A unified control circuit and control method based on a DC-DC converter

Abstract

The present invention relates to a unified control circuit and control method based on a DC-DC converter. Two ends of a low-voltage side of the DC-DC converter are respectively connected to a high-voltage battery pack, the high-voltage side of the DC-DC converter is connected to a DC bus, the DC bus is connected to a bus capacitor, the DC side of a TM motor controller and the DC side of a GM motor controller are both connected to the DC bus, the AC side of the TM motor controller is connected to a TM motor, the AC side of the GM motor controller is connected to a GM motor, and the other end of the GM motor is connected to an engine; the DC bus is connected to a voltage sampling unit, the output end of the voltage sampling unit is connected to the input end of a voltage difference calculation unit, the output end of the voltage difference calculation unit is connected to the input end of a voltage loop PI unit, the voltage loop PI unit is connected to a drive signal distribution unit, and the output end of the drive signal distribution unit is connected to a signal receiving end of the DC-DC converter.

Description

Technical Field

[0001] The present invention belongs to the technical field of motor controllers, and in particular relates to a unified control circuit and a control method based on a DC-DC converter. Background Art

[0002] In hybrid electric vehicles, the motor controller contains TM motor controller and GM motor controller, such as Figure 1 As shown. The GM motor controller is used to control the generator (GM motor), and the TM motor controller is used to control the traction motor (TM motor). The TM motor controller and the GM motor controller share a DC bus and are connected to the high-voltage battery pack.

[0003] The TM motor controller controls the TM motor to output the corresponding traction or braking torque according to the instructions of the VCU, and is the source of driving power for electric vehicles; the GM motor controller controls the torque or speed of the GM motor according to the instructions of the VCU, thereby controlling the amount of power generated by the GM motor.

[0004] There are three working modes inside the motor controller:

[0005] Mode 1: Pure electric mode, the GM motor does not generate electricity, and the TM motor is fully powered by the high-voltage battery pack. It is used in conditions where the high-voltage battery pack has sufficient power and a high SOC (State Of Charge);

[0006] Mode 2: Power generation mode, the GM motor generates electricity, part of the generated energy is used to charge the high-voltage battery pack, and the other part is used to power the TM motor. It is used in the working conditions of insufficient power of the high-voltage battery pack and low SOC;

[0007] Mode 3: Parallel mode, the high-voltage battery pack and the GM motor simultaneously power the TM motor. It is used for the TM motor to output full power at high speeds;

[0008] Since the TM motor controller and the GM motor controller share the same DC bus and are connected to the high-voltage battery pack, the bus voltage is clamped by the high-voltage battery pack and is very stable.

[0009] Further, if Figure 2 As shown in the figure, a DC-DC converter is connected in series to the busbar of the motor controller to boost the voltage of the high-voltage battery pack to power the TM motor. The purpose of this design is to use a lower voltage battery pack (such as 400V) to power a high-voltage TM motor (650V TM motor). The constant torque operating range and motor efficiency of the TM motor can be improved without increasing the cost of the battery pack.

[0010] There are still three working modes inside the motor controller:

[0011] Mode 1: Pure electric mode, the GM motor does not generate electricity, and the DC-DC converter boosts the voltage of the high-voltage battery pack to power the TM motor. It is used when the high-voltage battery pack has sufficient power and high SOC. The DC-DC converter works in boost mode;

[0012] Mode 2: Power generation mode, the GM motor generates electricity, part of the generated energy is stepped down by the DC-DC converter to charge the high-voltage battery pack, and the other part is used to power the TM motor. It is used in the working conditions of insufficient power of the high-voltage battery pack and low SOC. The DC-DC converter works in step-down mode. ;

[0013] Mode 3: Parallel mode, the high-voltage battery pack voltage is boosted by the DC-DC converter and supplies power to the TM motor together with the GM motor. It is used to output full power of the TM motor at high speed. The DC-DC converter works in boost mode;

[0014] The high-voltage battery pack is connected to the low-voltage end of the DC-DC converter, and the high-voltage end of the DC-DC converter shares the DC bus with the TM motor controller and the GM motor controller. Therefore, the bus voltage is not clamped by the high-voltage battery pack, and the bus voltage value is determined by the algebraic sum of the power of the DC-DC, TM motor controller, and GM motor controller on the bus. When the power flowing into the bus is greater than the power flowing out of the bus, the bus voltage rises, and vice versa. When the power flowing into and out of the bus is equal, the bus voltage remains unchanged.

[0015] Its current control scheme is also based on power balance control.

[0016] In pure electric mode, the VCU calculates the power consumed by the TM motor controller on the bus based on the output torque and speed of the TM motor controller, and controls the DC-DC converter to supplement the bus with equal power.

[0017] In the power generation mode, the VCU controls the torque or speed of the GM motor controller to make the engine work in the high-efficiency range. Assume that the power provided by the power generation to the bus is P1, and the bus power consumed by the TM motor controller is P2. Then the VCU controls the DC-DC converter to charge the high-voltage battery pack with P1-P2.

[0018] In parallel mode, the VCU calculates the power P2-P1 that the DC-DC converter needs to provide for the bus (absorbing power from the high-voltage battery pack) based on the bus power P2 consumed by the TM motor controller and the power P1 that the generator can currently provide.

[0019] The prior art has at least the following problems:

[0020] 1. It is difficult to ensure the balance of instantaneous power of the DC bus based on power balance control. Moreover, since the working mode of the DC-DC converter needs to switch between boost (providing power to the DC bus) and buck (absorbing power from the DC bus), and switching takes time, generally between hundreds of microseconds and several milliseconds, the bus power cannot be controlled during the switching process.

[0021] 2. The imbalance of DC bus power in the transient process will cause bus voltage fluctuations, which in turn will increase the harmonic content of the DC-DC converter, TM motor controller and GM motor controller, and reduce the control accuracy. In order to reduce the DC bus fluctuations, the capacitance of the capacitor between the DC buses is often increased, which increases the cost. Summary of the invention

[0022] The present invention provides a unified control circuit and control method based on a DC-DC converter, aiming to solve the technical problems existing in the above-mentioned prior art that the control based on power balance is difficult to ensure the balance of the instantaneous power of the DC bus; and the imbalance of the DC bus power in the transient process will cause the bus voltage to fluctuate, which in turn will increase the harmonic content of the DC-DC converter, the TM motor controller and the GM motor controller, and reduce the control accuracy.

