JP4341641B2 - Power supply - Google Patents

Description

  The present invention relates to a power supply device used as a power supply for electrical equipment, and more particularly to a circuit configuration for stabilizing an output voltage.

  Conventionally, a television receiver, a video device, an audio device, a personal computer, and other electric devices are provided with a power supply device that supplies a power supply voltage to a circuit board on which a predetermined circuit is mounted, a driving mechanism, or the like. As such a power supply device, since a stable voltage is required, a switching power supply device is often used.

  FIG. 3 is a block diagram showing a configuration of a switching power supply device as a conventional power supply device. This switching power supply device includes a DC voltage generation circuit 31 that generates a predetermined DC voltage from a commercial AC power supply (for example, 100V AC power supply) and supplies it as a power supply voltage to each circuit element, a switching element 32, and the switching element. An oscillation circuit 33 that performs an oscillating operation in order to perform a switching operation, a switching transformer 34 that is driven by a switching operation of the switching element 32 connected to the primary side, and a secondary side of the switching transformer 34. A DC voltage output circuit 35 that generates and outputs a DC voltage necessary for the load, and a duty ratio of the oscillation pulse signal of the oscillation circuit 33 so that the output voltage of the DC voltage output circuit 35 can be kept constant. A feedback control circuit for supplying a feedback signal to the oscillation circuit 33. There.

  The operation of the switching power supply device configured as described above will be described. When the plug of the device is inserted into an outlet of a commercial AC power supply 100V and the device is turned on, a predetermined DC voltage is output from the DC voltage generation circuit 31, and the oscillation circuit 33 starts an oscillation operation. When the output voltage of the DC voltage output circuit 35 exceeds a predetermined value, the feedback control circuit 36 outputs a feedback signal for PWM (pulse width modulation) control so that the duty ratio of the oscillation pulse signal of the oscillation circuit 33 is reduced. The oscillation circuit 33 is supplied to the oscillation circuit 33, whereby the oscillation circuit 33 shortens the ON period of the switching element 32, thereby reducing the current on the primary side of the switching transformer 34. As a result, the switching transformer 34 The voltage of the secondary output decreases, and the output voltage of the DC voltage output circuit 35 reaches a predetermined value.

Next, when the output voltage of the DC voltage output circuit 35 divides a predetermined value, the feedback control circuit 36 supplies a PWM control feedback signal to the oscillation circuit 33 so that the duty ratio of the oscillation pulse signal of the oscillation circuit 33 is increased. As a result, the oscillation circuit 33 lengthens the ON period of the switching element 32, thereby increasing the current on the primary side of the switching transformer 34. As a result, the output of the secondary side of the switching transformer 34 is increased. The voltage rises and the output voltage of the DC voltage output circuit 35 reaches a predetermined value.
Japanese Utility Model Publication No. 5-4221

  However, when a switching power supply device is used as the power supply device in this way, a switching transformer, an oscillation circuit, etc. are required to control the switching operation by the switching element so that the output voltage can be kept constant. For this reason, the subject that the number of circuit elements tends to increase and the cost tends to increase arises.

  The prior art described in Patent Document 1 is a voltage stabilizing device for supplying a stable voltage to an electronic circuit, a device, or the like, and in particular, a delay in the rise of the output voltage with respect to the rise of the input voltage. However, it is intended to suppress transmission of a noise signal superimposed on the input terminal from the outside to the output terminal, but the internal configuration of the voltage stabilizing device is not disclosed.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a power supply apparatus that can be configured with a small number of circuit elements to supply a stable voltage.

