A controller for improving the accuracy of switching power supply

Abstract

The present invention provides a controller for improving the accuracy of a switching power supply, which improves the accuracy of the switching power supply by adjusting a reference voltage or adjusting a reference current, and includes an error amplifier, a reference voltage source generation module, a reference signal adjustment module, an externally programmable memory, and a duty cycle modulation module. The controller can be used not only in a primary feedback switching power supply to improve its output voltage accuracy, but also in a secondary feedback, non-isolated switching power supply, etc., to improve their output voltage to a higher accuracy than the corresponding traditional technology.

Description

Technical Field

[0001] The invention belongs to the technical field of primary-side feedback flyback switching power supplies, and in particular relates to a controller for improving the accuracy of a switching power supply. Background Art

[0002] Primary feedback technology is a control technology for flyback switching power supplies that has been popular in the past decade. Its basic principle is to use the proportional voltage between the windings of the flyback transformer during the demagnetization stage, so that the voltage value of another winding can be detected by detecting the voltage of one winding. Therefore, for an isolated flyback switching power supply, as long as the demagnetization voltage of the primary winding is detected, the size of the isolated secondary voltage can be sensed, and then the duty cycle of the power switch tube can be controlled through PMW modulation to achieve the purpose of stabilizing the output voltage.

[0003] Compared with the method of using optocouplers for isolated feedback, this feedback method omits the amplifier composed of optocouplers, TL431, etc. The direct advantage is that the number of devices is reduced, the space occupied is reduced, and the cost is reduced. At the same time, because the conventional optocoupler devices with poor high-temperature characteristics are eliminated, the operating temperature range of the switching power supply can be improved. Therefore, switching power supplies using this feedback technology are widely used, especially in adapters and some smart homes where the output voltage accuracy requirements are not high.

[0004] However, the primary-side feedback technology cannot replace the secondary-side feedback technology of optocoupler feedback and be more widely used. This is because the primary-side feedback technology is affected by the parasitic parameters and deviations of the feedback path, resulting in low output voltage accuracy of the switching power supply, which is difficult to match the switching power supply with secondary-side feedback in terms of accuracy.

[0005] like Figure 1 The figure shows a simplified schematic diagram of secondary feedback. Its working principle is: the output voltage VOUT is directly sampled by voltage divider resistors R1 and R2 on the isolated secondary side of the transformer. The sampled voltage is transmitted to the primary side by the differential current generated by the transconductance amplifier composed of TL431 and the optocoupler isolation. The differential current and the voltage generated by the pull-up resistor control the duty cycle of the switching power supply, so that the output voltage is stabilized at the set value. Since this sampling is direct sampling by resistors, as long as high-precision resistors are used, the output voltage will not deviate from the rated value due to sampling.

[0006] like Figure 2 As shown in the figure, it is a simplified schematic diagram of the primary feedback. Its working principle is: when the power switch tube NM0 is turned on, the flyback transformer is excited, and the secondary winding N SThe voltage VOS and the auxiliary winding voltage VA are negative voltages, and the output diode DOUT and the auxiliary power diode DVDD are both cut off; after NMO is turned off, the transformer enters the demagnetization stage. At this time, the transformer is demagnetized through the secondary winding NS and the auxiliary winding NA, and the output diode D OUT and auxiliary power diode D VDD The voltage of the secondary winding is:

[0007] VOS=Vour+VBE+Is*Td;

[0008] Where V OUT is the output voltage of the flyback switching power supply, V BE is the output diode D OUT The junction voltage drop, I S is the freewheeling current through the diode, r d It is the internal resistance of the diode. In practice, it also includes the wiring resistance. Since it is not a major part, it can be ignored in most cases.

[0009] The demagnetization voltage VA of the auxiliary winding is in a turns ratio relationship with VOS, and then passes through the sampling resistor R FB1 and R FB2 To sample the controller RFB port, the voltage at the port RFB is:

[0010]

[0011] Where N A and N S are the number of coils of the auxiliary winding and secondary winding of the transformer respectively.

