CN102332823A

CN102332823A - Adaptive turnon time control circuit suitable for high-frequency step-down voltage converter

Info

Publication number: CN102332823A
Application number: CN201110263743A
Authority: CN
Inventors: 虞佳乐; 吕旦竹; 洪志良
Original assignee: Fudan University
Current assignee: Fudan University
Priority date: 2011-09-07
Filing date: 2011-09-07
Publication date: 2012-01-25
Anticipated expiration: 2031-09-07
Also published as: CN102332823B

Abstract

The invention belongs to the technical field of integrated circuit design, in particular to an adaptive turnon time control circuit for a high-frequency step-down voltage converter. The step-down voltage converter circuit consists of a power level circuit and a control level circuit, wherein the power level circuit consists of a power tube PMOS (P-channel metal oxide semiconductor), an NMOS (N-channel metal oxide semiconductor), a filtering inductor and a capacitor; and the control level circuit consists of a comparator, a control logic and an adaptive turnon time control circuit module. The adaptive turnon time control circuit consists of a frequency/phase discriminator, a charge pump-based low-pass filter and a voltage control delay unit, and is used for generating the turnon time of each cycle of the converter; and the adaptive turnon time control circuit and the control logic form a negative feedback loop for a DUTY signal so as to lock the switch frequency. In the invention, the turnon time control is superior to the traditional current or voltage mode control; and the adaptive turnon time control circuit is rapid in response and simple in structure, and can be applied to the power management chips of various portable electronic devices.

Description

Be applicable to the self adaptation ON time control circuit of high frequency voltage descending type voltage converter

Technical field

The invention belongs to the IC design technical field; Be specifically related to a kind of self adaptation ON time control circuit that is used for high frequency voltage descending type voltage converter, this circuit can be applied to such as in the battery powered portable sets such as mobile phone, panel computer, personal digital assistant.

Background technology

In current consumer electronics market, battery powered portable set such as smart mobile phone, panel computer, personal digital assistant etc. are being played the part of more and more important role in people's life.Therefore, the efficient voltage reducing type dc voltage changer as PMU has become the requisite module that prolongs lifetime of system.Receive device miniaturization and driving cheaply, switch power converter steps into the high frequency field gradually, to reduce the volume such as external passive devices such as inductance, electric capacity.Therefore high frequency voltage descending type direct current transducer has become follow-on designer trends, has broad application prospects.

And require controller that littler time-delay, bigger bandwidth and quicker response are arranged for high frequency voltage descending type direct current transducer.Rely on its congenital simple circuit configuration, transient response and need not complicated compensating element, fast as a kind of ON time control model of sluggishness control, just replacing the favor that traditional current-mode or voltage mode receive the design office.But there is the unfixed problem of switching frequency that receives factor affecting such as input and output voltage and transmission delay in this control method itself, and this problem can cause serious EMI problem, makes the application of transducer be restricted.

The present invention is directed to the self adaptation ON time controller that is applied in the high frequency voltage descending type direct current transducer; Effect through self adaptation ON time control circuit; When input, output voltage or loading condition change; Can make switching frequency be locked in required frequency through automatic adjusting, solve the unfixed problem of traditional sluggish mode switch frequency, make DUTY signal and clock signal clock simultaneously along synchronously.Therefore can widen ON time control model and even the application of sluggish pattern in high frequency voltage descending type direct current transducer.

Summary of the invention

The object of the present invention is to provide a kind of self adaptation ON time control circuit that is applicable to high frequency voltage descending type electric pressure converter, to solve the unfixed problem of switching frequency in traditional control.

