A direct current converter standby current optimization method, output circuit and direct current converter

Abstract

This invention relates to the field of switching power supply technology for electric vehicles, specifically to a method for optimizing standby current of a DC-DC converter, an output circuit, and a DC-DC converter. The DC-DC converter output circuit includes a power supply, a BOOST circuit, and a forward circuit and a flyback circuit electrically connected to the BOOST circuit, respectively. Under no-load conditions, the flyback circuit supplies power instead of the BOOST circuit's BURST mode standby, maintaining power supply in standby mode and effectively reducing standby current. Simultaneously, when a sudden load is applied, the flyback circuit can temporarily boost the circuit's output voltage, providing response time for the BOOST circuit to start up and ensuring that the converter's output voltage does not drop excessively during BOOST circuit startup. The circuit achieves response to load conditions by adding a current-limiting resistor R1 at the output of the flyback circuit, thus achieving cost-effective reduction of standby current while ensuring responsiveness to sudden load applications.

Description

Technical Field

[0001] This invention relates to the field of switching power supply technology for electric vehicles, specifically to a method for optimizing the standby current of a DC-DC converter, an output circuit, and a DC-DC converter. Background Technology

[0002] In DC-DC converters with wide input range and high power, a two-stage circuit (Boost + forward / half-bridge, etc.) is often used to achieve power output and heat dissipation. When the output is unloaded, the BOOST enters BURST mode, and the effective value of the input standby current is relatively large, even exceeding the standby current required by electric vehicles such as forklifts. While turning off the BOOST chip in standby mode can reduce the standby current, when a sudden load is applied to the output, the BOOST needs to restart and cannot respond to the load in time, resulting in a significant drop in output voltage.

[0003] Existing technology CN 118739199 B discloses an undervoltage protection circuit for a switching power supply, aiming to solve the problem of misjudgment that may occur when the system switches from a load state to an no-load state in the prior art. This solution introduces a current processing module, a comparison module, a timing module, a falling edge acquisition module, and an arithmetic module, combined with the falling edge detection of the main switching transistor's switching signal, to generate a more accurate undervoltage protection signal. However, while it avoids misjudgment by presetting the detection time (e.g., 40-80ms) and performing logical operations through the timing module, this may introduce a delay. For example, when the input voltage fluctuates rapidly, the undervoltage protection signal needs to wait for the falling edge sampling signal and the timing result to perform logical operations, which may prevent it from responding to transient undervoltage events in a timely manner, resulting in an inability to respond promptly to sudden load increases. Summary of the Invention

[0004] To address the technical problem of existing technologies having high standby current and being unable to respond promptly to sudden load increases, this application provides a method for optimizing standby current of a DC-DC converter, an output circuit, and a DC-DC converter. The output circuit includes a power supply, a BOOST circuit, and a forward circuit and a flyback circuit electrically connected to the BOOST circuit, respectively. The power supply is connected to the BOOST circuit and the flyback circuit respectively; The BOOST circuit is used to output a first voltage signal to the forward converter circuit; The flyback circuit is electrically connected to the BOOST circuit and the forward circuit through a current-limiting resistor, and is used to output a second voltage signal to the forward circuit and feed the second voltage signal back to the BOOST circuit. When there is no load, the second voltage signal is greater than the first voltage signal, the duty cycle of the BOOST circuit is set to zero, and the forward converter operates under the control of the second voltage signal. When a sudden load is applied, the flyback circuit temporarily supplies power to the load. The second voltage signal is immediately pulled down by the sudden load, and the second voltage signal is less than or equal to the first voltage signal. The BOOST circuit starts and controls the forward circuit to work with the first voltage signal.

[0005] The circuit provided in this application uses a flyback circuit to supply power during no-load conditions, replacing the BURST mode standby of the BOOST circuit, thus maintaining power supply in standby mode and effectively reducing standby current. Simultaneously, when a sudden load is applied, the flyback circuit can temporarily boost the circuit's output voltage, providing response time for the BOOST circuit to start up and ensuring that the converter's output voltage does not drop excessively during BOOST circuit startup. The circuit achieves load response by adding a current-limiting resistor R1 at the output of the flyback circuit, thereby reducing standby current while ensuring responsiveness to sudden load applications at low cost.

