JP2006187159A - Resonance switching power supply - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resonance switching power supply in which the output voltage can be controlled to sustain a predetermined level stably while keeping the switching frequency of a pulse current being generated depending on the output state of the power supply. <P>SOLUTION: The resonance switching power supply is constituted of a control circuit 11, a switching circuit 13 including transistors Q1 and Q2, a resonance circuit 14 including an inductor L1 and a capacitor C1, a smoothing circuit 15 including an inductor L2 and a capacitor C2, and an output current detecting load 16 formed of a resistor R wherein a step-down DC/DC converter 12 of a DC input voltage V<SB>IN2</SB>for driving the switching power supply is provided on the main power supply side. Output detecting means 17 of the control circuit 11 detects the output voltage V<SB>OUT</SB>and the output current I<SB>OUT</SB>to a load by the output terminal T<SB>OUT</SB>and an output current detecting load 16, controls the output resonance frequency to a predetermined level or above so that countermeasure against ripple is not required even under light load, and controls the DC input voltage V<SB>IN2</SB>based on the detected output value V<SB>OUT</SB>/I<SB>OUT</SB>so that the output voltage V<SB>OUT</SB>is sustained at a predetermined level. The converter may be an AC/DC converter. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a miniaturized resonant switching power supply device that can easily obtain a stable DC output from a DC input voltage.

  In the conventional switching power supply device, PWM (Pulse Width Modulation) control that stabilizes the DC output voltage by controlling the output voltage by changing the ratio of the ON time and OFF time of the switching transistor at a fixed period, There is PFM (Pulse Frequency Modulation) control that stabilizes the DC output voltage by changing the off time while fixing the on time of the transistor.

  In the PWM control, when the output voltage decreases, the on-time is lengthened, and when the output voltage increases, the time is shortened, so that an output current corresponding to the load can be supplied and a constant output voltage can always be maintained. On the other hand, in PFM control, when the input voltage increases or the output current increases, the frequency is reduced and the output is adjusted by increasing the frequency under the opposite conditions. Often used for control of type power supply devices.

  That is, in a resonance type power supply, a pulsed current or voltage generated by transistor switching is set by a resonance circuit using an LC element connected to the output side. difficult. Therefore, PFM control is generally used for the resonance type power supply device.

For example, the power supply unit shown in FIG. 1, IC is formed by (integrated circuit) supplied with a constant DC voltage V _IN control circuit 10, a transistor connected between one end of the DC constant voltage V _IN and the inductor L1 Q1, and inductor connected in series between the switching circuit consisting of two FET (field effect transistor) of the connected transistor Q2 between the other end and the ground potential of the inductor L1, a transistor Q1 and the output terminal T _OUT L1 and L2 and smoothing capacitors C1 and C2 connected to the output terminals T _OUT of the inductors L1 and L2, respectively. The inductor L1 and the capacitor C1 form a resonance circuit.

The control circuit 10 connects the two control terminals to the gate of the transistor Q1 · Q2, also connected to the output terminal T _OUT detecting the output voltage V _OUT between the potential and the ground. Further, the control circuit 10 controls the pulse frequency of the control signal supplied to the transistors Q1 and Q2 according to the detected voltage fluctuation of the output voltage _VOUT , changes the switching frequency of the switching circuit, and controls the switched output current i. Thus, the output voltage V _OUT is kept constant. The transistors Q1 and Q2 are CMOS (complementary metal oxide semiconductor) FETs. The drain of the transistor Q1 is supplied with a DC constant voltage _VIN , and the source of the transistor Q2 is grounded.

  Therefore, as shown in FIG. 2, when the current amount of the pulsed output current i may be small with a light load, the control circuit 10 increases the off time with respect to a certain amount of on time. On the other hand, when it is necessary to increase the output current i with a heavy load, so-called PFM control is performed in which the switching frequency of the switching circuit is increased by shortening the off time with respect to a certain amount of on time. Do.