  In order to achieve the above object, the invention of claim 1 has a series circuit configured by connecting a coil in series to a parallel circuit of a resistor and a variable capacitance element, and an AC power supply is applied to both ends of the series circuit. A power supply voltage output unit that outputs an AC voltage across the resistor, a rectifier that rectifies the AC voltage extracted from both ends of the resistor, and a DC voltage comparison object obtained by rectification using the rectifier Differential amplifying means for amplifying a differential voltage obtained by comparing a voltage with a predetermined reference voltage; and pulse width modulation control means for outputting a pulse signal having a duty ratio set in accordance with the obtained differential voltage; DC voltage converting means for inputting the pulse signal, boosting the pulse signal, converting the pulse signal into a DC voltage having a magnitude corresponding to the duty ratio, and outputting the DC voltage, and output from the DC voltage converting means Ru A feedback control unit configured to supply a current voltage as a capacitance control voltage to the capacitance variable control terminal of the variable capacitance element and perform feedback control so that the AC voltage output from the power supply voltage output unit can be held at a predetermined voltage; A power supply device characterized by the above is provided.

  In this configuration, when the AC voltage across the resistor exceeds a predetermined voltage, the comparison target voltage of the DC voltage from the rectifying means exceeds the reference voltage. As a result, a differential voltage indicating that the voltage to be compared has exceeded the reference voltage is output from the differential amplifying means, and this differential voltage is input to the pulse width modulation control means. Then, a pulse signal exceeding a duty ratio of 50%, for example, corresponding to the differential voltage is output by the pulse width modulation control means. The pulse signal exceeding the duty ratio of 50% is boosted and converted into a DC voltage by the DC voltage converting means. This converted DC voltage becomes a voltage according to the duty ratio of the pulse signal, and is applied to the capacitance variable control terminal of the variable capacitance element as a capacitance control voltage. Since the capacity control voltage in this case corresponds to a pulse signal exceeding a duty ratio of 50%, the capacity control voltage is higher than the reference capacity control voltage and acts to reduce the capacitance of the variable capacitance element. As a result, the capacitance of the variable capacitance element is reduced. As a result, the AC voltage across the resistor is lowered to a predetermined voltage. That is, the output voltage of the power supply device is held at a constant value.

  On the other hand, when the AC voltage across the resistor becomes less than a predetermined voltage, the comparison target voltage of the DC voltage from the rectifying means becomes less than the reference voltage. Thereby, a differential voltage indicating that the comparison target voltage is less than the reference voltage is output from the differential amplifying means, and this differential voltage is input to the pulse width modulation control means. Then, the pulse width modulation control means outputs a pulse signal having a duty ratio of less than 50% corresponding to the differential voltage. A pulse signal having a duty ratio of less than 50% is boosted and converted into a DC voltage by the DC voltage converting means. This converted DC voltage becomes a voltage according to the duty ratio of the pulse signal, and is applied to the capacitance variable control terminal of the variable capacitance element as a capacitance control voltage. Since the capacity control voltage in this case corresponds to a pulse signal with a duty ratio of less than 50%, the capacity control voltage is lower than the reference capacity control voltage and acts to increase the capacitance of the variable capacitance element. The capacitance of the variable capacitance element is increased. As a result, the AC voltage across the resistor rises to a predetermined voltage. That is, the output voltage of the power supply device is held at a constant value.

  According to this configuration, when a circuit is configured using a variable capacitance element to supply a stable voltage, the circuit can be configured with a small number of circuit elements, and the cost can be reduced.

  As described above, according to the present invention, a series circuit configured by connecting a coil in series to a parallel circuit of a resistor and a variable capacitance element is provided, and when the AC power source is applied to both ends of the series circuit, the resistor A power supply voltage output unit that outputs an AC voltage at both ends of the resistor, a rectifying unit that rectifies the AC voltage extracted from both ends of the resistor, and a comparison target voltage of the DC voltage obtained by rectifying by the rectifying unit Differential amplification means for amplifying a differential voltage obtained by comparing with a reference voltage, pulse width modulation control means for outputting a pulse signal having a duty ratio set according to the obtained differential voltage, and the pulse signal DC voltage conversion means for boosting the pulse signal and converting the pulse signal into a DC voltage having a magnitude corresponding to the duty ratio and outputting the DC voltage is provided. The DC voltage output from the DC voltage conversion means has a capacity System As a voltage is provided to the variable capacitance control terminal of the variable capacitance element, and provided with a feedback control unit that performs feedback control so that the AC voltage output from the power supply voltage output unit can be maintained at a predetermined voltage, stable When a circuit is configured using variable capacitance elements to supply voltage, the circuit can be configured with a small number of circuit elements, and cost can be reduced.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a block diagram showing a configuration of a power supply device according to an embodiment of the present invention.