[0006] The DC-DC converter standby current optimization method provided by this invention includes the following steps: Real-time acquisition of the first voltage signal output by the BOOST circuit and the second voltage signal output by the flyback circuit; When the second voltage signal is greater than the first voltage signal, the duty cycle of the BOOST circuit is set to 0, and the circuit enters standby mode, where it is powered by the flyback circuit. When the second voltage signal is less than or equal to the first voltage signal, the BOOST circuit is activated, the duty cycle of the BOOST circuit is restored to the required value, and the BOOST circuit provides power.

[0007] The above method determines the circuit's operating mode by real-time monitoring of the first voltage signal output by the BOOST circuit and the second voltage signal output by the flyback circuit. When the second voltage signal is greater than the first voltage signal, it indicates a light load or no-load condition. The duty cycle of the BOOST circuit is set to 0, stopping its switching action and entering a low-power standby mode. The power supply for the entire system is entirely handled by the flyback circuit, significantly reducing the overall circuit's standby power consumption. Conversely, when the second voltage signal drops to less than or equal to the first voltage signal, it indicates a sudden increase in load. The flyback circuit's output capability is insufficient to maintain the system's normal power supply requirements, only maintaining the output voltage for a short period. In this case, the BOOST circuit is immediately activated, restoring its duty cycle to the set value that meets the current load requirements. The BOOST circuit then takes over the main power supply task, ensuring the stability of the DC-DC converter's output voltage and the reliable operation of the load, improving the stability of the output circuit and its response speed to sudden load changes. Attached Figure Description

[0008] Figure 1 This is a schematic diagram of the overall structure of the output circuit provided by the present invention.

[0009] Figure 2 This is an overall flowchart of the method provided by the present invention. Detailed Implementation

[0010] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example 1

[0011] refer to Figure 1 The present invention provides a DC-DC converter output circuit, including: a power supply, a BOOST circuit, a forward circuit, a flyback circuit, and a current-limiting resistor R1.

[0012] The power supply is connected to the BOOST circuit and the flyback circuit respectively to supply power to the BOOST circuit and the flyback circuit. The BOOST circuit is used to output the first voltage signal HV1 to the forward converter circuit.

[0013] The flyback circuit is used to output the second voltage signal HV2 to the forward circuit and feed the second voltage signal HV2 back to the BOOST circuit. The flyback circuit is connected to the BOOST circuit and the forward circuit through a current-limiting resistor.

[0014] The forward converter circuit is used to output current to the load terminal V0+ according to the first voltage signal HV1 or the second voltage signal HV2.

[0015] When unloaded, the second voltage signal HV2 is greater than the first voltage signal HV1, the duty cycle of the BOOST circuit is set to zero, the forward converter operates under the control of the second voltage signal HV2, and the switching power supply enters standby mode, effectively reducing standby current.

[0016] When a sudden load is applied, the flyback circuit temporarily supplies power to the load, increasing the load current. The second voltage signal HV2 is immediately pulled down by the sudden load, and the second voltage signal HV2 drops to less than or equal to the first voltage signal HV1. The BOOST circuit starts and sends the first voltage signal HV1 to the forward circuit. Under the control of the first voltage signal HV1, the forward circuit supplies power to the load, completing the conversion from power supply by the flyback circuit to power supply by the BOOST circuit.

[0017] The circuit provided in this application uses a flyback circuit to supply power during no-load conditions, replacing the BURST mode standby of the BOOST circuit, thus maintaining power supply in standby mode and effectively reducing standby current. Simultaneously, when a sudden load is applied, the flyback circuit can temporarily boost the circuit's output voltage, providing response time for the BOOST circuit to start up and ensuring that the converter's output voltage does not drop excessively during BOOST circuit startup. The circuit achieves load response by adding a current-limiting resistor R1 at the output of the flyback circuit, thereby reducing standby current while ensuring responsiveness to sudden load applications at low cost.