  The switching power supply device having such a configuration is practically sufficient for fluctuation within a predetermined range. However, when the switching frequency is lowered with a light load, the pulse interval is widened. Therefore, it is necessary to secure the capacitance of the output-side capacitor C2 to prevent this ripple, and it is difficult to downsize the capacitor C2 and the like. There were drawbacks.

  The problem to be solved is that the smoothing capacitor and the like cannot be reduced in size due to the ripple countermeasure of the current resonance type power supply output, and the size of the apparatus cannot be avoided.

As described above, in the conventional current resonance type switching power supply, the control circuit to which the DC constant voltage V _IN is supplied generates a control signal with pulses having the same time width and the same amplitude, so that the switching frequency of the switching circuit is changed. The output voltage is maintained at a predetermined value.

  However, in the resonance type switching power supply according to the present invention, the switching frequency of the switching circuit is made constant by the control of the control circuit, and the DC input voltage supplied to the control circuit and the switching circuit is changed according to the output state of the power supply device. Thus, the amplitude of the pulsed output current is changed.

That is, according to the present invention, in a resonant switching power supply device that obtains a stable DC output from a DC input voltage (V _IN2 ), a ripple countermeasure for a low switching frequency is unnecessary when the DC output is lightly loaded. The control circuit (11), which receives the DC input voltage (V _IN2 ) and controls the DC output, detects the value of the output current (I _OUT ) supplied to the load together with the output voltage (V _OUT ). However, the DC input voltage (V _IN2 ) input to this control circuit (11) is controlled based on the detected output voltage (V _OUT ) and output current (I _OUT ) so that the ripple countermeasure is unnecessary. The main feature is that the output voltage (V _OUT ) is maintained at a predetermined value by changing the amplitude of the pulsed output current (i) while maintaining the output switching frequency at a predetermined value.

  That is, the control circuit controls the DC input voltage input to itself when periodically obtaining the output current value and controlling the increase / decrease. Therefore, the power source for driving the resonance type power source may be any of DC / AC (direct current / alternating current) as long as it has a corresponding converter. The switching power supply can be applied to either a current resonance type or a voltage resonance type.

For example, according to the present invention, a DC output converter (11) for generating and outputting a DC input voltage V _IN2 in the switching power supply from a large-capacity main power supply voltage V _IN and a DC input voltage V _IN2 received from the converter are predetermined. A control circuit (12) for outputting a pulse control signal having a predetermined time width at intervals, a switching circuit (13) for receiving a pulse control signal from the control circuit and performing a switching operation to output a periodic pulsed current; A resonance circuit (14) that receives a periodic output of the switching circuit and outputs a pulsed current having a predetermined resonance frequency, a smoothing circuit (15) for DC output, and an output current connected to the output terminal An output current detection load (16) that passes through and notifies the control circuit of the potential at both ends is provided. The control circuit detects the output voltage V _OUT from the potential difference between the output terminal and the ground, and cooperates with the output current detection load to detect the output current I _OUT from the potential at both ends and the ground potential. (17), and notifies the converter of changes in the output voltage V _OUT and the output current I _OUT and changes the output DC input voltage V _IN2 to control the output voltage V _OUT to be maintained at a predetermined value. .

The present invention also includes means for controlling the switching frequency to be equal to or higher than a predetermined value so as to maintain the output voltage _VOUT at a predetermined value.

  The reference numerals in the parentheses are given for easy understanding, are merely examples, and are not limited thereto.

  The resonant switching power supply device of the present invention includes a DC output converter that converts a main power supply voltage into a DC input voltage and outputs the same, and a control circuit controls the converter by obtaining information on the output voltage and output current of the power supply device. Then, the DC input voltage of the output can be changed. In this way, the DC input voltage supplied to the control circuit and the switching circuit can be controlled, so that the switching frequency of the generated pulsed current is maintained at a predetermined value or more according to the output state of the power supply device. There is an effect that the output voltage can be controlled to be stably maintained at a predetermined value.

