Capacitor Charge-Energy Transfer Description

Capacitor Charge Control

The Capacitor Charge Control circuit controls the Energy Storage Capacitor Charger. It achieves and maintains a selected voltage on the energy storage capacitor and reports the capacitor voltage status to the System microprocessor. The main circuit components consist of op amp U 1713 and comparators U8A, U8B, and U8C. Op amp U17B sets and maintains the selected voltage to the energy storage capacitor by controlling an inhibit signal to pin 2 of U2A. When a selected voltage is achieved, U17B shuts down U2A which disables the Energy Storage Capacitor Charger. To set the gain for a particular charge voltage, digital-to-analog (D/A) converter U18 is connected between the inverting input and the output of U17B. The output of the D/A converter is controlled by selection of a 12-hit word by the System microprocessor. Resistors R2 and R4 function as voltage dividers for the energy storage capacitor output voltage. When this divided voltage is applied to the noninverting input of U17B, the gain of U 17B rises accordingly. Comparator U8C provides switching for the Energy Storage Capacitor Charger in response to input from U17B. When the output of U 17I3 rises above +2.5V, U8C switches low. This low inhibit signal switches the output of U2A high, shutting down the Energy Storage Capacitor Charger. Comparators evaluate the charge stored on the energy storage capacitor with respect to the defibrillation energy selected. U8B detects values greater than the minimum required for in-tolerance energy; U8A detects values less than the maximum allowed for the same energy setting. The outputs from U8A and U8B form the CHARGE VALID signal, indicating valid energy charge levels. This signal informs the System microprocessor about the status of the selected charge energy.

Energy Transfer

The Energy Transfer circuit transfers the energy stored in the energy storage capacitor out through the paddles. The main circuit components are U6, Q4, C9, and CR4. When the sternum and apex pushbuttons on the paddles are pressed, the Sternum Transfer and Apex Transfer lines at J17 produce the Transfer Request signal front the output of U15A which is sent to the System microprocessor. If all energy transfer parameters are correct, the System microprocessor returns a Transfer Enable signal through U 11 A and U 14C.

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