JP6659196B2 - Power converter - Google Patents

Description

  The present invention relates to a power converter for performing DC / DC power conversion.

  2. Description of the Related Art Zero-cross switching control (hereinafter, referred to as ZCS control) is known as a highly efficient control method for a power conversion device that includes a switching element and a reactor and converts an input DC voltage into a DC voltage having an arbitrary magnitude. The ZCS control is a control in which the timing when the current flowing in the switching element or the current flowing in the reactor becomes zero is detected as a zero current signal, and the switching element is switched at the timing when the zero current signal is detected. The ZCS control has a problem that the switching frequency increases at a light load, and the switching loss increases.

  Thus, a method for preventing a switching frequency from becoming higher and reducing a switching loss is disclosed. For example, Patent Literature 1 discloses a method in which a delay time is inserted between detection of a zero current signal and switching of a switching element. Further, for example, Patent Document 2 discloses a method of counting the number of detected zero current signals and switching the switching element at a timing when the count number of the zero current signal reaches a certain number.

Japanese Patent No. 5828106 JP 2014-131455 A

  Patent Document 1 and Patent Document 2 do not discuss the case where an AC voltage component is superimposed on an input DC voltage which is an input voltage of a power converter. Therefore, when the AC voltage component is superimposed on the input DC voltage, there is a problem that a large ripple occurs in the output voltage.

  The present invention has been made in order to solve the above-described problems, and provides a power conversion device capable of reducing a ripple of an output voltage even when an AC voltage component is superimposed on an input DC voltage. Aim.

A power converter according to the present invention includes a switching element and a reactor, and a power supply main circuit unit that converts an input voltage in which an AC voltage component is superimposed on a DC voltage component into power and outputs the input voltage to a load.
When the detected value of the input voltage is larger due to the AC voltage component superimposed on the DC voltage component, the ON state of the switching element is smaller than when the detected value of the input voltage is smaller due to the AC voltage component superimposed on the DC voltage component. The power supply control unit determines an ON timing of the switching element so as to delay the timing.

  ADVANTAGE OF THE INVENTION According to the power converter of this invention, the ripple of an output voltage can be reduced also when an AC voltage component is superimposed on an input DC voltage.

FIG. 1 is a circuit block diagram illustrating a power conversion device according to a first embodiment of the present invention. FIG. 2 is a circuit block diagram illustrating a configuration example of an input power supply according to the first embodiment of the present invention. FIG. 4 is a diagram for explaining an operation of the power supply main circuit unit according to the first embodiment of the present invention. FIG. 4 is a diagram for explaining an operation of the power supply main circuit unit according to the first embodiment of the present invention. FIG. 4 is a diagram for explaining an operation of the power supply main circuit unit according to the first embodiment of the present invention. 4 is a flowchart illustrating a control operation of a power supply control unit according to the first embodiment of the present invention. FIG. 4 is a diagram illustrating a comparison between an input voltage detection value and a comparison threshold value according to the first embodiment of the present invention. FIG. 5 is a diagram illustrating a simulation result when variable count ZCS control is applied according to the first embodiment of the present invention. FIG. 7 is a diagram illustrating a simulation result when the variable count ZCS control is not applied according to the first embodiment of the present invention. FIG. 7 is a diagram illustrating another comparative example of the input voltage detection value and the comparison threshold value according to the first embodiment of the present invention. FIG. 3 is a circuit block diagram showing another example of the power converter according to Embodiment 1 of the present invention. FIG. 5 is a diagram illustrating a simulation result when variable count ZCS control is applied according to the first embodiment of the present invention. FIG. 7 is a diagram illustrating a simulation result when the variable count ZCS control is not applied according to the first embodiment of the present invention. FIG. 3 is a circuit block diagram showing another example of the power converter according to Embodiment 1 of the present invention. FIG. 3 is a circuit block diagram showing another example of the power converter according to Embodiment 1 of the present invention. FIG. 16 is a diagram illustrating an operation of a power supply main circuit unit of the power conversion device in FIG. 15. FIG. 3 is a circuit block diagram showing another example of the power converter according to Embodiment 1 of the present invention. FIG. 7 is a circuit block diagram showing a power converter according to Embodiment 2 of the present invention.

Embodiment 1 FIG.
FIG. 1 is a circuit block diagram showing a power converter 1 according to Embodiment 1 of the present invention. The power conversion device 1 according to the first embodiment includes a power supply main circuit unit 2 and a power supply control unit 3. The power supply main circuit section 2 includes a converter 6 having a switching element 11, a diode 13, and a reactor 12, and a capacitor Co for smoothing an output voltage of the converter 6. In the power supply main circuit section 2, the input power supply 4 is connected to the input side of the converter 6, and the load 5 is connected to the output side of the capacitor Co.

