JP2007124761A - Stabilized power supply - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stabilized power supply for simplifying a constitution, maintaining the high efficiency and a high ripple removing effect, and acquiring a stable and constant output voltage regardless of a fluctuation in an input voltage. <P>SOLUTION: A switching power supply circuit 10 has a switching voltage converting section 1 for converting the input voltage Vi into a primary conversion voltage Va by a control pulse SP, a pulse controlling section 2 for controlling a pulse width of the control pulse SP, and an oscillating section 3 for generating a rectangular oscillation signal X as a reference for generating the control pulse SP. A linear power supply circuit 20 converts the primary conversion voltage Va into the output voltage Vo. In the stabilized power supply, the switching power supply 10 and the linear power supply circuit 20 are connected. The oscillating section 3 fluctuates an amplitude of the oscillation signal X in proportion to the input voltage Vi, and maintains a constant frequency. The pulse controlling section 2 controls the pulse width of the control pulse SP independent of the input voltage Vi and the primary conversion voltage Va. A constant potential difference between the primary conversion voltage Va and the output voltage Vo is maintained. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a stabilized power supply device in which a linear power supply circuit is connected to a subsequent stage of a switching power supply circuit.

  As a method of configuring a direct current stabilized power supply, a method of combining a switching power supply circuit and a linear power supply circuit (series power supply circuit) is known. A switching power supply circuit has a wide input voltage range and good conversion efficiency. On the other hand, ripples are likely to remain in the converted voltage. On the other hand, the linear power supply circuit is a system in which the converted voltage has less noise such as ripple. However, since the potential difference between the input and output is mainly consumed as heat, the heat generation is large and the conversion efficiency is inferior to that of the switching power supply circuit.

  Focusing on such characteristics of the conversion method, a stabilized DC power supply is configured in which a linear power supply circuit is connected in series at the subsequent stage of the switching power supply circuit. That is, a large input voltage is converted to a voltage slightly higher than a predetermined output voltage by a highly efficient switching power supply circuit. The voltage is converted into a predetermined output voltage by the linear power supply circuit. The input voltage of the linear power supply circuit is most efficient when it is a voltage required for the linear power supply circuit to operate stably. That is, heat generation of the linear power supply circuit can be suppressed, and the input voltage can be converted into the output voltage with high efficiency. In addition, noise components such as ripples generated in the switching power supply circuit can be suppressed, and a stable output voltage with low noise can be output.

  FIG. 6 is a block diagram schematically showing a conventional configuration example of such a DC stabilized power supply apparatus. The stabilized DC power supply device includes a switching power supply circuit 10B and a linear power supply circuit 20B. The switching power supply circuit 10B includes a switching voltage conversion unit 1B, a pulse control unit 2B, an oscillation unit 3B, and a first error detection unit 6. The linear power supply circuit 20B includes a linear voltage conversion unit 4B and a second error detection unit 5B. As described above, if the voltage difference between the input voltage V2 and the output voltage V3 of the linear power supply circuit 20B is large, the efficiency deteriorates, and if it is too small, the voltage conversion becomes unstable. Therefore, the input voltage V2 of the linear power supply circuit 20B is controlled to an appropriate value. In the conventional configuration example shown in FIG. 6, the first error detector 6 is provided so that the output voltage V2 does not fluctuate even if the input voltage V1 to the switching power supply circuit 10B fluctuates.

Japanese Patent Application Publication No. JP-A-2001-259707, which is cited below, discloses a DC stabilized power supply having a basic configuration similar to that shown in FIG. In general, in order to change the output voltage of the power supply device while maintaining a low loss and ripple removal effect, it is necessary to readjust the constants of both the first error detection unit 6 and the second error detection unit 5B. The first error detection unit 6 corresponds to reference numerals 2 and 3 in FIG. The second error detection unit 5B corresponds to the first and fourth reference numerals 5 and 6.
Therefore, in the invention of Patent Document 1, the output result of the power supply apparatus can be obtained only by adjusting the constant of the second error detection unit 5B by adding the detection result of the second error detection unit 5B to the detection result of the first error detection unit 6. The voltage can be changed. The first error detector 6 corresponds to reference numerals 2, 8, and 9 in FIG.

