Abstract: Introduced one kind through the electromagnetic coupling non-contact charging circuit. Has related in detail electric circuit’s basic structure and the control policy, has analyzed the question which in the electric circuit possibly exists and has given the solution. Finally has confirmed this design through the experiment.
Key word: Non-contact charge; Transformer; Magnetic amplifier
Introduction
The scientist promulgates the electromagnetic induction and the available wire transmission electrical energy since 1840 until now, the electrical energy transmission was mainly carries on by the wire immediate contact. The electrician equipment’s charge is generally carries on through the plug and socket, but when carries on the high efficiency charge, this charge way has the danger which the high pressure receives an electric shock, has brought the unsafe factor for people’s production and the life, therefore, realizes between the power supply system and the electrical equipment does not have the conductor contact, becomes one of naturally electrical energy transmission important research directions. The new non-contact energy transfer technology used the transformer to carry on the energy transfer not to affect the speed this merit, and separated the traditional transformer’s induction coupling magnetic circuit, initially, the secondary circled separately in the different magnetic structure, thus realized between the power source and the load unit does not need the physical connection the energy coupling.
This charging circuit has used the switching power supply technology and the new non-contact energy transfer technology, under the power frequency 220V input, obtains the stable direct-current 12V output to use to the battery charging.
1 main circuit structure
Main circuit as shown in Figure 1, power frequency 220V input after the entire bridge rectification, first through conventional half bridge inversion electric circuit, then through non-contact insulating transformer isolation input level and output stage. The output stage uses the full-wave rectification, and through the LC filter filtration high frequency ripple, the final output directs current the 12V voltage. Half bridge electric circuit uses switching valve S1 and S2 are high frequency MOS manage IRF840, to solve high frequency switching power supply common questions and so on switching loss and noise, in the electric circuit has used the series resonance analysis situs, using switching valve outside and electric capacity C3 and C4, series inductance Lr and transformer’s leakage inductance resonance, winds through the high frequency MOS tube’s electric current is a sine wave like this, uses clears the MOS tube in the sine wave zero crossing time, has realized the zero potential soft switch technology, reduced the switching loss greatly. Simultaneously winds through counter-and diode’s sinusoidal current causes on diode’s electric current rate of change becomes very small, reduced restored the time reverse, was advantageous in the MOS tube’s clear and the shutdown.
Figure 2
2 control principles and structure
This electric circuit’s control structure drawing as shown in Figure 2, what the control chip uses is accurate resonant converter controller UC3861, has two groups widths by it to be fixed, the frequency invariable square-wave pulse, actuates chip IR2110 through the special-purpose MOS tube to actuate S1 and S2 again.
Figure 2 UC3861 and the IR2110 power supply provides by insulating transformer’s auxiliary winding (see Figure 1), is connected with Vcc. UC3861 belongs to the frequency modulation to control the chip, the frequency shift scope the pressure which by foot Range, Rmin and Cvco is composed controls the oscillator determination. When the erroneous amplifier’s output increases, the frequency also increases, vice versa. UC3861 can realize the zero potential switch technology, joins the resonance current which in the Zero end the current transformer examines (to see Figure 1), when the electric current zero hour, the chip will have cleared the output signal, clears the MOS tube, realizes the zero potential clear. When the zero potential switch resonance converter, the turn-on frequency elevates, the converter output voltage will reduce. Therefore, the erroneous amplifier’s opposition input end joins the voltage reference, the synchronism input end joins the feedback voltage. Because the input level and the output stage are the non-contact, therefore the feedback voltage cannot directly from out-port turning on, but (output voltage after auxiliary transformer live pressure) adds to directly the auxiliary power line voltage the synchronism input end, achieves the closed-loop control.
3 magnetic amplifiers use in the secondary constant voltage
To the charging circuit, the output voltage stable especially important, but has the isolation primary and the secondary unit non-contact system’s design, means that the secondary current cannot carry on the control directly, this electric circuit joins the magnetic amplifier in the out-port to use in the constant voltage.
The magnetic amplifier mainly makes by the crystalless alloy, its hysteresis loop is quite narrow, has not been saturated when inductance compared to saturation time inductance at least tenth magnitude. Its principle of work as shown in Figure 3, when the controlling current is very small, magnetic amplifier not saturated, its inductance may regard as the infinity, the electric circuit is equal to the abruption, the electric current is unable to pass. Along with controlling current’s enlargement, the magnetic amplifier tends to be saturated, the inductance quantity may regard as zero, the electric circuit is equal to the short circuit. Therefore the magnetic amplifier uses in time the constant voltage, may regard as a magnetic PWM switch.
The magnetic amplifier uses in the secondary constant voltage electric circuit as shown in Figure 4, in the chart MA1 and MA2 are magnetic amplifiers, it with the rectification second-level tube series, is advantageous in eliminates the noise which in the diode reverse recovery procedure the electric current change excessively quickly produces.
4 experimental results
In view of the above analysis, has designed an output is about the 20W non-contact charging circuit, the parameter is as follows: Resonant inductance Lr=5.48mH, resonant electric capacity C3=C4=680pF, the transformer uses the E magnetic core E55yi rightly, the original vice-side winding circles separately in skeleton’s both sides, adds the 1mm air gap, the leakage inductance is 0.105mH. Experimental result as shown in Figure 5.
(a) slaving voltage profile and switching valve vDS profile
(b) the switching valve vDS profile and directs current the 12V output wave shape
May see from Figure 5, on the switching valve realized the zero potential clear, the switching loss has been very small, and direct-current output 12V was stable.
5 conclusions
This article analyzed has realized the non-contact charge system’s significance, and has carried on the analysis to the non-contact charge system’s main circuit and the control circuit, proposed one kind used in the magnetic amplifier the secondary constant voltage the electric circuit analysis situs, both has stabilized the direct-current output, and improved system’s dynamic property. Finally through the experimental verification above design.
