KR20090102949A - Dc/dc converter with multi-output - Google Patents

Abstract

PURPOSE: A multi-output DC/DC converter is provided to reduce the loss of the power by performing a zero current switching control of an output terminal in synchronization with the switching signal of a power converter. CONSTITUTION: A switch switches an input DC power alternatively and converts the DC power into the AC power. A first transformer(200) includes a single transformer. The single transformer transforms the AC power from the switch into the first power with a voltage level according to a turn ratio. A second transformer(300) includes the single transformer magnetically independent of the first transformer. The single transformer transforms the AC power from the switch into the second power with the voltage level according to the turn ratio. A first rectifier(400) rectifiers the first power from the first transformer and outputs the first DC power. A second rectifier(500) rectifies the second power from the second transformer and outputs the second DC power by switching the rectified power. A controller(600) is synchronized with the switching of the switch and controls the switching of the second rectifier.

Description

Multi-Output DC / DC Converters {DC / DC CONVERTER WITH MULTI-OUTPUT}

The present invention relates to a multiple output DC / DC converter, and more particularly, to a multiple output DC / DC converter for controlling switching of the rectifier stage in synchronization with a switching signal used for power conversion without using a step-down chopper circuit for the output rectifier stage. It is about.

BACKGROUND OF THE INVENTION Power supply devices, particularly DC / DC converters, are conventionally used for information appliances such as personal computers, home electronic products such as air conditioners, audio and visual devices, and the like.

Such a DC / DC converter may provide a plurality of output power sources depending on the electronic product applied thereto.

A general multi-output DC / DC converter converts input DC power into AC power through a single transformer, and rectifies it again to output a plurality of DC power. However, in general multi-output DC / DC converter, if the voltage level of one DC power among a plurality of DC powers is changed by a single transformer, cross-regulation is not maintained because it affects the other DC power. There is this. For this purpose, multiple output DC / DC converters with step-down chopper circuits are used.

1 is a block diagram of a conventional multi-output DC / DC converter.

Referring to FIG. 1, the conventional multi-output DC / DC converter alternately switches an input DC power Vin to an AC power by switching the switching unit 11, and the converted AC power is converted to the primary winding of the single transformer 12. To L1).

The first and second secondary windings L2 and L3 transfer AC power to the first and second rectifiers 13 and 14 according to a preset winding ratio with the primary winding L1, and the first and second rectifiers 13 and 14 rectify AC power to output DC power.

At this time, the first rectifier 13 outputs the first DC power supply Vs, and the second rectifier 14 transmits the DC power to the step-down chopper circuit 15. The step-down chopper circuit 15 switches a DC power supply from the second rectifying unit 14 under the control of the controller 15a to output a second DC power supply Va having a voltage level lower than that of the DC power supply. .

The step-down chopper circuit 15 mentioned above is comprised from the switch S, the freewheeling diode D, and the filter L. As shown in FIG.

Accordingly, the conventional multi-output DC / DC converter has a problem that the power conversion efficiency is lowered by re-converting the power again by the step-down chopper circuit 15 described above after the primary power conversion, the step-down configured as described above There is a problem in that the number of parts is increased by the chopper circuit 15 to increase the manufacturing cost.

In order to solve the above problems, an object of the present invention is to provide a multi-output DC / DC converter for controlling the switching of the rectifier stage in synchronization with the switching signal used for power conversion without using the step-down chopper circuit in the output rectifier stage. will be.

In order to achieve the above object, one technical aspect of the present invention is a switching unit for alternating switching the input DC power to an AC power source, and the voltage level according to a predetermined turns ratio of the AC power from the switching unit A first converter having a single transformer for converting to a first power source having a voltage; and converting the AC power from the switching unit into a second power source having a voltage level according to a preset turns ratio, A second converter having a single independent transformer; a first rectifier for rectifying the first power from the first converter and outputting a first DC power; and the second power from the second converter. A second rectifying unit configured to rectify and switch the rectified power to output a second DC power supply, and the second rectifying unit in synchronization with the switching of the switching unit. In that it comprises a control unit for controlling the switching is to provide a multi-output DC / DC converter according to claim.

