controlling switching elements and output voltage monitor means, and a control circuit inputted with each output voltage monitor signal. The control circuit responds to one monitor signal, controls the discharge controlling switching elements and the output controlling switching elements of the output circuit, adjusts output voltages of the output circuits at one control cycle, and sequentially and repeatedly controls the output voltages of the plurality of output circuits in terms of time division by arranging a plurality of the control cycles in terms of time division. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a DC-DC converter capable of outputting two or more different output voltages.

  Conventionally, a coil boosting type DC-DC converter used in an electronic device generally has one coil and a single output voltage.

Recently, however, there has been a need for a device that can obtain a plurality of output voltages with a single DC-DC converter in order to reduce the size of the device.
FIG. 4A is a diagram showing an example of a conventional multiple voltage output type DC-DC converter.
In FIG. 4A, a voltage variable coil 52 and an NPN transistor Tr10 as a switching element are connected in series between power input terminals 50 and 51, and the input terminal 51 is connected to a ground potential (hereinafter abbreviated as GND). The anode side of the diode 54 is connected to the connection point between the coil 52 and the Tr 10, and the cathode side of the diode 54 is connected to the output terminal 56. Resistors 62 and 64 connected in series between the cathode side of the diode 54 and GND constitute output voltage monitoring means, and output voltage monitor signals are output from the connection points of the resistors 62 and 64 to control circuits. 66. Reference numeral 68 denotes a reference frequency signal generation circuit which generates a signal having a reference frequency and sends it to the control circuit 66. The control circuit 66 generates a signal TrCON for controlling conduction / non-conduction of the transistor Tr10 from the monitor signal and the reference frequency signal and applies the signal TrCON to the base electrode of the transistor Tr10.

FIG. 4B is a timing chart for explaining the operation of the DC-DC converter shown in FIG.
In the DC-DC converter of FIG. 4A, current flows from the input terminal 50 to the GND via the voltage variable coil 52 and the transistor Tr10 when the transistor Tr10 is conductive, and the voltage when the transistor Tr10 is nonconductive. The energy stored in the variable coil 52 is supplied to the output terminal 56 via the diode 54. A capacitor (not shown) is connected to the output terminal 56 to store electric power.
When the load connected to the output terminal 56 is light, the monitor signal is a high voltage, and when the load is heavy, the monitor signal is a low voltage. As shown in FIG. 4B, the control circuit 66 responds to the monitor signal so that the duty ratio of the time during which the transistor Tr10 is turned on becomes small at a light load, and the time when the transistor Tr10 is turned on at a heavy load. The TrCON signal is output so that the duty ratio increases. If the duty ratio of the time for which the transistor Tr10 is conductive is reduced, the energy stored in the voltage variable coil 52 is reduced and the output voltage is lowered. If the duty ratio of the time for which the transistor Tr10 is conductive is increased, the voltage is variable. The energy stored in the coil 52 for use increases and the output voltage rises. Thus, the output voltage is stabilized by the feedback system formed by the control circuit 66 and the like.

A regulator 60 is provided between the output terminal 56 and GND. The regulator 60 uses the voltage at the output terminal 56 as a power source, regulates the voltage between the regulator 60 and GND, and outputs the second DC voltage to the output terminal 58.
In this way, the DC-DC converter circuit shown in FIG. 4A is a two-output type DC-DC in which, for example, 15 V is obtained from the output terminal 56 as output A and 10 V is obtained from the output terminal 58 as output B. It is a converter circuit.

The problem with such a two-output type DC-DC converter is that the efficiency is poor.
The inefficiency is due to the use of the regulator 60, and the regulator generally has a large internal energy loss, which causes a problem of poor energy conversion efficiency.

Therefore, it is conceivable to adopt a circuit configuration in which a coil boost type DC-DC converter is provided in parallel without using a regulator, as shown in FIG.
FIG. 5 is a diagram showing an example of a multiple voltage output type DC-DC converter provided with a coil step-up DC-DC converter in parallel.
In FIG. 5, circuit blocks 72 and 74 have the same configuration as the circuit block 70 except the regulator 60 from the circuit diagram of FIG. 4A, and an input terminal 76 is connected to the circuit block 72 and the circuit block 74. ing.
With this configuration, two different output voltages can be obtained from the output terminals 86 and 88 of the circuit blocks 72 and 74, respectively. The voltage value to be output can be set by the respective control circuits 90 and 92. For example, the control circuits 90 and 92 are set so as to obtain 15V from the output terminal 86 as the output A and 10V from the output terminal 88 as the output B. Each can be set by a conventional technique.

