A switching DC converter control method with high response speed characteristic

Abstract

The present application belongs to the field of converter technology, and particularly relates to a switching DC converter control method with high response speed characteristics. The method of the present application mainly obtains a current signal by obtaining a voltage difference of a secondary filter, then compares a load feedback voltage with a reference signal to obtain an error signal, and compares the error signal with the current signal to generate a pulse signal for controlling the switching DC converter. The present application has the beneficial effect of obtaining high load switching response speed and high loop stability for a DC converter with a secondary or more filters.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of converters, and particularly relates to a control method of a switching DC converter with high response speed characteristics. BACKGROUND

[0002] DC voltage converters are widely used in industrial applications, mobile devices, automotive electronics, data centers and many other scenarios. Common DC voltage converters, such as Buck converters, Boost converters, Forward converters, etc., generally have a first-order filter in their topology. In actual applications, due to the requirement of ripple, a second-order filter may be used after the first-order filter to achieve lower output ripple. Parasitic parameters on the power distribution network of the circuit board may actually constitute a second-order filter. The second-order filter causes more phase lag than the first-order filter, so the feedback loop bandwidth is usually designed conservatively to ensure system stability. In order to have 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 of setting a low-frequency feedback at the output end of the second-order filter in the feedback loop, and detecting a high-frequency signal at the output end of the first-order filter, which ensures 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-order filter. SUMMARY

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

[0004] The technical scheme of the application is as follows:

[0005] The control method of the switching DC converter with high response speed characteristics, the switching DC converter internally includes a power switching device and a first-order filter, and the output of the switching DC converter is output to a load through a second-order filter; the control method comprises the following steps:

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

[0007] S2, obtaining a feedback voltage signal FB of the load, comparing FB and 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, defined as a first modulation signal MOD, inputting the first modulation signal MOD to a pulse modulator;

[0009] S4, detecting an electrical signal in the switching DC converter, defined as a second modulation signal CS, inputting the second modulation signal CS to the pulse modulator;

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

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

[0012] Detecting the current signal of the power switching device or detecting the current signal of the related device in the first-stage filter.

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

[0014] Further, the second modulation signal CS is obtained by detecting the inductance current signal in the first-stage filter, and the pulse modulator comprises a comparator, a pulse signal generator, and a periodic ramp compensation signal Ramp, the Ramp and the second modulation signal CS are added and input to the negative input end of the comparator, the first modulation signal MOD is input to the positive input end of the comparator, and the output end of the comparator is input to the pulse signal generator to generate the control pulse signal.

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

[0016] Further, the power switching device inside the switching DC converter is multiple, and the pulse signals generated in the corresponding pulse modulators are also multiple, and each pulse signal corresponds to one power switching device.

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

[0018] The present application has the advantage 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 DRAWINGS

[0019] Figure 1 is a schematic diagram of a conventional circuit structure.

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

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

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

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

[0024] The present application will be described in detail below with reference to the accompanying drawings.

[0025] A conventional switching power converter circuit structure with two-stage filter is shown in Figure 1 . The basic switching converter contains power switching devices and inductors, capacitors and / or transformer elements. A controller detects the voltage at the output terminal Vout_remote through the FB signal terminal, and generates one or more pulse signals through operation. These pulse signals control the switching of the power devices, and adjust the Vout_remote voltage at the output of the second-stage filter to reach the target voltage set by the controller.

[0026] The control system used in the present application is shown in Figure 2 . The basic switching converter contains power switching devices and inductors, capacitors and / or transformer elements. The voltage difference across the second-stage filter is detected and sent to an inverse calculation circuit module. This module can be constructed by an analog circuit, or by a digital circuit. 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 EA, added to the FW signal to become the MOD signal, which is sent to the pulse modulator controlling the pulse. Pulse modulation can employ constant frequency falling edge modulation, constant frequency rising edge modulation, dual-edge modulation, constant on-time modulation, constant off-time modulation, and hysteresis modulation, etc. The input signal of the pulse width / frequency modulator also includes the current sensing signal CS from the switching converter. This can be the current sensing signal of the inductor or transformer in the power switching circuit, or the current sensing signal of the switching device or other branches. Optionally, the pulse width modulator can include a periodic ramp compensation signal Ramp to achieve better loop stability and noise immunity. One or more pulse signals D output by the pulse width modulator control the switching of one or more power devices in the switching converter, achieving accurate and rapid adjustment of the Vout_remote voltage at the load end.

