JP2017195664A - Resonant power supply - Google Patents

Abstract

A resonance type power supply device that achieves downsizing and cost reduction is provided.
[Solution]
A resonance-type power supply apparatus that applies a pulsed voltage to a transformer and a resonance element by switching an input voltage by a primary side switching element, and controls an output voltage by switching by a secondary side switching element. Is set to be equal to or less than the transformer turns ratio of the amplitude of the pulse voltage, the switching frequency of the set period is obtained, and the gate signal of the secondary side switching element is obtained based on the obtained switching frequency. A configuration having a control function to be corrected is adopted.
[Selection] Figure 1

Description

  The present invention relates to a resonant power supply device used in industrial equipment, information equipment, and the like.

  An input voltage and an output voltage of a power supply device used for industrial equipment, information equipment, or the like that converts a direct current input voltage into a direct current output voltage are insulated using a transformer. One of the high-efficiency circuit configurations used for an insulated power supply device is an LLC current resonance type circuit. Since the LLC current resonance type circuit uses a resonance phenomenon to flow a current in a sine wave shape and performs switching at a timing when the current becomes small, it is possible to realize a highly efficient power supply device with small switching loss. In the resonance type power supply device that is a power supply device using such a resonance phenomenon, the ideal off timing of the secondary semiconductor element depends on the resonance frequency. There was a problem that a loss occurred in the secondary semiconductor element.

  On the other hand, as described in, for example, Japanese Patent Application Laid-Open No. 2005-168167 (Patent Document 1), means for estimating the current resonance frequency from the current flowing through the resonance element is known.

JP 2005-168167 A

  As described in Patent Document 1, the resonance frequency can be estimated from the waveform and frequency of the resonance current. However, in order to estimate the resonance frequency, it is necessary to detect current at a frequency higher than the switching frequency, which is not realistic.

  In order to solve the above-described problem, the present invention, as an example, applies a pulsed voltage to the transformer and the resonant element by switching the input voltage by the primary side switching element, and the secondary side switching element. The resonance type power supply device that controls the output voltage by switching in accordance with the output voltage, wherein the command value of the output voltage is set to be equal to or less than the turn ratio of the transformer of the amplitude of the pulsed voltage, and the switching frequency in the set period And having a control function of correcting the gate signal of the secondary side switching element based on the acquired switching frequency.

  According to the present invention, it is possible to provide an inexpensive and highly efficient resonant power supply apparatus that can easily grasp the resonant frequency.

1 is a circuit diagram of a resonant power supply device according to Embodiment 1. FIG. 3 shows frequency characteristics of the resonant power supply device according to the first embodiment. 4 is a waveform at the time of starting the resonance type power supply device according to the first embodiment. FIG. 3 is an operation waveform diagram of the resonance type power supply device according to the first embodiment. FIG. 6 is a circuit diagram of a resonant power supply device according to a second embodiment. 6 is a circuit diagram of a resonant power supply device according to Embodiment 3. FIG.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a circuit diagram of a resonant power supply device according to this embodiment. In FIG. 1, the resonant power supply device 01 includes a power supply main circuit 02 and a power supply control block 03. An input voltage Vin is applied from the input power supply Ein to the input terminal of the power supply main circuit 02, and a load Ro is connected to the output terminal.

  The power supply main circuit 02 includes an input capacitor Cin, a primary side semiconductor element (switching element) 04, a resonance element 05, a transformer 06, a secondary side semiconductor element (switching element) 07, and an output capacitor Co, and an input voltage Vin The output voltage Vo that is the voltage across the output capacitor Co is detected and transmitted to the power supply control block 03. This detection / transmission function is composed of, for example, an operational amplifier or the like, and the power supply control block 03 receives the signal via an A / D converter.

  The power supply control block 03 includes a control amount calculator 12 that receives Vo and calculates a switching frequency Fsw at which Vo becomes an output voltage command value Vref sent from the host controller, and the primary-side semiconductor element based on Fsw 04 is generated by the primary gate signal generator 14. In this embodiment, since the primary side semiconductor element 04 has a full bridge configuration of Q1, Q2, Q3, and Q4, the primary side gate signal generator 14 generates the gate signals Vg1, Vg2, Vg3, and Vg4. The power supply main circuit 02 drives Q1, Q2, Q3, and Q4 according to the signal, and controls Vo. The power supply control block 03 may be realized by a dedicated control IC.

