TWI809517B - Constant current switching power supply and its control chip - Google Patents

Abstract

Provided are a constant current switching power supply and a control chip thereof. A control chip for a constant current switching power supply includes: a current sensing module configured to generate a current sensing signal based on a switching current signal representing a current flowing through a power switch in the constant current switching power supply; a clamp element control module The group is configured to generate a clamp element control signal based on the current sensing signal and the gate detection signal representing the turn-on and turn-off of the power switch; and the switch control module is configured to: based on the output representing the constant-current switching power supply The output feedback signal of the voltage and the first reference voltage generate an error amplification signal, and based on the clamp element control signal, the error amplification signal is controlled to charge the error representation capacitor to generate an error representation signal, and based on the current sensing signal, the error representation signal, and the constant The frequency oscillation signal generates the gate drive signal.

Description

Constant current switching power supply and its control chip

The invention relates to the field of circuits, in particular to a constant current switching power supply and a control chip thereof.

Switching power supply, also known as switching power supply and switching converter, is a kind of power supply. The function of the switching power supply is to convert a level of voltage into a user-side required voltage or current.

Usually, switching power supply is used for AC to DC (AC/DC) or DC to DC (Direct Current, DC/DC) conversion, and mainly includes the following circuit parts: Electromagnetic Interference (EMI) filter circuit, rectification filter circuit , a power conversion circuit, a pulse width modulation (Pulse Width Modulation, PWM) control circuit, an output rectification filter circuit, etc., wherein the PWM control circuit is mainly implemented by a PWM control chip.

A control chip for a constant current switching power supply according to an embodiment of the present invention includes: a current sensing module configured to generate current sensing based on a switch current signal representing a current flowing through a power switch in a constant current switching power supply signal; the clamp element control module is configured to generate the clamp element control signal based on the current sensing signal and the gate detection signal representing the turn-on and turn-off of the power switch; and the switch control module is configured to: based on The output feedback signal representing the output voltage of the constant current switching power supply and the first reference voltage generate an error amplification signal, control the error amplification signal to charge the error representation capacitor based on the clamp element control signal to generate the error representation signal, and based on the current sensing signal , the error characterization signal, and the fixed-frequency oscillation signal generate a gate drive signal.

The constant current switching power supply according to the embodiment of the present invention includes the above-mentioned constant current Control chip for switching power supply.

According to the control chip used for the constant current switching power supply according to the embodiment of the present invention, the clamping element control signal is generated based on the current sensing signal and the gate detection signal, and the error characteristic signal is clamped based on the clamping element control signal, which can speed up The loop response speed of the constant current switching power supply during the load dynamic response process can suppress the overshoot of the output current of the constant current switching power supply during the load dynamic response process, thereby reducing or avoiding damage to the load of the constant current switching power supply.

100,200: constant current switching power supply

Q1, Q21: power switch

L1, L21: inductance

D21: Freewheeling diode

D11: Freewheeling diode

D1: Trigger

C2, C22: output capacitor

R1, R21: feedback detection resistor

Vout: output voltage

102,202: control chip

FB: output feedback signal

R2, R22: current sensing resistors

qc: switch current signal

1022, 2026-1: error amplifier

Vref_ea: reference voltage

COMP: error amplification signal

1024,2022: Current Sensing Module

CS: current feedback sensing terminal

CS_i: current sensing signal

1026, 2026-2: Oscillators

CLK: fixed frequency oscillation signal

1028, 2026-3: PWM Comparator

off,OFF: turn off the control signal

ramp, RAMP: slope compensation signal

C3.C23: Error Characterization Capacitance

1030, 2026-4: control logic module

CTL: switch control signal

1032,2026-5: gate driver

GATE: gate drive signal

Iout: output current

VOUT: 200 output voltage

QC: switch current signal

2024: Clamp element control module

2026: Switch control module

GATE_SENSE: Gate detection signal

DCC: clamp element control signal

VREF_EA: the first reference voltage

COMP_D: error characterization signal (voltage)