Thus, if the configuration as shown in FIG. 5 is adopted, efficiency can be improved as compared with the configuration shown in FIG. 4A, but the problem remains.
The first problem is that the number of parts is increased and the electronic device cannot be reduced in size and cost. The second problem is that the input current flows in both Tr20 and Tr30. The energy loss in Tr30 is added to the energy loss, and there is still a lot of wasted energy in terms of energy conversion efficiency.

As an approximate technique, a stable output voltage DC-DC converter is proposed in Japanese Patent Laid-Open No. 10-150766. This DC-DC converter was invented for the purpose of suppressing the ripple of the output voltage. The first DC-DC converter has two rectification / smoothing circuits, and the output of the first rectification / smoothing circuit is the first. 1, and the output of the second rectifying / smoothing circuit is the input of the second DC-DC converter.
FIG. 1 of Japanese Patent Laid-Open No. 10-150766 describes a circuit diagram of a DC-DC converter, and its configuration is intermediate between FIGS. 4 and 5 of this specification. In addition, since the most difficult coil to integrate in a semiconductor and a large volume are provided for each output, and the transistor of the input part with energy loss is provided for each output, the two attempts to be solved by the present invention It is thought that both problems have not been solved.

JP-A-10-150766

  The problems to be solved are that the conventional multi-voltage output type DC-DC converter is difficult to reduce in size and cost and has poor energy conversion efficiency.

A DC-DC converter circuit according to the present invention is a DC-DC converter circuit that obtains a plurality of output voltages,
The DC-DC converter circuit includes a voltage variable circuit in which a voltage variable coil and a storage / discharge control switching element for controlling energy storage / discharge of the voltage variable coil are connected in series between power input terminals, and the voltage variable A plurality of output circuits connected between the voltage variable coil of the circuit and the storage / discharge control switching element, the output control switching element, output voltage monitoring means for monitoring the output voltage, and an output terminal; A control circuit to which a frequency signal and a monitor signal output from each of the output voltage monitoring means are input. The control circuit corresponds to the monitor signal of one of the output circuits in one control cycle. The conduction voltage between the storage discharge control switching element and the output control switching element of the output circuit is controlled to display the output voltage of the output circuit. Flip thereby adjusted to a value determined because, characterized by dividing and sequentially repeating control time an output voltage of said plurality of output circuits time division manner by plurality of control cycles.

  The storage / discharge control switching element and the output control switching element are transistors.

  Further, a command signal indicating the number of output voltages is input to the control circuit, and in response to the command signal, the number of the output circuits controlled in the control cycle provided in a time-division manner can be selected. It is characterized by.

  Since a plurality of different voltages can be generated with high efficiency by one coil, it is possible to reduce the size, cost, and power consumption of electronic devices.

A voltage variable circuit in which a voltage variable coil and a storage discharge control switching element for controlling energy storage and discharge of the voltage variable coil are connected in series between power supply input terminals; and the voltage variable coil of the voltage variable circuit; A plurality of output circuits connected between the storage / discharge control switching elements and having an output control switching element, output voltage monitoring means for monitoring an output voltage, and an output terminal; a reference frequency signal; and each output voltage monitor And a control circuit to which a monitor signal output from the means is input, and the control circuit corresponds to the monitor signal of the output discharge circuit corresponding to the monitor signal of the output circuit in one control cycle, and the control circuit While controlling the conduction / non-conduction of the output control switching element of the output circuit, the output voltage of the output circuit is adjusted to a predetermined value.該制 and division manner plurality during a control cycle divided and sequentially repeated control when the output voltage of said plurality of output circuits.
In addition, a command signal indicating the number of output voltages is input to the control circuit, and in response to the command signal, the number of the output circuits controlled in the control cycle provided in a time division manner can be selected.

FIG. 1 is a circuit diagram of an embodiment of the DC-DC converter of the present invention, and FIGS. 2 and 3 are timing charts for explaining the operation of the circuit diagram shown in FIG.
In FIG. 1, the example which outputs two types of voltages was shown.

