CN-117767720-B - Vehicle-mounted DC-DC conversion device and electric automobile

CN117767720BCN 117767720 BCN117767720 BCN 117767720BCN-117767720-B

Abstract

The invention provides a vehicle-mounted DC-DC conversion device and an electric automobile, and relates to the field of power sources, wherein the vehicle-mounted DC-DC converter comprises a first bridge unit, a transformer, a synchronous rectification unit and a clamping absorption circuit; and the controller is used for outputting driving signals for driving the first bridge unit, the synchronous rectification unit and the switching tube in the clamping absorption circuit, and sequentially works in a discharging stage of the clamping capacitor, a pre-charging stage of the clamping capacitor and a starting stage with gradually increased duty ratio in a starting stage of the vehicle-mounted DC-DC converter in a reverse mode for converting the second voltage into the first voltage. The reliability of starting the vehicle-mounted DC-DC converter can be improved.

Inventors

BI QINGSHENG
LI ZHAO
HAO SHIQIANG

Assignees

浙江富特科技股份有限公司

Dates

Publication Date: 20260508
Application Date: 20231226

Claims (9)

1. A vehicle-mounted DC-DC conversion device, comprising: The vehicle-mounted DC-DC converter comprises a first bridge unit, a second bridge unit and a first voltage generation unit, wherein the first bridge unit is used for receiving or outputting a first voltage; the secondary winding center tap transformer, the first bridge unit connects the primary winding; the synchronous rectification unit is characterized in that a first synchronous rectification tube and a second synchronous rectification tube are respectively connected between two ends of a secondary winding and a grounding end, an inductor is connected between a center tap and a first end of a second capacitor, the second end of the second capacitor is grounded, and the second capacitor is used for outputting or receiving a second voltage; A controller for controlling the vehicle DC-DC converter to sequentially operate in a discharging stage of the clamping capacitor, a pre-charging stage of the clamping capacitor and a start-up stage with gradually increased duty ratio when the vehicle DC-DC converter operates in a reverse mode from the second voltage to the first voltage, wherein In the discharging stage of the clamping capacitor, a driving signal output by the controller firstly controls a switching tube in the first bridge unit to be inoperative, and the first synchronous rectifying tube and the second synchronous rectifying tube operate in an amplifying region to store energy in the forward direction of an inductor; In the pre-charging stage of the clamping capacitor, a clamping switching tube working in the clamping absorption circuit is conducted after a switching tube corresponding to the working in the first bridge unit is conducted, and the switching tube corresponding to the working in the first bridge unit is turned off before being turned off; And in the start-up stage with the gradually increased duty ratio, when the duty ratio of the driving signal of the switching tube in the low-voltage side synchronous rectification unit is smaller than 50%, the switching tube in the synchronous rectification unit and the switching tube correspondingly operated in the first bridge unit synchronously operate, the duty ratio is synchronously and gradually increased, and when the duty ratio of the driving signal of the switching tube in the low-voltage side synchronous rectification unit is increased to be larger than 50%, the switching tube in the synchronous rectification unit and the switching tube correspondingly operated in the first bridge unit complementarily operate.
2. The on-vehicle DC-DC converter according to claim 1, wherein the driving signal output from the controller controls the first synchronous rectifier and the second synchronous rectifier to be alternately turned on during the discharging phase of the clamp capacitor.
3. The vehicle-mounted DC-DC conversion apparatus according to claim 2, wherein the driving signal outputted from the controller controls the first clamp switching tube and the second clamp switching tube to be alternately turned on and the switching tube corresponding to the first bridge unit to operate in a discharging stage of the clamp capacitor.
4. The on-vehicle DC-DC converter according to claim 3, wherein in a discharge phase of the clamp capacitor, the driving signals outputted by the controller to control the first synchronous rectifier and the second synchronous rectifier are a cluster of narrow pulses having a phase shift angle of 180 °, and the driving signals to control the first clamp switch and the second clamp switch are a cluster of narrow pulses having a phase shift angle of 180 °; and the first synchronous rectifying tube and a cluster of narrow pulses of the first clamping switching tube are alternately sent out, and the second synchronous rectifying tube and a cluster of narrow pulses of the second clamping switching tube are alternately sent out.
5. The vehicle-mounted DC-DC conversion device according to claim 4, wherein a duration of a high level of one pulse period of the narrow pulse is 150ns to 200ns.
6. The on-vehicle DC-DC conversion device according to claim 1 or 5, wherein the controller performs, in a precharge phase of the clamp capacitor: s1, the controller outputs a driving signal with a fixed duty ratio of one period to a switching tube working in the vehicle-mounted DC-DC converter, and adds up a count value Cnt to 1; S2, judging whether the count value Cnt is smaller than a count set maximum value Cntr, if yes, entering a step S3, otherwise, entering a step S4; s3, judging whether the voltage Vclamp on the clamping capacitor is larger than a voltage set value Vr, if so, entering a step S5, and if not, entering a step S1; s4, reporting a pre-charging failure, and ending a start-up stage of the vehicle-mounted DC-DC converter; S5, entering a start-up stage of gradually increasing the duty ratio of the vehicle-mounted DC-DC converter.
7. The on-vehicle DC-DC converter according to claim 6, wherein the on-vehicle DC-DC converter operates in an open loop mode during a precharge phase of the clamp capacitor.
8. The on-vehicle DC-DC conversion device according to claim 7, wherein the controller outputs a drive signal of a fixed duty ratio in a precharge phase of the clamp capacitor.
9. An electric vehicle comprising the on-vehicle DC-DC converter according to claim 1.

