CN214189371U

CN214189371U - Hybrid active discharge circuit

Info

Publication number: CN214189371U
Application number: CN202022752761.6U
Authority: CN
Inventors: 冯颖盈; 姚顺; 冯仁伟
Original assignee: Shenzhen Vmax Power Co Ltd
Current assignee: Shenzhen Vmax Power Co Ltd; Shenzhen VMAX New Energy Co Ltd
Priority date: 2020-11-24
Filing date: 2020-11-24
Publication date: 2021-09-14
Anticipated expiration: 2030-11-24

Abstract

The utility model discloses a hybrid active discharge circuit, it includes controller and high-pressure power battery, and high-pressure power battery passes through the direct current generating line and connects high-pressure inverter, high-pressure DC/DC respectively, high-pressure DC/DC connects the low-voltage battery, connect high-voltage electric capacity between the positive and negative generating line of direct current generating line, high-pressure inverter connects high-pressure alternating current load, low-voltage battery connects the low-voltage battery load, the connection of high-pressure DC/DC the input of direct current generating line is equipped with the branch road that discharges; in the early stage of discharging, the high-voltage capacitor charges the low-voltage battery through high-voltage DC/DC; in the later discharge period, the high-voltage capacitor discharges through the discharge branch; one part of the discharge electric energy is transmitted to the low-voltage battery, one part of the discharge electric energy is consumed in the HVDCDC converter, and the other part of the discharge electric energy is consumed in the miniaturized power discharge resistor.

Description

Hybrid active discharge circuit

Technical Field

The utility model relates to an electric automobile high pressure driving system field, concretely relates to mix initiative discharge circuit.

Background

The voltage at the input terminal of the inverter used in the electric vehicle and the hybrid vehicle is higher than 60Vdc, and in order to protect personal safety, it is required to provide a discharge circuit in the dc side capacitor of the inverter to reduce the voltage of the dc side capacitor. The conventional active discharge method is to add an active discharge circuit, discharge by using a power resistor, but needs to add an additional constant power control circuit, so that the cost is increased, the volume of the power discharge resistor is large, and the power discharge resistor can be damaged after being discharged for many times.

Therefore, it is an urgent technical problem to design a discharge circuit with energy saving, small size, long service life and reliable operation.

SUMMERY OF THE UTILITY MODEL

In order to solve the above-mentioned defect that exists among the prior art, the utility model provides a mix initiative discharge circuit.

The utility model adopts the technical scheme that a hybrid active discharge circuit is designed, which comprises a controller and a high-voltage power battery, wherein the high-voltage power battery is respectively connected with a high-voltage inverter and a high-voltage DC/DC through a direct current bus, the high-voltage DC/DC is connected with a low-voltage battery, a high-voltage capacitor is connected between a positive bus and a negative bus of the direct current bus, the high-voltage inverter is connected with a high-voltage alternating current load, the low-voltage battery is connected with a low-voltage battery load, and the input end of the direct current bus connected with the high-voltage DC/DC is provided with a discharge branch; in the early stage of discharging, the high-voltage capacitor charges the low-voltage battery through high-voltage DC/DC; and in the later discharge period, the high-voltage capacitor discharges through the discharge branch.

The discharge branch comprises a discharge resistor PTC and a discharge switch Q1 which are connected in series, and the discharge switch Q1 is controlled by a controller.

And a power switch SW1 is connected between the high-voltage power battery and the direct-current bus in series.

The direct current bus is also connected with other high-voltage electric equipment.

The high-voltage DC/DC comprises a primary side conversion module, a high-frequency transformer and a secondary side conversion module which are sequentially connected, wherein the primary side conversion module adopts a full-bridge topological structure, the secondary side conversion module adopts a synchronous rectification topological structure, and the secondary side conversion module comprises a sixth switch Q6 and a seventh switch Q7; the sixth switch Q6 and the seventh switch Q7 adopt MOS transistors with body diodes.

The utility model provides a technical scheme's beneficial effect is:

the utility model discloses a mix initiative discharge mode, the route of discharging becomes partly energy transmission for low-voltage battery, partly energy consumption in HVDCDC converter by single consumption on power discharge resistance, and another part energy consumption has that discharge speed is fast, power discharge resistance size is little, with low costs, easy control and the advantage that the reliability is high on miniaturized power discharge resistance.

Drawings

The invention is explained in more detail below with reference to exemplary embodiments and the accompanying drawings, in which:

FIG. 1 is a schematic block diagram of a preferred embodiment of the present invention;

fig. 2 is a circuit diagram of an HVDCDC converter according to a preferred embodiment of the present invention;

fig. 3 is a timing diagram of waveforms according to a preferred embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more clearly understood, the present invention will be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

The utility model discloses a mix initiative discharge circuit, refer to the schematic block diagram of the preferred embodiment of the utility model shown in figure 1, it includes controller and high-voltage power battery, and high-voltage power battery passes through the direct current generating line and connects high-voltage inverter, high-voltage DC/DC respectively, low voltage battery is connected to high-voltage DC/DC, connect high-voltage electric capacity between the positive and negative generating line of direct current generating line, high-voltage inverter connects high-voltage alternating current load, low voltage battery connects low voltage battery load, the input that high-voltage DC/DC connects the direct current generating line is equipped with the branch road that discharges; in the early stage of discharging, the high-voltage capacitor charges the low-voltage battery through high-voltage DC/DC; and in the later discharge period, the high-voltage capacitor discharges through the discharge branch.