  In FIG. 1, the power supply apparatus includes a power supply voltage output unit 1 that outputs an alternating voltage of a predetermined voltage to a direct current voltage output circuit 3 that supplies a direct current voltage to a load such as an electronic circuit or a drive mechanism (not shown), A feedback control unit 2 that performs feedback control on the power supply voltage output unit 1 so that the output voltage of the voltage output unit 1 becomes a predetermined voltage is provided.

  The power supply voltage output unit 1 includes a coil L, a resistor R, and a variable capacitance element C. The resistor R and the variable capacitor C are connected in parallel, and the coil L is connected in series to a parallel circuit of the resistor R and the variable capacitor C. An AC power source E such as a 100 V commercial AC power source is connected to both ends of a series circuit of a coil L and a parallel circuit of a resistor R and a variable capacitance element C. A DC voltage output circuit 3 is connected to both ends of the resistor R.

  The feedback control unit 2 rectifies the AC voltage (output voltage) Vo extracted from both ends of the resistor R in the power supply voltage output unit 1, and noise-like DC voltage obtained by rectification by the rectifier circuit 4. A low-pass filter 5 for removing a high-frequency component and a series circuit for generating a comparison target voltage Vs for comparison with a reference voltage e by applying a DC voltage from which a noisy high-frequency component is removed by the low-pass filter 5 are configured. A resistor R1 and a resistor R2, a differential amplifier circuit 6 that amplifies the differential voltage between the comparison target voltage Vs and the reference voltage e, and a pulse signal whose duty ratio is set according to the differential voltage from the differential amplifier circuit 6 A PWM (pulse width modulation) control circuit 7 to be output and a pulse signal from the PWM control circuit 7 are input to boost the pulse signal in accordance with the duty ratio. And a boost converter 8 outputs the converted to the magnitude of the DC voltage the DC voltage. The DC voltage output from the boost converter 8 is applied to the capacitance variable control terminals g and h of the variable capacitance element C as a capacitance control voltage.

  The variable capacitance element C includes an equivalent capacitor C1, capacitor C2, capacitor C3, and capacitor C4 constituting a multilayer ceramic capacitor. One end of each of the capacitor C1 and the capacitor C2 is connected to the power input terminal a, and the capacitor C3 and the capacitor One end of C4 is connected to the power input terminal b. The other ends of the capacitors C1 and C3 are connected to the variable capacitance control terminal g, and the other ends of the capacitors C2 and C4 are connected to the variable capacitance control terminal h.

  FIG. 2 is a diagram illustrating an example of characteristics of the variable capacitance element C. In FIG. In FIG. 2, a line F is a characteristic curve showing the relationship of the capacitance of the variable capacitance element C to the capacitance control voltage. According to the characteristic curve indicated by the line F, when the capacitance control voltage is 0 V, the capacitance corresponding to the capacitance of the variable capacitance element C viewed from the capacitance variable control terminals g and h is Cmax = [C1 C2 / (C1 + C2)] + [C3.C4 / (C3 + C4)] However, C1, C2, C3, and C4 in this equation represent capacitances of the capacitors C1, C2, C3, and C4. When the capacitance control voltage is shifted to the plus side or the minus side, as indicated by the line F, the capacitance of the variable capacitance element C decreases. Utilizing such characteristics, the capacitance of the variable capacitance element C is changed, and thereby the AC voltage (output voltage Vo) applied to the resistor R (see FIG. 1) is controlled.