In FIG. 1, a voltage variable coil 12 and an NPN transistor Tr1 serving as a storage / discharge control switching element are connected in series between power input terminals 10 and 11 to which a DC voltage is input to form a voltage variable circuit 13. A collector electrode of an NPN transistor Tr2 which is a first output control switching element for generating a first output voltage A at a connection point between the voltage variable coil 12 and Tr1, and a second output voltage B Is connected to the collector electrode of the NPN transistor Tr3, which is a second output control switching element for generating the first output, and the emitter electrode on the output side of the transistor Tr2 outputs the first voltage A. The emitter electrode connected to the terminal 14 and on the output side of the transistor Tr3 is a second output terminal 16 from which a second voltage B is output. It is connected.
Resistors 22 and 24 connected in series between the emitter electrode side of the transistor Tr2 and GND constitute first monitoring means 18 for creating a monitor voltage signal of the first output voltage A. A first monitor voltage signal is output from 24 connection points and sent to the control circuit 30.
The resistors 26 and 28 connected in series between the emitter electrode side of the transistor Tr3 and the GND constitute second monitor means 20 for generating a monitor voltage signal of the second output voltage B, and the resistors A second monitor voltage signal is output from the connection point 26, 28 and sent to the control circuit 30.
Here, the first output control switching element Tr2, the first monitoring means 18 and the output terminal 14 form a first output circuit, and the second output control switching element Tr3 and the second monitoring means 20 are formed. And the output terminal 16 form a second output circuit.
A reference frequency signal generation circuit 32 generates a signal having a reference frequency and sends it to the control circuit 30. The control circuit 30 creates a signal for controlling conduction / non-conduction of the transistors Tr1, Tr2, Tr3 from the monitor signal and the reference frequency signal and applies them to the base electrodes of the transistors Tr1, Tr2, Tr3.
Further, the control circuit 30 receives a two-output command signal 34 and a single output command signal 36, and the control circuit 30 responds to the command signals 34 and 36 in a first mode for outputting two kinds of voltages; The second mode for outputting one voltage is selected.
Capacitors 40 and 38 are connected to the first output terminal 14 and the second output terminal 16, respectively. These capacitors 40 and 38 function to smooth the output voltage and store power and supply it to the load. Since these capacitors 40 and 38 have a large volume, they are generally mounted externally outside the DC-DC converter package.
The reference frequency signal generation circuit 32 may be provided inside the DC-DC converter, or may be configured to be supplied with a reference frequency signal from an external reference frequency signal generation circuit.

  In FIG. 1, current flows from the input terminal 10 to the voltage variable coil 12 and the input terminal 11 connected to GND via the transistor Tr1 when the transistor Tr1 is conductive, and when the transistor Tr1 is nonconductive, the voltage is variable. The energy accumulated in the coil 12 is supplied to the output terminal 14 or 16 through the transistor Tr2 or the transistor Tr3 which is in a conductive state. The voltage supplied to the output terminals 14 and 16 is stored in the capacitor 40 or 38.

FIG. 2 is a first timing chart for explaining the operation of the DC-DC converter of FIG. 1 and is a diagram for explaining a first mode for outputting two kinds of voltages.
In FIG. 2, the two-output command signal is at the H level and the single output command signal is at the L level, and the output mode is a two-output mode that outputs two kinds of voltages.
The reference frequency signal is a signal sent from the circuit block 32 of FIG. 1 to the control circuit 30, and one cycle of the reference frequency signal is one control cycle, and the control target output is A, B, A for each cycle. , B, and so on in a time-division manner. That is, the control for the output A is performed in the first cycle with respect to the reference frequency, the control for the output B is performed in the second cycle, and the same control is repeated thereafter. When the control target output is A, the control circuit 30 controls the NPN transistor Tr1 which is a storage discharge control switching element and the NPN transistor Tr2 which is a first output control switching element. When the control target output is B, The control circuit 30 controls the NPN transistor Tr1 that is a storage discharge control switching element and the NPN transistor Tr3 that is a second output control switching element.

  That is, in the period t4 when the output to be controlled is A, the duty ratio t1 / t4 during which the transistor Tr1 becomes conductive is determined by the first monitor signal, and the voltage variable coil 12 from the input terminal 10 during the period t1. A current flows through the GND via the transistor Tr1 and energy is accumulated in the voltage variable coil 12, and the transistor Tr2 becomes conductive in synchronization with the transistor Tr1 becoming non-conductive in the period t2 following the period t1, and the voltage is variable. The energy stored in the coil 12 is sent to the output terminal 14 via the transistor Tr2, stored in the capacitor 40, and supplied to a load (not shown). During this time, the transistor Tr3 is controlled to maintain a non-conductive state.

