Isolated dc-dc converter and hiccup control method

Abstract

The application discloses an isolated DC-DC converter and hiccup control method, comprising: a power conversion circuit, a driving circuit and a controller; the controller is used for obtaining a first error result of an output voltage and a reference voltage of the isolated DC-DC converter and a second error result of an output current and a reference current of the isolated DC-DC converter, adjusting a hiccup duration according to the first error result and the second error result; generating a driving instruction according to the hiccup duration and giving the driving circuit; the driving circuit is used for outputting a driving signal to drive a switch tube in the power conversion circuit. The output voltage and the output current are compared with corresponding reference values respectively to obtain corresponding comparison results, and the hiccup duration is adjusted according to the two comparison results, so that the output voltage and the output current are considered, and the performance of the isolated DC-DC converter is ensured without too high power consumption.

Description

Technical Field

[0001] This application relates to the field of power electronics technology, specifically to an isolated DC-DC converter and a hiccup control method. Background Technology

[0002] An isolated DC-DC converter is an isolated switching power supply. Taking an LLC resonant DC-DC converter as an example, it can be classified as a full-bridge LLC resonant DC-DC converter or a half-bridge LLC resonant DC-DC converter, depending on the circuit topology connected to the primary winding of the transformer. The form of the rectifier circuit connected to the secondary winding of the transformer is not limited. The output of the LLC resonant DC-DC converter is DC, and due to the isolation provided by the transformer, it can effectively isolate interference signals.

[0003] In practical applications, the higher the output voltage of an isolated DC-DC converter, the higher the switching frequency, and the greater the losses of the switching transistors. Higher losses also lead to more heat generation and a greater risk of transistor damage. Therefore, the switching frequency should be kept as low as possible at high output voltage points. Specifically, to reduce the output voltage, the isolated DC-DC converter can be controlled to operate in hiccup mode. Hiccup mode, also known as intermittent operation, is used because isolated DC-DC converters typically control output voltage and current through frequency modulation. Although the frequency modulation range is wide, under light load or no-load conditions, even at maximum frequency, the set voltage or current value may still be exceeded. In this case, intermittent operation mode is needed to control the output voltage and current within the set values. To increase the output voltage, the isolated DC-DC converter can be controlled to operate in continuous mode. In continuous mode, hiccup is not required; the output voltage and current can be controlled within the set values ​​simply by adjusting the frequency.

[0004] In existing technologies, the switching between hiccup mode and continuous mode is controlled solely by the output voltage of the isolated DC-DC converter. This method cannot provide precise control, resulting in large output ripple and an inability to effectively balance performance and losses. Summary of the Invention

[0005] In view of this, this application provides an isolated DC-DC converter and a hiccup control method, which can precisely control hiccups and balance the relationship between the performance and losses of the isolated DC-DC converter.

[0006] This application provides an isolated DC-DC converter, including: a power conversion circuit, a drive circuit, and a controller;

[0007] The controller is used to obtain a first error result of the output voltage and reference voltage of the isolated DC-DC converter, and a second error result of the output current and reference current of the isolated DC-DC converter; adjust the hiccup duration according to the first error result and the second error result; and generate a drive command for the drive circuit according to the hiccup duration.

[0008] The driving circuit is used to output driving signals to drive the switching transistors in the power conversion circuit.

[0009] Preferably, the controller is specifically configured to adjust the hiccup duration based on the second error result when the first error result is greater than the second error result; adjust the hiccup duration based on the first error result when the first error result is less than the second error result; and adjust the hiccup duration based on either the first or second error result when the first error result is equal to the second error result.

[0010] Preferably, the controller is specifically configured to, when the first error result is greater than the second error result, shorten the hiccup duration if the output current is greater than the reference current, and increase the hiccup duration if the output current is less than the reference current.

[0011] Preferably, the controller is specifically configured to, when the first error result is less than the second error result, shorten the hiccup duration if the output voltage is greater than the reference voltage, and increase the hiccup duration if the output voltage is less than the reference voltage.

