Switching DC converter control method with high response speed characteristic

Abstract

The invention belongs to the technical field of converters, and particularly relates to a control method of a switching direct-current converter with a high response speed characteristic. According to the method, a current signal is obtained mainly by obtaining the voltage difference of a secondary filter, then a load feedback voltage is compared with a reference signal, and after an error signal is obtained, the error signal is compared with the current signal to generate a pulse signal used for controlling the switching direct-current converter. The method has the beneficial effects that high load switching response speed and high loop stability are obtained for the direct-current converter with two-stage or more filters.

Description

Technical Field

[0001] The invention belongs to the technical field of converters, and in particular relates to a control method for a switching DC converter with high response speed characteristics. Background Art

[0002] DC voltage converters are widely used in industrial applications, mobile devices, automotive electronics, data centers and other scenarios. Common DC voltage converters, such as Buck converters, Boost converters, Forward converters, etc., generally have a first-stage filter in their topology. In practical applications, due to the ripple requirements, a second-stage filter may be used after the first-stage filter to achieve lower output ripple. Parasitic parameters on the circuit board power distribution network may also actually constitute a second-stage filter. The second-stage filter brings more phase lag than the first-stage filter, so the feedback loop bandwidth is usually conservatively designed to ensure the stability of the system. In order to have a more accurate output voltage static accuracy, the document "Jindong Zhang, Method of and system for regulating output voltage, US patent 7212012B1, 2007." proposes a method in which low-frequency feedback is set at the output end of the second-stage filter in the feedback loop, and high-frequency signals are detected at the output end of the first-stage filter, thereby ensuring the accuracy of the output voltage and the stability of the loop. However, these methods have the problem of slow voltage transient response at the output end of the second-stage filter. Summary of the invention

[0003] In view of the problems existing in the prior art, the present invention provides a switching DC converter control method with high response speed characteristics.

[0004] The technical solution of the present invention is:

[0005] A control method for a switching DC converter with high response speed characteristics, wherein the switching DC converter includes a power switch device and a first-stage filter, and the output of the switching DC converter is output to a load after passing through a second-stage filter; the control method includes:

[0006] S1, detect the difference of the electrical signals at both ends of the second-stage filter, which is defined as the detection signal FW;

[0007] S2, obtaining a feedback voltage signal FB of the load, comparing FB with a reference voltage VREF through an error amplifier, and defining the output of the error amplifier as a feedback control signal;

[0008] S3, adding the detection signal FW and the feedback control signal to obtain a pulse modulation signal, which is defined as a first modulation signal MOD, and inputting the first modulation signal MOD into a pulse modulator;

[0009] S4, detecting the electrical signal in the switch DC converter, defining it as a second modulation signal CS, and inputting the second modulation signal CS into the pulse modulator;

[0010] S5. In the pulse modulator, a control pulse signal is generated under the joint action of the first modulation signal MOD and the second modulation signal CS, and the control pulse signal is used to control the power switch device in the switching DC converter.

[0011] Furthermore, the specific method of detecting the electrical signal in the switching DC converter is:

[0012] Detect the current signal of the power switch device or detect the current signal of the relevant device in the first stage filter.

[0013] Furthermore, the second modulation signal CS is obtained by detecting the current signal of the power switching device, and the pulse modulator includes a comparator, a pulse signal generator, and a periodic slope compensation signal Ramp. Ramp is added to the second modulation signal CS and input to the positive input terminal of the comparator, the first modulation signal MOD is input to the negative input terminal of the comparator, and the output terminal of the comparator is input to the pulse signal generator to generate a control pulse signal.

[0014] Furthermore, the second modulation signal CS is obtained by detecting the inductor current signal in the first-stage filter, and the pulse modulator includes a comparator, a pulse signal generator, and a periodic slope compensation signal Ramp. Ramp is added to the second modulation signal CS and input to the negative input terminal of the comparator, the first modulation signal MOD is input to the positive input terminal of the comparator, and the output terminal of the comparator is input to the pulse signal generator to generate a control pulse signal.

[0015] Furthermore, the second modulation signal CS is obtained by detecting the output current signal in the first-stage filter, and the pulse modulator includes a three-input comparator, a pulse signal generator, and a periodic slope compensation signal Ramp. Ramp is added to the second modulation signal CS and input to the negative input terminal of the comparator, the first modulation signal MOD is input to the first positive input terminal of the comparator, the second positive input terminal of the comparator is connected to the reference voltage signal, and the output terminal of the comparator is input to the pulse signal generator to generate a control pulse signal.