[0018] Furthermore, the above output circuit also includes a reverse protection diode D connected in series with the current limiting resistor R1, which is used to prevent reverse current (first voltage signal) from being input into the flyback circuit when the second voltage signal is suddenly pulled down by the load, so as to protect the flyback circuit.

[0019] By using the anti-reverse diode D and the current-limiting resistor R1 to limit the peak current between the flyback circuit and the forward circuit, the overload current can be prevented from impacting the circuit, and the reverse current can be effectively avoided from damaging the circuit components, thereby improving the reliability of the entire system.

[0020] This application also provides a DC-DC converter employing the above-described output circuit. Example 2

[0021] Based on the output circuit provided in Embodiment 1, this application also provides a method for optimizing the standby current of a DC-DC converter, referencing... Figure 2 This includes the following steps: S1. Real-time acquisition of the first voltage signal HV1 output by the BOOST circuit and the second voltage signal HV2 output by the flyback circuit; S2. When the second voltage signal HV2 is greater than the first voltage signal HV1, the duty cycle of the BOOST circuit is set to 0, and it enters standby mode, powered by the flyback circuit. S3. When the second voltage signal HV2 is less than or equal to the first voltage signal HV1, the BOOST circuit starts, the duty cycle of the BOOST circuit is restored to the required value, and the BOOST circuit provides power.

[0022] The above method uses real-time monitoring of the first voltage signal HV1 output by the BOOST circuit and the second voltage signal HV2 output by the flyback circuit to determine the circuit's operating mode. When the second voltage signal HV2 output by the flyback circuit is sufficiently high (i.e., greater than the first voltage signal HV1 output by the BOOST circuit), it indicates a light load or an unloaded state. In this case, the flyback circuit has the capability to independently provide stable power to subsequent circuits, and the BOOST circuit does not need to continue operating. Therefore, the duty cycle of the BOOST circuit is set to 0, causing it to stop switching and enter a low-power standby mode, with the entire system's power supply handled entirely by the flyback circuit. In this way, the BOOST circuit, having stopped operating, no longer consumes additional drive current and switching losses, thus significantly reducing the overall circuit's standby power consumption. Conversely, when the second voltage signal HV2 output by the flyback circuit drops to less than or equal to the first voltage signal HV1 output by the BOOST circuit, it indicates that the output capability of the flyback circuit may be insufficient to maintain the normal power supply requirements of the system. This means there may be a sudden load increase at the load end. In this case, the BOOST circuit is immediately activated, restoring its duty cycle to the set value that meets the current load requirements. The BOOST circuit then takes over the main power supply task again, ensuring the stability of the DC-DC converter output voltage and the reliable operation of the load. This dynamic switching of the BOOST circuit's operating state minimizes energy consumption during non-essential operating periods while ensuring power supply continuity, effectively optimizing standby current.

[0023] Furthermore, in the aforementioned standby current optimization process, if the duty cycle of the BOOST circuit is immediately set to 0 whenever the second voltage signal HV2 is greater than the first voltage signal HV1, it will cause the BOOST circuit to be frequently turned off. Especially in some scenarios where the load changes frequently, the frequent start and stop of the BOOST circuit will cause the entire circuit to be subjected to frequent current surges, reducing the service life of the circuit.

[0024] Based on the above analysis, when the second voltage signal HV2 is greater than the first voltage signal HV1, the duty cycle of the BOOST circuit gradually decreases to 0 during the soft turn-off period.

[0025] Specifically, the soft turn-off period is related to the specific design parameters of the DC-DC converter's output circuit, that is, it is determined by both the minimum turn-off time and the maximum turn-off time.

[0026] The minimum turn-off time is primarily determined by the output capacitance and load characteristics, with the aim of preventing excessive voltage overshoot during the turn-off process. When the BOOST circuit suddenly stops delivering energy, the remaining energy in the inductor and the energy stored in the output capacitor (output capacitor C_out) will discharge to the load. If the load is very light (e.g., no load), this energy has nowhere to be released, causing the output voltage HV1 to rise, resulting in voltage overshoot. Therefore, it is necessary to limit the minimum turn-off time of the BOOST circuit.

