CN201134763Y

CN201134763Y - Off-line current type PWM power source control circuit

Info

Publication number: CN201134763Y
Application number: CNU2006201444123U
Authority: CN
Inventors: 王乐康; 杜凯; 李照华; 符传汇; 贾相英
Original assignee: Shenzhen Mingwei Electronic Co Ltd
Current assignee: Shenzhen Mingwei Electronic Co Ltd
Priority date: 2006-12-31
Filing date: 2006-12-31
Publication date: 2008-10-15
Anticipated expiration: 2016-12-31

Abstract

The utility model relates to an off-line current type PWM power supply control circuit which comprises a voltage detecting circuit (U1), an oscillating circuit (U4), an under-voltage protective circuit (U3), an error amplifier (U7), a PWM comparator (U8), high-voltage switch pipes (M1 and M2), a PWM logical circuit (U5) and a drive gate (U6), wherein the circuit also comprises a time delay circuit (U2) and the U2 is crossed and connected between the U1 and a switch (S1).

Description

Off-line type, current mode PWM power control circuit

Technical field

The utility model relates to switching power source control circuit, mainly is meant a kind of off-line type, current mode PWM power control circuit.

Background technology

Along with the continuous development of electronic technology, current mode PWM power-supply controller of electric has entered into the every field of science and technology, and pattern is constantly brought forth new ideas, and the utilization scope heals and becomes extensively, is bringing into play its irreplaceable effect.Applying to the off-line type switching power source chip of AC/DC change-over circuit at present, the most representative have following several: VIPer22 (ST ST Microelectronics product), Top246yn (POWER company product).

The basic principle of Switching Power Supply is as follows:

The operating frequency of holding circuit does not change, when load changed, the reference voltage of the current signal of feedback (flowing through power switch pipe), voltage signal and inside compared, and produces the PWM modulation signal, adjust the pulsewidth of power controlling switching tube signal, make the output voltage of Switching Power Supply constant.

Wherein shown in the realization principle accompanying drawing 1 of VIPer22 (ST ST Microelectronics product):

There is following shortcoming in VIPer22 in Switching Power Supply:

1) adopt the encapsulation of twin-core sheet, chip comprises control chip and high-voltage switch gear chip.

2) control chip adopts the BiCMOS technology, complex process, and domestic being difficult to produces.

3) the high-voltage switch gear chip adopts the power MOS pipe of withstand voltage 700V, and cost is higher.

When 4) short circuit was protected, operating time and self-starting time ratio were 10: 1, cause short-circuit dissipation very big.

Wherein shown in the realization principle accompanying drawing 2 of Top246yn (POWER company product):

There is following shortcoming in Top246yn in Switching Power Supply:

1) adopt the withstand voltage Bicmos technology that reaches 700V, area is big, and complex process domesticly still can't be produced, and cost is higher.

When 2) short circuit was protected, operating time and self-starting time ratio were bigger, cause short-circuit dissipation also bigger.

Summary of the invention

The purpose of this utility model provides a kind of off-line type, current mode PWM power control circuit, by increase delay circuit in circuit, has overcome the deficiency that existing switching power source control circuit exists.

The realization the technical solution of the utility model is: sort circuit comprises voltage detecting circuit U1, oscillating circuit U4, under-voltage protecting circuit U3, error amplifier U7, PWM comparator U8, injectron M1, M2, PWM logical circuit U5, driving gate U6; its primary structure is that described circuit also comprises delay circuit U2, and this U2 is connected across between U1 and the switch S 1.

This technical scheme also comprises:

The power vd D of described circuit is through voltage-stabiliser tube D1,1 fen two-way of resistance R, and one the tunnel connects switch S 1 through U1, and wherein U1 meets high pressure port VIN through U2, S1, resistance R 4; Another road meets VIN through U7, U8, U5, U6, M1, M2; Wherein U5 meets U4 respectively and meets VIN through U3.

Described delay circuit comprises chip built-in or external vibration, constitutes timing circuit by multistage trigger.

Described delay circuit comprises the timing circuit that chip built-in or external vibration constitute.

Described delay circuit comprises the capacitor charge and discharge circuit that electric capacity, resistance are formed.

The beneficial effect that the utlity model has: by delay circuit is set, guarantees on the MOS technology of simplifying, to realize reliable short-circuit protection, and reduce power consumption, have rational in infrastructure, technology is simple, cost is low, characteristics such as low in energy consumption.

Description of drawings

Fig. 1 is the schematic diagram of the off-line type switching power circuit (VIPer22) of the AC/DC change-over circuit produced of disclosed ST ST Microelectronics.

Fig. 2 is the schematic diagram of the off-line type switching power circuit (Top246yn) of the AC/DC change-over circuit produced of disclosed POWER company.

Fig. 3 is off-line type of the present utility model, current mode PWM power control circuit schematic diagram.

Fig. 4 is the PWM modulation waveform figure of Fig. 3.

Fig. 5 is the delay circuit schematic diagram of Fig. 3.