[0016] Furthermore, there are multiple power switch devices inside the switching DC converter, and the corresponding pulse modulator generates multiple pulse signals, each of which corresponds to a power switch device.

[0017] The detection signal and the feedback signal in the above scheme are signals of the same nature. If the detected signals are different, they are converted into signals of the same nature through a conversion circuit, and finally the first modulated signal is obtained from the two signals.

[0018] The beneficial effect of the present invention is that, for a DC converter with two or more filters, a high load switching response speed and a high loop stability are obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the traditional circuit structure.

[0020] Figure 2 It is a schematic diagram of the circuit structure of the present invention.

[0021] Figure 3 2 is a schematic diagram of the circuit structure of Example 1.

[0022] Figure 4 2 is a schematic diagram of the circuit structure of Example 2.

[0023] Figure 5 2 is a schematic diagram of the circuit structure of Example 3. DETAILED DESCRIPTION

[0024] The present invention is described in detail below with reference to the accompanying drawings.

[0025] The conventional switching power converter circuit structure with a secondary filter is as follows: Figure 1 As shown. The basic switching converter circuit includes power switching devices and inductors, capacitors and / or transformer components. The controller detects the voltage of the output terminal Vout_remote through the FB signal terminal and generates one or more pulse signals through calculation. These pulse signals control the switching of the power device and adjust the Vout_remote voltage output by the second-stage filter to reach the target voltage set by the controller.

[0026] The control system used in the present invention is as follows Figure 2 As shown. The switching converter includes power switching devices and inductor, capacitor and / or transformer components. The voltage difference across the second-stage filter is detected and sent to a circuit module inverse calculation module. This module can be constructed by analog circuits or digital circuits. According to the structure and parameter characteristics of the second-stage filter, the inverse calculation module calculates its output signal FW, which can be used to represent the current delivered to the load through the second-stage filter.

[0027] On the other hand, the voltage at the load end is fed back to the error amplifier EA. The error between the FB signal and the VREF reference voltage signal is amplified by the EA, and after being added to the FW signal, it becomes the MOD signal, which is sent to the pulse modulator Modulator of the control pulse. Pulse modulation can adopt constant frequency falling edge modulation, constant frequency rising edge modulation, double edge modulation, constant on-time modulation or constant off-time modulation and hysteresis modulation. The input signal of the pulse width / frequency modulator also comes from the current detection signal CS of the switching converter. It can be the current detection signal of the inductor or transformer in the power switching circuit, or it can be the current detection signal of the switching device or other branches. Optionally, the pulse width modulator can include a periodic slope compensation signal Ramp to achieve better loop stability and anti-noise capability. One or more pulse signals D output by the pulse width modulator control the switch of one or more power devices of the switching converter to achieve accurate and fast adjustment of the load end Vout_remote voltage.

[0028] Example 1

[0029] like Figure 3 As shown, the power switch circuit topology in this example is a single-phase boost converter. There is a second-stage filter between its output voltage Vout and the load, which includes an inductor, two resistors and a capacitor. The current of the power switch tube is detected as a CS signal. The signal between the input and output of the second-stage filter is amplified by the amplifier, in which the reactance Z1-Z4 can be properly designed to produce appropriate zero poles and gains for adjusting the output FW signal. The voltage at the load end is sent to the FB end of the controller through the feedback circuit. The error between this signal and the reference voltage VREF is amplified and compensated by the OTA, and then added to the FW signal to become the input MOD of the pulse width modulator. The pulse width modulator adds the CS signal and the optional sawtooth wave signal to compare with MOD, triggering the RS trigger to generate a pulse signal D to control the switch of the power tube.