Description

Vehicle-mounted DC-DC conversion device and electric automobile Technical Field The invention relates to the field of power sources, in particular to a vehicle-mounted DC-DC conversion device and an electric automobile. Background With the development of science and technology and society, new energy automobiles have been widely used and have an increasing duty ratio. Electric vehicles often include a high voltage battery that draws electrical energy from a power grid and stores the energy in the high voltage battery as a source of electrical energy within the electric vehicle. An onboard DC-DC converter is used to convert high voltage battery energy of an electric vehicle to low voltage battery energy of, for example, 12V to power loads in a new energy vehicle. The conventional vehicle-mounted DC-DC converter is a bidirectional DC-DC converter, which can convert a high voltage (e.g., 400V) on a high-voltage battery into a low voltage (e.g., 12V) on a low-voltage battery, or convert a low voltage (e.g., 12V) on a low-voltage battery into a high voltage (e.g., 400V) on a high-voltage battery. When the vehicle-mounted DC-DC converter is started, the vehicle-mounted DC-DC converter may be required to work at a start-up state for converting a high voltage (such as 400V) on a high-voltage battery into a low voltage (such as 12V) on a low-voltage battery, which is called as a forward start-up state. It is also possible to start the machine, which requires the vehicle-mounted DC-DC converter to operate to convert a low voltage (e.g. 12V) on the low voltage battery to a high voltage (e.g. 400V) on the high voltage battery, we call the reverse start machine. The forward start and the reverse start can cause interference such as impact current, impact voltage and the like, and also can cause the problems that part of devices cannot work normally, such as switching tube loss, drive chip damage, transformer magnetic saturation and the like, so that the reliability of the vehicle-mounted DC-DC converter is influenced. Disclosure of Invention The invention provides a vehicle-mounted DC-DC conversion device, which comprises: The vehicle-mounted DC-DC converter comprises a vehicle-mounted DC-DC converter, a clamping absorption circuit, a clamping switch tube and a clamping capacitor, wherein the vehicle-mounted DC-DC converter comprises a first bridge unit, a secondary winding center tap transformer, a synchronous rectification unit, a first synchronous rectification tube and a second synchronous rectification tube, an inductor, a second capacitor and a clamping absorption circuit, the first bridge unit is used for receiving or outputting a first voltage, the secondary winding center tap transformer is connected with a primary winding, the first synchronous rectification tube and the second synchronous rectification tube are respectively connected between two ends of the secondary winding and a grounding end, the inductor is connected between a center tap and a first end of the second capacitor, a second end of the second capacitor is grounded, and the second capacitor is used for outputting or receiving a second voltage; and the controller is used for controlling the vehicle-mounted DC-DC converter to sequentially operate in a discharging stage of the clamping capacitor, a pre-charging stage of the clamping capacitor and a start-up stage with gradually increased duty ratio in a start-up stage of the vehicle-mounted DC-DC converter in a reverse mode of converting the second voltage into the first voltage. Further, in the discharging stage of the clamping capacitor, the driving signal output by the controller firstly controls the switching tube in the first bridge unit to be disabled, the first synchronous rectifying tube and the second synchronous rectifying tube to work so as to store energy forward for the inductor, and then controls the first clamping switching tube and the second clamping switching tube to work, and the switching tube in the first bridge unit works so as to discharge the voltage on the clamping capacitor to the first capacitor. Further, in the discharging stage of the clamping capacitor, the driving signal output by the controller controls to enable the first clamping switching tube and the second clamping switching tube to work in the amplifying region, and controls to enable the first synchronous rectifying tube and the second synchronous rectifying tube to work in the amplifying region. Further, in the discharging stage of the clamping capacitor, the driving signal output by the controller controls the first synchronous rectifying tube and the second synchronous rectifying tube to be alternately conducted. Further, in the discharging stage of the clamping capacitor, the driving signal output by the controller controls the first clamping switching tube and the second clamping switching tube to be alternately conducted, and the switching tube corresponding to the first bridge unit works. Further, in t