  Therefore, since the pulse period does not increase, the power supply device can be downsized with the downsizing of the smoothing circuit regardless of the addition of the DC output converter.

According to the present invention, in a resonant switching power supply device that obtains a stable DC output from a DC input voltage, the object of eliminating the need for ripple countermeasures for low frequencies when the DC output of the power supply device is lightly loaded is achieved. That is, the control circuit that controls the DC output in response to the DC input voltage V _IN2 detects the output current I _OUT supplied to the load together with the output voltage V _OUT , and sets the detected output voltage V _OUT or the output current I _{OUT to} the detected value. Based on this, the DC input voltage V _IN2 input to this control circuit is controlled, and the output voltage V _OUT is maintained while maintaining the resonance frequency that is output so as not to require ripple countermeasures even at light loads, at a predetermined value or higher. Is controlled to be maintained at a predetermined value.

  For this reason, a DC output converter is additionally provided in the power supply device, and this DC output converter generates a DC input voltage supplied by an internal circuit of the power supply device from an external main power supply voltage. Therefore, the control circuit controls the DC output converter, changes the DC input voltage output from the DC output converter and input to the control circuit, and adjusts the output voltage to be maintained at a predetermined value.

  A first embodiment of the present invention will be described with reference to FIG.

  FIG. 3 is an explanatory diagram showing a block circuit of the first embodiment in the resonant switching power supply device according to the present invention.

The illustrated switching power supply device is a current resonance type, and includes a control circuit 11, a step-down DC / DC converter 12, a switching circuit 13 including transistors Q1 and Q2, a resonance circuit 14 including an inductor L1 and a capacitor C1, and an inductor L2. It comprises a smoothing circuit 15 including a capacitor C2 and an output current detection load 16 formed by a resistor R. The inductors L1 and L2 and the resistor R are connected in series from the transistor Q1 to the output terminal T _OUT .

The control circuit 11 is connected to one end of the output current detection load 16 by inputting the DC input voltage V _IN2 output from the step-down DC / DC converter 12 and drawing both ends of the output current detection load 16 to obtain a potential difference from the ground. Detecting the output voltage V _{OUT at} the output terminal T _OUT and the output current I _OUT supplied to the load flowing through the output current detection load 16 and outputting control signals to the step-down DC / DC converter 12 and the switching circuit 13 respectively. Thus, the output voltage V _OUT is adjusted to be maintained at a predetermined value.

  That is, the control circuit 11 is formed of, for example, an IC (integrated circuit), and generates a pulsed current with a predetermined switching frequency using the switching circuit 13 and the resonance circuit 14, and generates the generated current i at this time. It must be small for light loads and large for heavy loads.

For this reason, the control circuit 11 sends a control signal to the step-down DC / DC converter 12 and controls the output DC input voltage V _IN2 to be low when the load is light and high when the load is heavy. . In this case, the control circuit 11 controls the DC input voltage V _IN2 output at the maximum load so as to become the main power supply voltage V _IN . The control circuit 11 has a control terminal connected to the gates of the transistors Q1 and Q2 of the switching circuit 13, and sends out a pulse control signal having a predetermined time width at predetermined intervals.

The step-down DC / DC converter 12 inputs a DC constant voltage V _IN from a main power source such as a battery, forms a DC power source for controlling the IC, and outputs a DC input voltage V _IN2 . Furthermore, the step-down DC / DC converter 12, the control circuit based on the control signal received from the 11, by changing the DC input voltage V _IN2, DC constant voltage V of the DC input voltage V _IN2 is mains to be output during the maximum load Controlled to be _IN .

The switching circuit 13 includes transistors Q1 and Q2 formed of series CMOSFETs, and is supplied with the DC input voltage V _IN2 output from the step-down DC / DC converter 12 in the same manner as the control circuit 11, and is switched to generate a pulsed generated current. i is output from the transistor Q 1 to the resonance circuit 14.

