JP2010081736A - Ac/dc converter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize an operation by high precision and a high-power factor in an AC/DC converter of a two-stage structure. <P>SOLUTION: In an AC/DC conversion part 41A of the AC/DC converter, switching driving of a switching element SW2 in an AC/DC conversion part 2 is controlled by using a timing control signal Sa based on a sampled detection signal S(Vin) and a detection signal S(Iin). Thus, a highly precise PFC operation is realized in the AC/DC conversion part 2. A period Ta of the timing control signal Sa and periods Tb of the timing control signals Sb1 and Sb2 become almost the same, and phases of the timing control signals Sb1 and Sb2 are set to advance to the phase of the timing control signal Sa. Thus, switching noise due to the switching element SW2 is reduced at the time of sampling in the A/D conversion part 41A. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an AC / DC converter having a two-stage configuration of an AC / DC converter and a DC / DC converter.

  In recent years, various large-capacity power storage devices have been developed against the background of power electronics technology. For example, a plug-in hybrid electric vehicle (PHEV) has been proposed as a use application of such a large-capacity power storage device. When charging with this PHEV, power is supplied from a commercial power supply (AC power supply) to a battery mounted in the PHEV via an AC / DC converter that functions as a charger.

  The PHEV AC / DC converter is required to be small and lightweight in order to be mounted on a vehicle. Therefore, a switching converter is used for this AC / DC converter. Further, in order to obtain power from a commercial power source, such a switching converter is required to reduce the harmonic current on the input side to some extent according to the standard. Therefore, in order to cope with this (in order to increase the power factor), the AC / DC converter for PHEV is generally equipped with a circuit having a PFC (Power Factor Correction) function.

  Here, such an AC / DC converter circuit requires a step-up / step-down function. However, only an AC / DC converter having a PFC function can have only a boost function.

  Thus, for example, Patent Documents 1 to 3 propose a two-stage converter in which an AC / DC converter having the above-described PFC function is provided at the front stage and a DC / DC converter is provided at the rear stage. Here, the DC / DC converter in the subsequent stage is in charge of the step-down function. At this time, if the two-stage converter is controlled by separate control circuits, the control circuit scale increases and the area occupied by the control circuit increases. Therefore, in recent years, digital control in which these controls are performed by a single DSP (Digital Signal Processor) has been proposed (for example, Patent Document 4).

JP 2001-37226 A JP 2007-110856 A JP 2008-125316 A JP 2007-288892 A

  By the way, in order to perform high-precision control to satisfy the harmonic current regulation by PFC operation in the previous stage AC / DC converter, the input current and input voltage to this AC / DC converter must be accurately grasped. Therefore, it is necessary to perform PFC control based on the information. Therefore, in the DSP, it is desired to generate a timing control signal that enables such highly accurate PFC control.

In order to grasp the input current and the input voltage, it is conceivable that the DSP takes in a digital detection signal via an internal or external A / D converter. The most suitable timing for this capture is when the switching operation is performed during the PFC operation. On the other hand, at the timing of such a switching operation, it is difficult to obtain an accurate value particularly for the input current due to switching noise. Therefore, the DSP is desired to generate a timing control signal in consideration of switching noise during such PFC operation.

  The present invention has been made in view of such problems, and an object of the present invention is to provide an AC / DC converter capable of performing high-accuracy and high-power factor operation in a two-stage AC / DC converter. It is in.

  The first AC / DC converter of the present invention includes a first switching element, and includes an AC / DC converter that generates a DC input voltage based on an AC input voltage, and a second switching element. A DC / DC converter configured to generate a DC output voltage and an input current flowing into the AC / DC converter are periodically sampled at a predetermined timing by performing voltage conversion based on the DC input voltage. First and second timing control signals are generated based on the sampling means and at least the input current sampled by the sampling means, and pulse width modulation is performed on the first switching element using the first timing control signal. In addition to switching driving, the second timing control signal is used to change the pulse width for the second switching element. By those having a control unit for switching drive. Here, the period of the first timing control signal and the period of the second timing control signal are substantially the same as each other, or one is an integral multiple of the other. In addition, the phase of the second timing control signal is set to advance with respect to the phase of the first timing control signal. The “AC input voltage” includes a voltage used as a power supply voltage for electrical equipment, and is preferably used for a so-called commercial power supply.

  In the first AC / DC converter of the present invention, the AC / DC converter generates a DC input voltage based on the AC input voltage, and the DC / DC converter performs voltage conversion based on the DC input voltage. As a result, a DC output voltage is generated. At this time, the input current flowing into the AC / DC converter is periodically sampled at a predetermined timing, and the first and second timing control signals are generated based on at least the sampled input current. The first switching element is switched and driven by pulse width modulation using the first timing control signal, and the second switching element is switched and driven by pulse width modulation using the second timing control signal. Is done. In this way, the switching drive of the first switching element is controlled using the first timing control signal based on the sampled input current to the AC / DC converter, so that the AC / DC converter High-precision PFC operation is possible. The period of the first timing control signal and the period of the second timing control signal are substantially the same as each other or one is an integral multiple of the other, and the phase of the second timing control signal is the first By setting so as to advance with respect to the phase of the timing control signal, the input current sampling operation is performed before the switching operation of the first switching element based on the second timing control signal. Thus, switching noise during sampling is reduced.

  In the first AC / DC converter of the present invention, it is preferable that the second timing control signal also serves as a timing control signal for sampling the input current. When the sampling means further samples the AC input voltage periodically at a predetermined timing, the second timing control signal further includes a timing control signal for sampling the AC input voltage. It is more preferable to serve as both. In such a configuration, it is not necessary to separately provide a timer or the like for the timing control signal at the time of sampling, so that the configuration of the entire AC / DC converter is simplified.

