a u2018 charge phase u2019 there now follows a brief description of the discharge and charge phases of operation of the drive circuit 6 a to initiate the discharge phase the discharge switch q 2 is closed and the charge switch q 1 remains open as described in more detail in applicant 39 s co pending application ep 06254039 8 under the control of the microprocessor 26 and the current sensing and control means 42 the discharge switch q 2 is rapidly pulsed on and off to regulate the flow of current an injector 34 or 36 fig1 is selected for injection by closing the associated injector select switch qs 1 or qs 2 respectively for example to inject from the first injector 34 the first injector select switch qs 1 is closed and current flows from the positive terminal of the second capacitor c 2 through the current sensing and control means 42 through the terminals of the selected first injector 34 from the low side u2212 to the high side through the inductor l through the discharge switch q 2 and back to the negative side of the second capacitor c 2 no current is able to flow through the unselected second injector 36 because the associated injector select switch qs 2 remains open to charge the injectors 34 36 during the charge phase the charge switch q 1 is closed and the discharge switch q 2 remains open also as described in ep 06254039 8 under the control of the microprocessor 26 and the current sensing and control means 42 the charge switch q 1.