[0012] The switching power supply controller samples the demagnetization voltage of VFB and finally stabilizes the voltage of VFB very close to the reference voltage Vref by modulating the duty cycle. Combining the above two formulas, the output voltage can be obtained as follows:

[0013]

[0014] It can be seen that the accuracy of the output voltage is affected by R FB1 and R FB2 The proportionality coefficient, N S and N AThe proportional coefficient, the junction voltage drop of the output diode VBE, and the influence of the diode internal resistance on the size of the freewheeling current can be collectively referred to as the factors that cause the output voltage accuracy to deteriorate due to the sampling path. The influence of the sampling resistor can be reduced by selecting a high-precision resistor, but it cannot be completely eliminated. The influence of the transformer on the output voltage accuracy is the most difficult to control in power supply manufacturing. The diode junction voltage drop not only has errors, but also has a large temperature coefficient, so the accuracy of the primary feedback switching power supply of traditional technology is not high. For power supplies working in intermittent mode, the voltage at the end of fast demagnetization can be detected, which is often called inflection point sampling. Since the freewheeling current Id is close to zero at this time, the voltage drop on the diode internal resistance rd is very small and can be ignored, so the accuracy can generally be achieved to ±5%; for power supplies entering CCM mode, that is, continuous mode, since the voltage drop caused by the freewheeling current on the internal resistance cannot be ignored, it is also difficult to meet ±5%. Summary of the invention

[0015] In view of the fact that the existing switching power supply with primary side feedback technology is difficult to achieve the output voltage accuracy of secondary side feedback, although it has a minimalist peripheral circuit without optocoupler and excellent high temperature characteristics, it cannot replace secondary side feedback and be applied in a wide range of fields. The present invention proposes a controller for improving the accuracy of the switching power supply.

[0016] In order to have a basic understanding of some aspects of the disclosed embodiments, a brief summary is given below. This summary is not intended to be a general review, nor is it intended to identify key / important components or to delineate the scope of protection of these embodiments. Its only purpose is to present some concepts in a simple form as a preface to the detailed description that follows.

[0017] The present invention adopts the following technical solution:

[0018] In some optional embodiments, a controller for improving the accuracy of a switching power supply is provided, comprising: a reference signal trimming module and an externally programmable memory, wherein the Up control signal input port of the reference signal trimming module is connected to the Up output port of the externally programmable memory, and the Down control signal input port of the reference signal trimming module is connected to the Down output port of the externally programmable memory; the reference signal trimming module provides a reference voltage for stabilizing the output voltage of the switching power supply, and the externally programmable memory reprograms the code of the memory according to the trimming signal to change the reference voltage output by the reference signal trimming module.

[0019] In some optional embodiments, the controller for improving the accuracy of a switching power supply further includes: an error amplifier and a reference voltage source generating module; the reference voltage source generating module outputs a reference voltage to the reference signal adjustment module or the error amplifier; the error amplifier is used to amplify the error between a sampling signal of the output voltage and a reference voltage provided by the reference signal adjustment module, or to amplify the error between a sampling signal of the output voltage adjusted by the reference signal adjustment module and a reference voltage output by the reference voltage source generating module.

[0020] In some optional embodiments, the controller for improving the accuracy of a switching power supply further includes: a duty cycle modulation module, wherein the first input port of the duty cycle modulation module is connected to the output port of the error amplifier, and the duty cycle modulation module is used to modulate the duty cycle according to the output voltage of the error amplifier, and output a driving signal with different duty cycles for driving the power tube switch, so that the output voltage of the switching power supply is stabilized at a set value.