In the first AC / DC converter of the present invention, the time corresponding to the phase difference between the first timing control signal and the second timing control signal is made longer than the delay time required for the sampling operation by the sampling means. Preferably it is set. In such a configuration, since the sampling operation of the input current is reliably performed before the switching operation of the first switching element, the switching noise at the time of sampling can be completely avoided.

  In the first AC / DC converter of the present invention, it is preferable that the period of the first timing control signal is set to be longer than the period of the second timing control signal. When configured in this way, conversely, compared with the case where the cycle of the first timing control signal is set to be shorter than the cycle of the second timing control signal, the AC / DC converter and the DC / DC The operation of the converter is facilitated, and the efficiency of the entire AC / DC converter is improved.

  In the first AC / DC converter of the present invention, the AC / DC converter includes a booster circuit having a power factor improving function using the first switching element, and the DC / DC converter performs a step-down operation. It is possible to configure.

  In the first AC / DC converter of the present invention, the sampling means performs sampling using A / D conversion, and the control unit is configured using a single digital arithmetic device (DSP). It is possible to do so.

  The second AC / DC converter of the present invention is based on an input voltage input from one input / output terminal pair of the first and second input / output terminal pairs and outputs an output voltage from the other input / output terminal pair. And an AC / DC converter arranged on the first input / output terminal side and including the first switching element, and arranged on the second input / output terminal side. A DC / DC converter configured to include a switching element, sampling means for periodically sampling an inflow current flowing into the AC / DC converter at a predetermined timing, and an inflow current sampled by at least the sampling means The first timing control signal is generated based on the first timing control signal, and the first timing control signal is used to switch the first switching element by pulse width modulation. It performs, in which a control unit for switching driving by the pulse width modulation to the second switching element by using the second timing control signal. Here, the period of the first timing control signal and the period of the second timing control signal are substantially the same as each other, or one is an integral multiple of the other. In addition, the phase of the second timing control signal is set to advance with respect to the phase of the first timing control signal.

In the second AC / DC converter of the present invention, during forward operation, an AC input voltage is input from the first input / output terminal pair, and the AC / DC conversion unit generates a DC input voltage based on the AC input voltage. Generated. In the DC / DC converter, voltage conversion is performed based on the DC input voltage to generate a DC output voltage and output it from the second input / output terminal pair. On the other hand, during reverse operation, a DC input voltage is input from the second input / output terminal pair, and the DC / DC converter performs voltage conversion based on the DC input voltage to generate a transformed DC voltage. The In the AC / DC converter, an AC output voltage is generated based on the transformed DC voltage, and is output from the first input / output terminal pair. At this time, the inflow current flowing into the AC / DC converter is periodically sampled at a predetermined timing, and the first and second timing control signals are generated based on at least the sampled inflow current. The first switching element is switched and driven by pulse width modulation using the first timing control signal, and the second switching element is switched and driven by pulse width modulation using the second timing control signal. Is done. In this way, the switching driving of the first switching element is controlled using the first timing control signal based on the sampled inflow current to the AC / DC conversion unit, so that A
High-precision PFC operation is possible in the C / DC converter. The period of the first timing control signal and the period of the second timing control signal are substantially the same as each other or one is an integral multiple of the other, and the phase of the second timing control signal is the first By setting so as to advance with respect to the phase of the timing control signal, the input current sampling operation is performed before the switching operation of the first switching element based on the second timing control signal. Thus, switching noise during sampling is reduced.

  According to the AC / DC converter of the present invention, the switching drive of the first switching element is controlled using the first timing control signal based on the sampled input current (or inflow current) to the AC / DC converter. As a result, it is possible to perform a highly accurate PFC operation in the AC / DC converter. The period of the first timing control signal and the period of the second timing control signal are substantially the same as each other or one is an integral multiple of the other, and the phase of the second timing control signal is the first Since the phase is advanced with respect to the phase of the timing control signal, the switching noise at the time of sampling can be reduced. Therefore, the AC / DC converter having a two-stage configuration can be operated with high accuracy and high power factor.

  Hereinafter, the best mode for carrying out the present invention (hereinafter simply referred to as an embodiment) will be described in detail with reference to the drawings.

  FIG. 1 shows a block configuration of an AC / DC converter (AC / DC converter 1) according to an embodiment of the present invention. The AC / DC converter 1 is applied to an automobile, for example, and performs a step-up / step-down operation based on an AC input voltage Vacin (so-called commercial voltage) supplied from a commercial power supply 10 to charge a battery 50. It is. The AC / DC converter 1 includes an AC / DC converter 2, a DC / DC converter 3, and a controller 4. That is, the AC / DC converter 1 is an AC / DC converter having a two-stage configuration of an AC / DC converter 2 and a DC / DC converter 3.

  The AC / DC converter 2 generates a DC voltage Vdc1 by performing AC / DC (AC / DC) conversion on the AC input voltage Vacin. The AC / DC converter 2 has a PFC function by a booster circuit 24 described later. The detailed configuration of the AC / DC converter 2 will be described later (FIG. 2).

  The DC / DC converter 3 performs DC / DC (direct current / direct current) conversion on the direct current voltage Vdc1, thereby transforming the DC output voltage Vdcout to be supplied to the battery 50 (here, stepped down). Is generated. The detailed configuration of the DC / DC converter 3 will be described later (FIG. 2).

  The control unit 4 controls the operation of the AC / DC conversion unit 2 and the DC / DC conversion unit 3, and includes an arithmetic unit 40, two A / D conversion units 41A and 41B, and two timers 42A and 42B. And have.

The A / D conversion unit 41A performs A / D (analog / digital) conversion on the detection signal S (Vin) and the detection signal S (Iin) supplied from the AC / DC conversion unit 2 to perform digital Detection signal D (Vin) and detection signal D (Iin). The A / D conversion unit 41B generates a digital detection signal D (Vout) by performing A / D conversion on the detection signal S (Vout) supplied from the DC / DC conversion unit 3. It is. These A / D converters 41A and 41B are provided with detection signals S (Vin), S (Iin), S (Vout
) Are periodically sampled at a predetermined timing, which will be described later, and A / D conversion is performed.