The self adaptation ON time control circuit that is applicable to high frequency voltage descending type electric pressure converter provided by the invention; Said voltage-dropping type voltage translator circuit is made up of power stage and controlled stage circuit, and wherein power stage is made up of power tube PMOS, NMOS and filter inductance, electric capacity; Controlled stage is made up of modules such as comparator, control logic, self application ON time control circuits, and its structure is seen shown in Figure 1.Said self adaptation ON time control circuit is used to produce the ON time in each cycle of transducer by phase frequency detector (PFD), form based on the low pass filter (CPLPF) and the voltage control delay unit (VCD) of charge pump, and its structure is seen shown in Figure 1.Wherein phase frequency detector (PFD) is by two d type flip flop (D1; D2) and one form with door (AND); Two d type flip flop D ends all connect high potential (VDD); CK end connects CLK signal (clock signal) and DUTY signal (duty cycle signals) respectively, is output as UP signal (rising index signal) and DW signal (decline index signal), passes through and door (AND) two d type flip flops that reset; Form by two current source I1 and I2, two switch S 1 and S2, resistance R p, two capacitor C 1 and CP based on the low pass filter (CPLPF) of charge pump; Voltage control delay unit (VCD) by two transistors forming current mirror (M1, M2) and two transistors discharging and recharging of control capacitance C2 (M3, M4), capacitor C 2 and comparator (CMP) form; Said self adaptation ON time control circuit and control logic form feedback loop to the DUTY signal, thereby realize the locking to switching frequency.

Among the present invention, the ON time in each cycle is the time that capacitor C 2 charges to threshold value VTH.Phase frequency detector produces UP signal (rising index signal) and DW signal (decline index signal) through the rising edge that comparator (CMP) compares DUTY signal (duty cycle signals) and CLK signal (clock signal); Thereby control based on switch S in the low pass filter of charge pump 1 or S2, respectively conducting current source I1 or I2; Therefore the charging charge on the capacitor C 1 changes; This module output, just the threshold voltage VTH of voltage-controlled delay unit changes accordingly, the charging interval of control capacitance C2; Thereby realize that negative feedback makes the DUTY signal align with CLK gradually, reach the purpose of locking frequency.Lead over the CLK signal like the DUTY signal elevating time, then phase frequency detector produces DW signal conduction switch S 2, and current source I2 is to capacitor C 1 discharge; Thereby threshold voltage VTH descends; ON time reduces, and the feedback loop through constituting with control logic makes DUTY align with CLK.When the factors vary such as input, output voltage or loading condition of transducer, transducer is regulated through the self adaptation of ON time control circuit, and locking switch frequency to the frequency of giving has solved the unfixed problem of switching frequency in traditional control.

Description of drawings

Fig. 1 is the circuit structure of high frequency voltage descending type dc voltage changer.

Fig. 2 is the self adaptation ON time control circuit that the present invention designs.

Fig. 3 is the steady state test figure of the high frequency voltage descending type electric pressure converter of band self adaptation ON time control circuit.

Fig. 4 is self adaptation ON time control circuit frequency lock function simulating result under the different loads situation.

Embodiment

Followingly the present invention is elaborated according to accompanying drawing and design example.

What the present invention designed is a kind of self adaptation ON time control circuit that is applied to high frequency voltage descending type dc voltage changer.The typical application structure of this circuit is as shown in Figure 1.High frequency voltage descending type dc voltage changer mainly is made up of power stage circuit and controlled stage circuit.Wherein power stage is made up of power tube PMOS, NMOS and filter inductance, electric capacity; Controlled stage is made up of modules such as comparator, control logic, self application ON time controllers.The DUTY signal that produces in the controlled stage circuit produces non-overlapped drive signal difference power controlling pipe PMOS and conducting and the shutoff of NMOS through drive circuit.When the conducting of PMOS pipe and NMOS pipe when turn-offing, the inductance left end directly connects power supply, and power supply charges to output capacitance through inductance, and inductive current rises, and output voltage rises.Behind fixing ON time, when NMOS pipe conducting and PMOS pipe turn-off, the straight adjoining land of inductance left end, output capacitance is through fly-wheel diode and inductive discharge, and inductive current descends, and output voltage descends.When output voltage drops to the VREF value when following, comparator output triggers control logic and opens PMOS once more and turn-off NMOS.And the effect of self adaptation ON time controller is carried out adaptive adjusting to switching frequency except producing a fixing ON time and through negative feedback, finally locks onto design load.