[0021] In some optional embodiments, the external programmable memory includes: a selector and a memory, the selector outputs a selection signal to the memory; the selector includes: a selection switch tube NMS, a pull-up bias resistor Rdn, a NOT gate not3, a selection switch tube PMS, a pull-down bias resistor Rdp, a NOT gate not4 and a NOT gate not5;

[0022] The source of the selection switch tube NMS is connected to the source of the selection switch tube PMS, and is connected to the pin TRIM of the external programmable memory;

[0023] A 2.5V bias voltage is applied to the gate of the select switch NMS, and a 5V bias voltage is applied to the gate of the select switch PMS;

[0024] The drain of the selection switch tube NMS is connected to the second port of the pull-up bias resistor Rdn and the input port of the NOT gate not3 respectively, and the output signal of the NOT gate not3 is used as the selection signal of one of the selectors;

[0025] A first port of the pull-up bias resistor Rdn is connected to a positive power input port;

[0026] The drain of the selection switch tube PMS is connected to the first port of the pull-down bias resistor Rdp and the input port of the NOT gate not4 respectively;

[0027] The second port of the pull-down bias resistor Rdp is connected to the negative port of the power input;

[0028] The output port of NOT gate not4 is connected to the input port of NOT gate not5, and the output signal of NOT gate not5 is used as another selection signal of the selector.

[0029] In some optional embodiments, the memory includes: a pull-down resistor Rin, a fuse control switch tube Nfuse, a fuse FUSE, a bias current source and a NOT gate not1; the first port of the pull-down resistor Rin is connected to the gate of the fuse control switch tube Nfuse and forms the input end of the memory, and the second port of the pull-down resistor Rin is connected to the negative power input port; the drain of the fuse control switch tube Nfuse is respectively connected to the second port of the fuse FUSE, the input port of the bias current source, and the input port of the NOT gate not1; the first port of the fuse FUSE is connected to the positive power input port; the output port of the bias current source and the source of the fuse control switch tube Nfuse are respectively connected to the negative power input port.

[0030] In some optional embodiments, the memory further includes: a NOT gate not2; an input port of the NOT gate not2 is connected to an output port of the NOT gate not1, and an output port of the NOT gate not2 is connected to an output end of the memory.

[0031] The beneficial effects brought by the present invention are as follows: it can be applied not only to primary-side feedback switching power supplies to improve their output voltage accuracy, but also to secondary-side feedback, non-isolated switching power supplies, etc., to improve their output voltage to a higher accuracy than the corresponding traditional technologies. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 A simplified schematic diagram of a secondary-side feedback flyback switching power supply in the prior art;

[0033] Figure 2 It is a simplified schematic diagram of a primary-side feedback flyback switching power supply in the prior art;

[0034] Figure 3 An externally programmable memory designed based on fuses according to the present invention;

[0035] Figure 4 A selector implemented by one pin is adopted for the present invention;

[0036] Figure 5 The schematic diagram of the present invention is to correct the output voltage by adjusting the reference voltage;

[0037] Figure 6 A specific implementation circuit diagram of the present invention for correcting the output voltage by adjusting the reference voltage;

[0038] Figure 7 The schematic diagram of the present invention is to correct the output voltage by adjusting the reference current;

[0039] Figure 8This is a specific implementation circuit diagram of the present invention for correcting the output voltage by adjusting the reference current. DETAILED DESCRIPTION

[0040] The following description and accompanying drawings fully demonstrate specific embodiments of the present invention so that those skilled in the art can practice them. Other embodiments may include structural, logical, electrical, process and other changes. The embodiments represent possible variations only. Unless clearly required, separate components and functions are optional, and the order of operation may vary. The parts and features of some embodiments may be included in or replace the parts and features of other embodiments.

[0041] The controller provided by the present invention adopts an external power MOS tube and a series resistor to perform current sampling, thereby defining a drive pin DRV and a current sampling pin RCS. Pin definitions like this are only for placing the method and controller of the present invention into a specific switching power supply for detailed description, which is easier to understand, rather than for limiting the scope of application of the present invention, because the application of the built-in power MOS tube and current sampling does not hinder the implementation of the core content of the present invention.