D_max: maximum working factor indication signal

OCP_ref: Second reference voltage

OCP_s: overcurrent protection signal

CMP1, CMP3: Comparator

OCP_i: Overcurrent indication signal

OCP_p: initial overcurrent protection signal

D2,D3,D4,D5: triggers

P1: circuit

OCP1: Over-current protection signal every other cycle

CMP2: OCP comparator

SW1, SW2: switch

COMP_p: error control signal

Ib1: pull-down current source

COMP_c: Error comparison signal

The present invention can be better understood from the following description of specific embodiments of the present invention in conjunction with the accompanying drawings, wherein:

FIG. 1 shows a schematic circuit diagram of a system control part of a traditional constant-current switching power supply with a constant operating frequency and a BOOST architecture.

FIG. 2 shows a timing diagram of various signals related to the circuit shown in FIG. 1 .

Fig. 3 shows a schematic circuit diagram of the system control part of the constant current switching power supply according to the embodiment of the present invention.

FIG. 4 shows a timing diagram of various signals related to the circuit shown in FIG. 3 .

Fig. 5 shows the logical block diagram of the clamp element control module shown in Fig. 3;

FIG. 6 shows an example implementation circuit diagram of the clamp element control module shown in FIG. 3 .

FIG. 7 shows an example implementation circuit diagram of the clamp element control module shown in FIG. 3 .

FIG. 8 shows a schematic diagram of a clamping element implementation circuit that may be included in the switch control module shown in FIG. 3 when the clamping element control module shown in FIG. 3 adopts the implementation circuit shown in FIG. 7 .

Features and exemplary embodiments of various aspects of the invention will be described in detail below. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced without some of these specific details. The following description of the embodiments is only to provide a better understanding of the present invention by showing examples of the present invention. The present invention is by no means limited to the following Any specific configurations and algorithms are presented, but rather any modifications, substitutions, and improvements of elements, components, and algorithms are covered without departing from the spirit of the invention. In the drawings and the following description, well-known structures and techniques have not been shown in order to avoid unnecessarily obscuring the present invention.

Fixed-frequency switching power supply is a switching power supply with constant operating frequency. Its advantages include: the operating frequency of the power switch will not change with the change of inductance, which is convenient for the selection of inductance; the working factor of the gate drive voltage used to drive the power switch In the lower case, the entire circuit system works in discontinuous conduction mode (Discontinuous Conduction Mode, DCM), with small effective current and high efficiency. However, during the load dynamic response process, due to the limitation of the loop response speed, the output voltage or output current of the fixed-frequency switching power supply is prone to overshoot, which may cause load damage in severe cases.

FIG. 1 shows a schematic circuit diagram of a system control part of a conventional constant-current switching power supply 100 with a constant operating frequency and a boost architecture. As shown in Figure 1, when the power switch Q1 is in the on state, the inductor L1 stores energy; when the power switch Q1 is in the off state, the energy stored in the inductor L1 is charged to the output capacitor C2 through the freewheeling diode D11; The feedback detection resistor R1 detects the output feedback signal FB representing the output voltage Vout of the constant current switching power supply 100 and transmits the detected output feedback signal FB to the output feedback signal FB of the PWM control chip 102; the current detection resistor R2 detects and represents the flowing power Switch the current switching current signal qc of the switch Q1 and transmit the detected switching current signal qc to the current feedback sensing terminal CS of the PWM control chip 102 .