In fig. 1, C1 is the equivalent input capacitance of the high-voltage inverter, including the DC-LINK capacitance and other internal capacitances. C2 is the equivalent input capacitance of high voltage DC/DC (HVDCDC), including DC-LINK capacitance and other internal capacitance. Cn is equivalent input capacitance of other high-voltage equipment, including equipment such as a vehicle-mounted charger and a high-voltage air conditioner. SW1 is a high-voltage battery main relay, which comprises a main positive relay contact and a main negative relay contact. After receiving the active discharge command, the high voltage inverter or the HVDCDC starts the HVDCDC to work, and the energy on the high voltage capacitors C1, C2 and Cn is supplied to the low voltage battery for charging and consuming in the HVDCDC working process, such as switching loss and the like.

In a preferred embodiment, the discharge branch comprises a discharge resistor PTC and a discharge switch Q1 connected in series, and the discharge switch Q1 is controlled by a controller. The discharge switch Q1 may employ a MOSFET. Due to the limitations of the HVDCDC output voltage level, which cannot continue to charge the low-voltage battery with energy from the high-voltage capacitors C1, C2, Cn after the HV input voltage drops to a lower level, i.e., the HV threshold voltage noted in this patent, and is consumed during the HVDCDC operation, this patent adds a PTC discharge method to supplement the active discharge after the HV voltage drops below the HV voltage threshold voltage. The PTC active discharge dissipates the energy remaining on the high voltage capacitors C1, C2, Cn in the form of heat across the PTC resistor. In fig. 2, the power discharge resistor is not limited to the PTC resistor, and other resistor types such as a wire resistor and a cement resistor may be used.

In fig. 1, the thin line arrows indicate the flow of power during discharge, and the power flows from the high-voltage inverter, the primary side of HVDCDC, and other high-voltage electric devices to the low-voltage battery and the low-voltage battery load.

In fig. 1, besides raising the HVDCDC output voltage to consume high-voltage capacitance energy, raising the operating frequency thereof can also be used within a safe operating range to realize active discharge by using HVDCDC switching loss.

To the problem and not enough that exist among the prior art, the utility model provides a mix initiative discharge circuit. The discharge path is changed into a plurality of mixed active discharge modes such that a part of energy is transferred to a low-voltage battery from a single consumed power discharge resistor, a part of energy is consumed in the HVDCDC converter, and the other part of energy is consumed in a miniaturized power discharge resistor. Based on the hybrid active discharge control method, the high-voltage inverter of the electric automobile can realize the characteristics of high discharge speed, reduced size of a power discharge resistor, low cost, easy control and high reliability, and even no power discharge resistor is needed.

In the preferred embodiment, a power switch SW1 is connected in series between the high voltage power battery and the dc bus. When the high-voltage power battery needs to be charged or the high-voltage power battery needs to supply power to a load, the controller turns on the power switch SW 1. When the controller sends an active discharge command or the internal fault of the high-voltage inverter causes the active discharge command, the power switch SW1 is cut off, so that greater safety accidents are prevented.

In a preferred embodiment, the direct current bus is also connected with other high-voltage electric equipment.

Referring to fig. 2, a circuit diagram of an HVDCDC converter according to a preferred embodiment of the present invention is shown, wherein the high voltage DC/DC converter includes a primary side conversion module, a high frequency transformer, and a secondary side conversion module, which are connected in sequence, the primary side conversion module adopts a full-bridge topology, the secondary side conversion module adopts a synchronous rectification topology, and the secondary side conversion module includes a sixth switch Q6 and a seventh switch Q7; the sixth switch Q6 and the seventh switch Q7 adopt MOS transistors with body diodes. The primary side conversion module converts high-voltage direct current in C1, C2 and Cn into direct current pulse, the direct current pulse is transmitted to the secondary side conversion module through the high-frequency transformer, and the secondary side conversion module carries out rectification and then charges the low-voltage battery. In fig. 2 Vhv is the high voltage capacitor voltage.

The working process of the present invention is further explained by combining fig. 1 and fig. 2:

in the early stage of discharging, the high-voltage capacitor charges the low-voltage battery through high-voltage DC/DC; and in the later discharge period, the high-voltage capacitor discharges through the discharge branch. It is pointed out that after receiving an active discharge command sent by the controller, the high-voltage DC/DC is started and the output voltage of the high-voltage DC/DC is raised to charge the low-voltage battery. The specific boost voltage value is determined by the HVDCDC hardware parameters and the voltage battery parameters.

