JP6731076B2 - Dead time setting method of DCDC converter circuit - Google Patents

Description

The present invention relates to a dead time setting method for a DCDC converter circuit, and more particularly to a dead time setting method for a DCDC converter circuit used in a vehicle power supply.

A DCDC converter circuit used for a vehicle power supply is configured by a plurality of switching elements to form a full bridge circuit, and by controlling the full bridge circuit, the voltage is stepped up or down via a transformer.

The full bridge circuit has a series circuit composed of an upper arm and a lower arm (see Patent Document 1). In order to prevent a short-circuit current from flowing between the upper arm and the lower arm, it is necessary to set a dead time which is a simultaneous off period of the upper arm and the lower arm.

A loss of the switching operation of the switching element may occur during the dead time. The DCDC converter circuit is required to reduce the loss of switching operation while suppressing an increase in the resonance inductance connected between the full bridge circuit and the transformer.

JP, 2016-116440, A

Therefore, the problem to be solved by the present invention is to suppress the loss of the switching operation while suppressing the increase of the resonance inductance.

A dead time setting method for a DCDC converter circuit according to the present invention is a dead time setting method for a DCDC converter circuit including a resonance coil and a transformer connected to a full bridge circuit, wherein the dead time is the inductance of the resonance coil. The full bridge circuit is calculated based on the leakage inductance of the transformer, and the full bridge circuit includes a first upper arm including a first switching element and a first capacitance component connected in parallel with the first switching element; A first lower arm configured by a switching element and a second capacitance component connected in parallel with the second switching element and connected in series with the first upper arm; a third switching element and the third switching element; A second upper arm constituted by a third capacitance component connected in parallel, a fourth switching element and a fourth capacitance component connected in parallel with the fourth switching element, and the second upper arm A second lower arm connected in series, wherein the resonance coil is provided in a wiring connecting the connection point between the first upper arm and the first lower arm and the transformer, and the start time of the dead time is , The reversal of the circulating current flowing through the first upper arm, the first lower arm, the resonance coil, and the transformer is completed later than the timing at which the charging of the first capacitance component and the discharging of the second capacitance component are completed. It is set earlier than the timing and based on the parasitic resistance component of the full bridge circuit, the resistance value of the gate resistance inserted in the full bridge circuit, and the input capacitance when the applied voltage of each switching element is 0V.

According to the present invention, loss of switching operation can be reduced while suppressing an increase in resonance inductance.

3 is a block diagram of an internal configuration of an insulation type DCDC converter 200. FIG. FIG. 3 is a schematic block diagram showing connection of electrification components in vehicle 100. The switching timings of the switching elements H1 to H4 are shown. The operation of the primary side circuit of the insulation type DCDC converter 200 in the period (1) of FIG. The operation of the primary side circuit of the insulation type DCDC converter 200 in the period (2) of FIG. 3A is shown. As a comparative example, the operation of the primary side circuit of the insulation type DCDC converter 200 when ZVS fails will be shown. Circuit operations in periods (1), (2), and (3) of FIG. 3A are shown. It is a graph which shows the effect in this embodiment.

An embodiment according to the present invention will be described with reference to FIGS. 1 to 6.

FIG. 2 is a schematic block diagram showing connection of electrification components in vehicle 100.

Vehicle 100 is an electric vehicle or a hybrid vehicle, and has a main motor 101, an inverter 102, a high-voltage main battery 201, a low-voltage auxiliary battery 202, an insulating DCDC converter 200, and an auxiliary device 103.

The main motor 101 is a traveling motor of the vehicle 100 and is driven by the AC power output from the inverter 102.

The inverter 102 is a power conversion device that converts the DC power of the high-voltage main engine battery 201 into AC power.

The auxiliary machine 103 is an electronic device that operates by using the DC power of the low-voltage auxiliary machine battery 202, and is a general term for ECUs, headlights, etc., although not shown.

FIG. 1 is a block diagram of the internal configuration of the insulation type DCDC converter 200.

The insulation type DCDC converter 200 is a power conversion device between the high voltage main battery 201 and the low voltage auxiliary battery 202.

The high-voltage main engine battery 201 is a high-voltage battery configured by connecting a plurality of lithium-ion batteries and the like. The low voltage auxiliary battery 202 is a low voltage battery such as a lead battery.

