JP7243839B2 - Controller for DCDC converter - Google Patents

Description

The present disclosure relates to a control device and control method for an isolated resonant DCDC converter, and an isolated resonant DCDC converter.

Patent Literature 1 provides a control device for a power conversion circuit that can suppress a decrease in the effect of reducing loss that occurs in a rectifier when synchronous rectification is performed. The control device described in Patent Literature 1 includes a conversion circuit, a transformer, and a rectifying section, and detects reverse current flow from each output terminal side to the secondary coil side in the rectifying section. When a reverse current flow is detected, the control device turns off the fifth and sixth switches of the rectifying section, which are separate from the bridge-connected first to fourth switching elements, so that the reverse current flow does not occur. Correct the timing.

JP 2018-182882 A

In the case of digitally controlling the on/off of the switch on the secondary side by the synchronous rectification method in the isolated resonance type DCDC converter as shown in Patent Document 1, for example, current detection by a microcomputer, comparator state switching, register writing, PWM Signal generation takes time. As a result, there is a delay between the start of current flow on the secondary side and the detection of the start of current flow and turning on of the switch on the secondary side. Similarly, there is a delay between when the current in the secondary becomes zero or less and when the switch on the secondary is turned off. This is not preferable because it causes a difference in control timing between the primary side and the secondary side, causing a reverse current flow, resulting in a decrease in power conversion efficiency, heat generation, failure, and the like.

The present disclosure discloses a control device and control method for digitally controlling an isolated resonant DCDC converter, and an isolated resonant DCDC converter that generates less heat than the conventional technology.

A control device for an isolated resonance type DCDC converter according to one aspect of the present disclosure includes (A) a first current flowing between a first secondary winding and a load, and a second secondary winding and the load; and the second current flowing between and, and detect the first and second ON periods in which the first and second currents are respectively equal to or greater than a predetermined value in one cycle of the control operation, or ( B) a first voltage across a first sense resistor interposed between said first secondary winding and a load and a voltage across said second secondary winding and a load; A second voltage across a second detection resistor is detected, and first and second on-periods in which the first and second voltages are equal to or greater than a predetermined value, respectively, in one cycle of the control operation are detected. and an on-period detector that corresponds to the first on-period in at least one cycle immediately before the current cycle, or delays the start timing of the first on-period by a predetermined time and delays the end timing by a predetermined time. The first switch is turned on in a period within the current cycle corresponding to the advanced period, and the start timing of the second on period corresponds to or is set to the second on period of the at least one cycle. a switch control unit for turning on the second switch in a period within the current cycle corresponding to a period in which the end timing is delayed by a predetermined time and the end timing is advanced by a predetermined time.

According to the control device and the like of the present disclosure, it is possible to digitally control an isolated resonance type DCDC converter with less heat generation than in the prior art.

1 is a block diagram showing a configuration example of a resonant converter 1 according to Embodiment 1; FIG. 2 is a block diagram showing a detailed configuration example of a control unit 110 in FIG. 1; FIG. 2 is a timing chart showing operation waveforms of signals and the like in each part of the resonant converter 1 of FIG. 1; FIG. 10 is a block diagram showing a configuration example of a resonant converter 1A according to Embodiment 2; 5 is a block diagram showing a detailed configuration example of a control unit 110A of FIG. 4; FIG. 5 is a graph showing an example of a waveform of current Id1 when output current Iout is varied. FIG. 5 is a flow chart showing an example of a switch control operation by the controller 110A of FIG. 4; FIG. FIG. 11 is a block diagram showing a configuration example of a resonant converter 1B according to Embodiment 3; FIG. 11 is a block diagram showing a configuration example of a resonant converter 1C according to Embodiment 4; FIG. 11 is a block diagram showing a configuration example of a resonant converter 1D according to Embodiment 5; FIG. 12 is a block diagram showing the configuration of a resonant converter 1E according to Embodiment 6; 12 is a timing chart showing operation waveforms of signals and the like in each part of the resonant converter 1E of FIG. 11;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments according to the present invention will be described based on the drawings. However, each embodiment described below is merely an example of the present invention in every respect. It goes without saying that various modifications and variations can be made without departing from the scope of the invention. That is, in carrying out the present invention, a specific configuration according to the embodiment may be adopted as appropriate. In addition, in the attached drawings, the same reference numerals are given to the same or similar configurations.