Detecting the voltage of the high-voltage capacitor after the discharge is started, and charging the low-voltage battery by the high-voltage capacitor through high-voltage DC/DC when the voltage of the high-voltage capacitor is higher than a threshold voltage; when the voltage of the high-voltage capacitor is not higher than the threshold voltage, the high-voltage capacitor discharges through the discharge branch circuit; and when the voltage of the high-voltage capacitor is lower than the threshold voltage, ending the discharge. The threshold voltage may vary from one model of device to another and is not specifically limited in this patent.

In the preferred embodiment, when the voltage of the high voltage capacitor is detected not to be higher than the threshold voltage and before the PTC starts to discharge, the front-end time controlled discharge switch Q1 is turned on continuously for a short time to perform pre-discharge, i.e., PTC pre-discharge, in order to protect the PTC and its series MOSFET Q1. This PTC pre-discharge process is enabled by giving a short time PTC discharge. The later period of time controls the discharge switch Q1 to be intermittently conducted by PWM signal for discharging. The PTC discharge adopts a PWM pulse enabling discharge mode to reduce the loss and thermal stress of the PTC resistor and the MOSFET Q1, thereby improving the reliability. Before the HVDCDC discharge starts, the HVDCDC pre-discharge can be carried out in a manner similar to the PTC pre-discharge manner, and the method is used for detecting whether faults such as relay adhesion exist.

In a preferred embodiment, when the high-voltage capacitor charges the low-voltage battery through high-voltage DC/DC, the sixth switch Q6 and the seventh switch Q7 can be controlled to perform synchronous rectification, and also can perform rectification through the body diode thereof. Referring to fig. 2, when the high voltage DC/DC is charged to the low voltage battery, the synchronous rectifiers Q6 and Q7 may not be turned on, and the parasitic body diode thereof is used to increase the discharge loss and accelerate the active discharge speed.

Fig. 3 is a timing chart of waveforms according to the preferred embodiment of the present invention.

The starting and output levels of HVDCDC are controlled, the enabling of a PTC discharging circuit is controlled, two control objects are realized through driving signals of Q2-Q5 and Q6-Q7 and driving signals of Q1 respectively, wherein Q6 and Q7 are synchronous rectifying tubes on the secondary side of HVDCDC.

And T0, receiving an active discharge command.

And T0-T1, the HVDCDC output voltage is raised, active discharge is started, and the high-voltage capacitor energy is transferred to the low-voltage battery and is partially consumed in the HVDCDC.

T1-T2, PTC pre-discharge, the PTC pre-discharge process is determined by giving a short time PTC discharge enable and monitoring whether the HV voltage change meets a preset HV droop rate.

And T2-T3, PTC discharge consumes residual energy after HVDCDC discharge on the PTC resistor, and the process adopts a PWM discharge mode to reduce average loss of the PTC resistor and Q1.

At time T3, the HV capacitance voltage drops below the safe voltage.

The foregoing examples are illustrative only and are not intended to be limiting. Any equivalent modifications or variations without departing from the spirit and scope of the present application should be included in the claims of the present application.

Claims

1. A hybrid active discharge circuit is characterized by comprising a controller and a high-voltage power battery, wherein the high-voltage power battery is respectively connected with a high-voltage inverter and a high-voltage DC/DC through a direct-current bus, the high-voltage DC/DC is connected with a low-voltage battery, a high-voltage capacitor is connected between a positive bus and a negative bus of the direct-current bus, the high-voltage inverter is connected with a high-voltage alternating-current load, the low-voltage battery is connected with a low-voltage battery load, and a discharge branch is arranged at the input end of the high-voltage DC/DC, which is connected with the direct-current bus;

in the early stage of discharging, the high-voltage capacitor charges the low-voltage battery through high-voltage DC/DC;

and in the later discharge period, the high-voltage capacitor discharges through the discharge branch.

2. The hybrid active discharge circuit of claim 1 wherein said discharge branch comprises a series connected discharge resistor PTC and a discharge switch Q1, said discharge switch Q1 being controlled by a controller.

3. The hybrid active discharge circuit of claim 1 wherein a power switch SW1 is connected in series between the high voltage power battery and the dc bus.

4. The hybrid active discharge circuit of claim 1 wherein said DC bus further connects a high voltage inverter to other high voltage electrical devices than high voltage DC/DC.

5. The hybrid active discharge circuit of any of claims 1 to 4, wherein the high voltage DC/DC comprises a primary side conversion module, a high frequency transformer, and a secondary side conversion module connected in sequence, the primary side conversion module adopts a full-bridge topology, the secondary side conversion module adopts a synchronous rectification topology, and the secondary side conversion module comprises a sixth switch Q6 and a seventh switch Q7; the sixth switch Q6 and the seventh switch Q7 adopt MOS transistors with body diodes.