The designers use the cocurrent electronic load to test the power source, like solar energy array or battery, but the commercial cocurrent electronic load is very expensive. So long as you use power MOSFET in its linear area, may manufacture own cocurrent electronic load (Figure 1). This load uses two simple feedback loops. MOSFET serves as under a stationary stream pattern under the current supply or the constant voltage pattern potential source. Designer when description potential source characteristic uses the stationary stream pattern, because under the stationary stream pattern, the power source must provide the magnitude of current which in the electronic load establishes. The designers use together the constant voltage pattern and the current supply, because the constant voltage pattern will force the power source to work under the load hypothesis voltage.
Under the electric current pattern, RSHUNT examines ILOAD, the voltage feedback which the examination obtains gives operational amplifier IC1The opposition input end. Because operational amplifier’s zero-frequency gain is very high in the linear feedback work area, the opposition input end maintains with the non-opposition input end is equal, namely is equal to VIREF. The amplifier has own value of exports, causes MOSFET Q2 and the Q3 work in the linear area, will thus consume power source’s power. The source magnitude of current and electric current link datum VIREF is proportional, namely ILOAD=VIREF/RSHUNT. May use one to connect in the regulated voltage datum the resistance voltage divider to establish VIREF, or the use switch outputs from one based on PC I/O the card D/A, realizes the nimble disposition.
The voltage working pattern’s situation and the electric current pattern are the same, just examines the variable is the output voltage, this output voltage is undergoes the voltage divider RA/RB weaken, therefore electronic load’s work ratio-voltage transports the electric discharge source voltage to be high. Examines the voltage feeds back to the IC1B non-opposition input end, MOSFET works once more in the linear area. Load voltage VLOAD=VVREF×(RA RB)/RB.
CA3240 double transports puts IC1 to be possible, in the input voltage is lower than the negative supply voltage in the situation to work, this is useful to the single power source power supply, however, if you have the symmetrical power source, that may use any transports puts. Relay K1 actuates Q1 through one digital pilot wire to cut the working pattern. MOSFET is very important; You may increase this parallel use the IRF150 component, sharpens the electric current bearing capacity, because IRF150 has the temperature coefficient, thus may wind through two parallel MOSFET balanced the electric currents. Because in the electric circuit uses two MOSFET, the electronic load may withstand the 10A electric current, the power loss is bigger than 100W, therefore uses a radiator and the small fan is a great idea.
This electric circuit is suitable in the description has two kind of power source pattern light to bend down the battery module characteristic. When uses this electric circuit and based on the PC establishment, Helios technology company (www.heliostechnology.com) light bends down the battery module I-V characteristic curve to indicate that has an area in VMPP (peak voltage) above, under VMPP this voltage, the steep transition corresponds (Figure with a potential source 2). In is lower than VMPP under the voltage, the light bends down the battery module just likes a current supply. In the ordinary circumstances, describes the I-V characteristic curve this smooth area characteristic with a simple electric current pattern electronic load is very difficult, is very sensitive because of the voltage output to the electric current small change, therefore, the constant voltage pattern load is one kind of good choice.
