Control method of switch direct current converter with high response speed characteristicTechnical Field
The invention belongs to the technical field of converters, and particularly relates to a control method of a switch direct current converter with high response speed characteristics.
Background
Dc voltage converters find wide application in a variety of contexts, such as industrial applications, mobile devices, automotive electronics, data centers, and the like. Common dc voltage converters, such as Buck converters, boost converters, forward converters, etc., typically have a topology with a first order filter. In practical applications, it is possible to use a second stage filter after the first stage filter to achieve lower output ripple due to ripple requirements. Parasitic parameters on the circuit board power distribution network may also actually constitute the second stage filter. The second stage filter brings more phase lag than the first stage filter, so the feedback loop bandwidth is usually designed conservatively, and the stability of the system is ensured. In order to have a more accurate static accuracy of the output voltage, document "Jindong Zhang, method of AND SYSTEM for regulating output voltage, US patent 7212012B1,2007" proposes a Method in which a low frequency feedback is provided in a feedback loop at the output of the second stage filter, while a high frequency signal is detected at the output of the first stage filter, ensuring the accuracy of the output voltage and the stability of the loop. However, these methods have the problem of slower voltage transient response at the output of the second stage filter.
Disclosure of Invention
Aiming at the problems existing in the prior art, the invention provides a control method of a switch direct current converter with high response speed characteristic.
The technical scheme of the invention is as follows:
A control method of a switching DC converter with high response speed characteristics, wherein the switching DC converter internally comprises a power switching 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, and the control method comprises the following steps:
S1, detecting an electric signal difference value at two ends of a second-stage filter, and defining the electric signal difference value as a detection signal FW;
S2, acquiring a feedback voltage signal FB of a load, comparing the 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, defining the pulse modulation signal as a first modulation signal MOD, and inputting the first modulation signal MOD into a pulse modulator;
S4, detecting an electric signal in the switch direct-current converter, defining 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 combined action of the first modulation signal MOD and the second modulation signal CS, and the power switching device in the switching direct current converter is controlled by the control pulse signal.
Further, the specific method for detecting the electric signal in the switch direct current converter is as follows:
detecting a current signal of the power switching device or detecting a current signal of an associated device in the first stage filter.
Further, the second modulation signal CS is obtained by detecting a current signal of the power switch device, and the pulse modulator includes a comparator, a pulse signal generator, and a periodic slope compensation signal Ramp, where the Ramp and the second modulation signal CS are added and input to a positive input terminal of the comparator, the first modulation signal MOD is input to a negative input terminal of the comparator, and an output terminal of the comparator is input to the pulse signal generator and generates a control pulse signal.
Further, the second modulation signal CS is obtained by detecting an inductor current signal in the first stage filter, and the pulse modulator includes a comparator, a pulse signal generator, and a periodic Ramp compensation signal Ramp, where the Ramp and the second modulation signal CS are added and input to a negative input terminal of the comparator, the first modulation signal MOD is input to a positive input terminal of the comparator, and an output terminal of the comparator is input to the pulse signal generator and generates a control pulse signal.
Further, the second modulation signal CS is obtained by detecting an output current signal in the first stage filter, and then the pulse modulator includes a three-input comparator, a pulse signal generator, and a periodic Ramp compensation signal Ramp, where the Ramp and the second modulation signal CS are added and input to a negative input terminal of the comparator, the first modulation signal MOD is input to a first positive input terminal of the comparator, the second positive input terminal of the comparator is connected to a reference voltage signal, and an output terminal of the comparator is input to the pulse signal generator and then generates a control pulse signal.
Furthermore, the plurality of power switching devices inside the switching direct current converter are arranged, pulse signals generated in the corresponding pulse modulators are also multipath, and each path of pulse signals corresponds to one power switching device.
The detection signal and the feedback signal in the scheme are signals with the same property, if the detected signals are different, the signals are converted into the signals with the same property through the conversion circuit, and finally the first modulation signal is obtained by the two signals together.