(Embodiment 1)
FIG. 1 is a block diagram showing a configuration example of a resonant converter 1 according to Embodiment 1. As shown in FIG. In FIG. 1, the resonance type converter 1 converts a DC input voltage Vin input from a DC voltage source 120 into an AC voltage for resonance, and then rectifies and converts it again to a DC output voltage Vout. It is a DCDC converter.

1, the resonant converter 1 includes a full-bridge inverter 140, a transformer 100, a rectifying section 150, a load R1, a resistor R2, capacitors C1 and C2, current detecting sections 131 and 132, and a control section 110. Prepare. Full bridge inverter 140 includes switching elements G1 to G4. Transformer 100 includes primary winding 101 , first secondary winding 102 , and second secondary winding 103 . The rectifying unit 150 is an example of the “secondary conversion unit” of the present disclosure, and includes parallel-connected switch S1 and diode D1 and parallel-connected switch S2 and diode D2. The switches S1 and S2 are switch elements such as MOS transistors.

The DC voltage source 120 generates a DC voltage Vin and supplies it to the full bridge inverter 140 . Switching elements G 1 to G 4 of full bridge inverter 140 are on/off controlled by gate control signals Sg 1 and Sg 2 from control section 110 . At this time, the switching elements G1 and G4 and the switching elements G2 and G3 are controlled to be turned on periodically and alternately. As a result, the input voltage Vin from the DC voltage source 120 is switched and smoothed by the capacitor C1, and the AC voltage is output to the primary winding 101 of the transformer 100. FIG.

An excitation voltage is generated in the first and second secondary windings 102 and 103 by electromagnetic induction caused by an AC voltage flowing through the primary winding 101 . The excitation voltages from the first and second secondary windings 102, 103 are synchronously full-wave rectified by the switches S1, S2, smoothed by the resistor R2 and the capacitor C2, and the DC output voltage Vout is output.

Current detection unit 131 outputs a signal SId1 indicating current Id1 flowing from first secondary winding 102 to control unit 110, and current detection unit 132 indicates current Id2 flowing from second secondary winding 103. A signal SId2 is output to control unit 110 . The control unit 110 outputs a gate control signal Sg1 for controlling the switching elements G1 and G4, a gate control signal Sg2 for controlling the on/off of the switching elements G2 and G3, and switch control signals Ss1 and Ss2 for controlling the on/off of the switches S1 and S2. Output.

FIG. 2 is a block diagram showing a detailed configuration example of the control unit 110 in FIG. In FIG. 2 , the control section 110 includes a clock oscillator 111 , an ON period detection section 112 , a gate control section 113 and a switch control section 114 . The switch control unit 114 includes a storage unit 114m. The clock oscillator 111 outputs a clock signal Sclk to each of the on-period detection unit 112, the gate control unit 113, and the switch control unit 114. Periodic operations are performed that are common and in phase with the cycle time Tc. One cycle of this common periodic operation is hereinafter referred to as "one cycle".

In FIG. 2, based on the signals SId1 and SId2 from the current detectors 131 and 132, the on-period detector 112 detects a first on-period T1 during which the current Id1 flows and a period T1 during which the current Id2 flows in one cycle. A second on-period T2 is detected, and information on the first and second on-periods T1 and T2 is output to the switch control section 114 . The gate control unit 113 outputs a gate control signal Sg1 that is ON only during the first half of one cycle (a length of Tc/2 from the start of the cycle) and is OFF during the remaining period, and the first half of the cycle. It generates and outputs a gate control signal Sg2 which is off for only one minute and on for the rest of the period.

The switch control section 114 stores information on the first and second ON periods T1 and T2 output from the ON period detection section in the storage section 114m. In addition, the switch control unit 114 reads out the first on-period T1 in the immediately preceding cycle from the storage unit 114m, is on during the first on-period T1 in the immediately preceding cycle, and is off during the remaining period. A switch control signal Ss1 is generated as follows. Similarly, the switch control section 114 generates a switch control signal Ss2 that is ON during the second ON period T2 in the cycle immediately preceding one cycle and OFF during the other periods. The switch control section 114 outputs switch control signals Ss1 and Ss2 to the first and second switches S1 and S2, respectively.