[0027] The maximum shutdown time is primarily determined by the target standby power consumption and system response speed requirements. If the load is frequently started and stopped, the BOOST circuit should not be frequently shut down and should always maintain a response to the load. Furthermore, since the total no-load standby time accounts for a small percentage of the total power consumption in industrial vehicles, the power consumption in standby mode is not significant, making power saving insignificant. Instead, it is more important to maintain the BOOST circuit's responsiveness to frequently changing loads. Therefore, the soft shutdown period should be appropriately extended to ensure timely response to the load. If the load is not frequently shut down and the average no-load time is long, reducing standby power consumption should be the primary goal; therefore, the soft shutdown period should be set to the minimum shutdown time.

[0028] Specifically, the soft shutdown period can be determined through the following steps: First, determine the load mode of the industrial vehicle. If the load mode of the industrial vehicle is high-frequency load mode, set the soft shutdown cycle to the maximum shutdown time. If the load mode of the industrial vehicle is low-frequency load mode, set the soft shutdown cycle to the minimum shutdown time.

[0029] Generally, the minimum turn-off time can be set to 0.1s-0.5s, with the specific value depending on the circuit's design parameters. The maximum turn-off time can be set to 3-5s, or it can be appropriately extended, depending on the specific application scenario.

[0030] Specifically, the no-load threshold is determined by measuring the circuit's loss under no-load conditions, generally based on the measured no-load loss amplified by a safety factor. For example, if the actual measured no-load loss is P0, and the safety factor is set to k (k is usually greater than 1 and can be adjusted according to the circuit design margin and the stability requirements of the actual application scenario, such as taking 1.2~1.5), then the no-load threshold P_th can be set as P_th = k * P0. This setting effectively avoids misjudging a brief low-power state during normal load fluctuations as no-load, while ensuring that the true no-load state is accurately identified, providing a reliable basis for subsequent no-load cycle statistics.

[0031] Furthermore, in step S2, when the second voltage signal HV2 is greater than the first voltage signal HV1, there is still a possibility of abnormal current fluctuations in the circuit, causing the BOOST circuit to incorrectly start the standby state. Therefore, it can be further confirmed whether it is in an unloaded state, specifically including the following steps: S4. Obtain the load current and load voltage, and calculate the load power; S5. When the second voltage signal HV2 is greater than the first voltage signal HV1, determine whether the load power is less than the no-load threshold. If so, set the duty cycle of the BOOST circuit to 0; otherwise, return to step S1.

[0032] By calculating the output power at the load end, the system determines whether the changes in the second voltage signal HV2 and the first voltage signal HV1 are caused by load changes, thus avoiding misjudgments caused by non-load change factors such as abnormal current fluctuations in the circuit. Specifically, when the system detects that the second voltage signal HV2 is greater than the first voltage signal HV1, it does not directly enter standby mode, but first initiates the detection of the actual operating conditions at the load end. By collecting the two key parameters of load end current and voltage in real time, and accurately calculating the real-time output power of the current load end according to the power calculation formula (power = current × voltage), the system compares this calculated load end power with a preset no-load threshold. Only when the real-time power value is indeed less than the no-load threshold and meets the duration requirement (for example, a short confirmation period can be set to ensure that the power value is stably lower than the threshold rather than fluctuating instantaneously), will the system determine that the voltage change is caused by the load being reduced to a no-load or near-no-load state, and then execute the operation of setting the duty cycle of the BOOST circuit to 0, so that the circuit enters a low-power standby mode. Conversely, if the calculated load power is greater than or equal to the no-load threshold, it indicates that the phenomenon of the second voltage signal HV2 being greater than the first voltage signal HV1 is not caused by the no-load condition, but may be due to a temporary voltage fluctuation caused by a momentary current spike or other interference factors. In this case, the system will ignore this voltage change and return to step S1 to continue to monitor the first voltage signal HV1 and the second voltage signal HV2 in real time, thereby ensuring that the BOOST circuit only enters the standby state under true no-load conditions. This effectively improves the accuracy and reliability of standby state judgment and avoids the impact of unnecessary standby switching on circuit stability and load power supply continuity.