  The arithmetic unit 40 is based on the detection signal D (Vin) and detection signal D (Iin) supplied from the A / D conversion unit 41A and the detection signal D (Vout) supplied from the A / D conversion unit 41B. An arithmetic process is performed to generate a control signal that is a basis of timing control signals Sa, Sb1, and Sb2, which will be described later, and supplied to timers 42A and 42B. The function of the arithmetic unit 40 is configured by software, and all processing by the arithmetic unit 40 is performed by a digital signal processing device. Such a digital signal processing device is preferably composed of, for example, a logic circuit group or a microcomputer, and is preferably composed of a single DSP.

  The timer 42A generates a timing control signal Sa having a predetermined cycle Ta by performing a timer operation based on the control signal from the arithmetic unit 40, and outputs the timing control signal Sa to the booster circuit 24 in the AC / DC converter 2 described later. To do. The timer 42B generates a timing control signal Sb1 and Sb2 having a predetermined cycle Tb by performing a timer operation based on a control signal from the arithmetic unit 40, and an inverter in a DC / DC converter 3 described later. This is output to the circuit 31. These timing control signals Sa, Sb1, and Sb2 are control signals for performing switching driving by pulse width modulation (PWM) to the switching elements in the booster circuit 24 or the inverter circuit 31, respectively.

  Here, in the present embodiment, the cycle Ta of the timing control signal Sa and the cycle Tb of the timing control signals Sb1 and Sb2 are substantially the same. The phases of the timing control signals Sb1 and Sb2 are set so as to advance with respect to the phase of the timing control signal Sa. In other words, the timings of the timing control signals Sb1 and Sb2 are set to be slightly shorter than the timing of the timing control signal Sa.

  Further, the time corresponding to the phase difference between the timing control signal Sa and the timing control signals Sb1 and Sb2 is longer than the delay time (delay time Tdelay described later) required for the sampling operation by the A / D converters 41A and 41B. Is set to

  Furthermore, as shown in FIG. 1, the timing control signal Sb2 also serves as a timing control signal for sampling in the A / D conversion units 41A and 41B. However, the timing control signal Sb1 may also serve as a timing control signal for sampling in the A / D converters 41A and 41B. Details of these timing control signals Sa, Sb1, and Sb2 will be described later (FIG. 3).

  Next, detailed configurations of the AC / DC conversion unit 2 and the DC / DC conversion unit 3 will be described with reference to FIG. FIG. 2 is a circuit diagram showing the detailed configuration of the AC / DC converter 2 and the DC / DC converter 3.

  First, the AC / DC converter 2 includes a rectifier circuit 21, a capacitor C1, an input voltage detection circuit 22, an input current detection circuit 23, a booster circuit 24 including a switching element SW2, and a smoothing circuit including a smoothing capacitor 25C. 25.

The rectifier circuit 21 is a bridge type rectifier circuit having four rectifier diodes 21D1 to 21D4. Specifically, the anode of the diode 21D1 and the cathode of the diode 21D2 are connected to the input terminal T1 via the connection line H1, and the anode of the diode 21D3 and the cathode of the diode 21D4 are connected to the input terminal T2 via the connection line L1. It is connected. The cathode of the diode 21D1 and the cathode of the diode 21D3 are connected to the connection line H2, and the anode of the diode 21D2 and the anode of the diode 21D4 are connected to the connection line L2. With such a configuration, in the rectifier circuit 21, the input AC input voltage Vacin is rectified, and a rectified voltage V1 (input voltage Vin) is generated between the connection lines H2 and L2.

  The capacitor C1 is disposed between the connection lines H2 and L2 between the rectifier circuit 21 and an input voltage detection circuit 22 described later, and functions as a smoothing capacitor. Specifically, it is for smoothing and reducing noise and the like during a switching operation by the switching element SW2 described later.

  The input voltage detection circuit 22 is disposed on the connection lines H2 and L2 between the capacitor C1 and the input current detection circuit 2 described later, and detects the voltage V1 (input voltage Vin) across the capacitor C1. At the same time, a detection signal S (Vin) corresponding to the detected input voltage Vin is output to the A / D conversion unit 41A in the control unit 4. As a specific circuit configuration of the input voltage detection circuit 22, for example, the input voltage Vin is detected by a voltage dividing resistor (not shown) arranged between the connection lines H2 and L2, and a voltage corresponding to this is detected. And the like that generate

  The input current detection circuit 23 is disposed on the connection line H2 between the input voltage detection circuit 22 and a booster circuit 24, which will be described later, and detects the input current Iin flowing into the booster circuit 24 as well as this detection. The detection signal S (Iin) corresponding to the input current Iin is output to the A / D conversion unit 41A in the control unit 4. A specific circuit configuration of the input current detection circuit 23 includes, for example, a circuit including a current transformer.

  The booster circuit 24 includes a switching element SW2, an inductor 24L, and a diode 24D. Specifically, the inductor 24L is inserted and arranged on the connection line H2, one end is connected to the input current detection circuit 23, and the other end is connected to one end (drain) of the switching element SW2. The switching element SW2 is a switching element for generating a pulse voltage V2 by switching the rectified voltage V1 (input current Vin), for example, a field effect transistor (MOS-FET). Or a bipolar transistor, IGBT (Insulated Gate Bipolar Transistor), or the like. Here, the switching element SW2 is composed of an N-channel MOS-FET, the gate is connected to the signal line of the timing control signal Sa supplied from the timer 42A in the control unit 4, and the source is connected to the connection line L2. The drain is connected to the connection line H2. The anode of the diode 24D is connected to the other end of the inductor 24L and the drain of the switching element SW2, and the cathode of the diode 24D is connected to one end of a smoothing capacitor 25C described later. With this configuration, the booster circuit 24 generates a pulse voltage V2 boosted based on the rectified voltage V1, as will be described in detail later.