[0042] like Figures 3 to 6 As shown, in some illustrative embodiments, a controller for improving the accuracy of a switching power supply is provided, which improves the accuracy of the switching power supply by adjusting a reference voltage or adjusting a reference current, and includes: an error amplifier, a reference voltage source generation module, a reference signal adjustment module, an externally programmable memory, and a duty cycle modulation module.

[0043] The error amplifier comprises: a negative input port 101, a positive input port 102 and an output port 103;

[0044] The duty cycle modulation module comprises: a first input port 104, a second input port 105, and a duty cycle output port 106;

[0045] The reference signal adjustment module includes: an Up control signal input port 108, a Down control signal input port 109, a reference voltage source input port 110, and a reference voltage output port 107;

[0046] The external programmable memory includes: an input port 113, an Up control signal output port 112, and a Down control signal output port 114;

[0047] The reference voltage source generating module comprises a reference voltage source output port 111 .

[0048] The connection relationship and signal functions of the various components of the controller of the present invention are as follows: the negative input port 101 is connected to the controller port RFB, sampling the feedback output voltage, that is, the sampling signal of the output voltage; the positive input port 102 is connected to the reference voltage output port 107, and the reference signal adjustment module provides a reference voltage Vref_out for stabilizing the output voltage VOUT of the switching power supply; the output port 103 is connected to the first input port 104, and the duty cycle modulation module modulates the duty cycle according to the output voltage of the error amplifier to stabilize the output voltage of the switching power supply at a set value; the second input port 105 is connected to the current feedback pin RCS of the controller to realize current sampling; the duty cycle output port 106 is connected to the driving port DRV of the controller to drive the external power MOS tube NM O; the reference voltage source input port 110 is connected to the reference voltage source output port 111, and the reference voltage source generating module provides the reference power source Vref_in for the reference signal trimming module; the Up control signal input port 108 is connected to the Up control signal output port 112, and the externally programmable storage module provides the control signal Up to increase the output voltage of the reference signal trimming module, that is, the voltage of the positive input port 102 is increased, so that the output voltage of the switching power supply can be increased; the Down control signal input port 109 is connected to the Down control signal output port 114, and the externally programmable storage module provides the control signal Down to reduce the output voltage of the reference signal trimming module, that is, the voltage of the positive input port 102 is reduced, so that the output voltage of the switching power supply can be reduced.

[0049] The reference signal trimming module provides a reference voltage for stabilizing the output voltage of the switching power supply; the external programmable memory reprograms the code of the memory according to the trimming signal to change the reference voltage output by the reference signal trimming module. The reference voltage source generation module outputs the reference voltage to the reference signal trimming module or the error amplifier; when the switching power supply accuracy is improved by trimming the reference voltage, the error amplifier amplifies the error between the sampling signal of the output voltage and the reference voltage provided by the reference signal trimming module; when the switching power supply accuracy is improved by trimming the reference current, the error amplifier amplifies the error between the sampling signal of the output voltage adjusted by the reference signal trimming module and the reference voltage output by the reference voltage source generation module; the duty cycle modulation module is used to modulate the duty cycle according to the output voltage of the error amplifier, and output drive signals with different duty cycles for driving the power tube switch, so that the output of the switching power supply is stabilized at the set value.