  The primary-side semiconductor element 04 is repeatedly turned on and off in accordance with the gate signals Vg1, Vg2, Vg3, and Vg4 from the power supply control block 03, and applies a pulsed voltage to the resonant element 05 and the transformer 06. For example, when Q1 and Q4 are on and Q2 and Q3 are off, a voltage of Vin is applied to the resonant element 05, and when Q2 and Q3 are on and Q1 and Q4 are off, the resonant element 05 is − A voltage of Vin is applied. Therefore, in this embodiment, a pulse voltage having an amplitude of Vin is applied to the resonance element 05 and the transformer 06.

  The resonant element 05 includes a resonant inductance Lr and a resonant capacitor Cr. The resonance inductance Lr is in series with the leakage inductance of the transformer 06. In this embodiment, the leakage inductance of the transformer is not described, but the leakage inductance of the transformer is assumed to be included in the resonance inductance Lr. Although Lr and Cr are described separately arranged on the primary side terminal of the transformer, they may be arranged in series on one side as long as they are arranged in series on the electric circuit.

  In the transformer 06, the exciting inductance is Lm, the number of turns on the primary side is N1, and the number of turns on the secondary side is N2.

  The secondary-side semiconductor element 07 has a full bridge configuration of Q5, Q6, Q7, and Q8. These gate signals are Vg5, Vg6, Vg7, Vg8, and are generated by the secondary side gate signal generator 15 of the power supply control block 03.

  FIG. 2 shows the frequency characteristics of the resonance type power supply device 01 in this embodiment. The resonant power supply device 01 obtains a desired output voltage Vo by adjusting the switching frequency Fsw. FIG. 2 is a graph of frequency characteristics in which the horizontal axis is Fsw and the vertical axis is the gain M. The gain M is defined by the product of the input / output voltage ratio (Vo / Vin) and the turns ratio of the transformer 07 (N1 / N2), and the output voltage when operating at a certain switching frequency Fsw is the number of turns of the input voltage Vin. This is a criterion for confirming whether the value is larger or smaller than the value divided by the ratio.

  The resonance type power supply device 01 has a characteristic of having a resonance frequency Fo determined by Lr and Cr, and having a gain M of 1 when Fsw is operated at Fo. This feature is more accurate when the load is light because a voltage drop due to parasitic resistance components occurs when the load current is large.

  When operating at the switching frequency Fsw at light load, if the Lr and Cr as designed can be manufactured, the gain M becomes 1, so that the resonance frequency Fo as the designed value can be obtained. When Lr or Cr varies due to aging, the graph of the frequency characteristics changes. In the case of variation A, the resonance frequency shifts to Fo (A), and in the case of variation B, the resonance frequency shifts to Fo (B).

  In the present embodiment, the switch 11 and the resonance frequency memory 13 are provided in the power supply control block 03 in order to grasp the deviation of the resonance frequency. The power supply control block 03 inputs the sampling mode switching signal Sm to the switching device 11 and the resonance frequency storage device 13, and the normal mode in which the voltage command value operates with the voltage command value Vref sent from the host, and the resonance element 05. And a sampling mode that stores the switching frequency Fsw at that time as the resonance frequency Fo, and operates with a value obtained by dividing the amplitude of the pulse voltage applied to the transformer 06 by the turn ratio. The resonance frequency Fo acquired in the sampling mode is a resonance frequency corresponding to Lr and Cr deviated from design values due to manufacturing variations and aging degradation.

  FIG. 3 shows waveforms at the start-up in this embodiment. 3A shows the output voltage Vo, FIG. 3B shows the sampling mode switching signal Sm, and FIG. 3C shows the standby completion signal EN. The sampling mode is preferably performed at light load for the reasons described above. Since it is difficult to grasp the timing when the load is light after supplying power to the load, it is desirable to provide a sampling mode when the power is turned on. Therefore, as shown in FIG. 3, when t0 is the time when the activation signal of the resonance power supply device 01 is input, the sampling mode is first shifted to at t1, and the output voltage command value of the power supply is divided by Vin by the turn ratio. Value. Switching is gradually started from t2, and at t3, the output voltage Vo becomes a value obtained by dividing Vin by the turns ratio. Between t3 and t4, the resonance frequency memory 13 stores the switching frequency Fsw as the resonance frequency Fo. After the storage is completed, the switch 11 switches to the voltage command value Vref sent from the host at t4, and after the output voltage Vo becomes Vref, the standby completion signal EN of the resonance type power supply device 01 is transmitted to the outside at t5. To do. Note that Vo rises linearly during the period from t2 to t3, but it is also possible to slowly increase the command value so that the final voltage in the sampling mode becomes a value obtained by dividing Vin by the turns ratio.

