KR200236029Y1 - DC-DC Converter for adjusting Output Voltage - Google Patents

Abstract

The present invention converts an input DC power source into a pulse signal according to a predetermined pulse width control signal, induces an AC power source with the pulse signal, and generates a first output voltage through a rectifying circuit. The voltage Vout1 operates by receiving a first transformer configured to have mutual insulation characteristics and a first output voltage Vout1 output through the first transformer 100, and protrudes to the outside of the device through an external terminal. According to the resistance value of the sensed resistor, the corresponding pulse width modulation control signal is output, and the first output voltage Vout1 is converted into an AC signal, and then the voltage level of the second output voltage Vout2 of DC is arbitrarily changed through a filter. The present invention provides a variable output voltage DC-DC converter capable of arbitrarily varying the output voltage to a required voltage by a simple resistance replacement method.

Description

DC-DC Converter for adjusting Output Voltage}

The present invention relates to a DC-DC converter, and in particular, by installing an external terminal that can be plugged into the output terminal of the DC-DC converter by replacing the resistance, and by installing a corresponding resistor according to the voltage to be output by the user arbitrarily, The present invention relates to an output voltage variable DC-DC converter capable of outputting a variable voltage according to a simple voltage.

In general, a DC-DC converter is a device that arbitrarily varies an output voltage with respect to an input power source. This converter is used for general electronic systems such as DSP (Digital Signal Processor) or CPU, electronic communication equipment, medical equipment, and semiconductor devices that operate according to the driving voltage required by the internal system without receiving input power. .

The DC-DC converter according to the prior art may be classified into an insulated type that provides an insulation function between input and output voltages and a non-isolated type that does not provide the same. Isolated converters between input and output voltages are mainly divided into forward and flyback methods. Most non-isolated converters are chopper type.

1 and 2 are circuit diagrams illustrating a forward type and a flyback type converter, which is an example of a DC-DC converter having insulation between input and output voltages according to the related art.

Referring to FIG. 1, a DC-DC converter according to a conventional forward method includes a PWM chip 1, a transformer 3, a driving transistor TR1, diodes D1 and D2, an inductor L1, and a capacitor C1. ) And photocouplers OP1 and OP2.

In this case, the DC-DC converter is insulated from the input / output voltage through the transformer 3 and the photocouplers OP1 and OP2.

In the forward type DC-DC converter, when commercial DC power is applied through the input terminal DC Vin, and the driving transistor TR1 is turned on, the voltage of the primary coil T1 of the transformer 3 becomes the secondary coil ( The voltage is transformed to a predetermined voltage at T2).

The voltage transformed through the secondary coil T2 passes through the diode D1 and is transmitted to the output terminal DC Vout through the inductor L1.

On the contrary, when the driving transistor TR1 is turned off, since there is no energy transfer from T1 to T2 of the transformer 3, the diode D2 conducts and the voltage accumulated in the inductor L1 is output.

On the other hand, the PWM chip 1 adjusts the duty ratio of PWM, the operation signal of the driving transistor TR1. When the voltage value of the output terminal DC Vout is high, the duty ratio is decreased, and the output voltage is low. In this case, increase the duty ratio to keep the output voltage constant. Usually, the duty ratio setting of the PWM is adjusted to a constant duty ratio through a fixed resistor and then adjusted to the desired duty ratio within this range.

The light emitting diode OP1 constituting the photocoupler detects a change in voltage of the output terminal and transfers the light to the phototransistor OP2 through light. The light received by the phototransistor OP2 is converted into an electrical signal, and the signal enters the PWM chip 1 to adjust the duty ratio according to the voltage change of the output terminal to maintain a constant output voltage.

Meanwhile, referring to FIG. 2, a flyback type DC-DC converter according to the related art includes a PWM chip 1, a transformer 3, a driving transistor TR2, a diode D3, a capacitor C2, and a photocoupler. (OP1, OP2).

Here, the flyback DC-DC converter is also insulated between the input / output voltage through the transformer 3 and the photo coupler (OP1, OP2) like the forward method.

First, in the flyback type DC-DC converter, when commercial power is applied through the input terminal and the driving transistor TR2 is turned off, the voltage of the primary coil T1 of the transformer 3 is predetermined in the secondary coil T2. Transformed into voltage. The voltage transformed through T2 is transmitted to the output terminal through the diode D3.