[0012] Preferably, the controller is specifically configured to obtain a first adjustment duration based on a first error result, obtain a second adjustment duration based on a second error result, and adjust the hiccup duration based on the smaller of the first adjustment duration and the second adjustment duration.

[0013] Preferably, the controller is also used to control the hiccup frequency based on the output voltage.

[0014] Preferably, the controller is specifically used to find the switching frequency corresponding to the minimum loss based on the output voltage, and to control the hiccup frequency based on the switching frequency, since the output voltage has different losses at different switching frequencies.

[0015] Preferably, the controller is also configured to switch from hiccup mode to continuous mode when the hiccup duration is greater than the control cycle for N consecutive cycles; N is greater than or equal to 2.

[0016] This application also provides a hiccup control method for an isolated DC-DC converter, including:

[0017] Obtain the first error results for the output voltage and reference voltage of the isolated DC-DC converter, and the second error results for the output current and reference current of the isolated DC-DC converter;

[0018] The hiccup duration is adjusted based on the first and second error results; a drive command is generated based on the hiccup duration and sent to the drive circuit; so that the drive circuit outputs a drive signal to drive the switching transistor in the power conversion circuit.

[0019] Preferably, adjusting the hiccup duration based on the first error result and the second error result specifically includes:

[0020] The first error result is greater than the second error result, so the hiccup duration is adjusted based on the second error result;

[0021] The first error result is smaller than the second error result, so the hiccup duration is adjusted based on the first error result;

[0022] The first error result is equal to the second error result, and the hiccup duration is adjusted based on the first error result or the second error result.

[0023] Preferably, the first error result is greater than the second error result, and the hiccup duration is adjusted according to the second error result, specifically including:

[0024] When the first error result is greater than the second error result, if the output current is greater than the reference current, the hiccup duration is shortened; if the output current is less than the reference current, the hiccup duration is increased.

[0025] Preferably, the first error result is smaller than the second error result, and the hiccup duration is adjusted according to the first error result, specifically including:

[0026] When the first error result is less than the second error result, if the output voltage is greater than the reference voltage, the hiccup duration is shortened; if the output voltage is less than the reference voltage, the hiccup duration is increased.

[0027] Preferably, adjusting the hiccup duration based on the first error result and the second error result specifically includes:

[0028] The first adjustment duration is obtained based on the first error result, and the second adjustment duration is obtained based on the second error result;

[0029] The hiccup duration is adjusted based on the smaller of the first and second adjustment durations.

[0030] Preferably, it further includes controlling the hiccup frequency based on the output voltage.

[0031] Preferably, the hiccup frequency is controlled according to the output voltage, specifically including:

[0032] Find the switching frequency with the minimum loss based on the output voltage, and control the hiccup frequency based on the switching frequency. The output voltage corresponds to different losses at different switching frequencies.

[0033] Preferably, it further includes: when the hiccup duration is greater than the control period for N consecutive cycles, switching from hiccup mode to continuous mode; N is greater than or equal to 2.

[0034] Therefore, this application has the following beneficial effects:

[0035] The isolated DC-DC converter provided in this application samples the output voltage and output current in real time, compares the output voltage and output current with the corresponding reference values, obtains the corresponding comparison results, and adjusts the hiccup duration based on the two comparison results. This takes into account both the output voltage and the output current, thereby ensuring the performance of the isolated DC-DC converter without causing excessive power consumption. Attached Figure Description

[0036] Figure 1 A schematic diagram of an isolated DC-DC converter provided in an embodiment of this application;

[0037] Figure 2 A control principle diagram provided for an embodiment of this application;

[0038] Figure 3 Another control principle diagram provided for an embodiment of this application;

[0039] Figure 4 Another control principle diagram provided in the embodiments of this application;

[0040] Figure 5 Another control principle diagram provided for embodiments of this application;

[0041] Figure 6 A flowchart illustrating a hiccup control method for an isolated DC-DC converter provided in an embodiment of this application. Detailed Implementation

[0042] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the embodiments of this application will be further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0043] In practical applications, the higher the output voltage and the higher the switching frequency of an isolated DC-DC converter, the greater the losses of the switching transistors. The greater the losses of the switching transistors, the higher the risk of transistor damage. Therefore, when the output voltage is high, the switching frequency should not be too high.