[0050] The controller of the present invention improves the accuracy of the switching power supply by adjusting the reference voltage. The working principle is: the error amplifier amplifies the error between the sampling signal of the output voltage and the reference voltage provided by the reference signal adjustment module, and the amplified voltage modulates the output of the driving signal with different duty ratios to drive the switch of the power tube, and finally stabilizes the output of the switching power supply at the set value. This is the basic principle of the switching power supply to stabilize the output voltage. The present invention provides a memory, which is connected to the adjustment pin TRIM of the controller chip, and changes the code of the memory according to the adjustment signal of the adjustment pin TRIM, thereby changing the output reference voltage of the reference signal adjustment module, that is, changing the reference voltage for stabilizing the output voltage of the switching power supply, so that the output voltage of the switching power supply can be fine-tuned by fine-tuning the reference voltage. When the device parameter deviation of the switching power supply causes its output voltage to be lower than the required minimum value, the reference voltage of the error amplifier is increased by adding an excitation to the adjustment pin TRIM, thereby increasing the output voltage of the switching power supply until the output voltage meets the requirements; similarly, when the output voltage of the switching power supply is higher than the required maximum value, the reference voltage of the error amplifier is reduced by adding an excitation to the adjustment pin TRIM, thereby reducing the output voltage of the switching power supply until the output voltage meets the requirements.

[0051] like Figure 7 and 8 As shown, the present invention can also improve the accuracy of the switching power supply controller by adjusting the reference current. At this time, the error amplifier amplifies the error between the sampling signal of the output voltage adjusted by the reference signal adjustment module and the reference voltage output by the reference voltage source generation module. The connection mode and function of the error amplifier, the reference voltage source generation module, the reference signal adjustment module, the external programmable memory and the duty cycle modulation module are as follows:

[0052] The error amplifier has a negative input port 101 connected to the current output port 201 of the reference signal trimming module and the voltage feedback signal of the switching power supply, that is, connected to the pin RFB, a positive input port 102 connected to the reference voltage source output port 111 of the reference voltage source generating module, and an output port 103 connected to the first input port 104 of the duty cycle modulation module. The first input port 104 of the duty cycle modulation module is connected to the output port 103 of the error amplifier, the second input port 105 is connected to the pin RCS, and the duty cycle output port 106 is connected to the pin DRV. The Up control signal input port 108 and the Down control signal input port 109 of the reference signal trimming module are respectively connected to the Up control signal output port 112 and the Down control signal output port 114 of the external programmable memory, and the reference voltage output port 107 is connected to the negative input port 101 of the error amplifier. The input port 113 of the external programmable memory is connected to the trimming pin TRIM of the controller. The reference voltage source generating module has a reference voltage source output port 111 connected to the positive input port 103 of the error amplifier.

[0053] The controller of the present invention improves the accuracy of the switching power supply by adjusting the reference current. The working principle is: the reference current generated by the reference signal adjustment module superimposes an additional voltage drop on the sampling resistor, and changing the size of the reference current can change the additional voltage drop superimposed on the sampling resistor, thereby changing the feedback voltage of the output voltage of the switching power supply, so that the output voltage of the power supply changes accordingly. The size of the reference current is changed by changing the code of the memory through the trimming pin TRIM, and then the output voltage of the switching power supply is corrected to meet the requirements.

[0054] In the semiconductor process of designing power chips, two methods are often used to achieve the function of permanent storage. One is electrically erasable memory (EEPROM), and the other is a memory that forms one bit with a fuse. A fuse is a small resistor with a certain resistance value, generally tens of ohms to hundreds of ohms. Due to its small size, after a current of tens of milliamperes to hundreds of milliamperes passes through it for a period of time, it is melted due to concentrated heat, just like a very low-power fuse. The principle is simple and easy to understand, so the following describes the use of fuses to achieve a memory with permanent storage capacity.

[0055] The external programmable memory includes: a selector and a memory. The memory includes: a pull-down resistor Rin, a fuse control switch tube Nfuse, a fuse FUSE, a bias current source and a NOT gate not1; the first port of the pull-down resistor Rin is connected to the gate of the fuse control switch tube Nfuse and forms the input end of the memory, and the second port of the pull-down resistor Rin is connected to the negative power input port; the drain of the fuse control switch tube Nfuse is connected to the second port of the fuse FUSE, the input port of the bias current source, and the input port of the NOT gate not1; the first port of the fuse FUSE is connected to the positive power input port VDD; the output port of the bias current source and the source of the fuse control switch tube Nfuse are respectively connected to the negative power input port. Thus, a memory storing an initial state of "1" is formed.