FIG. 3 is a timing chart showing operation waveforms of signals and the like in each part of the resonant converter 1 of FIG. As shown in FIG. 3, the switch control signal Ss1 for controlling the switch S1 is turned on only during the period when the current Id1 is flowing, and is turned off during other periods. Similarly, the switch control signal Ss2 is turned on only during the period when the current Id2 is flowing, and is turned off during other periods.

As described above, the resonant converter 1 according to the first embodiment turns on the switches S1 and S2 during the first and second ON periods of the immediately preceding cycle. As a result, reverse current flow through the switches S1 and S2 can be prevented, and a decrease in power conversion efficiency and heat generation can be reduced. In addition, since there is time to generate the control signals Ss1 and Ss2 after detecting the first and second on-periods T1 and T2, it is possible to reduce the effect of delay in switch control caused by digital control. can.

(Embodiment 2)
FIG. 4 is a block diagram showing a configuration example of resonant converter 1A according to the second embodiment. 5 is a block diagram showing a detailed configuration example of the control section 110A of FIG. 4 and 5, the resonant converter 1A differs from the resonant converter 1 of FIG. 1 in the following points.
(1) A controller 110A is provided in place of the controller 110 .

(2) It further includes a voltage detection section 133 that detects the output voltage Vout and a current detection section 134 that detects the output current Iout.
(3) The control section 110A includes a switch control section 114A instead of the switch control section 114, and changes the control operation according to the value of the output current Iout.
The principle of operation when the output current Iout changes will be described below.

FIG. 6 is a graph showing an example of the waveform of the current Id1 when the output current Iout is varied. In FIG. 6, curve 410 shows the waveform when the output current Iout is large (eg, 175 A), curve 430 shows the waveform when the output current Iout is small (eg, 10 A), and curve 430 shows the waveform when the output current Iout is medium (eg, 10 A). For example, the waveform for 80 A) is shown in curve 420 . In FIG. 6, an on-period Th corresponding to the curve 410, an on-period Tm corresponding to the curve 420, an on-period Tl corresponding to the curve 430, and a period common to the three on-periods Th, Tm, and Tl. and a common ON period Tc.

As shown in FIG. 6, the first and second on-periods T1 and T2 detected for controlling the switches S1 and S2 in the first embodiment change depending on the value of the output current Iout. , the start and end of the first and second on-periods T1 and T2 are delayed. Therefore, when the output current Iout fluctuates greatly during one cycle, the control as in the first embodiment can effectively prevent the currents Id1 and Id2 from actually flowing in the forward direction and the switches S1 and S2 from turning on. The period during which the current is applied does not match, and a reverse current flow occurs.

FIG. 7 is a flow chart showing an example of the switch control operation by the control section 110A of FIG. In FIG. 7, the switch control operation includes steps S401-S407.

In FIG. 7, in step S401, the control unit 110A turns on the switches S1 and S2 according to the first and second ON periods T1 and T2 of the immediately preceding cycle, as in the first embodiment. After step S401, the switch control operation proceeds to step S402.

In step S402, control unit 110A determines whether or not output current Iout fluctuates by a difference greater than a predetermined value during one cycle. If the output current Iout is fluctuating, the switch control operation proceeds to step S403. If not, the switch control operation repeats step S401. Therefore, if the variation of the output current Iout is sufficiently small, the switches are controlled in the same manner as in the first embodiment.

In step S403, control unit 110A turns on switches S1 and S2 according to common ON period Tc in FIG. As described above, when the output current Iout fluctuates greatly, the first ON period T1 also fluctuates. Here, in the common ON period Tc of FIG. 6, the current Id1 flows regardless of the value of the output current Iout. Therefore, even when the output current Iout fluctuates greatly, the reverse current can be prevented by turning on the switch S1 only during the common ON period Pc. After step S403, the switch control operation proceeds to step S404.