In the PWM control chip 102 shown in FIG. 1 , the error amplifier 1022 generates the error amplification signal COMP based on the output feedback signal FB and the reference voltage Vref_ea; the current sensing module 1024 generates the current sensing signal CS_i based on the switching current signal qc; the oscillator 1026 generates a constant frequency oscillation signal CLK; the PWM comparator 1028 generates an off control signal off (for example, constant The frequency oscillation signal CLK and the current sensing signal CS_i are superimposed to generate the slope compensation signal ramp, the error amplification signal COMP charges the error representation capacitor C3 to generate the error representation voltage COMP_D, and the PWM comparator 1028 compares the slope compensation signal ramp with the error representation voltage COMP_D Generate shutdown control signal off); control logic module The group 1030 generates a switch control signal CTL for controlling the turn-on and turn-off of the power switch Q1 based on the turn-off control signal off and the constant frequency oscillation signal CLK; the gate driver 1032 generates a switch control signal CTL for driving the power switch Q1 based on the switch control signal CTL and turn off the gate drive signal GATE.

FIG. 2 shows a timing diagram of various signals related to the circuit shown in FIG. 1 . It can be seen from FIG. 2 that during the load dynamic response process when the reference voltage Vref_ea is switched from a low voltage to a high voltage: the output current Iout of the constant current switching power supply 100 increases from a small current to a large current, and the error characterization signal COMP_D changes from The low voltage increases to a high voltage, and the current sensing signal CS_i also increases from a low voltage to a high voltage, which will cause the constant current switching power supply 100 to appear in an over-current protection (Over Current Protection, OCP) state or a maximum operating factor state (ie , the gate drive signal GATE used to drive the on and off of the power switch Q1 has a maximum operating factor); during the voltage rollback process of the error characterization signal COMP_D falling from a high voltage to a steady-state voltage, the constant current switching power supply 100 is still In the OCP state or the state of the maximum operating factor, the insufficient loop response speed will cause the voltage rollback process to take a long time, causing the output current Iout of the constant current switching power supply 100 to overshoot seriously, and even damage the constant current switching power supply 100 load risk.

In view of the above-mentioned one or more problems existing in the constant current switching power supply 100, a constant current switching power supply and its control chip are proposed to suppress the overshoot of the output current of the constant current switching power supply during the load dynamic response process of the constant current switching power supply , thereby reducing or avoiding damage to the load of the constant current switching power supply.

FIG. 3 shows a schematic circuit diagram of a system control part of a constant current switching power supply 200 according to an embodiment of the present invention. In the constant current switching power supply 200 shown in Figure 3, when the power switch Q21 is in the on state, the inductor L21 stores energy; when the power switch Q21 is in the off state, the energy stored in the inductor L21 passes through the freewheeling diode D21 charge to the output capacitor C22; the feedback detection resistor R21 detects the output feedback signal FB representing the output voltage VOUT of the constant current switching power supply 200 and transmits the sensed output feedback signal FB to the output feedback signal FB of the PWM control chip 202; the current The sensing resistor R22 senses the switch current signal QC representing the current flowing through the power switch Q21 and transmits the sensed switch current signal QC to the current feedback sensing terminal CS of the PWM control chip 202 .

In the constant current switching power supply 200 shown in FIG. 3 , the control chip 202 includes a current sensing module 2022 , a clamp element control module 2024 , and a switch control module 2026 . The current sensing module 2022 is configured to generate the current sensing signal CS_i based on the switch current signal QC. The clamp control module 2024 is configured to generate the clamp control signal DCC based on the current sensing signal CS_i and the gate drive signal GATE_SENSE representing the on and off of the power switch Q21 . The switch control module 2026 is configured to generate the error amplification signal COMP based on the output feedback signal FB and the first reference voltage VREF_EA, and control the charging of the error amplification signal COMP to the error representation capacitor C23 based on the clamp element control signal DCC to generate the error representation signal COMP_D , and the gate driving signal GATE is generated based on the clamp element control signal DCC, the error characterization signal COMP_D, and the constant frequency oscillation signal CLK.