[0056] The memory further includes: a NOT gate not2; the input port of the NOT gate not2 is connected to the output port of the NOT gate not1, and the output port of the NOT gate not2 is connected to the output port Vout of the memory, thereby forming a memory storing an initial state of "0".

[0057] like Figure 3 As shown, the working principle of the memory is: when the input port Vin of the memory is suspended or connected to the Nfuse power supply "ground", the fuse control switch Nfuse is turned off. Since the current provided by the fuse FUSE is much larger than the bias current source, for example, 2uA, the drain voltage of the fuse control switch Nfuse is equal to the power supply voltage, and the output of the NOT gate not2 is also the power supply voltage, that is, the output logic state "1". As long as Vin does not add a positive voltage, the memory will maintain this state after powering on. When a positive voltage is continuously added to the input terminal Vin of the memory to turn on the fuse control switch Nfuse until the fuse FUSE is blown, the drain voltage of the fuse control switch Nfuse becomes a low voltage due to the effect of the bias current source, and the NOT gate not2 outputs a logic state "0". Once the fuse FUSE is blown, the memory will always be in this state when it is powered on. This method of writing data by fusing is irreversible. If you want to obtain a memory with an initial state of "0", just remove a NOT gate. In this way, you will have two states: initialized to "0" and initialized to "1". You can save the initialized data code according to design needs.

[0058] The output voltage of the switching power supply exceeds the specification range. It may be higher than the maximum value allowed, in which case the output voltage needs to be reduced, or it may be lower than the minimum value allowed, in which case the output voltage needs to be increased. If two pins are used to adjust the output voltage of the switching power supply, one to increase the output voltage and the other to reduce the output voltage, there is naturally no operational conflict, but this may lead to insufficient chip package pins. Therefore, the following describes a data selector that uses only one pin to implement the two operations of increasing and reducing the output voltage.

[0059] like Figure 4 As shown, a pin TRIM is used to implement a data selector for changing the output voltage in two different directions, and the selector outputs a selection signal to the memory; the selector includes: a selection switch tube NMS, a pull-up bias resistor Rdn, a NOT gate not3, a selection switch tube PMS, a pull-down bias resistor Rdp, a NOT gate not4 and a NOT gate not5.

[0060] The source of the selection switch tube NMS is connected to the source of the selection switch tube PMS, and is connected to the TRIM pin of the external programmable memory; 2.5V and 5V bias voltages are applied to the gates of the selection switch tube NMS and the selection switch tube PMS respectively; the drain of the selection switch tube NMS is connected to the second port of the pull-up bias resistor Rdn and the input port of the NOT gate not3, and the output signal of the NOT gate not3 is used as one of the selection signals of the selector, that is, the A signal; the first port of the pull-up bias resistor Rdn is connected to the positive port of the power input; the drain of the selection switch tube PMS is connected to the first port of the pull-down bias resistor Rdp and the input port of the NOT gate not4; the second port of the pull-down bias resistor Rdp is connected to the negative port of the power input; the output port of the NOT gate not4 is connected to the input port of the NOT gate not5, and the output signal of the NOT gate not5 is used as another selection signal of the selector, that is, the B signal.

[0061] The working principle of the selector is: when the pin TRIM is suspended, the selection switch tube NMS and the selection switch tube PMS are both turned off, then the NOT gate not3 and the NOT gate not5 both output a low potential, that is, both output logic "0". If the pin TRIM is connected to the power supply "ground", the selection switch tube NMS is turned on, its drain voltage is pulled to a low potential, and the NOT gate not3 outputs a high level, that is, outputs a logic "1", then the A path is selected, because the selection switch tube PMS is turned off, the B path still outputs "0", not selected; if the pin TRIM is added with a voltage exceeding 5V to make the selection switch tube PMS fully turned on, so that its drain voltage reaches the voltage of the logic level "1", the NOT gate not5 outputs a high voltage, that is, outputs a logic "1", then the B path is selected, because the source voltage of the selection switch tube NMS is higher than the gate voltage, it is cut off, and the NOT gate not3 outputs a low potential, and is not selected. It can be seen that when the pin TRIM is connected to the "ground" low voltage, only path A is selected, and when it is connected to a high voltage, only path B is selected. If the control signal of path A is designed to increase the output voltage, path B is to reduce the output voltage. One pin can realize voltage correction in two different directions of increasing and decreasing the output voltage.