[0030] Example 2

[0031] like Figure 4As shown, the power switch circuit topology in this example is a two-phase parallel buck converter. The two phases jointly supply power to the load. There is a second-stage filter between its output voltage Vout and the load, which includes an inductor, a resistor and two capacitors. Due to the similarity of the structure, the circuit relationship is described using the circuit of the first phase. The current of the power inductor L1 is detected as the CS1 signal. The signal between the input and output of the second-stage filter is connected to the reactance network composed of Z7-10 (just as an example). The two nodes in the network are used to indirectly detect the current of the second-stage filter. They are connected to the amplifier, and the reactance Z1-Z4 around the amplifier can be appropriately designed to produce appropriate zero poles and gain for adjusting the output FW signal. The voltage at the load end is sent to the FB terminal of the controller through the feedback circuit. The error between this signal and the reference voltage VREF is amplified by EA, added to the FW signal, and becomes the input MOD of the pulse width modulator. The pulse width modulator uses the CS1 signal and the optional sawtooth wave signal to add and compare with MOD, triggering the monostable generator to generate a pulse signal D1 to control the switch of the power tube M1. Similarly, the current detection signal CS2 of the power inductor L2 is compared with MOD to generate a pulse signal D2 to control the power tube M2.

[0032] As an extension of the proposed circuit concept, the inverse calculation module can also sample signals of more than two nodes on the secondary filter for signal calculation.

[0033] Example 3

[0034] like Figure 5 As shown in the figure, in this example, the current detection of the two-phase parallel buck converter is located at the connection of the two inductors to obtain the CS_total detection signal. The signal of VOUT_remote passes through the feedback network, is added with MOD and sent to the comparator, and is compared with the current detection and reference voltage signals to trigger the monostable trigger. The pulses generated by the trigger drive the power tubes of the two phases respectively through the pulse distributor.

Claims

1. A control method for a switching DC converter with high response speed characteristics, wherein the switching DC converter includes a power switch device and a first-stage filter, and the output of the switching DC converter is output to a load after passing through a second-stage filter; characterized in that: The control method comprises: S1, detect the difference of the electrical signals at both ends of the second-stage filter, which is defined as the detection signal FW; S2, obtaining a feedback voltage signal FB of the load, comparing FB with a reference voltage VREF through an error amplifier, and defining the output of the error amplifier as a feedback control signal; S3, adding the detection signal FW and the feedback control signal to obtain a pulse modulation signal, which is defined as a first modulation signal MOD, and inputting the first modulation signal MOD into a pulse modulator; S4, detecting the electrical signal in the switch DC converter, defining it as a second modulation signal CS, and inputting the second modulation signal CS into the pulse modulator; S5. In the pulse modulator, a control pulse signal is generated under the joint action of the first modulation signal MOD and the second modulation signal CS, and the control pulse signal is used to control the power switch device in the switching DC converter.

2. A switching DC converter control method with high response speed characteristics according to claim 1, characterized in that: The specific method of detecting the electrical signal in the switching DC converter is: Detect the current signal of the power switch device or detect the current signal of the relevant device in the first stage filter.

3. A switching DC converter control method with high response speed characteristics according to claim 2, characterized in that: The second modulation signal CS is obtained by detecting the current signal of the power switching device, and the pulse modulator includes a comparator, a pulse signal generator, and a periodic slope compensation signal Ramp. Ramp is added to the second modulation signal CS and input to the positive input terminal of the comparator, the first modulation signal MOD is input to the negative input terminal of the comparator, and the output terminal of the comparator is input to the pulse signal generator to generate a control pulse signal.

4. A switching DC converter control method with high response speed characteristics according to claim 2, characterized in that: The second modulation signal CS is obtained by detecting the inductor current signal in the first-stage filter. The pulse modulator includes a comparator, a pulse signal generator, and a periodic slope compensation signal Ramp. Ramp is added to the second modulation signal CS and input to the negative input terminal of the comparator. The first modulation signal MOD is input to the positive input terminal of the comparator. The output terminal of the comparator is input to the pulse signal generator to generate a control pulse signal.

5. The control method of a switching DC converter with high response speed characteristics according to claim 2, characterized in that: The second modulation signal CS is obtained by detecting the output current signal in the first-stage filter, and the pulse modulator includes a three-input comparator, a pulse signal generator, and a periodic slope compensation signal Ramp. Ramp is added to the second modulation signal CS and input to the negative input terminal of the comparator, the first modulation signal MOD is input to the first positive input terminal of the comparator, the second positive input terminal of the comparator is connected to the reference voltage signal, and the output terminal of the comparator is input to the pulse signal generator to generate a control pulse signal.

6. A switching DC converter control method with high response speed characteristics according to claim 1, characterized in that: There are multiple power switch devices inside the switching DC converter, and the corresponding pulse signals generated in the pulse modulator are also multiple, and each pulse signal corresponds to a power switch device.

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