[0023] The technical solution of the present invention to solve the above technical problems is as follows: a unified control circuit based on a DC-DC converter, the DC-DC converter includes an inductor L, a switch tube S1 and a switch tube S2, the second end of the inductor L is respectively connected to one end of the switch tube S1 and one end of the switch tube S2, the other end of the switch tube S1 and the first end of the inductor L are between the low-voltage side of the DC-DC converter, and the other end of the switch tube S1 and the other end of the switch tube S2 are between the DC bus side of the DC-DC converter; the unified control circuit includes a bus PI closed-loop control module, and the bus PI closed-loop control module includes:

[0024] A voltage sampling unit is electrically connected to the DC bus side of the DC-DC converter and is used to sample the voltage on the DC bus side of the DC-DC converter to obtain a voltage sampling value V BUS_Sample ;

[0025] A voltage difference calculation unit is electrically connected to the voltage sampling unit and is used to calculate the voltage sampling value V BUS_Sample and the preset voltage target value V BUS_REF Perform difference processing to obtain the voltage difference result;

[0026] a voltage loop PI unit, electrically connected to the voltage difference calculation unit, configured to perform a proportional integral operation on the voltage difference result and output a first proportional integral operation result;

[0027] A drive signal distribution unit is electrically connected to the voltage loop PI unit, and is used to generate a main PWM drive signal with a duty cycle of D and an auxiliary PWM drive signal with a duty cycle of 1-D according to the first proportional-integral operation result, and distribute the main PWM drive signal and the auxiliary PWM drive signal to the controlled end of the switch tube S1 and the controlled end of the switch tube S2 respectively, so as to control the switch tube S1 and the switch tube S2 to be turned on and off.

[0028] The beneficial effects of the present invention are as follows: the present application uses the voltage on the DC bus side of the DC-DC converter as the control object, constructs a voltage loop PI unit to control it, so that no matter how the power input / output of the TM motor controller and the GM motor controller connected to the DC bus side fluctuates to the DC-DC converter, the DC-DC converter can ensure the voltage stability on the DC bus side, solving the problem that it is difficult to achieve the instantaneous power balance on the DC bus side in the prior art. And the switch tube S1 and the switch tube S2 are controlled by different PWM drive signals to ensure the constant voltage on the DC bus side. At the same time, the working mode of the DC-DC converter is no longer distinguished, and the DC-DC converter is controlled to absorb or supplement power from the DC bus side based on the constant voltage on the DC bus side.

[0029] Based on the above technical solution, the present invention can also be improved as follows.

[0030] Furthermore, the bus PI closed-loop control module further includes:

[0031] A current sampling unit is electrically connected to the DC-DC converter and is used to sample the current of the inductor L in the DC-DC converter to obtain a current sampling value I L_Sample ;

[0032] A current difference calculation unit is electrically connected to the current sampling unit and the voltage loop PI unit, and is used to calculate the current target value I L_Ref With the current sampling value I L_Sample The current target value I L_Ref The first proportional integral operation result output by the voltage loop PI unit;

[0033] The current loop PI unit is connected between the current difference calculation unit and the drive signal distribution unit, and is used to perform a proportional integral operation on the current difference result and output a second proportional integral operation result.

[0034] The beneficial effect of adopting the above further scheme is: the current at the inductor L is obtained through the current sampling unit, and the second proportional integral operation result of the switch tube S1 and the switch tube S2 is calculated through the current loop PI unit, and then the current at the inductor L is controlled by controlling the switch tube S1 and the switch tube S2 of the DC-DC converter, thereby enhancing the dynamic response capability of the DC-DC converter.

[0035] Furthermore, the driving signal distribution unit is specifically configured to allocate a current according to the current sampling value I L_Sample The switch tube S1 or the switch tube S2 is selected as the main switch tube in the direction of , and the switch tube S2 or the switch tube S1 is correspondingly selected as the auxiliary switch tube, and a main PWM drive signal with a duty cycle of D and an auxiliary PWM drive signal with a duty cycle of 1-D are generated according to the second proportional-integral operation result, and the main PWM drive signal and the auxiliary PWM drive signal are respectively allocated to the controlled end of the main switch tube and the controlled end of the auxiliary switch tube to control the main switch tube and the auxiliary switch tube to be alternately turned on and off.

[0036] The beneficial effect of adopting the above further scheme is: the current at the inductor L is obtained through the current sampler, and the second proportional integral operation result of the switch tube S1 and the switch tube S2 is calculated through the current loop PI unit, and then the PWM drive signal of the switch tube S1 and the switch tube S2 is calculated by the drive signal distribution unit, and then the current at the inductor L is controlled by controlling the switch tube S1 and the switch tube S2 of the DC-DC converter, thereby enhancing the dynamic response capability of the DC-DC converter.

[0037] Furthermore, the current flowing from the first end to the second end of the inductor L is regarded as the positive direction.

[0038] When the current sampling value I L_Sample >0 and the current sampling value I L_Sample The absolute value of the current is greater than or equal to the first current threshold I L_th1 When the switch tube S1 is the main switch tube, the switch tube S2 is the auxiliary switch tube, the main PWM drive signal with a duty cycle of D is distributed to the controlled end of the switch tube S1, and the auxiliary PWM drive signal with a duty cycle of 1-D is distributed to the controlled end of the switch tube S2;

[0039] When the current sampling value I L_Sample <0 and the current sampling value I L_Sample The absolute value of the current is greater than or equal to the first current threshold I L_th1 When the switch tube S2 is the main switch tube and the switch tube S1 is the auxiliary switch tube, the main PWM drive signal with a duty cycle of D is distributed to the controlled end of the switch tube S2, and the auxiliary PWM drive signal with a duty cycle of 1-D is distributed to the controlled end of the switch tube S1.

[0040] The beneficial effect of adopting the above further solution is: when the current sampling value I L_Sample >0, the DC-DC converter absorbs power from the high-voltage battery pack and provides it to the DC bus, and the DC-DC converter is equivalent to the boost mode; when the current sampling value I L_Sample When <0, the DC-DC converter absorbs power from the DC bus to charge the high-voltage battery pack, and the DC-DC converter is equivalent to buck mode.