The full bridge circuit 203 is a circuit for converting electric power using four switching elements, has switching elements H1 to H4, and an arm is formed by the switching element H1 and the switching element H2 connected in series. The switching element H3 and the switching element H4 connected to the arm are connected in parallel. The switching elements H1 to H4 are semiconductor switches, and MOSFETs or the like are used.

The capacitance components H1C to H4C are capacitance components that appear to be connected in parallel to the switching elements H1 to H4 in terms of an equivalent circuit, and are composed of a parasitic capacitance of the switching element and a capacitor connected in parallel.

The resonance inductor 204 is an inductance component for flowing a circulating current through the full bridge circuit 203. The resonance inductor 204 may be the leakage inductance of the transformer 205 and the inductance component of the resonance coil, or may be only the leakage inductance of the transformer 205. The resonance inductor 204 is mounted between the transformer 205 and the connection point of the switching elements H1 and H2.

The resonance inductor 204 stores the exciting current when the high voltage main battery 201 excites the transformer 205 as energy.

The circulating current, which will be described later with reference to FIG. 3, is a current flowing through the resonance inductor 204, and flows when the switching elements H1 to H4 in the full bridge circuit 203 are switched, that is, when the high-voltage main battery 201 does not excite the transformer 205.

The transformer 205 has a primary winding, a secondary winding, and a core, and converts power according to the turn ratio of the primary winding and the secondary winding. The primary winding is connected to the full bridge circuit 203, and the secondary winding is connected to the secondary side rectification circuit 206.

The secondary side rectifier circuit 206 is connected to the secondary winding of the transformer 205, rectifies the power output by the transformer 205, and outputs the rectified power to the low-voltage auxiliary battery 202. Although not shown, it has a choke coil, a switching element, a diode, and the like.

The control signal generator 207 receives the output voltage and output current of the secondary side rectifier circuit 206, calculates the switching timings of the switching elements H1 to H4, and outputs the respective control signals. A DSP or a microcomputer is used for timing calculation and signal generation.

FIG. 3 shows the operation of the primary side circuit of the insulation type DCDC converter 200 when ZVS is successful. ZVS is a technique for reducing loss to approximately 0 [W] by switching in a state where the voltage across the switching elements H1 to H4 is approximately 0 [V]. The loss of the switching element is obtained by the product of the voltage across the switching element and the current flowing through the switching element, and ZVS is established by setting the voltage across the switching element to approximately 0 [V].

FIG. 3A shows switching timings of the switching elements H1 to H4. However, not all operations of the isolated DCDC converter 200 are shown.

The control signal H1gate is a control signal for the switching element H1 and is a signal output by the control signal generation unit 207. The switching element H1 shifts to the ON state with a slight time difference when the control signal H1gate is turned on, and similarly shifts to the OFF state when the control signal H1gate is turned off.

The control signal H2gate is a control signal of the switching element H2 like the control signal H1gate. The control signal H3gate is a control signal of the switching element H3 like the control signal H1gate. The control signal H4gate, like the control signal H1gate, is a control signal for the switching element H4.

During the period (1) of FIG. 3A, the switching element H1 and the switching element H3 are in the ON state, and the switching element H2 and the switching element H4 are in the OFF state.

FIG. 3B shows the operation of the primary side circuit of the insulation type DCDC converter 200 in the period (1) of FIG.

The circulating current 302b is a current flowing through the resonance inductor 204, and the current path is indicated by a thick arrow in FIG. 3B, and returns to the resonance inductor 204 via the transformer 205, the switching element H3, and the switching element H1. ..

A period (2) of FIG. 3A is a state in which the switching element H1 is turned off from the state of the period (1) of FIG. 3A, and the switching element H1, the switching element H2, and the switching element H4 are in an off state, The switching element H3 is in the on state.

FIG. 3C shows the operation of the primary side circuit of the insulation type DCDC converter 200 in the period (2) of FIG.

The circulating current 302c is obtained by changing the current path of the circulating current 302b, and is indicated by a thick arrow in FIG.

The circulating current 302c is similar to the circulating current 302b up to the point where it flows through the transformer 205 and the switching element H3, but since the switching element H1 is in the OFF state, it cannot flow through the switching element H1 and the high voltage main battery 201 , And returns to the resonance inductor 204 via the body diode of the switching element H2.

Since the switching element H1 is turned off, a voltage is generated across the capacitive component H1C, and the capacitive component H1C is charged by the circulating current 302c.