According to one technical aspect of the present invention, the first and second switching for controlling the alternating switching of the switching unit according to the voltage level of the first DC power supply by receiving the first DC power supply from the first rectifying unit A main switching controller for providing a signal, a signal generator for generating a triangular wave signal synchronized with the first and second switching signals from the main switching controller, a voltage level of the second DC power supply from the second rectifying unit; It may include an output switching controller for controlling the switching of the second rectifier according to the comparison result between the reference voltage set in advance and the triangular wave signal from the signal generator.

According to one technical aspect of the present invention, the signal generator comprises a pulse transformer delivering pulses of the first and second switching signals from the main switching controller, and the first and the first from the signal synchronizing transformer. It may include a triangular wave generation circuit for generating a clock signal at the dead time of the two switching signal and for generating the triangular wave signal in accordance with the clock signal.

According to one technical aspect of the present invention, the triangular wave generation circuit may generate a clock signal having a high signal at the dead time of the first and second switching signals.

According to one technical aspect of the present invention, the triangular wave generation circuit may generate a clock signal having a low signal at a dead time of the first and second switching signals.

According to one technical aspect of the present invention, the output switching controller comprises a comparison element for comparing the voltage level of the second DC power supply and the voltage level of the reference voltage, and the second according to a comparison result from the comparison element. It may include an output switching circuit for providing a third switching signal for controlling the switching of the rectifier.

According to one technical aspect of the present invention, the first converter further comprises a first resonant capacitance for charging and discharging the switched power, a first resonant inductor for charging the switched energy, and a first magnetizing inductor in an LLC manner. Can resonate.

According to one technical aspect of the present invention, the second converter further comprises a second resonant capacitance for charging and discharging the switched power, a second resonant inductor for charging the switched energy, and a second magnetization inductor in an LLC manner. Can resonate.

According to one technical aspect of the present invention, the multiple output DC / DC converter may further include a power factor correction unit for rectifying commercial AC power and power factor correction of the rectified power to provide the input DC power.

According to the present invention, since the switching of the output stage is controlled in synchronization with the switching signal of the power conversion stage, the step-down chopper circuit used in the conventional multi-output DC / DC converter becomes unnecessary, and thus the parts of the step-down chopper circuit of the step-down chopper circuit are required. There is an effect of reducing the manufacturing cost corresponding to the number, and the zero current switching control of the output stage in synchronization with the switching signal of the power conversion stage has the effect of reducing the power loss due to switching loss and conduction loss of the step-down chopper circuit.

1 is a block diagram of a conventional multiple output DC / DC converter.

2 is a block diagram of a multi-output DC / DC converter of the present invention.

Fig. 3 is a block diagram showing another embodiment of the power conversion unit employed in the multiple output DC / DC converter of the present invention.

4 (a), (b) and (c) are diagrams showing embodiments of the first rectifying section employed in the multiple output DC / DC converter of the present invention.

5 (a), 5 (b) and 5 (c) are diagrams showing embodiments of the second rectifying unit employed in the multiple output DC / DC converter of the present invention.

6A and 6B are diagrams showing embodiments of a triangular wave generating circuit employed in a multiple output DC / DC converter of the present invention.

FIG. 7 is a signal waveform diagram of a triangular wave generating circuit shown in FIGS. 6A and 6B;

8 is a signal waveform diagram of a control unit employed in the multiple output DC / DC converter of the present invention.

Figure 9 is a waveform diagram of the switching operation by the control unit employed in the multiple output DC / DC converter of the present invention.

10 is an operational waveform diagram of a multiple output DC / DC converter of the present invention.

<Detailed Description of Major Symbols in Drawing>

100 ... switching part 200 ... first conversion part

300 ... second converter 400 ... first rectifier

500 ... 2nd rectifier 600 ... control part

610 ... main switching controller 620 ... signal generator

621 Pulse Generator 622 Triangle Wave Generator

630 ... output switching controller 631comparator

632 ... output switching circuit

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

2 is a block diagram of a multiple output DC / DC converter of the present invention.

