Direct-current side voltage discharge method of bidirectional isolation topology and application of direct-current side voltage discharge method
By adopting a DC-side voltage leakage method with a bidirectional isolation topology in the DC output converter, the driving duty cycle of the transformer and the switch tube is used to control the current for leakage, which solves the problem of slow voltage drop when the DC output converter is shut down in the prior art, and achieves low-cost and efficient voltage leakage.
Patent Information
- Application Number
- CN202411980080.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-31
- Publication Date
- 2025-04-11
AI Technical Summary
In the prior art, the DC output converter is shut down due to the existence of filter capacitors, which causes the port voltage to drop very slowly, which cannot meet the relevant safety requirements, and increasing the discharge circuit will increase the complexity and cost of hardware design.
The DC-side voltage leakage method is adopted with a bidirectional isolation topology. Through the cooperation of the transformer, controller, primary and secondary bridge arms, the driving duty cycle of the switch tube is used to control the current flowing through the transformer for discharge, so as to realize the discharge of the output capacitor and port voltage.
This method does not require the use of discharge resistors, which reduces the cost, and controls the current magnitude by adjusting the driving duty cycle of the switch tube, protecting the switch tube, achieving effective voltage leakage.
Smart Images
Figure CN119813743A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of power electronics, and in particular to a DC side voltage discharge method of a bidirectional isolation topology and an application thereof. Background Art
[0002] DC output converters usually have filter capacitors on the output side to reduce output ripple. However, the presence of this capacitor will cause the port voltage to drop very slowly when the device is turned off, which does not meet the relevant safety regulations and may also cause inconvenience to the use of the device. The common practice in the prior art is to add a discharge circuit on the output port side of the module. Common discharge circuit forms are as follows: Figure 1 , Figure 2 shown.
[0003] Solution 1, such as Figure 1 As shown in Figure 2, a resistor is directly connected in parallel at both ends of the filter capacitor during pressure relief. When the module is turned off, the resistor R1 can discharge the remaining energy in the capacitor C1. Figure 2 As shown, to further reduce the loss, when the module is turned off, Q1 is controlled to be turned on, and the resistor R1 is connected in parallel to both ends of C1 for discharge. When the module is turned on, Q1 is controlled to be turned off, and the resistor R1 is disconnected from both ends of the capacitor. Figure 1 The solution can reduce losses during operation.
[0004] Both of the above forms require additional circuits for discharge, which increases the complexity and cost of hardware design.
[0005] Therefore, how to solve the above technical problems is the research direction that technicians in this field are committed to. Summary of the invention
[0006] The object of the present invention is to overcome the deficiencies of the prior art and provide a DC side voltage discharge method of a bidirectional isolation topology.
[0007] To achieve the above object, the technical solution adopted by the present invention is: a DC side voltage discharge method of a bidirectional isolation topology, wherein the bidirectional isolation topology includes a transformer, a controller, a primary bridge arm, a secondary bridge arm and an output capacitor, wherein the midpoint of the primary bridge arm is connected to the primary winding of the transformer, and the two ends of the primary bridge arm are respectively connected to the two ends of the DC power supply; the midpoint of the secondary bridge arm is connected to the secondary winding of the transformer, and the two ends of the secondary bridge arm are respectively connected to the two ends of the output capacitor; the switch tube of each bridge arm in the secondary bridge arm includes an upper tube and a lower tube, The steps for DC side voltage discharge are as follows: 1) The controller receives a discharge command; 2) The controller determines the driving duty cycle of the initial switch tube of the secondary bridge arm according to the sampled output capacitor voltage value through the formula DT=I*L / V or the relationship DT=F(V) obtained by adjustment. Here, DT represents the driving duty cycle, I is the switch tube current limit, V is the output voltage, and L is the inductance; F(V) represents the functional relationship between the duty cycle obtained by adjustment and the output capacitor voltage; 3) Assume that one of the secondary bridge arms is the first bridge arm, and the controller sends a drive corresponding to the duty cycle to the upper tube of the first bridge arm. Correspondingly, the upper tube of the first bridge arm is turned on, and the capacitor discharge current passes through the upper