The input power supply 4 is a device that outputs a voltage Vin including an AC voltage component and a DC voltage component (hereinafter, referred to as an input voltage Vin or a pulsating voltage Vin). The input power supply 4 only needs to output a pulsating voltage Vin. As shown in FIG. 2, the AC voltage Vac output from the AC power supply 41 is full-wave rectified by a diode bridge circuit 42, and then PFC (Power Factor Correction). The power conversion may be performed by the circuit 43. In FIG. 2, C1 and C2 indicate capacitors.
Further, the input power supply 4 may be configured to output a voltage obtained by full-wave rectifying the AC voltage Vac by the diode bridge circuit 42 without using the PFC circuit 43.
Further, an AC / DC converter (not shown) that directly converts the AC voltage Vac to a DC voltage without using the diode bridge circuit 42 may be used as the input power supply 4.
In the first embodiment, as shown in FIG. 1, the input power supply 4 for generating the pulsating voltage Vin is shown as a circuit diagram in which an AC power supply 4A and a DC power supply 4B are connected in series.

  The converter 6 is a power converter that receives an input voltage (pulsation voltage) Vin and performs DC / DC power conversion to a target output voltage Vo, and includes, for example, a step-down chopper circuit including a switching element 11, a reactor 12, and a diode 13. Be composed. The converter 6 may be any circuit having a switching element and a reactor and performing DC / DC power conversion. For example, a step-up chopper circuit, a step-up / step-down chopper circuit, an H-bridge type step-up / step-down circuit, a SEPIC (Single Ended Primary Inductor) (Converter) converter, flyback converter, or Cuk converter. The switching element 11 is a field effect transistor (FET) element and an IGBT (Insulated Gate Bipolar Transistor) element driven by a switching element drive signal Ga (hereinafter, referred to as a gate signal Ga) generated by the power supply control unit 3 described later. And so on. Further, the diode 13 may be changed to a switching element Q1 (not shown) such as an FET element or an IGBT element, and a synchronous rectification method in which the switching element 11 and the switching element Q1 are turned on and off by reverse logic may be used.

  The power supply main circuit section 2 includes an input voltage detection section 7, an output voltage detection section 8, and a zero current detection section 9. The input voltage detector 7 detects the magnitude of the input voltage (pulsating voltage) Vin as an input voltage detection value Vinsen. For example, as shown in FIG. 1, two or more voltage-dividing resistors connected in series are provided. Is provided. The output voltage detector 8 detects the magnitude of the DC output voltage vo as an output voltage detection value Vosen. For example, as shown in FIG. 1, two or more series-connected voltage-dividing resistors Is provided. The zero current detection unit 9 is for detecting a zero point of the current flowing through the reactor 12, and for example, as shown in FIG. The voltage VLsen obtained from the auxiliary winding of the zero current detection unit 9 is output to a zero current signal generation unit 31 of the power supply control unit 3 described later, and the zero current signal generation unit 31 detects a zero point of the current of the reactor 12 and Outputs current signal ZCD.

  Note that the zero current detection unit 9 may not be a method using the auxiliary winding as long as it can detect a zero point of the current flowing through the reactor 12. For example, a current detection resistor may be installed on the low side of the reactor 12, A method of detecting the zero point of the current of the reactor 12 from the voltage generated at both ends of the current detection resistor may be used.

  Next, the power control unit 3 will be described. The power supply controller 3 includes a zero current signal generator 31, an on-time generator 32, an on-timing generator 33, and a switching driver 34. The zero current signal generation unit 31 outputs the zero current signal ZCD indicating the timing at which the current flowing through the reactor 12 becomes zero based on the voltage VLsen obtained from the zero current detection unit 9 as described above. The on-time generator 32 derives a time for maintaining the gate signal Ga at High (hereinafter, referred to as “H”), that is, an on-time of the switching element 11, based on the output voltage detection value Vosen and the target voltage value Voref. . The on-timing generation unit 33 performs variable count ZCS control based on the zero current signal ZCD, the input voltage detection value Vinsen, and the output voltage detection value Vosen, and sets the gate signal Ga to “H”, that is, turns on the switching element 11. Determine the timing. The variable count ZCS control is control that determines the timing at which the gate signal Ga is set to “H” based on the AC voltage component superimposed on the input voltage (pulsation voltage) Vin. The variable count ZCS control will be described later in detail. The switching driver 34 receives the ON time from the ON time generator 32 and the ON timing from the ON timing generator 33, and generates a gate signal Ga for operating the switching element 11.

Next, the circuit operation of the power supply main circuit unit 2, particularly the circuit operation of ZCS control, will be described with reference to FIG. FIG. 3 shows the relationship between the gate signal Ga output from the switching drive unit 34, the reactor current iL flowing in the reactor 12, and the zero current signal ZCD output from the zero current signal generation unit 31, with the horizontal axis representing time.
When the gate signal Ga becomes “H” and the switching element 11 is turned on, in FIG. 1, a current flows in the order of the input power supply 4, the switching element 11, the reactor 12, the load 5, and the input power supply 4, and the reactor current iL increases. During the period in which reactor current iL increases, zero current signal ZCD is at "H".