Referring to FIG. 2, the multiple output DC / DC converter of the present invention includes a switching unit 100, first and second converters 200 and 300, first and second rectifiers 400 and 500, and a controller 600. . In addition, the AC power rectifier may further include a power factor correction unit (PFC) for rectifying the power factor and then providing an input DC power source Vin to the switching unit 100.

The switching unit 100 includes first and second switches Q1 and Q2 for alternately switching the input DC power supply Vin. The AC power switched by the first and second switches Q1 and Q2 is transmitted to the first and second converters 200 and 300.

The first and second converters 200 and 300 may include first and second single transformers having primary and secondary windings L1a, L1b, L2a, and L2b, respectively. In addition, the first converter 200 may include the first resonant capacitor Cr1 and the first resonant inductor Lr1 connected in series with the input terminal of the first switch Q1 of the switching unit 100, and the primary winding of the first transformer. An LLC resonant method including a first magnetized inductor Lm1 connected in parallel to L1a may be adopted.

Similarly, the second conversion unit 300 is the first of the second resonant capacitor Cr2 and the second resonant inductor Lr2 and the second single transformer connected in series to the input terminal of the second switch Q2 of the switching unit 100. An LLC resonant method including a second magnetized inductor Lm2 connected in parallel to the winding L1b may be adopted. The first and second magnetizing inductors Lm1 and Lm2 described above may be configured only with leakage inductance of the single transformer.

As described above, the first and second converters 200 and 300 may include the first single transformer L1a and L1b, the first resonant capacitor Cr1, and the first resonant inductor Lr1. The first switch Q1 is connected in parallel, and the second single transformer L1b, L2b, the second resonant capacitor Cr2, and the second resonant inductor Lr2 are connected in parallel to the second switch Q2. Can be.

3 is a configuration diagram showing another embodiment of the power conversion unit employed in the multiple output DC / DC converter of the present invention.

Referring to FIG. 3, the first and second converters 200 and 300 employed in the multiple output DC / DC converter of the present invention may include the first single transformer L1a and L2a, the first resonant capacitor Cr1, and the first resonant capacitor Cr1 and the first resonant capacitor Cr1. The resonant inductor Lr1 is connected in parallel to the first switch Q1, and the second single transformer L1b and L2b, the second resonant capacitor Cr2, and the second resonant inductor Lr2 are also connected to the first switch Q1. It may be a structure connected in parallel.

Referring back to FIG. 2, AC power converted from the first and second converters 200 and 300 is transferred to the first and second rectifiers 400 and 500, respectively.

The first and second rectifiers 400 and 500 rectify the AC power converted from the first and second converters 200 and 300, respectively, and output the first and second DC power sources Vs and Va. In this case, the second rectifier 500 rectifies the AC power and then switches under the control of the controller 600 to convert the rectified power into a second DC power Va. The first and second DC power supplies Vs and Va from the first and second rectifiers 400 and 500 are transmitted to the controller 600.

Meanwhile, the configuration of the first and second rectifiers 400 and 500 may be variously implemented and will be described with reference to the following drawings.

(A), (b) and (c) of FIG. 4 are schematic diagrams showing embodiments of the first rectifying unit employed in the multiple output DC / DC converter of the present invention, and FIGS. (c) is a block diagram showing embodiments of the second rectifier employed in the multiple output DC / DC converter of the present invention.

The first rectifier 400 employed in the multiple output DC / DC converter of the present invention has a half-wave rectification structure using one diode as shown in FIG. 4 (a), as shown in FIG. 4 (b). A full-wave rectification structure using four diodes or a center-tap full-wave rectification structure using two diodes may be configured as shown in FIG.

Similarly, the second rectifier 500 employed in the multiple output DC / DC converter of the present invention has a half-wave rectification structure using one diode as shown in FIG. 5A, and is shown in FIG. 5B. As shown in (c) of FIG. 5, a third switch Q3 is connected in series to a center-tap full-wave rectification structure using two diodes. .