tube of the first bridge arm, the secondary winding, and the switch tubes in other secondary bridge arms and returns to the other end of the capacitor. The discharge current flowing through the upper tube of the first bridge arm increases slowly, and the energy is converted into transformer loss through the transformer and transmitted to the primary device at the same time; 4) After the driving time of the upper tube of the first bridge arm reaches the driving duty cycle, the controller turns off the driving of the upper tube of the first bridge arm. At this time, the discharge current is less than or equal to the current limit of the switch tube, the excitation inductor continues to flow, and the discharge current is transferred to the lower tube of the first bridge arm. The discharge current flows through the lower tube of the first bridge arm, the secondary winding, and the switch tubes of other secondary bridge arms and then returns to the other end of the capacitor. The discharge current flowing through the lower tube of the first bridge arm decreases, and the energy is converted into transformer loss through the transformer and transmitted to the primary device at the same time; 5) After 1 / 2 switching cycle, the controller sends a drive corresponding to the duty cycle to the lower tube of the first bridge arm. Correspondingly, the lower tube of the first bridge arm is turned on, and the capacitor discharge current returns to the other end of the capacitor after passing through the switch tube of the secondary bridge arm of other phases, the secondary winding, and the lower tube of the first bridge arm. The discharge current flowing through the lower tube of the first bridge arm slowly increases, and the energy is converted into transformer loss through the transformer and transmitted to the primary device at the same time; 6) After the driving time of the lower tube of the first bridge arm reaches the driving duty cycle, the controller turns off the driving of the lower tube of the first bridge arm. At this time, the discharge current is less than or equal to the current limit of the switch tube, the excitation inductor continues to flow, and the discharge current is transferred to the upper tube of the first bridge arm. The discharge current flows through the switch tubes of other secondary bridge arms, the secondary winding, and the upper tube of the first bridge arm and then returns to the other end of the capacitor. The discharge current flowing through the upper tube of the first bridge arm decreases, and the energy is converted into transformer loss through the transformer and transmitted to the primary device at the same time; 7) Let n be the total number of secondary bridge arms, and repeat the operations of step 3) to step 6) for the mth secondary bridge arm after (m-1) / n cycles of step 1), where m≤n; 8) Repeat the operations from step 3) to step 7), without adjusting the duty cycle DT or adjusting it according to the output capacitor voltage sampled by the controller in real time, until the output capacitor voltage detected by the controller drops to the discharge threshold, and then stop the wave discharge.
[0008] As a specific implementation manner, the switch tubes in the primary bridge arm and the secondary bridge arm are selected from any one or more of IGBT tubes, MOSFET tubes, SCR tubes and GaN tubes.
[0009] Another object of the present invention is to provide the application of the DC side voltage discharge method of the above-mentioned bidirectional isolation topology in dual active bridge, synchronous rectification LLC, bidirectional CLLLC and bidirectional CLLC topologies.
[0010] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art: 1) The DC side voltage discharge method of the present invention does not use devices such as discharge resistors in the bidirectional isolation topology adopted, and has lower cost; 2) The DC side voltage discharge method of the present invention mainly generates waves for the switch tube of the secondary bridge arm, converts the voltage energy of the output capacitor and the port into the loss of the transformer and transmits it to the primary side device, and at the same time adjusts the size of the waves to control the current not to exceed the specification of the switch tube, thereby protecting the switch tube of the secondary bridge arm from damage and realizing the discharge of the output filter capacitor and the port. BRIEF DESCRIPTION OF THE DRAWINGS
[0011] Figure 1 This is the electrical principle block diagram of the current scheme 1 design; Figure 2 This is the electrical schematic diagram of the current Scheme 2 design; Figure 3 This is a single-phase LLC electrical principle block diagram designed in Example 1; Figure 4 This is a three-phase LLC electrical principle block diagram designed in Example 2; Figure 5 is a single-phase LLC output discharge switch tube drive and transformer secondary winding current diagram in Example 1; Figure 6 This is the three-phase LLC output discharge switch tube drive and transformer secondary winding current diagram in Example 2. DETAILED DESCRIPTION
[0012] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and specific embodiments.