  When the gate signal Ga becomes Low (hereinafter referred to as “L”) and the switching element 11 is turned off, a current flows in the order of the reactor 12, the load 5, the diode 13, and the reactor 12, and the reactor current iL decreases to zero. While the reactor current iL decreases to zero, the zero current signal ZCD becomes "L".

  Here, the period in which the reactor current iL increases and the period in which the reactor current iL decreases to zero become shorter as the power supplied to the load 5 becomes smaller.

  When reactor current iL falls to zero, LC resonance occurs due to the inductance component of reactor 12 and the parasitic capacitance of switching element 11, and a resonance current due to the LC resonance flows into reactor current iL. During the period when the resonance current flows through the reactor, the reactor current iL becomes zero and the zero current signal ZCD becomes "H" at the timing of rising. By setting the gate signal to “H” at the timing when the zero current signal ZCD becomes “H”, the switching loss generated by switching of the switching element 11 can be reduced.

  Next, the outline of the variable count ZCS control will be described. In the variable count ZCS control, the rise of the zero current signal ZCD to “H” is counted during a period in which the resonance current flows through the reactor 12, and the gate signal Ga is set to “H” when the count reaches a predetermined number. . At this time, the count number until the gate signal Ga is set to “H” is varied based on the AC voltage component superimposed on the pulsating voltage Vin. Specifically, when the voltage value of the pulsating voltage Vin becomes larger due to the superposed AC voltage component, the count number until the gate signal Ga is set to “H” is increased. Further, when the voltage value of the pulsating voltage Vin becomes smaller due to the superposed AC voltage component, the count number until the gate signal Ga is set to “H” is reduced.

  4 and 5 are explanatory diagrams of the operation of the variable count ZCS control. FIG. 4 counts the zero current signal ZCD, and sets the gate signal Ga to “H” at the timing when the count number becomes two. FIG. 5 counts the zero current signal ZCD, and sets the gate signal Ga to “H” at the timing when the count number becomes three. 5 in which the count number of the zero current signal ZCD is increased and the gate signal Ga is set to “H” is shown in FIG. 4 where the count number of the zero current signal ZCD is reduced and the gate signal Ga is set to “H”. It can be seen that the period during which the gate signal Ga is set to “L” increases and the duty ratio of the gate signal Ga decreases as compared to the case shown. That is, when the pulsating voltage Vin increases due to the superimposed AC voltage component, the duty ratio of the gate signal Ga is reduced by increasing the count number of the zero current signal ZCD, thereby suppressing an increase in the output voltage. Further, when the pulsating voltage Vin becomes smaller due to the superimposed AC voltage component, the duty ratio of the gate signal Ga is increased by reducing the count number of the zero current signal ZCD, and a decrease in the output voltage is suppressed. By the above operation, a ripple component generated in the output voltage can be reduced.

  The variable count ZCS control varies the number of counts of the zero current signal ZCD in accordance with the power supplied to the load 5. Specifically, at a light load, the count number of the zero current signal ZCD is increased as compared with a high load. Thereby, even if the power supplied to the load 5 is reduced and the period during which the reactor current iL increases and the period during which the reactor current iL decreases are shortened, it is possible to prevent the switching frequency from increasing. The count number of the zero current signal ZCD may be set as long as the switching frequency is set so as not to increase the frequency. For example, the count number is set so that the switching frequency becomes almost the same regardless of the power of the load 5. Alternatively, for example, the switching frequency may be set to be lower when the power supplied to the load 5 is small than when the power supplied to the load is large.

  Next, details of the power control unit 3 will be described. The power control unit 3 may be a general digital control circuit (including a circuit using software having the same function as the digital control circuit) which does not entirely use an IC (Interrupted Circuit). It may be a digital control circuit. Furthermore, all may be analog control circuits that do not use digital control circuits. In the present embodiment, a configuration as a digital control circuit using a microcomputer will be described.

  The on-time generator 32 calculates the difference between the output voltage detection value Vosen and the target voltage value Voref, and determines the on-time of the switching element 11 so that the difference becomes zero. The calculation of the on-time is based on the output voltage detection value Vosen and the target voltage, such as classical control such as PI control (proportional integral control) and PID control (proportional differential integral control), or modern control such as H∞ (H-infinity) control. Any control may be used as long as the difference between the values Voref is controlled to be zero. By calculating the on-time of the on-time generator 32, the output voltage Vo can be adjusted to an arbitrary target voltage value Voref.

  The on-timing generation unit 33 performs variable count ZCS control using the zero current signal ZCD, the input voltage detection value Vinsen, and the output voltage detection value Vosen, and generates an on-timing of the gate signal Ga.

  The operation of the on-timing generation unit 33 will be described with reference to the flowchart of FIG. Note that, in FIG. 6, the symbol S means a processing step.

  First, when the on-timing generation unit 33 starts the control processing, the input voltage detection value Vinsen obtained by detecting the input voltage (pulsation voltage) Vin by the input voltage detection unit 7 of the power supply main circuit unit 2 and the output voltage detection unit 8, an output voltage detection value Vosen obtained by detecting the output voltage Vo is taken in (step S1).