[0041] Furthermore, the unified control circuit mentioned above also includes a hysteresis control module;

[0042] The hysteresis control module is used to L_Sample The absolute value of the current is less than the first current threshold I L_th1 When the bus PI closed-loop control module is controlled to stop working, the voltage sampling value V BUS_Sample drops, and the voltage sampling value V BUS_Sample drops to the second voltage threshold V BUS2 Restart the bus PI closed-loop control module to make the voltage sampling value V BUS_Sample rises, and when the voltage sampling value V BUS_Sample Rising to the first voltage threshold V BUS1 The bus PI closed-loop control module stops working again, and the cycle repeats until the current sampling value I L_Sample The absolute value of the voltage is greater than the second voltage threshold V BUS2 When the bus PI closed-loop control module is controlled, it operates stably.

[0043] The beneficial effect of adopting the above further solution is: when the current sampling value I of the inductor L is L_Sample When the current sampling value I is close to 0A, in order to avoid the main switch tube from frequently switching between the switch tube S1 and the switch tube S2, the above transition method is added. L_Sample <0 and the absolute value is less than the first current threshold I L_th1 When the current sampling value I L_Sample >0 and the absolute value is less than the first current threshold I L_th1 When the switch tube S1 is turned on intermittently, the current of the inductor L is ensured to be continuous when the switch tube S1 is working.

[0044] Furthermore, the low voltage side of the DC-DC converter is electrically connected to a high voltage battery pack, the positive battery bus of the high voltage battery pack is connected to the first end of the inductor L, and the negative battery bus of the high voltage battery pack is connected to one end of the switch tube S1;

[0045] The two ends of the DC bus side of the DC-DC converter are respectively connected to the positive DC bus and the negative DC bus, a bus capacitor is connected between the positive DC bus and the negative DC bus, the other ends of the positive DC bus and the negative DC bus are connected to the DC side of the TM motor controller and the DC side of the GM motor controller, the AC side of the TM motor controller is connected to the TM motor, the AC side of the GM motor controller is connected to the GM motor, and the other end of the GM motor is connected to the engine.

[0046] The beneficial effect of adopting the above further scheme is: the present application distributes the PWM drive signals of the switch tube S1 and the switch tube S2 through the driving distribution unit for control, so that no matter how the power input / output of the TM motor controller and the GM motor controller to the positive DC bus and the negative DC bus fluctuates, the DC-DC converter can ensure the voltage stability on the DC bus side.

[0047] In a second aspect, the present invention further proposes a unified control method based on a DC-DC converter, which is applied to the above-mentioned unified control circuit based on a DC-DC converter, including the steps of bus PI closed-loop control, and the steps of the bus PI closed-loop control are as follows:

[0048] S1: Sampling the voltage on the DC bus side of the DC-DC converter to obtain a voltage sampling value V BUS_Sample ;

[0049] S2: The voltage sampling value V BUS_Sample and the preset voltage target value V BUS_REF Perform difference processing to obtain the voltage difference result;

[0050] S3: performing a proportional-integral operation on the voltage difference result, and outputting a first proportional-integral operation result;

[0051] S4: Generate a main PWM drive signal with a duty cycle of D and an auxiliary PWM drive signal with a duty cycle of 1-D according to the first proportional-integral operation result, and distribute the main PWM drive signal and the auxiliary PWM drive signal to the controlled end of the switch tube S1 and the controlled end of the switch tube S2 respectively, so as to control the switch tube S1 and the switch tube S2 to be turned on and off.

[0052] The beneficial effect of adopting the above further scheme is: the present application takes the voltage on the DC bus side of the DC-DC converter as the control object, constructs a voltage loop PI unit to control it, so that no matter how the power input / output of the TM motor controller and the GM motor controller connected to the DC bus side to the DC-DC converter fluctuates, the DC-DC converter can ensure the voltage stability on the DC bus side, solving the problem that it is difficult to achieve the balance of instantaneous power on the DC bus side in the prior art. And the switch tube S1 and the switch tube S2 are controlled by different PWM drive signals to ensure the constancy of the voltage on the DC bus side. At the same time, the working mode of the DC-DC converter is no longer distinguished, and the DC-DC converter is controlled to absorb or supplement power from the DC bus side based on the constant voltage on the DC bus side.

[0053] Furthermore, the above-mentioned bus PI closed-loop control step also includes:

[0054] S5: Sampling the current of the inductor L in the DC-DC converter to obtain a current sampling value I L_Sample ;

[0055] S6: Set the current target value I L_Ref With the current sampling value I L_Sample The current target value I L_Ref is the first proportional integral operation result obtained in step S3;

[0056] S7: Perform a proportional-integral operation on the current difference result, and output a second proportional-integral operation result.

[0057] The beneficial effect of adopting the above further scheme is: the current at the inductor L is obtained through the current sampling unit, and the second proportional integral operation result of the switch tube S1 and the switch tube S2 is calculated through the current loop PI unit, and then the current at the inductor L is controlled by controlling the switch tube S1 and the switch tube S2 of the DC-DC converter, thereby enhancing the dynamic response capability of the DC-DC converter.

[0058] Further, the above S4 is specifically: according to the current sampling value I L_Sample The switch tube S1 or the switch tube S2 is selected as the main switch tube in the direction of , and the switch tube S2 or the switch tube S1 is correspondingly selected as the auxiliary switch tube, and a main PWM drive signal with a duty cycle of D and an auxiliary PWM drive signal with a duty cycle of 1-D are generated according to the second proportional-integral operation result, and the main PWM drive signal and the auxiliary PWM drive signal are respectively allocated to the controlled end of the main switch tube and the controlled end of the auxiliary switch tube to control the main switch tube and the auxiliary switch tube to be turned on and off.

[0059] The beneficial effect of adopting the above further scheme is: the current at the inductor L is obtained through the current sampler, and the second proportional integral operation result of the switch tube S1 and the switch tube S2 is calculated through the current loop PI unit, and then the PWM drive signal of the switch tube S1 and the switch tube S2 is calculated by the drive signal distribution unit, and then the current at the inductor L is controlled by controlling the switch tube S1 and the switch tube S2 of the DC-DC converter, thereby enhancing the dynamic response capability of the DC-DC converter.