Fig. 2 is that the self adaptation ON time produces the detailed structure chart of circuit.Self adaptation ON time control circuit is used to produce the ON time in each cycle of transducer by phase frequency detector (PFD), form based on the low pass filter (CPLPF) and the voltage control delay unit (VCD) of charge pump.Self adaptation ON time control circuit and control logic form feedback loop to the DUTY signal, thereby realize the locking to switching frequency, have solved the problem that switching frequency changes with input and output voltage and loading condition in the traditional control method.Its operation principle is following: the ON time in each cycle is the time that capacitor C 2 charges to threshold value VTH.Phase frequency detector produces UP and DW signal through the rising edge that compares DUTY signal and CLK signal, thereby controls based on switch S in the low pass filter of charge pump 1 or S2, respectively conducting current source I1 or I2.Therefore the charging charge on the capacitor C 1 changes; This module output, just the threshold voltage VTH of voltage-controlled delay unit changes accordingly, the charging interval of control capacitance C2; Thereby realize that negative feedback makes the DUTY signal align with CLK gradually, reach the purpose of locking frequency.Lead over the CLK signal like the DUTY signal elevating time, then phase frequency detector produces DW signal conduction switch S 2, and current source I2 is to capacitor C 1 discharge; Thereby threshold voltage VTH descends; ON time reduces, and the feedback loop through constituting with control logic makes DUTY align with CLK.

Fig. 3 is the steady state test figure of the high frequency voltage descending type electric pressure converter of band self adaptation ON time control circuit.It is thus clear that self adaptation ON time control circuit is with the good stuck-at-0MHz of the switching frequency of transducer, stability still can under the stable state.

Fig. 4 is self adaptation ON time control circuit frequency lock function simulating result under the different loads situation.It is thus clear that in wide output loading 0 ~ 1500mA scope, the self adaptation ON time control circuit that is designed can be good near the switching frequency stuck-at-0MHz with transducer, its error range can be controlled in about 1%.And the same transducer of inapplicable this self adaptation ON time control circuit, it is bigger that its switching frequency changes in whole load variations scope, and frequency error can reach more than 10%.

Claims

1. self adaptation ON time control circuit that is applicable to high frequency voltage descending type electric pressure converter, said voltage-dropping type voltage translator circuit is made up of power stage and controlled stage circuit, and wherein power stage is made up of power tube PMOS, NMOS and filter inductance, electric capacity; Controlled stage is made up of comparator, control logic, self application ON time control circuit module; It is characterized in that said self adaptation ON time control circuit by phase frequency detector (PFD), form based on the low pass filter (CPLPF) and the voltage control delay unit (VCD) of charge pump, is used to produce the ON time in each cycle of transducer; Wherein phase frequency detector (PFD) is by two d type flip flop (D1; D2) and one form with door (AND); Two d type flip flop D ends all connect high potential (VDD); CK end meets clock signal clk and duty cycle signals DUTY respectively, is output as rising index signal UP signal and decline index signal DW signal, passes through and door (AND) two d type flip flops that reset; Form by two current source I1 and I2, two switch S 1 and S2, resistance R p, two capacitor C 1 and CP based on the low pass filter (CPLPF) of charge pump; Voltage control delay unit (VCD) by two transistors forming current mirror (M1, M2) and two transistors discharging and recharging of control capacitance C2 (M3, M4), capacitor C 2 and comparator (CMP) form; Said self adaptation ON time control circuit and control logic form feedback loop to the DUTY signal, thereby realize the locking to switching frequency.

2. self adaptation ON time control circuit according to claim 1, it is characterized in that: the ON time in each cycle is the time that capacitor C 2 charges to threshold value VTH; Phase frequency detector produces UP signal and DW signal through the rising edge that comparator (CMP) compares DUTY signal and CLK signal, thereby controls based on switch S in the low pass filter of charge pump 1 or S2, respectively conducting current source I1 or I2; Charging charge on the capacitor C 1 changes, this module output, just threshold voltage V of voltage-controlled delay unit _THChange accordingly, the charging interval of control capacitance C2, thus realize that negative feedback makes the DUTY signal align with CLK gradually, reach the purpose of locking frequency.