In step S404, control unit 110A determines whether or not output current Iout is smaller than predetermined threshold value Ith, that is, whether or not Iout<Ith is established. If it is established, the switch control operation proceeds to step S405, and if not established, the switch control operation proceeds to step S406.

At step S405, the controller 110A keeps the switches S1 and S2 off for one cycle. That is, the isolated resonant converter is operated by the asynchronous rectification method. If the output current Iout is sufficiently small, it is difficult to detect variations in the output current Iout. Also, since the values of the currents Id1 and Id2 are small, power consumption by the resistances of the diodes D1 and D2 is small. Therefore, even if the switches S1 and S2 are always turned off and the asynchronous rectification is performed, an effect equivalent to that of the synchronous rectification can be obtained. After step S405 ends, the switch control operation returns to step S404. Therefore, as long as the output voltage Iout is smaller than the predetermined threshold value Ith, the controller 110A repeats step S405.

In step S406, control unit 110A determines whether or not output current Iout fluctuates for a period of a predetermined number of cycles. If the output current Iout is fluctuating, the switch control operation returns to step S404. If not, the switch control operation proceeds to step S407. In step S407, the control unit 110A turns on the switches S1 and S2 during the first and second ON periods one cycle before, in the same manner as in step S401, for a period of a predetermined number of cycles. After the predetermined number of cycles has elapsed, the switch control operation returns to step S401. In other words, in step S407, control unit 110A performs the same operation as in step S401 without monitoring fluctuations in output current Iout until output current Iout stabilizes.

As described above, resonant converter 1A according to the second embodiment changes the switch control operation according to the value of output current Iout. As a result, even when the output current Iout changes greatly, it is possible to prevent the current from flowing back through the switches S1 and S2, thereby reducing power conversion efficiency and heat generation.

Note that the monitored value to be monitored for changing the switch control operation is not limited to the output current Iout. At least one of the measured temperatures tmp1 and tmp2 of the switches S1 and S2 may be used as a monitoring value and used as a reference for changing the switch control operation.

(Embodiment 3)
FIG. 8 is a block diagram showing a configuration example of a resonant converter 1B according to the third embodiment. In FIG. 8, resonant converter 1B differs from resonant converter 1 of FIG. 1 in the following points.
(1) Instead of the current detection units 131 and 132, the detection resistors Rd1 and Rd2 inserted at the positions of the current detection units 131 and 132, respectively, and the detection voltages Vd1 and Vd2 across the detection resistors Rd1 and Rd2 are detected. It includes voltage detection units 131B and 132B that output signals SVd1 and SVd2 to the control unit 110B.
(2) The control unit 110B detects the ON periods T1 and T2 based on the voltage signals SVd1 and SVd2 instead of the current signals SId1 and SId2.

Detection resistors Rd1 and Rd2 generate detection voltages Vd1 and Vd2 by currents Id1 and Id2 flowing through them, respectively. Therefore, by setting the periods during which the detected voltages Vd1 and Vd2 corresponding to the currents Id1 and Id2, respectively, are equal to or greater than a predetermined value as the on-periods T1 and T2, the first and second on-periods T1 and T2 similar to those of the first embodiment can be obtained. T2 can be detected.

(Embodiment 4)
FIG. 9 is a block diagram showing a configuration example of a resonant converter 1C according to the fourth embodiment. The resonant converter 1C differs from the resonant converter 1A of FIG. 4 in the following points.
(1) Instead of the current detection units 131 and 132, the detection resistors Rd1 and Rd2 inserted at the positions of the current detection units 131 and 132, respectively, and the detection voltages Vd1 and Vd2 across the detection resistors Rd1 and Rd2 are detected. It includes voltage detection units 131B and 132B that output signals SVd1 and SVd2 to the control unit 110C.
(2) The control unit 110C detects the ON periods T1 and T2 based on the voltage signals SVd1 and SVd2 instead of the current signals SId1 and SId2.
Thereby, the detection voltages Vd1 and Vd2 corresponding to the currents Id1 and Id2 can be detected, and the first and second on-periods T1 and T2 can be detected as in the third embodiment.