  Further, in the period t3 when the output to be controlled is B, the duty ratio, t5 / t3, during which the transistor Tr1 is turned on is determined by the second monitor signal, and the voltage variable coil 12 from the input terminal 10 during the period t5, A current flows through GND through the transistor Tr1 and energy is accumulated in the voltage variable coil 12, and the transistor Tr3 is turned on in synchronization with the transistor Tr1 being turned off in the period t6 following the period t5, and the voltage is changed. The energy stored in the working coil 12 is sent to the output terminal 16 via the transistor Tr3, stored in the capacitor 38, and supplied to a load (not shown). During this time, the transistor Tr2 is controlled to maintain a non-conductive state.

  That is, a control cycle for controlling the transistor Tr1 which is a switching element for storage / discharge control and the transistor Tr2 which is a first output control switching element, and the transistor Tr1 which is a storage / discharge control switching element and the second output control switch A control cycle for controlling the transistor Tr3, which is a switching element, is alternately provided in a time division manner.

During this time, when the load connected to the output terminals 14 and 16 is light, the first and second monitor signals are at high voltages, and when the load is heavy, the first and second monitor signals are at low voltages. Become. In response to the monitor signal, the control circuit 30 controls Tr1 so that the duty ratio of the time during which the transistor Tr1 is turned on becomes small at a light load, and the duty ratio at the time when the transistor Tr1 is turned on at a heavy load. . That is, when the load connected to the output terminal 14 is light, the duty ratio t1 / t4 during which the transistor Tr1 becomes conductive in the period t4 decreases, and increases when the load is heavy. Further, when the load connected to the output terminal 16 is light, the duty ratio, t5 / t3, during which the transistor Tr1 is turned on in the period t3 is reduced, and is increased when the load is heavy.
If the duty ratio of the time for which the transistor Tr1 is conductive is reduced, the energy stored in the voltage variable coil 12 is reduced and the output voltage is lowered. If the duty ratio of the time for which the transistor Tr1 is conductive is increased, the voltage is variable. The energy stored in the working coil 12 increases and the output voltage rises. Thus, the output voltage is stabilized by the feedback system formed by the control circuit 30 and the like.

  The output voltage A of the output terminal 14 is, for example, 15V, and the output voltage B of the output terminal 16 is, for example, 10V. The output voltage A and the output voltage B can be arbitrarily set to different voltage values. In the period t4 for obtaining the voltage A, the time t1 for turning on the transistor Tr1 is set so that the necessary power can be supplied. In the period t3 for obtaining the voltage B, the time t5 for turning on the transistor Tr1 is set so that the necessary power can be supplied. To do.

As described above, in the DC-DC converter circuit of the present invention, the control circuit 30 corresponds to the first monitor voltage signal, the transistor Tr1 serving as the storage / discharge control switching element, and the first output control switching element. The transistor Tr2 is controlled synchronously, and the transistor Tr1 which is a storage discharge control switching element and the transistor Tr3 which is a second output control switching element are controlled synchronously in response to the second monitor voltage signal. is doing.
Further, the control circuit 30 performs time-division control of the storage / discharge control switching element and the first output control switching element, and control of the storage / discharge control switching element and the second output control switching element. It is repeated alternately.
For this reason, it can be configured such that two different output voltages can be generated by a booster circuit constituted by a single voltage variable coil 12 and transistor Tr1. With such a circuit configuration and control method, a problem energy loss can be suppressed to the same energization time of the transistor Tr1 as that of the conventional single output DC-DC converter, and can be minimized. In addition, since a plurality of different voltages can be obtained with high efficiency by a single booster circuit, a remarkable effect can be achieved in reducing the size and cost of the device.

Although the example circuit of FIG. 1 shows an example in which two different output voltages are obtained, it is of course possible to obtain a larger number of output voltages by using the same time-division control method. is there.
In addition, although the output voltage monitor signal has been shown as an example obtained by resistance division, there are a method of using an active element such as an operational amplifier, a method of directly feeding back the output voltage to the control circuit, and processing in the control circuit, etc. The present invention is not limited to these means.