  The smoothing circuit 25 includes a smoothing capacitor 25C configured using, for example, a film capacitor. Specifically, one end of the smoothing capacitor 25C is connected to the cathode of the diode 24D, and the other end of the smoothing capacitor 25C is connected to the connection line L2. With such a configuration, in the smoothing circuit 25, the DC voltage Vdc1 to be supplied to the DC / DC converter 3 is generated by smoothing the pulse voltage V2. Further, the smoothing capacitor 25C also plays a role of smoothing and reducing noise and the like during switching operation by switching elements SW31 to SW34 in the DC / DC conversion unit 3 described later.

  Next, the DC / DC conversion unit 3 includes an inverter circuit 31, a transformer 32, a rectifier circuit 33, a smoothing circuit 34, and an output voltage detection circuit 35.

  The inverter circuit 31 is a full bridge type inverter circuit having four switching elements SW31 to SW34. Each of these switching elements SW31 to SW34 is configured by, for example, a MOS-FET, a bipolar transistor, an IGBT, or the like. Here, the switching elements SW31 to SW34 are each configured by an N-channel MOS-FET. Here, the gate of the switching element SW31 is connected to the signal line of the timing control signal Sb2 supplied from the timer 42B in the control unit 4, the source is connected to the drain of the switching element SW32, and the drain is connected to the connection line H2. ing. The gate of the switching element SW32 is connected to the signal line of the timing control signal Sb1 supplied from the timer 42B in the control unit 4, the source is connected to the connection line L2, and the drain is connected to the source of the switching element SW31. Yes. The gate of the switching element SW33 is connected to the signal line of the timing control signal Sb1 supplied from the timer 42B in the control unit 4, the source is connected to the drain of the switching element SW34, and the drain is connected to the connection line H2. Yes. The gate of the switching element SW34 is connected to the signal line of the timing control signal Sb2 supplied from the timer 42B in the control unit 4, the source is connected to the connection line L2, and the drain is connected to the source of the switching element SW33. Yes. The source of the switching element SW31 and the drain of the switching element SW32 are connected to one end of a winding 321 (primary side winding) in the transformer 32 described later. The source of the switching element SW33 and the drain of the switching element SW34 are The other end of the winding 321 is connected. With this configuration, the inverter circuit 31 generates an AC voltage (input AC voltage) between both ends of the winding 321 based on the DC voltage Vdc1, as will be described in detail later.

  The transformer 32 has a winding 321 (primary winding) and a winding 322 (secondary winding). One end of the winding 322 is connected to the connection line H3, and the other end is connected to the connection line L3. The transformer 32 transforms the input AC voltage generated by the inverter circuit 31 and generates an output AC voltage at both ends of the winding 322. In this case, the degree of transformation is determined by the turn ratio between the winding 321 and the winding 322.

  The rectifier circuit 33 is a bridge type rectifier circuit having four rectifier diodes 33D1 to 33D4. Specifically, the anode of the diode 33D1 and the cathode of the diode 33D2 are connected to one end of the winding 322 via the connection line H3, and the anode of the diode 33D3 and the cathode of the diode 33D4 are connected to each other via the connection line L3. It is connected to the other end of 322. The cathode of the diode 33D1 and the cathode of the diode 33D3 are connected to the connection line H4, and the anode of the diode 33D2 and the anode of the diode 33D4 are connected to the connection line L4. With such a configuration, in the rectifier circuit 33, the AC output voltage input from both ends of the winding 322 is rectified, and a rectified voltage (DC voltage Vdc2) is generated between the connection lines H4 and L4. .

  The smoothing circuit 34 has a smoothing capacitor 34C configured using, for example, a film capacitor. Specifically, one end of the smoothing capacitor 34C is connected to the cathodes of the diodes 33D1 and 33D3 via the connection line H4, and the other end of the smoothing capacitor 34C is connected to the anodes of the diodes 33D2 and 33D4 via the connection line L4. Has been. With such a configuration, the smoothing circuit 34 smoothes the DC voltage Vdc2, thereby generating a DC output voltage Vdcout (output voltage Vout) to be supplied to the battery 50.

  The output voltage detection circuit 35 is disposed between the smoothing circuit 34 and the output terminals T3 and T4 on the connection lines H4 and L4, and the output voltage Vout supplied to the battery 50 via the output terminals T3 and T4. , And a detection signal S (Vout) corresponding to the detected output voltage Vout is output to the A / D conversion unit 41B in the control unit 4. Note that the specific circuit configuration of the output voltage detection circuit 35 is similar to that of the input voltage detection circuit 22, for example, the output voltage Vout by a voltage dividing resistor (not shown) arranged between the connection lines H4 and L4. And generating a voltage corresponding to this.

  Here, the switching element SW2 corresponds to a specific example of “first switching element” in the present invention, and the switching elements SW31 to SW34 correspond to a specific example of “second switching element” in the present invention. The A / D conversion unit 41A corresponds to a specific example of “sampling means” in the present invention, and the arithmetic unit 40 and timers 42A and 42B correspond to a specific example of “control unit” in the present invention. The DC voltage Vdc1 corresponds to a specific example of “DC input voltage” in the present invention. Further, the timing control signal Sa corresponds to a specific example of “first timing control signal” in the present invention, and the timing control signals Sb1 and Sb2 correspond to a specific example of “second timing control signal” in the present invention. To do.

  Next, the operation and effect of the AC / DC converter 1 of the present embodiment will be described.

  First, the basic operation (charging operation to the battery 50) of the AC / DC converter 1 will be described with reference to FIGS. FIG. 3 is a timing waveform diagram showing the overall operation of the AC / DC converter 1. (A) to (C) are timing controls Sa, Sb1 and Sb2, and (D) and (E) are detection signals. S (Iin) and D (Iin) are respectively represented.