[0060] Furthermore, when the current sampling value I L_Sample >0 and the current sampling value I L_Sample The absolute value of the current is greater than or equal to the first current threshold I L_th1 When the switch tube S1 is the main switch tube, the switch tube S2 is the auxiliary switch tube, the main PWM drive signal with a duty cycle of D is distributed to the controlled end of the switch tube S1, and the auxiliary PWM drive signal with a duty cycle of 1-D is distributed to the controlled end of the switch tube S2;

[0061] When the current sampling value I L_Sample <0 and the current sampling value I L_Sample The absolute value of the current is greater than or equal to the first current threshold I L_th1 When the switch tube S2 is the main switch tube and the switch tube S1 is the auxiliary switch tube, the main PWM drive signal with a duty cycle of D is distributed to the controlled end of the switch tube S2, and the auxiliary PWM drive signal with a duty cycle of 1-D is distributed to the controlled end of the switch tube S1.

[0062] The beneficial effect of adopting the above further solution is: when the current sampling value I L_Sample >0, the DC-DC converter absorbs power from the high-voltage battery pack and provides it to the DC bus, and the DC-DC converter is equivalent to the boost mode; when the current sampling value I L_Sample When <0, the DC-DC converter absorbs power from the DC bus to charge the high-voltage battery pack, and the DC-DC converter is equivalent to buck mode.

[0063] Further, the method further includes a hysteresis control step, wherein the hysteresis control step is as follows:

[0064] Step 1: Monitor the current sampling value I L_Sample , when the current sampling value I L_Sample The absolute value of the current is less than the first current threshold I L_th1 When the bus PI closed-loop control stops, the voltage sampling value V BUS_Sample , so that the voltage sampling value V BUS_Sample decline;

[0065] Step 2: The voltage sampling value V BUS_Sample drops to the second voltage threshold V BUS2When the bus PI closed-loop control is restarted, the voltage sampling value V BUS_Sample When the voltage sampling value V BUS_Sample Rising to the first voltage threshold V BUS1 The bus PI closed-loop control is stopped again, and the cycle repeats until the current sampling value I L_Sample The absolute value of the current is greater than the second current threshold I L_th2 When the bus PI closed-loop control is stably operated, the voltage sampling value V BUS_Sample Stable at the first voltage threshold V BUS1 .

[0066] The beneficial effect of adopting the above further solution is: when the current sampling value I of the inductor L is L_Sample When the current sampling value I is close to 0A, in order to avoid the main switch tube from frequently switching between the switch tube S1 and the switch tube S2, the above transition method is added. L_Sample <0 and the absolute value is less than the first current threshold I L_th1 When the current sampling value I L_Sample >0 and the absolute value is less than the first current threshold I L_th1 When the switch tube S1 is turned on intermittently, the current of the inductor L is ensured to be continuous when the switch tube S1 is working.

[0067] Additional aspects and advantages of the present application will be partially given in the following description, which will become apparent from the following description, or will be understood through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] Figure 1 A schematic diagram of the connection relationship of a motor controller in the background technology of the present invention;

[0069] Figure 2 A schematic diagram of the connection relationship of a motor controller including a DC-DC converter in the background technology of the present invention;

[0070] Figure 3 A schematic diagram of the connection relationship of a motor controller provided by one embodiment of the present invention;

[0071] Figure 4 A connection diagram of a voltage loop PI unit control provided by an embodiment of the present invention;

[0072] Figure 5 A connection diagram of a current loop PI unit control provided by an embodiment of the present invention

[0073] Figure 6 A waveform diagram of a current discontinuous mode when the inductor current is positive provided by one embodiment of the present invention;

[0074] Figure 7 A waveform diagram using the Burst1 mode is provided for one embodiment of the present invention. DETAILED DESCRIPTION

[0075] The principles and features of the present invention are described below. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0076] The technical solution of the present invention and how the technical solution of the present invention solves the above-mentioned technical problems are described in detail below with specific embodiments. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be repeated in some embodiments. The embodiments of the present invention will be described below in conjunction with the accompanying drawings.

[0077] like Figure 3-Figure 5 As shown, an embodiment of the present invention provides a unified control circuit based on a DC-DC converter, wherein the DC-DC converter includes an inductor L, a switch tube S1 and a switch tube S2, wherein the second end of the inductor L is connected to one end of the switch tube S1 and one end of the switch tube S2 respectively, and the area between the other end of the switch tube S1 and the first end of the inductor L is the low-voltage side of the DC-DC converter, and the area between the other end of the switch tube S1 and the other end of the switch tube S2 is the DC bus side of the DC-DC converter; the unified control circuit includes a bus PI closed-loop control module, and the bus PI closed-loop control module includes:

[0078] A voltage sampling unit is electrically connected to the DC bus side of the DC-DC converter and is used to sample the voltage on the DC bus side of the DC-DC converter to obtain a voltage sampling value V BUS_Sample ;

[0079] A voltage difference calculation unit is electrically connected to the voltage sampling unit and is used to calculate the voltage sampling value V BUS_Sample and the preset voltage target value V BUS_REF Perform difference processing to obtain the voltage difference result;

[0080] a voltage loop PI unit, electrically connected to the voltage difference calculation unit, configured to perform a proportional integral operation on the voltage difference result and output a first proportional integral operation result;

[0081] A drive signal distribution unit is electrically connected to the voltage loop PI unit, and is used to generate a main PWM drive signal with a duty cycle of D and an auxiliary PWM drive signal with a duty cycle of 1-D according to the first proportional-integral operation result, and distribute the main PWM drive signal and the auxiliary PWM drive signal to the controlled end of the switch tube S1 and the controlled end of the switch tube S2 respectively, so as to control the switch tube S1 and the switch tube S2 to be turned on and off.

[0082] Among them, the present application takes the voltage on the DC bus side of the DC-DC converter as the control object, constructs a voltage loop PI unit to control it, so that no matter how the power input / output of the TM motor controller and the GM motor controller connected to the DC bus side fluctuates to the DC-DC converter, the DC-DC converter can ensure the voltage stability on the DC bus side, solving the problem that it is difficult to achieve instantaneous power balance on the DC bus side in the prior art. And the switch tube S1 and the switch tube S2 are controlled by different PWM drive signals to ensure the constant voltage on the DC bus side. At the same time, the working mode of the DC-DC converter is no longer distinguished, and the DC-DC converter is controlled to absorb or supplement power from the DC bus side based on the constant voltage on the DC bus side.