[0044] To balance the performance and losses of isolated DC-DC converters, the technical solution provided in this application does not control hiccups solely based on the output voltage of the isolated DC-DC converter, but rather controls hiccups by combining both the output voltage and output current. The hiccup duration is adjusted based on comparisons of the output voltage and output current with their corresponding reference values.

[0045] For the same output voltage, different output currents result in different hiccup times. The magnitude of the output current corresponds to the load size. For the same output voltage, under heavy load, the switching frequency is low, and hiccup may not occur; under light load, the switching frequency is high, and hiccup will occur.

[0046] Therefore, the technical solution provided in this application embodiment controls the hiccup duration by jointly controlling the output voltage and output current, which can take into account both the performance and loss of the isolated DC-DC converter.

[0047] See Figure 1 The figure is a schematic diagram of an isolated DC-DC converter provided in an embodiment of this application.

[0048] The isolated DC-DC converter provided in this embodiment includes: a power conversion circuit 300, a drive circuit 200, and a controller 100;

[0049] The controller 100 is used to obtain a first error result of the output voltage and reference voltage of the isolated DC-DC converter, and a second error result of the output current and reference current of the isolated DC-DC converter; adjust the hiccup duration according to the first error result and the second error result; and generate a drive command for the drive circuit 200 according to the hiccup duration.

[0050] It should be understood that the reference voltage and reference current are preset values, and the first error result can be positive or negative; similarly, the second error result can be positive or negative.

[0051] One possible implementation is to adjust the hiccup duration based on the smaller of the first and second error results. Specifically, the smaller of the two error results can be obtained first, or the control algorithm can be calculated first, and then the results of the two calculations can be compared.

[0052] In addition, the duration of hiccups can be adjusted to either lengthen or shorten them. The specific adjustment can be made by adjusting the hiccup duration in a closed loop based on the magnitude of the error result.

[0053] The isolated DC-DC converter provided in this application sample the output voltage and output current in real time, compares the output voltage and output current with the corresponding reference values, obtains the corresponding comparison results, and adjusts the hiccup duration based on the two comparison results. This takes into account both the output voltage and the output current, thereby ensuring the performance of the isolated DC-DC converter without causing excessive power consumption.

[0054] The drive circuit 200 is used to output a drive signal to drive the switching transistor in the power conversion circuit 300.

[0055] It should be understood that the switching transistor in the power conversion circuit 300 is generally a controllable switching transistor, which needs to be driven to turn on or off by a drive signal. The controller 100 cannot directly drive the switching transistor to operate. Therefore, the drive circuit 200 needs to drive the switching transistor to operate according to the drive signal.

[0056] See Figure 2 This figure is a control principle diagram provided in an embodiment of this application.

[0057] The isolated DC-DC converter provided in this application embodiment can control not only the duration of each hiccup, but also the frequency of hiccups. This will be described in detail below.

[0058] The technical solution provided in this application embodiment controls the hiccup duration by outputting voltage and outputting current, and controls the hiccup frequency by outputting voltage.

[0059] The hardware requires an output voltage sampling circuit and an output current sampling circuit.

[0060] The output voltage sampled by the output voltage sampling circuit is compared with the reference voltage.

[0061] Below are two specific methods for adjusting hiccup duration based on the first error result and the second error result.

[0062] The first type:

[0063] First, find the smaller of the two error results, and then determine the hiccup duration that needs to be adjusted based on the smaller value.

[0064] The controller is specifically used to adjust the hiccup duration based on the second error result when the first error result is greater than the second error result; to adjust the hiccup duration based on the first error result when the first error result is less than the second error result; and to adjust the hiccup duration based on either the first or second error result when the first error result is equal to the second error result.

[0065] Specifically, the controller is used to shorten the hiccup duration and thus reduce the output current when the first error result is greater than the second error result and the output current is greater than the reference current; and to increase the hiccup duration and thus increase the output current when the output current is less than the reference current.