Referring back to FIG. 2, the first and second DC power supplies Vs and Va from the first and second rectifiers 400 and 500 are transmitted to the controller 600, and the first and second DC power supplies Vs and Va are provided. The control unit 600 controls the switching of the switching unit 100 and the switching of the second rectifying unit 500 according to the voltage level.

To this end, the controller 600 may include a main switching controller 610 for providing first and second switching signals sw1 and sw2 for controlling alternating switching of the switching unit 100, and first and second switching signals ( a signal generator 620 for generating a triangular wave signal synchronized with sw1 and sw2, and an output switching controller 630 for providing a third switching signal for controlling output switching of the second rectifier 500.

The main switching controller 610 receives the first DC power supply Vs and feeds back the first and second switching signals sw1 and sw2 that control the switching duty according to the voltage level of the first DC power supply Vs. To the first and second switches Q1 and Q2. The first and second switching signals sw1 and sw2 are also provided to the signal generator 620.

The signal generator 620 transmits the signal level of the first and second switching signals sw1 and sw2 from the main switching controller 610 and the first and second from the pulse transformer 621. And a triangular wave generation circuit 622 for generating a clock signal CLK in accordance with the signal levels of the switching signals sw1 and sw2 and for generating a triangular wave Vsaw in accordance with the clock signal CLK.

The clock signal CLK may be generated to have a high signal or a low signal at the dead time of the first and second switching signals sw1 and sw2. Accordingly, the triangle wave generator circuit 622 may be configured in the following two embodiments.

6 (a) and 6 (b) are configuration diagrams showing embodiments of the triangular wave generator circuit employed in the multiple output DC / DC converter of the present invention.

Referring to FIG. 6A, the triangle wave generator circuit 622 inverts the signal levels of the combined first and second switching signals sw1 and sw2 from the pulse transformer 621 (Isaw), and inverts them. The result is used as the clock signal CLK1. According to the clock signal CLK1, a resistor Q may be used to switch the voltage charged in the capacitor Csaw to generate a triangular wave signal Vsaw.

Referring to FIG. 6B, the triangle wave generator circuit 622 uses the signal levels of the combined first and second switching signals sw1 and sw2 from the pulse transformer 621 as the clock signal CLK2. . The signal levels of the combined first and second switching signals sw1 and sw2 are inverted (Isaw), and the voltage charged in the capacitor (Csaw) is switched (Qsaw) through a resistor (Rsaw) to generate a triangular wave signal (Vsaw). It may be composed of a structure that occurs.

As described above, the triangular wave signal Vsaw according to the configuration of the triangular wave generator circuit of FIG. 6A or 6B has the same signal waveform.

FIG. 7 is a signal waveform diagram by the triangular wave generator circuit shown in FIGS. 6A and 6B.

Referring to FIG. 7, as shown in FIGS. 6A and 6B, the clock signals CLK1 and CLK2 may be high at the dead time of the first and second switching signals sw1 and sw2. It may have a signal (CLK1) and may have a low signal (CLK2). Accordingly, the triangular wave signal Vsaw is synchronized with the first and second switching signals sw1 and sw2.

That is, when the node V _A becomes high, a low signal is applied to the base terminal of the switch Qsaw, and the capacitor is gradually charged by the current flowing through the resistor. Done. Charging of the capacitor (Csaw) is continued until the switch (Qsaw) is turned on, when the node V _A is turned low, a high signal is applied to the base terminal of the switch (Qsaw) Qsaw conducts, and the charge charged in the capacitor (Csaw) discharges rapidly through the switch (Qsaw). By repeatedly performing such an operation, a triangular wave signal Vsaw signal is generated in synchronization with the switching of the switching unit 100.

Referring again to FIG. 2, the triangular wave signal Vsaw from the signal generator 620 is transmitted to the output switching controller 630.

The output switching controller 630 includes a comparison element 631 for comparing the voltage level of the second DC power supply with a voltage level of the preset reference voltage Vref, a comparison result from the comparison element 632, and a triangle wave signal Vsaw. ) Provides a third switching signal sw3 that controls the switching of the third switch Q3 of the second rectifier 500.