  In the AC / DC converter 1, when an AC input voltage Vacin (commercial voltage) formed of a sine wave is supplied to the AC / DC converter 2 from between the input terminals T <b> 1 and T <b> 2, the AC / DC converter 1 is rectified by the rectifier circuit 21. A rectified voltage V1 (input voltage Vin) consisting of a positive half-wave is generated.

  Next, the booster circuit 24 generates a boosted pulse voltage V2 by performing a boosting operation as shown in FIGS. 4A and 4B, for example, based on the rectified voltage V1. Specifically, the pulse voltage V2 is generated by switching the rectified voltage V1 by the switching element SW2.

More specifically, first, when the switching element SW2 is turned on in accordance with the timing control signal Sa (“Tr: ON” period shown in FIG. 3; on period Ton), for example, FIG. As shown in (A), a current I11 flows from the inductor 24L to the switching element SW2, thereby accumulating magnetic energy in the inductor 24L. When the switching element SW2 is turned off in accordance with the timing control signal Sa (“Tr: OFF” period shown in FIG. 3; off period Toff), for example, as shown in FIG. 4B. In addition, a current I12 flows from the inductor 24L to the diode 24D and the capacitor 25C in this order, whereby the magnetic energy stored in the inductor 24L is stored in the capacitor 25C and a boosting operation is performed. The relationship between the rectified voltage V1 and the pulse voltage V2 during such a boosting operation is expressed as shown in the following equation (1).
V2 = {(Ton + Toff) / Toff} × V1 (1)

  Next, in the smoothing circuit 25, the input pulse voltage V2 is smoothed, and a DC voltage Vdc1 to be supplied to the DC / DC converter 3 is generated.

Next, the DC / DC converter 3 generates a stepped-down DC output voltage Vdcout by performing a DC voltage conversion operation (step-down operation) based on the input DC voltage Vdc1. Specifically, first, in the inverter circuit 31, the DC voltage Vdc 1 is switched to generate an input AC voltage, and this input AC voltage is supplied to the winding 321 of the transformer 32. Next, the transformer 32 transforms the input AC voltage, and the winding 322 outputs a transformed (step-down) output AC voltage. Next, in the rectifier circuit 33, the output AC voltage output from the transformer 32 is rectified by the diodes 33D1 to 33D4 to generate a rectified voltage (DC voltage Vdc2). Next, in the smoothing circuit 34, the input rectified voltage is smoothed and output as a DC output voltage Vdcout from the output terminals T3 and T4. The battery 50 is charged by the DC output voltage Vdcout (output voltage Vout) and the output current Iout shown in FIG.

  At this time, in the DC / DC converter 3, for example, as shown in FIGS. 5A and 5B, in the inverter circuit 31, the switching elements SW31 and SW34 are turned on according to the timing control signal Sb2. (See FIGS. 3C and 5A) and a period during which the switching elements SW32 and SW33 are turned on in accordance with the timing control signal Sb1 (see FIGS. 3B and 5B). Are repeated alternately. Specifically, first, as shown in FIG. 5A, when the switching elements SW31 and SW34 are turned on, the primary loop current I21a flows in the direction from the switching element SW31 to the switching element SW34. In addition, a secondary loop current I22a flows through the winding 322, the diode 33D1, the smoothing capacitor 34C, and the diode 33D4 in this order. On the other hand, as shown in FIG. 5B, when the switching elements SW32 and SW33 are turned on, the primary loop current I21b flows in the direction from the switching element SW33 to the switching element SW32. Further, a secondary loop current I22b flows through the winding 322, the diode 33D3, the smoothing capacitor 34C, and the diode 33D2 in this order.

  Next, a control operation (generation operation of timing control signals Sa, Sb1, Sb2) by the control unit 4, which is one of the characteristic parts of the present invention, will be described in detail with reference to FIGS. .

  First, in the charging operation, the input voltage Vin is detected by the input voltage detection circuit 22, the input current Iin is detected by the input current detection circuit 23, and the output voltage Vout is detected by the output voltage detection circuit 35. Then, the detection signal S (Vin) from the input voltage detection circuit 22, the detection signal S (Iin) from the input current detection circuit 23, and the detection signal S (Vout) from the output voltage detection circuit 35 are supplied to the control unit 4, respectively. Is done.

  Next, the A / D conversion unit 41A in the control unit 4 performs A / D conversion on the detection signal S (Vin) and the detection signal S (Iin), respectively, so that the digital detection signal D (Vin ), A detection signal D (Iin) is generated and supplied to the arithmetic unit 40. On the other hand, the A / D conversion unit 41B performs A / D conversion on the detection signal S (Vout), thereby generating a digital detection signal D (Vout) and supplying the digital detection signal D (Vout) to the arithmetic unit 40.

Next, in the arithmetic unit 40 and the timers 42A and 42B, based on the detection signal D (Vin), the detection signal D (Iin), and the detection signal D (Vout), a timing control signal Sa having a predetermined period Ta, Timing control signals Sb1 and Sb2 having a predetermined period Tb are generated. The timing control signal Sa is supplied to the switching element SW2 in the booster circuit 24, and switching driving by PWM is performed. Further, the timing control signals Sb1 and Sb2 are supplied to the switching elements SW31 to SW34 in the inverter circuit 31, and switching driving by PWM is performed. In this way, the switching of the switching element SW2 in the AC / DC conversion unit 2 is performed using the detection signal S (Vin) and the timing control signal Sa based on the detection signal S (Iin) sampled in the AC / DC conversion unit 41A. By controlling the drive, the AC / DC converter 2 can perform highly accurate PFC operation.

  At this time, in the present embodiment, for example, as shown in FIG. 3, the cycle Ta of the timing control signal Sa and the cycle Tb of the timing control signals Sb1 and Sb2 are substantially the same, and the timing control signal The phases of the signals Sb1 and Sb2 are set so as to advance with respect to the phase of the timing control signal Sa. Specifically, timing tb (t1, t3, t5, t7, etc.) at which the timing control signals Sb1, Sb2 are switched on / off is timing ta (t2, t4, t6) at which the timing control signal Sa is switched on / off. , T8, etc.) is set so as to be a minute time earlier.