  That is, when the capacitance of the variable capacitance element C changes, the electrostatic energy of the variable capacitance element C changes, thereby changing the electrical work amount of the variable capacitance element C. As a result, it is taken out from both ends of the resistor R. The power will change. Accordingly, when a large amount of current flows through the load (DC voltage output circuit 3 or the like) connected to both ends of the resistor R and the output voltage Vo, which is the voltage across the resistor R, decreases, the power extracted from both ends of the resistor R is reduced. If the voltage is increased, the output voltage Vo can be increased. Therefore, the variable capacitance element C may be controlled so as to increase the capacitance. Conversely, when the output voltage Vo, which is the voltage across the resistor R, rises when the current of the load (DC voltage output circuit 3 or the like) connected to both ends of the resistor R is small and the voltage across the resistor R rises, the electric power extracted from both ends of the resistor R Since the voltage Vo can be lowered by reducing the value of the variable capacitance element C, the capacitance of the variable capacitance element C may be controlled to be small.

  Next, the operation of the power supply device of this embodiment will be described. A DC voltage output circuit 3 is connected to both ends of the resistor R, which is an output of the power supply voltage output unit 1 in this power supply device, and the AC voltage Vi of the AC power source E is applied to the input terminals S1 and S2, whereby the resistor R An AC voltage (output voltage) Vo is generated, an AC voltage Vi is output from the power supply voltage output unit 1, and an AC voltage (output voltage) Vo is supplied to the DC voltage output circuit 3. In addition, in order to detect a change in the AC voltage (output voltage) Vo and keep the AC voltage (output voltage) Vo at a predetermined voltage, the feedback control unit 2 that performs feedback control on the power supply voltage output unit 1 includes a resistor R. An alternating voltage (output voltage) Vo that is a voltage across the both ends is supplied.

  In the feedback control unit 2, the AC voltage (output voltage) Vo supplied from both ends of the resistor R of the power supply voltage output unit 1 is rectified by the rectifier circuit 4 to be converted into a DC voltage. 5 removes a noisy high frequency component. A direct current due to a direct current voltage from which noisy high frequency components have been removed flows through a series circuit of the resistors R1 and R2, and the voltage across the resistor R2 is used as the comparison target voltage Vs. Entered. In the differential amplifier circuit 6, the comparison target voltage Vs is compared with the reference voltage e, and a differential voltage between the comparison target voltage Vs and the reference voltage e is amplified. Note that when the AC voltage (output voltage) Vo, which is the voltage across the resistor R, is a predetermined voltage, the reference voltage e is set so that the differential voltage becomes 0 [V].

  Therefore, as described in FIG. 2, the capacitance of the variable capacitance element C is maximum when the capacitance control voltage is 0 [V]. Cmax = [C1 · C2 / (C1 + C2)] + [C3 · C4 / (C3 + C4)], in order to increase or decrease the capacitance with respect to the reference capacitance, n [V] is set to a reference capacitance control voltage as shown in FIG. 2, and feedback control is performed. The maximum value and the minimum value of the capacitance control voltage are set so that the maximum change width of the capacitance necessary for the above can be obtained. For example, as shown in FIG. 2, an approximate linear section of line F is used, and in this case, the capacitance control voltage when the capacitance reaches the maximum value m1 [μF] is n1 [V], and the capacitance is The capacity control voltage when the minimum value is m2 [μF] is set as n2 [V].

  In addition, by using the approximate linear section of the line F, it becomes easy to control the capacitance to be changed by the capacitance control voltage. That is, the operation of the capacitance control voltage within the approximate linear section of the characteristic line indicating the relationship between the capacitance control voltage applied to the capacitance variable control terminals g and h of the variable capacitance element C and the capacitance of the variable capacitance element C. By bringing the point and performing linear control for changing the capacitance of the variable capacitance element C, control for changing the capacitance by the capacitance control voltage is facilitated.

  The differential voltage from the differential amplifier circuit 6 is input to the PWM control circuit 7, and the PWM control circuit 7 outputs a pulse signal having a duty ratio corresponding to the differential voltage. In the PWM control circuit 7, when the differential voltage is 0 [V], for example, a pulse signal with a duty ratio of 50% is output, and when the differential voltage is plus [V], the duty ratio is 50 % And the differential voltage is minus [V], the duty ratio is less than 50%. Therefore, in the step-up converter 8, when a pulse signal having a duty ratio of 50% is input from the PWM control circuit 7, the 50% pulse signal is boosted and converted into a DC voltage, and the DC voltage at this time is n [ V], and is applied as the capacitance control voltage n to the capacitance variable control terminals g and h of the variable capacitance element C. Since the capacitance control voltage n is set as the reference capacitance control voltage as described above, the variable capacitance The capacitance of the element C does not change and remains m [μF].