[0083] Optionally, the bus PI closed-loop control module further includes:

[0084] A current sampling unit is electrically connected to the DC-DC converter and is used to sample the current of the inductor L in the DC-DC converter to obtain a current sampling value I L_Sample ;

[0085] A current difference calculation unit is electrically connected to the current sampling unit and the voltage loop PI unit, and is used to calculate the current target value I L_Ref With the current sampling value I L_Sample The current target value I L_Ref The first proportional integral operation result output by the voltage loop PI unit;

[0086] The current loop PI unit is connected between the current difference calculation unit and the drive signal distribution unit, and is used to perform a proportional integral operation on the current difference result and output a second proportional integral operation result.

[0087] Among them, the current at the inductor L is obtained through the current sampling unit, and the second proportional integral operation result of the switch tube S1 and the switch tube S2 is calculated through the current loop PI unit, and then the current at the inductor L is controlled by controlling the switch tube S1 and the switch tube S2 of the DC-DC converter, thereby enhancing the dynamic response capability of the DC-DC converter.

[0088] Optionally, the driving signal distribution unit is specifically configured to distribute the current according to the current sampling value I L_Sample The switch tube S1 or the switch tube S2 is selected as the main switch tube in the direction of , and the switch tube S2 or the switch tube S1 is correspondingly selected as the auxiliary switch tube, and a main PWM drive signal with a duty cycle of D and an auxiliary PWM drive signal with a duty cycle of 1-D are generated according to the second proportional-integral operation result, and the main PWM drive signal and the auxiliary PWM drive signal are respectively allocated to the controlled end of the main switch tube and the controlled end of the auxiliary switch tube to control the main switch tube and the auxiliary switch tube to be turned on and off.

[0089] Among them, the current at the inductor L is obtained through the current sampler, and the second proportional integral operation results of the switch tube S1 and the switch tube S2 are calculated through the current loop PI unit, and then the PWM drive signals of the switch tube S1 and the switch tube S2 are calculated through the drive signal distribution unit, and then the current at the inductor L is controlled by controlling the switch tube S1 and the switch tube S2 of the DC-DC converter, thereby enhancing the dynamic response capability of the DC-DC converter.

[0090] Optionally, the current flowing from the first end to the second end of the inductor L is regarded as the positive direction.

[0091] When the current sampling value I L_Sample >0 and the current sampling value I L_Sample The absolute value of the current is greater than or equal to the first current threshold I L_th1 When the switch tube S1 is the main switch tube, the switch tube S2 is the auxiliary switch tube, the main PWM drive signal with a duty cycle of D is distributed to the controlled end of the switch tube S1, and the auxiliary PWM drive signal with a duty cycle of 1-D is distributed to the controlled end of the switch tube S2;

[0092] When the current sampling value I L_Sample <0 and the current sampling value I L_Sample The absolute value of the current is greater than or equal to the first current threshold I L_th1 When the switch tube S2 is the main switch tube and the switch tube S1 is the auxiliary switch tube, the main PWM drive signal with a duty cycle of D is distributed to the controlled end of the switch tube S2, and the auxiliary PWM drive signal with a duty cycle of 1-D is distributed to the controlled end of the switch tube S1.

[0093] Among them, when the current sampling value I L_Sample >0, the DC-DC converter absorbs power from the high-voltage battery pack and provides it to the DC bus, and the DC-DC converter is equivalent to the boost mode; when the current sampling value I L_Sample When <0, the DC-DC converter absorbs power from the DC bus to charge the high-voltage battery pack, and the DC-DC converter is equivalent to buck mode.

[0094] Optionally, the unified control circuit further includes a hysteresis control module;

[0095] The hysteresis control module is used to L_Sample The absolute value of the current is less than the first current threshold I L_th1 When the bus PI closed-loop control module is controlled to stop working, the voltage sampling value V BUS_Sample drops, and the voltage sampling value V BUS_Sample drops to the second voltage threshold V BUS2 Restart the bus PI closed-loop control module to make the voltage sampling value V BUS_Sample rises, and when the voltage sampling value V BUS_Sample Rising to the first voltage threshold V BUS1 The bus PI closed-loop control module stops working again, and the cycle repeats until the current sampling value I L_Sample The absolute value of the voltage is greater than the first voltage threshold V BUS1 When the bus PI closed-loop control module is controlled, it operates stably.

[0096] Among them, when the current sampling value of the inductor L is I L_Sample When the current sampling value I is close to 0A, in order to avoid the main switch tube from frequently switching between the switch tube S1 and the switch tube S2, the above transition method is added. L_Sample <0 and the absolute value is less than the first current threshold I L_th1 When the current sampling value I L_Sample >0 and the absolute value is less than the first current threshold I L_th1 When the switch tube S1 is turned on intermittently, the current of the inductor L is ensured to be continuous when the switch tube S1 is working.

[0097] Optionally, the low-voltage side of the DC-DC converter is electrically connected to a high-voltage battery pack, a positive battery bus of the high-voltage battery pack is connected to the first end of the inductor L, and a negative battery bus of the high-voltage battery pack is connected to one end of the switch tube S1;

[0098] The two ends of the DC bus side of the DC-DC converter are respectively connected to the positive DC bus DC+ and the negative DC bus DC-, a bus capacitor is connected between the positive DC bus DC+ and the negative DC bus DC-, the other ends of the positive DC bus DC+ and the negative DC bus DC- are both connected to the DC side of the TM motor controller and the DC side of the GM motor controller, the AC side of the TM motor controller is connected to the TM motor, the AC side of the GM motor controller is connected to the GM motor, and the other end of the GM motor is connected to the engine.

[0099] Among them, the present application distributes the PWM drive signals of the switch tube S1 and the switch tube S2 through the driving distribution unit for control, so that no matter how the power input / output of the TM motor controller and the GM motor controller to the positive DC bus and the negative DC bus fluctuates, the DC-DC converter can ensure the voltage stability on the DC bus side.

[0100] Working principle:

[0101] The logic of the driving signal distribution unit is to pass the current sampling value I L_Sample In the reverse direction, switch tube S1 or switch tube S2 is selected as the main switch tube, and the duty cycle D is assigned to the PWM drive signal of the main switch tube. Specifically:

[0102] Assume the positive direction of the inductor current is Figure 3 shown.

[0103] Get the current sampling value I L_Sample , when the current sampling value I L_Sample >0, the duty cycle of switch S1 is D, and the duty cycle of switch S2 is 1-D. At this time, S1 is the main switch. L_Sample <0, the duty cycle of the switch tube S2 is D, and the duty cycle of the switch tube S1 is 1-D. At this time, S2 is the main switch tube.