JP 2004-201466 A (2nd to 21st paragraphs, FIGS. 1 and 4)

The power supply device disclosed in Patent Document 1 can change the output voltage of the power supply device while maintaining a low loss and ripple removal effect. Therefore, it is excellent as a power supply device in which a linear power supply circuit is connected to the subsequent stage of the switching power supply circuit. However, an error detection unit is required for both the switching power supply path and the linear power supply circuit. That is, an error detection circuit for monitoring the output voltage of the switching power supply circuit (input voltage of the linear power supply circuit) is required.
In recent years, the stabilized power supply apparatus has been increasingly used by being incorporated in a vehicle or an electric product, and further downsizing is desired in addition to energy saving (high efficiency). Therefore, it is necessary to propose a configuration that can be further reduced in size than the conventional configuration described above.

  The present invention has been made in view of the above problems. That is, an object of the present invention is to provide a stabilized power supply device having a simple configuration and high efficiency and high ripple removal effect. In particular, it is an object of the present invention to provide a stabilized power supply device that can maintain a high efficiency and a high ripple removal effect even when the input voltage fluctuates, and obtain a stable and constant output voltage with a simple configuration.

In order to achieve the above object, a stabilized power supply apparatus according to the present invention is configured as follows.
That is, a switching voltage conversion unit that switches an input voltage with a control pulse, smoothes and converts the input voltage into a primary conversion voltage, a pulse control unit that controls a pulse width of the control pulse, and a reference for generating the control pulse A stabilized power supply device to which a switching power supply circuit having an oscillating unit that generates a triangular wave oscillation signal and a linear power supply circuit that converts the primary conversion voltage into an output voltage are connected, and has the following characteristics: It has a configuration.
The oscillation unit varies the amplitude of the oscillation signal in proportion to the input voltage, and keeps the frequency of the oscillation signal constant regardless of the input voltage. The pulse control unit is configured to control the input voltage and the primary voltage. The pulse width of the control pulse is controlled by pulsing the oscillation signal with a threshold value determined independently with respect to the conversion voltage, so that the primary conversion voltage and the The potential difference from the output voltage is kept constant.

According to this characteristic configuration, the stabilized power supply device according to the present invention varies the amplitude of the oscillation signal in proportion to the varying input voltage. Then, a control pulse is generated from the oscillation signal whose amplitude is varied regardless of the primary conversion voltage. As a result, when the input voltage is increased, the amplitude of the triangular wave-like oscillation signal is increased, and the pulsing threshold is relatively lowered with respect to the oscillation signal. For this reason, the duty ratio of the control pulse varies as the input voltage varies. That is, as the input voltage increases, the ratio cut by the control pulse also increases. Therefore, even if the input voltage fluctuates, the primary conversion voltage is converted to a substantially constant value. As a result, the potential difference between the primary conversion voltage, which is the input of the linear power supply circuit, and the output voltage is also maintained at a substantially constant value.
In this feature configuration, the potential difference between the primary conversion voltage and the output voltage can be kept substantially constant without detecting the voltage value or error of the primary conversion voltage. Therefore, it is possible to provide a stabilized power supply device that can maintain a high efficiency and a high ripple removal effect even when the input voltage fluctuates, and obtain a stable and constant output voltage with a simple configuration.

The stabilized power supply according to the present invention can further include the following features in addition to the above features.
That is, the linear power supply circuit includes an error detection unit that detects an error of the output voltage by comparing a voltage obtained by dividing the output voltage with a predetermined reference voltage, and the oscillation unit includes the oscillation unit The lower limit value of the signal is ground, and the upper limit value is changed in proportion to the input voltage, thereby changing the amplitude,
The upper limit value is set to a value obtained by dividing the input voltage by the same voltage dividing ratio as that of the error detection unit, and the threshold value of the pulse control unit is changed according to the error of the output voltage. Features a point.