  Thereby, based on such timing control signals Sb1 and Sb2, before the switching operation of the switching element SW2 (operation at timings t2, t4, t6, t8, etc.) (for example, sampling timing ts in the figure). The detection signals S (Iin) and S (Vin) can be sampled in the A / D converters 41A and 41B. Therefore, switching noise (for example, noise indicated by the arrow P1 in the figure) due to the switching element SW2 is reduced during sampling in the A / D conversion unit 41A.

  The timing control signal Sb2 also serves as a timing control signal for sampling the detection signals S (Iin) and S (Vin) in the A / D converters 41A and 41B. Thereby, it is not necessary to provide a timer separate from the timers 41A and 41B for the timing control signal when sampling, and the configuration of the entire AC / DC converter 1 is simplified.

  Further, the time corresponding to the phase difference between the timing control signal Sa and the timing control signals Sb1 and Sb2 (for example, the time between timings t1 and t2) is the delay time Tdelay required for the sampling operation by the A / D converters 41A and 41B. (See FIG. 3). In other words, the delay time Tdelay from the start of sampling by the timing control signal Sb2 (for example, timing t1) to the actual sampling (for example, sampling timing ts) is the timing control signal Sa and the timing control signals Sb1 and Sb2. It is shorter than the time corresponding to the phase difference. Thereby, it is possible to sample the detection signals S (Iin) and S (Vin) immediately before the timing (for example, timing t2) when the switching element SW2 in the AC / DC conversion unit 2 switches from on to off. . In addition, since the sampling operation is reliably performed before the switching operation of the switching element SW2, switching noise during sampling can be completely avoided. The reason why the sampling is preferably performed immediately before the timing when the switching element SW2 switches from on to off in this manner is as follows. That is, as indicated by the arrow P2 in the figure, the input current In flowing through the AC / DC converter 2 is maximized at this time, so that the value of the input current Iin is rated by managing this current value. This is because it becomes easy to fit within the value. It is possible to set the sampling timing when the switching noise immediately after the switching timing has converged, but it is necessary to wait until the switching noise converges and the time for the noise to converge is a circuit. It can be said that it is desirable to set it immediately before the switching timing due to variations due to the characteristics of the network and mounted components.

As described above, in the present embodiment, the detection signal S (Vin) sampled in the AC / DC conversion unit 41A and the timing control signal Sa based on the detection signal S (Iin) are used. Since the switching drive of the switching element SW2 is controlled, the AC / DC converter 2 can perform a highly accurate PFC operation. Further, the cycle Ta of the timing control signal Sa and the cycle Tb of the timing control signals Sb1 and Sb2 are substantially the same, and the phases of the timing control signals Sb1 and Sb2 advance with respect to the phase of the timing control signal Sa. Therefore, switching noise due to the switching element SW2 can be reduced during sampling in the A / D converter 41A. Therefore, it is possible to perform an operation (charging operation) with high accuracy and high power factor in an AC / DC converter having a two-stage configuration.

  Also, since the time corresponding to the phase difference between the timing control signal Sa and the timing control signals Sb1 and Sb2 is made longer than the delay time Tdelay required for the sampling operation by the A / D converters 41A and 41B, A / In the D converter 41A, the sampling operation of the detection signal S (Iin) is reliably performed before the switching operation of the switching element SW2. Therefore, switching noise at the time of sampling can be completely avoided, and charging operation with high accuracy and high power factor can be performed.

  Since the timing control signal Sb2 also serves as a timing control signal for sampling the detection signals S (Iin) and S (Vin) in the A / D converters 41A and 41B, the timing for sampling is used. There is no need to provide a timer separate from the timers 41A and 41B for the control signal. Therefore, the configuration of the entire AC / DC converter 1 can be simplified. Thereby, an inexpensive DSP can be used as the arithmetic unit 40, and the AC / DC converter 1 can be manufactured at a low cost.

  In the present embodiment, the case where the cycle Ta of the timing control signal Sa and the cycle Tb of the timing control signals Sb1 and Sb2 are substantially the same has been described. However, the present invention is not limited to such a case. . Specifically, for example, one of the periods Ta and Tb may be an integral multiple of the other within a range in which the phase is not affected by the switching noise. However, it is preferable that the period Ta is longer than the period Tb. On the contrary, compared with the case where the period Ta is set to be shorter than the period Tb, the operation of the AC / DC conversion unit 2 and the DC / DC conversion unit 3 can be easily performed, and the entire AC / DC converter 1 can be operated. This is because the efficiency is improved. That is, for example, as shown in FIGS. 6A to 6C, the period Ta is an integral multiple of the period Tb (here, Ta = 3 × Tb). Can be said to be preferable.

  While the present invention has been described with reference to the embodiment, the present invention is not limited to this embodiment, and various modifications can be made.

  For example, the configurations of the AC / DC conversion unit, the DC / DC conversion unit, the rectifier circuit, the booster circuit, the smoothing circuit, the inverter circuit, and the control unit described in the above embodiment are not limited to these, and may be other configurations. May be.