FIG. 4 shows a timing diagram of various signals related to the circuit shown in FIG. 3 . It can be seen from FIG. 4 that during the load dynamic response process when the first reference voltage VREF_EA is switched from a low voltage to a high voltage: as the current sensing signal CS_i rises, the constant current switching power supply 200 appears OCP or maximum In the working factor state, the clamping element control module 2024 triggers the clamping element for the error characteristic signal COMP_D, so that the error characteristic signal COMP_D is clamped near the voltage determined by the OCP or the maximum operating factor state, preventing the error characteristic signal COMP_D continues to rise to a higher voltage, so that the error signal COMP_D can quickly reach a steady-state voltage when the voltage rolls back, which has a significant inhibitory effect on the output current or output voltage overshoot of the constant-current switching power supply 200 .

It can be seen from the above description that during the dynamic load response process of the constant current switching power supply 200, the control chip 202 generates the clamp element control signal DCC based on the current sensing signal CS_i and the gate detection signal GATE_SENSE and controls the clamp element based on the clamp element. The signal DCC clamps the error characterization signal COMP_D, which can speed up the loop response speed of the constant current switching power supply 200, suppress the overshoot of the output current of the constant current switching power supply 200, thereby reducing or avoiding the impact on the constant current switching power supply 200. damage to the load.

In some embodiments, the switch control module 2026 can be further configured to generate a slope compensation signal by superimposing the constant frequency oscillation signal CLK and the current sensing signal CS_i RAMP is compared with the error characterization signal COMP_D to generate a turn-off control signal OFF for controlling the turn-off of the power switch Q21; based on the turn-off control signal OFF and the constant frequency oscillation signal CLK, a switch control for controlling the turn-on and turn-off of the power switch Q21 is generated a signal CTL; and generating a gate drive signal GATE based on the switch control signal CTL.

As shown in FIG. 3 , in some embodiments, the switch control module 2026 includes an error amplifier 2026-1, an oscillator 2026-2, a PWM comparator 2026-3, a control logic module 2026-4, and a gate driver 2026 -5, wherein: the error amplifier 2026-1 generates the error amplification signal COMP based on the output feedback signal FB and the first reference voltage VREF_EA; the oscillator 2026-2 generates the fixed frequency oscillation signal CLK; the PWM comparator 2026-3 compares the fixed frequency The oscillation signal CLK and the current sensing signal CS_i are superimposed to generate the slope compensation signal RAMP and the error representation signal COMP_D to generate the shutdown control signal OFF; the control logic module 2026-4 is based on the shutdown control signal OFF and the fixed frequency oscillation signal CLK to generate The switch control signal CTL; the gate driver 2026-5 generates the gate drive signal GATE based on the switch control signal CTL.

FIG. 5 shows a logic block diagram of the clamp control module 2024 shown in FIG. 3 . As shown in FIG. 5 , in some embodiments, the clamp element control module 2024 includes a maximum operation factor detection unit, an OCP detection unit, and a control signal generation unit, wherein: the maximum operation factor detection unit is configured based on a fixed frequency oscillation The signal CLK and the gate detection signal GATE_SENSE generate a maximum operating factor indication signal D_max; the OCP detection unit is configured to generate an overcurrent protection signal OCP_s based on the current sensing signal CS_i and the second reference voltage OCP_ref; the control signal generation unit is configured to Based on the overcurrent protection signal OCP_s and the maximum operation factor indication signal D_max, the clamp element control signal DCC is generated. Here, the maximum operation factor sensing unit can detect whether the constant current switching power supply 200 is in the maximum operation factor state, and the OCP detection unit can detect whether the constant current switching power supply 200 is in the OCP state, so the control signal generation unit can be based on the constant current switching power supply Whether the 200 is in the maximum operating factor state and/or the OCP state to generate the clamp element control signal DCC.