On the contrary, when the driving transistor TR2 is turned on, the energy from T1 to T2 of the transformer 3 is charged.

Unlike the forward method described above, the flyback type DC-DC converter has a simple circuit configuration because there is no inductor connected to the secondary side of the transformer, and the rest of the PWM chip (except that the operation of the driving transistor is different) 1) and photo couplers OP1 and OP2 operate in the same manner as in FIG.

Therefore, the DC-DC converter of the prior art forward or flyback type uses a transformer to change the DC power supply to obtain a desired output DC voltage. In particular, a transformer and a photocoupler are used to make an input / output voltage to make an input. The effect of the output due to the sudden change of the maximum is prevented.

However, the conventional isolated DC-DC converter can convert a high input power to a low output power by using a transformer, but has a disadvantage in that only one output voltage can be obtained per DC-DC converter.

For this reason, forward or flyback isolated DC-DC converters are typically used as large mains supplies (48V input ⇒ 5V / 10A output).

Therefore, the conventional isolated DC-DC converter is difficult to control the output voltage to the desired level, so the DC-DC converter module is replaced according to the desired output voltage according to the change of the output voltage, or the module is adapted to the required voltage of the used system. There was a disadvantage to make.

Therefore, in the case of the isolated DC-DC converter according to the prior art, the influence of the output stage due to the drastic change in the input stage can be minimized compared to the non-isolated chopper method, but it is difficult to precisely control the output voltage, Since only a single voltage is output per DC converter, the module has to be designed differently according to the output voltage required in the design, thereby increasing the design cost.

Therefore, the purpose of the present invention is to install an external terminal that can be plugged into the output terminal of the isolated DC-DC converter, and then to replace the resistor according to the user's desired output according to the desired voltage, simple resistance replacement The present invention provides an output voltage variable DC-DC converter capable of outputting the output voltage by changing the output voltage to a required voltage.

1 and 2 is a circuit diagram showing an example of a conventional isolated DC-DC converter,

3 is a functional block diagram showing an isolated DC-DC converter according to the present invention,

4 is a detailed circuit diagram of FIG. 3 according to an embodiment of the present invention;

FIG. 5 is a diagram illustrating an internal configuration of a PWM chip of the oscillation controller of FIG. 4.

FIG. 6 is a diagram illustrating an internal configuration of a PWM chip of the output voltage controller of FIG. 4.

* Explanation of symbols for the main parts of the drawings

100: first transformer 110: input unit

120: transformer 130: rectifier circuit

140: output detection unit 150: oscillation control unit

200: second transformer 210: output unit

230: output voltage control unit 250: output voltage control unit

Technical means of the present invention for achieving the above object, the input unit 110 for receiving a predetermined DC high voltage from the outside to remove the noise through the LC filter; A transformer unit 120 for converting a DC power supply through the input unit 110 into a pulse signal according to a predetermined pulse width control signal to induce an AC signal; A rectifier circuit 130 for rectifying the AC voltage through the transformer to generate a first output voltage Vout1; An output detector 140 which detects a change in the first output voltage Vout1 output through the rectifier circuit 130 and feeds it back through a photocoupler; An oscillation control unit 150 which receives the signal fed back from the output detection unit 140 and variably controls the oscillation pulse width to generate a pulse signal of a predetermined frequency in the transformer unit; The output unit 210 converts the first output voltage Vout1 output from the rectifier circuit unit 130 into an AC signal according to a predetermined pulse width control signal and generates a second output voltage Vout2 of DC through a filter. Wow; After detecting the second output voltage Vout2 output through the output unit 210 through a plurality of sensing resistors, the level of the second output voltage Vout2 is changed by varying the resistance value of the resistor protruding through the external terminal. An output voltage adjusting unit 230 for adjusting; And receiving a second output voltage Vout2 sensed by the output voltage adjusting unit 230 as a feedback terminal, comparing the output voltage with a predetermined reference voltage, and outputting a predetermined pulse width control signal to the output unit 210. And an output voltage controller 250 for converting and controlling one output voltage Vout1 into an AC signal.

In addition, the output voltage adjusting unit 230 is connected to the first sensing resistor (R15) between the output terminal of the output unit 210 and the feedback terminal of the output voltage control unit 250, the output side of the first sensing resistor and The second sensing resistor R16 is connected between grounds, and is installed in parallel with the second sensing resistor R16 and protrudes to the outside through an external terminal, and then the second output voltage Vout2 And a resistor R0 for arbitrarily adjusting the level.