(Embodiment 5)
FIG. 10 is a block diagram showing a configuration example of a resonant converter 1D according to the fifth embodiment. In FIG. 10, resonant converter 1D differs from resonant converter 1 in FIG. 1 in the following points.
(1) Switches S1D and S2D have a predetermined on-loss resistance when turned on.
(2) Instead of the current detectors 131 and 132, it includes voltage detectors 131D and 132D that measure voltages Vd1 and Vd2 across the switches S1D and S2D and output signals SVd1 and SVd2 to the controller 110D.
(3) The control unit 110D detects the ON periods T1 and T2 based on the voltage signals SVd1 and SVd2 instead of the current signals SId1 and SId2.

In FIG. 10, when the on-loss resistance of the switches S1D and S2D is not negligible, the voltages across the switches S1D and S2D are measured to detect the currents Id1 and Id2 in the same manner as in the third and fourth embodiments, ON periods T1 and T2 can be detected.

(Embodiment 6)
FIG. 11 is a block diagram showing the configuration of resonant converter 1E according to the sixth embodiment. The resonant converter 1E of FIG. 11 differs from the resonant converter 1 of FIG. 1 in the following points.
(1) Voltage detectors 131D and 132D are provided in place of the current detectors 131 and 132 .
(2) A controller 110</b>E is provided instead of the controller 110 .
(3) The controller 110E outputs control signals Ss1E and Ss2E to the switches S1 and S2.

FIG. 12 is a timing chart showing operation waveforms of signals and the like in each part of the resonant converter 1E of FIG. In FIG. 12, the ON period T1p indicates the ON period in the immediately preceding cycle, and the ON period T1m indicates the period during which the switch S1 is controlled to be ON in the current cycle. Also, the ON period T2p indicates the ON period in the previous cycle, and the ON period T2m indicates the period during which the switch S2 is controlled to be ON in the current cycle. Here, the periods Tdon and Tdoff are periods each having a predetermined minute time (<<T1p, T2p). As shown in FIG. 12, control unit 110E sets periods T1m and T2m set so that the start timing is delayed by period Tdon and the end timing is advanced by period Tdoff relative to ON periods T1p and T1p in the immediately preceding cycle. , the switches S1 and S2 are turned on. The reason why the end timing is advanced is to prevent reverse current flow.

Here, the switches S1 and S2 are not turned on during the periods Tdon and Tdoff. When voltages similar to those in FIG. 3 are applied from secondary winding 102 to switches S1 and S2 in periods Tdon and Tdoff, currents Id1 and Id2 flow through diodes D1 and D2, respectively. Therefore, by measuring the voltages across the switches S1 and S2, that is, the voltages across the diodes D1 and D2, for example, using the voltage detection units 131D and 132D in FIG. The start timing and end timing of T2 can be substantially detected.

As described above, the switches S1 and S2 are turned on in a period in which the start timings of the on-periods T1p and T2p of the immediately preceding cycle are delayed by the period Tdon and the end timings are advanced by the period Tdoff, and both ends of the diodes D1 and D2 are turned on. By measuring the voltage, the start and end timings of the on-periods T1 and T2 can be detected, and the on-periods T1 and T2 can be substantially detected.

(Other embodiments)
In Embodiments 1 to 6, control units 110 and 110A turn on switches S1 and S2 based on the first and second on periods in one cycle immediately preceding the current cycle. However, this is not limited to one cycle immediately preceding the current cycle, but may be the on-periods T1, T2 in at least one cycle up to immediately preceding the current cycle. For example, the switches S1 and S2 are controlled to be turned on during the ON period of the cycle two cycles before the current cycle, or during the average of the ON periods T1 and T2 one cycle before and the ON periods T1 and T2 two cycles before.

In addition, in Embodiments 1 to 6, the full-bridge inverter 140 is used as the primary-side converter that converts the DC voltage to the AC voltage. part may be used.

The control device and the like of the present disclosure are applicable to digital control and synchronous rectification type DCDC conversion devices.