[0013] The present invention provides a DC side voltage discharge method of a bidirectional isolation topology. The bidirectional isolation topology includes a transformer, a controller, a primary bridge arm, a secondary bridge arm and an output capacitor. The midpoint of the primary bridge arm is connected to the primary winding of the transformer, and the two ends of the primary bridge arm are respectively connected to the two ends of a DC power supply; the midpoint of the secondary bridge arm is connected to the secondary winding of the transformer, and the two ends of the secondary bridge arm are respectively connected to the two ends of the output capacitor; the switch tube of each bridge arm in the secondary bridge arm includes an upper tube and a lower tube. Example 1
[0014] See also Figure 3 As shown, the bidirectional isolation topology in this example adopts a single-phase LLC, and its secondary bridge arm includes bridge arm 1 and bridge arm 2. The upper tube in bridge arm 1 is Q7, and the lower tube is Q8; the upper tube in bridge arm 2 is Q9, the lower tube is Q10, and the capacitor is C1. The DC side voltage discharge steps are as follows: 1) The controller receives a discharge command; 2) The controller determines the driving duty cycle of the initial switch tube of the secondary bridge arm according to the sampled output capacitor voltage value through the formula DT=I*L / V or the relationship DT=F(V) obtained by adjustment. Here, DT represents the driving duty cycle, I is the switch current limit, V is the output voltage, and L is the inductance; F (V) represents the functional relationship between the duty cycle and the output capacitor voltage obtained by adjustment; 3) The controller sends a drive with a corresponding duty cycle to the upper tube Q7 of bridge arm 1. Correspondingly, the upper tube Q7 of bridge arm 1 is turned on, and the discharge current of capacitor C1 returns to the other end of capacitor C1 after passing through the upper tube Q7 of bridge arm 1, the secondary winding, and the lower tube Q10 of bridge arm 2. The discharge current flowing through the upper tube Q7 of bridge arm 1 increases slowly, and the energy is converted into transformer loss through the transformer and transmitted to the primary devices at the same time; 4) After the driving time of the upper tube Q7 of bridge arm 1 reaches the driving duty cycle, the controller turns off the upper tube drive of bridge arm 1. At this time, the discharge current is less than or equal to the switch tube current limit, the excitation inductor continues to flow, and the discharge current is transferred to the lower tube Q8 of bridge arm 1. The discharge current flows through the lower tube Q8 of bridge arm 1, the secondary winding, and the upper tube Q9 of bridge arm 2 and then returns to the other end of capacitor C1. The discharge current flowing through the lower tube Q8 of bridge arm 1 decreases, and the energy is converted into transformer loss through the transformer and transmitted to the primary side devices at the same time; 5) After 1 / 2 switching cycle, the controller sends a corresponding duty cycle drive to the lower tube Q8 of bridge arm 1. Correspondingly, the lower tube Q8 of bridge arm 1 is turned on, and the capacitor discharge current passes through the upper tube Q9 of bridge arm 2, the secondary winding, and the lower tube Q8 of bridge arm 1 and returns to the other end of capacitor C1. The discharge current flowing through the lower tube Q8 of bridge arm 1 increases slowly, and the energy is converted into transformer loss through the transformer and transmitted to the primary devices at the same time; 6) After the driving time of the lower tube Q8 of bridge arm 1 reaches the driving duty cycle, the controller turns off the driving of the lower tube Q8 of bridge arm 1. At this time, the discharge current is less than or equal to the current limit of the switch tube, the excitation inductor continues to flow, and the discharge current is transferred to the upper tube Q7 of bridge arm 1. The discharge current flows through the lower tube Q10 of bridge arm 2, the secondary winding, and the upper tube Q7 of bridge arm 1 and then returns to the other end of capacitor C1. The discharge current flowing through the upper tube Q7 of bridge arm 1 decreases, and the energy is converted into transformer loss through the transformer and transmitted to the primary side devices at the same time; 7) In the 1 / 2 cycle after step 1), repeat the operations of step 3) to step 6) for the switch tube on the second bridge arm; 8) Repeat the operations of step 3) to step 7), and adjust the duty cycle DT according to the output capacitor voltage sampled by the controller in real time until the output capacitor voltage detected by the controller drops to the discharge threshold, and then stop the wave discharge.
[0015] Here, the switch tube can be any one or more of an IGBT tube, a MOSFET tube, an SCR tube and a GaN tube.
[0016] In this example, the switch driver in the secondary bridge arm and the transformer secondary winding current diagram are shown in Figure 5 shown.
[0017] The voltage discharge method used in this example is mainly to achieve voltage discharge by controlling the secondary bridge arm switch tube drive in the main power topology and using the transformer as the discharge path. When the output capacitor needs to be discharged, the controller drives the switch tube of the secondary bridge arm, and the current flows through the switch tube and the transformer, converting the energy of the output capacitor into copper loss and magnetic loss of the transformer and transmitting it to the primary side device to achieve output capacitor voltage discharge. When the controller detects that the output voltage drops to a voltage that does not require discharge, it stops driving the switch tube. In addition, the discharge current is limited by detecting the duty cycle of the switch tube. Since the internal resistance and inductance of the transformer are fixed, according to the formula I=V*DT / L, the discharge current is related to the output voltage. The drive duty cycle of the switch tube can be calculated according to the output voltage, and the current size is controlled to meet the current limit of the switch tube without damaging the switch tube. Example 2
[0018] See also Figure 4 As shown, the bidirectional isolation topology in this example adopts a three-phase LLC, and its secondary bridge arm includes bridge arm 1, bridge arm 2 and bridge arm 3. The upper tube in bridge arm 1 is Q7, and the lower tube is Q8; the upper tube in bridge arm 2 is Q9, and the lower tube is Q10; the upper tube in bridge arm 3 is Q11, the lower tube is Q12, and the capacitor is C1. The difference in the DC side voltage discharge process is that in this example, because there are three bridge arms, the action time of the three bridge arms is 1 / 3 of the switching cycle. The switch tube drive in the secondary bridge arm and the secondary winding current of the transformer refer to Figure 6 shown.