  Further, in the step-up converter 8, when a pulse signal having a duty ratio exceeding 50% is input from the PWM control circuit, the pulse signal exceeding the duty ratio of 50% is boosted and converted into a DC voltage. The voltage according to the ratio (a voltage higher than the reference capacitance control voltage n) is applied, and the DC voltage at this time is applied to the capacitance variable control terminals g and h of the variable capacitance element C as the capacitance control voltage. The capacitance becomes smaller. In this case, the AC voltage (output voltage) Vo is higher than a predetermined voltage. When the capacitance of the variable capacitance element C is reduced, the AC voltage (output voltage) that is the voltage across the resistor R is obtained. Vo drops to a predetermined voltage.

  Further, in the step-up converter 8, when a pulse signal having a duty ratio of less than 50% is input from the PWM control circuit, the pulse signal having a duty ratio of less than 50% is boosted and converted into a DC voltage. Becomes a voltage corresponding to the duty ratio (a voltage lower than the reference capacity control voltage n), and this DC voltage is applied to the capacity variable control terminals g and h of the variable capacity element C as the capacity control voltage. The capacitance increases. In this case, the AC voltage (output voltage) Vo is lower than the predetermined voltage. By increasing the capacitance of the variable capacitance element C, the AC voltage (output voltage) that is the voltage across the resistor R is obtained. Vo rises to a predetermined voltage.

  In this embodiment, the operating point of the capacity control voltage is brought to the approximate straight line section of the right line as seen from the line F shown in FIG. 2, but the operating point of the capacity control voltage is approximated to the left line. You may bring it to the target straight section. In this case, if the capacitance control voltage is lowered, the capacitance of the variable capacitance element C is reduced. Therefore, if feedback control is performed corresponding to this, the same effect can be obtained.

  As described above, according to the present embodiment, if a circuit is configured using variable capacitance elements to supply a stable voltage, the circuit can be configured with a small number of circuit elements, and the cost can be reduced.

  INDUSTRIAL APPLICABILITY The present invention can be used for a power supply device for electrical equipment that requires a stable power supply voltage.

It is a block diagram which shows the structure of the power supply device which concerns on one Embodiment of this invention. It is a figure which shows an example of the characteristic of a variable capacitance element in the said embodiment. It is a block diagram which shows the structure of the switching power supply device as a conventional power supply device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Power supply voltage output part 2 Feedback control part 4 Rectifier circuit (rectifier means)
6 Differential amplification circuit (Differential amplification means)
7 PWM control circuit (pulse width modulation control means)
8 Boost converter (DC voltage conversion means)

Claims (1)

A power supply voltage that has a series circuit configured by connecting coils in series to a parallel circuit of a resistor and a variable capacitance element, and outputs an AC voltage across the resistor when an AC power supply is applied to both ends of the series circuit An output section;
Rectifying means for rectifying the AC voltage taken out from both ends of the resistor, and amplifying a differential voltage obtained by comparing the comparison target voltage of the DC voltage obtained by rectifying with the rectifying means and a predetermined reference voltage Differential amplifying means, pulse width modulation control means for outputting a pulse signal having a duty ratio set in accordance with the obtained differential voltage, and input of the pulse signal to boost the pulse signal in accordance with the duty ratio DC voltage conversion means for converting to a DC voltage of a predetermined magnitude and outputting the DC voltage, and using the DC voltage output from the DC voltage conversion means as a capacity control voltage to the capacity variable control terminal of the variable capacitance element And a feedback control unit that performs feedback control so that the AC voltage output from the power supply voltage output unit can be maintained at a predetermined voltage. .

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