CN1877959A - High-frequency constant current charger - Google Patents

Abstract

The invention discloses a high-frequency constant-current charging device, which comprises the following parts: high-frequency transformer in connection with contravariant circuit output of full-bridge contravariant circuit with energy-saving capacitance of DC power and contravariant switch group, high-bridge high-pressure commutating circuit and load capacitance, wherein a resonant circuit is concatenated between one end of contravariant circuit output and one end of high-frequency transformer. The charging device possesses certain constant-current output ability and anti-load short-circuits ability, which improves charging efficiency and anti-electromagnetic ability.

Description

A kind of high-frequency constant current charger

Technical field

The present invention relates to charge power supply, specifically relate to a kind of high-frequency constant current charger.

Background technology

At present, high voltage pulse modulator is widely used in fields such as X-ray machine and container examination system.There is multiple circuit form available in high voltage pulse modulator front end circuit charge power supply, traditional have capacitance-resistance type (RC), mode of resonance (LCD), a flyback charging type (inverse-excitation type inverter), in the flyback charging type, the general capacitor that adopts is as elementary accumulation power supply, pass through inverter control circuit, boost through transformer, high-voltage rectifying is as the charge power supply of output capacitor.

Along with the development of power electronic, various high-frequency inversion technology are maked rapid progress, and inverting commonly used has three kinds, pulse-width modulation (PWM), frequency modulation(FM) (FM) and phase modulated (PM) etc., and operating frequency can reach tens KHZ, even higher.As the charge power supply of high voltage pulse modulator, should have the impact capacity of certain opposing load short circuits, just should have constant-current characteristics, because load is a capacitor,, open moment at electric current because the voltage of capacitor can not suddenly change, capacitor is equivalent to short circuit.The output regulatory function that also should possess stronger anti-electromagnetic interference capability and wide region simultaneously, and higher charge efficiency.

Satisfy above-mentioned requirements, all there is weak point in present several modulation system, because these several modes all require in charging process the operating state of inverse switch pipe constantly to be adjusted, the process of adjustment may cause adverse effect to stability, the reliability of power supply.Wherein, the pulse-width modulation conversion efficiency is low, and the inverse switch pipe is operated in the hard switching state, causes the electromagnetic interference of circuit also bigger, and it is unreliable to work.

Summary of the invention

Technical problem to be solved by this invention provides the constant current charger of a kind of high frequency series resonance, switching circuit form.

For solving the problems of the technologies described above, technical scheme of the present invention is a kind of high-frequency constant current charger, the full bridge inverter of forming by the storage capacitor in parallel, inverse switch pipe and be connected in the high frequency transformer of this inverter circuit output with DC power supply, full-bridge high-voltage rectifier, load capacitance is characterized in that: be connected in series a resonant circuit between an end of described inverter circuit output and the end that high frequency transformer is imported.Inverter circuit itself has certain frequency-selecting function and internal resistance, by setting the harmonic period of resonant circuit, adopts fixed pulse width, fixing switching frequency, and the switching tube in the control inverter circuit turn-offs when being implemented in zero current.

A kind of high-frequency constant current charger, described resonant circuit is made of inductance coil and capacitor series.

High-frequency constant current charger, the resonance frequency of described resonant circuit $f_0=1{/}_{\mathrm{\Π}}\sqrt{\mathrm{LrCr}}.$

A kind of high-frequency constant current charger, described inverse switch pipe are igbt (IGBT).

A kind of high-frequency constant current charger is characterized in that: the iron core of described high frequency transformer adopts amorphous material to make Crossed Circle.Can reduce the volume of transformer, reduce the wastage.

A kind of high-frequency constant current charger adopts said structure, is connected in series a resonance frequency to be between an end of inverter circuit output and a end that high frequency transformer is imported $f_0=1/2_{\mathrm{\Π}}\sqrt{\mathrm{LrCr}}$ Resonant circuit.Inverter circuit itself has certain frequency-selecting function and internal resistance, by setting the harmonic period of resonant circuit, adopt fixed pulse width, fixing switching frequency, inverse switch pipe in the control inverter circuit, turn-off when being implemented in zero current, thereby make this charging device have the ability of certain constant current fan-out capability and opposing load short circuits, and improved charge efficiency and anti-electromagnetic interference capability.

Description of drawings

The present invention is further detailed explanation below in conjunction with the drawings and specific embodiments;

Fig. 1 is a kind of high-frequency constant current charger circuit theory diagrams of the present invention;

Fig. 2 is an inverse switch pipe start pulse signal schematic diagram shown in Figure 1;

Fig. 3 is load capacitance output characteristic curve figure shown in Figure 1;

In Fig. 1,1, DC power supply; 2, storage capacitor; , Z1, Z2, Z3, Z4, inverse switch pipe; 4, resonant circuit; 5, inductance coil; 6, capacitor; 7, high frequency transformer; 8, high-voltage rectifier; 9, load capacitance.