[0104] When the current sampling value I L_Sample >0, the DC-DC converter absorbs power from the high-voltage battery pack and provides it to the DC bus side. The DC-DC converter is equivalent to the boost mode, and the switch tube S1 is the main switch tube, assigning the duty cycle D to the PWM drive signal G S1 , assign the duty cycle 1-D to the PWM drive signal G S2 .

[0105] When the current sampling value I L_Sample <0, the DC-DC converter absorbs power from the DC bus side to charge the high-voltage battery pack, and the DC-DC converter is equivalent to the buck mode. The switch tube S2 is the main switch tube, and the duty cycle D is assigned to the PWM drive signal G S2 , assign the duty cycle 1-D to the PWM drive signal G S1 .

[0106] Since the current sampling value I L_Sample The driving signal is distributed in the direction of L_Sample When it is close to 0A, the drive signal will appear in the PWM drive signal G S1 and PWM drive signal G S2 Moreover, when the current sampling value I L_SampleWhen the current is very small, the DC-DC converter operates in the current discontinuous mode, the controllability of the DC-DC converter decreases, and the efficiency decreases.

[0107] Figure 6 This is the waveform of the current discontinuous mode when the inductor current is positive. Before time A, the inductor current I L Continuous, PWM drive signal G S1 and PWM drive signal G S2 The duty cycles are D and 1-D respectively, and the switching period is Ts.

[0108] At time A, the output power of the DC-DC converter decreases, and the inductor current I L The average value of the inductor current I L1 Rapidly decreases to the inductor current I L2 . Inductor current I L2 Discontinuous, if the PWM drive signal G S1 The duty cycle is D, then the PWM drive signal G S2 The duty cycle is no longer 1-D, because there is no drive signal when the current is 0A, and the switching period is still Ts. In discontinuous mode, since the voltage loop PI unit is still working, the ripple of the DC bus voltage is very small.

[0109] Figure 7 This is the waveform of the Burst1 mode. When the inductor current of the DC-DC converter drops to I L_th1 After that, the dual-loop control of the DC-DC converter stops working, and the switch tube S1 and the switch tube S2 are turned off. The DC bus voltage increases from the first voltage threshold V BUS1 After time T2, the voltage drops to the second voltage threshold V BUS2 At time B, the dual-loop control of the DC-DC converter starts, and the DC bus voltage gradually rises to the first voltage threshold V BUS1 At this time, the average value of the inductor current is I L3 , the current waveform is continuous. However, since the maximum value of the inductor current does not exceed I L_th2 , indicating that the inductor current is still small at this time, and the inductor current is still intermittent during continuous operation. Therefore, the dual-loop control starts and stops, and the bus voltage drops from the first voltage threshold V BUS1 To the second voltage threshold V BUS2 This cycle repeats itself, forming the Burst1 mode.

[0110] At time C, the inductor current exceeds the second current threshold I L_th2 , indicating that the load current increases, the inductor current can work in continuous mode, so it exits Burst1 mode, and the dual-loop control continues to work. When the DC bus voltage reaches the first voltage threshold V BUS1After that, the voltage loop PI unit in the dual-loop control stabilizes the bus voltage at the first voltage threshold V BUS1 .

[0111] Therefore, the Burst1 mode is: when IL>0 and the current is too small, the inductor current is discontinuous, the switch tube S1 is intermittently turned on to ensure that the inductor current is continuous when the switch tube S1 is working; similarly, there is a Burst2 mode, that is, when IL<0 and the current is too small, the inductor current is discontinuous, S2 is intermittently turned on to ensure that the inductor current is continuous when S2 is working. When the inductor current is negative, the above control situation is the same.

[0112] The present invention also proposes a unified control method based on a DC-DC converter, which is applied to the above-mentioned unified control circuit based on a DC-DC converter, including the steps of bus PI closed-loop control, and the steps of the bus PI closed-loop control are as follows:

[0113] S1: Sampling the voltage on the DC bus side of the DC-DC converter to obtain a voltage sampling value V BUS_Sample ;

[0114] S2: The voltage sampling value V BUS_Sample and the preset voltage target value V BUS_REF Perform difference processing to obtain the voltage difference result;

[0115] S3: performing a proportional-integral operation on the voltage difference result, and outputting a first proportional-integral operation result;

[0116] S4: Generate a main PWM drive signal with a duty cycle of D and an auxiliary PWM drive signal with a duty cycle of 1-D according to the first proportional-integral operation result, and distribute the main PWM drive signal and the auxiliary PWM drive signal to the controlled end of the switch tube S1 and the controlled end of the switch tube S2 respectively, so as to control the switch tube S1 and the switch tube S2 to be turned on and off.

[0117] Among them, the present application takes the voltage on the DC bus side of the DC-DC converter as the control object, constructs a voltage loop PI unit to control it, so that no matter how the power input / output of the TM motor controller and the GM motor controller connected to the DC bus side fluctuates to the DC-DC converter, the DC-DC converter can ensure the voltage stability on the DC bus side, solving the problem that it is difficult to achieve instantaneous power balance on the DC bus side in the prior art. And the switch tube S1 and the switch tube S2 are controlled by different PWM drive signals to ensure the constant voltage on the DC bus side. At the same time, the working mode of the DC-DC converter is no longer distinguished, and the DC-DC converter is controlled to absorb or supplement power from the DC bus side based on the constant voltage on the DC bus side.

[0118] Optionally, the bus PI closed-loop control step further includes:

[0119] S5: Sampling the current of the inductor L in the DC-DC converter to obtain a current sampling value I L_Sample ;

[0120] S6: Set the current target value I L_Ref With the current sampling value I L_Sample The current target value I L_Ref is the first proportional integral operation result obtained in step S3;

[0121] S7: Perform a proportional-integral operation on the current difference result, and output a second proportional-integral operation result.

[0122] Among them, the current at the inductor L is obtained through the current sampling unit, and the second proportional integral operation result of the switch tube S1 and the switch tube S2 is calculated through the current loop PI unit, and then the current at the inductor L is controlled by controlling the switch tube S1 and the switch tube S2 of the DC-DC converter, thereby enhancing the dynamic response capability of the DC-DC converter.