  Next, the power supply to the load 5 is calculated from the output voltage detection value Vosen and the resistance value of the load 5 known in advance, and the reference count cnt is determined based on the power supply to the load 5 (step S2). The reference count cnt is an integer of 1 or more, and is set so that the numerical value increases as the power supplied to the load 5 decreases. The execution position of step S2 need not be the position shown in FIG. 6, and step S2 may be executed after step S3 or step S4 described later. Note that a current detection circuit for the current flowing through the load 5 may be added, and the supply power of the load 5 may be calculated using the detected value of the current flowing through the load 5 and the output voltage detection value Vosen.

  Next, a DC voltage component of the input voltage detection value Vinsen is calculated by calculating an average value of the input voltage detection value Vinsen, and the calculated result is set as a comparison threshold value Vcomp (step S3). Step S3 does not need to be performed for each control cycle of the on-timing generation unit 33, and after setting the comparison threshold Vcomp once, step S3 may be omitted. The comparison threshold Vcomp does not need to be calculated from the input voltage detection value Vinsen. If the magnitude of the DC voltage component of the input power supply 4 is known in advance, the value may be set as the comparison threshold Vcomp. . For example, when the input power supply 4 is an AC / DC converter, the target output voltage of the AC / DC converter may be set in advance as the comparison threshold Vcomp.

  Next, in step S4, a magnitude comparison between the comparison threshold value Vcomp calculated in step S3 and the input voltage detection value Vinsen is performed. FIG. 7 is a diagram for explaining the magnitude comparison between the comparison threshold value Vcomp and the input voltage detection value Vinsen. In FIG. 7, a period T1 in which the input voltage detection value Vinsen is equal to or larger than the comparison threshold value Vcomp is indicated by hatching, and is distinguished from a period T2 in which the input voltage detection value Vinsen is smaller than the comparison threshold value Vcomp.

  By comparing the comparison threshold value Vcomp with the input voltage detection value Vinsen in step S4, during the period T2 where the input voltage detection value Vinsen is smaller than the comparison threshold value Vcomp, a value obtained by subtracting the decrease correction value x1 from the reference count cnt is used as the turn-on count ZCDcnt. Set (step S5). In the period T1 in which the input voltage detection value Vinsen is equal to or greater than the comparison threshold value Vcomp, a value obtained by adding the increase correction value x2 to the reference count cnt is set as the turn-on count ZCDcnt (step S6). Here, the decrease correction value x1 and the increase correction value x2 are both integers equal to or greater than 0, but the decrease correction value x1 and the increase correction value x2 do not become 0 at the same time. The decrease correction value x1 has a value less than the reference count cnt. Therefore, the turn-on count ZCDcnt does not become zero or a negative value.

Next, the zero current signal generation unit 31 of the power supply control unit 3 outputs a zero current signal ZCD indicating the timing at which the reactor current iL becomes zero, and the on-timing generation unit 33 detects the zero current signal ZCD (step S7). ). Then, the detection of the zero current signal ZCD is counted, and the timing when the count signal reaches the turn-on count ZCDcnt to set the gate signal Ga to “H”, that is, the ON timing of the switching element 11 is determined (step S8).
The above is the description of the operation of the on-timing generation unit 33 (the flowchart of FIG. 6). As described above, the variable count ZCS control can be realized by the operation.

  Actually, the effect of the variable count ZCS control of the present embodiment was confirmed using a circuit simulation of Myway Plus. In this simulation, a DC voltage of 300 V and an AC voltage of 20 V (100 Hz) were connected in series and used as an input voltage. The comparison threshold value Vcomp was set to 300 V, the reference count cnt was set to 3, the decrease correction value x1 was set to 1, the increase correction value x2 was set to 1, and the target voltage value Voref was set to 200 V.

8 and 9 are diagrams illustrating simulation results when the variable count ZCS control is applied and when it is not applied. 8 and 9, the upper diagrams show the waveforms of the input voltage detection value Vinsen and the comparison threshold value Vcomp, the middle diagrams show the waveforms of the output voltage Vo, and the lower diagrams show the turn-on count ZCDcnt.
FIG. 8 compares the input voltage detection value Vinsen with the comparison threshold value Vcomp. When the input voltage detection value Vinsen is equal to or greater than the comparison threshold value Vcomp (Vinsen> = Vcomp), the turn-on count ZCDcnt is 4, and the input voltage detection value Vinsen is the comparison threshold value Vcomp. When it is smaller (Vinsen <Vcomp), it can be confirmed that the turn-on count ZCDcnt is 2. FIG. 9 shows a simulation result when the turn-on count ZCDcnt is always set to 2 regardless of the magnitude of the input voltage detection value.

  The simulation result of FIG. 8 confirms that the pulsation of the output voltage Vo is smaller than the simulation result of FIG. The ripple rate of the output voltage Vo calculated by dividing the difference between the maximum value and the minimum value of the output voltage Vo by the average value of the output voltage Vo is 0.068 in the simulation result of FIG. 8 and 0 in the simulation result of FIG. .131. Therefore, the output voltage ripple reduction effect of the variable count ZCS control was confirmed.