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

3 is a functional block diagram illustrating an output voltage variable DC-DC converter according to the present invention, and includes a first transformer unit 100 and a second transformer unit 200.

The first transformer 100 converts an input DC power source into a pulse signal according to a predetermined pulse width control signal, induces AC power to the pulse signal, and generates a first output voltage Vout1 through a rectifying circuit. However, the first output voltage Vout1 with respect to the input voltage is formed to have mutually insulating characteristics, and the second transformer 200 also receives the first output voltage Vout1 output through the first transformer 100. It is supplied and operated and outputs the pulse width modulation control signal corresponding to the resistance value of the sensing resistor protruding to the outside of the device through the external terminal to convert the first output voltage (Vout1) into an AC signal, and then through the filter Is generated by arbitrarily adjusting the voltage level of the second output voltage (Vout2).

Here, the first transformer unit 100 and the second transformer unit 200 is preferably configured as one module.

In addition, the first transformer 100 receives an input of a predetermined DC high voltage from the outside and removes noise through the LC filter, and the DC power supply through the input unit 110 modulates a predetermined pulse width (PWM). A transformer unit 120 for converting a pulse signal according to a control signal to induce an AC signal, and rectifying the AC voltage through the transformer unit 120 to generate a first output voltage Vout1; The output detector 140 detects a change in the first output voltage Vout1 output through the rectifier circuit unit 130 and feeds it back through the photocoupler, and receives a signal fed back from the output detector 140 and a transformer. An oscillation control unit 150 that variably controls the oscillation pulse width PWM so as to generate a pulse signal of a constant frequency is formed by the reference numeral 120.

In addition, the second transformer 200 converts the first output voltage Vout1 output from the rectifier circuit 130 into an AC signal according to a predetermined pulse width control signal. The output unit 210 generating Vout2) and the second output voltage Vout2 output through the output unit 210 are detected through a plurality of sensing resistors, and then the resistance value of the resistor protruding through the external terminal is variable. The output voltage controller 230 for adjusting the level of the second output voltage Vout2 and the second output voltage Vout2 sensed through the output voltage controller 230 are provided as feedback terminals to provide a predetermined reference voltage. The output voltage controller 250 converts the first output voltage Vout1 into an AC signal by outputting a predetermined pulse width control signal to the output unit 210 after comparison with the control signal.

) Denotes an insulated portion between the input circuit terminal and the first output circuit terminal, and means non-contact signal transmission.

4 is a circuit diagram of FIG. 3 according to an embodiment of the present invention, and includes an input unit 110, a transformer unit 120, a rectifier circuit unit 130, an output detector unit 140, an oscillation control unit 150, and an output unit 210. ), An output voltage controller 230 and an output voltage controller 250.

The input unit 110 includes noise or ripple signal removing capacitors C1 and C2 and a noise removing inductor L1 between the input terminal Vin and the primary coil T1 of the transformer T of the transformer unit 120. And a resistor (R1), and the transformer unit (120) is a transformer (T) for converting a DC voltage provided through the input unit 110 into a pulse signal in accordance with a predetermined pulse width modulation (PWM) control signal. A capacitor C3, an inductor L2, and diodes D1 and D2 that generate a power source for driving a PWM chip are connected between the coils T2 separated from the primary side of the transformer T.

The rectifier circuit 130 may include diodes D3 and D4, an inductor L4, noise or ripple cancellation capacitors C12, C13, and C14 connected to the secondary coil T3 of the transformer T, and overvoltage protection. It is configured to generate a first output voltage (Vout1) by rectifying the AC signal which is composed of the zener diode (ZD1) guided to the secondary coil (T3).

The output detector 140 detects a change in the resistors R22, R23, and R24 for feedback control and the first output voltage Vout1 fed back between the output terminal of the rectifier circuit 130 and the ground. ), The voltage detector REG1 and the capacitor C22 are connected to each other to detect the output voltage of the rectifier circuit 130. Here, the resistor R22 and the capacitor C24 are both stabilization elements of the light emitting diode OP1.