[0123] Optionally, the S4 is specifically: according to the current sampling value I L_Sample The switch tube S1 or the switch tube S2 is selected as the main switch tube in the direction of , and the switch tube S2 or the switch tube S1 is correspondingly selected as the auxiliary switch tube, and a main PWM drive signal with a duty cycle of D and an auxiliary PWM drive signal with a duty cycle of 1-D are generated according to the second proportional-integral operation result, and the main PWM drive signal and the auxiliary PWM drive signal are respectively allocated to the controlled end of the main switch tube and the controlled end of the auxiliary switch tube to control the main switch tube and the auxiliary switch tube to be turned on and off.

[0124] Among them, the current at the inductor L is obtained through the current sampler, and the second proportional integral operation results of the switch tube S1 and the switch tube S2 are calculated through the current loop PI unit, and then the PWM drive signals of the switch tube S1 and the switch tube S2 are calculated through the drive signal distribution unit, and then the current at the inductor L is controlled by controlling the switch tube S1 and the switch tube S2 of the DC-DC converter, thereby enhancing the dynamic response capability of the DC-DC converter.

[0125] Optionally, when the current sampling value I L_Sample >0 and the current sampling value I L_Sample The absolute value of the current is greater than or equal to the first current threshold I L_th1When the switch tube S1 is the main switch tube, the switch tube S2 is the auxiliary switch tube, the main PWM drive signal with a duty cycle of D is distributed to the controlled end of the switch tube S1, and the auxiliary PWM drive signal with a duty cycle of 1-D is distributed to the controlled end of the switch tube S2;

[0126] When the current sampling value I L_Sample <0 and the current sampling value I L_Sample The absolute value of the current is greater than or equal to the first current threshold I L_th1 When the switch tube S2 is the main switch tube and the switch tube S1 is the auxiliary switch tube, the main PWM drive signal with a duty cycle of D is distributed to the controlled end of the switch tube S2, and the auxiliary PWM drive signal with a duty cycle of 1-D is distributed to the controlled end of the switch tube S1.

[0127] Among them, when the current sampling value I L_Sample >0, the DC-DC converter absorbs power from the high-voltage battery pack and provides it to the DC bus, and the DC-DC converter is equivalent to the boost mode; when the current sampling value I L_Sample When <0, the DC-DC converter absorbs power from the DC bus to charge the high-voltage battery pack, and the DC-DC converter is equivalent to buck mode.

[0128] Optionally, the method further includes a hysteresis control step, wherein the hysteresis control step is as follows:

[0129] Step 1: Monitor the current sampling value I L_Sample , when the current sampling value I L_Sample The absolute value of the current is less than the first current threshold I L_th1 When the bus PI closed-loop control stops, the voltage sampling value V BUS_Sample , so that the voltage sampling value V BUS_Sample decline;

[0130] Step 2: The voltage sampling value V BUS_Sample drops to the second voltage threshold V BUS2 When the bus PI closed-loop control is restarted, the voltage sampling value V BUS_Sample When the voltage sampling value V BUS_Sample Rising to the first voltage threshold V BUS1 The bus PI closed-loop control is stopped again, and the cycle repeats until the current sampling value I L_Sample The absolute value of the current is greater than the second current threshold I L_th2 When the bus PI closed-loop control is stably operated, the voltage sampling value V BUS_Sample Stable at the first voltage threshold V BUS1 .

[0131] The beneficial effect of adopting the above further solution is: when the current sampling value I of the inductor L is L_SampleWhen the current sampling value I is close to 0A, in order to avoid the main switch tube from frequently switching between the switch tube S1 and the switch tube S2, the above transition method is added. L_Sample <0 and the absolute value is less than the first current threshold I L_th1 When the current sampling value I L_Sample >0 and the absolute value is less than the first current threshold I L_th1 When the switch tube S1 is turned on intermittently, the current of the inductor L is ensured to be continuous when the switch tube S1 is working.

[0132] The above description is only a preferred embodiment of the present invention and an explanation of the technical principles used. Those skilled in the art should understand that the disclosure scope involved in the present invention is not limited to the technical solution formed by a specific combination of the above technical features, but should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the above disclosed concept. For example, the above features are replaced with the technical features with similar functions disclosed in the present invention (but not limited to) by each other.

Claims

1. A unified control circuit based on a DC-DC converter, characterized in that: The DC-DC converter includes an inductor L, a switch tube S1 and a switch tube S2, the second end of the inductor L is connected to one end of the switch tube S1 and one end of the switch tube S2 respectively, the other end of the switch tube S1 and the first end of the inductor L are between the low voltage side of the DC-DC converter, and the other end of the switch tube S1 and the other end of the switch tube S2 are between the DC bus side of the DC-DC converter; the unified control circuit includes a bus PI closed-loop control module, and the bus PI closed-loop control module includes: A voltage sampling unit is electrically connected to the DC bus side of the DC-DC converter and is used to sample the voltage on the DC bus side of the DC-DC converter to obtain a voltage sampling value V BUS_Sample ; A voltage difference calculation unit is electrically connected to the voltage sampling unit and is used to calculate the voltage sampling value V BUS_Sample and the preset voltage target value V BUS_REF Perform difference processing to obtain the voltage difference result; a voltage loop PI unit, electrically connected to the voltage difference calculation unit, configured to perform a proportional integral operation on the voltage difference result and output a first proportional integral operation result; a driving signal distribution unit, electrically connected to the voltage loop PI unit, for generating a main PWM driving signal with a duty cycle of D and an auxiliary PWM driving signal with a duty cycle of 1-D according to the first proportional-integral operation result, and respectively distributing the main PWM driving signal and the auxiliary PWM driving signal to the controlled end of the switch tube S1 and the controlled end of the switch tube S2, so as to control the switch tube S1 and the switch tube S2 to be turned on and off; The bus PI closed-loop control module also includes: A current sampling unit is electrically connected to the DC-DC converter and is used to sample the current of the inductor L in the DC-DC converter to obtain a current sampling value I L_Sample ; A current difference calculation unit is electrically connected to the current sampling unit and the voltage loop PI unit, and is used to calculate the current target value I L_Ref With the current sampling value I L_Sample The current target value I L_Ref The first proportional integral operation result output by the voltage loop PI unit; A current loop PI unit, connected between the current difference calculation unit and the drive signal distribution unit, for performing a proportional integral operation on the current difference result and outputting a second proportional integral operation result; The unified control circuit also includes a hysteresis control module; The hysteresis control module is used to L_Sample The absolute value of the current is less than the first current threshold I L_th1 When the bus PI closed-loop control module is controlled to stop working, the voltage sampling value V BUS_Sample drops, and the voltage sampling value V BUS_Sample drops to the second voltage threshold V BUS2 Restart the bus PI closed-loop control module to make the voltage sampling value V BUS_Sample rises, and when the voltage sampling value V BUS_Sample Rising to the first voltage threshold V BUS1 The bus PI closed-loop control module stops working again, and the cycle repeats until the current sampling value I L_Sample The absolute value of the current is greater than the second current threshold I L_th2 When the bus PI closed-loop control module is controlled, it operates stably.