  In the present embodiment, as shown in FIG. 7, the turn-on count ZCDcnt is determined by comparing the input voltage detection value Vinsen with the comparison threshold value Vcomp calculated based on the input voltage detection value Vinsen. However, the turn-on count ZCDcnt may be determined in any manner as long as it is determined based on the AC voltage component superimposed on the DC voltage component of the input voltage (pulsating voltage). For example, as shown in FIG. 10, Vcomp1 and Vcomp2 may be provided as comparison thresholds, and these comparison thresholds Vcomp1 and Vcomp2 may be compared with the input voltage detection value Vinsen. In the case of the example shown in FIG. 10, the turn-on count ZCDcnt can be changed by three during one cycle of the pulsation voltage Vin. That is, in a period T30 in which the input voltage detection value Vinsen is smaller than the comparison threshold value Vcomp1, in a period T20 in which the input voltage detection value Vinsen is smaller than the comparison threshold value Vcomp2 and equal to or more than the comparison threshold value Vcomp1, and in a period T10 in which the input voltage detection value Vinsen is equal to or more than the comparison threshold value Vcomp2. Are determined so that the turn-on count ZCDcnt increases in order.

  Further, in this embodiment, the configuration using the step-down chopper circuit shown in FIG. 1 as the converter 6 has been described. However, the converter 6 has a switching element and a reactor, and any circuit that performs DC / DC conversion. A simple circuit may be used. For example, as shown in FIG. 11, a configuration using a boost chopper circuit as converter 6 may be employed.

  As shown in FIG. 11, even when the converter 6 is configured to use a step-up chopper circuit, the variable count ZCS control can be performed similarly to the configuration using the step-down chopper circuit for converter 6 described above. That is, the ripple of the output voltage Vo can be reduced by varying the turn-on count ZCDcnt according to the AC voltage component superimposed on the input voltage (pulsation voltage) Vin.

  The effect of the variable count ZCS control of the present embodiment was confirmed using a circuit simulation of Myway Plus Co., Ltd. in the case of using the boost chopper circuit of FIG. 11 as the converter 6. In this simulation, a DC voltage of 100 V and an AC voltage of 20 V (100 Hz) were connected in series and used as an input voltage. The comparison threshold value Vcomp was set to 100 V, the reference count cnt was set to 3, the decrease correction value x1 was set to 1, the increase correction value x2 was set to 1, and the target voltage value Voref was set to 200V.

  12 and 13 show simulation results when the variable count ZCS control is applied and not applied when the boost chopper circuit of FIG. 12 and 13, the upper graph shows the waveform of the input voltage detection value Vinsen and the comparison threshold Vcomp, the middle graph shows the waveform of the output voltage Vo, and the lower graph shows the turn-on count ZCDcnt.

  FIG. 12 shows a simulation waveform when the variable count ZCS control is applied. When the input voltage detection value Vinsen is equal to or greater than the comparison threshold value Vcomp (Vinsen> = Vcomp), the turn-on count ZCDcnt is 4, and the input voltage detection value Vinsen is the comparison threshold value Vcomp. When it is smaller (Vinsen <Vcomp), it can be confirmed that the turn-on count ZCDcnt is 2. FIG. 13 shows a simulation waveform when the turn-on count ZCDcnt is always set to 2 regardless of the input voltage detection value Vinsen. It can be confirmed that the pulsation of the output voltage Vo is smaller when the variable count ZCS control in FIG. 12 is applied than when the variable count ZCS control is not applied in FIG. The ripple rate of the output voltage Vo calculated by dividing the difference between the maximum value and the minimum value of the output voltage Vo by the average value of the output voltage Vo is 0.043 in FIG. 12 and 0.069 in FIG. Met. Therefore, also in the case of using the boost chopper circuit as the converter 6, the effect of reducing the output voltage ripple by the variable count ZCS control was confirmed.

  Further, in the present embodiment, as shown in FIG. 1, zero point of the current flowing through reactor 12 is detected as zero current signal ZCD using zero current detection unit 9 and zero current signal generation unit 31, and count variable ZCS control is performed. But not limited to this. That is, the timing at which the voltage applied to the switching element 11 becomes zero may be detected as the zero voltage signal ZVD, and the zero voltage signal ZVD may be used instead of the zero current signal ZCD. In this case, instead of the zero current detector 9 and the zero current signal generator 31 shown in FIG. 1, as shown in FIG. 14, a zero voltage detector 90 for detecting a voltage applied to the switching element 11 and a zero voltage detector 90 are applied to the switching element 11. The zero voltage signal generation unit 310 that outputs the timing when the voltage becomes zero as the zero voltage signal ZVD is used. Other configurations and operations are the same as those described above.