The output voltage of the stabilized power supply device, that is, the output voltage of the linear power supply circuit may vary depending on the power consumption of the load. The linear power supply circuit has an error detection unit that detects this variation (error) by comparing the divided value of the output voltage with a predetermined reference voltage that is a target of voltage conversion, and corrects this variation. .
On the other hand, in the switching power supply circuit, the oscillation unit varies the amplitude of the oscillation signal by varying the upper limit value in proportion to the input voltage. This upper limit is determined by dividing the input voltage. The oscillation signal generated by the oscillation unit is pulsed into a control pulse by the pulse control unit, and the input voltage is converted into a primary conversion voltage by the control pulse.
In this feature configuration, the threshold value of the pulse control unit is changed (corrected) in consideration of the error detected by the linear power supply circuit. That is, the primary conversion voltage is corrected following the fluctuation of the output voltage. If the voltage dividing ratio of the error detecting unit is the same as the voltage dividing ratio that defines the upper limit voltage as in this feature configuration, the followability is good. As a result, the potential difference before and after the linear power supply circuit can be kept constant, and a decrease in efficiency in the linear power supply circuit can be suppressed.

  Furthermore, in the stabilized power supply device according to the present invention, the oscillation unit generates the oscillation signal in a triangular waveform by charging and discharging a constant current to and from a capacitor, and the constant current is the input signal. It can be characterized in that it varies in proportion to the voltage.

As the input voltage increases, the amplitude of the triangular wave oscillation signal increases proportionally. When the oscillation signal is generated by charging / discharging the capacitor, if the charging / discharging current is constant regardless of the input voltage, the time required for charging / discharging varies. For example, as the input voltage increases, the amplitude of the oscillation signal increases, and the voltage obtained by charging the capacitor also increases. Charging the capacitor to a higher voltage with the same current requires a lot of charging time. When the charging time (and discharging time) becomes longer, the frequency of the oscillation signal becomes slower. When the input voltage is lowered, the effect is reversed and the frequency is increased.
Therefore, when the constant current for charging / discharging is changed in proportion to the input voltage as in this feature configuration, the constant current increases when the input voltage is high, and when the input voltage is low. The constant current is also reduced. Therefore, regardless of the input voltage, the capacitor is charged to a voltage corresponding to the input voltage in approximately the same time. As a result, the frequency of the oscillation signal can be kept constant regardless of the input voltage.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a block diagram schematically showing a configuration example of a stabilized power supply device according to the present invention. As shown in the figure, the stabilized power supply device is configured by connecting a linear power supply circuit 20 to the subsequent stage of the switching power supply circuit 10. The input voltage Vi input to the stabilized power supply device is converted into the primary conversion voltage Va by the switching power supply circuit 10, and then the primary conversion voltage Va is converted into the output voltage Vo by the linear power supply circuit 20.
The switching power supply circuit 10 includes a switching voltage conversion unit 1, a pulse control unit 2, and an oscillation unit 3. The linear power supply circuit 20 includes a linear voltage conversion unit 4 and an error detection unit 5.

  The switching voltage converter 1 switches the input voltage Vi with the control pulse SP, smoothes it, and converts it into the primary conversion voltage Va. The pulse controller 2 controls the pulse width (duty ratio) of the control pulse SP. The oscillating unit 3 generates a triangular wave oscillation signal X that is a reference for generating the control pulse SP.

  FIG. 2 is a waveform diagram for explaining the principle of pulse width control by the pulse controller 2 of FIG. The oscillation unit 3 varies the amplitude of the oscillation signal X in proportion to the input voltage Vi. At this time, the frequency of the oscillation signal X is kept constant regardless of the fluctuation of the input voltage Vi (the period T is constant). The pulse controller 2 controls the pulse width of the control pulse SP by pulsing the oscillation signal X with a threshold value E3 that is determined independently with respect to the input voltage Vi and the primary conversion voltage Va.

  FIG. 2 shows two oscillation signals X having different amplitudes. In these, the peak-peak (hereinafter referred to as PP) indicated between the lower limit value E5 and the upper limit value E4 is E4a and E4b on the basis of the ground (GND). E4b is twice the value of E4a, and the right waveform in the figure has twice the amplitude (or PP) of the left waveform. Since the periods are both T, the frequency is the same. These are pulsed by a common threshold value E3, and become control pulses SP having duty ratios of Ta1: Ta2 and Tb1: Tb2, respectively. Although details will be described later, the value obtained by multiplying the input voltage Vi by the ratio (H / T) of the H (High) state in the cycle T of the control pulse SP is the primary conversion voltage Va.