[0033] In summary, compared with existing technologies, the method provided in this application significantly improves the accuracy of standby state identification by introducing a judgment mechanism based on load power. Existing technologies often trigger standby mode based solely on simple comparisons of voltage signals or a single current threshold, which is easily susceptible to misjudgments caused by instantaneous interference or load fluctuations. This leads to the circuit frequently entering standby mode under non-true no-load conditions or failing to switch in time when truly no-load, affecting system stability and energy utilization efficiency. This application, however, by real-time acquisition and calculation of the load power value, combined with preset no-load thresholds and duration confirmation conditions, can effectively filter out false no-load signals caused by interference factors such as current spikes and voltage fluctuations. It ensures that the BOOST circuit only enters low-power standby mode when the load truly drops to no-load or near-no-load state and remains stable. This power-based judgment method better aligns with the actual operating state changes of the load, fundamentally solving the limitations of traditional single-parameter judgments of voltage or current. This makes standby state switching more reliable and intelligent, further reducing unnecessary energy loss, while ensuring the continuity and stability of load power supply, and improving the overall performance of the DC-DC converter and user experience.

[0034] In conclusion, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A DC-DC converter output circuit, characterized in that, include: Power supply, BOOST circuit, and forward and flyback circuits electrically connected to the BOOST circuit respectively; The power supply is connected to the BOOST circuit and the flyback circuit respectively; The BOOST circuit is used to output a first voltage signal to the forward converter circuit; The flyback circuit is electrically connected to the BOOST circuit and the forward circuit through a current-limiting resistor, and is used to output a second voltage signal to the forward circuit and feed the second voltage signal back to the BOOST circuit. When there is no load, the second voltage signal is greater than the first voltage signal, the duty cycle of the BOOST circuit is set to zero, and the forward converter operates under the control of the second voltage signal. When a sudden load is applied, the flyback circuit temporarily supplies power to the load. The second voltage signal is immediately pulled down by the sudden load, and the second voltage signal is less than or equal to the first voltage signal. The BOOST circuit starts and controls the forward circuit to work with the first voltage signal.

2. The output circuit according to claim 1, characterized in that, The output circuit also includes a reverse protection diode connected in series with the current limiting resistor. The reverse protection diode is used to prevent the first voltage signal from entering the flyback circuit when the second voltage signal is pulled down by a sudden load.

3. A method for optimizing the standby current of a DC-DC converter, characterized in that, Includes the following steps: Real-time acquisition of the first voltage signal output by the BOOST circuit and the second voltage signal output by the flyback circuit; When the second voltage signal is greater than the first voltage signal, the duty cycle of the BOOST circuit is set to 0, and the circuit enters standby mode, where it is powered by the flyback circuit. When the second voltage signal is less than or equal to the first voltage signal, the BOOST circuit is activated, the duty cycle of the BOOST circuit is restored to the required value, and the BOOST circuit provides power.

4. The method according to claim 3, characterized in that, When the second voltage signal is greater than the first voltage signal, the duty cycle of the BOOST circuit gradually decreases to 0 during the soft-shutdown period.

5. The method according to claim 4, characterized in that, The soft shutdown period is determined by both the minimum shutdown time and the maximum shutdown time.

6. The method according to claim 3 or 4, characterized in that, It also includes the following steps: Obtain the load current and load voltage, and calculate the load power. When the second voltage signal is greater than the first voltage signal, it is determined whether the power of the load terminal is less than the no-load threshold. If so, the duty cycle of the BOOST circuit is set to 0.

7. A DC-DC converter, characterized in that, The output circuit described in claims 1-2 is used.

8. A DC-DC converter, characterized in that, The standby current optimization method described in claims 3-6 is adopted.

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