  According to the present embodiment, the resonant power supply device 01 is characterized in that the output voltage has a two-stage stable potential before outputting the standby completion signal EN. One of the potentials is a value corresponding to a turn ratio of Vin, and the other is a voltage command value Vref from the host microcomputer.

  In the present embodiment, the secondary side gate signal generator 15 uses the resonance frequency stored as described above. FIG. 4 shows an operation waveform diagram for one switching cycle when the switching frequency Fsw is smaller than the stored resonance frequency Fo in the normal mode.

  In FIG. 4, gate signals Vg1, Vg2, Vg3, Vg4, Vg5, Vg6, Vg7, Vg8, current ILr flowing through resonance inductance Lr, and source-drain currents I5 of secondary semiconductor elements Q5, Q6, Q7, Q8. , I6, I7, and I8, each showing a waveform of one switching period. 3 and 4 are different in time axis, and t0 to t5 in FIG. 3 and t10 to t16 in FIG. 4 are irrelevant. In FIG. 4, one cycle is from t10 to t16. Vg1 and Vg4 are turned on at t10 and turned off at t13. Vg2 and Vg3 are turned on at t14 and turned off at t16. From t10 to t11 and from t13 to t14 are dead times. Since Vg2 and Vg3 are on and Vin is applied to the resonance element 05 from t10 when Vg2 and Vg3 are turned off, a sinusoidal current ILr flows through Lr during a period from t10 to t12. ILr is an excitation current route that flows to Cr of the resonance element 05 through the excitation inductance Lm of the transformer 06, and a load current route that flows from the transformer 06 to the secondary side semiconductor element 07 and returns to Cr through the output capacitor Co or the load Ro. Divided into two routes.

  The excitation current ILm flowing in the excitation current route rises with a certain slope during the period from t10 to t12 because Vin is applied to Lm. Here, ILm, which is a sinusoidal waveform, and ILm, which continues to rise at a constant slope, have the same value at t12. From t10 to t12, since ILr was larger than ILm, I5 and I8 flowed in the positive direction through Q5 and Q8 of the load current route. If Vg5 and Vg8 are in the on state after t12, negative current flows through I5 and I8 after t12, and the current flows backward, so the efficiency deteriorates. That is, it is desirable to turn on the period from t10 to t12 flowing in the positive direction in Q5 and Q8. Similarly, it is desirable that Vg6 and Vg7 are turned on during the period from t13 to t15.

  If the load is in a constant steady state, the resonance current ILr (t10) at t10 is equal to the resonance current ILr (t16) at t16. Since ILr is a positive / negative target from t10 to t13 and from t13 to t16, ILr (t13) = − ILr (t10). From t12 to t13, ILr may rise or fall depending on the operation mode, but ILr (t12) −ILr (t13) = ILr (t16) −ILr (t15), and the current fluctuation width is equal. In other words, since the current changed from t12 to t13 is offset with the current changed from t15 to t16, it can be seen that if the ILr waveform from t10 to t12 and the ILr waveform from t13 to t15 are cut out, a sine wave is obtained. . The frequency at this time is a resonance frequency Fo determined by Lr and Cr. When the switching frequency Fsw matches the stored resonance frequency Fo, the ILr waveform becomes continuous.

  From the above, the ideal on-timing of Vg5 and Vg8 is the timing at which Vg2 and Vg3 are turned off, and the ideal off-timing is after a half period (= 1) of the resonance period To (= 1 / Fo) from that timing. / (2 * Fo)). Similarly, Vg6 and Vg7 are the timings at which Vg1 and Vg4 are turned off, and the ideal off timing is a half cycle after the resonance period To (= 1 / Fo) from the timing (= 1 / (2 * Fo). ). These processes are performed by the secondary-side gate signal generator 15 that has obtained information from the primary-side gate signal generator 14 and the resonance frequency storage 13.