1, 1A to 1E resonant converter 100 transformer 101 primary windings 102, 103 secondary windings 110, 110A to 110E control unit 111 clock oscillator 112 on-period detection unit 113 gate control units 114, 114A switch control unit 114m storage unit 120 DC voltage sources 131, 132, 134 Current detectors 131B, 131D, 131E, 132B, 132D, 132E Voltage detectors 133, 137 Voltage detectors 135, 136 Temperature detector 140 Full-bridge inverter 150 Rectifiers C1, C2 Capacitor D1, D2 Diode R1 Load R2 Resistors Rd1, Rd2 Detection resistors S1, S1D, S2, S2D Switch

Claims (7)

a primary conversion unit that converts an input DC voltage into an AC voltage;
a transformer having a primary winding and first and second secondary windings for converting the alternating voltage into two alternating voltages;
A secondary side having a first switch connected between said first secondary winding and a load and a second switch connected between said second secondary winding and a load A control device for controlling an isolated resonance type DCDC conversion device comprising a conversion unit,
(A) detecting a first current flowing between the first secondary winding and the load and a second current flowing between the second secondary winding and the load, and performing control operation; or (B) between the first secondary winding and the load sense a first voltage across a first sense resistor inserted between the second secondary winding and a load, and a second voltage across a second sense resistor interposed between the second secondary winding and the load. and an on-period detector for detecting first and second on-periods in which the first and second voltages are equal to or greater than a predetermined value, respectively, in one cycle of the control operation;
It corresponds to the first ON period in at least one cycle up to immediately before the current cycle, or corresponds to a period in which the start timing of the first ON period is delayed by a predetermined time and the end timing is advanced by a predetermined time. during a period within the current cycle , turning on the first switch, corresponding to the second on period of the at least one cycle, or delaying the start timing of the second on period by a predetermined time; a switch control unit that turns on the second switch in a period within the current cycle corresponding to a period in which the end timing is advanced by a predetermined time;
A control device for an isolated resonance type DCDC converter. the first sense resistor is the on resistance of the first switch and the second sense resistor is the on resistance of the second switch;
A control device according to claim 1 . at least one cycle immediately preceding the current cycle is the one cycle immediately preceding the current cycle;
3. A control device according to claim 1 or 2. The switch control unit monitors for one cycle based on at least one monitored value of an input voltage, an output current, an output voltage, and temperatures of the first and second switches of the isolated resonance type DCDC converter. turning on the first and second switches during a predetermined common ON period during which the first and second currents flow regardless of the monitored value, if the variation in value is greater than a predetermined value;
A control device according to any one of claims 1 to 3. a first diode connected in parallel with the first switch;
a second diode connected in parallel with the second switch;
always turning off the first and second switches regardless of the monitored value when the monitored value is less than a predetermined threshold value in the immediately preceding cycle;
5. A control device according to claim 4. An isolated resonance type DCDC converter comprising the control device according to any one of claims 1 to 5. a primary conversion unit that converts an input DC voltage into an AC voltage;
a transformer having a primary winding and first and second secondary windings for converting the alternating voltage into two alternating voltages;
A secondary side having a first switch connected between said first secondary winding and a load and a second switch connected between said second secondary winding and a load In a control device control method for controlling an isolated resonance type DCDC conversion device comprising a conversion unit,
The controller controls (A) a first current flowing between the first secondary winding and a load and a second current flowing between the second secondary winding and a load; detecting first and second ON periods in which the first and second currents are equal to or greater than a predetermined value, respectively, in one cycle of the control operation; or (B) the first secondary winding a first voltage across a first sense resistor interposed between the second secondary winding and a load; and a second voltage across a second sense resistor interposed between the second secondary winding and the load. and detecting the first and second on-periods in which the first and second voltages are equal to or higher than a predetermined value, respectively, in one cycle of the control operation;
The control device corresponds to the first ON period in at least one cycle immediately before the current cycle, or delays the start timing of the first ON period by a predetermined time and advances the end timing by a predetermined time. turning on the first switch in a period within the current cycle corresponding to the period corresponding to the period corresponding to the second on period of the at least one cycle, or setting the start timing of the second on period and turning on the second switch in a period within the current cycle corresponding to a period in which the end timing is delayed by a predetermined time and the end timing is advanced by a predetermined time.
A control method for an insulated resonance type DCDC converter.

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