[0066] The controller is specifically designed to reduce the output voltage by shortening the hiccup duration when the first error result is less than the second error result and the output voltage is greater than the reference voltage; and to increase the output voltage by increasing the hiccup duration when the output voltage is less than the reference voltage.

[0067] The above analysis shows that by adjusting the hiccup duration, the output voltage can be maintained near the reference voltage, and the output current can be maintained near the reference current, thereby ensuring the stability of the isolated DC-DC converter.

[0068] The second method will be introduced below:

[0069] See Figure 3 This figure is another control principle diagram provided in an embodiment of this application.

[0070] The technical solution provided in this embodiment is to first obtain the corresponding adjustment duration based on the two error results, and then take the smaller value to adjust the hiccup duration.

[0071] The controller is specifically used to obtain a first adjustment duration based on a first error result, obtain a second adjustment duration based on a second error result, and adjust the hiccup duration based on the smaller value between the first adjustment duration and the second adjustment duration.

[0072] Specifically, the method for obtaining the adjustment duration based on the error results is the same as... Figure 2 The descriptions are similar, so I will not repeat them here.

[0073] The technical solution provided in this application not only adjusts the duration of hiccups, but also adjusts the frequency of hiccups, which will be described below with reference to the accompanying drawings.

[0074] See Figure 4 This figure is another control principle diagram provided in the embodiment of this application.

[0075] The controller is also used to control the hiccup frequency based on the output voltage.

[0076] Figure 4 Only in Figure 2 Based on this, a control path for determining the hiccup frequency based on the output voltage has been added. Additionally, it should be understood that... Figure 4 You can also Figure 3 Based on this, a control path for the hiccup frequency based on the output voltage is added. See [link / reference] for details. Figure 5 This will not be elaborated upon here.

[0077] Specifically, the controller can obtain the hiccup frequency based on the output voltage through control algorithm 3. Specifically, it can be a PID or PI control algorithm, etc., without being specifically limited here.

[0078] The controller is specifically used to find the switching frequency with the minimum loss based on the output voltage, and to control the hiccup frequency based on the switching frequency. The output voltage has different losses at different switching frequencies.

[0079] Specifically, based on the characteristics of the actual circuit, the switching frequency with low loss corresponding to different voltage points of the output voltage can be tested. This switching frequency is used as the hiccup frequency f of the output voltage, which is also the maximum adjustable frequency point in the current continuous output voltage mode. Compared with the traditional method of using the highest frequency point as a fixed hiccup frequency point, the technical solution provided in this application can more effectively reduce losses by adjusting the hiccup frequency according to local conditions, thereby improving the power conversion efficiency of the isolated DC-DC converter.

[0080] The controller is also used to switch from hiccup mode to continuous mode when the hiccup duration is greater than the control cycle for N consecutive cycles; N is greater than or equal to 2.

[0081] The duration of hiccups serves as an indicator for switching from hiccup mode to continuous operation. If the duration of hiccups is greater than the control period T for N consecutive cycles, it indicates that it is necessary to switch to continuous operation mode.

[0082] Hiccup frequency serves as an indicator for switching from continuous mode to hiccup mode. When working in continuous mode, if the control frequency is found to be higher than the hiccup frequency for M consecutive cycles, it indicates that it is necessary to switch to hiccup mode.

[0083] N and M can be adjusted according to requirements until the requirements are met.

[0084] The isolated DC-DC converter provided in this application embodiment effectively reduces switching losses and improves product efficiency through a frequency conversion hiccup scheme without increasing hardware costs. In the frequency conversion hiccup method, the hiccup time and hiccup frequency are controllable. The hiccup frequency is adjusted in real time by adjusting the output voltage, and the hiccup duration is adjusted in real time according to the errors in the output current and output voltage, thereby simultaneously taking into account switching losses and the range of continuous mode.

[0085] Based on the hiccup control method for an isolated DC-DC converter provided in the above embodiments, this application also provides a method, which will be described in detail below with reference to the accompanying drawings.