  Further, in the present embodiment, the control method of determining the on-timing of the switching element using the count number of zero current signal ZCD has been described. However, the on-timing of the switching element is determined in accordance with the AC voltage component superimposed on the input voltage. As long as it is determined, the configuration may be such that the zero current signal ZCD is not counted. For example, it may be realized by a control method in which the ON timing of the switching element is set to a timing at which a predetermined time has elapsed, and the predetermined time is made variable by an AC voltage component superimposed on the input voltage.

  Hereinafter, control for varying the predetermined time by an AC voltage component superimposed on the input voltage will be described with reference to the circuit diagram of the power conversion device in FIG. 15 and the circuit operation diagram in FIG. 15, the configuration of the power supply main circuit unit 2 and the power supply control unit 3 of the power conversion device 1 is basically the same as the configuration of FIG. The operation is different.

  In FIG. 15, power supply control unit 3 includes a zero current signal generation unit 31 that outputs a zero current signal ZCD indicating a timing at which the current flowing through reactor 12 becomes zero based on voltage VLsen obtained from zero current detection unit 9, An on-time generator 32 that derives the on-time of the switching element 11 based on the output voltage detection value Vosen and the target voltage value Voref, and determines the timing at which a predetermined time has elapsed based on the zero current signal ZCD as the on-timing of the switching element 11. And a switching drive unit 34 that receives the ON time from the ON time generation unit 32 and the ON timing from the ON timing generation unit 33A to generate a gate signal Ga for operating the switching element 11. I have.

  In FIG. 16, the on-timing generation unit 33A starts time measurement from the first rising timing t1 of the zero current signal ZCD after the switching element 11 is turned off, and performs switching at a timing when the measured time reaches a predetermined time Td. The on-timing for turning on the element 11 is determined. The predetermined time Td for determining the ON timing of the switching element 11 is determined by an AC voltage component superimposed on the input voltage. That is, when the detected value Vinsen of the input voltage is larger due to the AC voltage component superimposed on the DC voltage component, the predetermined time Td is longer than when the detected value Vinsen of the input voltage is smaller than the AC voltage component superimposed on the DC voltage component. Is performed to increase the delay.

  By performing the delay control described with reference to FIGS. 15 and 16, the same operation as the configuration using the zero current signal ZCD can be realized, and the effect of reducing the output voltage ripple can be obtained. The timing for starting the time measurement is not based on the zero current signal ZCD, but may be based on, for example, the zero voltage signal ZVD described with reference to FIG. The timing at which the switching element 11 is turned on or the timing at which the switching element 11 is turned off may be used.

  FIG. 17 shows an example of a power converter that starts time measurement from the timing when the switching element 11 is turned on or off. In FIG. 17, the switching detection unit 35 detects the timing of turning on or off the switching element 11 based on the gate signal Ga from the switching driving unit 34. The on-timing generation unit 33B starts time measurement from the timing at which the switching element 11 is turned on or off, and determines the on-timing at which the switching element 11 is turned on when the measured time reaches a predetermined time. Other operations are the same as those described with reference to FIGS.

  As described above, according to the first embodiment, a power supply main circuit unit that includes a switching element and a reactor, converts power of an input voltage in which an AC voltage component is superimposed on a DC voltage component, and outputs the input voltage to a load, When the detected value of the input voltage is larger due to the AC voltage component superimposed on the DC voltage component, the ON timing of the switching element is delayed compared to when the detected value of the input voltage is smaller due to the AC voltage component superimposed on the DC voltage component. Since the power supply control unit that determines the ON timing of the switching element is provided as described above, it is possible to reduce the ripple generated in the output voltage.

  In addition, the power supply control unit compares the detected value of the input voltage with the comparison threshold, and when the detected value of the input voltage is equal to or greater than the comparison threshold, delays the ON timing of the switching element as compared with when the detected value of the input voltage is smaller than the comparison threshold. Since the ON timing of the switching element is determined, the ripple generated in the output voltage can be reduced by simple control.

  Further, since the comparison threshold is a DC voltage component of the input voltage, the ripple generated in the output voltage can be reduced by simple control.

  Further, the power supply control unit outputs a zero current signal that indicates a timing when the current flowing through the reactor becomes zero, and a zero voltage that outputs a zero voltage signal that indicates the timing when the voltage applied to the switching element becomes zero. An on-timing generation unit that counts one of the signal generation units and one of the zero current signal and the zero voltage signal, and determines the timing when the count reaches a predetermined number as the on timing of the switching element. And a switching drive unit that turns on the switching element at the on-timing determined by the on-timing generation unit. When the detected value of the input voltage is larger than the AC voltage component superimposed on the DC voltage component, the detected value of the input voltage is Is smaller than the AC voltage component superimposed on the DC voltage component, The variable count zero-cross switching control that increases the constant number is performed, so that the ripple generated in the output voltage can be reduced, and the timing at which the current flowing through the reactor becomes zero or the voltage applied to the switching element becomes zero. Since the switching element is turned on at the timing, the switching loss and the switching noise can be reduced.