  As in this embodiment, switching the secondary-side semiconductor element 07 at an ideal on timing secures the maximum synchronous rectification period and is performed at an ideal off timing. Can prevent loss due to backflow, thus reducing loss. Therefore, it leads to high efficiency, and since the heat dissipation amount can be reduced, the heat dissipating member can be reduced, leading to cost reduction and miniaturization.

  In an actual machine, the ideal off-timing is not always To / 2 due to the influence of parasitic inductance or element recovery. Therefore, the secondary side gate signal generator 15 determines the obtained resonance frequency Fo and the design. If the resonance frequency of the actual device is higher than the resonance frequency of the design value, the off-timing of the secondary-side semiconductor element is corrected so as to be shorter and the actual frequency of the actual device is more than the resonance frequency of the design value. When the resonance frequency is low, the off-timing of the secondary-side semiconductor element can be corrected so as to be longer, thereby approaching a more ideal off-timing.

  Also, in the actual machine, if it deviates even slightly from the ideal off timing, for example, after t12 in FIG. 4, currents in negative directions flow in I5 and I8 and the current flows backward. And Vg8 off timing is earlier than t12, that is, the direction in which Fo is estimated to be high. That is, it is preferable to set the command value of the output voltage to be equal to or less than the transformer turns ratio of the amplitude of the pulse voltage.

  In the present embodiment, the resonance frequency Fo is acquired at the time of startup. However, it is not necessary to acquire at the time of startup, and the frequency acquired last time may be used.

  Furthermore, the deterioration of Cr can be confirmed and judged from the change in the used frequency, and when the resonance frequency becomes below a certain level, a signal for exchanging the capacitor unit or the resonance type power supply device 01 is output to the outside. By using it for maintenance, it contributes to longer life of the device.

  As described above, in this embodiment, in the resonance type power supply device, the output voltage with a gain characteristic of 1 is output at the time of starting the power supply, and the switching frequency at that time is obtained, thereby grasping the resonance frequency of the power supply main circuit. By reflecting the resonance frequency in the synchronous rectification signal of the secondary side semiconductor element, etc., a high-efficiency and small-sized resonance power supply device is realized.

  In other words, a resonance type power supply device that applies a pulsed voltage to a transformer and a resonant element by switching an input voltage by a primary side switching element, and controls an output voltage by switching by a secondary side switching element. The command value of the output voltage is set to be equal to or less than the transformer turns ratio of the amplitude of the pulsed voltage, the switching frequency of the set period is obtained, and the secondary side switching element of the secondary side switching element is obtained based on the obtained switching frequency. A structure having a control function for correcting the gate signal is adopted.

  Thereby, the resonant frequency can be easily grasped, and an inexpensive and highly efficient resonant power supply apparatus can be provided.

  FIG. 5 shows a circuit diagram of the resonance type power supply device 01 of the present embodiment. In this embodiment, the primary side semiconductor element 04 is composed of two semiconductor elements Q11 and Q12, the transformer 06 is composed of a center tap, and the secondary side semiconductor element 07 is also composed of two semiconductor elements Q13 and Q14. It is an example. The power supply control block 03 is omitted because it is the same as in FIG. Even when the circuit configuration is changed in this way, in the case of the resonant power supply device 01, the ideal off-timing of the secondary-side semiconductor element 07 depends on the resonant frequency Fo.

  Since the voltage level is Vin and −Vin in the first embodiment, the amplitude of the voltage is Vin. However, in this embodiment, the voltage applied to the transformer 06 and the resonance element 05 is 0. Since it is a pulse of Vin, the amplitude of the voltage is Vin / 2. Therefore, in the sampling mode, a value obtained by dividing a half value of Vin by the turn ratio is driven as a voltage command value.

  As described above, the voltage command value in the sampling mode is set to a value obtained by dividing the amplitude of the pulse voltage applied to the transformer 06 and the resonant element 05 by the turn ratio, thereby enabling various circuit methods such as a full bridge circuit and a half bridge circuit. Can also be supported.

  FIG. 6 shows a circuit diagram of the resonance type power supply device 01 of the present embodiment. In the present embodiment, the power control block 03 has a fixed frequency switching device 21. Other configurations are the same as those in FIG.