8 is a signal waveform diagram of a control unit employed in the multiple output DC / DC converter of the present invention.

Referring to FIG. 8, it can be seen that the third switching signal sw3 of the output switching controller 630 of the controller 600 is provided according to the comparison result from the comparison element 632 and the triangular wave signal Vsaw.

That is, when the voltage level of the triangle wave signal Vsaw is higher than the voltage level of the comparison result, the third switching signal sw3 is converted into a high signal for conducting the third switch Q3, and the triangle wave signal Vsaw When the voltage level is lower than the voltage level of the comparison result, the third switching signal sw3 is switched to a low signal that blocks the third switch Q3. The falling edge of the third switching signal sw3 described above coincides with the switching synchronization of the switching unit 100 to enable the zero current switching off operation of the third switch Q3.

9 is a waveform diagram of switching operation by the control unit employed in the multiple output DC / DC converter of the present invention.

Referring to FIG. 9, the variation of the second DC power supply Va of the second rectifying unit 500 according to the variation of the input voltage or the output load changes the time point at which the third switch Q3 is turned on, and the third The magnitude of the resonance current Isec2 supplied to the secondary winding L2b of the second converter 300 is determined by the current initial value at the time when the switch Q3 is turned on. That is, when the voltage level of the second DC power supply Va of the second rectifying unit 500 is lower than the voltage level of the reference voltage Vref, the point of time to switch to the on of the third switch Q3 is accelerated, and the resonance current is increased. The second DC power supply Va of the second rectifying unit 500 is increased by increasing the initial value of Ipri2 and increasing the magnitude of the resonance current Isec2 supplied to the secondary winding L2b of the second converter 500. Increase the voltage level. On the contrary, when the voltage level of the second DC power supply Va of the second rectifier 500 is higher than the voltage level of the reference voltage Vref, the operation of the above operation is reversed.

10 is an operational waveform diagram of a multiple output DC / DC converter of the present invention.

2 and 10, the third switching signal sw3 from the controller 600 synchronized with the switching of the switching unit 100 is applied to the third switch Q3, and the third switch Q3 is applied to the third switch Q3. From the time of turning on, power is supplied from the primary winding L1b of the second converter 300 to the second rectifier 500.

The time point at which the third switch Q3 is turned off is a time point after power supply is completed from the primary winding L1b of the second converter 300 to the second rectifier 500. As a result, the third switch Q3 may achieve zero current switching ZCS, thereby reducing switching loss and improving power conversion efficiency.

The periods of supplying power from the primary windings L1a and L1b of the first or second converters 200 and 300 to the secondary windings L2a and L2b include resonance capacitors Cr1 and Cr2, resonance inductors Lr1 and Lr2, and Since it is determined by the resonance frequency set by the magnetizing inductors Lm1 and Lm2, the secondary windings L2a and L2b from the primary windings L1a and L1b of the first or second converters 200 and 300 even when the load of the output terminal varies. The period of power supply to) does not change. Accordingly, regardless of the variation in the load of the secondary winding L2a of the first converter 200, the second DC power source is supplied from the secondary winding L2b of the second converter 300 through the second rectifier 500. (Va) can be output.

In addition, the controller 600 is synchronized with the switching signals sw1 and sw2 of the first and second switches Q1 and Q2 and turns on the third switch Q3 based on the voltage level of the second DC power supply Va. Since the period in which the current Isec2 flows from the secondary winding L2b of the second converter 300 to the second rectifier 500 is controlled by turning on / off, the second DC power source output from the second rectifier 500 ( The voltage level of Va) can be controlled with high accuracy.

As described above, since the second DC power supply Va output from the second rectifying unit 500 is directly controlled by the on / off operation of the third switch Q3, the power conversion loss is small and the second rectifying unit ( Highly stable second DC power supply Va can be obtained by a simple and easy circuit change such as adding a third switch Q3 to 500, thereby increasing power conversion efficiency and generating a high-precision DC power supply. Low cost multiple output DC / DC converters can be realized.