  The power supply control unit includes a zero current signal generation unit that outputs a zero current signal indicating a timing when the current flowing through the reactor becomes zero, and a zero voltage that outputs a zero voltage signal indicating a timing when the voltage applied to the switching element becomes zero. A signal generation unit, and one of the switching detection units that detects the timing at which the switching element is turned on or off, and the zero current signal, the zero voltage signal, and the one at which the switching element is turned on or off. An on-timing generation unit that determines a timing at which a predetermined time has elapsed as an on-timing of the switching element; and a switching drive unit that turns on the switching element at the on-timing determined by the on-timing generation unit. Due to the AC voltage component superimposed on the At the time, compared to when the detected value of the input voltage becomes smaller due to the AC voltage component superimposed on the DC voltage component, the delay control for extending the predetermined time is performed. Can be reduced.

  In addition, the power supply control unit determines the on-timing of the switching element so that the on-timing of the switching element is delayed when the power supplied to the load is low as compared to when the power supplied to the load is high. When the power supplied to the load is low, the variable count zero-cross switching control for increasing the predetermined number of times is performed as compared with the case where the power supplied to the load is high. Furthermore, when the power supplied to the load is low, delay control for extending the predetermined time is performed as compared to when the power supplied to the load is high. As a result, even when the power supplied to the load fluctuates, it is possible to prevent the switching frequency from increasing, and to prevent an increase in switching loss.

When the power supplied to the load is large, (1) when the detected value of the input voltage is large due to the AC voltage component superimposed on the DC voltage component, The switching timing of the switching element is determined by determining the on-timing of the switching element so as to delay the on-timing of the switching element as compared with the case where the alternating voltage component superimposed on the component becomes smaller,
When the power supplied to the load is small, (2) a control method of performing switching control of the switching element at a constant switching cycle, and (3) a detection value of the input voltage is independent of the AC voltage component superimposed on the DC voltage component. A control method that counts the number of zero current signals indicating the timing at which the current flowing in the reactor becomes zero, determines the timing at which the counted number reaches a predetermined number as the ON timing of the switching element, and performs switching control of the switching element. May be performed.
According to this, when the power supplied to the load is large, the ripple generated in the output voltage can be reduced.

  Further, the power supply control unit determines the on-time of the switching element based on the output voltage detection value of the power supply main circuit unit and the target voltage value, so that a desired output voltage can be obtained.

Embodiment 2 FIG.
FIG. 18 is a circuit block diagram showing a power converter according to Embodiment 2 of the present invention. 18, the same reference numerals are given to the same or corresponding components as those in FIG. The second embodiment is different from the first embodiment in that the load is an LED (Light Emitting Diode) module 50. The point that the load 5 in FIG. 8 is changed to the output current detection unit 80, the output voltage detection value Vosen is changed to the output current detection value Iosen, and the target voltage value Voref input to the on-time generation unit 32 is changed to the target current value Ioref. Is different. The output current detection unit 80 includes, for example, a current detection resistor (not shown), and detects a potential difference generated between both ends of the current detection resistor as a voltage conversion value Isen corresponding to a current flowing through the LED module 50. In addition, the LED module 50 has a configuration in which all LED chips are connected in series in FIG. 18, but is not limited to a case where the LED chips are connected in series, and may be a parallel connection or a series-parallel connection, or may be one LED. Further, although an LED is connected as a load here, an organic electroluminescence (organic EL), a laser diode, or the like may be used instead of the LED.

  Here, an LED is usually suitable for current control because of its characteristics. Therefore, in the present embodiment, the control for adjusting the output voltage to the target voltage is changed to the control for adjusting the output current to the target current. In FIG. 18, the on-time generator 32 derives the on-time of the switching element 11 based on the output current detection value Iosen and the target current value Ioref. That is, the on-time generator 32 calculates the difference between the output current detection value Iosen and the target current value Ioref, and determines the on-time of the switching element 11 so that the difference becomes zero. With this configuration, the output current flowing through the LED module 50 can be controlled by the same control as in the first embodiment.

  Further, as described in the first embodiment, when the detected value Vinsen of the input voltage is increased by the AC voltage component superimposed on the DC voltage component, the power supply control unit 3 converts the detected value Vinsen of the input voltage to the DC voltage component. Since the switching control is performed by determining the on-timing of the switching element 11 so that the on-timing of the switching element 11 is delayed as compared with the case where the alternating voltage component becomes small, the ripple of the output current can be reduced. .

  In particular, when an LED is used as the load, if a large ripple is superimposed on a current flowing through the LED, a problem that light flicker appears in a security camera, a video camera, or the like occurs. In the second embodiment, the ripple generated in the output current can be reduced by the variable count ZCS control or the delay control described in the first embodiment, so that the occurrence of light flicker can be prevented. Also, when the power converter has a dimming function for adjusting the light amount of the LED, the dimming function can be changed if the target current value Ioref normally input from the outside can be changed by the dimming function. realizable.