Specifically, for example, a zero cross point detection circuit 26 for detecting a zero cross point in the input voltage Vin may be provided instead of the input voltage detection circuit 22 as in the AC / DC conversion unit 2A shown in FIG. Good. Specifically, the zero cross point detection circuit 26 includes a transformer 261, four diodes 26D1 to 26D4, a resistor 26R, a constant voltage source 262, and a comparator 263. Here, one winding 261A of the transformer 261 is connected between the connection lines H1 and L1, and the other winding 261B includes the cathode of the diode 26D1 and the anode of the diode 26D3, the cathode of the diode 26D2 and the diode 26D4. Connected between the anodes. The anodes of the diodes 26D1 and 26D2 are grounded to each other, and the cathodes of the diodes 26D3 and 26D4 are connected to one end of the resistor 26R and the negative input terminal of the comparator 263. The other end of the resistor 26R is grounded, and the positive input terminal of the comparator 263 is connected to a constant voltage source 262 that is a power source of the constant voltage Vc. Also, a zero cross point detection signal S (zp) is output from the output terminal of the comparator 263 and supplied to the control unit 4. In the AC / DC converter including the AC / DC conversion unit 2A having such a configuration, the zero cross point (specifically, the detection signal S (zp)) detected by the zero cross point detection circuit 26 in the control unit 4 is detected. A sine wave having a period such as twice the period is generated using a calculation or a look-up table (LUT), and the timing control signals Sa, Sb1, and Sb2 are generated using such a sine wave. As a result, even when the input current Iin is distorted from a sine waveform due to noise or the like, the harmonic current can be reliably reduced regardless of the waveform of the input voltage Vin.

  In the AC / DC converter 2 of the above embodiment, the case where the rectifier circuit and the booster circuit are provided separately and the switching element is provided in the booster circuit has been described. For example, the AC / DC converter 2 shown in FIG. Like the DC converter 2B, the synchronous rectifier circuit 27 is used as a rectifier circuit, and the synchronous rectifier circuit 27 is used as a part of the booster circuit, and the switching elements SW21 to SW24 in the synchronous rectifier circuit 27 are used as switching elements of the booster circuit. You may make it also serve. Specifically, the synchronous rectifier circuit 27 includes two inductors 24L1 and 24L2, four switching elements SW21 to SW24, and a diode 24D. The inductor 24L1 is inserted on the connection line H1, and the inductor 24L2 is inserted on the connection line L1. The gate of the switching element SW21 is connected to the signal line of the timing control signal Sa2 supplied from the timer 42A in the control unit 4, the source is connected to the connection line H1, and the drain is connected to the connection line H2. . The gate of the switching element SW22 is connected to the signal line of the timing control signal Sa1 supplied from the timer 42A in the control unit 4, the source is connected to the connection line L2, and the drain is connected to the connection line H1. . The gate of the switching element SW23 is connected to the signal line of the timing control signal Sa1 supplied from the timer 42A in the control unit 4, the source is connected to the connection line L1, and the drain is connected to the connection line H2. . The gate of the switching element SW24 is connected to the signal line of the timing control signal Sa2 supplied from the timer 42A in the control unit 4, the source is connected to the connection line L2, and the drain is connected to the connection line L1. . The anode of the diode 24D is connected to the drains of the switching elements SW21 and SW23, and the cathode of the diode 24D is connected to one end of the smoothing capacitor 25C. With this configuration, in the synchronous rectifier circuit 27, when the input voltage Vin is positive, the switching elements SW21 and SW24 are turned on, the switching element SW23 is turned off, and the switching element SW22 is turned on / off (the time ratio is controlled). State). On the other hand, when the input voltage Vin is negative, the switching elements SW22 and SW23 are turned on, the switching element SW21 is turned off, and the switching element SW24 is turned on / off (a state in which the time ratio is controlled).

Further, for example, an AC / DC converter 2B shown in FIG. 8 is provided instead of the AC / DC converter 2 as in the AC / DC converter 1C shown in FIGS. 9 to 12, and the DC / DC converter 3 Instead of this, a DC / DC converter 3C may be provided. Specifically, in the AC / DC converter 2B, the switching elements SW21 to SW24 are each composed of a MOS-FET. In the DC / DC conversion unit 3C, the switching elements SW31 to SW34 are each configured by a MOS-FET, and switching elements SW41 to SW44 configured by MOS-FET are provided instead of the rectifier diodes 33D1 to 33D3. It has been. In this case, each of the switching elements SW21 to SW24, SW31 to SW34, and SW41 to SW44 can be regarded as including a switching element and a rectifier diode (parasitic diode of the switching element) connected in parallel to them. When configured in this manner, the DC output voltage Vdcout is generated based on the AC input voltage Vacin input from the input terminals T1 and T2 as described in the above embodiment, and is output from the output terminals T3 and T4. In addition to the forward operation (see the current path of the arrow shown in FIGS. 9 and 10), the AC output voltage Vacout is generated based on the DC input voltage Vdcin input from the output terminals T3 and T4, and the input terminal T1. , T2 can also be performed in the reverse direction (see the current path indicated by the arrows shown in FIGS. 11 and 12) (bidirectional operation is possible). In that case, during reverse operation, the rectifier circuit 33 functions as an inverter circuit, and the inverter circuit 31 functions as a rectifier circuit.

  In this case, the input terminals T1 and T2 correspond to a specific example of “first input / output terminal” in the present invention, and the output terminals T3 and T4 correspond to one specific example of “second input / output terminal” in the present invention. Corresponds to the example. Further, the switching elements SW21 to SW24 correspond to a specific example of “first switching element” in the present invention, and the switching elements SW31 to SW34 and SW41 to SW44 correspond to a specific example of “second switching element” in the present invention. Corresponding to

  In addition, the case where the entire AC / DC converter is used as a charging device for a battery or the like has been described so far, but the AC / DC converter of the present invention is not limited to such a charging device. It can be applied to other uses.

  In the above embodiment, the function of the arithmetic unit 40 in the control unit 4 is configured by software. However, the function of the arithmetic unit 40 may be configured by hardware. However, when configured by hardware, the circuit scale increases, and it is difficult to correct variations in each element. Therefore, it is preferable to configure by software as in the above embodiment.