FIG. 6 shows an example implementation circuit diagram of the clamp element control module 2024 shown in FIG. 3 . As shown in FIG. 6, in some embodiments, flip-flop D1 detects the gate detection signal When the duty factor of GATE_SENSE reaches the duty factor of the constant-frequency oscillation signal CLK, a maximum duty factor indication signal D_max is generated. The comparator CMP1 passes the current sense signal CS_i

Compared with the second reference voltage OCP_ref to generate an over-current indication signal OCP_i. The over-current indication signal OCP_i generates an initial over-current protection signal OCP_p after being shielded by Leading Edge Blanking (LEB). The initial over-current protection signal OCP_p is processed by the flip-flops D2 and D3 and the pulse generating circuit P1 to generate the over-current protection signal OCP_S at intervals. The clamp control signal DCC is generated after the periodic over-current protection signal OCP_S and the maximum duty factor indication signal D_max are logically ORed.

In some embodiments, when the clamp control signal DCC is at a high level, the error amplification signal COMP is enabled to charge the error representation capacitor C23; when the clamp control signal DCC is at a low level, the error amplification signal COMP is disabled to charge the error Characterizes the charging of capacitor C23. Here, the voltage on the error representation capacitor C23 is the error representation signal COMP_D.

FIG. 7 shows another example implementation circuit diagram of the clamp element control module 2024 shown in FIG. 3 . As shown in Figure 7, in some embodiments, flip-flop D5 senses

The maximum duty factor indication signal D_max is generated when the duty factor of the gate detection signal GATE_SENSE reaches the oscillation ratio of the constant frequency oscillation signal CLK. The comparator CMP2 generates the over-current indication signal OCP_i by comparing the current sensing signal CS_i with the second reference voltage OCP_ref. The overcurrent protection signal OCP_s is generated after the overcurrent indication signal OCP_i is shielded by leading edge blanking (LEB). The over-current protection signal OCP_s and the maximum operation factor indication signal D_max are logically ORed to generate the clamp control signal DCC through the flip-flop D4.

In the exemplary implementations shown in FIGS. 6 and 7 , since the clamp control signal DCC is generated by performing a logical OR on the overcurrent protection signal OCP_s and the maximum operating factor indication signal D_max, no matter whether the constant current switching power supply 200 is in the OCP The clamp control signal DCC can clamp the error characterization signal COMP_D either in the maximum working factor state or in the maximum working factor state.

FIG. 8 shows a schematic diagram of a clamping element implementation circuit that may be included in the switch control module 2026 shown in FIG. 3 when the clamping element control module 2024 shown in FIG. 3 adopts the implementation circuit shown in FIG. 7 . Clamp element control signal DCC control switch SW1 for error amplification signal COMP is performed to generate the error control signal COMP_p. The comparator CMP3 compares the error representation signal COMP_D with the error control signal COMP_p and controls the switch SW2 to turn on when the error representation signal COMP_D is greater than the error control signal COMP_p. The error representation signal is compared by the pull-down current source Ib1 COMP_D for control.

It can be seen from FIG. 8 that in some embodiments, the switch control module 2026 can be further configured to: control the error amplification signal COMP based on the clamp element control signal DCC to generate the error control signal COMP_p; The signal COMP_D is compared with the error control signal COMP_p to generate an error comparison signal COMP_c; and based on the error comparison signal COMP_c, the error amplification signal COMP is controlled to discharge the error representation capacitor C23.

In summary, compared with the constant current switching power supply 100 shown in FIG. 1, the constant current switching power supply 200 shown in FIG. Its function is to control the increase of the error representation signal COMP_D during the load dynamic response process of the constant current switching power supply 200, making it easier for the error representation signal COMP_D to return to the steady-state voltage, thereby suppressing the overshoot of the output current and reducing the impact on the load. damage.

The present invention may be embodied in other specific forms without departing from its spirit and essential characteristics. For example, the algorithms described in certain embodiments may be modified without departing from the basic spirit of the invention in terms of system architecture. Therefore, the present embodiments are to be considered in all respects as illustrative rather than restrictive, the scope of the present invention is defined by the appended claims rather than the above description, and, within the meaning and equivalents of the claims, All changes in scope are thereby embraced within the scope of the invention.