  The resonance circuit 14 connects the inductor L1 and the capacitor C1 having a series configuration, and outputs a pulsed current with a resonance frequency determined by the inductor L1 and the capacitor C1 as a switching frequency from a connection point between the inductor L1 and the capacitor C1. To do.

  The smoothing circuit 15 connects the inductor L2 and the capacitor C2 in series in parallel with the capacitor C1 of the resonance circuit 14, and connects the connection point between the inductor L2 and the capacitor C2 to the output terminal, and is output from the resonance circuit 14. The pulsed current having the switching frequency is smoothed to a direct current.

The output current detection load 16 includes a resistor R, and is inserted and connected between the inductor L2 of the smoothing circuit 15 and the connection point between the output terminal _TOUT and the capacitor C2. Both ends of the output current detection load 16 are drawn into the control circuit 11 to form an output detection means 17, and the output detection means 17 is based on the potential difference between the both ends of the output current detection load 16 and the output terminal side ends and the ground. The output voltage V _OUT and the output current I _{OUT of the} power supply device are detected and the control signal described above is output to the step-down DC / DC converter 12 and the switching operation of the switching circuit 13 is controlled.

  Next, the operation function of the control circuit 11 shown in FIG. 3 will be described with reference to FIG.

As described above with reference to FIG. 2, in the conventional current resonance type switching power supply to which the DC constant voltage V _IN is supplied, the control circuit generates current pulses having the same amplitude. Therefore, the switching frequency is changed. Yes. That is, PFM control is performed.

  However, in the current resonance type switching power supply according to the present invention, the DC input voltage supplied to the control circuit and the switching circuit is changed according to the output state of the power supply device under the condition that the period of the pulse current is constant. That is, since a small current may be supplied at a light load, the input power supply applied to the control circuit 11 may be at a low potential. On the other hand, since a large current is required in heavy load, a high potential is required.

Therefore, the control circuit 11 detects the load state from the output voltage V _OUT and the output current I _OUT of the power supply device, and sends a control signal to the step-down DC / DC converter 12 provided on the main power supply voltage V _IN side. The DC input voltage V _IN2 supplied to the control circuit 11 is controlled as described above, and the output voltage V _OUT is maintained at a predetermined value.

  In the above description, an IC is used for the control circuit, two CMOSFETs are used for the switching circuit, and a resistor is used for the current detection load. Also good. Further, although the current resonance type has been described, the current amplitude described above can be controlled by converting it into a voltage amplitude, so that it is apparent that the present invention can also be applied to the voltage resonance type.

  Since the configuration according to such a form is adopted, the interval between the pulsed currents output at the time of light load can be fixed to a predetermined value. Therefore, since the capacity of the smoothing capacitor corresponding to the ripple can be reduced as compared with the conventional case, there is an effect that the power supply device can be downsized even if a converter is added.

  The same effect can be obtained with respect to the ripple in the control method of adjusting the amplitude by setting the interval of the pulsed current output at the time of light load to a predetermined value or less.

  A second embodiment of the present invention will be described with reference to FIG.

  The second embodiment of FIG. 5 includes an AC / DC converter 18 instead of the step-down DC / DC converter 12 of the first embodiment. Therefore, a smoothing capacitor C0 is inserted on the output side of the AC / DC converter 18.

With such a configuration, the main power source can be a commercial AC power source, for example, and the AC constant voltage V _AC can be used for the input of the power supply device. The other components are the same as those described with reference to FIG.

  This function means that the main power supply voltage supplied to the switching power supply according to the present invention can be selected from either DC or AC.

  Using a DC / DC or AC / DC converter at the input part of the main power supply in the resonance type switching power supply device, the control circuit can easily fix the pulse generation period of the switching power supply part to a predetermined value while varying its amplitude, or Since the amplitude can be adjusted by setting the pulse generation period to a predetermined value or more, it can be applied to miniaturization of power supply applications that require smoothing of the output pulse using a switching circuit.