2. The unified control circuit based on a DC-DC converter according to claim 1, characterized in that: The driving signal distribution unit is specifically used to allocate the current according to the current sampling value I L_Sample The switch tube S1 or the switch tube S2 is selected as the main switch tube in the direction of , and the switch tube S2 or the switch tube S1 is correspondingly selected as the auxiliary switch tube, and a main PWM drive signal with a duty cycle of D and an auxiliary PWM drive signal with a duty cycle of 1-D are generated according to the second proportional-integral operation result, and the main PWM drive signal and the auxiliary PWM drive signal are respectively allocated to the controlled end of the main switch tube and the controlled end of the auxiliary switch tube to control the main switch tube and the auxiliary switch tube to be turned on and off.

3. A unified control circuit based on a DC-DC converter according to claim 2, characterized in that: The current flows from the first end to the second end of the inductor L as the positive direction. When the current sampling value I L_Sample >0 and the current sampling value I L_Sample The absolute value of the current is greater than or equal to the first current threshold I L_th1 When the switch tube S1 is the main switch tube, the switch tube S2 is the auxiliary switch tube, the main PWM drive signal with a duty cycle of D is distributed to the controlled end of the switch tube S1, and the auxiliary PWM drive signal with a duty cycle of 1-D is distributed to the controlled end of the switch tube S2; When the current sampling value I L_Sample <0 and the current sampling value I L_Sample The absolute value of the current is greater than or equal to the first current threshold I L_th1 When the switch tube S2 is the main switch tube and the switch tube S1 is the auxiliary switch tube, the main PWM drive signal with a duty cycle of D is distributed to the controlled end of the switch tube S2, and the auxiliary PWM drive signal with a duty cycle of 1-D is distributed to the controlled end of the switch tube S1.

4. A unified control method based on a DC-DC converter, characterized in that: A unified control circuit based on a DC-DC converter as claimed in any one of claims 1 to 3, comprising a bus PI closed-loop control step, wherein the bus PI closed-loop control step is as follows: S1: Sampling the voltage on the DC bus side of the DC-DC converter to obtain a voltage sampling value V BUS_Sample ; S2: The voltage sampling value V BUS_Sample and the preset voltage target value V BUS_REF Perform difference processing to obtain the voltage difference result; S3: performing a proportional-integral operation on the voltage difference result, and outputting a first proportional-integral operation result; S4: generating a main PWM drive signal with a duty cycle of D and an auxiliary PWM drive signal with a duty cycle of 1-D according to the first proportional-integral operation result, and respectively distributing the main PWM drive signal and the auxiliary PWM drive signal to the controlled end of the switch tube S1 and the controlled end of the switch tube S2 to control the switch tube S1 and the switch tube S2 to be turned on and off; The bus PI closed-loop control step also includes: S5: Sampling the current of the inductor L in the DC-DC converter to obtain a current sampling value I L_Sample ; S6: Set the current target value I L_Ref With the current sampling value I L_Sample The current target value I L_Ref is the first proportional integral operation result obtained in step S3; S7: performing a proportional-integral operation on the current difference result, and outputting a second proportional-integral operation result; The method further includes the steps of hysteresis control, wherein the steps of hysteresis control are as follows: Step 1: Monitor the current sampling value I L_Sample , when the current sampling value I L_Sample The absolute value of the current is less than the first current threshold I L_th1 When the bus PI closed-loop control stops, the voltage sampling value V BUS_Sample , so that the voltage sampling value V BUS_Sample decline; Step 2: The voltage sampling value V BUS_Sample drops to the second voltage threshold V BUS2 When the bus PI closed-loop control is restarted, the voltage sampling value V BUS_Sample When the voltage sampling value V BUS_Sample Rising to the first voltage threshold V BUS1 The bus PI closed-loop control is stopped again, and the cycle repeats until the current sampling value I L_Sample The absolute value of the current is greater than the second current threshold I L_th2 When the bus PI closed-loop control is stably operated, the voltage sampling value V BUS_Sample Stable at the first voltage threshold V BUS1 .

5. A unified control method based on a DC-DC converter according to claim 4, characterized in that: The S4 is specifically: according to the current sampling value I L_Sample The switch tube S1 or the switch tube S2 is selected as the main switch tube in the direction of , and the switch tube S2 or the switch tube S1 is correspondingly selected as the auxiliary switch tube, and a main PWM drive signal with a duty cycle of D and an auxiliary PWM drive signal with a duty cycle of 1-D are generated according to the second proportional-integral operation result, and the main PWM drive signal and the auxiliary PWM drive signal are respectively allocated to the controlled end of the main switch tube and the controlled end of the auxiliary switch tube to control the main switch tube and the auxiliary switch tube to be turned on and off.

6. A unified control method based on a DC-DC converter according to claim 5, characterized in that: When the current sampling value I L_Sample >0 and the current sampling value I L_Sample The absolute value of the current is greater than or equal to the first current threshold I L_th1 When the switch tube S1 is the main switch tube, the switch tube S2 is the auxiliary switch tube, the main PWM drive signal with a duty cycle of D is distributed to the controlled end of the switch tube S1, and the auxiliary PWM drive signal with a duty cycle of 1-D is distributed to the controlled end of the switch tube S2; When the current sampling value I L_Sample <0 and the current sampling value I L_Sample The absolute value of the current is greater than or equal to the first current threshold I L_th1 When the switch tube S2 is the main switch tube and the switch tube S1 is the auxiliary switch tube, the main PWM drive signal with a duty cycle of D is distributed to the controlled end of the switch tube S2, and the auxiliary PWM drive signal with a duty cycle of 1-D is distributed to the controlled end of the switch tube S1.

Images