200: constant current switching power supply

VIN: input voltage

C21: Input capacitance

L21: Inductance

D21: Freewheeling diode

VOUT: 200 output voltage

Iout: 100 output current

C22: output capacitor

2026-2: Oscillators

CLK: fixed frequency oscillation signal

RAMP: slope compensation signal

2026-3: PWM Comparator

OFF: Turn off the control signal

2026-4: Control Logic Module

CTL: switch control signal

2026-5: Gate driver

GATE: gate drive signal

Q21: Power switch

R22: current sense resistor

COMP_D: error characterization signal (voltage)

2026-1: Error Amplifier

CS: current feedback sensing terminal

CS_i: current sensing signal

COMP: error amplification signal

VREF_EA: the first reference voltage

C23: Error Characterization Capacitance

FB: output feedback signal

2026: Switch control module

2022: Current Sensing Module

QC: switch current signal signal

GATE_SENSE: Gate gate detection sense signal signal

2024: Clamp element control module

DCC: clamp element control signal

202: control chip

R21: feedback detection sense resistor

Claims (10)

A control chip for a constant current switching power supply, comprising: a current sensing module configured to generate a current sensing signal based on a switching current signal representing a current flowing through a power switch in the constant current switching power supply; The bit control module is configured to generate a clamp element control signal based on the current sensing signal and the gate detection signal representing the turn-on and turn-off of the power switch; and the switch control module is configured to: Based on the output feedback signal representing the output voltage of the constant current switching power supply and the first reference voltage, an error amplification signal is generated, and based on the clamp element control signal, the error amplification signal is controlled to charge the error representation capacitor to generate an error. A representative signal, and based on the current sensing signal, the error representative signal, and the constant frequency oscillation signal, the gate driving signal is generated. The control chip according to claim 1, wherein the clamp element control module is further configured to: generate an overcurrent protection signal based on the current sensing signal and the second reference voltage; generate an overcurrent protection signal based on the fixed frequency oscillation signal and the gate detection signal to generate a maximum operating factor indication signal; and based on the overcurrent protection signal and the maximum operating factor indication signal to generate the clamp element control signal. The control chip according to claim 2, wherein the clamp element control module is further configured to: generate the clamp element control signal. The control chip according to claim 2, wherein the clamp element control module is further configured as: An over-current indication signal is generated by comparing the current sensing signal with the second reference voltage; and the over-current protection signal is generated by blanking the leading edge of the over-current indication signal. The control chip according to claim 2, wherein the clamp element control module is further configured to: when sensing that the duty factor of the gate detection signal reaches the duty factor of the fixed frequency oscillation signal, Generate the maximum work factor indication signal. The control chip according to claim 1, wherein the switch control module is further configured to: generate a slope compensation signal and the error representation signal by superimposing the fixed frequency oscillation signal and the current sensing signal making a comparison, generating a turn-off control signal for controlling the turn-off of the power switch; generating a switch control signal for controlling the turn-on and turn-off of the power switch based on the turn-off control signal and the fixed-frequency oscillation signal; and Based on the switch control signal, the switch driving signal is generated. The control chip according to claim 1, wherein the switch control module is further configured to: enable the error amplification signal to charge the error representation capacitor when the clamp element control signal is at a high level ; When the clamp element control signal is at low level, prohibiting the error amplification signal from charging the error representation capacitor, wherein the voltage on the error representation capacitor is used as the error representation signal. The control chip according to claim 1, wherein the switch control module is further configured to: control the error amplification signal based on the clamp element control signal to generate an error control signal; The error characterization signal is compared with the error control signal to produce an error ratio a comparison signal; and based on the error comparison signal, controlling charging of the error representation capacitor by the error amplification signal. The control chip according to claim 9, wherein the switch control module is further configured to: use a part of the error amplification signal to charge the error representation capacitor when the error comparison signal is at a high level; When the error comparison signal is at a low level, the entirety of the error amplification signal is used to charge the error representation capacitor. A constant current switching power supply, comprising the control chip for constant current switching power supply according to any one of claims 1 to 9.

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