  In FIG. 6, in the sampling mode, the voltage command value is set to the turn ratio of the input voltage, and the fixed frequency switch 21 operates the primary-side gate signal generator 14 at the switching frequency Fsw calculated by the control amount calculator 12. The resonance frequency Fo is stored in the resonance frequency memory 13. In the normal operation mode, as in the first embodiment, the primary-side gate signal generator 14 generates a gate signal at the switching frequency Fsw calculated by the control amount calculator 12 according to the voltage command value Vref sent from the host controller. However, when the voltage of the input power supply Ein can be controlled, the resonant power supply device 01 can be driven with the switching frequency fixed to Fo acquired in the sampling mode.

  As a result, the resonance type power supply device 01 is in an ideal operating state and can realize high power conversion efficiency when operating at the resonance frequency Fo as the switching frequency Fsw. Since the input / output voltage ratio is fixed at a fixed frequency, it is necessary to control the input voltage when controlling the output voltage.

  As in the above-described embodiment, the resonant power supply apparatus has a sampling mode in which the output voltage command value is set to a value corresponding to the turn ratio of the amplitude of the voltage applied to the resonant element and the transformer and the resonant frequency is acquired. Can provide high-efficiency power conversion, and can provide a small and low-cost resonant power supply.

  Further, in all the embodiments, the example of the single operation has been described, but also in the case of the parallel operation, the resonance frequencies of all the resonance type power supply devices can be confirmed by sequentially checking the resonance frequencies one by one.

  In all the embodiments, the semiconductor element is indicated by the symbol of MOS-FET. However, the semiconductor element is not limited to the MOS-FET, and the present invention can be applied if the element is a switching element such as IGBT.

  Although the embodiments have been described above, the present invention is not limited to the above-described embodiments, and includes various modifications. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment.

  01: Resonant power supply device, 02: Power supply main circuit, 03: Power supply control block, 04: Primary side semiconductor element, 05: Resonant element, 06: Transformer, 07: Secondary side semiconductor element, 11: Switcher, 12 : Control amount calculator, 13: resonance frequency memory, 14: primary side gate signal generator, 15: secondary side gate signal generator, 21: fixed frequency switcher

Claims (8)

A resonance type power supply device that applies a pulsed voltage to a transformer and a resonance element by switching an input voltage by a primary side switching element, and controls an output voltage by switching by a secondary side switching element,
The command value of the output voltage is set to be equal to or less than the transformer turns ratio of the amplitude of the pulsed voltage, the switching frequency of the set period is acquired, and the 2 based on the acquired switching frequency A resonance type power supply apparatus having a control function of correcting a gate signal of a secondary switching element The resonant power supply device according to claim 1,
A resonance type power supply apparatus comprising: a storage unit that stores a switching frequency during a period in which a command value of the output voltage is set to be equal to or less than a ratio of the turn ratio of the transformer of the amplitude of the pulse voltage. The resonant power supply device according to claim 1,
A period in which the command value of the output voltage is set to be equal to or less than a ratio of the turn ratio of the transformer of the amplitude of the pulsed voltage, and a period from when the resonant power supply device is started to when a standby completion signal is output. A resonance type power supply apparatus characterized by: The resonant power supply device according to claim 1,
From the change in switching frequency during the period in which the command value of the output voltage is set to be equal to or less than the transformer turns ratio of the amplitude of the pulse voltage, the deterioration of the resonance capacitor constituting the resonance element is determined, A resonance type power supply apparatus having a function of outputting a signal relating to the deterioration to the outside of the resonance type power supply apparatus. The resonant power supply device according to claim 1,
A resonance type power supply apparatus, wherein a gate signal of a primary side switching element is generated and controlled based on the acquired switching frequency. A resonance type power supply device that applies a pulsed voltage to a transformer and a resonance element by switching an input voltage by a primary side switching element, and controls an output voltage by switching by a secondary side switching element,
2. A resonance type power supply apparatus according to claim 1, wherein there are two potentials at which the output voltage is stabilized from when the resonance type power supply apparatus is activated to when a standby completion signal is output. The resonant power supply device according to claim 1,
The control function is realized by a control IC. A resonance type power supply device that applies a pulsed voltage to a transformer and a resonance element by switching an input voltage by a primary side switching element, and controls an output voltage by switching by a secondary side switching element,
The command value of the output voltage is set to be equal to or less than the transformer turns ratio of the amplitude of the pulsed voltage, the switching frequency of the set period is obtained, and the half period or less of the obtained switching frequency A resonance type power supply apparatus, wherein the secondary side switching element is corrected by a gate signal having a pulse width of λ.

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