[0019] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.
Claims
1. A DC side voltage discharge method of a bidirectional isolation topology, characterized in that: The bidirectional isolation topology includes a transformer, a controller, a primary bridge arm, a secondary bridge arm and an output capacitor. The midpoint of the primary bridge arm is connected to the primary winding of the transformer, and the two ends of the primary bridge arm are respectively connected to the two ends of the DC power supply; the midpoint of the secondary bridge arm is connected to the secondary winding of the transformer, and the two ends of the secondary bridge arm are respectively connected to the two ends of the output capacitor; the switch tube of each bridge arm in the secondary bridge arm includes an upper tube and a lower tube, The steps for DC side voltage discharge are as follows: 1) The controller receives a discharge command; 2) The controller determines the driving duty cycle of the initial switch tube of the secondary bridge arm according to the sampled output capacitor voltage value through the formula DT=I*L / V or the relationship DT=F(V) obtained by adjustment. Here, DT represents the driving duty cycle, I is the switch tube current limit, V is the output voltage, and L is the inductance; F(V) represents the functional relationship between the duty cycle obtained by adjustment and the output capacitor voltage; 3) Assume that one of the secondary bridge arms is the first bridge arm, and the controller sends a drive corresponding to the duty cycle to the upper tube of the first bridge arm. Correspondingly, the upper tube of the first bridge arm is turned on, and the capacitor discharge current passes through the upper tube of the first bridge arm, the secondary winding, and the switch tubes in other secondary bridge arms and returns to the other end of the capacitor. The discharge current flowing through the upper tube of the first bridge arm increases slowly, and the energy is converted into transformer loss through the transformer and transmitted to the primary device at the same time; 4) After the driving time of the upper tube of the first bridge arm reaches the driving duty cycle, the controller turns off the driving of the upper tube of the first bridge arm. At this time, the discharge current is less than or equal to the current limit of the switch tube, the excitation inductor continues to flow, and the discharge current is transferred to the lower tube of the first bridge arm. The discharge current flows through the lower tube of the first bridge arm, the secondary winding, and the switch tubes of other secondary bridge arms and then returns to the other end of the capacitor. The discharge current flowing through the lower tube of the first bridge arm decreases, and the energy is converted into transformer loss through the transformer and transmitted to the primary device at the same time; 5) After 1 / 2 switching cycle, the controller sends a drive corresponding to the duty cycle to the lower tube of the first bridge arm. Correspondingly, the lower tube of the first bridge arm is turned on, and the capacitor discharge current returns to the other end of the capacitor after passing through the switch tube of the secondary bridge arm of other phases, the secondary winding, and the lower tube of the first bridge arm. The discharge current flowing through the lower tube of the first bridge arm slowly increases, and the energy is converted into transformer loss through the transformer and transmitted to the primary device at the same time; 6) After the driving time of the lower tube of the first bridge arm reaches the driving duty cycle, the controller turns off the driving of the lower tube of the first bridge arm. At this time, the discharge current is less than or equal to the current limit of the switch tube, the excitation inductor continues to flow, and the discharge current is transferred to the upper tube of the first bridge arm. The discharge current flows through the switch tubes of other secondary bridge arms, the secondary winding, and the upper tube of the first bridge arm and then returns to the other end of the capacitor. The discharge current flowing through the upper tube of the first bridge arm decreases, and the energy is converted into transformer loss through the transformer and transmitted to the primary device at the same time; 7) Let n be the total number of secondary bridge arms, and repeat the operations of step 3) to step 6) for the mth secondary bridge arm after (m-1) / n cycles of step 1), where m≤n; 8) Repeat the operations from step 3) to step 7), without adjusting the duty cycle DT or adjusting it according to the output capacitor voltage sampled by the controller in real time, until the output capacitor voltage detected by the controller drops to the discharge threshold, and then stop the wave discharge.
2. The DC side voltage discharge method of a bidirectional isolation topology according to claim 1 is characterized in that: The switch tubes in the primary bridge arm and the secondary bridge arm are selected from any one or more of IGBT tubes, MOSFET tubes, SCR tubes and GaN tubes.
3. An application of a DC side voltage discharge method of a bidirectional isolation topology as described in any one of claims 1 to 2 in a dual active bridge, synchronous rectification LLC, bidirectional CLLLC and bidirectional CLLC topologies.