It is explanatory drawing which showed an example of the circuit block structure in the conventional resonant switching power supply device. It is explanatory drawing which shows an example of the resonance waveform by PFM control in FIG. It is explanatory drawing which showed one Embodiment of the circuit block structure in the resonance type switching power supply device by this invention. Example 1 FIG. 4 is an explanatory diagram showing one form of a resonance waveform of a generated current i in the circuit of FIG. 3. Example 1 It is explanatory drawing which showed one Embodiment of the circuit block structure in the resonance type switching power supply device by this invention. (Example 2)

Explanation of symbols

11 Control circuit 12 Step-down DC / DC converter (DC output converter)
DESCRIPTION OF SYMBOLS 13 Switching circuit 14 Resonance circuit 15 Smoothing circuit 16 Output current detection load 17 Output detection means 18 AC / DC converter (DC output converter)
C0, C1, C2 Capacitor L1, L2 Inductor Q1, Q2 Transistor R Resistor

Claims (8)

In a resonant switching power supply apparatus that obtains a stable DC output via a resonant circuit and a smoothing circuit from a pulsed current or voltage generated by a control circuit and a switching circuit that operate with a DC input voltage,
A DC output converter that outputs the DC input voltage and supplies the DC circuit to the control circuit and the switching circuit; and output detection means that detects at least one of a voltage value and a current value of the DC output as an output value. ,
The control circuit receives the output value from the output detection means, and controls the DC output converter based on the output value to change the DC input voltage and to make the output frequency of the switching circuit equal to or higher than a certain value. The resonance type switching power supply device, characterized in that the control is performed so as to be maintained at The resonant switching power supply device according to claim 1,
The switching circuit is controlled so as to change the amplitude of the pulsed output under the control of the control circuit and adjust the voltage of the DC output to a predetermined value. The resonant switching power supply device according to claim 1 or 2,
The output detection means is included in the control circuit and includes an output current detection load,
The load is inserted into a line through which an output current flows inside a smoothing circuit connected to the output of the resonance circuit, and notifies the control circuit of the potential at both ends thereof.
The control circuit detects an output current of the power supply device from a ground and both-end potentials of the load, and outputs an output voltage from the ground and an output terminal, respectively, to obtain an output value. .   2. The resonant switching power supply device according to claim 1, wherein the DC output converter is a DC / DC converter or an AC / DC converter that inputs one of direct current (DC) and alternating current (AC) as a main power supply voltage. A resonance-type switching power supply device comprising:   2. The resonant switching power supply device according to claim 1, wherein the switching circuit is composed of two CMOSFETs.   2. The resonant switching power supply device according to claim 1, wherein the output current detection load is a resistor. A DC output converter that generates and outputs a DC input voltage from the main power supply voltage; and
A control circuit for receiving the DC input voltage from the converter and outputting a pulse control signal having a predetermined time width at predetermined intervals;
A switching circuit that receives the pulse control signal from the control circuit, performs a switching operation, and outputs a pulsed current or voltage having a predetermined resonance frequency; and a resonance circuit;
A smoothing circuit for receiving a pulsed current or voltage having the resonance frequency and outputting a direct current;
An output current detection load connected to the output terminal and passing the output current and notifying the control circuit of the potential at both ends;
The control circuit detects the output voltage from the potential difference between the output terminal and the ground, and detects the output current upon receiving the notification of the both-end potential with respect to the ground from the output current detection load. Resonant switching power supply apparatus comprising: means for notifying the converter and changing a DC input voltage to be output, and controlling the output voltage to be maintained at a predetermined value by the change of the DC input voltage. In a resonant switching power supply device that obtains a stable DC output from a DC input voltage,
A DC output converter for obtaining the DC input voltage from a main power supply voltage;
Output detection means for detecting at least one of a voltage value and a current value of the DC output as an output value;
The output detection unit receives the output value, and controls the DC output converter according to the output value to change the DC input voltage and control the switching frequency to be a predetermined value or more, And a control unit that adjusts the voltage so as to maintain the voltage at a predetermined value.

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