In addition, in the multi-output DC / DC converter according to the present invention, the control unit 600 synchronizes the switching operation of the third switch Q3 with the switching operation of the first and second switches Q1 and Q2, thereby providing zero current switching ( Since ZCS is achieved, switching losses at the third switch Q3 can be reduced.

As described above, since the switching of the output stage is controlled in synchronization with the switching signal of the power conversion stage, the step-down chopper circuit used in the conventional multi-output DC / DC converter becomes unnecessary, thus requiring the parts of the step-down chopper circuit of the step-down chopper circuit. There is an effect of reducing the manufacturing cost corresponding to the number, and the zero current switching control of the output stage in synchronization with the switching signal of the power conversion stage has the effect of reducing the power loss due to switching loss and conduction loss of the step-down chopper circuit.

Meanwhile, in the conventional multi-output DC / DC converter, a single transformer is used, whereas in the multi-output DC / DC converter of the present invention, two transformers are used. However, since two transformers divide each of the total power used by a single transformer, Each transformer can be miniaturized, and likewise, in the case of the control unit 600, the above-described functions can be integrated in one IC, so that there is no problem of an increase in required parts and an increase in manufacturing cost.

The present invention described above is not limited to the above-described embodiment and the accompanying drawings, but is defined by the claims below, and the configuration of the present invention may be modified in various ways without departing from the technical spirit of the present invention. It will be apparent to those skilled in the art that the present invention may be changed and modified.

Claims (9)

A switching unit which alternately switches an input DC power source and converts the AC power into an AC power source; A first converter having a single transformer for converting the AC power from the switching unit into a first power source having a voltage level in accordance with a preset turns ratio; A second converter converting the AC power from the switching unit into a second power source having a voltage level according to a preset turns ratio and having a single transformer magnetically independent of the first converter; A first rectifier for rectifying the first power from the first converter to output a first DC power; A second rectifier for rectifying the second power from the second converter and switching the rectified power to output a second DC power; And A controller which controls the switching of the second rectifier in synchronization with the switching of the switching unit Multiple output DC / DC converter comprising a. The method of claim 1, wherein the control unit A main switching controller receiving feedback of the first DC power from the first rectifying unit and providing first and second switching signals for controlling alternating switching of the switching unit according to the voltage level of the first DC power supply; A signal generator for generating a triangular wave signal in synchronization with the first and second switching signals from the main switching controller; And An output switching controller controlling switching of the second rectifier according to a comparison result between the voltage level of the second DC power supply from the second rectifier and a preset reference voltage and a triangular wave signal from the signal generator Multiple output DC / DC converter comprising a. The signal generator of claim 2, wherein the signal generator A pulse transformer delivering pulses of the first and second switching signals from the main switching controller; And A triangular wave generating circuit for generating a clock signal at a dead time of the first and second switching signals from the signal synchronizing transformer and generating the triangular wave signal in accordance with the clock signal; Multiple output DC / DC converter comprising a. The method of claim 3, And the triangular wave generating circuit generates a clock signal having a high signal at a dead time of the first and second switching signals. The method of claim 3, And the triangular wave generating circuit generates a clock signal having a low signal at a dead time of the first and second switching signals. The method of claim 2, wherein the output switching controller A comparison element comparing the voltage level of the second DC power supply with the voltage level of the reference voltage; And An output switching circuit for providing a third switching signal for controlling the switching of the second rectifier according to a comparison result from the comparison element Multiple output DC / DC converter comprising a. The method of claim 1, The first converter further comprises a first resonant capacitance for charging and discharging the switched power, a first resonant inductor for charging the switched energy, and a first magnetization inductor. Converter. The method of claim 1, The second converter includes a second resonant capacitance for charging and discharging the switched power, a second resonant inductor for charging the switched energy, and a second magnetization inductor. Converter. The method of claim 1, The multiple output DC / DC converter further comprises a power factor correcting unit rectifying the commercial AC power and power factor correcting the rectified power to provide the input DC power.