Fig. 6 is the flip-flop circuit schematic diagram of Fig. 5.

Embodiment

Below in conjunction with accompanying drawing the utility model is described further:

As shown in the figure, this circuit is to have increased delay circuit on the traditional circuit basis, and its operation principle is: in the electrifying startup stage, VDD is in zero potential, and VIN charges to VDD by R4, S1; After voltage detecting circuit U1 detects VDD and reaches starting resistor, oscillating circuit U4 work, oneself work of delay circuit U2, through after the constant time lag, circuit begins operate as normal, closes S1 simultaneously.VDD is owing to current drain, and voltage descends, and when dropping to the starter gate valve threshold voltage, chip has entered the PWM mode of operation.This moment, circuit sampling flow through the M1 electric current of switching power tube and the voltage signal (being sent to VDD) of optocoupler feedback, deliver to the reference voltage of error amplifier U7, PWM comparator U8 and reference circuit U1 generation, the sawtooth signal comparison that oscillating circuit U4 produces then, form the PWM modulation signal, drive the pulse duty factor of high-voltage switch gear power tube M2 control signal at last.Pwm signal is used for controlling external transformer, and at the secondary output end of the transformer that adopts this new structure, the galvanic current that needing to obtain is pressed.PWM modulated waveform figure as shown in Figure 4.

Added the time-delay short-circuit protection circuit that powers in the circuit, with the low-power consumption that guarantees to realize that short circuit is had the hiccups and protected.

The PWM modulation circuit comprises error amplifier U7, PWM comparator U8.

The injectron that adopts is outside NPN power tube.

Adopting the delay circuit structure to reduce short-circuit dissipation is a kind of method, and the concrete time or the concrete form of time-delay can have multiple variation.

The concrete form of delay circuit can have following several:

A) utilize chip built-in (or external) vibration, constitute timing circuit by multistage trigger, and the delay circuit that is used for carrying out accurate timing.

B) timing circuit that utilizes chip built-in (or external) vibration to constitute is judged the delay circuit that obtains accurate timing by reading between timing.

C) by electric capacity, resistance, utilize discharging and recharging the time of electric capacity, and the delay circuit that obtains.

Delay circuit can be obtained by following method: built-in chip type (external) oscillator, and internal needle carries out timing to frequency of oscillation, and available 16 timing circuits produce the signal that time-delay finishes when counting overflows.As internal oscillator frequency 65536Hz, after the time-delay of 16 powers, it just in time is 1 second through 2; After 1 second, counting overflows, and utilizes spill over to be fixed time-delay.

In the specific implementation, can adopt multiple different circuit mode, the following stated be a kind of preferred plan when the complexity of considering design and cost minimization.

1. voltage detecting circuit (reference circuit) U1 is a band-gap reference, and the reference voltage of starting resistor, cut-ff voltage etc. is provided.

2. oscillating circuit U4 provides PWM the reference frequency and the triangular wave of modulation for entire circuit.

3. voltage detecting circuit U1 is made of hysteresis loop comparator, by comparing with reference voltage, determines that the chip place starts or normal operating conditions.

4.S1 judgement is opened or is closed according to the U1 operating state.

5. the ratio of Fan Kui voltage, electric current and benchmark after error amplifier U7 amplification, is sent into PWM comparator U8.

6.PWM logic U5 according to the output of frequency of oscillation, error amplifier, produces certain frequency, duty ratio is with the modulation signal of load variations.

7. the injectron that adopts of the utility model is the NPN power tube, accepts modulation signal and the switch motion that produces big electric current.

Claims

1. an off-line type, current mode PWM power control circuit; comprise voltage detecting circuit (U1), oscillating circuit (U4), under-voltage protecting circuit (U3), error amplifier (U7), PWM comparator (U8), injectron (M1, M2), PWM logical circuit (U5), driving gate (U6); it is characterized in that described circuit also comprises delay circuit (U2), should (U2) be connected across between (U1) and the switch (S1).

2. off-line type as claimed in claim 1, current mode PWM power control circuit, the power supply (VDD) that it is characterized in that described circuit divides two-way through voltage-stabiliser tube (D1), resistance (R1), one road warp (U1) connects switch (S1), and wherein (U1) connects high pressure port (VIN) through (U2), (S1), resistance (R4); Another road meets (VIN) through (U7), (U8), (U5), (U6), (M1), (M2); Wherein (U5) meets (U4) respectively and meets (VIN) through (U3).

3. off-line type as claimed in claim 1 or 2, current mode PWM power control circuit is characterized in that described delay circuit comprises chip built-in or external vibration, by the timing circuit of multistage trigger formation.

4. off-line type as claimed in claim 1 or 2, current mode PWM power control circuit is characterized in that described delay circuit comprises the timing circuit that chip built-in or external vibration constitute.

5. off-line type as claimed in claim 1 or 2, current mode PWM power control circuit is characterized in that described delay circuit comprises the capacitor charge and discharge delay circuit that electric capacity, resistance are formed.