Since the switching element H1 is turned off, the capacitance component H2C is discharged because the voltage across it decreases. After the discharge is completed, the body diode of the switching element H2 becomes conductive and the circulating current 302c flows.

The circulating current 302c gradually decreases due to charging of the capacitive component H1C, loss of the wiring path, and the like.

A period (3) of FIG. 3A is a state in which the switching element H2 is turned on from the state of the period (2) of FIG. 3A, the switching element H2 and the switching element H3 are in the ON state, the switching element H1, The switching element H4 is in the off state.

The voltage across the switching element H2 is the switching element in the state where the capacitive component H2C is discharged in the period (2) of FIG. 3A, that is, when the body diode of the switching element H2 is conductive and the circulating current 302c is flowing. It is only the voltage drop of the body diode of H2, and can be regarded as almost 0 [V].

ZVS in the switching element H2 is established by turning on when the voltage across the switching element H2 is approximately 0 [V].

FIG. 4 shows a primary side circuit operation of the insulation type DCDC converter 200 at the time of ZVS failure as a comparative example.

As described above, the circulating current 302c is a circulating current when ZVS is established in the switching element H2, and is indicated by a dotted arrow in FIG. The circulating current 302c gradually decreases and eventually stops flowing.

The resonance inductor 204 receives a reverse voltage because the circulating current 302c stops flowing. The circulating current 401 is a current path of the circulating current when a reverse voltage is applied to the resonance inductor 204, and is indicated by a thick arrow in FIG.

The capacitive component H1C is discharged to secure the current path of the circulating current 401. The capacitive component H2C is charged by the voltage generated at both ends.

ZVS in the switching element H2 becomes ineffective by being turned on when the capacitance component H2C is charged and the voltage across the switching element is not 0 [V].

In order to establish ZVS, it is necessary to turn on the switching element H2 while the circulating current 302c is flowing, and the period (2) in FIG. 3A, that is, the switching element H1 is turned off and then the switching element H2 is turned on. You can adjust the time until it turns on.

The period (2) in FIG. 3A is called dead time. The dead time is a period provided to prevent a P/N short circuit of the high-voltage main engine battery 201, that is, to prevent the switching elements H1 and H2 from being simultaneously turned on.

The dead time should be set long in order to avoid a P/N short circuit in consideration of circuit safety. On the other hand, the dead time should be set short because it is necessary to satisfy ZVS and the switching element H2 must be turned on while the circulating current 302c is flowing, considering a low loss circuit.

In this embodiment,
The present invention proposes a means for setting a dead time as long as possible within the dead time range in which ZVS is established.

FIG. 5 shows the circuit operation in the periods (1), (2), and (3) of FIG. In FIG. 5, the horizontal axis is time, the change points of the switching element H1 and the switching element H2 are shown as times t0, t1, t2, t3, t4, t5, and t6, and the change points of the resonant inductor 204 are ta, tb, and tc. Indicate.

In FIG. 5, the circuit operation diagram on the upper left shows the operation of the switching element H1.

The time t0 is the time when the control signal generation unit 207 outputs the OFF command for the control signal H1gate of the switching element H1.

The switching element H1 receives the control signal H1gate at time t0. Strictly speaking, there is a time lag from when the control signal H1gate is output from the control signal generation unit 207 to when it is transmitted to the switching element H1, but it is negligible here and can be ignored here.

The gate signal H1Vgs starts to drop in voltage after receiving the control signal H1gate.

Time t1 is the time when the gate signal H1Vgs drops to the plateau voltage.

Since the switching element H1 has not been turned off at time t1, the circulating current flows through the circulating current 302b.

The elapsed time from time t0 to time t1 is displayed as period t01, and the elapsed time from time t1 to time t2 is also displayed as period t12 in the same manner.

The period t01 can be represented by (Equation 1).

Rg is a parasitic resistance component such as a wiring pattern. Although not shown, Rg_app_off is the resistance value of the gate resistance inserted in the circuit. The gate resistance may use different constants when the switch is off and when it is on.

Ciss@Vds=0 is the input capacitance of the switching element when the applied voltage is 0 V, and is the capacitance that depends on the switching element.

Vgs_app represents the voltage applied to the gate terminal of the switching element. Vgp is a plateau voltage and depends on the switching element.

Time t2 is the time when the discharge of the mirror capacitance is completed, and the switching element H1 is turned off from here.