It is a block diagram showing the structure of the AC / DC converter which concerns on one embodiment of this invention. FIG. 2 is a circuit diagram illustrating a detailed configuration of an AC / DC conversion unit and a DC / DC conversion unit illustrated in FIG. 1. It is a timing waveform diagram for demonstrating the operation | movement of the whole AC / DC converter. FIG. 3 is a circuit diagram for explaining the operation of a booster circuit in the AC / DC converter shown in FIG. 2. FIG. 3 is a circuit diagram for explaining the operation of the DC / DC converter shown in FIG. 2. It is a timing waveform diagram for demonstrating the operation | movement of the whole AC / DC converter which concerns on the modification of this invention. It is a circuit diagram showing the structure of the AC / DC conversion part which concerns on the other modification of this invention. It is a circuit diagram showing the structure of the AC / DC conversion part which concerns on the other modification of this invention. It is a circuit diagram for demonstrating the forward direction operation | movement of the whole AC / DC converter which concerns on the other modification of this invention. It is a circuit diagram for demonstrating the forward direction operation | movement of the whole AC / DC converter which concerns on the other modification of this invention. It is a circuit diagram for demonstrating the reverse direction operation | movement of the whole AC / DC converter which concerns on the other modification of this invention. It is a circuit diagram for demonstrating the reverse direction operation | movement of the whole AC / DC converter which concerns on the other modification of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,1C ... AC / DC converter, 10 ... Commercial power supply, 2, 2A, 2B ... AC / DC conversion part, 21 ... Rectifier circuit, 21D1-21D4 ... Diode, 22 ... Input voltage detection circuit, 23 ... Input current detection circuit 24 ... booster circuit, 24L, 24L1, 24L2 ... inductor, 24D ... diode, 25 ... smoothing circuit, 25C ... smoothing capacitor, 26 ... zero cross point detection circuit, 261 ... transformer, 261A, 261B ... winding, 262 ... constant voltage Power source, 263, comparator, 26D1 to 26D4, diode, 26R, resistor, 27, synchronous rectifier circuit, 3
, 3C ... DC / DC converter, 31 ... inverter circuit, 32 ... transformer, 321, 322 ... winding, 33 ... rectifier circuit, 33D1-33D4 ... diode, 34 ... smoothing circuit, 34C ... smoothing capacitor, 35 ... output voltage Detection circuit, 4 ... control unit, 40 ... arithmetic unit, 41A, 41B ... A / D conversion unit, 42A, 42B ... timer, 50 ... battery, 60 ... load, T1, T2 ... input terminal, T3, T4 ... output terminal , H1, L1, H2, L2, H3, L3, H4, L4 ... connection line, Vacin ... AC input voltage, V1 (Vin) ... rectified voltage (input voltage), V2 ... pulse voltage, V3 ... voltage, Vdc1, Vdc2 ... DC voltage, Vc ... constant voltage, Vdcout (Vout) ... DC output voltage (output voltage), Iin ... input current, Iout ... output current, I11, I12, I21a, I21b, I22a, I22b ... Current, S (Vin), S (Iin), S (Vout), S (zp), D (Vin), D (Iin), D (Vout) ... Detection signal, Sa, Sa1, Sa2, Sb1, Sb2 ... timing control signal, C1 ... capacitor, SW2, SW21 to SW24, SW31 to SW34, SW41 to SW44 ... transistor (switching element), Ta, Tb ... period of timing control signal, t1 to t8, ta, tb ... timing.

Claims (9)

An AC / DC converter configured to include a first switching element and generate a DC input voltage based on the AC input voltage;
A DC / DC converter configured to include a second switching element and generate a DC output voltage by performing voltage conversion based on the DC input voltage;
Sampling means for periodically sampling the input current flowing into the AC / DC converter at a predetermined timing;
First and second timing control signals are generated based on at least the input current sampled by the sampling means, and the first switching element is switched by pulse width modulation using the first timing control signal. A controller that performs driving and performs switching driving by pulse width modulation on the second switching element using the second timing control signal, and
The period of the first timing control signal and the period of the second timing control signal are substantially the same as each other, or one is an integral multiple of the other,
An AC / DC converter, wherein the phase of the second timing control signal is set to advance with respect to the phase of the first timing control signal. The AC / DC converter according to claim 1, wherein the second timing control signal also serves as a timing control signal for sampling the input current. The sampling means further samples the AC input voltage periodically at a predetermined timing,
The AC / DC converter according to claim 2, wherein the second timing control signal further serves as a timing control signal for sampling the AC input voltage. The time corresponding to the phase difference between the first timing control signal and the second timing control signal is set to be longer than the delay time required for the sampling operation by the sampling means. The AC / DC converter according to any one of claims 1 to 3. The cycle of the first timing control signal is set so as to be longer than the cycle of the second timing control signal. 5. AC / DC converter. The AC / DC converter according to claim 5, wherein a cycle of the first timing control signal is an integral multiple of a cycle of the second timing control signal. The AC / DC conversion unit is configured to include a booster circuit having a power factor improvement function using the first switching element,
The AC / DC converter according to any one of claims 1 to 6, wherein the DC / DC converter is configured to perform a step-down operation. The sampling means performs sampling using A / D conversion,
The AC / DC converter according to any one of claims 1 to 7, wherein the control unit is configured using a single digital arithmetic device (DSP). An AC / DC converter that outputs an output voltage from the other input / output terminal pair based on an input voltage input from one input / output terminal pair of the first and second input / output terminal pairs,
An AC / DC converter disposed on the first input / output terminal side and configured to include a first switching element;
A DC / DC converter disposed on the second input / output terminal side and configured to include a second switching element;
Sampling means for periodically sampling the inflow current flowing into the AC / DC converter at a predetermined timing;
First and second timing control signals are generated based on at least the inflow current sampled by the sampling means, and the first switching element is switched by pulse width modulation using the first timing control signal. A controller that performs driving and performs switching driving by pulse width modulation on the second switching element using the second timing control signal, and
The period of the first timing control signal and the period of the second timing control signal are substantially the same as each other, or one is an integral multiple of the other,
An AC / DC converter, wherein the phase of the second timing control signal is set to advance with respect to the phase of the first timing control signal.

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