[0028] Example 1

[0029] like Figure 3 As shown, the power switching circuit topology in this example is a single-phase boost converter. A second-stage filter, consisting of an inductor, two resistors, and a capacitor, exists between its output voltage Vout and the load. The current of the power switch is detected as the CS signal. The signal between the input and output of the second-stage filter is amplified by an amplifier, where reactances Z1-Z4 can be appropriately designed to produce suitable zeros, poles, and gain for adjusting the output FW signal. The load voltage is fed to the controller's FB terminal via a feedback circuit. The error between this signal and the reference voltage VREF is amplified and compensated by OTA, then added to the FW signal to become the input MOD of the pulse width modulator. The pulse width modulator compares the CS signal and an optional sawtooth wave signal added to MOD, triggering an RS flip-flop to generate a pulse signal D, controlling the switching of the power transistor.

[0030] Example 2

[0031] like Figure 4As shown, the power switching circuit topology in this example is a two-phase parallel buck converter. Both phases supply power to the load. A second-stage filter—containing an inductor, resistor, and two capacitors—is located between its output voltage Vout and the load. Due to structural similarity, the circuit relationship is described using the first-phase circuit. 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 a reactance network consisting of Z7-10 (for example only). Two nodes in the network are used to indirectly detect the current of the second-stage filter. They are connected to an amplifier, and the reactances Z1-Z4 around the amplifier can be appropriately designed to generate suitable zeros, poles, and gain for adjusting the output FW signal. The voltage at the load end is fed to the FB terminal of the controller via a feedback circuit. The error between this signal and the reference voltage VREF is amplified by EA and added to the FW signal to become the input MOD of the pulse width modulator. The pulse width modulator compares the CS1 signal and an optional sawtooth wave signal added to MOD, triggering a monostable generator to generate a pulse signal D1, controlling the switching of the power transistor 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 transistor M2.

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

[0033] Example 3

[0034] like Figure 5 As shown, in this example, the current detection of the two-phase parallel buck converter is located at the connection point of the two inductors, obtaining the CS_total detection signal. The VOUT_remote signal, after passing through the feedback network, is added to MOD and sent to a comparator. This comparator is then compared with the current detection and reference voltage signals, triggering a monostable multivibrator. The pulses generated by the triggers are then distributed by a pulse distributor to drive the power transistors of the two phases respectively.

Claims

1. A switching DC converter control method having a high response speed characteristic, the switching DC converter internally including a power switching device and a first stage filter, the output of the switching DC converter being output to a load after passing through a second stage filter; characterized by, The control method comprises: S1, detecting the difference of the electrical signals at the input and output ends of the second filter, defining the detection signal as FW; S2, obtaining the feedback voltage signal FB of the load, comparing FB and the reference voltage VREF through the error amplifier, and defining the output of the error amplifier as the feedback control signal; S3, adding the detection signal FW and the feedback control signal to obtain the pulse modulation signal, defining the first modulation signal as MOD, and inputting the first modulation signal MOD to the pulse modulator; S4, detecting the electrical signal in the switching DC converter, defining the second modulation signal as CS, and inputting the second modulation signal CS to the pulse modulator; S5, generating the control pulse signal in the pulse modulator under the joint action of the first modulation signal MOD and the second modulation signal CS, and using the control pulse signal to control the power switching device in the switching DC converter.

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

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

4. The switching DC converter control method with high response speed characteristics according to claim 2, characterized by, When the second modulation signal CS is obtained by detecting the inductor current signal in the first filter, the pulse modulator comprises a comparator, a pulse signal generator, and a periodic ramp compensation signal Ramp, the Ramp is added to the second modulation signal CS and then input to the negative input end of the comparator, the first modulation signal MOD is input to the positive input end of the comparator, and the output end of the comparator is input to the pulse signal generator to generate the control pulse signal.

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

6. The switching DC converter control method with high response speed characteristics according to claim 1, characterized by, The power switching device inside the switching DC converter is multiple, and the pulse signals generated in the corresponding pulse modulators are also multiple, and each pulse signal corresponds to one power switching device.

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