FIG. 3 is a second timing chart for explaining the operation of the DC-DC converter of FIG. 1, and is a diagram for explaining a second mode for outputting one voltage.
In FIG. 3, the 2-output command signal is at L level and the single output command signal is at H level, and the output mode is a single output mode that outputs one voltage.
In this mode, the control target output is A over the entire period of the reference frequency signal, and the transistor Tr3 for the output B is maintained in a non-conductive state. That is, the mode is a mode in which the transistor Tr1 which is a storage / discharge control switching element and the transistor Tr2 which is a first output control switching element are continuously controlled.
In this second mode, for each period T ′ of the reference frequency signal, the duty at which the transistor Tr1 becomes conductive, t7 / T ′, is determined by the first monitor signal, and the voltage variable coil is input from the input terminal 10 during the period t7. 12. Current flows through GND through the transistor Tr1 and energy is accumulated in the voltage variable coil 12. The transistor Tr2 becomes conductive in synchronization with the transistor Tr1 becoming non-conductive in the period t8 following the period t7. The energy stored in the voltage variable coil 12 is sent to the output terminal 14 via the transistor Tr2, stored in the capacitor 40, and supplied to a load (not shown). This operation is repeated in each subsequent cycle, and the transistor Tr3 maintains a non-conductive state during the single output mode.

Thus, in the DC-DC converter circuit of the present invention, the output voltage can be arbitrarily switched between the single output mode and the multiple output mode. In this case, command signals 34 and 36 are given to the control circuit 30, and control contents are switched inside the control circuit 30 based on the command signals 34 and 36.
When the two-output mode as shown in FIG. 2 is used, the switching cycle for obtaining each output is halved, whereas when the single-output mode is set, the circuit that does not output is controlled. Since there is no need, the selected output can be controlled in a full cycle. Therefore, a remarkable effect is exhibited when the specific load is particularly heavy.

  In the present embodiment, an example is shown in which two or one voltage is obtained from a DC-DC converter that can output two kinds of voltages by a command signal. However, various kinds of voltages can be outputted by the same method. Of course, it is possible to select the DC-DC converter so that an arbitrary number of voltages can be obtained by a command signal.

  Further, in this embodiment, an example in which an NPN transistor is used as a storage / discharge control switching element and an output control switching element has been shown. However, each switching element is not limited to a PNP transistor, a field effect transistor (FET), etc. A switching element can be used.

1 is a circuit diagram of an embodiment of a DC-DC converter according to the present invention. It is a 1st timing chart explaining operation | movement of the DC-DC converter by this invention. It is a 2nd timing chart explaining operation | movement of the DC-DC converter by this invention. It is the figure which showed an example of the conventional multiple voltage output type DC-DC converter. It is the figure which showed the example of the multiple voltage output type DC-DC converter which provided the coil boost type DC-DC converter in parallel.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10, 11 Power supply input terminal 13 Voltage variable circuit 12 Voltage variable coil Tr1 Storage / discharge control switching element Tr2, Tr3 Output control switching element 18, 20 Output voltage monitoring means 30 Control circuit 34, 36 Command signal 14, 16 Output terminal 32 Reference frequency signal generation circuit 38, 40 Capacitor 22, 24, 26, 28 Resistance

Claims (3)

A DC-DC converter circuit for obtaining a plurality of output voltages,
The DC-DC converter circuit includes:
A voltage variable circuit in which a voltage variable coil and a storage / discharge control switching element for controlling energy storage / discharge of the voltage variable coil are connected in series between power input terminals;
A plurality of output control switching elements, output voltage monitoring means for monitoring the output voltage, and output terminals, connected between the voltage variable coil of the voltage variable circuit and the storage / discharge control switching element. An output circuit;
A control circuit to which a reference frequency signal and a monitor signal output from each output voltage monitoring means are input;
The control circuit controls conduction / non-conduction between the storage / discharge control switching element and the output control switching element of the output circuit in response to a monitor signal of the one output circuit in one control cycle, and the output A DC-DC characterized in that the output voltage of the circuit is adjusted to a predetermined value, and a plurality of control cycles are provided in a time division manner so that the output voltages of the plurality of output circuits are sequentially and repeatedly controlled in a time division manner. Converter circuit.   2. The DC-DC converter circuit according to claim 1, wherein the storage discharge control switching element and the output control switching element are transistors. A command signal indicating the number of output voltages is input to the control circuit,
3. The DC-DC converter circuit according to claim 1, wherein the number of the output circuits to be controlled in the control cycle provided in a time division manner can be selected in response to the command signal.

Images