  As described above, according to the second embodiment, the ON time of the switching element is determined based on the output current detection value and the target current value, so that the output current can be adjusted to the target current, The same effect as the effect described in the first embodiment can be obtained. In particular, the ripple generated in the output current can be reduced.

  In the present invention, it is possible to freely combine the respective embodiments or appropriately modify or omit the respective embodiments within the scope of the present invention.

Claims (14)

A power supply main circuit unit having a switching element and a reactor, converting power of an input voltage in which an AC voltage component is superimposed on a DC voltage component, and outputting the converted power to a load;
When the detected value of the input voltage is larger due to the AC voltage component superimposed on the DC voltage component, the ON state of the switching element is smaller than when the detected value of the input voltage is smaller due to the AC voltage component superimposed on the DC voltage component. A power conversion device including a power supply control unit that determines an ON timing of the switching element so as to delay the timing. The power control unit compares the detected value of the input voltage with a comparison threshold, and when the detected value of the input voltage is equal to or greater than the comparison threshold, the on-timing of the switching element is compared with when the detected value of the input voltage is smaller than the comparison threshold. The power converter according to claim 1, wherein the ON timing of the switching element is determined so as to delay the switching time. The power converter according to claim 2, wherein the comparison threshold is a DC voltage component of the input voltage. The power supply control unit includes a zero current signal generation unit that outputs a zero current signal indicating a timing when the current flowing through the reactor becomes zero, and a zero current signal that outputs a zero voltage signal indicating a timing when the voltage applied to the switching element becomes zero. Any one of the voltage signal generation units and the number of times of the one of the zero current signal and the zero voltage signal are counted, and a timing at which the count reaches a predetermined number is determined as the ON timing of the switching element. An on-timing generation unit, comprising a switching drive unit that turns on the switching element at the on-timing determined by the on-timing generation unit,
When the detected value of the input voltage is larger due to the AC voltage component superimposed on the DC voltage component, the predetermined number of times is smaller than when the detected value of the input voltage is smaller due to the AC voltage component superimposed on the DC voltage component. The power converter according to any one of claims 1 to 3, wherein control for increasing the power is performed. The power supply control unit includes a zero current signal generation unit that outputs a zero current signal indicating a timing when the current flowing through the reactor becomes zero, and a zero current signal that outputs a zero voltage signal indicating a timing when the voltage applied to the switching element becomes zero. One of a voltage signal generation unit and a switching detection unit that detects a timing at which the switching element is turned on or off, and one of the zero current signal, the zero voltage signal, and a timing at which the switching element is turned on or off. An on-timing generation unit that determines a timing at which a predetermined time has elapsed from any one as the on-timing of the switching element, and a switching drive unit that turns on the switching element at the on-timing determined by the on-timing generation unit,
When the detected value of the input voltage is larger due to the AC voltage component superimposed on the DC voltage component, the predetermined time is shorter than when the detected value of the input voltage is smaller due to the AC voltage component superimposed on the DC voltage component. The power converter according to any one of claims 1 to 3, wherein a delay control for increasing the length is performed. The power supply control unit determines the on-timing of the switching element so that the on-timing of the switching element is delayed when the power supplied to the load is low, as compared to when the power supplied to the load is high. The power converter according to any one of claims 1 to 3. The power converter according to claim 4, wherein the power supply control unit performs control to increase the predetermined number of times when the power supplied to the load is low as compared to when the power supplied to the load is high. The power conversion device according to claim 5, wherein the power supply control unit performs delay control for increasing the predetermined time when the power supplied to the load is low as compared to when the power supplied to the load is high. The power supply control unit is configured such that, when the power supplied to the load is large, when the detected value of the input voltage is increased by the AC voltage component superimposed on the DC voltage component, the detected value of the input voltage is reduced to the DC voltage component. Compared with when the voltage becomes smaller due to the superposed AC voltage component, the on-timing of the switching element is determined so as to delay the on-timing of the switching element, and the switching of the switching element is controlled.
When the power supplied to the load is small, the control method for performing switching control on the switching element at a constant switching cycle, and the reactor is independent of the AC voltage component in which the detected value of the input voltage is superimposed on the DC voltage component. Control that counts the number of zero current signals indicating the timing at which the current flowing through the switching element becomes zero, determines the timing at which the counted number reaches a predetermined number as the on timing of the switching element, and performs switching control of the switching element. The power converter according to claim 1, wherein at least one of the methods is controlled. The power converter according to any one of claims 1 to 9, wherein the power control unit determines an on-time of the switching element based on an output voltage detection value of the power main circuit unit and a target voltage value. . The power converter according to any one of claims 1 to 9, wherein the power control unit determines an on-time of the switching element based on an output current detection value of the power main circuit unit and a target current value. . The power converter according to claim 11, wherein the power supply main circuit unit is connected to any one of an LED, organic electroluminescence, and a laser diode as the load. The power converter according to any one of claims 1 to 12, wherein the power supply main circuit unit includes a step-down chopper circuit. The power converter according to any one of claims 1 to 12, wherein the power supply main circuit unit is configured by a boost chopper circuit.

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