[0062] like Figure 6 As shown in FIG. 1 , it is a specific implementation circuit diagram of the controller of this embodiment. The outputs of the selector A and B are two control signals. A controls a memory whose initial state is "0", and B controls a memory whose initial state is "1". Therefore, without any voltage adjustment action, the voltage of the Down control signal output port 114 and the Down control signal input port 109 is a low voltage, and the adjustment switch tube NMC is turned off, while the Up control signal output port 112 and the Up control signal input port 108 are high level, and the adjustment switch tube NMD is turned on. It is easy to calculate that the reference voltage of the error amplifier positive input port 102 is:

[0063]

[0064] When the output voltage VOUT of the switching power supply exceeds the maximum value of the allowable range, the voltage of the pin TRIM is continuously pulled down to the power ground, the A path of the selector becomes a high voltage, and the fuse is energized until it is blown. After the fuse of the memory controlled by the A path is blown, the output voltage of the memory is always a high voltage when it is powered on, and the trimming switch tube NMC is turned on. It is easy to calculate the trimmed voltage:

[0065]

[0066] It can be seen that the denominator in the brackets decreases, the reference voltage of the error amplifier decreases, and the output voltage VOUT of the switching power supply decreases, which plays a role in correcting the output voltage.

[0067] On the contrary, when the output voltage VOUT of the switching power supply is less than the minimum value of the allowable range, the voltage at the pin TRIM is continuously increased to make the selector B output a high level voltage until the fuse is blown, so that the Up signal of the Up control signal output port 112 and the Up control signal input port 108 becomes a low voltage, and the trimming switch NMD is turned off. It is easy to calculate the trimmed voltage as:

[0068]

[0069] It can be seen that the reference voltage of the error amplifier increases, and the output voltage VOUT of the switching power supply increases, which plays a role in correcting the output voltage.

[0070] like Figure 7 and Figure 8 As shown, the output voltage of the switching power supply is corrected by adjusting the reference current. Therefore, compared with the method of correcting the output voltage of the switching power supply by adjusting the reference voltage, the difference lies in that the memory controls the reference signal adjustment module, and the reference current output by the current output port 201 of the reference signal adjustment module flows into or out of the controller from the port RFB.

[0071] The method of the controller of the present invention to provide the output voltage accuracy of the switching power supply is:

[0072] The first step is to design a programmable permanent memory inside the controller, that is, an external programmable memory, and the reference voltage or reference current that affects the output voltage of the switching power supply can be changed by reprogramming the code of the external programmable memory;

[0073] The externally programmable memory means that the code stored in the memory can be continuously stored even after power failure after being rewritten;

[0074] The second step is to set a specific programming pin on the controller for programming the external programmable memory. This specific pin can be independent or multiplexed with other functional pins of the controller;

[0075] The third step is to test the output voltage of the switching power supply. If the output voltage exceeds the accuracy range, the output voltage is corrected through the programming pin to meet the accuracy range.

[0076] Those skilled in the art will also appreciate that the various illustrative logic blocks, modules, circuits, and algorithmic steps described in conjunction with the embodiments herein can all be implemented as electronic hardware, computer software, or a combination thereof. In order to clearly illustrate the interchangeability between hardware and software, various illustrative components, blocks, modules, circuits, and steps are generally described above around their functions. Whether such functions are implemented as hardware or software depends on specific applications and the design constraints imposed on the entire system. A skilled person can implement the described functions in an alternative manner for each specific application, but such implementation decisions should not be interpreted as departing from the scope of protection of the present disclosure.