The period t12 can be represented by (Equation 2).

The gate signal H1Vgs continues to maintain the plateau voltage during the period t12, and starts decreasing from the time t2.

The drain current H1Ids is a current flowing between the drain and the source of the switching element H1 and starts decreasing at time t2.

Time t3 is a time when the switching element H1 is substantially turned off.

The period t23 can be represented by (Equation 3).

Vtk indicates the threshold voltage of the switching element.

The gate signal H1Vgs continues to decrease during the period t23, becomes the threshold voltage at time t3, and continues to decrease thereafter.

The drain current H1Ids starts decreasing at time t2 and becomes almost 0 [A] at time t3. The switching element H1 is turned off at the time t3 when the drain current H1Ids becomes 0 [A].

In FIG. 5, the circuit operation diagram on the upper right shows the operation of the switching element H2.

The time t4 is the time when the ON signal of the control signal H2gate of the switching element H2 is output from the control signal generation unit 207.

The switching element H2 receives the control signal H2gate at time t4. Strictly speaking, there is a time lag from when the control signal H2gate is output from the control signal generation unit 207 to when it is transmitted to the switching element H2, but it is negligible here and can be ignored here. The gate signal H2Vgs starts to increase in voltage after receiving the control signal H2gate.

Time t5 is the time when the gate signal H2Vgs rises to the threshold voltage.

The switching element H2 starts to turn on at time t5. The drain current H2Ids starts rising at time t5.

The period t45 can be expressed by (Equation 4).

Although not shown, Rg_app_on indicates the resistance value of the gate resistance inserted in the circuit.

Time t6 is the time when the gate signal H2Vgs rises to the plateau voltage. The switching element H2 is substantially turned on at time t6.

The period t56 can be expressed by (Equation 5).

In FIG. 5, the lower circuit operation diagram shows the operation of the resonant inductor 204 and the capacitive component H2_C.

The voltage VH2C indicates the voltage across the capacitive component H2C.

With respect to the capacitance component H2C shown in FIG. 1, the switching element H1 is turned off at the time t3, so that discharge is started and the voltage across both ends decreases.

In the capacitance component H1C shown in FIG. 1, since the switching element H1 is turned off at the time t3, a voltage is generated at both ends and charging is started by the circulating current.

The circulating current ILr indicates a current flowing through the resonance inductor 204, that is, a circulating current, and starts to gradually decrease at time t3 in order to charge the capacitance component H1C.

Time ta indicates the time when charging of the capacitive component H1C and discharging of the capacitive component H2C are completed.

The voltage VH2C becomes almost 0 [V] because the discharge of the capacitive component H2C is completed.

The period t3a is an elapsed time from the start of discharging the capacitive component H2C and the charging of the capacitive component H1C at time t3 to the completion of the discharging of the capacitive component H2C and charging of the capacitive component H1C at time ta. , (Equation 6).

C is the capacitance of the capacitance component H2C and the capacitance component H1C. Here, the capacitances of the capacitance component H2C and the capacitance component H1C are treated as the same capacitance, but they may be different.

Vin is the voltage value of the high voltage main battery 201 and is the input voltage of the insulation type DCDC converter 200.

ILr(0) is an initial value of the circulating current and depends on the output current of the insulation type DCDC converter 200.

Time tb indicates the time when the reversal of circulating current ILr is completed. The circulating current ILr decreases from the time ta as a function of the input voltage Vin and the inductance of the resonant inductor 204, starts the inversion at the center of the period tab, and completes the inversion at the time tb.

The voltage VH2C can be regarded as almost 0 [V] from the time ta when the discharge is completed to the time tb.

The period tab is an elapsed time from the completion of the charging of the capacitive component H1C and the discharging of the capacitive component H2C at the time ta to the completion of the reversal of the circulating current ILr at the time tb, which can be expressed by (Equation 7). I can.

Lr is the inductance of the resonance inductor 204. The time tc indicates the time when the discharging of the capacitive component H1C and the charging of the capacitive component H2C are completed.

The capacitive component H1C starts discharging after the inversion of the circulating current ILr is completed at time tb and is completed at time tc.

The capacitive component H2C starts charging after the inversion of the circulating current ILr is completed at time tb, and is completed charging at time tc.