As is clear from FIG. 2, when a larger input voltage Vi is input and PP of the oscillation signal X becomes GND-E4b, the ratio of the H state of the control pulse SP becomes small. When the amplitude of the oscillation signal X is changed in proportion to the change of the input voltage Vi, a constant primary conversion voltage Va is obtained regardless of the change of the input voltage Vi. As a result, even if the input voltage Vi increases, the potential difference between the primary conversion voltage Va and the output voltage Vo can be kept constant, and an increase in loss in the linear power supply circuit 20 can be suppressed.
Note that the triangular wave oscillation signal X is not limited to an isosceles triangular waveform as shown in FIG. 2, and the same effect can be obtained even if it is a sawtooth wave.

Hereinafter, an example of an embodiment that specifically implements the principle of the present invention described above will be described with reference to FIGS.
FIG. 3 is a circuit diagram showing a schematic circuit configuration of the stabilized power supply device of FIG. The switching voltage converter 1 includes an n-channel power MOSFET (F1) as a switching element and a smoothing circuit that smoothes the waveform after switching. The smoothing circuit includes an inductor L1, a capacitor C1, a diode D1, and the like.

  The pulse control unit 2 includes a comparator A1. The comparator A1 pulses the triangular wave oscillation signal X input from the oscillation circuit 3A (oscillation unit 3) with a threshold value E3. Although details will be described later, the threshold value E3 is determined by adding an error detected by the linear power supply circuit 20 to the voltage E2 determined by the constant voltage circuit. The oscillation circuit 3A will be described later.

  The linear voltage conversion unit 4 includes a semiconductor element using a power transistor or the like, a stabilization capacitor, and the like. The error detector 5 divides the output voltage Vo by the voltage dividing resistors R1 and R2 and compares the divided value with a predetermined reference voltage E1 to detect an error. For example, when the power consumption by the load 9 is large, the power supply from the linear power supply circuit 20 cannot catch up, and the output voltage Vo may drop. When the output voltage Vo drops, the voltage divided by the resistors R1 and R2 also drops. The error detection circuit A2 detects the difference between the divided voltage value and the reference voltage E1, and transmits the detection result to the linear voltage converter 4. The linear power supply converter 4 controls the output voltage Vo according to the detection result.

  In order to make the potential difference between the primary conversion voltage Va and the output voltage Vo constant regardless of the variation of the input voltage Vi, the control so that the primary conversion voltage Va becomes a constant value has been described with reference to FIG. However, as described above, the output voltage Vo may vary depending on the power consumption of the load 9, and the voltage difference with the output voltage Vo may vary if the primary conversion voltage Va remains constant. Therefore, the detection result of the error detector 4 is also transmitted to the pulse controller 2 so that the fluctuation of the output voltage Vo is reflected in the primary conversion voltage Va. That is, the threshold value E3 of the pulse control unit 2 is changed according to the error of the output voltage Vo. The threshold value E3 is determined by adding the divided value of the output voltage Vo to the voltage E2 determined by the constant voltage circuit. Since the divided value of the output voltage Vo includes an error detected by the linear power supply circuit 20, the threshold value E3 of the pulse control unit 2 is changed according to the error of the output voltage Vo.

  FIG. 4 is a circuit diagram showing a schematic circuit configuration of the oscillation circuit 3A of FIG. In the figure, reference numeral 31 denotes an upper / lower limit value setting unit, reference numeral 32 denotes a triangular wave generation unit, and reference numeral 33 denotes a charge / discharge current setting unit.

  The upper and lower limit value setting unit 31 sets an upper limit value E4 and a lower limit value E5 that determine PP of the oscillation signal X. The upper limit value E4 is determined by dividing the voltage between the input voltage Vi and the ground (GND) by resistors R3 and R4. The divided voltage becomes the upper limit value E4 of the oscillation signal X (see FIG. 2). The lower limit value E5 of the oscillation signal X is GND (see FIG. 2). The comparator A3 determines whether or not the rising oscillation signal X has reached the upper limit value E4. The comparator A4 determines whether or not the descending oscillation signal X has reached the lower limit value E5. The outputs of the comparators A3 and A4 are input to the RS flip-flop FF. The RS flip-flop FF outputs a control signal for charging / discharging a capacitor Cx described later.