The oscillation control unit 150 is connected between the primary coil T1 of the push-pull transformer T and the ground to apply a DC signal applied to the transformer T according to a predetermined pulse width PWM control signal. A pulse width control signal for controlling the output signal of the transformer 120 in accordance with a predetermined detection signal, and a current sensor L3 for detecting the output current of the driving transistor M1 and the transformer 120 that are converted into and And a plurality of resistors R2 to R10, a plurality of capacitors C4 to C8, a phototransistor OP2, and a diode D5 connected to the respective terminals of the PWM chip 160. Consists of

In addition, the internal configuration of the PWM chip 160 of the oscillation control unit 150, as shown in Figure 5, the amplifiers (161, 163), diode 162, oscillator 164, PWM device 165, rectifier ( 166).

The output unit 210 of the second transformer unit 120 includes a diode D6, capacitors C19 and C20, amplifying transistors M2 and M3, and an output choke L5, and an output voltage. The adjusting unit 230 is a plurality of sensing resistors (R14, R15) are connected in series between the output terminal of the output unit 210 and the feedback terminal (FB) of the output voltage control unit 250, the sensing resistor (R15) of A plurality of sensing resistors R16 and R17 are connected in series between the output side and the ground, and are installed in parallel with the sensing resistor R16 to protrude to the outside through an external terminal, and then the second output voltage Vout2 is changed to a resistance value. The control resistor R0 for arbitrarily adjusting the level of is connected.

That is, a plurality of resistors R14, R15, R16, R17, and R0 are provided in series / parallel between the output terminal of the output unit 210 and the feedback terminal FB of the PWM chip 260, and the output unit 210 The second output voltage Vout2 is sensed through a plurality of series / parallel resistors and then supplied to the feedback terminal FB of the PWM chip 260 to increase the level of the second output voltage Vout2 of the output unit 210. Random adjustment is made.

The output voltage controller 250 includes a PWM chip 260 for outputting a pulse width control signal for controlling the second output voltage Vout2 of the output unit 210 according to a predetermined feedback signal, and a drive control resistor ( R13), capacitors C15 and C16 for determining the feedback stabilization time constant, resistor R18, and the driving power RC filters C17, C18, and R17 of the PWM chip 260.

As shown in FIG. 6, the internal configuration of the PWM chip 260 of the output voltage controller 250 includes an amplifier 261, a delayer 262, a comparator 263, an oscillator 264, and a logic gate 265. And inverters 266 and 267 which output driving signals of the amplifying transistors M2 and M3.

The output voltage variable power supply apparatus according to the present invention configured as described above operates as follows.

For example, when a DC 48V power source is applied to the input unit 110 of the first transformer unit 100, the initial operating power is supplied to the terminal 7 of the PWM chip 160 through the input resistor R1.

Once the PWM chip 160 is operated, a pulse signal having a predetermined pulse width is output through the terminal 6 to open and close the driving transistor M1 and thus applied to the primary coil T1 of the transformer T. DC power is converted into a pulse signal to induce an AC signal to the secondary coil (T2, T3).

After the AC voltage transferred to T2 of the transformer T is rectified through the diodes D1 and D2, a DC power is made through the inductor L2, and the DC power is the driving power of the oscillation control unit 150. Used as

The AC voltage transferred to the secondary coil T3 of the transformer T is passed through a filter such as diodes D3 and D4 of the rectifier circuit 130, an inductor L4, and capacitors C12, C13, and C14. After the AC component is removed, the first output voltage Vout1 is generated. At this time, noise or ripple is removed through the capacitors C12, C13, and C14, and overvoltage is prevented through the zener diode ZD1.

The PWM chip 160 is driven through the coil T2 separated on the primary side of the transformer T. The PWM chip 160 outputs a reference voltage of approximately 5V to the eighth terminal through an internal rectifier 166. The reference voltage is used as each power source of the oscillation control unit 150.

In addition, the change amount of the first output voltage Vout1 output from the rectifying circuit unit 130 by the phototransistor OP2 from the light emitting diode OP1 of the output detector 140 through the second terminal of the PWM chip 160 is measured. Detects through the error amplifier 161. At this time, the stability (gain) of the error amplifier 161 and the feedback circuit is obtained by the resistor R5 and the capacitor C4 connected in parallel to the first terminal of the PWM chip 160.

The signal output through the error amplifier 161 is input to the PWM device 165 after comparing with the voltage of the current sensor L3 applied to the terminal 3 via the diode 162 through the comparator 163.

Accordingly, the PWM device 165 creates a pulse width modulated waveform, determines the duty ratio, and sends it to the sixth terminal.