The period tbc indicates an elapsed time from the completion of the inversion of the circulating current ILr at the time tb to the completion of the discharging of the capacitive component H1C and the charging of the capacitive component H2C at the time tc.

ZVS in the switching element H2 is established when the voltage across the switching element H2 is approximately 0 [V], that is, when the voltage across the capacitive component H2C is 0 [V].

The voltage across the capacitive component H2C becomes almost 0 [V] at time ta, and starts rising again at time tb. That is, it is almost 0 [V] in the period tab.

The ZVS in the switching element H2 is sufficient if the switching element H2 is substantially in the ON state within the period tab, and is satisfied if the time t6 is within the period tab, that is, (Equation 8) may be satisfied.

The period t0a is the total of the period t01, the period t12, the period t23, and the period t3a, and can be represented by (Expression 9).

The period t06 is the total of the period t04, the period t45, and the period t56, and can be represented by (Expression 10).

The period t0b is the total of the period t0a and the period tab, and can be expressed by (Equation 11).

The period t04 is an elapsed time from when the OFF command of the control signal H1gate of the switching element H1 is output from the control signal generation unit 207 to when the ON command of the control signal H2gate of the switching element H2 is output from the control signal generation unit 207. Which is represented by the period (2) in FIG. 3A and is called dead time.

The optimum dead time t04 can be obtained by using (Equation 9), (Equation 10), and (Equation 11) and setting the time t4 that satisfies (Equation 8).

FIG. 6 is a graph showing the effect of this embodiment. In FIG. 6, the vertical axis represents the loss [W] when the switching element is turned on, and the horizontal axis represents the load current [A] of the isolated DCDC converter 200.

A loss curve 601 shows the loss when the dead time is set to 200 [ns] as a comparative example. The loss curve 602 shows the loss when the dead time is set to 150 [ns] according to this embodiment.

The loss curve 602 shows that the loss is smaller than that of the loss curve 601 over the entire load region shown in the figure. The loss curve 602 is expected to increase in a light load region (not shown), but the output specifications of the insulation type DCDC converter 200 include medium load (about 100 [A]) to heavy load (200 [A] or more). ) Is the result of optimization so that the loss is minimized, and it is also possible to optimize the light load region to low loss.

100... Vehicle, 101... Main machine motor, 102... Inverter, 103... Auxiliary machine, 200... Insulation type DCDC converter, 201... High voltage main machine battery, 202... Low voltage auxiliary machine battery, 203... Full bridge circuit, 204... Resonance inductor, 205 ... Transformer, 206 ... Secondary side rectifier circuit, 207 ... Control signal generation unit, 302b ... Circulating current, 302c ... Circulating current, 401 ... Circulating current, 601 ... Loss curve, 602 ... Loss curve, H1 ... Switching element, H2 ... switching element, H3... switching element, H4... switching element, H1C... capacitive component, H2C... capacitive component, H3C... capacitive component, H4C... capacitive component, H1gate... control signal, H2gate... control signal, H1Ids... drain current, H2Ids. ... drain current, H3gate... control signal, H4gate... control signal, H1Vgs... gate signal, H2Vgs... gate signal, ILr... circulating current

Claims (1)

A dead time setting method for a DCDC converter circuit comprising a resonance coil and a transformer connected to a full bridge circuit, comprising:
The dead time is calculated based on the inductance of the resonance coil and the leakage inductance of the transformer ,
The full bridge circuit is
A first upper arm composed of a first switching element and a first capacitance component connected in parallel with the first switching element;
A first lower arm configured by a second switching element and a second capacitance component connected in parallel with the second switching element and connected in series with the first upper arm;
A second upper arm composed of a third switching element and a third capacitance component connected in parallel with the third switching element;
A fourth switching element and a second lower arm configured by a fourth capacitance component connected in parallel with the fourth switching element and connected in series with the second upper arm;
The resonance coil is provided in a wiring that connects the connection point between the first upper arm and the first lower arm and the transformer,
The start of the dead time is later than the timing at which the charging of the first capacitive component and the discharging of the second capacitive component are completed, and the circulation through the first upper arm, the first lower arm, the resonance coil, and the transformer. Based on the parasitic resistance component of the full bridge circuit, the resistance value of the gate resistance inserted in the full bridge circuit, and the input capacitance when the applied voltage of each switching element is 0 V, earlier than the timing at which the reversal of the current is completed. A dead time setting method for a DCDC converter circuit to be set.

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