The voltage division ratio between the resistors R3 and R4 is the same as the voltage division ratio between the resistors R1 and R2 of the error detection unit 5 shown in FIG. By making the voltage dividing ratio the same, an error generated in the linear power supply circuit 20 can be added to the pulse control unit 2 of the switching power supply circuit 10 and the fluctuation of the output voltage Vo can follow the primary conversion voltage Va.
As described above, the output of the linear power supply circuit 20 may vary depending on the power consumption of the load 9. However, by adding an error generated in the linear power supply circuit 20 to the pulse control unit 2, the potential difference before and after the linear power supply circuit 20 can be kept constant. As a result, it is possible to suppress an increase in loss generated in the linear power supply circuit 20.

  FIG. 5 is a waveform diagram for explaining the principle of generating a triangular wave oscillation signal X by the oscillation circuit 3A of FIG. As shown in the figure, when the falling oscillation signal X reaches the lower limit E5, the output of the comparator A4 changes from H to L (low). This output is input to the set terminal (_S) of the RS flip-flop FF, and the output terminal (Q) becomes H. This output signal is input to the charge / discharge switch F2 (FET in this example), and charging of the capacitor Cx is started. While the output terminal (Q) is H, charging of the capacitor Cx is continued.

  When charging of the capacitor Cx is started, the voltage across the capacitor Cx increases. That is, the oscillation signal X rises. The output of the comparator A4 changes from L to H, and when the oscillation signal X reaches the upper limit value E4, the output of the comparator A3 changes from H to L. This output is input to the reset terminal (_R) of the RS flip-flop FF, and the output terminal (Q) becomes L. Thereby, the discharge from the capacitor Cx is started. While the output terminal (Q) is L, the discharge from the capacitor Cx is continued. Thereafter, charging and discharging are repeated in this manner, and a triangular wave oscillation signal X is generated.

  The charge / discharge current of the capacitor Cx is determined by the charge / discharge current setting unit 33 (see FIG. 4). Specifically, it is determined by the value of the current flowing through the resistor Ri. The voltage across the resistor Ri is determined by GND and the emitter voltage of the transistor Tr8 that functions as a constant voltage circuit (emitter follower). Therefore, the charge / discharge current of the capacitor Cx is determined by a constant current circuit determined from the output of the constant voltage circuit and the resistor Ri.

  The voltage value of the constant voltage circuit is determined by a value obtained by dividing the input voltage Vi by the resistors R5 and R6. This divided voltage value is transmitted to a constant voltage circuit using the transistor Tr8 via a constant voltage circuit (emitter follower) using the transistor Tr7. The divided value by the resistors R5 and R6 varies with the variation of the input voltage Vi, that is, in proportion to the input voltage Vi. Therefore, the current value defined by the constant current circuit having the resistor Ri also varies in proportion to the input voltage Vi.

  The triangular wave generation unit 32 generates a triangular wave oscillation signal X by charging and discharging the constant current determined in this way with respect to the capacitor Cx. A constant current generated by the constant current circuit flows through the resistor R11 and the transistor Tr1 connected in series to the constant current circuit. The transistors Tr1 and Tr2 have a common base input. Therefore, the series circuit of the resistor R12 and the transistor Tr2 is configured as a mirror with respect to the series circuit of the resistor R11 and the transistor Tr1. That is, a current mirror circuit is configured. Therefore, the constant current (charging current I1) defined by the constant current circuit is supplied to the capacitor Cx connected in series with the resistor R12 and the transistor Tr2. That is, the capacitor Cx is charged with the charging current I1, which is a constant current.

  The series circuit of the resistor R13 and the transistor Tr3 and the series circuit of the resistor R14 and the transistor Tr4 are both mirrored with respect to the series circuit of the resistor R11 and the transistor Tr1. Each of the series circuits including the transistor Tr3 and the transistor Tr4 constitutes a current mirror circuit, and these two series circuits are connected in parallel. Therefore, a current I2 that is twice the charging current I1 flows through the series circuit including the transistor Tr6 and the resistor R16 connected in series to the parallel circuit. The transistor Tr5 has a common base with the transistor Tr6, and these also constitute a current mirror circuit. Therefore, a current I2 (discharge current) that is twice the charging current I1 flows through the series circuit of the transistor Tr5 and the resistor R15.