In addition, when the voltage of the rectifier circuit 130 is changed, the output detector 140 changes the resistance of the voltage detector REG1, thereby controlling the amount of light by controlling the amount of current of the light emitting diode OP1.

Therefore, the first transformer unit 100 of the present invention is input through the transformer (T), the photocoupler (OP1, OP2) and the current sensor (L3) when transforming the DC input power source (24V to 72V) to a constant DC voltage. Insulation between / outputs is achieved.

Next, the output voltage controller 250 of the second transformer 200 has a control signal of the output voltage controller 230 inputted to the feedback terminal FB and a signal oscillated by the oscillator 264. To detect the difference is input to the comparator 263, the signal of the feedback stabilization time constant elements input to the comparator terminal (C0MP) to control the signal of the output voltage regulator 230.

The output signal of the rectifier circuit unit 130 applied through the resistor R13 is also input to the comparator 263 through the delay unit 262.

The output of the comparator 263 enters the input terminal of the logic gate 265 again and is logically combined with the signal output from the oscillator 264.

Subsequently, the output signal of the logic gate 265 is non-inverted and inverted and input to the inverters 266 and 267, respectively.

The first output voltage Vout1 of the rectifying circuit unit 130 is applied to the power supply terminal PVcc1 of the inverter 216 to be used as a driving power source of the inverter 216, while to the power supply terminal Vcc of the inverter 217. The first output power Vout1 of the rectifying circuit unit 130 is applied through the RC filters R19, C17, and C18, and this voltage is used as a driving power source of the PWM chip 260.

At this time, the inverters 216 and 217 output pulse width control signals that are opposite to each other through the output terminals G1 and G2 to control the amplifying transistors M2 and M3, respectively.

Accordingly, the two amplification transistors M2 and M3 are alternately turned on and off so that the first output voltage Vout1 is converted into an AC signal and then rectified and output through the output choke L5 and the capacitor C20. In this case, the second output voltage Vout2 is output to any one of a plurality of voltage levels, and the plurality of output voltage levels is approximately 1.5V to 3.5V DC.

The second output voltage Vout2 output through the output choke L5 is fed back to the PWM terminal 260 by the resistors R14, R15, R16, R17, and R0 of the output voltage adjusting unit 230. The voltage supplied to the feedback terminal FB is input to FB), and the voltage supplied to the feedback terminal FB is varied by the resistance value of the external regulating resistor R0 installed externally through the external terminal.

The detection signal according to the changed resistance value of the output voltage regulator 230 is input to the feedback terminal FB of the PWM chip 260 and compared with the oscillation signal of the oscillator 264 through the comparator 263 to modulate the pulse width. The frequency and the level of the second output voltage Vout2 are determined.

That is, in order to control the second output voltage Vout2 output through the output unit 210, the minimum output voltage is set as the internal sensing resistors R14, R15, R16, and R17 of the output voltage controller 230. An external regulating resistor (R0) was attached to the external terminal to increase the voltage to make the user's desired voltage.

The feedback terminal FB of the PWM chip 260 is input to the non-inverting terminal of the amplifier 261, a reference voltage of approximately 1.25V is applied to the inverting terminal, and the second output voltage Vout2 of the output unit 210 is Voltage is applied to the series / parallel circuit composed of resistors R14, R15, R16, R17, and R0, and a constant voltage is induced to each resistor according to the resistance value.

The resistors R14 and R17 are designed to have a very small value without affecting the operation of the circuit, which is to prevent a malfunction in the case of disconnection of the detection line.

The PWM chip 260 controls the second output voltage Vout2 such that a voltage matching the reference voltage is input to the feedback terminal FB. That is, when the sensing voltages R15, R16, and R0 input to the feedback terminal FB of the PWM chip 260 are variable, the second output voltage Vout2 is variable.

The sensing voltage depends on the resistors R15 and R16. When the sensing voltage is Vss, Vss can be obtained as shown in Equation 1 below.

As described in the above description, since the PWM chip 260 controls the output so that the sensing voltage applied to the feedback terminal and its own reference voltage (1.25V) match, the second output voltage Vout2 can be obtained as shown in Equation 2 below. .

When the first sensing resistor R15 is a fixed value in Equation 2, it can be seen that the second output voltage Vout2 changes according to the change of the second sensing resistor R16.