[0086] See Figure 6 The figure is a flowchart of a hiccup control method for an isolated DC-DC converter provided in an embodiment of this application.

[0087] The hiccup control method for the isolated DC-DC converter provided in this embodiment includes:

[0088] S601: Obtain the first error results of the output voltage and reference voltage of the isolated DC-DC converter, and the second error results of the output current and reference current of the isolated DC-DC converter;

[0089] S602: Adjust the hiccup duration according to the first error result and the second error result; generate a drive command for the drive circuit according to the hiccup duration; so that the drive circuit outputs a drive signal to drive the switching transistor in the power conversion circuit.

[0090] The hiccup control method for isolated DC-DC converters provided in this application sample the output voltage and output current in real time, compare the output voltage and output current with the corresponding reference values ​​respectively, obtain the corresponding comparison results, and adjust the hiccup duration based on the two comparison results. This method takes into account both the output voltage and the output current, thereby ensuring the performance of the isolated DC-DC converter without causing excessive power consumption.

[0091] Below are two specific ways to adjust the duration of hiccups.

[0092] The first type:

[0093] Adjusting the hiccup duration based on the first and second error results, specifically including:

[0094] The first error result is greater than the second error result, so the hiccup duration is adjusted based on the second error result;

[0095] The first error result is smaller than the second error result, so the hiccup duration is adjusted based on the first error result;

[0096] The first error result is equal to the second error result, and the hiccup duration is adjusted based on the first error result or the second error result.

[0097] The first error result is greater than the second error result. The hiccup duration is adjusted based on the second error result, specifically including:

[0098] When the first error result is greater than the second error result, if the output current is greater than the reference current, the hiccup duration is shortened; if the output current is less than the reference current, the hiccup duration is increased.

[0099] The first error result is smaller than the second error result. The hiccup duration is adjusted based on the first error result, specifically including:

[0100] When the first error result is less than the second error result, if the output voltage is greater than the reference voltage, the hiccup duration is shortened; if the output voltage is less than the reference voltage, the hiccup duration is increased.

[0101] The second type:

[0102] Adjusting the hiccup duration based on the first error result and the second error result specifically includes: obtaining a first adjustment duration based on the first error result, obtaining a second adjustment duration based on the second error result, and adjusting the hiccup duration based on the smaller value between the first adjustment duration and the second adjustment duration.

[0103] The method provided in this application embodiment can adjust not only the duration of hiccups, but also the frequency of hiccups.

[0104] The method provided in this embodiment also includes: controlling the hiccup frequency based on the output voltage.

[0105] The hiccup frequency is controlled based on the output voltage. Specifically, this involves finding the switching frequency with the minimum loss based on the output voltage, and controlling the hiccup frequency based on the switching frequency. The loss corresponding to the output voltage is different at different switching frequencies.

[0106] The method provided in this application embodiment also includes:

[0107] When the duration of hiccups exceeds the control period for N consecutive cycles, switch from hiccup mode to continuous mode; N is greater than or equal to 2.

[0108] The hiccup control method for isolated DC-DC converters provided in this application effectively reduces switching losses and improves product efficiency through a frequency conversion hiccup scheme. In the frequency conversion hiccup method, two parameters, hiccup time and hiccup frequency, can be controlled. The hiccup frequency is adjusted in real time by adjusting the output voltage, and the hiccup duration is adjusted in real time according to the errors in the output current and output voltage, thereby simultaneously taking into account switching losses and the range of continuous mode.

[0109] It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the systems or apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the descriptions are relatively simple, and relevant parts can be referred to the method section.

[0110] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An isolated DC-DC converter, characterized in that, include: Power conversion circuit, drive circuit, and controller; The controller is used to obtain a first error result of the output voltage and reference voltage of the isolated DC-DC converter, and a second error result of the output current and reference current of the isolated DC-DC converter; The hiccup duration is adjusted based on the smaller of the first error result and the second error result, or a first adjustment duration is obtained based on the first error result, a second adjustment duration is obtained based on the second error result, and the hiccup duration is adjusted based on the smaller of the first adjustment duration and the second adjustment duration. A driving instruction is generated and sent to the driving circuit based on the hiccup duration; The driving circuit is used to output a driving signal to drive the switching transistor in the power conversion circuit.