  A charge / discharge switch F2 is connected in parallel to the series circuit of the transistor Tr6 and the resistor R16. The charge / discharge switch F2 formed of an FET is turned on when the output (Q) of the RS flip-flop is H, and is turned off when the output is L. When the charge / discharge switch F2 is on, the current flowing through the parallel circuit of the transistors Tr3 and Tr4 does not flow through the transistor Tr6 but flows to the ground through the charge / discharge switch F2. Therefore, no current flows through the transistor Tr5 constituting the current mirror, and the capacitor Cx is charged with the charging current I1.

  When the charge / discharge switch F2 is off, the current flowing through the parallel circuit of the transistors Tr3 and Tr4 flows through the transistor Tr6. Accordingly, the discharge current I2 flows through the transistor Tr5 constituting the current mirror. The transistor Tr5 discharges the capacitor Cx in order to flow the discharge current I2. The charging current I1 continues to be supplied to the capacitor Cx. Therefore, the capacitor Cx is discharged with I2−I1 = I1. In this way, the capacitor Cx is charged and discharged with the same current value, so that a triangular wave as shown in FIG. 5 is generated. In this way, the capacitor Cx is charged when the charge / discharge switch F2 is on and discharged when it is off.

In the oscillation circuit 3A, the capacitor Cx is charged and discharged by a constant current (charging current I) that varies in proportion to the input voltage Vi. Therefore, the frequency of the oscillation signal X is kept constant regardless of the fluctuation of the input voltage Vi.
If I2 = I1 × 2 is not set, a triangular wave having another shape such as a sawtooth wave can be generated.

  As described above, according to the present invention, there is provided a stabilized power supply apparatus that can maintain a high efficiency and a high ripple removal effect even when the input voltage fluctuates and obtain a stable and constant output voltage with a simple configuration. can do.

The block diagram which shows typically the structural example of the stabilized power supply device which concerns on this invention Waveform diagram explaining the principle of pulse width control by the pulse control unit of FIG. 1 is a circuit diagram showing a schematic circuit configuration of the stabilized power supply device of FIG. A circuit diagram showing a schematic circuit configuration of the oscillation circuit of FIG. Waveform diagram for explaining the principle of generating a triangular wave oscillation signal by the oscillation circuit of FIG. Block diagram schematically showing a conventional configuration example of a stabilized DC power supply device

Explanation of symbols

1: Switching voltage conversion unit 2: Pulse control unit 3: Oscillation unit 4: Linear voltage conversion unit 5: Error detection unit 10: Switching power supply circuit 20: Linear power supply circuit SP: Control pulse Vi: Input voltage Va: Primary conversion voltage Vo : Output voltage X: Oscillation signal E1: Reference voltage E3: Threshold value E4: Upper limit value E5: Lower limit value Cx: Capacitor I1: Constant current

Claims (3)

A switching voltage converter that switches the input voltage using a control pulse, smoothes it to convert it to a primary conversion voltage, a pulse controller that controls the pulse width of the control pulse, and a triangle that serves as a reference for generating the control pulse An oscillation unit that generates a wavy oscillation signal;
A linear power supply circuit that converts the primary conversion voltage into an output voltage, and a stabilized power supply device connected,
The oscillation unit varies the amplitude of the oscillation signal in proportion to the input voltage, and keeps the frequency of the oscillation signal constant regardless of the input voltage,
The pulse control unit controls the pulse width of the control pulse by pulsing the oscillation signal with a threshold value independently determined for the input voltage and the primary conversion voltage,
A stabilized power supply apparatus in which a potential difference between the primary conversion voltage and the output voltage is kept constant regardless of fluctuations in the input voltage. The linear power supply circuit has an error detection unit that detects an error of the output voltage by comparing a voltage obtained by dividing the output voltage with a predetermined reference voltage,
The oscillating unit uses the lower limit value of the oscillation signal as ground, and changes the amplitude by changing the upper limit value in proportion to the input voltage,
The upper limit value is set to a value obtained by dividing the input voltage by the same voltage division ratio as the error detection unit,
The stabilized power supply device according to claim 1, wherein the threshold value of the pulse control unit is changed according to the error of the output voltage.   The oscillation unit generates the triangular wave oscillation signal by charging and discharging a constant current to and from a capacitor, and the constant current is varied in proportion to the input voltage. 2. The stabilized power supply device according to 2.

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