Embodiment

As shown in Figure 1 and Figure 2, a kind of high-frequency constant current charger, full bridge inverter of forming by storage capacitor 2, inverse switch pipe Z1, Z2, Z3, the Z4 in parallel and the high frequency transformer 7 that is connected in this inverter circuit output with DC power supply 1, the output of high frequency transformer 8 connects the input of full-bridge high-voltage rectifier 8, and the output of high-voltage rectifier 8 also connects load capacitance 9.Being connected in series one between one end of described inverter circuit output and the end of high frequency transformer 8 inputs is connected in series by inductance coil 5 and capacitor 6 and constitutes resonant circuit 4.In the power inverter process, by start pulse signal T1, T2, two groups of inverse switch pipe Z1, Z4 and Z2, Z3 alternate conduction are finished a switch periods.Owing to be in resonance frequency of inverter circuit output serial connection $f_0=1/2_{\mathrm{\&Pi;}}\sqrt{\mathrm{<figure-callout\; id="5"\; label="LrCr\; Inductance\; coil"\; filenames="A20051004048600071.png"\; state="\{\{state\}\}">LrCr</figure-callout>}}$ Inductance coil 5 and capacitor 6, make the loop have certain frequency-selecting function and internal resistance, when the switching frequency F of inverter circuit less than resonance frequency f ₀One half, the form of this topological structure have certain constant current fan-out capability.The ability that has also possessed simultaneously the opposing load short circuits.

The series-resonant inverting circuit, if the average current in loop is about 45A, peak current is about 130A, therefore can select average current is the inverse switch pipe (igbt) of 200A band fly-wheel diode.Determine that according to the switching characteristic of inverse switch pipe (IGBT) switching frequency is 19KHz, then resonance frequency is f ₀Be decided to be 40Hz, thereby can calculate the value of the Cr of the Lr of inductance coil 5 and capacitor 6.

The precision of charging is least unit by the work period of control charge power supply with a Δ V, and for guaranteeing Zero Current Switch, just half period is a step Δ V, and the absolute error of the minimum voltage stabilizing of power supply output that Here it is can approximate calculation be:

ΔV/V＝F/2fs

F is that charge power supply operating frequency fs is the switching frequency of series resonant tank

Be set at 19KHz as switching frequency with series resonant tank.The frequency that connects inverse switch pipe base stage start pulse signal T1, T2 is 19KHz, controls two groups of inverse switch pipe Z1, Z4 and Z2, Z3 alternate conduction, finishes a switch periods.The precision of this charge power supply can reach

Δ V/V=20/ (2 * 19 * 10 ³)=0.53 * 10 ^-3As seen can satisfy the requirement of charging voltage precision fully, charging voltage can be by sampling feedback to control loop.

This charge power supply, the current waveform of exporting through inverter circuit is sinusoidal wave, harmonic content is few.The di/dt of entire circuit is smaller, and electromagnetic interference is also little, has improved the reliability of whole system.Referring to Fig. 3, because charge power supply can reach constant current output, the voltage that is recharged on the load container 9 is linear the rising, and power supply is made half period, and output voltage just rises to certain numerical value.

Claims (5)

1, a kind of high-frequency constant current charger, by the storage capacitor (2) in parallel, inverse switch pipe (Z1, Z2, Z3, Z4) full bridge inverter of forming and the high frequency transformer (7) that is connected in this inverter circuit output with DC power supply (1), full-bridge high-voltage rectifier (8), load capacitance (9) is characterized in that: be connected in series a resonant circuit (4) between an end of described inverter circuit output and the end that high frequency transformer (7) is imported.

2, a kind of high-frequency constant current charger according to claim 1 is characterized in that: described resonant circuit (4) is made of inductance coil (5) and capacitor (6) serial connection.

3, a kind of high-frequency constant current charger according to claim 2 is characterized in that: the resonance frequency of described resonant circuit (4) $f_0=1/2\mathrm{\&Pi;}\sqrt{\mathrm{LrCr}}.$

4, a kind of high-frequency constant current charger according to claim 1 is characterized in that: described inverse switch pipe (Z1, Z2, Z3, Z4) is an igbt.

5, a kind of high-frequency constant current charger according to claim 1 is characterized in that: the iron core of described high frequency transformer (7) adopts amorphous material to make Crossed Circle.

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