Claims

1. A controller for improving the accuracy of a switching power supply, characterized in that: include: A reference signal trimming module and an externally programmable memory, wherein the Up control signal input port of the reference signal trimming module is connected to the Up output port of the externally programmable memory, and the Down control signal input port of the reference signal trimming module is connected to the Down output port of the externally programmable memory; the reference signal trimming module provides a reference voltage for stabilizing the output voltage of the switching power supply, and the externally programmable memory reprograms the code of the memory according to the trimming signal to change the reference voltage output by the reference signal trimming module; The external programmable memory comprises: a selector and a memory, wherein the selector outputs a selection signal to the memory; the selector comprises: a selection switch tube NMS, a pull-up bias resistor Rdn, a NOT gate not3, a selection switch tube PMS, a pull-down bias resistor Rdp, a NOT gate not4 and a NOT gate not5; The source of the selection switch tube NMS is connected to the source of the selection switch tube PMS, and is connected to the pin TRIM of the external programmable memory; A 2.5V bias voltage is applied to the gate of the select switch NMS, and a 5V bias voltage is applied to the gate of the select switch PMS; The drain of the selection switch tube NMS is connected to the second port of the pull-up bias resistor Rdn and the input port of the NOT gate not3 respectively, and the output signal of the NOT gate not3 is used as the selection signal of one of the selectors; A first port of the pull-up bias resistor Rdn is connected to a positive power input port; The drain of the selection switch tube PMS is connected to the first port of the pull-down bias resistor Rdp and the input port of the NOT gate not4 respectively; The second port of the pull-down bias resistor Rdp is connected to the negative port of the power input; The output port of NOT gate not4 is connected to the input port of NOT gate not5, and the output signal of NOT gate not5 is used as another selection signal of the selector.

2. A controller for improving the accuracy of a switching power supply according to claim 1, characterized in that: Also includes: Error amplifier and reference voltage source generation module; The reference voltage source generating module outputs the reference voltage to the reference signal adjusting module or the error amplifier; The error amplifier is used to amplify the error between the sampling signal of the output voltage and the reference voltage provided by the reference signal adjustment module, or to amplify the error between the sampling signal of the output voltage adjusted by the reference signal adjustment module and the reference voltage output by the reference voltage source generation module.

3. A controller for improving the accuracy of a switching power supply according to claim 2, characterized in that: Also includes: A duty cycle modulation module, wherein the first input port of the duty cycle modulation module is connected to the output port of the error amplifier, and the duty cycle modulation module is used to modulate the duty cycle according to the output voltage of the error amplifier, and output a driving signal with different duty cycles for driving the power tube switch, so that the output voltage of the switching power supply is stabilized at a set value.

4. A controller for improving the accuracy of a switching power supply according to claim 1, characterized in that: The memory includes: a pull-down resistor Rin, a fuse control switch tube Nfuse, a fuse FUSE, a bias current source and a NOT gate not1; the first port of the pull-down resistor Rin is connected to the gate of the fuse control switch tube Nfuse and forms the input end of the memory, and the second port of the pull-down resistor Rin is connected to the negative power input port; the drain of the fuse control switch tube Nfuse is respectively connected to the second port of the fuse FUSE, the input port of the bias current source, and the input port of the NOT gate not1; the first port of the fuse FUSE is connected to the positive power input port; the output port of the bias current source and the source of the fuse control switch tube Nfuse are respectively connected to the negative power input port.

5. A controller for improving the accuracy of a switching power supply according to claim 4, characterized in that: The memory further includes: a NOT gate not2; an input port of the NOT gate not2 is connected to an output port of the NOT gate not1, and an output port of the NOT gate not2 is connected to an output end of the memory.

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