2. The converter according to claim 1, characterized in that, The controller adjusts the hiccup duration based on the smaller of the first error result and the second error result, specifically including: if the first error result is greater than the second error result, adjusting the hiccup duration based on the second error result; if the first error result is less than the second error result, adjusting the hiccup duration based on the first error result; if the first error result is equal to the second error result, adjusting the hiccup duration based on either the first error result or the second error result.

3. The converter according to claim 2, characterized in that, Specifically, when the first error result is greater than the second error result, if the output current is greater than the reference current, the hiccup duration is shortened; if the output current is less than the reference current, the hiccup duration is increased.

4. The converter according to claim 2, characterized in that, Specifically, the controller is configured to, when the first error result is less than the second error result, shorten the hiccup duration if the output voltage is greater than the reference voltage, and increase the hiccup duration if the output voltage is less than the reference voltage.

5. The converter according to claim 1, characterized in that, The controller is also used to control the hiccup frequency based on the output voltage.

6. The converter according to claim 5, characterized in that, The controller is specifically used to find the switching frequency with the minimum loss based on the output voltage, and to control the hiccup frequency based on the switching frequency. The output voltage has different losses at different switching frequencies.

7. The converter according to any one of claims 1-6, characterized in that, The controller is further configured to switch from hiccup mode to continuous mode when the hiccup duration is greater than the control cycle for N consecutive cycles; where N is greater than or equal to 2.

8. A method for controlling hiccups in an isolated DC-DC converter, characterized in that, The isolated DC-DC converter includes a drive circuit and a power conversion circuit, and the method includes: Obtain a first error result for the output voltage and reference voltage of the isolated DC-DC converter, and a second error result for the output current and reference current of the isolated DC-DC converter; The hiccup duration is adjusted according to the smaller of the first error result and the second error result, or a first adjustment duration is obtained according to the first error result, a second adjustment duration is obtained according to the second error result, and the hiccup duration is adjusted according to the smaller of the first adjustment duration and the second adjustment duration; a drive command is generated according to the hiccup duration and sent to the drive circuit; so that the drive circuit outputs a drive signal to drive the switching transistor in the power conversion circuit.

9. The method according to claim 8, characterized in that, The step of adjusting the hiccup duration based on the smaller of the first error result and the second error result specifically includes: If the first error result is greater than the second error result, the hiccup duration is adjusted based on the second error result. The first error result is smaller than the second error result, and the hiccup duration is adjusted according to the first error result; The first error result is equal to the second error result, and the hiccup duration is adjusted according to the first error result or the second error result.

10. The method according to claim 9, characterized in that, The first error result is greater than the second error result. Adjusting the hiccup duration based on the second error result specifically includes: When the first error result is greater than the second error result, if the output current is greater than the reference current, the hiccup duration is shortened; if the output current is less than the reference current, the hiccup duration is increased.

11. The method according to claim 9, characterized in that, The first error result is smaller than the second error result. Adjusting the hiccup duration based on the first error result specifically includes: When the first error result is less than the second error result, if the output voltage is greater than the reference voltage, the hiccup duration is shortened; if the output voltage is less than the reference voltage, the hiccup duration is increased.

12. The method according to claim 8, characterized in that, Also includes: The hiccup frequency is controlled based on the output voltage.

13. The method according to claim 12, characterized in that, The control of hiccup frequency based on the output voltage specifically includes: The switching frequency corresponding to the minimum loss is found based on the output voltage, and the hiccup frequency is controlled based on the switching frequency. The loss corresponding to the output voltage is different at different switching frequencies.

14. The method according to any one of claims 8-13, characterized in that, Also includes: When the hiccup duration exceeds the control cycle for N consecutive cycles, switch from hiccup mode to continuous mode. The N is greater than or equal to 2.

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