The invention has the beneficial effects that aiming at the direct current converter with two or more filters, high response speed of load switching and high loop stability are obtained.
Drawings
Fig. 1 is a schematic diagram of a conventional circuit configuration.
Fig. 2 is a schematic circuit structure of the present invention.
Fig. 3 is a schematic circuit configuration of embodiment 1.
Fig. 4 is a schematic circuit configuration diagram of embodiment 2.
Fig. 5 is a schematic circuit configuration diagram of embodiment 3.
Detailed Description
The present invention will be described in detail with reference to the accompanying drawings.
A conventional switching power converter circuit configuration with a two-stage filter is shown in fig. 1. The basic switching circuitry SWITCHING CONVERTER includes power switching devices, and inductive, capacitive, 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 operation. The pulse signals control the switch of the power device, and the Vout_remote voltage output by the second-stage filter is adjusted to reach the target voltage set by the controller.
The control system employed in the present invention is shown in fig. 2. SWITCHING CONVERTER include power switching devices, and inductive, capacitive, and/or transformer components. The voltage difference across the second stage filter is detected and sent to a circuit module inverse computation module inverse calculation. This module may be constructed from analog circuitry or may be constructed from digital circuitry. Based on the structural and parametric 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.
On the other hand, the voltage at the load terminal 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, and then supplied to a pulse Modulator for controlling the pulse. The 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, hysteresis modulation and the like. The input signal to the pulse width/frequency modulator is also the current sense signal CS from SWITCHING CONVERTER. It may be a current sense signal of an inductor or transformer in a power switching circuit, or may be a current sense signal of a switching device or other branch. Optionally, the pulse width modulator may contain a periodic Ramp compensation signal Ramp to achieve better loop stability and noise immunity. The pulse width modulator outputs one or more pulse signals D, controls the switching of one or more power devices of SWITCHING CONVERTER, and realizes accurate and rapid adjustment of the voltage of the load terminal Vout_remote.
Example 1
As shown in fig. 3, the power switching circuit topology in this example is a single-phase boost converter. A second filter is provided between its output voltage Vout and the load, comprising an inductance, two resistances and a capacitance. 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 an amplifier, wherein the reactances Z1-Z4 can be suitably designed to produce suitable pole-zero and gain for adjusting the output FW signal. The voltage of the load terminal 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 and compensated by the OTA and added to the FW signal to become the input MOD of the pulse width modulator. The CS signal and the optional sawtooth signal are added to be compared with MOD by the pulse width modulator, the RS trigger is triggered to generate a pulse signal D, and the switch of the power tube is controlled.
Example 2
As shown in fig. 4, the power switching circuit topology in this example is a two-phase parallel buck converter. The two phases together supply the load. There is a second filter between its output voltage Vout and the load-comprising an inductance, a resistance and two capacitances. Because of the structural similarity, the relationship of the circuits is described with the circuits 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 a reactive network consisting of Z7-10, by way of 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 around which the reactances Z1-Z4 can be suitably designed to produce suitable pole-zero and gain for adjusting the output FW signal. The voltage of the load terminal 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, and added to the FW signal to form the input MOD of the pulse width modulator. The pulse width modulator uses CS1 signal and optional sawtooth wave signal to add and compare with MOD, trigger monostable generator to produce pulse signal D1, control the switch of power tube M1. Similarly, the current detection signal CS2 of the power inductor L2 is compared with MOD to generate the pulse signal D2 to control the power transistor M2.
As an extension of the proposed circuit concept, the inverse calculation module may also sample the signals of more than two nodes on the two-stage filter for signal computation.
Example 3
As shown in fig. 5, in this example, the current detection of the two-phase parallel buck converter is located at the junction of the two inductors, so as to obtain the cs_total detection signal. The signal of VOUT_remote through the feedback network is added with MOD and sent to a comparator, and compared with the current detection and reference voltage signals, the monostable trigger is triggered. The pulse generated by the trigger drives the two-phase power tubes respectively through the pulse distributor.