Based on the above principle, in the present invention, the second sensing resistor R16 having a fixed value is installed in the voltage supply device, and both ends of the second sensing resistor R16 are exposed to the outside to adjust the resistor R0 to the externally exposed terminal. In the case of connecting A, the actual resistance value of the second sensing resistor R16 may be obtained by an externally connected resistor and a parallel resistance formula.

If the external connection resistance is R0, the parallel resistance value Rp can be expressed as Equation 3 below.

Therefore, the parallel resistance value increases as the value of the adjusting resistor R0 increases, and the parallel resistance value decreases as the value of the adjusting resistor R0 decreases.

In conclusion, when the value of the adjusting resistor R0 is small and the parallel resistance value is low, the second output voltage Vout2 is high, and when the value of the adjusting resistor R0 is large and the parallel resistance value is high, the second output voltage Vout2 is low.

Accordingly, the change of the resistance value of the second sensing resistor R16 may be adjusted through the adjustment resistor R0 of the external terminal connected in parallel with the second sensing resistor R16, which is the second output voltage Vout2. ) Is adjusted.

In this way, the constant DC voltage of the first transformer 100 may be changed to any one of a plurality of voltage levels again through a resistance value of the external regulating resistor R0 of the output voltage adjusting unit 230. In a powered system, the required voltage can be precisely matched.

In addition, the second transformer 200 determines the frequency and the level of the output voltage, but complementarily turns on the two amplifying transistors M2 and M3 so that the current continuously flows, thereby causing the desired second output voltage Vout2. May continue to occur.

Therefore, an embodiment of the present invention makes the first output voltage (Vout1) of a predetermined level through the first transformer 100 having an input-to-output isolation function between the input DC power source (24V to 72V), the second transformer By randomly changing and replacing the resistance value of the resistor R0 protruding through the external terminal of the 200, the second output voltage Vout2 may be arbitrarily varied from 1.5V to 3.5V DC.

While specific embodiments of the present invention have been described and illustrated above, it is obvious that the present invention may be embodied in various modifications by those skilled in the art. Such modified embodiments should not be individually understood from the technical spirit or the prospect of the present invention, and such modified embodiments should fall within the appended claims of the present invention.

Therefore, by installing an external terminal that can be plugged in by replacing a resistor in the output terminal of the DC-DC converter having an insulation characteristic between input and output of the present invention, by installing the corresponding resistor according to the voltage to be output by the user arbitrarily By simply changing the resistance, the output voltage can be easily changed to the required voltage. Also, by simply changing the resistance, the output voltage can be widened according to the resistance value. In addition, there are various advantages such as low design cost due to the simplification of the circuit.

Claims (2)

In an isolated DC-DC converter: An input unit which receives a predetermined DC high voltage from the outside and removes noise through the LC filter; A transformer for inducing an AC signal by converting a DC power supply through the input unit into a pulse signal according to a predetermined pulse width control signal; A rectifying circuit unit rectifying an AC voltage through the transformer unit to generate a first output voltage Vout1; An output detector for detecting a change in the first output voltage Vout1 output through the rectifier circuit and then feeding back through a photocoupler; An oscillation control unit for receiving the signal fed back from the output detector and variably controlling the oscillation pulse width to generate a pulse signal of a predetermined frequency in the transformer unit; An output unit converting the first output voltage Vout1 output from the rectifier circuit unit into an AC signal according to a predetermined pulse width control signal and generating a second output voltage Vout2 of DC through a filter; An output for adjusting the level of the second output voltage Vout2 by detecting the second output voltage Vout2 output through the output unit through a plurality of sensing resistors and then varying the resistance value of the resistor protruding through an external terminal; Voltage control unit; And After receiving the second output voltage Vout2 sensed by the output voltage adjusting unit as a feedback terminal and comparing it with a predetermined reference voltage, a predetermined pulse width control signal is output to the output unit to exchange the first output voltage Vout1. An output voltage variable type DC-DC converter comprising an output voltage control unit for converting and controlling a signal. The method according to claim 1, The output voltage adjusting unit includes a first sensing resistor R15 connected between an output terminal of the output unit and a feedback terminal of the output voltage controller, and a second sensing resistor R16 connected between the output side of the first sensing resistor and ground. And a control resistor R0 for arbitrarily adjusting the level of the second output voltage Vout2 due to the change in resistance after being installed in parallel with the second sensing resistor R16 and protruding to the outside through an external terminal. Adjustable output voltage DC-DC converter, characterized in that provided.